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EP-4738698-A1 - OSCILLATOR CIRCUITS WITH FLICKER NOISE SUPPRESSION BY PHASE-SHIFTED SELF-INJECTION

EP4738698A1EP 4738698 A1EP4738698 A1EP 4738698A1EP-4738698-A1

Abstract

An oscillator circuit (100, 300) includes a first cross coupled pair (110, 310), a second cross coupled pair (120, 320), a resonant circuit (130) coupled between the first cross coupled pair (110, 310) and the second cross coupled pair (120, 320) and a first injection circuit (140-1, 340-1). The resonant circuit (130) includes a first node outputting a first voltage signal (VoscP) and a second node outputting a second voltage signal (VoscN). The first injection circuit (140-1, 340-1) is coupled to the first cross coupled pair (110, 310) and injects a first compensating current with a first predetermined phase to a predetermined node of the first cross coupled pair (110, 310).

Inventors

  • CHEN, JIUN-YAN
  • HUNG, CHAO-CHING
  • HSUEH, YU-LI

Assignees

  • MEDIATEK INC.

Dates

Publication Date
20260506
Application Date
20250619

Claims (15)

  1. An oscillator circuit (100, 300), characterized by : a first cross coupled pair (110, 310); a second cross coupled pair (120, 320); a resonant circuit (130), coupled between the first cross coupled pair (110, 310) and the second cross coupled pair (120, 320) and comprising a first node outputting a first voltage signal (VoscP) and a second node outputting a second voltage signal (VoscN); and a first injection circuit (140-1, 340-1), coupled to the first cross coupled pair (110, 310) and injecting a first compensating current with a first predetermined phase to a predetermined node of the first cross coupled pair (110, 310).
  2. The oscillator circuit (100, 300) of claim 1, wherein the first cross coupled pair (110, 310) is characterized by : a first transistor (T11), comprising a first electrode, a second electrode and a third electrode; and a second transistor (T12), comprising a first electrode, a second electrode and a third electrode; wherein the first electrode of the first transistor (T11) is coupled to the second electrode of the second transistor (T12), and the first electrode of the second transistor (T12) is coupled to the second electrode of the first transistor (T11); and wherein the predetermined node is a node connecting to the third electrode of the first transistor (T11).
  3. The oscillator circuit (100, 300) of claim 2, characterized in that the first electrode of the first transistor (T11) is coupled to the first node of the resonant circuit (130) and the first electrode of the second transistor (T12) is coupled to the second node of the resonant circuit (130), and wherein the first voltage signal is provided to the first injection circuit (140-1, 340-1).
  4. The oscillator circuit (100, 300) of any one of claims 2 or 3, wherein the first injection circuit (140-1, 340-1) is characterized by : a filter circuit (210), coupled to the third electrode of the first transistor (T11) and receiving the first voltage signal (VoscP); and a feedthrough circuit (220), coupled to the filter circuit (210) and providing a current path between the third electrode of the first transistor (T11) and a power supply node.
  5. The oscillator circuit (100, 300) of any one of claims 2 to 4, characterized in that the first injection circuit (140-1, 340-1) injects the first compensating current in response to the first voltage signal (VoscP), and the first predetermined phase is a 90-degree phase.
  6. The oscillator circuit (100, 300) of any one of claims 2 to 5, further characterized by : a second injection circuit (140-2, 340-2), coupled to the third electrode of the second transistor (T12) and injecting a second compensating current with a second predetermined phase to the third electrode of the second transistor (T12); wherein the second voltage signal is provided to the second injection circuit (140-2, 340-2) and the second injection circuit (140-2, 340-2) injects the second compensating current in response to the second voltage signal (VoscN).
  7. The oscillator circuit (100, 300) of any one of claims 1 to 6, wherein the second cross coupled pair (120, 320) is characterized by : a third transistor (T13), comprising a first electrode, a second electrode and a third electrode; and a fourth transistor (T14), comprising a first electrode, a second electrode and a third electrode, wherein the first electrode of the third transistor (T13) is coupled to the second electrode of the fourth transistor (T14), and the first electrode of the fourth transistor (T14) is coupled to the second electrode of the third transistor (T13); and the oscillator circuit (100, 300) further comprises: a third injection circuit (140-3, 340-3), coupled to the third electrode of the third transistor (T13) and injecting a third compensating current with a third predetermined phase to the third electrode of the third transistor (T13); and a fourth injection circuit (140-4, 340-4), coupled to the third electrode of the fourth transistor (T14) and injecting a fourth compensating current with a fourth predetermined phase to the third electrode of the fourth transistor (T14); wherein the first voltage signal (VoscP) is provided to the third injection circuit (140-3, 340-3), the third injection circuit (140-3, 340-3) injects the third compensating current in response to the first voltage signal (VoscP), the second voltage signal (VoscN) is provided to the fourth injection circuit (140-4, 340-4) and the fourth injection circuit (140-4, 340-4) injects the fourth compensating current in response to the second voltage signal (VoscN).
  8. An oscillator circuit (100, 300), characterized by : a first cross coupled pair (110, 310); a second cross coupled pair (120, 320); a resonant circuit (130), coupled between the first cross coupled pair (110, 310) and the second cross coupled pair (120, 320) and comprising a first node outputting a first voltage signal (VoscP) and a second node outputting a second voltage signal (VoscN); and a plurality of injection circuits (140-1, 140-2, 140-3, 140-4, 340-1, 340-2, 340-3, 340-4), each being coupled to one of the first cross coupled pair (110, 310) and the second cross coupled pair (120, 320) and injecting a compensating current with a predetermined phase to a predetermined node of the one of the first cross coupled pair (110, 310) and the second cross coupled pair (120, 320); wherein one of the injection circuits (140-1, 140-2, 140-3, 140-4, 340-1, 340-2, 340-3, 340-4) comprises: a filter circuit (210), coupled to the predetermined node of the one of the first cross coupled pair (110, 310) and the second cross coupled pair (120, 320) and receiving one of the first voltage signal (VoscP) and the second voltage signal (VoscN); and a feedthrough circuit (220), coupled to the filter circuit (210) and providing a current path between the predetermined node and a power supply node.
  9. The oscillator circuit (100, 300) of claim 8, wherein the injection circuits are characterized by : a first injection circuit (140-1, 340-1), coupled to the first cross coupled pair (110, 310); a second injection circuit (140-2, 340-2), coupled to the first cross coupled pair (110, 310); a third injection circuit (140-3, 340-3), coupled to the second cross coupled pair (120, 320); and a fourth injection circuit (140-4, 340-4), coupled to the second cross coupled pair (120, 320).
  10. The oscillator circuit (100, 300) of claim 9, wherein the first cross coupled pair (110, 310) is characterized by : a first transistor (T11), comprising a first electrode, a second electrode and a third electrode; and a second transistor (T12), comprising a first electrode, a second electrode and a third electrode; wherein the first electrode of the first transistor (T11) is coupled to the second electrode of the second transistor (T12), and the first electrode of the second transistor (T12) is coupled to the second electrode of the first transistor (T11); and wherein the first injection circuit (140-1, 340-1) is coupled to the third electrode of the first transistor (T11) and the second injection circuit (140-2, 340-2) is coupled to the third electrode of the second transistor (T12).
  11. The oscillator circuit (100, 300) of any one of claims 9 or 10, wherein the second cross coupled pair (120, 320) is characterized by : a third transistor (T13), comprising a first electrode, a second electrode and a third electrode; and a fourth transistor (T14), comprising a first electrode, a second electrode and a third electrode; wherein the first electrode of the third transistor (T13) is coupled to the second electrode of the fourth transistor (T14), and the first electrode of the fourth transistor (T14) is coupled to the second electrode of the third transistor (T13); and wherein the third injection circuit (140-3, 340-3) is coupled to the third electrode of the third transistor (T13) and the fourth injection circuit (140-4, 340-4) is coupled to the third electrode of the fourth transistor (T14).
  12. The oscillator circuit (100, 300) of any one of claims 9 to 11, characterized in that the first voltage signal (VoscP) is provided to the first injection circuit (140-1, 340-1) and the third injection circuit (140-3, 340-3), and the second voltage signal (VoscN) is provided to the second injection circuit (140-2, 340-2) and the fourth injection circuit (140-4, 340-4).
  13. The oscillator circuit (100, 300) of any one of claims 9 to 12, characterized in that the first injection circuit (140-1, 340-1) injects a first compensating current in response to the first voltage signal (VoscP), the second injection circuit (140-2, 340-2) injects a second compensating current in response to the second voltage signal (VoscN), the third injection circuit (140-3, 340-3) injects a third compensating current in response to the first voltage signal (VoscP), and the fourth injection circuit (140-4, 340-4) injects a fourth compensating current in response to the second voltage signal (VoscN).
  14. The oscillator circuit (100, 300) of any one of claims 8 to 13, characterized in that the predetermined phase is a 90-degree phase.
  15. The oscillator circuit (100, 300) of any one of claims 8 to 14, characterized in that there is a 180-degree phase shift between the first voltage signal (VoscP) and the second voltage signal (VoscN).

Description

Field of the Invention This invention relates to an oscillator circuit capable of suppressing flicker noise by phase-shifted self-injection. Background of the Invention Current noise significantly impacts the performance of oscillator circuits, primarily reflected in the degradation of phase noise. When current noise is injected into the oscillator's resonant circuit, the noise signal propagates through the resonant circuit and the oscillator's gain path, affecting the output signal. The injected current noise influences the oscillator's instantaneous phase, leading to phase deviations. The phase deviation of the oscillator is sensitive to the timing of the current noise injection. For the injected current noise with the same magnitude, different phase deviations are generated as the time of injection into the oscillator is different. Impulse Sensitivity Function (ISF) is a mathematical model used to describe the sensitivity of oscillators to external perturbations, particularly in the analysis of phase noise. ISF is represented as Γ(x), which characterizes the oscillator's response to unit impulses at different points within its cycle. The more symmetric the curve of ISF, the better the flicker noise suppression capability of the oscillator circuit. However, due to the nonlinear characteristics of oscillator circuits, ISF curves are often asymmetrical. Therefore, improving the symmetry of the ISF curve to enhance noise suppression capability is an important issue in oscillator circuit design. Summary of the Invention The invention aims at providing an oscillator circuit which can suppress flicker noise by phase-shifted self-injection. This is achieved by oscillator circuits according to claims 1 and 8. The dependent claims pertain to corresponding further developments and improvements. As will be seen more clearly from the detailed description below, the oscillator circuit according to a first embodiment comprises a first cross coupled pair, a second cross coupled pair, a resonant circuit coupled between the first cross coupled pair and the second cross coupled pair and a first injection circuit. The resonant circuit comprises a first node outputting a first voltage signal and a second node outputting a second voltage signal. The first injection circuit is coupled to the first cross coupled pair and injects a first compensating current with a first predetermined phase to a predetermined node of the first cross coupled pair. As will be seen more clearly from the detailed description below, the oscillator circuit according to another embodiment comprises a first cross coupled pair, a second cross coupled pair, a resonant circuit coupled between the first cross coupled pair and the second cross coupled pair and a plurality of injection circuits. The resonant circuit comprises a first node outputting a first voltage signal and a second node outputting a second voltage signal. Each injection circuit is coupled to one of the first cross coupled pair and the second cross coupled pair and injects a compensating current with a predetermined phase to a predetermined node of the one of the first cross coupled pair and the second cross coupled pair. One of the injection circuits comprises a filter circuit and a feedthrough circuit. The filter circuit is coupled to the predetermined node of the one of the first cross coupled pair and the second cross coupled pair and receives one of the first voltage signal and the second voltage signal. The feedthrough circuit is coupled to the filter circuit and provides a current path between the predetermined node and a power supply node. Brief Description of the Drawings In the following, the invention is further illustrated by way of example, taking reference to the following drawings. Thereof: FIG. 1shows a schematic diagram of an oscillator circuit according to an embodiment of the invention.FIG. 2shows an exemplary circuit diagram of an injection circuit according to an embodiment of the invention.FIG. 3shows an exemplary circuit diagram of an oscillator circuit according to a first embodiment of the invention.FIG. 4shows an exemplary circuit diagram of an oscillator circuit according to a second embodiment of the invention.FIG. 5depicts an exemplary circuit diagram of an injection circuit to illustrate the relationship between the drain current and the gate voltage according to an embodiment of the invention.FIG. 6is a schematic diagram showing the generation of symmetric effective ISF which is achieved by injecting the compensating current with a predetermined phase according to an embodiment of the invention.FIG. 7is a schematic diagram showing the phase of the load when looking into the resonant circuit according to an embodiment of the invention. Detailed Description FIG. 1 shows a schematic diagram of an oscillator circuit according to an embodiment of the invention. The oscillator circuit 100 may comprise cross coupled pairs 110 and 120, a resonant circuit 130 and one o