阅读说明：本技术 一种基于多振荡核心的太赫兹压控振荡器 (Terahertz voltage-controlled oscillator based on multi-oscillation core ) 是由 李芹 冯可瞧 于 2021-07-19 设计创作，主要内容包括：本发明公开了一种基于多振荡核心的太赫兹压控振荡器,利用多个振荡核心并联,降低负阻,根据振荡器的指标要求设计连接各VCO振荡核心的传输,最后将振荡信号输入缓冲放大器电路与倍频器电路。该结构在工艺受限的情况下,可以有效地降低无源器件的值,实现较好的相位噪声,为太赫兹频段收发前端提供高品质本振信号。(The invention discloses a terahertz voltage-controlled oscillator based on multiple oscillation cores, which utilizes the parallel connection of multiple oscillation cores to reduce negative resistance, designs transmission connected with each VCO oscillation core according to the index requirement of an oscillator, and finally inputs oscillation signals into a buffer amplifier circuit and a frequency multiplier circuit. The structure can effectively reduce the value of a passive device under the condition of limited process, realizes better phase noise and provides high-quality local oscillation signals for the terahertz frequency band transceiving front end.)

1. A terahertz voltage-controlled oscillator based on a double-oscillation core is characterized by comprising a distributed oscillator, a buffer output stage and a frequency multiplier, wherein the distributed oscillator is formed by connecting two cross-coupled oscillation units in series and parallel with a transmission line; the cross-coupled oscillation unit is composed of a pair of NMOS tubes and two inductors; the gate of the transistor MN1 of the first cross-coupled oscillation unit is connected with the drain of the transistor MN2 through an inductor L4, the gate of the transistor MN2 is connected with the drain of the transistor MN1 through an inductor L3, and the sources of the transistor MN1 and the transistor MN2 are grounded; the drains of the transistor MN1 and the transistor MN2 are connected through the coplanar waveguides L1 and L2, and the common end of the coplanar waveguides L1 and L2 which are connected is connected to a power supply voltage; the gate of the transistor MN3 of the second cross-coupled oscillation unit is connected with the drain of the transistor MN4 through an inductor L8, the gate of the transistor MN4 is connected with the drain of the transistor MN3 through an inductor L7, and the sources of the transistor MN3 and the transistor MN4 are grounded; the drains of the transistor MN1 and the transistor MN3 are connected through a coplanar waveguide L5; the drains of the transistor MN2 and the transistor MN4 are connected through a coplanar waveguide L6; the buffer output stage comprises NMOS tubes MN7 and MN 8; one ends of varactors VA1 and VA2 are connected to a voltage control end, the other ends of varactors VA1 and VA2 are respectively connected with the grids of NMOS transistors MN7 and MN8, and are connected with the drains of transistors MN3 and MN4 through coplanar waveguides L9 and L10; and the buffer output stage is connected with the frequency multiplier through a transformer.

2. The terahertz voltage-controlled oscillator based on the double-oscillation core as claimed in claim 1, wherein inductance values of coplanar waveguides L1, L2, L9 and L10 are equal, and inductance values of coplanar waveguides L5 and L6 are equal.

3. A terahertz voltage-controlled oscillator based on a three-oscillation core is characterized by comprising a distributed oscillator, a buffer output stage and a frequency multiplier, wherein the distributed oscillator is formed by connecting three cross-coupled oscillation units and a transmission line in series-parallel connection; the cross-coupled oscillation unit is composed of a pair of NMOS tubes and two inductors; the gate of the transistor MN1 of the first cross-coupled oscillation unit is connected with the drain of the transistor MN2 through an inductor L4, the gate of the transistor MN2 is connected with the drain of the transistor MN1 through an inductor L3, and the sources of the transistor MN1 and the transistor MN2 are grounded; the drains of the transistor MN1 and the transistor MN2 are connected through the coplanar waveguides L1 and L2, and the common end of the coplanar waveguides L1 and L2 which are connected is connected to a power supply voltage; the gate of the transistor MN3 of the second cross-coupled oscillation unit is connected with the drain of the transistor MN4 through an inductor L8, the gate of the transistor MN4 is connected with the drain of the transistor MN3 through an inductor L7, and the sources of the transistor MN3 and the transistor MN4 are grounded; the gate of the transistor MN5 of the third cross-coupled oscillation unit is connected with the drain of the transistor MN6 through an inductor L12, the gate of the transistor MN6 is connected with the drain of the transistor MN5 through an inductor L11, and the sources of the transistor MN5 and the transistor MN6 are grounded; the drains of the transistor MN1 and the transistor MN3 are connected through a coplanar waveguide L5, the drains of the transistor MN3 and the transistor MN5 are connected through a coplanar waveguide L9, the drains of the transistor MN2 and the transistor MN4 are connected through a coplanar waveguide L6, and the drains of the transistor MN4 and the transistor MN6 are connected through a coplanar waveguide L10; the buffer output stage comprises NMOS tubes MN7 and MN 8; one ends of varactors VA1 and VA2 are connected to a voltage control end, the other ends of varactors VA1 and VA2 are respectively connected with the grids of NMOS transistors MN7 and MN8, and are connected with the drains of transistors MN3 and MN4 through coplanar waveguides L9 and L10; and the buffer output stage is connected with the frequency multiplier through a transformer.

4. The terahertz voltage-controlled oscillator based on the triple-oscillation core as claimed in claim 3, wherein inductance values of coplanar waveguides L1, L2, L9 and L10 are equal, and inductance values of coplanar waveguides L5 and L6 are equal.

Technical Field

The invention relates to a millimeter wave terahertz frequency band CMOS multi-core voltage-controlled oscillator for generating terahertz frequency band constant-amplitude oscillation signals.

Background

Terahertz (Tera-hertz), i.e. electromagnetic waves in the frequency range of 0.1T to 10 THz, corresponds to wavelengths between 3 mm and 30 μm, and belongs to non-ionizing radiation. In recent years, terahertz is concerned about researches in aspects of object imaging, astronomical detection, ultra-wideband high-speed communication systems and the like, a terahertz signal source is used as a key part of terahertz application, and performance indexes of the terahertz signal source directly influence the performance of the system. The terahertz signal can be indirectly acquired by adopting a frequency doubling chain mode, namely, the required terahertz frequency is acquired by the high-quality microwave low-frequency signal through multiple times of frequency doubling, and the terahertz frequency acquisition circuit has the advantages of higher frequency stability, lower power consumption and the like. In the design of a frequency doubling chain circuit, a millimeter wave terahertz frequency band voltage-controlled oscillator is indispensable.

The millimeter wave terahertz voltage-controlled oscillator is the most basic module in a radio frequency system, can realize the conversion from direct current power to radio frequency power, and generates stable sinusoidal oscillation at a certain determined frequency point, so that the terahertz voltage-controlled oscillator with good design and realization performance is the reliable guarantee of circuit performance. The technical indexes of the voltage-controlled oscillator mainly include center frequency, tuning range, output power, phase noise and the like. The design difficulty of the terahertz frequency band voltage-controlled oscillator is how to ensure good output power, tuning range and phase noise.

A common terahertz voltage controlled oscillator structure consists of a ring oscillator, a three-point oscillator, and a cross-coupled oscillator. In contrast, the cross-coupled oscillation structure is commonly found in the use of CMOS process, and the Colpitts structure is commonly found in BJT process. But various factors influence the use of the voltage-controlled oscillator in the silicon-based CMOS terahertz chip. On one hand, in a terahertz frequency band, parasitic series inductance of the transistor has non-negligible influence on a feedback path and the whole core, so that the tunable range of the variable capacitor is limited, and on the other hand, large capacitance or capacitance array tuning is introduced, so that the Q value of the LC resonant cavity is greatly reduced, and the contradiction between the tuning range and phase noise is more prominent. From the perspective of extracting harmonics, because of the limited frequencies that can be achieved by the fundamental frequency oscillator, a double-push oscillator or an N-push oscillator is conventionally adopted to achieve a higher frequency. Although the Push-Push oscillator has an easy oscillation frequency, the efficiency of power conversion is too low.

Therefore, in the terahertz voltage-controlled oscillator circuit, how to reduce the phase noise of the passive device and improve the oscillation frequency of the oscillator becomes a key attractive problem.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the prior art, the terahertz voltage-controlled oscillator based on the multi-oscillation core is provided, the phase noise of a passive device is reduced, and the tuning range of the oscillator is improved.

The technical scheme is as follows: a terahertz voltage-controlled oscillator based on a double-oscillation core comprises a distributed oscillator, a buffer output stage and a frequency multiplier, wherein the distributed oscillator is formed by connecting two cross-coupled oscillation units and a transmission line in series-parallel connection; the cross-coupled oscillation unit is composed of a pair of NMOS tubes and two inductors; the gate of the transistor MN1 of the first cross-coupled oscillation unit is connected with the drain of the transistor MN2 through an inductor L4, the gate of the transistor MN2 is connected with the drain of the transistor MN1 through an inductor L3, and the sources of the transistor MN1 and the transistor MN2 are grounded; the drains of the transistor MN1 and the transistor MN2 are connected through the coplanar waveguides L1 and L2, and the common end of the coplanar waveguides L1 and L2 which are connected is connected to a power supply voltage; the gate of the transistor MN3 of the second cross-coupled oscillation unit is connected with the drain of the transistor MN4 through an inductor L8, the gate of the transistor MN4 is connected with the drain of the transistor MN3 through an inductor L7, and the sources of the transistor MN3 and the transistor MN4 are grounded; the drains of the transistor MN1 and the transistor MN3 are connected through a coplanar waveguide L5; the drains of the transistor MN2 and the transistor MN4 are connected through a coplanar waveguide L6; the buffer output stage comprises NMOS tubes MN7 and MN 8; one ends of varactors VA1 and VA2 are connected to a voltage control end, the other ends of varactors VA1 and VA2 are respectively connected with the grids of NMOS transistors MN7 and MN8, and are connected with the drains of transistors MN3 and MN4 through coplanar waveguides L9 and L10; and the buffer output stage is connected with the frequency multiplier through a transformer.

A terahertz voltage-controlled oscillator based on a triple-oscillation core comprises a distributed oscillator, a buffer output stage and a frequency multiplier, wherein the distributed oscillator is formed by connecting three cross-coupled oscillation units and a transmission line in series-parallel; the cross-coupled oscillation unit is composed of a pair of NMOS tubes and two inductors; the gate of the transistor MN1 of the first cross-coupled oscillation unit is connected with the drain of the transistor MN2 through an inductor L4, the gate of the transistor MN2 is connected with the drain of the transistor MN1 through an inductor L3, and the sources of the transistor MN1 and the transistor MN2 are grounded; the drains of the transistor MN1 and the transistor MN2 are connected through the coplanar waveguides L1 and L2, and the common end of the coplanar waveguides L1 and L2 which are connected is connected to a power supply voltage; the gate of the transistor MN3 of the second cross-coupled oscillation unit is connected with the drain of the transistor MN4 through an inductor L8, the gate of the transistor MN4 is connected with the drain of the transistor MN3 through an inductor L7, and the sources of the transistor MN3 and the transistor MN4 are grounded; the gate of the transistor MN5 of the third cross-coupled oscillation unit is connected with the drain of the transistor MN6 through an inductor L12, the gate of the transistor MN6 is connected with the drain of the transistor MN5 through an inductor L11, and the sources of the transistor MN5 and the transistor MN6 are grounded; the drains of the transistor MN1 and the transistor MN3 are connected through a coplanar waveguide L5, the drains of the transistor MN3 and the transistor MN5 are connected through a coplanar waveguide L9, the drains of the transistor MN2 and the transistor MN4 are connected through a coplanar waveguide L6, and the drains of the transistor MN4 and the transistor MN6 are connected through a coplanar waveguide L10; the buffer output stage comprises NMOS tubes MN7 and MN 8; one ends of varactors VA1 and VA2 are connected to a voltage control end, the other ends of varactors VA1 and VA2 are respectively connected with the grids of NMOS transistors MN7 and MN8, and are connected with the drains of transistors MN3 and MN4 through coplanar waveguides L9 and L10; and the buffer output stage is connected with the frequency multiplier through a transformer.

Has the advantages that: 1. the cores of the cross-coupled oscillators are connected in parallel, so that the negative resistance part of the VCO is reduced, the influence of parasitic capacitance introduced by the size of a transistor is reduced, and the numerical value of the adopted LC network is reduced and the Q value is increased. Under the condition that the varactor device is maintained unchanged, the wide tuning range can be realized, the load carrying capacity is higher, and the better phase noise is achieved.

2. A coplanar waveguide with the ground is designed in the VCO, and the Q value of a passive device is guaranteed. By adjusting the ratio of inductance and inductance values of the coplanar waveguides L1 and L5, the phase noise and tuning range of the voltage-controlled oscillator can be adjusted slightly, and the requirement on the variable capacitance value of the variable capacitance device is reduced.

Drawings

Fig. 1 is a circuit diagram of a conventional VCO;

FIG. 2 is a circuit diagram of a VCO based on dual oscillating cores according to the present invention;

fig. 3 is a circuit diagram of a VCO based on a triple-oscillation core according to the present invention;

FIG. 4 is a plot of the tuning range of a conventional single-core VCO;

FIG. 5 is a phase noise simulation result of a conventional single-core VCO;

FIG. 6 is a tuning range curve for a dual core VCO in accordance with the present invention;

FIG. 7 is a phase noise plot for a dual core VCO in accordance with the present invention;

FIG. 8 is a tuning range curve for a three-core VCO in accordance with the teachings of the present invention;

fig. 9 is a phase noise curve of a three-core VCO according to the present invention.

Detailed Description

The invention is further explained below with reference to the drawings.

The traditional oscillator starts from increasing the Q value of a varactor and increases the Q value of a resonant network, but other undesirable performance losses are easily caused in a terahertz frequency band. According to the invention, at the fundamental frequency of 110GHz, based on a multi-core parallel structure, the problem that the tuning effect of the varactor is greatly influenced by the parasitic capacitance of an MOS (metal oxide semiconductor) tube is solved, and a terahertz waveband voltage-controlled oscillator is designed. Meanwhile, the output power of the oscillator is improved by using the buffer and the frequency multiplier circuit, and the problem that the oscillation power of the terahertz frequency band voltage-controlled oscillator is too low is solved. The technology has general practicability, has use value in a D wave band, and can be used as a good solution of a voltage-controlled oscillator at higher frequency.

Example 1

As shown in fig. 2, a terahertz voltage-controlled oscillator based on a double-oscillation core includes a distributed oscillator, a buffer output stage and a frequency multiplier, wherein the distributed oscillator is formed by connecting two cross-coupled oscillation units in series and parallel with a transmission line. The cross-coupled oscillation unit is composed of a pair of NMOS tubes and two inductors. The gate of the transistor MN1 of the first cross-coupled oscillation unit is connected with the drain of the transistor MN2 through an inductor L4, the gate of the transistor MN2 is connected with the drain of the transistor MN1 through an inductor L3, and the sources of the transistor MN1 and the transistor MN2 are grounded; the drains of the transistor MN1 and the transistor MN2 are connected through the coplanar waveguides L1 and L2, and the common end of the coplanar waveguides L1 and L2 is connected to a power supply voltage. The gate of the transistor MN3 of the second cross-coupled oscillation unit is connected with the drain of the transistor MN4 through an inductor L8, the gate of the transistor MN4 is connected with the drain of the transistor MN3 through an inductor L7, and the sources of the transistor MN3 and the transistor MN4 are grounded. The drains of the transistor MN1 and the transistor MN3 are connected through a coplanar waveguide L5; the drains of the transistor MN2 and the transistor MN4 are connected by a coplanar waveguide L6. The buffer output stage comprises NMOS tubes MN7 and MN 8. Varactors VA1 and VA2 are used for realizing varactor tuning, one ends of varactors VA1 and VA2 are connected to a voltage control end Vtune, the other ends of varactors VA1 and VA2 are connected with the gates of NMOS transistors MN7 and MN8 respectively, and the varactors VA1 and VA2 are connected with the drains of a transistor MN3 and a transistor MN4 through coplanar waveguides L9 and L10. The buffer output stage is connected with the frequency multiplier through a transformer. The frequency multiplier consists of NMOS tubes MN9 and MN 10; the transformer consists of L13, L14, L15 and L16, and achieves the functions of impedance matching and direct current isolation.

The inductance values of coplanar waveguides L1, L2, L9 and L10 are equal, the inductance values of coplanar waveguides L5 and L6 are equal, and the oscillator characteristic is equal to two inductances L1_、The ratio of the inductance values of L5.

Example 2

As shown in fig. 3, the terahertz voltage-controlled oscillator based on the triple-oscillation core comprises a distributed oscillator, a buffer output stage and a frequency multiplier, wherein three cross-coupled oscillation units are connected in series and parallel with a transmission line. The cross-coupled oscillation unit consists of a pair of NMOS tubes and two inductors; the gate of the transistor MN1 of the first cross-coupled oscillation unit is connected with the drain of the transistor MN2 through an inductor L4, the gate of the transistor MN2 is connected with the drain of the transistor MN1 through an inductor L3, and the sources of the transistor MN1 and the transistor MN2 are grounded; the drains of the transistor MN1 and the transistor MN2 are connected through the coplanar waveguides L1 and L2, and the common end of the coplanar waveguides L1 and L2 is connected to a power supply voltage. The gate of the transistor MN3 of the second cross-coupled oscillation unit is connected with the drain of the transistor MN4 through an inductor L8, the gate of the transistor MN4 is connected with the drain of the transistor MN3 through an inductor L7, and the sources of the transistor MN3 and the transistor MN4 are grounded. The gate of the transistor MN5 of the third cross-coupled oscillation unit is connected with the drain of the transistor MN6 through the inductor L12, the gate of the transistor MN6 is connected with the drain of the transistor MN5 through the inductor L11, and the sources of the transistor MN5 and the transistor MN6 are grounded. The drains of the transistor MN1 and the transistor MN3 are connected through a coplanar waveguide L5, the drains of the transistor MN3 and the transistor MN5 are connected through a coplanar waveguide L9, the drains of the transistor MN2 and the transistor MN4 are connected through a coplanar waveguide L6, and the drains of the transistor MN4 and the transistor MN6 are connected through a coplanar waveguide L10. The buffer output stage comprises NMOS tubes MN7 and MN 8. Varactors VA1 and VA2 are used for realizing varactor tuning, one ends of varactors VA1 and VA2 are connected to a voltage control end Vtune, the other ends of varactors VA1 and VA2 are connected with the gates of NMOS transistors MN7 and MN8 respectively, and the varactors VA1 and VA2 are connected with the drains of a transistor MN3 and a transistor MN4 through coplanar waveguides L9 and L10. The buffer output stage is connected with the frequency multiplier through a transformer. The frequency multiplier consists of NMOS tubes MN9 and MN 10; the transformer consists of L13, L14, L15 and L16, and achieves the functions of impedance matching and direct current isolation.

The inductance values of coplanar waveguides L1, L2, L9 and L10 are equal, the inductance values of coplanar waveguides L5 and L6 are equal, and the oscillator characteristic is related to the ratio of the inductance values of two inductors L1 and L5.

The embodiment adopts a 40nm CMOS process to prepare the VCO working in the terahertz frequency band. The process has 10 layers of metal, wherein M10 is thick metal. The parameters of the VCO oscillating circuit in this embodiment are shown in table 1:

TABLE 1

Parameter(s)	Parameter value
		VCO supply voltage (V)	0.9
Drain inductance L (pH)	12
		Oscillating nmos tube M1 size	1μm×14/40nm
Variable capacitance CVAR(capacity)	8f—20fF
		Gate series inductance L (pH)	10
VCO tube quiescent operating point current Id (mA)	10

The parameters of the buffer output stage in this embodiment are shown in table 2:

TABLE 2

Parameter(s)	Parameter value
		Buffer output stage supply voltage (V)	0.9
Buffer output stage nmos tube M2 size	1μm×10/40nm
		Buffer output stage tube static working point current Id (mA)	4.23

The parameters of the frequency multiplier circuit in this embodiment are shown in table 3:

TABLE 3

Parameter(s)	Parameter value
		Frequency doubler supply voltage (V)	0.9
Size of frequency multiplier nmos tube M3	1μm×30/40nm
		Static operating point current Id (mA) of frequency multiplier tube	5
Primary inductance L (pH)/Q value of transformer	71pH/15
		L (pH)/Q value of secondary inductor of transformer	87pH/15
Coefficient of coupling	0.6
		L matching inductance value L (pH)/Q value	27pH/15
L matching capacitance C (fF)/Q	12.44fF/31

In order to verify the correctness and effectiveness of the VCO based on the multi-oscillation core proposed by the present invention, a comparative simulation verification was performed with the conventional single-core VCO as shown in fig. 1.

Simulation results of the conventional single-core VCO and the dual-core VCO and the triple-core VCO implemented by the present invention are shown in fig. 4, fig. 5, fig. 6, fig. 7, fig. 8 and fig. 9, and circuit parameters of each circuit except for the resonant cavity inductance L and the variable capacitance are not changed.

Fig. 4 and 5 are graphs showing simulation results of a single-core VCO with a conventional structure. FIG. 4 is a graph of the tuning range of the frequency of Vtune, which shifts from 214 GHz to 226.7GHz when the voltage of Vtune changes from 0.1V to 2.6V. FIG. 5 is a plot of its phase noise at each tuning frequency, with the worst phase noise being-81.5 dBc @1MHz, and most preferably-82.3 dBc @1 MHz.

Fig. 6 and 7 are graphs showing simulation results of the dual-core VCO of the present embodiment. FIG. 6 is a graph of the tuning range of the Vtune, which shifts from 212.9 GHz to 227.6GHz when the voltage of Vtune changes from 0.1V to 2.6V. FIG. 7 is a plot of phase noise at each tuning frequency, with the worst phase noise being-84.7 dBc @1MHz, and most preferably-86.2 dBc @1 MHz.

Fig. 8 and 9 are graphs showing simulation results of the three-core VCO of the present example. FIG. 8 is a graph of the tuning range of the voltage Vtune, which shifts from 213.4GHz to 224.8GHz when the voltage of Vtune changes from 0.1V to 2.6V. FIG. 9 is a plot of its phase noise at each tuning frequency, which is worst-85.7 dBc @1MHz, and most preferably-87.5 dBc @1 MHz.

From the results of fig. 4, 6, and 8, it can be seen that when the voltage of the control voltage terminal Vc is changed from 0.1V to 2.6V under the same load, the tuning range is similar and is not deteriorated. The tuning range of the dual-core VCO is optimal and is 14.7 GHz. The tuning range of the three-core VCO is not dominant because the transistor size is not changed to control the variables.

From the results of fig. 5, 7, and 9, it can be seen that the multi-core VCO can effectively improve the phase noise.

The comparison shows that the multi-core voltage-controlled oscillator adopted by the invention can keep better phase noise and output power under the condition that the tuning range is basically unchanged.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.