阅读说明：本技术 一种新型低噪声压控振荡器 (Novel low-noise voltage-controlled oscillator ) 是由 傅海鹏 郑玉学 马凯学 于 2019-09-25 设计创作，主要内容包括：本发明公开新型低噪声压控振荡器,包括双LC tank构成的电感电容谐振腔,MOS管MP1、MOS管MP2,MOS管MN1、MOS管MN2；MOS管MP1、MOS管MP2源极连接后接VDD,MOS管MP1栅极接MOS管MP2漏极,MOS管MP2栅极接MOS管MP1漏极；MOS管MN1、MOS管MN2源极连接后接地,MOS管MN1、MOS管MN2漏极分别与MOS管MP1、MOS管MP2漏极相接,MOS管MN1栅极接MOS管MN2漏极,MOS管MN2栅极接MOS管MN1栅极。本发明在保证低功耗的前提下,实现高的摆幅要求；有效解决了基波和二次谐波相位非对准条件下相位噪声差的问题。(The invention discloses a novel low-noise voltage-controlled oscillator, which comprises an inductance-capacitance resonant cavity formed by double LC tank, an MOS tube MP1, an MOS tube MP2, an MOS tube MN1 and an MOS tube MN 2; the source electrodes of the MOS tube MP1 and the MOS tube MP2 are connected and then connected with VDD, the grid electrode of the MOS tube MP1 is connected with the drain electrode of the MOS tube MP2, and the grid electrode of the MOS tube MP2 is connected with the drain electrode of the MOS tube MP 1; the source electrodes of the MOS tube MN1 and the MOS tube MN2 are connected and then grounded, the drains of the MOS tube MN1 and the MOS tube MN2 are respectively connected with the drains of the MOS tube MP1 and the MOS tube MP2, the grid electrode of the MOS tube MN1 is connected with the drain electrode of the MOS tube MN2, and the grid electrode of the MOS tube MN2 is connected with the grid electrode of the MOS tube MN 1. The invention realizes the requirement of high swing amplitude on the premise of ensuring low power consumption; the problem of poor phase noise under the condition of phase misalignment of fundamental waves and second harmonics is effectively solved.)

1. A novel low-noise voltage-controlled oscillator is characterized by comprising an inductance-capacitance resonant cavity formed by double LCtanks, an MOS tube MP1, an MOS tube MP2, an MOS tube MN1 and an MOS tube MN 2; the source electrodes of the MOS tube MP1 and the MOS tube MP2 are connected and then connected with VDD, the grid electrode of the MOS tube MP1 is connected with the drain electrode of the MOS tube MP2, and the grid electrode of the MOS tube MP2 is connected with the drain electrode of the MOS tube MP 1; the source electrodes of the MOS tube MN1 and the MOS tube MN2 are connected and then grounded, the drains of the MOS tube MN1 and the MOS tube MN2 are respectively connected with the drains of the MOS tube MP1 and the MOS tube MP2, the grid electrode of the MOS tube MN1 is connected with the drain electrode of the MOS tube MN2, the grid electrode of the MOS tube MN2 is connected with the grid electrode of the MOS tube MN1, and two ends of one LCtank of the double LCtanks are respectively connected with the connecting lines of the drains of the MOS tube MN1 and the MOS tube MN2, which correspond to the drains of the MOS tube MP1 and the MOS tube MP 2; and the phase difference between the fundamental wave and the second harmonic is eliminated by utilizing double LCtank weak coupling so as to improve the phase noise performance of the voltage-controlled oscillator.

2. The novel low-noise voltage-controlled oscillator as claimed in claim 1, wherein the dual LCtank includes an inductor L1, an inductor L2, two variable capacitors Cv1, two variable capacitors Cv2, the inductor L1 is connected in series with the two variable capacitors Cv1 to form a unit, the inductor L2 is connected in series with the two variable capacitors Cv2 to form another unit, and the control voltage Vt is respectively connected between the two variable capacitors Cv1 and between the two variable capacitors Cv 2.

Technical Field

The invention relates to the technical field of low-noise voltage-controlled oscillators, in particular to a novel low-noise voltage-controlled oscillator.

Background

In order to meet the requirement of bit error rate in the communication standard and improve the sensitivity of the millimeter wave radar receiver, the phase noise of a voltage-controlled oscillator in a millimeter wave frequency source needs to be reduced. With the development of the CMOS process, the thickness of the gate oxide layer of the transistor is thinner and thinner, the tolerable breakdown voltage is lower and lower, and the available bias voltage is smaller and smaller, so that the output swing of the oscillator is smaller and smaller, and the phase noise is further reduced. As the oscillation frequency enters the millimeter wave band, the gate length of the transistor required at this time to satisfy the barkhausen oscillation condition becomes shorter and shorter, which causes 1/f noise of the transistor to increase sharply, and the noise to further decrease. Meanwhile, compared with a low-frequency oscillator, a large amount of parasitic capacitance is introduced into the layout, the parasitic capacitance can reduce the characteristic frequency and the intrinsic gain of the transistor, and the phase noise performance is further reduced.

At present, for the problems of low output swing and poor phase noise of an oscillator, the first is to use a source-drain transformer coupled voltage controlled oscillator (TFVCO), which utilizes source-drain voltage dual-signal swing coupling, and the source-drain voltage swing is in reverse phase while the source-drain transformer is in reverse phase coupling, so that the output swing of the oscillator exceeds the power supply voltage. The TFVCO boosts the output swing using source-drain voltage coupling, but without boosting the intrinsic gain of the transistor, i.e. without optimizing the swing of the signal before coupling. Secondly, on the basis of the TFVCO, a differential Colpitts swing enhanced VCO (ESDC-VCO) is proposed. The source inductor replaces a tail current source of the traditional Colpitts, and meanwhile, feedback between a source terminal and a drain terminal is achieved by using a capacitor.

However, the above two methods have problems that the swing of the fundamental wave is increased and the swing of the second and higher harmonics, particularly the second harmonic, is also increased, and a phase difference between the fundamental wave and the higher harmonic is introduced due to the nonlinear effect of the transistor, and the phase difference enters the fundamental wave along with the mixing of the fundamental wave and the second harmonic, and becomes a phase noise near the fundamental wave, and thus a VCO with high phase noise performance is not realized.

Therefore, how to solve the problems of parasitic increase of the transistor, low intrinsic gain, low quality factor of the passive device and the like along with the increase of the oscillation frequency, and obtaining the millimeter wave oscillator with low noise becomes a technical problem which needs to be solved in the millimeter wave application.

Disclosure of Invention

The invention aims to provide a novel low-noise voltage-controlled oscillator aiming at the problems of large parasitics, low gains and low Q values of passive devices of active devices in a millimeter wave frequency band, so that the voltage-controlled oscillator with high-performance phase noise in a wider frequency band is realized, and the voltage-controlled oscillator has a better application prospect.

The technical scheme adopted for realizing the purpose of the invention is as follows:

a novel low-noise voltage-controlled oscillator comprises an inductance-capacitance resonant cavity formed by double LC tank, an MOS tube MP1, an MOS tube MP2, an MOS tube MN1 and an MOS tube MN 2; the source electrodes of the MOS tube MP1 and the MOS tube MP2 are connected and then connected with VDD, the grid electrode of the MOS tube MP1 is connected with the drain electrode of the MOS tube MP2, and the grid electrode of the MOS tube MP2 is connected with the drain electrode of the MOS tube MP 1; the source electrodes of the MOS tube MN1 and the MOS tube MN2 are connected and then grounded, the drains of the MOS tube MN1 and the MOS tube MN2 are respectively connected with the drains of the MOS tube MP1 and the MOS tube MP2, the grid electrode of the MOS tube MN1 is connected with the drain electrode of the MOS tube MN2, the grid electrode of the MOS tube MN2 is connected with the grid electrode of the MOS tube MN1, and two ends of one LC tank in the double LC tanks are respectively connected with the connecting lines of the drains of the MOS tube MN1 and the MOS tube MN2, which are correspondingly connected with the drains of the MOS tube MP1 and the MOS tube MP 2; and the phase difference between the fundamental wave and the second harmonic is eliminated by utilizing double LCtank weak coupling so as to improve the phase noise performance of the voltage-controlled oscillator.

The double LC tank comprises an inductor L1, an inductor L2, two variable capacitors Cv1 and two variable capacitors Cv2, wherein the inductor L1 and the two variable capacitors Cv1 are connected in series to form a unit, the inductor L2 and the two variable capacitors Cv2 are connected in series to form another unit, and control voltages Vt are respectively connected between the two variable capacitors Cv1 and between the two variable capacitors Cv 2.

The invention can realize high swing amplitude requirement on the premise of ensuring low power consumption; the problem of poor phase noise under the condition of phase misalignment of fundamental waves and second harmonics is effectively solved; the topological structure is simple, and the integration is convenient.

Drawings

FIG. 1 is a flow chart of the design of the novel low noise voltage controlled oscillator of the present invention;

FIG. 2 is a diagram of a Dual-tank structure of a transformer coupling;

FIG. 3 is a circuit topology diagram of the novel low noise voltage controlled oscillator according to the present invention;

fig. 4-5 are diagrams of performance effects of the novel low-noise voltage-controlled oscillator for realizing alignment of fundamental waves and second harmonics and improving phase noise respectively.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention adopts double LCtank (inductance capacitance resonant cavity) weak coupling to eliminate the phase difference between the fundamental wave and the second harmonic wave so as to improve the phase noise performance of the voltage-controlled oscillator.

As shown in fig. 3, the novel low-noise voltage-controlled oscillator of the present invention includes an LC resonant cavity, a MOS transistor MP1, a MOS transistor MP2, a MOS transistor MN1, and a MOS transistor MN 2; the source electrodes of the MOS tube MP1 and the MOS tube MP2 are connected and then connected with VDD, the grid electrode of the MOS tube MP1 is connected with the drain electrode of the MOS tube MP2, and the grid electrode of the MOS tube MP2 is connected with the drain electrode of the MOS tube MP 1; the source electrodes of the MOS tube MN1 and the MOS tube MN2 are connected and then grounded, the drains of the MOS tube MN1 and the MOS tube MN2 are respectively connected with the drains of the MOS tube MP1 and the MOS tube MP2, the grid electrode of the MOS tube MN1 is connected with the drain electrode of the MOS tube MN2, the grid electrode of the MOS tube MN2 is connected with the grid electrode of the MOS tube MN1, and two ends of one LC tank in the double LC tanks are respectively connected with the connecting lines of the drains of the MOS tube MN1 and the MOS tube MN2, which correspond to the drains of the MOS tube MP1 and the MOS tube MP 2.

The double LC tank comprises an inductor L1, an inductor L2, two variable capacitors Cv1 and two variable capacitors Cv2, wherein the inductor L1 and the two variable capacitors Cv1 are connected in series to form a unit, the inductor L2 and the two variable capacitors Cv2 are connected in series to form another unit, and VDD is connected between the two variable capacitors Cv1 and between the two variable capacitors Cv2 respectively.

FIG. 2 shows a transformer-coupled double tank structure, which can achieve resonance separation, two resonance frequency points, high frequency ω_HAnd a low frequency omega_LThe invention requires omega_H/ω_LThe alignment of fundamental wave and second harmonic is realized by 2, and the phase noise performance is improved. The two resonance frequencies are formed by the intrinsic resonance frequency ratio ξ (ω) of the coupling coefficient K and the double tank₁/ω₂)²Of decision

L_1,2、C_1,2The parameter is the capacitance and inductance of the resonant cavity in fig. 2.

Referring to fig. 1, in design, the eigenfrequency ratio ξ of double tank is first determined by the coupling coefficient K to realize ω_H/ω_L2. After the eigenfrequency ratio is determined, the desired operating frequency ω is used₀＝ω_LThis condition, the eigenfrequency of the double tan is determined

Phase noise and frequency modulation range and inductance L_1,2Capacitor C_1,2The value of (a) is relevant, so that the inductance L needs to be continuously optimized_1,2Capacitor C_1,2The values determine the final topology.

The invention adopts double-tank weak coupling to eliminate the phase difference of fundamental wave and second harmonic. How the coupled tank pair achieves resonance separation, the relationship between the two-frequency-point frequencies generated after resonance separation, and how phase alignment between the fundamental wave and the second harmonic is achieved by using resonance separation will be specifically described below.

The noise introduced by the aligned and misaligned fundamental and second harmonics is analyzed. Assuming the oscillation is stable, the fundamental signal is expressed as:

A₀cos(ω₀t) (1)

wherein A is₀Representing the amplitude, omega, of the fundamental signal₀Which is indicative of the frequency of the fundamental wave signal,

(1) at phase alignment, the second harmonic is expressed as:

A₁cos(2ω₀t) (2)

wherein A is₁Representing the amplitude of the second harmonic, 2 omega₀Which represents the frequency of the second harmonic signal,

mixing the second harmonic and the fundamental wave:

(2) when the phase is misaligned, the second harmonic is expressed as:

whereinIndicating the phase difference of the fundamental and second harmonics,

mixing the second harmonic and the fundamental wave:

from the above analysis, it can be seen that the fundamental wave introduces a quantity when the phases of the fundamental wave and the second harmonic are not aligned

This quantity is the effect that produces additional phase noise. The method provided by the invention can effectively eliminate the effect, because when the fundamental wave and the second harmonic are aligned, no extra phase is generated

The weak coupling of the transformer is described below to achieve frequency separation and phase alignment of the fundamental and second harmonics by means of the coupling.

How to achieve the alignment of the fundamental and second harmonics is described below in conjunction with the transformer-coupled dual-tank pair of fig. 2. The transformer coupling transformer impedance of fig. 2 can be represented by a simple impedance matrix:

where ω denotes the operating angular frequency

The impedance of the coupled tank two-port network is described by the impedance matrix of the transformer:

according to the Barkhausen condition, the negative resistance provided by the transistor is assumed to be-G_mAnd obtaining a loop gain condition and a phase condition.

Wherein

Representative impedance Z₁₁The real part of the reciprocal of the signal,

representative impedance Z₁₁The imaginary part of the reciprocal.

Two oscillation frequencies are obtained using equation (8 b):

wherein the content of the first and second substances,

ξ＝(ω₁/ω₂)²，ω₁represents the eigenresonance frequency, ω, of tank1₂Represents the eigenfrequency, ω, of tank2_HRepresenting the high frequency, omega, after resonance splitting_LRepresenting the low frequency after resonance separation.

When two oscillation frequencies are just placed at omega_H/ω_LWhen the frequency is located at the resonance frequency, the impedance of the resonance frequency is a pure real part, and the fundamental wave and the second harmonic have no phase difference (the generation of the phase difference is caused by an imaginary part of the impedance), so that the phase noise performance of the oscillator can be effectively improved. The specific effect is shown in fig. 4-5.

As can be seen from fig. 4-5, under the alignment condition, the superposition of the fundamental wave and the second harmonic wave is closer to the square wave, the waveform is more symmetrical, and the phase noise performance is better.

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.