CN-122026814-A - Digital control oscillator based on harmonic impedance tuning

CN122026814ACN 122026814 ACN122026814 ACN 122026814ACN-122026814-A

Abstract

The invention discloses a digital control oscillator based on harmonic impedance tuning, which comprises a first MOS tube, a second MOS tube, a transformer with a center tap, a coarse tuning capacitor group, a medium tuning capacitor group and a harmonic impedance tuning network, wherein a source electrode of the first MOS tube is connected with a source electrode of the second MOS tube, a source electrode common point is grounded through the harmonic impedance tuning network, a grid electrode of the first MOS tube is connected with a drain electrode of the second MOS tube, a drain electrode of the first MOS tube is connected with a grid electrode of the second MOS tube, a center tap of the transformer is connected with a VDD power supply, two ends of a primary coil of the transformer are respectively connected with the drain electrode of the first MOS tube and the drain electrode of the second MOS tube, a first end of the medium tuning capacitor group is connected with a first end of a secondary coil of the transformer, and a second end of the medium tuning capacitor group is connected with a second end of a secondary coil of the transformer. The invention has high resolution, monotonic frequency tuning, and can optimize phase noise performance.

Inventors

WU LIANG
Lv Yuetong

Assignees

香港中文大学（深圳）

Dates

Publication Date: 20260512
Application Date: 20260414

Claims (7)

1. The digital control oscillator based on harmonic impedance tuning is characterized by comprising a first MOS tube M1, a second MOS tube M2, a transformer with a center tap, a coarse tuning capacitor group, a medium tuning capacitor group and a harmonic impedance tuning network; the source electrode of the first MOS tube M1 is connected with the source electrode of the second MOS tube M2, and the common point of the source electrodes is grounded through a harmonic impedance tuning network; The grid electrode of the first MOS tube M1 is connected with the drain electrode of the second MOS tube M2, and the drain electrode of the first MOS tube M1 is connected with the grid electrode of the second MOS tube M2; The central tap of the transformer is connected with a VDD power supply, and two ends of a primary coil of the transformer are respectively connected with a drain electrode of the first MOS tube M1 and a drain electrode of the second MOS tube M2; The coarse adjustment capacitor group is connected between the drain electrode of the first MOS tube and the drain electrode of the second MOS tube.
2. The digitally controlled oscillator based on harmonic impedance tuning of claim 1, wherein the first MOS transistor M1 and the second MOS transistor M2 are NMOS transistors.
3. The digitally controlled oscillator of claim 1, wherein the transformer has a turns ratio of 2:1, a primary inductance of L1, a secondary inductance of L2, and a coupling coefficient of k.
4. The digitally controlled oscillator of claim 1, wherein the coarse tuning capacitor bank is a 4-bit coarse tuning capacitor bank C C_bank <3:0>, and the medium tuning capacitor bank is an 8-bit medium tuning capacitor bank C M_bank <7:0>; the coarse tuning capacitor group C C_bank <3:0> comprises four parallel branches, and each branch is formed by a switch series capacitor; The medium-tuning capacitor group C M_bank <7:0> comprises eight parallel branches, each branch being formed by a switched series capacitor.
5. The digitally controlled oscillator of claim 1, wherein the harmonic impedance tuning network comprises a first tail inductor L f1 , a second tail inductor L f2 and a fine tuning capacitor bank, one end of the first tail inductor L f1 is connected with a first end of the fine tuning capacitor bank, the other end of the first tail inductor L f1 is grounded, one end of the second tail inductor L f2 is connected with a second end of the fine tuning capacitor bank, the other end of the second tail inductor L f2 is grounded, and the first end of the fine tuning capacitor bank is also connected with the source common point.
6. The digitally controlled oscillator of claim 5, wherein the first tail inductor L f1 and the second tail inductor L f2 are octagonal, the first tail inductor L f1 is larger in size than the second tail inductor L f2 , and the second tail inductor L f2 is nested within the first tail inductor L f1 so that the two inductors form a coupled inductor pair.
7. The digitally controlled oscillator of claim 5 wherein said fine tuning capacitor bank is an 8-bit fine tuning capacitor bank C F_bank <7:0>; the fine tuning capacitor bank C F_bank <7:0> includes eight parallel branches, each branch consisting of switched series capacitors.

Description

Digital control oscillator based on harmonic impedance tuning Technical Field The invention relates to the field of oscillators, in particular to a digital control oscillator based on harmonic impedance tuning. Background In an all-digital phase-locked loop, a digitally controlled oscillator is a major determinant of its frequency accuracy and in-band phase noise. The frequency resolution of the digitally controlled oscillator is directly converted to quantization-induced phase errors, limiting the achievable performance of the system. As the requirements of wireless transceivers for low error vector magnitude and stringent spectral shielding continue to increase, the need for digitally controlled oscillators to achieve frequency resolution in the kilohertz range is increasingly stringent. In the prior art, the method for improving the resolution of the numerically controlled oscillator faces fundamental limitations that the realization of the effective capacitance stepping of the sub-flight method level through direct capacitance tuning is physically extremely difficult and is dominated by process deviation and parasitic effects, the magnetic coupling which is required to be too weak when the kHz level resolution is pursued is seriously influenced by a capacitance scaling technology based on a transformer, and the effective tuning weight of the method is equivalent to uncertainty introduced by device mismatch and parasitic effects when the kHz level resolution interval is entered on the basis of a C-2C ladder network or capacitance degradation technology and the like, so that predictability and reliability are limited. Furthermore, while the use of the Groszkowski effect (i.e., harmonic components resulting in an oscillation frequency offset) to account for oscillator noise up-conversion has been widely recognized, this effect is rarely actively used in beneficial circuit designs to achieve frequency tuning. Disclosure of Invention The invention aims to overcome the defects of the prior art, and provides a digitally controlled oscillator based on harmonic impedance tuning, which utilizes and actively controls Groszkowski effect to transfer the task of fine frequency tuning from a main resonant circuit sensitive to phase noise to a harmonic domain, so that ultra-high resolution and monotonic frequency tuning can be realized and phase noise performance can be optimized at the same time under the condition that effective capacitance or inductance of a fundamental resonant circuit is not required to be directly disturbed. The invention aims at realizing the technical scheme that the digital control oscillator based on harmonic impedance tuning comprises a first MOS tube M1, a second MOS tube M2, a transformer with a center tap, a coarse tuning capacitor group, a medium tuning capacitor group and a harmonic impedance tuning network; the source electrode of the first MOS tube M1 is connected with the source electrode of the second MOS tube M2, and the common point of the source electrodes is grounded through a harmonic impedance tuning network; The grid electrode of the first MOS tube M1 is connected with the drain electrode of the second MOS tube M2, and the drain electrode of the first MOS tube M1 is connected with the grid electrode of the second MOS tube M2; The central tap of the transformer is connected with a VDD power supply, and two ends of a primary coil of the transformer are respectively connected with a drain electrode of the first MOS tube M1 and a drain electrode of the second MOS tube M2; The coarse adjustment capacitor group is connected between the drain electrode of the first MOS tube and the drain electrode of the second MOS tube. Further, the first MOS transistor M1 and the second MOS transistor M2 are both NMOS transistors. Further, the transformer adopts a transformer with the turns ratio of 2:1, the inductance of the primary coil of L1, the inductance of the secondary coil of L2 and the coupling coefficient of k. Further, the coarse tuning capacitor group is a 4-bit coarse tuning capacitor group C C_bank <3:0>, and the medium tuning capacitor group is an 8-bit medium tuning capacitor group C M_bank <7:0>; the coarse tuning capacitor group C C_bank <3:0> comprises four parallel branches, and each branch is formed by a switch series capacitor; The medium-tuning capacitor group C M_bank <7:0> comprises eight parallel branches, each branch being formed by a switched series capacitor. Further, the harmonic impedance tuning network comprises a first tail inductor L f1, a second tail inductor L f2 and a fine tuning capacitor group, one end of the first tail inductor L f1 is connected with a first end of the fine tuning capacitor group, the other end of the first tail inductor L f1 is grounded, one end of the second tail inductor L f2 is connected with a second end of the fine tuning capacitor group, the other end of the second tail inductor L f2 is grounded, and the first end of the fine tuning