阅读说明：本技术 一种基于变压器耦合的堆叠压控振荡器 (Stacking and stacking voltage-controlled oscillator based on transformer coupling ) 是由 孙辉 汪浩 傅海鹏 于 2021-09-06 设计创作，主要内容包括：本发明提供了一种基于变压器耦合的堆叠压控振荡器,包括核心振荡电路,核心振荡电路包括两组对称设置的差分对管,差分对管由具有差分对结构的NMOS管M1、NMOS管M2组成,NMOS管M1的栅极和NMOS管M2的栅极之间连接有两组电感L1；核心振荡电路分别连接有选频电路和用于将两路差分信号转换成单路输出差分信号的巴伦电路；核心振荡电路还连接有用于隔离核心振荡电路和巴伦电路的输出环冲电路,输出缓冲电路包括NMOS管M3、NMOS管M4,NMOS管M3的栅极和NMOS管M4的栅极之间连接有两组电感L2；两组电感L1与两组电感L2形成磁耦合变压器。本发明有效解决了传统的太赫兹基波压控振荡器输出功率低、相噪性能差等问题,从而实现高性能太赫兹基波压控振荡器。(The invention provides a stack voltage-controlled oscillator based on transformer coupling, which comprises a core oscillation circuit, wherein the core oscillation circuit comprises two groups of symmetrically arranged differential pair transistors, each differential pair transistor comprises an NMOS (N-channel metal oxide semiconductor) transistor M1 and an NMOS transistor M2, and two groups of inductors L1 are connected between a grid electrode of the NMOS transistor M1 and a grid electrode of the NMOS transistor M2; the core oscillation circuit is respectively connected with a frequency selection circuit and a balun circuit for converting the two paths of differential signals into a single path of output differential signals; the core oscillation circuit is also connected with an output ring-flushing circuit for isolating the core oscillation circuit from the balun circuit, the output buffer circuit comprises an NMOS tube M3 and an NMOS tube M4, and two groups of inductors L2 are connected between the grid of the NMOS tube M3 and the grid of the NMOS tube M4; the two sets of inductors L1 form a magnetic coupling transformer with the two sets of inductors L2. The terahertz fundamental wave voltage-controlled oscillator effectively solves the problems of low output power, poor phase noise performance and the like of the traditional terahertz fundamental wave voltage-controlled oscillator, and therefore the high-performance terahertz fundamental wave voltage-controlled oscillator is achieved.)

1. The utility model provides a pile pressure-controlled oscillator based on transformer coupling which characterized in that: the differential pair transistors are composed of an NMOS transistor M1 and an NMOS transistor M2 which have a differential pair structure, and two groups of inductors L1 are connected between the grid of the NMOS transistor M1 and the grid of the NMOS transistor M2;

the core oscillation circuit is respectively connected with a frequency selection circuit and a balun circuit for converting the two paths of differential signals into a single path of output differential signals;

the core oscillation circuit is also connected with an output ring-flushing circuit for isolating the core oscillation circuit from the balun circuit, the output buffer circuit comprises an NMOS tube M3 and an NMOS tube M4, and two groups of inductors L2 are connected between the grid of the NMOS tube M3 and the grid of the NMOS tube M4;

the two sets of inductors L1 form a magnetic coupling transformer with the two sets of inductors L2.

2. The transformer coupling based stack voltage-controlled oscillator of claim 1, wherein: the drain electrode of the NMOS tube M1 is connected with the source electrode of the NMOS tube M3 through a microstrip transmission line TL1, and the drain electrode of the NMOS tube M2 is connected with the source electrode of the NMOS tube M4 through a microstrip transmission line TL 1;

the sources of the NMOS transistor M1 and the NMOS transistor M2 are both connected with a frequency selection circuit.

3. The transformer coupling based stack voltage-controlled oscillator of claim 1, wherein: two groups of inductors L1 are sequentially connected in series between the grid of the NMOS tube M1 and the grid of the NMOS tube M2;

the common connection end of the two groups of inductors L1 is connected with a power supply voltage Vg 1;

two groups of inductors L2 are sequentially connected in series between the grid of the NMOS tube M3 and the grid of the NMOS tube M4;

and the common connection end of the two secondary coil inductors L2 is connected with a power supply voltage Vg 2.

4. The transformer coupling based stack voltage-controlled oscillator of claim 1, wherein: the frequency selection circuit comprises two groups of capacitors C1 connected in series, wherein the two groups of capacitors C1 are respectively connected with the source electrodes of an NMOS tube M1 and an NMOS tube M2;

the sources of the NMOS transistor M1 and the NMOS transistor M2 are grounded through a microstrip transmission line TL2 respectively;

the common connection of the two sets of capacitors C1 is connected to the capacitor C2 via a microstrip transmission line TL3, the capacitor C2 being connected to ground.

5. The transformer coupling based stack voltage-controlled oscillator of claim 1, wherein: the balun circuit comprises two groups of inductors L3 connected in series, wherein the two groups of inductors L3 are respectively connected with the drains of an NMOS tube M3 and an NMOS tube M4;

the common connecting end of the two groups of inductors L3 is connected with a power supply voltage Vdd;

the inductor L4 is further included, a magnetic coupling structure is formed by the inductor L4 and the inductor L3, one end of the inductor L4 is grounded, the other end of the inductor L4 is connected with a bonding pad, and the bonding pad is connected with the external resistor RL.

Technical Field

The invention belongs to the technical field of terahertz oscillators, and particularly relates to a stack voltage-controlled oscillator based on transformer coupling.

Background

Terahertz waves are located between submillimeter waves and far infrared rays, and are electromagnetic wave frequency bands which have not been completely developed and applied so far. The terahertz wave has the unique advantages of penetrability, safety, broadband and the like, so that the terahertz wave has a very wide application scene in the fields of wireless communication systems, public safety detection, imaging, biomedicine, astronomical observation and the like. Terahertz sources with higher output power are the basis for realizing the above applications.

For a silicon-based integrated system, a terahertz voltage-controlled oscillator is an important method for realizing a terahertz source, so that research and realization of a high-performance terahertz voltage-controlled oscillator become the research focus in the field of silicon-based integrated circuits at present. CMOS technology has become the main choice for silicon-based integrated circuits due to its advantages of low cost and easy integration. However, the thz frequency has approached or even exceeded fmax for most existing process nodes, which results in a rapid degradation of the transistor performance. In order to alleviate the problem, the main choice of designing the terahertz oscillator based on the CMOS process at present is to extract higher harmonics so as to obtain a lower fundamental oscillation frequency. But extracting higher harmonics results in limited output power and waste of fundamental energy, so the DC-RF efficiency of the circuit is low. Although the method of power synthesis with multiple cores can be used to improve the output power and optimize the noise performance, it inevitably results in high power consumption and a large amount of chip area is sacrificed.

The terahertz oscillator directly realized by using the fundamental wave can avoid the waste of fundamental wave energy caused by harmonic wave extraction, and avoids high power consumption and large area caused by multi-core power synthesis, so that the design is relatively simple, but because the oscillation frequency is close to the process fmax and limited by low power supply voltage, the output power of the terahertz voltage-controlled oscillator realized based on the fundamental wave is very limited, and the comprehensive performance of the terahertz voltage-controlled oscillator is still in a certain gap compared with the currently best terahertz oscillator realized by adopting higher harmonic wave to perform power synthesis.

In summary, aiming at the problems of low output power and poor phase noise of the conventional CMOS terahertz fundamental wave voltage-controlled oscillator, a novel circuit topology structure is urgently needed to solve the problems of the terahertz fundamental wave oscillator, so that the terahertz fundamental wave voltage-controlled oscillator with high power and low phase noise is designed.

Disclosure of Invention

In view of this, the present invention provides a stacked voltage-controlled oscillator based on transformer coupling, so as to solve the problems of low output power and poor phase noise of the conventional CMOS terahertz fundamental wave voltage-controlled oscillator.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a stack voltage-controlled oscillator based on transformer coupling comprises a core oscillation circuit, wherein the core oscillation circuit comprises two groups of symmetrically arranged differential pair transistors, each differential pair transistor comprises an NMOS transistor M1 and an NMOS transistor M2, and two groups of inductors L1 are connected between the grid of the NMOS transistor M1 and the grid of the NMOS transistor M2;

the core oscillation circuit is respectively connected with a frequency selection circuit and a balun circuit for converting the two paths of differential signals into a single path of output differential signals;

the core oscillation circuit is also connected with an output ring-flushing circuit for isolating the core oscillation circuit from the balun circuit, the output buffer circuit comprises an NMOS tube M3 and an NMOS tube M4, and two groups of inductors L2 are connected between the grid of the NMOS tube M3 and the grid of the NMOS tube M4;

the two sets of inductors L1 form a magnetic coupling transformer with the two sets of inductors L2.

Furthermore, the drain of the NMOS transistor M1 is connected to the source of the NMOS transistor M3 through a microstrip transmission line TL1, and the drain of the NMOS transistor M2 is connected to the source of the NMOS transistor M4 through a microstrip transmission line TL 1;

the sources of the NMOS transistor M1 and the NMOS transistor M2 are both connected with a frequency selection circuit.

Further, two groups of inductors L1 are sequentially connected in series between the gate of the NMOS transistor M1 and the gate of the NMOS transistor M2;

the common connection end of the two groups of inductors L1 is connected with a power supply voltage Vg 1;

two groups of inductors L2 are sequentially connected in series between the grid of the NMOS tube M3 and the grid of the NMOS tube M4;

and the common connection end of the two secondary coil inductors L2 is connected with a power supply voltage Vg 2.

Furthermore, the frequency selection circuit comprises two groups of capacitors C1 connected in series, wherein the two groups of capacitors C1 are respectively connected with the sources of the NMOS transistor M1 and the NMOS transistor M2;

the sources of the NMOS transistor M1 and the NMOS transistor M2 are grounded through a microstrip transmission line TL2 respectively;

the common connection of the two sets of capacitors C1 is connected to the capacitor C2 via a microstrip transmission line TL3, the capacitor C2 being connected to ground.

Further, the balun circuit comprises two groups of inductors L3 connected in series, wherein the two groups of inductors L3 are respectively connected with the drains of the NMOS transistor M3 and the NMOS transistor M4;

the common connecting end of the two groups of inductors L3 is connected with a power supply voltage Vdd;

the inductor L4 is further included, a magnetic coupling structure is formed by the inductor L4 and the inductor L3, one end of the inductor L4 is grounded, the other end of the inductor L4 is connected with a bonding pad, and the bonding pad is connected with the external resistor RL.

Compared with the prior art, the stack voltage-controlled oscillator based on transformer coupling has the following beneficial effects:

(1) according to the stack voltage-controlled oscillator based on transformer coupling, the anti-interference capability and stability of a circuit can be improved by adopting a differential structure, and the symmetry of the differential structure is favorable for layout; in addition, the inductor can be realized in a differential structure, and has a higher Q value compared with a single-ended inductor, so that the phase noise performance of the circuit can be improved;

(2) the stack voltage-controlled oscillator based on transformer coupling can effectively improve the output oscillation amplitude by adopting a stack structure, so that the power synthesis is not required to be carried out by adopting multi-core coupling to improve the output power, the design is simpler to realize, and the stack voltage-controlled oscillator has lower power consumption and compact area while obtaining higher output power;

(3) the stack voltage-controlled oscillator based on transformer coupling is based on coupling of two-stage transistor grid inductors, and can greatly improve the grid swing of a core oscillator transistor, so that the phase noise of a circuit can be effectively reduced.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic circuit diagram of a stacked voltage-controlled oscillator based on transformer coupling according to an embodiment of the present invention;

fig. 2 is an equivalent circuit diagram of a transformer-coupling-based stacked voltage-controlled oscillator schematic diagram after coupling according to an embodiment of the present invention;

FIG. 3 is a graph of transistor gate power and circuit phase noise as a function of coupling coefficient k1 according to an embodiment of the present invention;

fig. 4 is a diagram of post-simulation results of the circuit according to the embodiment of the present invention.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

As shown in fig. 1, a stack voltage-controlled oscillator based on transformer coupling includes a core oscillation circuit, where the core oscillation circuit includes two sets of symmetrically arranged differential pair transistors, each differential pair transistor is composed of an NMOS transistor M1 and an NMOS transistor M2 with a differential pair structure, and two sets of inductors L1 are connected between a gate of the NMOS transistor M1 and a gate of the NMOS transistor M2;

the core oscillation circuit is respectively connected with a frequency selection circuit and a balun circuit for converting the two paths of differential signals into a single path of output differential signals;

the core oscillation circuit is also connected with an output ring-flushing circuit for isolating the core oscillation circuit from the balun circuit, the output buffer circuit comprises an NMOS tube M3 and an NMOS tube M4, and two groups of inductors L2 are connected between the grid of the NMOS tube M3 and the grid of the NMOS tube M4; the NMOS tube M3 and the NMOS tube M4 can be used as buffers to realize the isolation of the balun circuit and the core oscillation circuit, and reduce the influence of factors such as parasitic capacitance of devices such as the balun and the like on the core circuit;

the two sets of inductors L1 form a magnetic coupling transformer with the two sets of inductors L2.

The drain electrode of the NMOS tube M1 is connected with the source electrode of the NMOS tube M3 through a microstrip transmission line TL1, and the drain electrode of the NMOS tube M2 is connected with the source electrode of the NMOS tube M4 through a microstrip transmission line TL 1; the NMOS tube M1 and the NMOS tube M2 are cascaded with the NMOS tube M3 and the NMOS tube M4 to improve the power supply voltage Vdd swing amplitude and further improve the drain electrode output swing amplitude, the microstrip transmission line TL1 is used for adjusting the phase shift between two stages, and the parasitic network of the ice-river transistor realizes the grid signal phase inversion of the two-stage stacked tubes together;

the sources of the NMOS transistor M1 and the NMOS transistor M2 are both connected with a frequency selection circuit.

Two groups of inductors L1 are sequentially connected in series between the grid of the NMOS tube M1 and the grid of the NMOS tube M2;

the common connection end of the two groups of inductors L1 is connected with a power supply voltage Vg 1;

two groups of inductors L2 are sequentially connected in series between the grid of the NMOS tube M3 and the grid of the NMOS tube M4;

the common connecting end of the two secondary coil inductors L2 is connected with a power supply voltage Vg 2;

by arranging the inductor L1 and the inductor L2, on one hand, grid bias is provided for the two-stage NMOS tube, and on the other hand, a transformer is formed to carry out coupling to realize signal transmission of the two-stage tube, so that a differential oscillation mode is enhanced. The design changes the parasitic capacitance of the NMOS transistor by changing the bias voltage of the grid electrode to realize the voltage-controlled tuning function, thereby avoiding the use of a variable capacitance diode, and the inductor L1 and the inductor L2 can feed the grid signal part at the top back to the grid electrode at the bottom through coupling, thereby realizing the energy transfer and the frequency traction between two layers of transistors.

The frequency selection circuit comprises two groups of capacitors C1 connected in series, wherein the two groups of capacitors C1 are respectively connected with the source electrodes of an NMOS tube M1 and an NMOS tube M2;

the sources of the NMOS transistor M1 and the NMOS transistor M2 are grounded through a microstrip transmission line TL2 respectively;

the common connecting end of the two groups of capacitors C1 is connected with the capacitor C2 through a microstrip transmission line TL3, and the capacitor C2 is grounded; the microstrip transmission line TL2 is used to provide a dc path and forms a frequency selective network with the differential capacitor pair C1 and the microstrip transmission line TL3 to further enhance the differential performance, and the capacitor C2 is used to define an ac ground for the microstrip transmission line TL 3.

The balun circuit comprises two groups of inductors L3 connected in series, wherein the two groups of inductors L3 are respectively connected with the drains of an NMOS tube M3 and an NMOS tube M4;

the common connecting end of the two groups of inductors L3 is connected with a power supply voltage Vdd;

the inductor L4 is further included, a magnetic coupling structure is formed by the inductor L4 and the inductor L3, one end of the inductor L4 is grounded, the other end of the inductor L4 is connected with a bonding pad, and the bonding pad is connected with an external resistor RL; the inductor L3 and the inductor L4 form a balun circuit to realize the conversion of differential signals into single-ended output, and the balun circuit has the advantages that on one hand, two paths of signals can be synthesized and converted into single-ended output, so that the output power is improved (theoretically, 3dB is improved); on the other hand, the separation of the alternating current signal and the direct current signal is realized without additionally designing a DC blocking capacitor.

When coupling is considered, the equivalent model of the circuit after decoupling the transformer is shown in FIG. 2, where the mutual inductancek1 is the coupling coefficient between inductor L1 and inductor L2. The gate voltages of the NMOS tube M1 and the NMOS tube M2 are in an inverse relation in a circuit differential oscillation mode, the gate voltages of the NMOS tube M1 and the NMOS tube M3 can also be in an inverse relation by means of phase shift caused by parasitic effects of the tubes and selection of a proper length of an inter-stage transmission line, and the gate part energy of the NMOS tube M3 can be superposed on the gate of the NMOS tube M2 in the same direction by adjusting the directions of the same-name ends of a primary coil and a secondary coil of a transformer; under the condition, the transformer coupling plays a role similar to cross coupling, which is favorable for further improving the differential stability of the circuit, and the gate voltage swing of the core oscillation transistor M2 can be enhanced through the transformer coupling, so that the drain voltage swing of the NMOS transistor M2 is improved.

Under the condition that the two layers of gate inductance values are set to be constant, the gate output swing and the phase noise of the bottom layer of the NMOS transistor M1 and the NMOS transistor M2 are plotted as the coupling coefficient k1 in fig. 3. It can be seen that as the coupling coefficient increases, the gate energy transfer of the top NMOS transistor M3 and NMOS transistor M4 and the core transistors M1 and M2 gradually increases, and the gate swing of the NMOS transistor M1 and NMOS transistor M2 increases greatly as the coupling increases, so that the phase noise is obviously improved compared with the case of no coupling.

And performing circuit post-simulation after the parasitic effect of the whole layout is extracted. Under the condition that the supply voltage VDD is 2.4V, the tuning range obtained by changing gate biases Vg1 and Vg2 is 177.4 GHz-181 GHz, the tuning bandwidth is 2%, and the simulation result is shown in FIG. 4 (a); the curve of the output power changing with the tuning voltage is shown in fig. 4(b), and the application of the stacked structure increases the voltage swing, so that the circuit realizes higher output power, and when the gate bias changes, the output power changes from-0.47 dBm to 0.8 dBm; the variation curve of the phase noise simulated at the frequency offset of 1MHz is shown in FIG. 4 (c); the stacked structure brings output swing amplitude improvement, the transformer coupling enables the gate swing amplitude of the core transistor to be greatly improved, and the Colpitts structure has low phase noise characteristics, so that the circuit achieves good phase noise performance, and the optimal phase noise obtained through simulation is-94.5 dBc/Hz; with the change of bias, the direct current power consumption of the circuit fluctuates in the range of 20.9-26.2 mW, because the circuit directly adopts fundamental wave to realize output, energy waste caused by extracting higher harmonics is avoided, and the use of a stacked structure improves the output power, the design realizes high efficiency, the peak value DC-RF efficiency of the circuit can reach 4.7%, the efficiency in a tuning range is higher than 3.9%, and the simulation result is shown in fig. 4 (d).

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.