Oscillator circuit

Abstract

An oscillator circuit includes 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 resonance circuit comprises a first node for outputting a first voltage signal and a second node for outputting a second voltage signal. The first injection circuit is coupled to the first cross-coupled pair and injects a first compensation current having a first predetermined phase to a predetermined node of the first cross-coupled pair.

Description

[0001] Cross-references

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 715,681, filed November 4, 2024, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to oscillator circuits, and more particularly, to oscillator circuits that suppress flicker noise through phase-shift self-injection. Background Technology

[0004] Current noise significantly affects the performance of oscillator circuits, primarily through the deterioration of phase noise. When current noise is injected into the resonant circuit of an oscillator, the noise signal propagates through the resonant circuit and the oscillator's gain path, affecting the output signal. The injected current noise affects the instantaneous phase of the oscillator, causing phase deviation. This phase deviation is highly sensitive to the timing of current noise injection. For injected current noise of the same amplitude, different injection times will result in different phase deviations.

[0005] The Impulse Sensitivity Function (ISF) is a mathematical model used to describe the sensitivity of an oscillator to external disturbances, particularly in phase noise analysis. ISF is denoted as Γ(x) and characterizes the oscillator's response to a unit pulse at different points within its period. The more symmetrical the ISF curve, the stronger the flicker noise suppression capability of the oscillator circuit. However, due to the nonlinear characteristics of oscillator circuits, the ISF curve is usually asymmetrical.

[0006] 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

[0007] According to one embodiment of the present invention, an oscillator circuit includes 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 includes a first node that outputs a first voltage signal and a second node that outputs a second voltage signal. The first injection circuit is coupled to the first cross-coupled pair and injects a first compensation current having a first predetermined phase into a predetermined node of the first cross-coupled pair.

[0008] According to another embodiment of the present invention, an oscillator circuit includes 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 includes a first node that outputs a first voltage signal and a second node that outputs 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 compensation current with a predetermined phase into a predetermined node of one of the first cross-coupled pair and the second cross-coupled pair. One of the injection circuits includes a filter circuit and a path circuit. The filter circuit is coupled to the predetermined node of 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 path circuit is coupled to the filter circuit and provides a current path between the predetermined node and a power supply node.

[0009] These, as well as other objectives of the invention, will be self-evident to those skilled in the art upon reading the following detailed description of preferred embodiments, which are illustrated in various figures and drawings. Attached Figure Description

[0010] Figure 1 A schematic diagram of an oscillator circuit according to an embodiment of the present invention is shown.

[0011] Figure 2 An exemplary circuit diagram of an injection circuit according to an embodiment of the present invention is shown.

[0012] Figure 3 An exemplary circuit diagram of an oscillator circuit according to a first embodiment of the present invention is shown.

[0013] Figure 4 An exemplary circuit diagram of an oscillator circuit according to a second embodiment of the present invention is shown.

[0014] Figure 5 An exemplary circuit diagram of an injection circuit according to an embodiment of the present invention is described to illustrate the relationship between drain current and gate voltage.

[0015] Figure 6 This is a schematic diagram illustrating the generation of a symmetrical effective ISF (current injection sensitivity function) by injecting a compensation current with a predetermined phase, according to an embodiment of the present invention.

[0016] Figure 7 This is a schematic diagram showing the phase of the load when observing a resonant circuit according to an embodiment of the present invention. Detailed Implementation

[0017] Figure 1A schematic diagram of an oscillator circuit according to an embodiment of the present invention is shown. The oscillator circuit 100 may include cross-coupled pairs 110 and 120, a resonant circuit 130, and one or more injection circuits, such as injection circuits 140-1, 140-2, 140-3, and 140-4. The resonant circuit 130 is coupled between the cross-coupled pairs 110 and 120 and includes a first node for an output voltage signal VoscP and a second node for an output voltage signal VoscN.

[0018] According to one embodiment of the invention, an injection circuit is coupled to one of the cross-coupled pairs 110 and 120 and injects a compensation current with a predetermined phase into a predetermined node of one of the cross-coupled pairs 110 and 120. In an embodiment of the invention, the predetermined phase is a 90-degree (or close to 90-degree) phase, and the predetermined node is a node connected to the source of a transistor included in one of the cross-coupled pairs 110 and 120.

[0019] More specifically, cross-coupled pair 110 includes transistors T11 and T12, and cross-coupled pair 120 includes transistors T13 and T14. Each transistor T11, T12, T13, and T14 includes a drain (e.g., a first electrode), a gate (e.g., a second electrode), and a source (e.g., a third electrode). The drain of transistor T11 is coupled to the gate of transistor T12, and the drain of transistor T12 is coupled to the gate of transistor T11, forming cross-coupled pair 110. Similarly, the drain of transistor T13 is coupled to the gate of transistor T14, and the drain of transistor T14 is coupled to the gate of transistor T13, forming cross-coupled pair 120.

[0020] Furthermore, the drains of transistors T11 and T13 are coupled to the first node of the resonant circuit 130 for the output voltage signal VoscP, and the drains of transistors T12 and T14 are coupled to the second node of the resonant circuit 130 for the output voltage signal VoscN.

[0021] According to one embodiment of the present invention, there is a 180-degree phase difference between the voltage signal VoscP and the voltage signal VoscN. Furthermore, according to another embodiment of the present invention, the voltage signal VoscP is provided to injection circuits 140-1 and 140-3, and the voltage signal VoscN is provided to injection circuits 140-2 and 140-4.

[0022] According to one embodiment of the invention, injection circuit 140-1 is coupled to the source of transistor T11 (or a first predetermined node of cross-coupled pair 110 connected to the source of transistor T11). Injection circuit 140-1 receives voltage signal VoscP and, in response to voltage signal VoscP, injects a first compensation current having a first predetermined phase into the first predetermined node of cross-coupled pair 110.

[0023] The injection circuit 140-2 is coupled to the source of transistor T12 (or the second predetermined node of cross-coupled pair 110 connected to the source of transistor T12). The injection circuit 140-2 receives a voltage signal VoscN and, in response to the voltage signal VoscN, injects a second compensation current having a second predetermined phase into the second predetermined node of cross-coupled pair 110.

[0024] The injection circuit 140-3 is coupled to the source of transistor T13 (or the first predetermined node of the cross-coupled pair 120 connected to the source of transistor T13). The injection circuit 140-3 receives a voltage signal VoscP and, in response to the voltage signal VoscP, injects a third compensation current having a third predetermined phase into the first predetermined node of the cross-coupled pair 120.

[0025] The injection circuit 140-4 is coupled to the source of transistor T14 (or the second predetermined node of the cross-coupled pair 120 connected to the source of transistor T14). The injection circuit 140-4 receives a voltage signal VoscN and, in response to the voltage signal VoscN, injects a fourth compensation current having a fourth predetermined phase into the second predetermined node of the cross-coupled pair 120.

[0026] According to one embodiment of the present invention, the first compensation current injected into the source of transistor T11 is relative to the gate voltage V of transistor T11. G A current having a 90-degree phase (i.e., a first predetermined phase) or close to a 90-degree phase. That is, in one embodiment of the invention, the injected first compensation current is related to the gate voltage V of transistor T11. G The phase difference between them is 90 degrees or close to 90 degrees.

[0027] The second compensation current injected into the source of transistor T12 is relative to the gate voltage V of transistor T12. G A current having a 90-degree phase (i.e., a second predetermined phase) or close to a 90-degree phase. That is, in one embodiment of the invention, the injected second compensation current is related to the gate voltage V of transistor T12. G The phase difference between them is 90 degrees or close to 90 degrees.

[0028] The third compensation current injected into the source of transistor T13 is relative to the gate voltage V of transistor T13. G A current having a 90-degree phase (i.e., a third predetermined phase) or close to a 90-degree phase. That is, in one embodiment of the invention, the injected third compensation current is related to the gate voltage V of transistor T13. G The phase difference between them is 90 degrees or close to 90 degrees.

[0029] The fourth compensation current injected into the source of transistor T14 is relative to the gate voltage V of transistor T14. G A current having a 90-degree phase (i.e., the fourth predetermined phase) or close to a 90-degree phase. That is, in one embodiment of the invention, the injected fourth compensation current is related to the gate voltage V of transistor T14. G The phase difference between them is 90 degrees or close to 90 degrees.

[0030] According to one embodiment of the invention, each of one or more injection circuits, such as injection circuits 140-1, 140-2, 140-3, and 140-4, includes a filter circuit and a path circuit. The filter circuit may be a high-pass filter or a band-pass filter, and the path circuit may be a DC path circuit coupled to the filter circuit, providing a current path between a predetermined node and a power node of a respective cross-coupled pair, such as a power node providing a power supply voltage VDD or a power node providing a ground voltage GND.

[0031] Figure 2 An exemplary circuit diagram of an injection circuit according to an embodiment of the present invention is shown. The injection circuit 200 may be an implementation of the injection circuit 140-1 and may include a filter circuit 210 and a pass circuit 220.

[0032] Filter circuit 210 is coupled to the source of transistor T21 of the corresponding cross-coupled pair and receives the voltage signal VoscP. Filter circuit 210 performs high-pass or band-pass filtering on the received voltage signal VoscP and provides the filtered voltage signal to the source of transistor T21 of the corresponding cross-coupled pair, contributing to the compensation current injected into the source of transistor T21. Path circuit 220 provides a DC current path to ground voltage GND for the corresponding cross-coupled pair.

[0033] According to one embodiment of the present invention, the injection circuit 200 injects a compensation current having a positive 90-degree phase or substantially a positive 90-degree phase into the source of transistor T21 in response to a voltage signal VoscP. According to one embodiment of the present invention, the injected compensation current is related to the gate voltage V of transistor T21. G The phase difference between them is 90 degrees or close to 90 degrees.

[0034] Note that injection circuits 140-2, 140-3, and 140-4 have similar structures to injection circuit 140-1. Based on Figure 2 The circuit diagrams of injection circuits 140-2, 140-3, and 140-4 can be easily derived by those skilled in the art from the structures shown. Therefore, exemplary circuit diagrams of these injection circuits are omitted here for the sake of brevity.

[0035] Figure 3An exemplary circuit diagram of an oscillator circuit according to a first embodiment of the present invention is shown. The oscillator circuit 300 may include cross-coupled pairs 310 and 320, a resonant circuit coupled between the cross-coupled pairs 310 and 320, and one or more injection circuits, such as injection circuits 340-1, 340-2, 340-3, and 340-4. In this embodiment, the resonant circuit is implemented by an LC oscillation loop 330 and includes a first node for an output voltage signal VoscP and a second node for an output voltage signal VoscN.

[0036] Furthermore, in this embodiment, each injection circuit includes a high-pass filter and a DC-DC path circuit. The high-pass filter can be implemented using a capacitor, such as the capacitor C included in injection circuit 340-1. C The DC path circuit can be implemented using resistors, such as the resistor R included in injection circuit 340-1. S .

[0037] Figure 4 An exemplary circuit diagram of an oscillator circuit according to a second embodiment of the present invention is shown. Each injection circuit includes a high-pass filter and a DC-DC path circuit. Figure 4 The oscillator circuit 400 shown is... Figure 3 The main difference between the oscillator circuits 300 shown is that the high-pass filter is implemented using multiple capacitors, for example... Figure 4 The capacitors C1 and C2 are shown in the diagram.

[0038] According to one embodiment of the present invention, the injection circuit injects a current with a positive 90-degree phase shift into the source of the transistor in the corresponding cross-coupled pair, thereby achieving phase self-injection to change the drain current I of the transistor. D With gate voltage V G The relationship between these factors leads to a symmetrical effective ISF curve for the oscillator circuit.

[0039] Figure 5 An exemplary circuit diagram of an injection circuit is depicted to illustrate the drain current I according to an embodiment of the present invention. D With gate voltage V G The relationship between them. In this embodiment, the gate voltage V P (V) G VoscP is the voltage V. N For VoscN.

[0040] In an embodiment of the present invention, the injected compensation current is related to the gate voltage V of transistor T52. G The phase difference between them is 90 degrees or close to 90 degrees, and the injection of compensation current causes the drain current I of transistor T52 to increase. D With gate voltage VG The phase between them changes. Drain current I D This can be expressed as the following equation, Eq. (1):

[0041] Eq. (1)

[0042] The latter half of the drain current ID ( The injected compensation current contributes to this phase, exhibiting a positive 90-degree phase. This positive 90-degree phase is due to the capacitors (e.g., capacitor CC) included in the injection circuit. This positive 90-degree phase alters the phase of the current noise, resulting in a phase difference between the drain current ID and the gate voltage VG. ,like Figure 5 As shown.

[0043] In an embodiment of the present invention, the phase of the current noise is changed by injecting compensation current as described above. The purpose of changing the phase of the current noise is to make the effective ISF curve of the oscillator circuit symmetrical.

[0044] Figure 6 This is a schematic diagram illustrating the generation of a symmetrical effective ISF by injecting a compensation current with a predetermined phase according to an embodiment of the invention.

[0045] Since current noise is actually time-varying, considering the cyclic steady-state current noise... Valid ISF It is used as a measure of flicker noise suppression capability and is expressed by the following equation Eq. (2):

[0046] Eq. (2)

[0047] The parameter x represents a point in time.

[0048] exist Figure 6 In the image, the left side shows the waveform of asymmetric current noise with phase injection (generated in the proposed oscillator circuit with phase self-injection), the middle shows the waveform of asymmetric ISF, and the right side shows the waveform of the resulting valid ISF.

[0049] In embodiments of the invention, the asymmetric waveform of the ISF is compensated by current noise with phase injection by controlling the predetermined phase of the injected compensation current. For example, in the ISF curve, the amplitude at point a is smaller than the amplitude at point b. To compensate for this, a compensation current with a positive 90-degree phase lead is injected into the source of the corresponding transistor to change the phase of the current noise, such that the amplitude at point a is greater than the amplitude at point b. After the combination of current noise and ISF as expressed in Eq. (2), the waveform of the resulting effective ISF is symmetrical. Therefore, the flicker noise suppression capability is greatly improved for the proposed oscillator circuit with phase self-injection.

[0050] According to one embodiment of the present invention, the phase of the current noise is:

[0051] Eq. (3)

[0052] (For example, but not limited to, such as) Figure 3 The capacitor C shown C capacitors or such Figure 4 The capacitances of capacitors C1 and C2 shown are flexibly adjusted based on the asymmetry of the ISF curve.

[0053] Please note that since only resistors and capacitors are required in the injection circuit, the circuit area occupied by the injection circuit is very small. In particular, compared with conventional designs using second harmonic tail energy storage devices that include inductors, the circuit area required by the proposed oscillator to compensate for ISF asymmetry is significantly reduced. Furthermore, the proposed oscillator circuit not only has good flicker noise suppression capabilities but also supports wideband operation. Therefore, a second harmonic tuning circuit is not required compared to conventional designs.

[0054] Figure 7 This is a schematic diagram illustrating the phase of the load when viewing a resonant circuit according to an embodiment of the present invention, where n is a positive integer greater than 1. For viewing the load of the resonant circuit, please refer to... Figure 1 , where the load impedance Zload CM The two arrows indicate the path of the common-mode current flow, relative to the load impedance Zload. DM The two arrows indicate the path of the differential mode current flow.

[0055] like Figure 7 As shown, at a frequency of 2nf a and 2nf b Between and frequency (2n+1)f a and (2n+1)f b In the capacitive load region between, the phase ∠Zload is described. CM The slope of the curve and the description of phase ∠ZloadDM The slopes of the curves are very small and close to 0. This proves that the ISF does not change with the oscillation frequency of the oscillator, and that the proposed oscillator circuit supports wideband operation. That is, the flicker noise suppression capability does not decrease even when the oscillation frequency of the oscillator circuit changes. This is for illustrative purposes only, and the invention is not limited thereto. Any load that does not change significantly with frequency (i.e., a load with a gentle slope) is within the scope of this invention.

[0056] In summary, this invention presents an oscillator circuit for flicker noise suppression via phase-shift self-injection. The proposed oscillator circuit not only exhibits excellent flicker noise suppression capabilities but also supports wideband operation. Furthermore, since only resistors and capacitors are required in the injection circuit, the circuit area occupied by the injection circuit is very small. Compared to conventional designs, no second harmonic tail energy storage device or additional tuning circuitry or tuning mechanism is needed. Therefore, compared to conventional designs, the proposed oscillator requires a significantly reduced circuit area to compensate for ISF asymmetry.

[0057] Those skilled in the art will readily observe that many modifications and alterations can be made to the apparatus and method while retaining the teachings of the present invention. Therefore, the foregoing disclosure should be limited only by the scope of the appended claims.

Claims

1. An oscillator circuit, comprising: First cross-coupled pair; Second cross-coupling pair; A resonant circuit, coupled between the first cross-coupled pair and the second cross-coupled pair, includes a first node that outputs a first voltage signal and a second node that outputs a second voltage signal; as well as A first injection circuit is coupled to the first cross-coupled pair and injects a first compensation current having a first predetermined phase into a predetermined node of the first cross-coupled pair.

2. The oscillator circuit of claim 1, wherein the first cross-coupled pair comprises: The first transistor includes a first electrode, a second electrode, and a third electrode; as well as The second transistor includes a first electrode, a second electrode, and a third electrode. The first electrode of the first transistor is coupled to the second electrode of the second transistor, and the first electrode of the second transistor is coupled to the second electrode of the first transistor. The predetermined node is the node connected to the third electrode of the first transistor.

3. The oscillator circuit of claim 2, wherein the first electrode of the first transistor is coupled to the first node of the resonant circuit, and the first electrode of the second transistor is coupled to the second node of the resonant circuit, wherein the first voltage signal is provided to the first injection circuit.

4. The oscillator circuit of claim 2, wherein the first injection circuit comprises: A filter circuit is coupled to the third electrode of the first transistor and receives the first voltage signal. as well as The circuit path is coupled to the filter circuit and provides a current path between the third electrode of the first transistor and the power node.

5. The oscillator circuit of claim 2, wherein the first injection circuit injects the first compensation current in response to the first voltage signal, and the first predetermined phase is a 90-degree phase.

6. The oscillator circuit of claim 2, further comprising: A second injection circuit is coupled to the third electrode of the second transistor and injects a second compensation current having a second predetermined phase into the third electrode of the second transistor.

7. The oscillator circuit of claim 6, wherein the second injection circuit provides the second voltage signal, and the second injection circuit injects the second compensation current in response to the second voltage signal.

8. The oscillator circuit of claim 1, wherein the second cross-coupled pair comprises: The third transistor includes a first electrode, a second electrode, and a third electrode; as well as A fourth transistor includes a first electrode, a second electrode, and a third electrode, wherein the first electrode of the third transistor is coupled to the second electrode of the fourth transistor, and the first electrode of the fourth transistor is coupled to the second electrode of the third transistor.

9. The oscillator circuit of claim 8, further comprising: A third injection circuit is coupled to the third electrode of the third transistor and injects a third compensation current having a third predetermined phase into the third electrode of the third transistor.

10. The oscillator circuit of claim 9, wherein the third injection circuit provides the first voltage signal, and the third injection circuit injects the third compensation current in response to the first voltage signal.

11. The oscillator circuit of claim 8, further comprising: A fourth injection circuit is coupled to the third electrode of the fourth transistor and injects a fourth compensation current having a fourth predetermined phase into the third electrode of the fourth transistor.

12. The oscillator circuit of claim 11, wherein the fourth injection circuit provides the second voltage signal, and the fourth injection circuit injects the fourth compensation current in response to the second voltage signal.

13. An oscillator circuit, comprising: First cross-coupled pair; Second cross-coupling pair; A resonant circuit, coupled between the first cross-coupled pair and the second cross-coupled pair, includes a first node that outputs a first voltage signal and a second node that outputs a second voltage signal; as well as Multiple injection circuits, each coupled to one of the first cross-coupled pair and the second cross-coupled pair, inject a compensation current with a predetermined phase into a predetermined node of one of the first cross-coupled pair and the second cross-coupled pair. One of the injection circuits mentioned above includes: A filter circuit is coupled to a predetermined node of 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; as well as The circuit path is coupled to the filter circuit and provides a current path between the predetermined node and the power supply node.

14. The oscillator circuit of claim 13, wherein the injection circuit comprises: A first injection circuit is coupled to the first cross-coupled pair; The second injection circuit is coupled to the first cross-coupled pair; The third injection circuit is coupled to the second cross-coupled pair; as well as The fourth injection circuit is coupled to the second cross-coupled pair.

15. The oscillator circuit of claim 14, wherein the first cross-coupling pair comprises: A first transistor includes a first electrode, a second electrode, and a third electrode; And a second transistor, including a first electrode, a second electrode and a third electrode, wherein the first electrode of the first transistor is coupled to the second electrode of the second transistor, the first electrode of the second transistor is coupled to the second electrode of the first transistor, and a first injection circuit is coupled to the third electrode of the first transistor, and a second injection circuit is coupled to the third electrode of the second transistor.

16. The oscillator circuit of claim 14, wherein the second cross-coupling pair comprises: A third transistor includes a first electrode, a second electrode, and a third electrode; And a fourth transistor, including a first electrode, a second electrode and a third electrode, wherein the first electrode of the third transistor is coupled to the second electrode of the fourth transistor, the first electrode of the fourth transistor is coupled to the second electrode of the third transistor, and a third injection circuit is coupled to the third electrode of the third transistor, and a fourth injection circuit is coupled to the third electrode of the fourth transistor.

17. The oscillator circuit of claim 14, wherein a first voltage signal is provided to a first injection circuit and a third injection circuit, and a second voltage signal is provided to a second injection circuit and a fourth injection circuit.

18. The oscillator circuit of claim 14, wherein the first injection circuit injects a first compensation current in response to a first voltage signal, the second injection circuit injects a second compensation current in response to a second voltage signal, the third injection circuit injects a third compensation current in response to the first voltage signal, and the fourth injection circuit injects a fourth compensation current in response to the second voltage signal.

19. The oscillator circuit of claim 13, wherein the predetermined phase is a 90-degree phase.

20. The oscillator circuit of claim 13, wherein there is a 180-degree phase difference between the first voltage signal and the second voltage signal.

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