A multiphase oscillator capable of generating arbitrary phases

Abstract

This invention discloses a multiphase oscillator capable of generating arbitrary phases, comprising multiple orthogonal oscillators with no phase mode ambiguity. These orthogonal oscillators are arranged sequentially and maintain a consistent phase mode during operation. Any two adjacent orthogonal oscillators are coupled together via a phase-shift coupling network to generate a phase difference. This invention ensures deterministic output phase during application, while also exhibiting a small area and low phase noise.

Description

Technical Field

[0001] This invention relates to integrated circuit design technology, specifically a multiphase oscillator capable of generating arbitrary phases. Background Technology

[0002] An oscillator is a device that converts DC to AC signal output without external excitation. Oscillators possess positive feedback and a certain gain to overcome losses in the circuit feedback path, thus generating a self-sustaining and stable oscillation signal. Voltage-controlled oscillators (VCOs), as a major type of oscillator, are used in modules such as phase-locked loops (PLLs) and clock recovery circuits, and are one of the core modules of wireless communication systems. Figure 1 As shown in (a), commonly used voltage-controlled oscillators (VCOs) include an active circuit and an LCR resonant circuit. The upper resonant circuit relies on the resonance of capacitor C and inductor L, with R being the equivalent resistance, used to characterize the energy loss during resonance. The negative resistance -R generated by the lower active circuit cancels out the resistance generated by the resonant circuit, supplementing the energy loss in the resonant circuit. Therefore, when the VCO oscillates stably, it achieves... Figure 1 The stable output at the f0 resonant point shown in (b) has an oscillation frequency that can be calculated as follows:

[0003] Typically, the clock signal output by an oscillator is a differential signal, meaning it has two phases with a phase difference of 180°. When the number of output phases is greater than two, i.e., the phase difference between adjacent clock signals is less than 180°, it can be called a multiphase clock signal, such as... Figure 2 This demonstrates the waveform relationship between a conventional differential clock signal (two-phase) and a fully quadrature clock signal (four-phase). Figure 2 (a) is the waveform of the differential clock signal. Figure 2 (b) is the waveform of a fully quadrature clock signal. Multiphase output oscillators are widely used in many key RF modules such as subharmonic mixers, analog-to-digital converters (ADCs), and clock data recovery (CDR). Coupled LC oscillators or traveling-wave oscillators are commonly used to generate multiphase outputs.

[0004] The aforementioned multiphase signals are clock signals with fixed phase differences. In some applications, clock signals with variable phase differences (phase shifting) are also required, such as in phased array systems using LO phase shifting. The multiphase-shiftable clock in this system is generated by cascading a clock source and a phase shifter. If the multiphase-shiftable clock signal could be directly generated at the oscillator, it would undoubtedly simplify the design of the LO phase-shifted phased array and improve the overall system performance.

[0005] Currently, to obtain clock signals with variable phase difference (phase shift), existing multiphase oscillators mainly employ two methods: coupled LC oscillators and traveling wave oscillators. A schematic diagram of a coupled LC oscillator is shown below. Figure 3As shown. N LC oscillators are coupled into a loop, and the output of each oscillator has a different phase. The multi-phase output generated by this method has the following advantages: (1) the number of output phases can be increased by expanding the number of coupled oscillator cores; (2) phase noise can be optimized due to the number of coupled oscillators. Ideally, N-core coupling can achieve 10logN dB of phase noise suppression. However, using coupled LC oscillators requires additional coupling circuits and on-chip interconnects. This oscillator occupies a large chip area and can only generate multi-phase signals with a fixed phase difference. In addition, the magnitude relationship between the multiple phases generated by this circuit is uncertain, such as Figure 3 There exists in to and by to The existence of two phase modes, i.e., mode ambiguity, can lead to uncertainty in phase output.

[0006] A schematic diagram of a traveling wave oscillator is shown below. Figure 4 As shown, four pairs of active circuits provide negative resistance for the oscillation and are evenly distributed along the loop formed by the differential transmission lines. Each pair of active circuits generates a standing wave with a different phase, which superimposes throughout the loop to form a traveling wave. Therefore, the entire oscillation loop will produce phases of equal amplitude and phases ranging from 0° to 360°. This method produces an unlimited number of phases and has a smaller overall area compared to coupled LC oscillators. However, while traveling wave oscillators can easily generate a large number of phase signals, the phase difference between these signals remains fixed; furthermore, mode ambiguity remains a problem in traveling wave oscillators. Summary of the Invention

[0007] The purpose of this invention is to solve the problems that existing multiphase oscillators can only generate multiphase signals with fixed phase differences and have mode ambiguity. It provides a multiphase oscillator that can generate arbitrary phases, which can achieve 360° mode-ambiguous arbitrary phase output, can guarantee the determinism of the output phase, and has a small area and low phase noise.

[0008] The objective of this invention is mainly achieved through the following technical solutions:

[0009] A multiphase oscillator capable of generating arbitrary phases includes multiple orthogonal oscillators without phase mode ambiguity. These orthogonal oscillators are arranged sequentially and maintain a consistent phase mode during operation. Any two adjacent orthogonal oscillators are coupled together via a phase-shift coupling network to generate a phase difference. The invention consists of multiple sequentially arranged orthogonal oscillators and a phase-shift coupling network for coupling adjacent orthogonal oscillators and generating a phase difference. The orthogonal oscillators and the phase-shift coupling network are alternately placed, with each orthogonal oscillator acting as a clock channel to generate one orthogonal clock signal. All orthogonal oscillator units operate in a single-phase mode (i.e., without mode ambiguity). By configuring the phase-shift coupling network, a phase difference θ exists between the outputs of two adjacent orthogonal oscillators, which can cover a range from 0 to 360°, thus generating arbitrary phases.

[0010] Furthermore, the phase-shift coupling network has four coupling channels, which correspond to coupling channels with phase differences of 0°, 90°, 180°, and 270°, respectively. The phase-shift coupling network controls the phase difference between two adjacent quadrature oscillators by controlling the opening and closing of the four coupling channels and the coupling strength of each coupling channel.

[0011] Furthermore, the four coupling channels are coupling channel I, coupling channel II, coupling channel III, and coupling channel IV, and the phase differences between coupling channel I, coupling channel II, coupling channel III, and coupling channel IV are 0°, 90°, 180°, and 270°, respectively; wherein:

[0012] When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 0° and 45°, coupling channel I and coupling channel II are turned on, coupling channel III and coupling channel IV are turned off, and the coupling strength of coupling channel I is greater than that of coupling channel II.

[0013] When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 45° and 90°, coupling channel I and coupling channel II are turned on, coupling channel III and coupling channel IV are turned off, and the coupling strength of coupling channel I is less than the coupling strength of coupling channel II.

[0014] When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 90° and 135°, coupling channel II and coupling channel III are turned on, coupling channel I and coupling channel IV are turned off, and the coupling strength of coupling channel II is greater than that of coupling channel III.

[0015] When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 135° and 180°, coupling channel II and coupling channel III are turned on, coupling channel I and coupling channel IV are turned off, and the coupling strength of coupling channel II is less than the coupling strength of coupling channel III.

[0016] When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 180° and 225°, coupling channel III and coupling channel IV are turned on, coupling channel I and coupling channel II are turned off, and the coupling strength of coupling channel III is greater than that of coupling channel IV.

[0017] When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 225° and 270°, coupling channel III and coupling channel IV are turned on, coupling channel I and coupling channel II are turned off, and the coupling strength of coupling channel III is less than the coupling strength of coupling channel IV.

[0018] When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 270° and 315°, coupling channel I and coupling channel IV are turned on, coupling channel II and coupling channel III are turned off, and the coupling strength of coupling channel IV is greater than that of coupling channel I.

[0019] When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 315° and 360°, coupling channel I and coupling channel IV are turned on, coupling channel II and coupling channel III are turned off, and the coupling strength of coupling channel IV is less than the coupling strength of coupling channel I.

[0020] Furthermore, each of the coupling channels is implemented using any one of capacitive coupling, resistive coupling, inductive coupling, and transistor coupling, or a combination of two or more coupling methods.

[0021] Furthermore, the quadrature oscillator includes an active circuit and a resonant circuit, wherein the active circuit is implemented using a cross-coupled NMOS active circuit, a cross-coupled PMOS active circuit, a cross-coupled CMOS active circuit, or a cross-coupled transistor active circuit.

[0022] Furthermore, the phase differences of the multiple quadrature oscillators increase sequentially at equal arithmetic steps.

[0023] Furthermore, the quadrature oscillator has four output nodes: I+, Q+, I-, and Q-. The phase difference between any two adjacent quadrature oscillators is the phase difference of the signals output at the same node.

[0024] In summary, compared with existing technologies, this invention has the following advantages: Traditional multiphase oscillators generate a fixed phase, while this invention, by introducing a phase-shift coupling network to adjust the coupling relationship between two adjacent quadrature oscillators, can achieve the generation of any phase over 360°. The quadrature oscillators of this invention employ phase-mode-ambiguity-free quadrature oscillators, ensuring both phase determinism and improved phase noise performance. This invention simultaneously achieves 360° mode-ambiguity-free arbitrary phase output, a smaller area, and lower phase noise. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0026] Figure 1 A schematic diagram of an existing voltage-controlled oscillator and its resonant point;

[0027] Figure 2 This is a schematic diagram showing the waveform relationship between the differential clock signal and the fully quadrature clock signal of a conventional oscillator.

[0028] Figure 3 This is a schematic diagram of a coupled LC oscillator;

[0029] Figure 4 This is a schematic diagram of a traveling wave oscillator;

[0030] Figure 5 This is a schematic diagram of a specific embodiment of the present invention;

[0031] Figure 6 A schematic diagram showing a specific embodiment of the present invention with two orthogonal oscillators;

[0032] Figure 7 A schematic diagram for achieving phase-mode ambiguity in a quadrature oscillator;

[0033] Figure 8 This is a schematic diagram illustrating the configuration of an arbitrary phase and phase shift coupled network.

[0034] Figure 9 This is a schematic diagram of the active circuit implementation of the quadrature oscillator in a specific embodiment of the present invention;

[0035] Figure 10 This is a schematic diagram of the phase-shift coupling network implementation in a specific embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0037] Example:

[0038] like Figure 5 As shown, a multiphase oscillator capable of generating arbitrary phases includes multiple orthogonal oscillators with no phase mode ambiguity. These orthogonal oscillators are arranged sequentially, and all oscillators maintain a consistent phase mode during operation. Any two adjacent orthogonal oscillators are coupled together via a phase-shift coupling network, generating a phase difference. In this embodiment, the phase differences of the multiple orthogonal oscillators increase sequentially at equal arithmetic steps. It is important to note that to ensure the final generated phase is deterministic and controllable, all orthogonal oscillators in this embodiment must operate in a defined and consistent phase mode.

[0039] To demonstrate the principle of arbitrary phase generation, such as Figure 6 As shown ( Figure 6 Only two quadrature oscillators are configured. Each quadrature oscillator unit can support quadrature clock signal output. The quadrature oscillator has four output nodes: I+, Q+, I-, and Q-. This is the fixed polyphase signal section. The phase difference θ between any two adjacent quadrature oscillator units is defined as the phase difference of the signals output at the same node. Figure 6 The phase difference θ shown is the phase difference between the output signals of quadrature oscillators 1 and 2 at the I+ node. This phase difference θ is adjustable. The magnitude of θ can be configured through a phase-shift coupling network, fully covering any value from 0 to 360°. Similarly, Figure 6 There is a phase difference θ between the Q+ node of quadrature oscillator 1 and the Q+ node of quadrature oscillator 2, between the I- node of quadrature oscillator 1 and the I- node of quadrature oscillator 2, and between the Q- node of quadrature oscillator 1 and the Q- node of quadrature oscillator 2.

[0040] The phase-mode ambiguous quadrature oscillator used in this embodiment is implemented based on existing technology, and its implementation principle is as follows: Figure 7 As shown, Figure 7 China | Z 01 / 02 The two points on the curve represent the quadrature oscillator exhibiting mode ambiguity, operating in phase mode one and mode two respectively. Both have the same impedance and show no significant difference. The specific implementation of a quadrature oscillator without phase mode ambiguity involves lowering and raising the quality factors (Q values) of phase mode one and phase mode two respectively. Thus, when the quadrature oscillator is operating, the low-Q phase mode one is suppressed, while the high-Q phase mode two is retained, achieving the goal of a quadrature oscillator without phase mode ambiguity.

[0041] The phase-shift coupling network in this embodiment has four coupling channels, corresponding to phase differences of 0°, 90°, 180°, and 270°, respectively. The phase-shift coupling network controls the phase difference between two adjacent quadrature oscillators by controlling the opening and closing of the four coupling channels and the coupling strength of each channel. The coupling strength of each coupling channel is configurable; by configuring the combinations of these coupling channel strengths, a phase difference θ of any angle can be vector-synthesized. To further demonstrate the generation process of the phase difference θ, Figure 8The configuration of the θ-phase-shift coupling network is shown. In this embodiment, the four coupling channels are coupling channel I, coupling channel II, coupling channel III, and coupling channel IV, with phase differences of 0°, 90°, 180°, and 270° corresponding to coupling channels I, II, III, and IV, respectively. In this embodiment, when the phase difference between two adjacent quadrature oscillators needs to be controlled between 0° and 45°, coupling channels I and II are activated, while coupling channels III and IV are deactivated, and the coupling strength of coupling channel I is greater than that of coupling channel II. When the phase difference between two adjacent quadrature oscillators needs to be controlled between 45° and 90°, coupling channels I and II are activated, while coupling channels III and IV are deactivated, and the coupling strength of coupling channel I is less than that of coupling channel II. When the phase difference between two adjacent quadrature oscillators needs to be controlled between 90° and 135°, coupling channels II and III are activated, while coupling channels I and IV are deactivated, and the coupling strength of coupling channel II is greater than that of coupling channel III. When the phase difference between two adjacent quadrature oscillators needs to be controlled between 135° and 180°, coupling channels II and III are activated, while coupling channels I and IV are deactivated, and the coupling strength of coupling channel II is less than that of coupling channel III. The coupling strength varies depending on the phase difference between adjacent quadrature oscillators. When the phase difference needs to be controlled between 180° and 225°, coupling channels III and IV are activated, while coupling channels I and II are deactivated, and the coupling strength of coupling channel III is greater than that of coupling channel IV. When the phase difference needs to be controlled between 225° and 270°, coupling channels III and IV are activated, while coupling channels I and II are deactivated, and the coupling strength of coupling channel III is less than that of coupling channel IV. When the phase difference needs to be controlled between 270° and 315°, coupling channels I and IV are activated, while coupling channels II and III are deactivated, and the coupling strength of coupling channel IV is greater than that of coupling channel I. When the phase difference needs to be controlled between 315° and 360°, coupling channels I and IV are activated, while coupling channels II and III are deactivated, and the coupling strength of coupling channel IV is less than that of coupling channel I.

[0042] like Figure 9As shown, the quadrature oscillator in this embodiment includes an active circuit and a resonant circuit. The active circuit providing negative resistance in the quadrature oscillator is implemented using a cross-coupled NMOS active circuit, a cross-coupled PMOS active circuit, a cross-coupled CMOS active circuit, or a cross-coupled transistor active circuit. Different active circuits have different phase noise and power consumption characteristics, and can be selected according to the performance requirements.

[0043] The configurable phase-shift coupling network in this embodiment is used to couple two adjacent quadrature oscillators and generate arbitrary phases, such as... Figure 10 As shown, each coupling channel in this phase-shift coupling network employs any one of the following coupling methods, or a combination of two or more: capacitive coupling, resistive coupling, inductive coupling, and transistor coupling. When the phase-shift coupling network in this embodiment uses capacitive coupling, the coupling strength is adjusted by changing the equivalent capacitance value; when it uses resistive coupling, the coupling strength is adjusted by changing the equivalent resistance value; when it uses inductive coupling, the coupling strength is adjusted by changing the inductance coefficient; and when it uses transistor coupling, the coupling strength is adjusted by changing the transistor input voltage. In this embodiment, the coupling channel is closed when the coupling strength is zero. Different coupling methods have different areas, noise levels, etc., and a compromise is made based on actual needs.

[0044] The multiphase oscillator proposed in this embodiment achieves arbitrary phase output from multiple oscillators while supporting the generation of quadrature signals for each channel. By configuring a phase-shift coupling network for coupling two adjacent quadrature oscillator units, arbitrary phases can be synthesized between two adjacent quadrature oscillators. This embodiment has definite phase information, which can overcome the phase mode ambiguity problem existing in most traditional schemes.

[0045] Table 1 shows a performance comparison between this embodiment and a traditional multiphase oscillator:

[0046] Table 1. Performance comparison of this invention with conventional oscillators

[0047]

[0048] As shown in Table 1, this embodiment achieves arbitrary phase (phase shift) while still maintaining excellent phase accuracy and area advantages. In practical applications, by arranging multiple clock channels and completing phase generation, this scheme can serve as a potential clock / phase shifting solution for 5G / 6G phased arrays.

[0049] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multiphase oscillator capable of generating arbitrary phases, characterized in that, It includes multiple orthogonal oscillators without phase mode ambiguity. The multiple orthogonal oscillators are arranged in sequence and maintain the same phase mode when they are working. Any two adjacent orthogonal oscillators are coupled and connected through a phase shift coupling network to generate a phase difference. The phase-shift coupling network has four coupling channels, which correspond to the coupling channels with phase differences of 0°, 90°, 180° and 270° respectively. The phase-shift coupling network controls the phase difference between two adjacent quadrature oscillators by controlling the opening and closing of the four coupling channels and the coupling strength of each coupling channel. The four coupling channels are coupling channel I, coupling channel II, coupling channel III, and coupling channel IV, with phase differences of 0°, 90°, 180°, and 270° respectively. When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 0° and 45°, coupling channel I and coupling channel II are turned on, coupling channel III and coupling channel IV are turned off, and the coupling strength of coupling channel I is greater than that of coupling channel II. When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 45° and 90°, coupling channel I and coupling channel II are turned on, coupling channel III and coupling channel IV are turned off, and the coupling strength of coupling channel I is less than the coupling strength of coupling channel II. When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 90° and 135°, coupling channel II and coupling channel III are turned on, coupling channel I and coupling channel IV are turned off, and the coupling strength of coupling channel II is greater than that of coupling channel III. When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 135° and 180°, coupling channel II and coupling channel III are turned on, coupling channel I and coupling channel IV are turned off, and the coupling strength of coupling channel II is less than the coupling strength of coupling channel III. When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 180° and 225°, coupling channel III and coupling channel IV are turned on, coupling channel I and coupling channel II are turned off, and the coupling strength of coupling channel III is greater than that of coupling channel IV. When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 225° and 270°, coupling channel III and coupling channel IV are turned on, coupling channel I and coupling channel II are turned off, and the coupling strength of coupling channel III is less than the coupling strength of coupling channel IV. When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 270° and 315°, coupling channel I and coupling channel IV are turned on, coupling channel II and coupling channel III are turned off, and the coupling strength of coupling channel IV is greater than that of coupling channel I. When it is necessary to control the phase difference between two adjacent quadrature oscillators to be between 315° and 360°, coupling channel I and coupling channel IV are turned on, coupling channel II and coupling channel III are turned off, and the coupling strength of coupling channel IV is less than the coupling strength of coupling channel I.

2. A multiphase oscillator capable of generating arbitrary phases according to claim 1, characterized in that, Each of the aforementioned coupling channels is implemented using any one of the following coupling methods: capacitive coupling, resistive coupling, inductive coupling, and transistor coupling, or a combination of two or more coupling methods.

3. A multiphase oscillator capable of generating arbitrary phases according to claim 1, characterized in that, The quadrature oscillator includes an active circuit and a resonant circuit. The active circuit is implemented using a cross-coupled NMOS active circuit, a cross-coupled PMOS active circuit, a cross-coupled CMOS active circuit, or a cross-coupled transistor active circuit.

4. A multiphase oscillator capable of generating arbitrary phases according to claim 1, characterized in that, The phase differences of the multiple quadrature oscillators increase sequentially at equal arithmetic steps.

5. A multiphase oscillator capable of generating arbitrary phases according to any one of claims 1 to 4, characterized in that, The quadrature oscillator has four output nodes: I+, Q+, I-, and Q-. The phase difference between any two adjacent quadrature oscillators is the phase difference of the signals output at the same node.

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