Dual-mode oscillator and multi-phase oscillator
阅读说明：本技术 双模振荡器及多相位振荡器 (Dual-mode oscillator and multi-phase oscillator ) 是由 舒一洋 钱慧珍 罗讯 于 2016-11-04 设计创作，主要内容包括：本申请实施例公开了一种双模振荡器及多相位振荡器。该双模振荡器通过模式切换电路实现两个工作模式之间的切换,可以得到两个不同频段的振荡信号,同时,其采用两个变压器耦合振荡器构成双模振荡器,每个变压器耦合振荡器中的升压变压器将第一MOS管的漏极电压摆幅进行倍增后再注入第二MOS管的栅极,从而在不增大振荡器的供电电压的情况下获得更大的栅极电压摆幅,提高双模振荡器的相位噪声性能。该多相位振荡器,由多个双模变压器耦合振荡器通过多相位耦合电路连接成莫比乌斯环,不仅可以产生多相位振荡信号,还可以提高整个振荡器的相位噪声性能。(The embodiment of the application discloses a dual-mode oscillator and a multi-phase oscillator. The dual-mode oscillator realizes the switching between two working modes through the mode switching circuit, can obtain oscillation signals of two different frequency bands, simultaneously adopts two transformer coupled oscillators to form the dual-mode oscillator, and a boosting transformer in each transformer coupled oscillator multiplies the voltage swing of a drain electrode of a first MOS tube and then injects the multiplied voltage swing into a grid electrode of a second MOS tube, so that a larger grid electrode voltage swing is obtained under the condition of not increasing the power supply voltage of the oscillator, and the phase noise performance of the dual-mode oscillator is improved. According to the multi-phase oscillator, a plurality of dual-mode transformer coupled oscillators are connected into a Mobius ring through a multi-phase coupling circuit, so that not only can multi-phase oscillation signals be generated, but also the phase noise performance of the whole oscillator can be improved.)
1. A dual mode oscillator comprising two transformer coupled oscillators and a mode switching circuit.
2. The dual-mode oscillator of claim 1, wherein either of the two transformer-coupled oscillators includes a differential metal-oxide-semiconductor (MOS) transistor pair, a primary capacitance (Cp), a secondary capacitance (Cs), and a step-up transformer;
the source electrode of the first MOS transistor in the differential MOS transistor pair is connected with the source electrode of the second MOS transistor in the differential MOS transistor pair and is coupled to a constant voltage node;
the drain electrode of the first MOS tube is respectively connected with one end of the primary capacitor Cp and the first input end of the step-up transformer, and the drain electrode of the second MOS tube is respectively connected with the other end of the primary capacitor Cp and the second input end of the step-up transformer;
the grid electrode of the first MOS tube is respectively connected with one end of the secondary capacitor Cs and the second output end of the boosting transformer, and the grid electrode of the second MOS tube is respectively connected with the other end of the secondary capacitor Cs and the first output end of the boosting transformer; the first input end and the first output end are homonymous ends;
the mode switching circuit is positioned between the two transformer coupled oscillators, is respectively connected with two drains in each transformer coupled oscillator, and is used for changing the oscillation frequency range output by the dual-mode oscillator through switching.
3. The dual-mode oscillator of claim 2, wherein the first MOS transistor and the second MOS transistor are NMOS transistors; the source electrode of the first NMOS tube and the source electrode of the second NMOS tube are connected and coupled to the constant voltage node; the constant voltage node is directly grounded, or the constant voltage node is grounded through a tail current source.
4. The dual-mode oscillator of claim 3, wherein a primary inductance Lp of the step-up transformer is center-tapped from a power supply VDDA secondary inductor Ls of the step-up transformer is connected with a bias voltage V at a center tapgate。
5. The dual-mode oscillator of claim 2, wherein the first MOS transistor and the second MOS transistor are both PMOS transistors; the source electrode of the first PMOS tube and the source electrode of the second PMOS tube are connected and coupled to the constant voltage node; the constant voltage node is directly connected to a power supply VDDOr, the constant voltage node is connected to the power supply V through a tail current sourceDD。
6. The dual-mode oscillator of claim 5, wherein a center tap of the primary inductor Lp of the step-up transformer is coupled to ground, and a center tap of the secondary inductor Ls of the step-up transformer is coupled to a bias voltage Vgate。
7. The dual-mode oscillator of any one of claims 2-6, wherein at least one of the primary capacitance Cp and the secondary capacitance Cs, including at least one of a switched capacitor array or a varactor diode, is capable of being adjusted by an adjustment signal to adjust a capacitance value.
8. The dual-mode oscillator of any of claims 2-6, wherein the mode switching circuit comprises: control circuit and at least two mode capacitors C coupled to the control circuitmode；
The control circuit is used for switching the dual-mode oscillator between an odd mode and an even mode under the action of a mode control signal; wherein the content of the first and second substances,
in the even mode, the mode capacitance CmodeEquivalently bypassed, the oscillation frequency range being a first oscillation frequency range;
in the odd mode, the mode capacitance CmodeEquivalently, the frequency range is bridged between two drains of any transformer coupled oscillator, and the oscillation frequency range is a second oscillation frequency range which is different from the first oscillation frequency range.
9. The dual-mode oscillator of claim 8, wherein the control circuit comprises: a first odd mode switch and a second odd mode switch, and a first even mode switch and a second even mode switch;
the first even mode switch and the second even mode switch are respectively connected with at least one mode capacitor in parallel;
two ends of the first even mode switch are respectively connected to the drains of the first MOS tubes of the two transformer coupled oscillators, and two ends of the second even mode switch are respectively connected to the drains of the second MOS tubes of the two transformer coupled oscillators;
two ends of the first odd-mode switch are respectively connected with the drain electrode of a first MOS tube of one transformer coupled oscillator and the drain electrode of a second MOS tube of the other transformer coupled oscillator, and two ends of the second odd-mode switch are respectively connected with the drain electrode of the second MOS tube of the one transformer coupled oscillator and the drain electrode of the first MOS tube of the other transformer coupled oscillator;
wherein, in the odd mode, the first odd mode switch and the second odd mode switch are turned on, and the first even mode switch and the second even mode switch are turned off; in the even mode, the first odd mode switch and the second odd mode switch are switched off, and the first even mode switch and the second even mode switch are switched on.
10. The dual-mode oscillator of claim 8, wherein the second oscillation frequency range is lower than the first oscillation frequency range.
11. The dual-mode oscillator of any of claims 2-6, wherein the boost transformer has a boost multiple of k (k > 1) and the voltage across the secondary capacitor Cs is k times the voltage across the primary capacitor Cp.
12. A multi-phase oscillator, comprising: n dual-mode oscillators as claimed in any of claims 2 to 11, and N multi-phase coupling circuits; n is an integer greater than 1;
each multi-phase coupling circuit is coupled between two dual-mode oscillators; the N dual-mode oscillators form Mobius annular connection through the N multi-phase coupling circuits.
13. The multi-phase oscillator of claim 12, wherein the N dual-mode oscillators and the N multi-phase coupling circuits form N stages, each stage comprising a dual-mode oscillator and a multi-phase coupling circuit; the first coupling end of each stage of multiphase coupling circuit is connected to two drain electrodes of any transformer coupled oscillator in the stage of dual-mode oscillator, and the second coupling end of each stage of multiphase coupling circuit is connected to two drain electrodes of any transformer coupled oscillator in the next stage of dual-mode oscillator.
14. The multi-phase oscillator of claim 12, wherein the N dual-mode oscillators and the N multi-phase coupling circuits form N stages, each stage comprising a dual-mode oscillator and a multi-phase coupling circuit; the first coupling end of each stage of multiphase coupling circuit is connected to two grids of any transformer coupled oscillator in the stage of dual-mode oscillator, and the second coupling end of each stage of multiphase coupling circuit is connected to two grids of any transformer coupled oscillator in the next stage of dual-mode oscillator.
15. The multi-phase oscillator of claim 13 or 14, wherein the multi-phase coupling circuit comprises: coupling the MOS tube pair;
the source electrode of the first coupling MOS tube in the coupling MOS tube pair is connected with the source electrode of the second coupling MOS tube, and is directly grounded or grounded through a current source;
the drain electrode of the first coupling MOS tube and the drain electrode of the second coupling MOS tube are used as the first coupling end and are connected with two drain electrodes or two grid electrodes of any transformer coupling oscillator in the stage of dual-mode oscillator;
and the grid electrode of the first coupling MOS tube and the grid electrode of the second coupling MOS tube are used as the second coupling end and are connected with two drain electrodes or two grid electrodes of any transformer coupling oscillator in the next-stage dual-mode oscillator.
16. The multi-phase oscillator of claim 13 or 14, wherein the multi-phase coupling circuit comprises: a coupling MOS tube pair, a coupling capacitor pair, a coupling inductor pair, or a coupling microstrip line.
Technical Field
The application relates to the technical field of oscillators, in particular to a dual-mode oscillator and a multi-phase oscillator based on the same.
Background
An oscillator (oscillator) is an energy conversion device that converts direct current electric energy into alternating current electric energy with a certain frequency, and is widely applied to various fields such as measurement, automatic control, wireless communication, remote control and the like. In wireless communication systems, oscillators (such as carrier oscillators of transmitters) are used primarily to generate multi-frequency oscillating signal outputs; the frequency range of the oscillating signal determines the operating bandwidth of the wireless communication system. As wireless communication systems have been developed, the wireless communication systems are required to have wider operating bandwidths, and oscillators used in the systems are required to output oscillation signals having as wide a frequency range as possible. The dual-mode oscillator can break through the frequency range limitation of the traditional oscillator (such as an LC oscillator), provide oscillation signals with wider frequency range, and is applied to more existing wireless communication systems.
As shown in fig. 1, a conventional dual-mode oscillator is generally configured by two LC oscillators each configured by a pair of transistors and an LC oscillation circuit and a mode switching circuit. The two sets of switches S1, S2, and S3, S4 in the mode switching circuit are alternately turned on, so that the two LC oscillators are in two different operation modes. When S1 and S2 are turned on and S3 and S4 are turned off, the two LC oscillators are in the same phase mode, and the frequency range of oscillation signals of the dual-mode oscillator is the same as that of a single LC oscillator; when S1 and S2 are turned off and S3 and S4 are turned on, the two LC oscillators are in anti-phase mode, and the frequency range of the oscillation signal is relatively low compared with that of the in-phase state. Because the dual-mode oscillator respectively generates two frequency ranges of a high frequency band and a low frequency band under two working modes, compared with the traditional oscillator, the dual-mode oscillator can provide oscillation signals of wider frequency ranges.
Although the conventional dual-mode oscillator can provide oscillation signal output in a wide frequency band, the phase noise performance of the conventional dual-mode oscillator is still poor, which is one of important factors limiting the performance of a communication system. Therefore, there is a need for a new oscillator that can provide a wide-band oscillation signal output while ensuring good phase noise performance.
Disclosure of Invention
The application provides a dual-mode oscillator and a multi-phase oscillator, which can ensure good phase noise performance while providing wide-band oscillation signal output.
In a first aspect, an embodiment of the present application provides a dual-mode oscillator, which includes two transformer-coupled oscillators and a mode switching circuit;
any transformer coupled oscillator comprises a differential Metal Oxide Semiconductor (MOS) transistor pair, a primary capacitor Cp, a secondary capacitor Cs and a step-up transformer;
the source electrode of the first MOS transistor in the differential MOS transistor pair is connected with the source electrode of the second MOS transistor in the differential MOS transistor pair and is coupled to a constant voltage node;
the drain electrode of the first MOS tube is respectively connected with one end of the primary capacitor Cp and the first input end of the step-up transformer, and the drain electrode of the second MOS tube is respectively connected with the other end of the primary capacitor Cp and the second input end of the step-up transformer;
the grid electrode of the first MOS tube is respectively connected with one end of the secondary capacitor Cs and the second output end of the boosting transformer, and the grid electrode of the second MOS tube is respectively connected with the other end of the secondary capacitor Cs and the first output end of the boosting transformer; the first input end and the first output end are homonymous ends;
the mode switching circuit is positioned between the two transformer coupled oscillators, is respectively connected with two drains in each transformer coupled oscillator, and is used for changing the oscillation frequency range output by the dual-mode oscillator through switching.
Optionally, the output end of the dual-mode oscillator is the two drains or the two gates in any transformer-coupled oscillator.
Because the dual-mode oscillator provided by the embodiment of the application realizes the switching between the two working modes through the mode switching circuit, the oscillation signals of two different frequency bands can be obtained, and the primary capacitor Cs and the secondary capacitor Cp in each transformer coupled oscillator and the capacitor C in the mode switching circuit can be adjustedmodeThe output of the oscillation signal in the wide frequency band is realized. In addition, the dual-mode oscillator is formed by adopting two transformer coupled oscillators, the drain electrode of the first MOS tube in each transformer coupled oscillator is connected to the grid electrode of the second MOS tube through the boosting transformer, namely the boosting transformer multiplies the voltage swing of the drain electrode of the first MOS tube and injects the multiplied voltage swing into the second MOS tubeThe grid electrode of the second MOS tube can obtain larger grid electrode voltage swing amplitude under the condition of not increasing the power supply voltage of the oscillator, and the phase noise performance of the dual-mode oscillator is improved; meanwhile, the dual-mode oscillator couples the two transformer coupled oscillators together through the mode switching circuit, and the phase noise performance can be improved.
In a possible implementation manner, the first MOS transistor and the second MOS transistor are both NMOS transistors; the source electrode of the first NMOS tube and the source electrode of the second NMOS tube are connected and coupled to the constant voltage node; the constant voltage node is directly grounded, or the constant voltage node is grounded through a tail current source.
In a possible implementation manner, the center tap of the primary inductor Lp of the boosting transformer is connected with a power supply VDDA secondary inductor Ls of the step-up transformer is connected with a bias voltage V at a center tapgate。
In a possible implementation manner, the first MOS transistor and the second MOS transistor are both PMOS transistors; the source electrode of the first PMOS tube and the source electrode of the second PMOS tube are connected and coupled to the constant voltage node; the constant voltage node is directly connected to a power supply VDDOr, the constant voltage node is connected to the power supply V through a tail current sourceDD。
In a possible implementation manner, a center tap of a primary inductor Lp of the boosting transformer is grounded, and a center tap of a secondary inductor Ls of the boosting transformer is connected with a bias voltage Vgate。
In one possible implementation, at least one of the primary capacitance Cp and the secondary capacitance Cs, including at least one of a switched capacitor array or a varactor diode, can be adjusted in capacitance value by an adjustment signal.
In this implementation manner, if the primary capacitor Cp and the secondary capacitor Cs both include the switched capacitor array and the varactor diode, the step adjustment of the capacitance values of the primary capacitor Cp and the secondary capacitor Cs can be implemented by changing the number of capacitors in the switched capacitor array that are turned on, so as to implement the step adjustment of the oscillation frequency of the transformer coupled oscillator; by adjusting the control voltage of the variable capacitance diode, the continuous fine adjustment of the capacitance values of the primary capacitor Cp and the secondary capacitor Cs can be realized, and further the continuous fine adjustment of the oscillation frequency of the transformer coupled oscillator can be realized.
In one possible implementation, the mode switching circuit includes: a control circuit and at least two mode capacitors Cmode coupled to the control circuit;
the control circuit is used for switching the dual-mode oscillator between an odd mode and an even mode under the action of a mode control signal; wherein the content of the first and second substances,
in the even mode, the mode capacitance Cmode is equivalently bypassed, and the oscillation frequency range is a first oscillation frequency range;
in the odd mode, the mode capacitor Cmode is equivalently bridged between two drains of any transformer coupled oscillator, and the oscillation frequency range is a second oscillation frequency range which is different from the first oscillation frequency range.
In one possible implementation, the second oscillation frequency range is lower than the first oscillation frequency range.
In one possible implementation, the control circuit includes: a first odd mode switch and a second odd mode switch, and a first even mode switch and a second even mode switch;
the first even mode switch and the second even mode switch are respectively connected with at least one mode capacitor in parallel;
two ends of the first even mode switch are respectively connected to the drains of the first MOS tubes of the two transformer coupled oscillators, and two ends of the second even mode switch are respectively connected to the drains of the second MOS tubes of the two transformer coupled oscillators;
two ends of the first odd-mode switch are respectively connected with the drain electrode of a first MOS tube of one transformer coupled oscillator and the drain electrode of a second MOS tube of the other transformer coupled oscillator, and two ends of the second odd-mode switch are respectively connected with the drain electrode of the second MOS tube of the one transformer coupled oscillator and the drain electrode of the first MOS tube of the other transformer coupled oscillator;
wherein, in the odd mode, the first odd mode switch and the second odd mode switch are turned on, and the first even mode switch and the second even mode switch are turned off; in the even mode, the first odd mode switch and the second odd mode switch are switched off, and the first even mode switch and the second even mode switch are switched on.
In the implementation mode, the two odd mode switches and the two even mode switches can be implemented by the MOS tube working in the switching state, and the on and off of each switch is controlled by the mode control signal, so that the working mode of the dual-mode oscillator is switched between the odd mode and the even mode. In even mode, the mode capacitance CmodeThe switched-on even mode switch bypasses, the oscillation frequency range of the dual-mode oscillator is the same as that of the single transformer coupled oscillator, and the oscillation frequency range of the single transformer coupled oscillator can be adjusted by adjusting the size of the primary capacitor Cs and the secondary capacitor Cp, so that the adjustment of the oscillation frequency range of the high-frequency oscillation signal of the dual-mode oscillator is realized; in odd mode, the mode capacitance CmodeEquivalently, the capacitance of the drain electrode of the dual-mode oscillator is increased by bridging the two ends of the drain electrode of the transformer coupled oscillator, the oscillation frequency range is lower than that of a single transformer coupled oscillator, and C can be adjustedmodeThe magnitude of the value enables adjustment of the oscillation frequency range of the low-frequency oscillation signal of the dual-mode oscillator.
In a second aspect, the present application further provides a multi-phase oscillator, comprising: n dual-mode oscillators as described in any of the above implementations, and N multiphase coupling circuits; n is an integer greater than 1;
each multi-phase coupling circuit is coupled between two dual-mode oscillators; the N dual-mode oscillators form Mobius annular connection through the N multi-phase coupling circuits.
Alternatively, in the Mobius ring connection, N-1 multi-phase coupling circuits are directly coupled between the respective two dual-mode oscillators, and one multi-phase coupling circuit is cross-coupled between the respective two dual-mode oscillators.
In one possible implementation, the N dual-mode oscillators and the N multi-phase coupling circuits form N stages, each stage including a dual-mode oscillator and a multi-phase coupling circuit; the first coupling end of each stage of multiphase coupling circuit is connected to the drain electrode of any transformer coupled oscillator in the stage of dual-mode oscillator, and the second coupling end of each stage of multiphase coupling circuit is connected to the drain electrode of any transformer coupled oscillator in the next stage of dual-mode oscillator.
In one possible implementation, the N dual-mode oscillators and the N multi-phase coupling circuits form N stages, each stage including a dual-mode oscillator and a multi-phase coupling circuit; the first coupling end of each stage of multiphase coupling circuit is connected to two grids of any transformer coupled oscillator in the stage of dual-mode oscillator, and the second coupling end of each stage of multiphase coupling circuit is connected to two grids of any transformer coupled oscillator in the next stage of dual-mode oscillator.
In one possible implementation, the multi-phase coupling circuit includes: coupling the MOS tube pair;
the source electrode of the first coupling MOS tube in the coupling MOS tube pair is connected with the source electrode of the second coupling MOS tube, and is directly grounded or grounded through a current source;
the drain electrode of the first coupling MOS tube and the drain electrode of the second coupling MOS tube are used as the first coupling end and are connected with two drain electrodes or two grid electrodes of any transformer coupling oscillator in the stage of dual-mode oscillator;
and the grid electrode of the first coupling MOS tube and the grid electrode of the second coupling MOS tube are used as the second coupling end and are connected with two drain electrodes or two grid electrodes of any transformer coupling oscillator in the next-stage dual-mode oscillator.
In one possible implementation, the multi-phase coupling circuit includes: a coupled capacitor pair, a coupled inductor pair, or a coupled microstrip line.
The multi-phase oscillator provided by the embodiment of the application is formed by connecting a plurality of dual-mode transformer coupled oscillators into a Mobius ring through a multi-phase coupling circuit, so that not only can multi-phase oscillation signals be generated, but also the phase noise performance of the whole oscillator can be improved. Meanwhile, the multi-phase oscillator provided by the embodiment of the application locks the phases of a pair of transformer coupled oscillators in each dual-mode oscillator into the same-phase or opposite-phase state synchronously through the mode switching circuit based on the same mode control signal, so that only one transformer coupled oscillator in each pair of transformer coupled oscillators is connected with the multi-phase coupling circuit, and the phase output of the whole oscillator array can be determined; therefore, the multi-phase oscillator provided by the embodiment of the application has a simple circuit structure, and the corresponding circuit layout is easier to realize.
Drawings
In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without any creative effort.
Fig. 1 is a circuit configuration diagram of a conventional dual mode oscillator;
fig. 2 is a circuit structure diagram of a dual-mode oscillator according to an embodiment of the present disclosure;
FIG. 3 is a circuit diagram of the dual mode oscillator of FIG. 2 in the even mode;
FIG. 4 is a circuit diagram of the dual-mode oscillator of FIG. 2 in the odd mode;
fig. 5 is a circuit diagram of a transformer-coupled oscillator in a dual-mode oscillator according to an embodiment of the present disclosure;
fig. 6 is a circuit block diagram of a multi-phase oscillator according to an embodiment of the present application;
fig. 7 is a circuit structure diagram of a multi-phase oscillator based on coupled MOS transistor pairs according to an embodiment of the present application;
fig. 8 is a circuit diagram of a multi-phase oscillator based on coupling capacitor pairs according to an embodiment of the present disclosure;
fig. 9 is a circuit diagram of a multiphase oscillator using a gate connection method according to an embodiment of the present disclosure;
fig. 10 is a waveform diagram of a multi-phase oscillation signal generated by a multi-phase oscillator according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 2 is a circuit structure diagram of a dual-mode oscillator according to an embodiment of the present application. The dual mode oscillator may be applied to various fields including a wireless communication system.
As shown in fig. 2, the dual-mode oscillator provided in the embodiment of the present application is designed based on a transformer-coupled oscillator, and specifically may include two transformer-coupled oscillators 210 and 220, and a mode switching circuit 230; the transformer coupled oscillator 210 and the transformer coupled oscillator 220 are connected by a mode switching circuit 230.
First, the circuit configuration of the transformer coupled oscillator will be described. In the embodiment of the present application, the transformer coupled oscillator 210 and the transformer coupled oscillator 220 have the same circuit structure, and are each composed of a differential MOS (Metal Oxide Semiconductor) transistor pair, a primary capacitor Cp, a secondary capacitor Cs, and a step-up transformer. The specific circuit structure of the transformer coupled oscillator 210 will be described as an example.
As shown in fig. 2, the transformer coupled oscillator 210 includes: a differential MOS (Metal Oxide Semiconductor) transistor pair, a primary capacitor Cp, a secondary capacitor Cs, and a step-up transformer 213.
The differential MOS tube pair comprises a first MOS tube 211 and a second MOS tube 212; wherein, the source electrode of the first MOS transistor 211 is connected with the source electrode of the second MOS transistor 212; the drain of the first MOS transistor 211 is connected to one end of the primary capacitor Cp and the first input terminal of the step-up transformer 213, and the drain of the second MOS transistor 212 is connected to the other end of the primary capacitor Cp and the second input terminal of the step-up transformer 213; the gate of the first MOS transistor 211 is connected to one end of the secondary capacitor Cs and the second output terminal of the step-up transformer 213, and the gate of the second MOS transistor 212 is connected to the other end of the secondary capacitor Cs and the first output terminal of the step-up transformer 213. If the first MOS transistor 211 and the second MOS transistor 212 are N-channel MOS transistors (abbreviated as NMOS transistors), the source of the first MOS transistor 211 and the source of the second MOS transistor 212 are grounded through a current source or directly grounded, as shown in fig. 2; if the first MOS transistor 211 and the second MOS transistor 212 are P-channel MOS transistors (abbreviated as PMOS transistors), the source of the first MOS transistor 211 and the source of the second MOS transistor 212 are connected to a constant voltage through a current source or directly, which is described in detail below with reference to fig. 5.
Referring to fig. 2, the boost transformer 213 includes a primary inductor Lp and a secondary inductor Ls respectively connected to the power source VDDAnd a bias voltage Vgate(ii) a The dotted terminal of the primary inductor Lp is a first input terminal of the step-up transformer 213, and the synonym terminal of the primary inductor Lp is a second input terminal of the step-up transformer 213; correspondingly, the dotted terminal of the secondary inductor Ls is the first output terminal of the step-up transformer 213, and the dotted terminal of the secondary inductor Ls is the second output terminal of the step-up transformer 213. That is, the first input terminal and the first output terminal of the step-up transformer 213 are homonymous terminals, and the drain and the gate of the differential MOS transistor pair have an inverse relationship with the connection of the input terminal and the output terminal of the step-up transformer 213. The step-up transformer 213 has a step-up multiple k (k > 1), i.e., the output terminal voltage (corresponding to the voltage across the secondary capacitor Cs) is k times the input terminal voltage (corresponding to the voltage across the primary capacitor Cp). The coupling from the primary inductance Lp to the secondary inductance Ls achieves a boost function.
Two drain terminals of a differential MOS tube pair in the transformer coupled oscillator are used as output ends of the transformer coupled oscillator, and output signals are oscillation signals generated by the transformer coupled oscillator; the oscillation frequency of the oscillation signal can be adjusted by adjusting the sizes of the primary capacitance Cs and the secondary capacitance Cp. Therefore, the primary capacitance Cs and the secondary capacitance Cp may be adjustable capacitances, or the capacitance value of at least one of the two may be adjusted by a control signal.
In the transformer-coupled oscillator, the drain of one MOS transistor is connected to the gate of another MOS transistor through a transformer, so in other implementations, the two gates of the transformer-coupled oscillator may be used as the output terminals; correspondingly, in the dual-mode oscillator obtained by coupling the two transformer coupled oscillators through the mode switching circuit, two grids of any one of the transformer coupled oscillators can also be used as the output end of the dual-mode oscillator.
As shown in fig. 2, the mode switching circuit 230 is located between the two transformer-coupled oscillators 210 and 220, and is connected to the drain output terminals of each of the two transformer-coupled oscillators, respectively, so as to couple the two transformer-coupled oscillators 210 and 220 into a dual-mode oscillator; the output of the dual mode oscillator may be the output of the transformer coupled oscillator 210 or the output of the transformer coupled oscillator 220.
The mode switching circuit 230 specifically includes: control circuit and two mode capacitors C coupled to the control circuitmode. The control circuit comprises a pair of odd-mode switches Sodd1And Sodd2And a pair of even mode switches Seven1And Seven2(ii) a Wherein, two even mode switches Seven1And Seven2Respectively connected with a mode capacitor CmodeAnd (4) connecting in parallel.
First even mode switch Seven1Are respectively connected to the drain of the first MOS transistor 211 in the transformer-coupled oscillator 210 and the drain of the first MOS transistor in the transformer-coupled oscillator 220; second even mode switch Seven2Are respectively connected to the drain of the second MOS transistor 212 in the transformer-coupled oscillator 210 and the drain of the second MOS transistor in the transformer-coupled oscillator 220.
First odd mode switch S0dd1Are respectively connected to the drain of the second MOS transistor 212 in the transformer-coupled oscillator 210 and the drain of the first MOS transistor in the transformer-coupled oscillator 220; second odd-mode switch Sodd2Are respectively connected to the drain of the first MOS transistor 211 in the transformer-coupled oscillator 210 and the drain of the second MOS transistor in the transformer-coupled oscillator 220.
The two odd-mode switches Sodd1And Sodd2And two even mode switches Seven1And Seven2The switching on and off of each switch can be controlled by the MOS tube working in the switching state through the mode control signal.
In the embodiment of the present application, two pairs of switches in the mode switching circuit 230 are turned on alternately, so that the operating mode of the dual-mode oscillator is switched between the odd mode and the even mode, thereby changing the oscillation frequency range of the oscillation signal output by the dual-mode oscillator.
The specific working conditions are as follows:
1) when S iseven1And Seven2Conduction, Sodd1And Sodd2When the circuit is disconnected, the circuit works in an even mode, and the circuit of the dual-mode oscillator is shown as (a) in fig. 3; at the moment, the drain output ends of the two transformer coupled oscillators are connected by a mode capacitor CmodeTwo oscillators are directly connected with two conducted even mode switches and work in the same phase state, namely a mode capacitor CmodeThe waveforms at both ends are the same, no current flows, C can be adjustedmodeEquivalent removal, i.e. CmodeEquivalent to being bypassed, equivalent circuit as shown in fig. 3 (b), the oscillation frequency range of the dual mode oscillator is the same as that of the single transformer coupled oscillator.
2) When S isodd1And Sodd2Conduction, Seven1And Seven2When the circuit is switched off, the circuit works in an odd mode, and the circuit of the dual-mode oscillator is shown as (a) in FIG. 4; at the moment, the drain output ends of the two transformer coupled oscillators are in cross connection with the mode capacitor C through the two conducted odd-mode switchesmodeConnected, the two transformer-coupled oscillators operating in anti-phase, i.e. mode capacitance CmodeThe waveforms at the two ends are voltages output by the two transformer coupled oscillators in a differential mode. Now mode capacitor CmodeWhich may be equivalently connected across the drain of the transformer coupled oscillator, the equivalent circuit is shown in fig. 4 (b). At the moment, the drain capacitance of the whole dual-mode oscillator is increased, and the oscillation frequency range is lower than that of a single transformer coupled oscillator.
Can be seen from oppositeIn a conventional single oscillator, the dual-mode oscillator provided in the embodiment of the present application implements switching between two operating modes through the mode switching circuit, so as to obtain oscillation signals of two different frequency bands, thereby widening an oscillation frequency range; meanwhile, the mode switching circuit couples the two transformer coupled oscillators together, and the phase noise performance can be improved. The oscillation frequency range of the high-frequency oscillation signal obtained in the even mode is the same as that of the single transformer coupled oscillator, so that the oscillation frequency range of the single transformer coupled oscillator can be adjusted by adjusting the sizes of the primary capacitor Cs and the secondary capacitor Cp, and the adjustment of the oscillation frequency range of the high-frequency oscillation signal of the dual-mode oscillator is realized; meanwhile, the oscillation frequency range of the low-frequency oscillation signal obtained in the odd mode and the mode capacitor CmodeIn this connection, it is possible to adjust CmodeThe magnitude of the value enables adjustment of the oscillation frequency range of the low-frequency oscillation signal of the dual-mode oscillator. Therefore, the dual-mode oscillator provided by the embodiment of the application can be used for adjusting the primary capacitor Cs and the secondary capacitor Cp in each transformer coupled oscillator and the mode capacitor C in the mode switching circuitmodeThe output of the oscillation signal in the wide frequency band is realized.
In the existing dual-mode oscillator based on the LC oscillator, the main reason for the poor phase noise performance is that the drain voltage of one MOS transistor of each LC oscillator is directly injected back to the gate of another MOS transistor (as shown in fig. 1), so that the gate voltage is small. In the embodiment of the application, two transformer coupled oscillators are adopted to form a dual-mode oscillator, the drain electrode of the first MOS tube in each transformer coupled oscillator is connected to the grid electrode of the second MOS tube through a step-up transformer, namely the step-up transformer multiplies the voltage swing of the drain electrode of the first MOS tube and injects the multiplied voltage swing into the grid electrode of the second MOS tube, so that a larger grid voltage swing is obtained under the condition that the power supply voltage of the oscillator is not increased, and the phase noise performance of the dual-mode oscillator is improved.
In a possible embodiment of the present invention, the differential MOS transistor pair in the transformer-coupled oscillator may specifically adopt an NMOS transistor pair, as shown in fig. 2, a first MOS transistor 211 and a second MOS transistor 211The MOS transistors 212 are all N-type MOS transistors. At this time, after the source of the first NMOS transistor and the source of the second NMOS transistor are connected, the tail current source may be grounded (as shown in fig. 2); the tail current in fig. 2 can also be removed, and the source electrode of the first NMOS transistor and the source electrode of the second NMOS transistor are directly grounded. In addition, when the differential MOS transistor pair adopts an N-type MOS transistor pair, the center tap of the primary inductor Lp of the step-up transformer 213 is connected to the power supply VDDThe secondary inductor Ls center tap of the step-up transformer is connected with the grid bias voltage V of the NMOS tube (the first NMOS tube or the second NMOS tube)gate。
In a possible embodiment of the present invention, the differential MOS transistor pair in the transformer-coupled oscillator may also be a PMOS transistor pair, such as the transformer-coupled oscillator 510 shown in fig. 5, in which the source of the first PMOS transistor 511 and the source of the second PMOS transistor 512 are connected to the power supply V through a current sourceDD(alternatively, directly connected to the power supply VDD). In addition, the center tap of the primary inductor Lp of the step-up transformer 513 of the transformer coupled oscillator 510 is grounded, and the center tap of the secondary inductor Ls is connected to the gate bias voltage V of the PMOS transistor (the first PMOS transistor or the second PMOS transistor)gate. The other terminals of the transformer coupled oscillator 510 are connected in the same manner as the transformer coupled oscillator 210 described above, and are not described herein again.
In the embodiment of the present application, both transformer-coupled oscillators in the dual-mode oscillator shown in fig. 2 may be replaced by the transformer-coupled oscillator 510 shown in fig. 5, so as to obtain a dual-mode oscillator with another structure, and the operation principle of the dual-mode oscillator is the same as that described above.
In a possible embodiment of the present invention, the primary capacitor Cp and the secondary capacitor Cs of the transformer coupled oscillator can be implemented by at least one of a switched capacitor array and a varactor diode, so as to obtain a capacitance with adjustable values, that is: the primary capacitance Cp is formed by at least one of a first switched capacitor array and a first varactor diode, and the secondary capacitance Cs is formed by at least one of a second switched capacitor array and a second varactor diode. In this embodiment, if the primary capacitor Cp and the secondary capacitor Cs both include a switched capacitor array and a varactor diode, the step adjustment of the capacitance values of the primary capacitor Cp and the secondary capacitor Cs can be realized by changing the number of capacitors in the switched capacitor array to be turned on, and further, the step adjustment of the oscillation frequency of the transformer coupled oscillator is realized; by adjusting the control voltage of the variable capacitance diode, the continuous fine adjustment of the capacitance values of the primary capacitor Cp and the secondary capacitor Cs can be realized, and further the continuous fine adjustment of the oscillation frequency of the transformer coupled oscillator can be realized.
Based on the dual-mode oscillator described in the above embodiments, an embodiment of the present application further provides a multi-phase oscillator, where the multi-phase oscillator includes N dual-mode oscillators provided in any of the above embodiments, and N multi-phase coupling circuits; wherein N is an integer greater than 1. Any multi-phase coupling circuit is coupled between two dual-mode oscillators and used for coupling the coupling point of one dual-mode oscillator to the coupling point of the other dual-mode oscillator, and the coupling point of any dual-mode oscillator can be the output of the dual-mode oscillator, namely, two drains of any transformer coupled oscillator in the dual-mode oscillator or two gates of any transformer coupled oscillator in the dual-mode oscillator. The N dual-mode oscillators form Mobius annular connection through the N multi-phase coupling circuits to form multiple stages, and each stage comprises a dual-mode oscillator and a multi-phase coupling circuit. Namely: the first coupling end of each stage of multiphase coupling circuit is connected to the stage of dual-mode oscillator, and the second coupling end of the N-1 stage of multiphase coupling circuit in the N stage of multiphase coupling circuit is directly connected (in positive phase connection) to the next stage of dual-mode oscillator, namely, the second coupling end is directly coupled; and the second coupling ends of the other stage of multiphase coupling circuit are connected into the next stage of dual-mode oscillator after crossing (in reverse phase connection), namely, cross coupling. In the multiphase oscillator provided in the embodiment of the present application, a value of N may be an integer such as 2, 3, or 4, and a circuit structure of the multiphase oscillator is described below with reference to the accompanying drawings by taking N as an example.
As shown in the block diagram of the multiphase oscillator shown in fig. 6, four dual-mode oscillators, which are respectively numbered 1100, 1200, 1300 and 1400, form a mobius ring connection through four
In this embodiment, the first coupling end of each stage of the multiphase coupling circuit is connected to the coupling point of the stage of the dual-mode oscillator, and the second coupling end of each stage of the multiphase coupling circuit is connected to the coupling point of the next stage of the dual-mode oscillator. Specifically, as shown in fig. 6, a first coupling end of the first-stage
The coupling point of the dual-mode oscillator can be two grids or two drains of any transformer coupling oscillator in the dual-mode oscillator; i.e. in the four-stage case shown in fig. 6, by choosing different transformer coupled oscillators, there can be 24The connection mode includes connecting four transformer-coupled oscillators with
In the block diagram shown in fig. 6, two output terminals of the first-stage
Compared with the problem that the conventional dual-mode oscillator only can generate two-phase differential signals as shown in fig. 1, the multi-phase oscillator provided by the embodiment of the application is formed by connecting a plurality of dual-mode transformer coupled oscillators into a mobius ring through a multi-phase coupling circuit, so that not only can multi-phase oscillation signals be generated (2N-phase oscillation signals can be generated by N pairs of transformer coupled oscillators), but also the phase noise performance of the whole oscillator can be improved.
Meanwhile, the multi-phase oscillator provided by the embodiment of the application locks the phases of a pair of transformer coupled oscillators in each dual-mode oscillator into the same-phase or opposite-phase state synchronously through the mode switching circuit based on the same mode control signal, so that only one transformer coupled oscillator in each pair of transformer coupled oscillators is connected with the multi-phase coupling circuit, and the phase output of the whole oscillator array can be determined; therefore, the multi-phase oscillator provided by the embodiment of the application has a simple circuit structure, and the corresponding circuit layout is easier to realize.
In a possible embodiment of the present application, the multi-phase coupling circuit in the multi-phase oscillator may be implemented by coupling MOS transistor pairs, and accordingly, the block diagram shown in fig. 6 may be implemented as the circuit structure shown in fig. 7.
In this embodiment, the first coupling end of each stage of the multiphase coupling circuit is connected to the coupling point of the stage of the dual-mode oscillator, and the second coupling end of each stage of the multiphase coupling circuit is connected to the coupling point of the next stage of the dual-mode oscillator. As shown in fig. 6, the first coupling end of the first stage multiphase coupling circuit 610 is connected to two drains of the transformer coupled oscillator 1110 in the first stage dual-mode oscillator 1100, and the second coupling end of the first stage multiphase coupling circuit 610 is connected to two drains of the transformer coupled oscillator 1210 in the second stage dual-mode oscillator 1200; the first coupling end of the second stage multiphase coupling circuit 620 is connected to the two drains of the transformer coupled oscillator 1210 in the second stage dual-mode oscillator 1200, and the second coupling end of the second stage multiphase coupling circuit 620 is connected to the two drains of the transformer coupled oscillator 1310 in the third stage dual-mode oscillator 1300; the first coupling end of the third-stage multi-phase coupling circuit 630 is connected to the two drains of the transformer-coupled oscillator 1310 in the third-stage dual-mode oscillator 1300, and the second coupling end of the third-stage multi-phase coupling circuit 630 is connected to the two drains of the transformer-coupled oscillator 1410 in the fourth-stage dual-mode oscillator 1400; the first coupling end of the fourth stage multiphase coupling circuit 640 is connected to two drains of the transformer coupled oscillator 1410 in the fourth stage dual-mode oscillator 1400, and the second coupling end of the fourth stage multiphase coupling circuit 640 is connected to two drains of the transformer coupled oscillator 1110 in the first stage dual-mode oscillator 1100 after crossing.
Referring to fig. 7, each stage of the multiphase coupling circuit is composed of a pair of coupling MOS transistors, two drains of the pair of coupling MOS transistors serve as a first coupling terminal of the multiphase coupling circuit, and two gates of the pair of coupling MOS transistors serve as a second coupling terminal of the multiphase coupling circuit. Taking the fourth-stage
In other embodiments, the second coupling terminals of the fourth stage
It should be noted that, in order to ensure the circuit of the attached drawing to be simple and easy to read, the circuit diagram shown in fig. 7 does not actually show the connection between the output end of the multi-phase coupling circuit and the next-stage dual-mode oscillator, and the relevant personnel can determine according to the voltage label marked therein, that is, two end points with the same voltage label are actually connected end points. In addition, each transformer-coupled oscillator in fig. 7 adopts a transformer-coupled oscillator based on an NMOS transistor, and in other embodiments, the transformer-coupled oscillator based on a PMOS transistor as described in fig. 5 may be replaced.
In another possible embodiment of the present application, the multi-phase coupling circuit in the multi-phase oscillator may be implemented by a coupling capacitor pair, and accordingly, the block diagram shown in fig. 6 may be implemented as the circuit structure shown in fig. 8.
Referring to fig. 8, the fourth stage
In other embodiments of the present application, the multi-phase coupling circuit in the multi-phase oscillator may also be implemented by a coupling inductor pair or a coupling microstrip line, and a corresponding circuit diagram may be as shown in fig. 8 (i.e., the coupling capacitor pair in fig. 8 is replaced by the coupling inductor pair or the coupling microstrip line).
In the multi-phase oscillator described in the above embodiments, the two first coupling terminals and the two second coupling terminals of the multi-phase coupling circuit are both connected to the drains of the MOS transistors in the corresponding dual-mode oscillator, and in other possible embodiments of the present application, the two first coupling terminals and the two second coupling terminals of the multi-phase coupling circuit may also be connected to the gates of the MOS transistors in the corresponding dual-mode oscillator, as shown in fig. 9. The circuit shown in fig. 9 still takes N-4, and the connection manner of the multi-phase coupling circuit is determined according to the voltage labels in fig. 9, so that the circuit diagram is simple and easy to read.
Based on the circuit shown in fig. 7, the embodiment of the present invention designs a dual-mode eight-phase oscillator by using a CMOS (Complementary Metal oxide semiconductor) process. The circuit is simulated and displayed to realize eight-phase output, the waveform is shown in fig. 10 (the abscissa is time Times, the unit is nanosecond ns, the ordinate is voltage V, the unit is volt V), the frequency range is even mode: 29.97-37.91 GHz; odd mode: 26.03-30.51 GHz.
The following table 1 compares the performance of the multi-phase oscillator provided in the embodiment of the present application With the performance of the oscillators (i.e., the oscillator ISSCC2013 based on the CMOS process, the oscillator ISSCC2013 based on the SiGe (Silicon Germanium Silicon) process, and the oscillator ISSCC2016 based on the CMOS process) disclosed in recent years, where fom (measure of Merit) is an oscillator quality factor comprehensively considering the oscillator frequency, the power consumption, and the phase noise, and fomt (measure of Merit With tuning range) is an oscillator quality factor comprehensively considering the oscillator frequency, the power consumption, the phase noise, and the frequency range. The expressions are respectively:
FoM＝20log(f0/Δf)-PN-10log(PDC/1mW)；
FoMT＝20log(f0/Δf·FTR/10)-PN-10log(PDC/1mW)。
wherein, f in the above formula0Denotes an oscillation frequency, 4f denotes a frequency offset corresponding to phase noise, FTR (frequency Tuning Range) denotes a frequency adjustment range, PN (phase noise) denotes a phase noise value, and P denotes a frequency offset corresponding to phase noiseDCRepresenting dc power consumption), 1mW is 1mW of unit power value.
TABLE 1 comparison of Oscillator Performance
As can be seen from the comparison of table 1, with the CMOS process, superior FoM and FoMT were obtained compared to other CMOS designs. Therefore, the oscillator provided by the embodiment of the application can comprehensively meet the requirements of low power consumption, high phase noise performance, wide frequency range and multiple phases, and has advantages in manufacturing cost.
The above-described embodiments of the present application do not limit the scope of the present application. The structure of the above embodiments can be applied to the field of integrated circuits. "connection" as used in embodiments of the present invention expresses a coupling relationship on a signal, for example, a connection of one end point to another end point may implement signal transmission, and such connection may include direct connection or indirect connection.
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