Injection locked oscillator

Abstract

An electronic oscillator circuit includes: a resonant circuit including an inductor and a capacitor, where each of the inductor and the capacitor has a first terminal connected to a first side of the resonant circuit and a second terminal connected to a second side of the resonant circuit; a first current controller; and a second current controller; wherein the first current controller is connected to a first side of the resonant circuit; wherein the second current controller is connected to a second side of the resonant circuit; wherein the first current controller is arranged to enable it to act as a current source of the resonant circuit; wherein the second current controller is arranged to enable it to act as a current tank of the resonant circuit; wherein the first current controller and the second current controller are configured such that the injection current flows from the first current controller to the second current controller through the resonant circuit when the first current controller and the second current controller are in a first state; and when the first current controller and the second current controller are in the second state, no current is injected into the resonant circuit. The current injected in this manner allows energy to be injected into the resonant circuit, which forces oscillation in the resonant circuit to proceed at a predetermined frequency different from the natural resonant frequency of the resonant circuit.

Description

Background Art

[0001] The present invention relates to electronic oscillators, and more particularly to injection locked oscillators for generating periodic signals in CMOS circuits.

[0002] The traditional method of generating and locking a periodic signal is to use a phase-locked loop (PLL). However, the locking time of a phase-locked loop is very long (microseconds) and cannot provide a "locked" signal with a response time in the nanosecond and / or sub-nanosecond range.

[0003] The present invention aims to provide an electronic oscillator with a fast response rate (i.e., the ability to start oscillation and lock to a reference / injection pulse in the nanosecond range) and low power requirements. Such a reference-locked signal can be used to generate ultra-wideband transmit pulses or to provide a clock for an analog-to-digital converter (ADC). Summary of the invention

[0004] From a first aspect, the present invention provides an electronic oscillator circuit, comprising:

[0005] a resonant circuit including an inductor and a capacitor, wherein each of the inductor and the capacitor has a first terminal connected to a first side of the oscillating circuit and a second terminal connected to a second side of the resonant circuit;

[0006] a first current controller; and

[0007] a second current controller;

[0008] wherein a first current controller is connected to a first side of the resonant circuit;

[0009] wherein the second current controller is connected to the second side of the resonant circuit;

[0010] wherein the first current controller is arranged so that it can act as a current source for the resonant circuit;

[0011] wherein the second current controller is arranged so that it can act as a current sink of the resonant circuit;

[0012] wherein the first current controller and the second current controller are configured such that when the first current controller and the second current controller are in a first state, the injection current flows from the first current controller to the second current controller through the resonant circuit; and

[0013] When the first current controller and the second current controller are in the second state, no current is injected into the resonant circuit.

[0014] It can be seen that according to the present disclosure, an electronic oscillator circuit is provided, including a first current control and a second current controller connected to a resonant circuit, which are configured to inject current through the resonant circuit. Injecting current in this manner allows energy to be injected into the oscillation circuit, and if operated properly, the resonant circuit can be forced to oscillate at a predetermined frequency different from the natural resonant frequency of the resonant circuit. Therefore, when no injection signal is applied, the resonant circuit oscillates at its natural resonant frequency (determined by the size of the inductor and the capacitor), and when the injection frequency of the injected current is close to the natural resonant frequency of the resonant circuit (or has an Nth harmonic component close to the natural resonant frequency of the resonant circuit), the frequency of the oscillation signal in the resonant circuit is "pulled" to the injection frequency (or its Nth harmonic component).

[0015] The injection frequency may be selected to be as close to the resonant frequency as possible (or to have an Nth harmonic component as close to the resonant frequency as possible) so as to reduce the presence of signals at frequencies other than the injection frequency or its Nth harmonic (i.e., the frequency to which the resonant circuit is locked). Specifically, to ensure spectral compliance, the injection frequency may be selected so that the amplitude of "sideband spurs" close to the injection signal frequency is less than 30 dB. This may enable the electronic oscillator circuit to be used as part of a transmitter. In particular, it may be suitable for transmitters that require a certain degree of spectral compliance, such as some UWB transmissions.

[0016] In some examples, the first current controller and the second current controller may be switches. However, in some examples, the first current controller and the second current controller may be amplifiers. In some preferred examples, the first current controller and the second current controller may be transistors. In some such examples, the first current controller may be a PMOS transistor and the second current controller may be an NMOS transistor.

[0017] The electronic oscillator circuit may include one or more oscillation maintaining elements or circuits to offset the losses caused by the inherent impedance in the resonant circuit. In some examples, the electronic oscillator circuit may include one or more negative impedance elements to overcome the inherent impedance of the resonant circuit, thereby maintaining the oscillations in the resonant circuit, otherwise these oscillations will be suppressed due to resistance losses. Therefore, the role of this negative impedance element is to promote the oscillations in the resonant circuit so that the oscillations are maintained, rather than being suppressed due to negative impedance. The negative impedance element may take the form of one or more negative impedance circuits. In some such examples, the negative impedance element may include one or more cross-coupling pairs of circuits. Therefore, in some examples, the electronic oscillator circuit includes a first cross-coupling pair of circuits connected to the resonant circuit. The cross-coupling pair of circuits may be connected upstream of the resonant circuit. This cross-coupling pair of circuits may include a cross-coupled PMOS transistor pair, the source of each PMOS transistor being connected to a power supply rail or other current supply. The gate of the first PMOS transistor of the cross-coupled PMOS transistor pair may be connected to the drain of the second PMOS transistor of the cross-coupled PMOS transistor pair, and the gate of the second PMOS transistor of the cross-coupled PMOS transistor pair may be connected to the drain of the first PMOS transistor of the cross-coupled PMOS transistor pair.

[0018] In some examples, the electronic oscillator circuit includes a cross-coupled pair circuit connected to a resonant circuit. The cross-coupled pair circuit can be connected downstream of the resonant circuit. Such a cross-coupled pair circuit can include a cross-coupled NMOS transistor pair, and the source of each NMOS transistor is connected to the ground or other current sink. The gate of the first NMOS transistor of the cross-coupled NMOS transistor pair can be connected to the drain of the second NMOS transistor of the cross-coupled NMOS transistor pair, and the gate of the second NMOS transistor of the NMOS transistor pair can be connected to the drain of the first NMOS transistor of the NMOS transistor pair.

[0019] The terms "upstream" and "downstream" here refer to the direction of DC current flow from the power supply rail (or other power supply) to the ground rail (or other current sink) (or from a high rail to a low rail).

[0020] In some examples, the electronic oscillator circuit includes an injection clock source configured to apply a clock signal to the first current controller and the second current controller at a predetermined duty cycle so that the first current controller and the second current controller transition from the second state to the first state in response to the clock signal (i.e., the injection signal). This causes the injection current to flow from the first current controller (i.e., the power supply) to the second current controller (i.e., the ground or other current sink) through the resonant circuit at a frequency set by the clock (injection) signal (i.e., the frequency set by the duty cycle of the injection clock source).

[0021] In some examples, the duty cycle of the injected clock source can be selected to cause the first current controller and the second current controller to transition from the second state to the first state at a frequency close to the resonant frequency of the resonant circuit or a frequency having a harmonic component (e.g., Nth harmonic) close to the resonant frequency of the resonant circuit. In this way, the injected current can generate oscillations at a predetermined frequency in the resonant circuit by injection locking the oscillation of the resonant circuit to the frequency or harmonic component.

[0022] In some examples, the capacitor and the inductor can be connected in parallel in the resonant circuit to form an LC resonant circuit. In some examples, the capacitor can be one of a switchable capacitor bank to adjust the resonant frequency of the resonant circuit. In some examples, the capacitor can be a variable capacitor (e.g., a varactor), and its capacitance can be controllable.

[0023] From a second aspect, the present invention provides an electronic oscillator circuit, comprising:

[0024] a resonant circuit comprising a first inductor winding and a capacitor; and

[0025] an injection circuit, comprising a second inductor winding and a current controller;

[0026] wherein the injection circuit is not electrically connected to the resonant circuit;

[0027] wherein the current controller is configured such that when the current controller is in a first state, the injection current flows from the current controller through the second inductor winding;

[0028] wherein the current controller is configured such that when the current controller is in the second state, no injection current flows through the second inductor winding; and

[0029] The first inductor winding and the second inductor winding are coupled, so that an injected current in the second inductor winding of the injection circuit generates a corresponding injected current in the first inductor winding of the resonant circuit.

[0030] According to a second aspect of the present disclosure, there is provided an electronic oscillator circuit, comprising two non-electrically connected circuits, wherein the injection circuit comprises a current controller, which can be used to inject current into the inductive winding of the injection circuit. The current injection will generate a corresponding induced current in the inductive winding of the resonant circuit, thereby injecting the current into the resonant circuit. Injecting current into the resonant circuit allows energy to be injected into the resonant circuit. If operated properly, this will force the resonant circuit to oscillate at a predetermined frequency different from the natural resonant frequency of the resonant circuit. This can allow an oscillation signal of a predetermined frequency to be generated in the resonant circuit.

[0031] The two circuits are not electrically connected in the sense that current does not flow directly from one circuit to the other, but are coupled, i.e., current in one circuit is induced by the other circuit, such as by electromagnetic coupling. Thus, the two circuits may be arranged to be not physically connected or conductively connected, e.g., there is no physical conductor (such as a wire or trace) connecting the two circuits together that allows current to flow from one circuit to the other. Instead, the two circuits may be inductively coupled so that energy can be transferred between the two circuits. The two circuits may be mutually coupled.

[0032] In some examples, the inductive winding of the resonant circuit may include a pair of winding portions, namely a first winding portion and a second winding portion, connected between a first side and a second side of the resonant circuit and a common terminal, respectively. The common terminal may be a center tap of the inductive winding of the resonant circuit, for example, a contact approximately halfway through the inductive winding. Thus, the first winding portion and the second winding portion may be arranged such that in the first winding portion, the induced current flows from the center tap to the first side of the resonant circuit, and such that in the second winding portion, the induced current flows from the second side of the resonant circuit to the center tap. In some examples, the center tap may be connected to a power supply rail or other current supply.

[0033] The inductive winding of the injection circuit may further include a pair of winding portions, namely a third winding portion and a fourth winding portion.

[0034] The third winding portion and the fourth winding portion of the inductor winding of the injection circuit may be connected to a common terminal, which may be a center tap of the inductor winding of the injection circuit. The third winding portion and the fourth winding portion may be arranged so that the current in the third winding portion and the fourth winding portion flows toward or away from the common terminal (i.e., in opposite directions), and due to the arrangement of the first inductor winding and the second inductor winding relative to the third inductor winding portion and the fourth inductor winding portion, the induced current in the first winding portion and the second winding portion of the inductor winding of the resonant circuit flows in a common direction (i.e., from the first side of the resonant circuit to the second side of the resonant circuit; or from the second side of the resonant circuit to the first side of the resonant circuit). Therefore, the third winding portion and the fourth winding portion may be coupled to each other in a non-inverting relationship.

[0035] In some embodiments, the third winding portion and the fourth winding portion may be connected between respective power supply rails (or other current supplies) and a common terminal, which may be a center tap of an inductive winding of the injection circuit. In these embodiments, the center tap may be connected to a current controller of the injection circuit, such that the injection current in the third winding portion and the fourth winding portion flows from the respective power supply rails (or other current supplies) to the current controller via the center tap.

[0036] In some embodiments, the third winding portion and the fourth winding portion may be connected between respective grounds (or other current sinks) and a common terminal, which may be a center tap of an inductive winding of the injection circuit. In these embodiments, the center tap may be connected to a current controller of the injection circuit such that the injection current in the third winding portion and the fourth winding portion flows from the current controller to the ground (or other current sink) via the center tap.

[0037] In the above arrangement, the injection current in the injection circuit (for example at the center tap of the inductive winding of the injection circuit) can thus cause the injection current to be induced in the resonant circuit and flow around the resonant circuit. In such an example, the transfer of parasitic capacitance to the resonant circuit can be reduced.

[0038] In some examples, the current controller can be a switch. However, in some examples, the current controller can be an amplifier. In some preferred examples, the current controller in the injection circuit can be a transistor. In some such examples, the current controller can be a PMOS transistor, and the source of the PMOS transistor can be connected to a power supply rail or other current supply. In these examples, the inductor winding of the injection circuit can be arranged so that the drain of the PMOS transistor is connected to a terminal, such as a center tap, at the midpoint of the inductor winding of the injection circuit. Therefore, the inductor winding of the injection circuit can be connected between the terminal at the midpoint of the inductor winding and the other two terminals connected to the ground or other current sinks. In an embodiment in which the inductor winding of the injection circuit includes a third winding portion and a fourth winding portion, the third winding portion and the fourth winding portion can therefore be connected between the terminal at the midpoint of the inductor winding and the ground or other current sinks.

[0039] In some alternative examples, the current controller in the injection circuit can be an NMOS transistor, and the source of the NMOS transistor can be connected to ground or other current sinks. In these examples, the inductor winding of the injection circuit can be arranged so that the drain of the NMOS transistor is connected to a terminal at the midpoint of the inductor winding of the injection circuit, such as a center tap. Therefore, the inductor winding of the injection circuit can be connected between a terminal at the midpoint of the inductor winding and two other terminals connected to a power supply rail (or other current supply). In an embodiment in which the inductor winding of the injection circuit includes a third winding portion and a fourth winding portion, the third winding portion and the fourth winding portion can therefore be connected between a terminal at the midpoint of the inductor winding and a power supply rail (or other current supply).

[0040] An electronic oscillator circuit may include one or more oscillation-sustaining elements or circuits to offset losses due to an inherent impedance in the resonant circuit. In some examples, the resonant circuit of the electronic oscillator circuit may be connected to one or more negative impedance elements to overcome the inherent impedance of the resonant circuit to sustain oscillations within the resonant circuit that would otherwise be suppressed due to resistive losses. Thus, such negative impedance components may be used to promote oscillations within the resonant circuit such that the oscillations within the resonant circuit are sustained due to the negative impedance. The negative impedance element may take the form of one or more negative impedance circuits.

[0041] In some examples, the negative impedance element may include one or more cross-coupled circuits. In some examples, one or more cross-coupled circuits may include a first cross-coupled circuit connected to the resonant circuit. The cross-coupled circuit may be connected upstream of the resonant circuit. Such a cross-coupled circuit may include a cross-coupled PMOS transistor pair, the source of each PMOS transistor being connected to a power supply rail or other current supply. The gate of the first PMOS transistor of the cross-coupled PMOS transistor pair may be connected to the drain of the second PMOS transistor of the cross-coupled PMOS transistor pair, and the gate of the second PMOS transistor of the cross-coupled PMOS transistor pair may be connected to the drain of the first PMOS transistor of the cross-coupled PMOS transistor pair.

[0042] In some examples, the cross-coupled pair circuit can include a cross-coupled NMOS transistor pair, with the source of each NMOS transistor connected to ground or other current sinks. The gate of the first NMOS transistor of the cross-coupled NMOS transistor pair can be connected to the drain of the second NMOS transistor of the cross-coupled NMOS transistor pair, and the gate of the second NMOS transistor of the NMOS transistor pair can be connected to the drain of the first NMOS transistor of the NMOS transistor pair. The cross-coupled pair circuit can be connected downstream of the resonant circuit.

[0043] In some examples, the electronic oscillator circuit includes an injection clock source configured to apply a clock signal having a predetermined duty cycle to a current controller of the injection circuit, so that the current controller in the injection circuit transitions from the second state to the first state in response to the clock signal. This can cause the injection current to flow through the inductive winding of the injection circuit at a frequency set by the duty cycle of the clock signal. In this way, since the two windings are coupled to each other, the corresponding injection current can be injected through the inductive winding of the resonant circuit at a frequency set by the clock signal.

[0044] In some examples, the duty cycle of the injected clock source can be selected to cause the current controller to transition from the second state to the first state at a frequency close to the resonant frequency of the resonant circuit or having a harmonic frequency component (e.g., an Nth harmonic component) close to the harmonic frequency of the resonant circuit. In this way, the injected current can force oscillations to occur in the resonant circuit at a predetermined frequency by locking the injection of the resonant circuit to the frequency.

[0045] Features of any aspect or embodiment described herein may be applied to any other aspect or embodiment described herein as appropriate.When referring to different embodiments or sets of embodiments, it should be understood that these embodiments or sets of embodiments are not necessarily distinct, but may overlap with each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Some preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings:

[0047] Figure 1a is a schematic diagram of an LC resonant circuit according to the prior art;

[0048] Figure 1b is a schematic diagram of an LC resonant circuit including an NMOS cross-coupled pair circuit according to the prior art;

[0049] Figure 2a and 2b Schematically showing a PMOS-based and NMOS-based cross-coupled pair circuit according to the prior art;

[0050] Figure 3 A complementary (with NMOS and PMOS) cross-coupled oscillator circuit according to the prior art is shown;

[0051] Figure 4a and 4b schematically illustrates an LC oscillator circuit including a feedback loop with and without current injection according to the prior art;

[0052] Figure 5 is a schematic diagram of an injection locked oscillator according to the prior art;

[0053] Figure 6 is a schematic diagram of an injection locked oscillator according to an embodiment of the present invention;

[0054] Figure 7 is a schematic diagram of an injection locked oscillator according to an embodiment of the present invention;

[0055] Figure 8 is a schematic diagram of an injection locked oscillator according to an embodiment of the present invention;

[0056] Fig. 9is a schematic diagram of an injection locked oscillator according to an embodiment of the present invention;

[0057] Fig.10a and 10b schematically illustrates a first arrangement of an inductor winding that can be used with an injection locked oscillator according to an embodiment of the present invention, and a first physical arrangement of an inductor winding in a CMOS circuit according to the present invention; and

[0058] Fig.11a and 11b The injection locked oscillator according to the embodiment of the present invention and the second physical arrangement of the inductor winding in the CMOS circuit according to the present invention are schematically shown. DETAILED DESCRIPTION

[0059] FIG. 1 shows an LC resonant circuit 100 including an inductor 101 and a capacitor 103. In such an LC resonant circuit, if the capacitor 103 is initially charged, the voltage across the capacitor 103 drives a current through the inductor 101, thereby generating a magnetic field around the inductor 101. As the current passes through the inductor 101, the charge stored in the capacitor 103 is depleted, and the voltage across the capacitor 101 decreases until there is no voltage difference across the capacitor 103. At this point, the magnetic field around the inductor 101 generates an EMF on the inductor 101 with an opposite polarity to the initial polarity, causing the current to flow in the opposite direction, recharging the capacitor 103 with a polarity opposite to its original state. The charged capacitor 103 is then discharged through the inductor 101, and the process is repeated at a characteristic resonant frequency, which is determined by the capacitance and inductance of the capacitor 103 and the inductor 101, respectively. The resonant frequency of such a circuit is Therefore, the repeated charging of capacitor 103 and the generation of a magnetic field around inductor 101 causes LC resonant circuit 100 to store energy and act as a harmonic oscillator to generate a signal at a resonant frequency ω 0. Therefore, an LC resonant circuit such as LC resonant circuit 100 can be used to generate a sinusoidal signal at a resonant frequency ω 0 defined by the capacitance and inductance of its components.

[0060] Due to the inherent impedance of the LC resonant circuit 100, the energy stored in the LC resonant circuit 100 decreases over time as a result of resistive losses, thereby suppressing the resonant behavior. The severity of the attenuation of the oscillation amplitude in the LC resonant circuit 100 is determined by the impedance of the LC resonant circuit 100, that is, it is related to the capacitance and inductance in the LC resonant circuit 100. However, if the resistive losses are eliminated, or the LC resonant circuit 100 is driven (i.e., energy is provided to the LC resonant circuit 100) at or near the resonant frequency ω0, the oscillation in the LC resonant circuit 100 can be maintained.

[0061] Whether oscillation is maintained in an LC resonant circuit can be determined by the so-called "Barkhausen Criteria", which states that in a linear circuit with a feedback loop, a stable oscillation state can be maintained as long as the following are met:

[0062] i) the absolute value of the loop gain is equal to 1; and

[0063] ii) The phase shift in the loop is zero or an integer multiple of 2π.

[0064] Therefore, maintaining this criterion is crucial in order to provide a frequency and amplitude stable harmonic LC oscillator.

[0065] In order to achieve a gain equal to or greater than 1 in an LC resonant circuit, the inherent impedance within the LC resonant circuit needs to be overcome. One way to achieve this is to introduce a negative impedance component into the LC resonant circuit to effectively cancel its inherent impedance so that the LC resonant circuit behaves more like a model LC oscillator, where the oscillations are not damped.

[0066] Negative impedance can be introduced into an LC resonant circuit using active components such as transistors. Various arrangements of active components can be used to introduce negative impedance into the circuit to which they are connected. One method is to introduce a "cross-coupled pair circuit" such as Figure 1b shown.

[0067] Figure 1b An LC oscillator circuit 105 is shown, including an LC resonant circuit 120 and a cross-coupled pair circuit 110, the cross-coupled pair circuit 110 including two NMOS transistors 111 and 113, each of which has its source (111a and 113a, respectively) connected to ground. The NMOS transistors 111 and 113 are arranged so that the gate 111b of the first transistor 111 is connected to the drain 113c of the second transistor 113, and the gate 113b of the second transistor 113 is connected to the drain 111c of the first transistor 111. Connected in this manner, the NMOS transistors 111, 113 together provide a negative impedance source for the LC resonant circuit 100. The impedance of the cross-coupled pair circuit 110 can be equal to -2 / g m , where g m It is the transconductance of an NMOS transistor, i.e. the ratio of the drain current to the voltage across the gate-source.

[0068] By appropriately selecting the characteristics of the NMOS transistors 111, 113 of the cross-coupling pair circuit 110 according to the impedance of the LC resonant circuit 120 (i.e., making the negative impedance they generate approximately equal to the impedance of the LC resonant circuit 120), the inherent impedance within the LC resonant circuit 120 can be effectively offset, thereby achieving a circuit gain of 1 or greater.

[0069] Although Figure 1b The cross-coupled pair circuit 110 is shown to include NMOS transistors, but Figure 2a As shown, the same effect can be achieved using PMOS transistors.

[0070] Figure 2a A cross-coupled pair circuit arrangement 210 implemented using PMOS transistors 211, 213 is shown. For ease of comparison, Figure 2b Reappeared Figure 1b The cross-coupled pair circuit arrangement 110 shown is implemented using NMOS transistors 111 and 113. The two cross-coupled pair circuits 110 and 210 have the same function, namely providing negative impedance for the connected LC resonant circuit. Figure 1b However, since the majority of charge carriers are electrons and thus have greater charge mobility, NMOS-based circuits are generally preferred.

[0071] It is also possible to introduce negative impedance into the LC resonant circuit by providing a PMOS and NMOS cross-coupled pair circuit located upstream and downstream of the LC resonant circuit, i.e. closer and further away from the power supply rail, respectively. Figure 3 An example of such a complementary cross-coupled oscillator circuit 300 is seen in .

[0072] Figure 3 A complementary cross-coupled oscillator circuit 300 is shown, which includes an LC resonant circuit 320, an upstream PMOS cross-coupled pair circuit 210 (such as Figure 2a ) and downstream NMOS cross-coupled pair circuit 110 ( Figure 2b By connecting the PMOS cross-coupling pair circuit 210 and the NMOS cross-coupling pair circuit 110 respectively upstream and downstream of the LC resonant circuit 320, a negative impedance can be introduced into the circuit in a more power-saving manner compared to a single PMOS or NMOS cross-coupling circuit, while still effectively eliminating the inherent impedance in the circuit.

[0073] By canceling the inherent impedance of the LC resonant circuit, an LC oscillator including a negative impedance element (such as Figure 1b to Figure 3 As shown) is able to maintain oscillation at the resonant frequency of the LC resonant circuit.

[0074] Although the introduction of a negative impedance component provides the first method of maintaining oscillation in an LC resonant circuit, it is not the only method of achieving a gain of 1 to satisfy the Barkhausen criterion. Unity gain or greater can also be achieved by driving the LC resonant circuit (i.e., introducing energy into the LC resonant circuit to maintain oscillation).

[0075] Energy can be introduced into the LC resonant circuit through a feedback loop that includes an amplifier connected to the output of the LC resonant circuit so that a portion of the output signal can be used to compensate for resistive losses in the LC resonant circuit. In this implementation, a small portion of the output signal of the LC resonant circuit can be provided to the input of the amplifier, and the amplified signal can then be fed back into the LC resonant circuit. Thus, the amplifier can be used to provide positive feedback to the LC resonant circuit to maintain oscillation of the circuit at its resonant frequency.

[0076] Figure 4a To provide an example in this regard, an oscillator circuit 400a includes an LC resonant circuit 420a and a feedback loop 430a, wherein the feedback loop 430a includes an NMOS transistor 431a and an inverting amplifier 433a. It is understood that the feedback loop 430a between the inverting amplifier 433a and the NMOS transistor 431a is connected by a connection marked as V fb The circuit 400a is composed of two connections (for simplicity, the connecting lines in the figure are disconnected). In operation, when the oscillator circuit 400a is initially turned on, the electronic noise in the circuit provides a non-zero signal to the inverting amplifier 433a. The noise propagates around the LC resonant circuit 420a to generate a signal at the resonant frequency of the LC resonant circuit 420a, which is repeatedly amplified by the inverting amplifier 433a and fed back to the LC resonant circuit 420a until a steady-state oscillation signal is achieved at the resonant frequency. The role of the NMOS transistor 431a is to provide a 180-degree phase shift in the feedback loop, which, combined with the phase shift of the inverting amplifier 433a, ensures that the total phase shift in the loop is zero. Since the gain of the oscillator circuit 400a is greater than or equal to 1 and the phase shift is zero, the Barkhausen criterion is met, and the oscillator circuit 400a can continue to oscillate at the resonant frequency of the LC resonant circuit 420a.

[0077] In reference to Figures 1 to Figure 4a Having outlined how to use a negative impedance element or a positive feedback loop to maintain an LC resonant circuit oscillating at its resonant frequency, we will now refer to Figure 4b to Figure 11b Describe methods for controlling the frequency of these oscillations.

[0078] Since the resonant frequency of the LC resonant circuit is determined based on its inductance and capacitance, such as Therefore, the resonant frequency of the LC resonant circuit can usually be controlled by selecting appropriate capacitors (for example, using variable capacitance, i.e., varactors or switched capacitor banks) and inductors to provide the desired resonant frequency. However, it is not always possible to achieve an arbitrary resonant frequency by selecting appropriate capacitors and inductors while also achieving a sufficiently high quality factor.

[0079] In this case, the LC oscillator can be "forced" to oscillate at a frequency different from, but close to, its resonant frequency, using a phenomenon called injection locking, as described below. This is useful, for example, when the inductor and capacitor have high quality factors and the resonant frequency of the circuit is close to, but not exactly, the desired operating frequency of another part of the larger circuit.

[0080] For example, if a portion of a circuit including an LC oscillator requires an input signal of a predetermined frequency (e.g., 5.0 GHz), and high-quality capacitors and inductors are selected to provide an LC resonant circuit with a resonant frequency of 5.1 GHz, the injection locking function can be used to force the LC resonant circuit to oscillate at 5.0 GHz.

[0081] Injection locking occurs when a first oscillator oscillating at a first frequency is interfered with by a second oscillator oscillating at a nearby frequency. When there is strong coupling between the first and second oscillators, and the frequencies of the first and second oscillators are close enough, the first oscillator can be "pulled" by the second oscillator and its oscillation frequency can effectively be the same as the second oscillator.

[0082] In the context of an LC resonant circuit, the second oscillating signal may be provided by introducing a current into the LC resonant circuit at a predetermined frequency close to a natural resonant frequency of the LC resonant circuit.

[0083] Figure 4b An example of an oscillator circuit including current injection is provided, wherein an oscillation circuit 400b is shown to include an LC resonant circuit 420b and a feedback loop 430b, wherein the feedback loop 430b includes an NMOS transistor 431b and an inverting amplifier 433b, and Figure 4a As described in Figure 4a As shown, the feedback loop 430b between the inverting amplifier 433b and the NMOS transistor 431b is Figure 4b The V fb The two connections will be connected together. Figure 4a As shown, the NMOS transistor 431b provides a 180 degree phase shift in the feedback loop (providing a total phase shift of 2π in the loop) to ensure that the Barkhausen criterion is met. The oscillator circuit 400b also includes an injection current source 440 for injecting a current with a frequency of ω into the drain of the NMOS transistor 431b. inj The sinusoidal current I inj .

[0084] Injecting current I into the LC oscillator circuit inj The effect depends on the injected current I inj The phase relationship between the oscillation of the LC resonant circuit 420b.

[0085] If the injected current I inj If there is no phase difference with the oscillation of the LC resonant circuit 420b, then the LC oscillator 400b will continue to oscillate at the resonant frequency of the LC resonant circuit 420b, although the amplitude will increase in the absence of any limiter. However, if the current injection is not completely in phase with the oscillation of the LC resonant circuit 420b, a phase shift, such as a shift of φ radians, will be introduced into the LC resonant circuit 420b.

[0086] According to the above-mentioned Barkhausen criterion ii), after the phase shift is introduced, the steady-state oscillation cannot be maintained because the total phase shift in the loop is no longer equal to 0 or 2π. Therefore, the non-zero phase shift causes the oscillation frequency of the LC resonant circuit 420b to change from ω0 to a new value ω1 to compensate for the phase shift in the LC resonant circuit 420b, so that the resonant circuit generates a corresponding phase shift to offset the effect of the phase shift φ.

[0087] According to the injected current I inj The amplitude and frequency ω inj , the LC resonant circuit 420b can be injection locked, and the oscillation frequency of the oscillation circuit 400b is ω1=ω inj is equal to the frequency of the injected current, rather than the natural resonant frequency ω0 of the LC resonant circuit. In this way, the injected current can be used to change the frequency of the LC resonant circuit (such as the LC resonant circuit 420b).

[0088] Whether injection locking occurs depends on the locking range, that is, the range of ω that injection locking can maintain. inj Range. The maximum lock range can be given by:

[0089]

[0090] Among them I osc is the oscillator current, e.g. Figure 4b The drain current of the NMOS transistor 431b.

[0091] Therefore, by properly choosing I inj and ω inj , the oscillator including the LC resonant circuit can be made to have a desired frequency ω1=ω close to the resonant frequency ω0 of the LC resonant circuit. inj oscillation.

[0092] Figure 5 An injection locked oscillator according to the prior art is shown. The injection locked oscillator 500 comprises a cross-coupled pair circuit 510 (not shown in detail but represented as -2 / g) connected to an LC resonant circuit 520. m ), and a current injection source in the form of a transistor 550. The gate of the transistor 550 is connected to the injection source, which is arranged to receive a current from a frequency ω injApplying a voltage at the gate of transistor 550 causes a current in LC resonant circuit 520 to flow through transistor 550, which in turn generates a signal at a frequency ω set by an injected clock source (not shown) connected to the gate of transistor 550. inj The LC resonant circuit 520 is introduced. This process effectively inj The LC resonant circuit 520 is briefly short-circuited, energy is removed from the LC resonant circuit 520, and a phase difference is introduced into the LC resonant circuit 520. The phase difference causes the frequency of the LC resonant circuit 520 to change from the resonant frequency ω0 to the new frequency ω1=ω set by the clock signal. inj .

[0093] The advantage of "shorting" (i.e. applying phase correction) over injecting current is that it minimizes disturbance to the oscillator amplitude and pushes the oscillator phase towards the zero crossing point. For non-50% duty cycle injected signals, the injected signal is usually a train of very narrow pulses and the phase correction is usually implemented at the beginning / end of each cycle. This also minimizes unnecessary current consumption.

[0094] It is well known that it is beneficial to inject current at a frequency below the injection locking frequency. One way to achieve this is to inject current at a frequency below the resonant frequency of the LC tank circuit, but with harmonic components at the desired locking frequency.

[0095] For example, for an LC resonant circuit with a natural resonant frequency of 5.1 GHz, in principle, a 1 GHz injection signal can be used to lock the frequency of the LC resonant circuit to 5 GHz, that is, the fifth harmonic of the 1 GHz signal. By relying on harmonics rather than the injection frequency, a low-frequency clock source can be used to injection-lock the LC resonant circuit to a higher frequency. In other words, the LC resonant circuit can be forced to oscillate at a frequency ω1 that is N times the injection current frequency, that is, ω1 = Nω inj , allowing greater flexibility in the choice of clock source, for example, allowing the use of a clock source that requires less power.

[0096] If a stable low-frequency clock signal is used whose Nth harmonic is close to the desired injection locking frequency, an injection signal can be used to compensate the frequency of the oscillating signal in the LC resonant circuit 520 to the natural resonant frequency every N cycles. The injection signal "pulls" the oscillating signal in the LC resonant circuit 520 to the frequency of the Nth harmonic of the clock signal every N cycles.

[0097] For example, if a 1 GHz injection signal is used to lock the frequency of an LC resonant circuit with a natural resonant frequency of 5.1 GHz to a 5 GHz injection locking frequency, i.e., the fifth harmonic of the 1 GHz signal, then the LC oscillation signal will inject current only once every 5 cycles. If the natural frequency of the LC oscillation is not exactly consistent with the fifth harmonic of the injection signal, the pulse widths of the four cycles before the injection pulse (i.e., the 5th cycle) will be different. Therefore, the LC oscillation signal will be "pulled" (i.e., the 5th pulse becomes shorter or longer) with the injection signal, causing the signal in the LC resonant circuit 520 to be locked to the Nth harmonic frequency, i.e., 5 GHz in this example. Phase correction forces the average frequency to be equal to the injection frequency, i.e., when locked, the average frequency error of the injection locked oscillator is zero.

[0098] Therefore, a lower frequency injection signal can be used to induce injection locking at one of its higher frequency harmonics. This allows a low frequency clock source to be used while still generating a high frequency signal in the LC resonant circuit. Figure 6 An example of such a circuit is described with reference to FIG. 10 .

[0099] Figure 6 FIG. 6 shows an injection locked oscillator 600 according to an embodiment of the present invention. The injection locked oscillator 600 includes an LC resonant circuit 620, an upstream PMOS cross-coupling pair circuit 210 (such as Figure 2a ) and downstream NMOS cross-coupled pair circuit 110 ( Figure 2b shown).

[0100] Compared with the prior art oscillator circuit (such as Figure 3 Compared with the complementary cross-coupled oscillator circuit 300 shown in the figure, the injection locked oscillator 600 further includes two current controllers, which are respectively connected across the LC resonant circuit 620 in the form of a PMOS transistor 660 and an NMOS transistor 670. In particular, the PMOS transistor 660 is connected to a first side of the LC resonant circuit 620 (i.e., corresponding to the first terminal of the inductor and the capacitor), and the NMOS transistor 670 is connected to a second side of the LC resonant circuit 620 (i.e., corresponding to the second terminal of the inductor and the capacitor).

[0101] PMOS transistor 660 and NMOS transistor 670 are connected to a clock source 680, which is configured to apply a negative voltage -V to the gate of the PMOS transistor. inj , apply a positive voltage +V to the gate of the NMOS transistor inj , injection frequency ω inj, whose Nth harmonic ω1 is close to the resonant frequency ω0 of the LC resonant circuit 620. The clock source 680 is configured to apply an injection signal in the form of a pulse stream. These pulses are preferably narrow in the time domain, for example, the pulse width is around 100 ps, ​​or in some embodiments does not exceed 50 picoseconds. The width of these pulses can alternatively be defined as a duty cycle of no more than 10%, or in some embodiments no more than 5% of the injection signal.

[0102] The injection locked oscillator 600 can oscillate at the resonant frequency ω0 of the LC resonant circuit 620, as shown above, because the cross-coupling pair circuits 110 and 210 generate negative impedance within the circuit, and the resonant frequency is maintained. In the case of appropriate injection of current through the LC resonant circuit 620, the injection locked oscillator 600 can also oscillate at the frequency ω1 by injection locking to the injected current signal.

[0103] exist Figure 6 In the injection locked oscillator 600 shown, current injection is performed by using a PMOS transistor 660 and an NMOS transistor 670, as described below. It can be understood that the injection locking in the injection locked oscillator 600 is a low injection frequency ω inj (whose Nth harmonic is located at ω1), rather than at frequency ω1.

[0104] The injection is performed using an injection clock source 680 at a frequency of ω1. inj At the same time, a voltage pulse with a very short duration (on the order of tens of picoseconds, for example, no more than 100 ps or no more than 50 ps) is output to the PMOS transistor 660 and the NMOS transistor 670. This will cause the gates of the PMOS transistor 660 and the NMOS transistor 670 to generate voltages of opposite polarity during the pulse duration. When voltage is applied to the gates of the PMOS transistor 660 and the NMOS transistor 670, current flows from the PMOS transistor 660 to the NMOS transistor 570 through the LC resonant circuit 620. In this way, the current flows at a frequency of ω inj =ω1 / N injected into the LC resonant circuit.

[0105] Compared with typical injection locked oscillators (such as Figure 5 Unlike the injection locked oscillator 500 shown in FIG. 1 , the current in the injection locked oscillator 600 does not simply remove energy by shorting the LC resonant circuit. Instead, the current (and energy) is introduced into the circuit from the PMOS transistor 660 and then flows out of the circuit through the NMOS transistor 670.

[0106] Since the injection frequency is about N times lower than the resonant frequency of the LC resonant circuit 620, the oscillation signal in the LC resonant circuit 620 injects current only once every N cycles. In the N-1 cycles after each current injection, the phase of the oscillation in the LC resonant circuit 620 may deviate from the phase of ω1 (i.e., at ω inj This causes the oscillation frequency of the LC resonant circuit 620 to shift between the injected pulses. inj The injected current "pulls" the oscillation frequency of the LC resonant circuit 620 to the frequency of the Nth harmonic, thereby correcting any offset that may have occurred during the first N-1 cycles and maintaining the oscillation at the ω1 frequency.

[0107] This is achieved in the injection locked oscillator 600, where a current spike of extremely short duration (on the order of tens of picoseconds) is applied in the time domain each time current is injected, i.e., at the rate set by the injection clock 680. This short pulse in time is equivalent to a broadband signal in the frequency domain. Therefore, by appropriately controlling the width of the pulse in the time domain (for example, by providing a sufficiently narrow pulse in the time domain), a frequency domain signal can be generated, which has components over a wide frequency range, including a component of the Nth harmonic ω1 close to the resonant frequency ω0, and the signal in the LC resonant circuit 620 can be locked to this frequency. The pulse width of the injected pulse determines the strength of the Nth harmonic, so by applying a sufficiently short pulse, a strong injection signal can be generated at the Nth harmonic, thereby achieving injection locking.

[0108] Specifically, each time current is injected, the current flowing into the circuit from the source of the PMOS transistor corrects the peak value of the oscillating signal, “pulling” it to ω inj The signal peak at the harmonic ω1 of the injected current. Similarly, the current flowing out of the circuit flows to the current sink () at the NMOS transistor, by "pulling" the valley of the oscillating signal to ω inj The trough of the signal at the harmonic ω1 of the injected current is corrected, so that the trough of the oscillation signal is corrected. Therefore, each time a current pulse is provided, the oscillation signal in the LC resonant circuit 620 is corrected, so that the oscillation frequency of the LC resonant circuit 620 matches the frequency of the Nth harmonic ω1 of the injected signal, regardless of the phase of the oscillation signal in the LC resonant circuit 620 when the current is injected. By "correcting" the oscillation signal in the LC resonant circuit at the peaks and troughs of the oscillation signal, rather than short-circuiting at the zero crossing point as in the prior art, the energy injected into the LC resonant circuit can be better controlled. Therefore, compared with the prior art, the achievable locking range is increased.

[0109] Thus, by injecting a significantly lower frequency ω into the injection locked oscillator 600 injThe current of can force the injection locked oscillator 600 to oscillate at a predetermined frequency ω1 close to the resonant frequency ω0 of the LC resonator 620.

[0110] Figure 7 An injection locked oscillator 700 according to a second embodiment of the present invention is shown.

[0111] The injection locked oscillator 700 comprises two electrically separated circuits: an oscillator circuit 701 and an injection circuit 703. The oscillator circuit 701 comprises an LC resonant circuit 720 including an inductor in the form of a first inductive winding 711, a capacitor 713 and a downstream NMOS cross-coupled pair circuit 110, such as Figure 2b Circuits 701, 703 are electrically separated in that current does not flow directly from one circuit to the other.

[0112] The oscillator circuit 701 can be used to generate a periodic signal at a resonant frequency ω0 defined by the capacitance of the capacitor 713 and the inductance of the first inductor winding 711, in the same manner as described above with respect to FIGS. 1 to 2. Figure 6 The effect of the NMOS cross-coupling pair circuit 110 is to provide negative impedance in the oscillator circuit 701, thereby effectively offsetting the inherent impedance in the LC resonant circuit 720, so that the increase of the oscillator circuit 701 reaches or exceeds 1, thereby reducing the damping of the oscillation in the LC resonant circuit 720.

[0113] like Figure 6 As shown, when current is appropriately injected through the LC resonant circuit 720, the oscillator circuit 701 can also be forced to perform injection locking on the injected current signal with a frequency of ω1 (or a harmonic of ω1) so that it oscillates at a frequency ω1 close to the resonant frequency ω0.

[0114] In injection locked oscillator 700, current is injected into oscillator circuit 701 using injection circuit 703, which is electrically separate from oscillator circuit 701. Injecting current using a circuit electrically separate from oscillator circuit 701 advantageously reduces parasitic capacitance in LC resonant circuit oscillator circuit 701.

[0115] The injection circuit 703 includes a second inductor winding 715 and an NMOS transistor 717. The second inductor winding 715 is connected to a power supply rail 716 and an NMOS transistor 717. The NMOS transistor 717 is connected to ground and to an injection clock source 780, which is configured to generate an injection signal at an injection frequency ω. inj A voltage V is applied to the gate of the NMOS transistor 717. inj , the Nth harmonic of the injected frequency ω1 is close to the resonant frequency ω0 of the LC resonant circuit 720 .

[0116] When the voltage V injWhen applied to the gate of the NMOS transistor 717, current flows from the power supply rail 716 to the ground through the second inductor winding 715 and the NMOS transistor 717. Therefore, a frequency ω is introduced into the second inductor winding 715. inj A current having the Nth harmonic of the frequency ω1.

[0117] Although the injection circuit 703 and the oscillator 701 are electrically separated, i.e., no current flows directly between them, the first inductor winding 711 and the second inductor winding 715 are arranged so that they are electromagnetically coupled. Therefore, the first inductor winding 711 and the second inductor winding 715 are arranged so that they form the primary winding and the secondary winding of the transformer, respectively. In this way, the injection current in the second inductor winding 715 will generate a corresponding induced current in the first inductor winding 711, and the induced current also has a frequency ω inj .

[0118] Therefore, the induced injection current has a frequency of ω inj flows through the LC resonant circuit 720, with a frequency ω inj The Nth harmonic has a frequency ω1 close to the resonant frequency ω0 of the LC resonant circuit 720. This will cause the oscillation in the LC resonant circuit 720 to be injection locked in response to the injected current, thereby "pulling" the oscillation frequency in the LC resonant circuit to the frequency of the Nth harmonic, that is, causing the oscillation in the LC resonant circuit 720 to occur at ω1 instead of ω0. However, as Figure 6 As described above, since the injection frequency is approximately N times lower than the resonance frequency of the LC resonance circuit 720 , the oscillation signal in the LC resonance circuit 720 injects current at the frequency ω1 once every N cycles.

[0119] Between the two current injections, the phase of the oscillation in the LC resonant circuit 720 may therefore deviate from ω1 (i.e., at ω inj The frequency of the oscillation in the LC resonant circuit 720 may shift between injection pulses and must be overcome each time current is injected to maintain the oscillation at frequency ω1. Figure 6 As shown in the injection locked oscillator 600, this is achieved by applying a current spike of extremely short duration (on the order of tens of picoseconds) in the time domain (equivalent to a broadband signal in the frequency domain) each time current is injected.

[0120] Since the broadband signal in the frequency domain contains components with a very wide frequency range, including components on the Nth harmonic frequency ω1 close to the resonant frequency ω0, the oscillating signal in the LC resonant circuit 720 will be "pulled" to the frequency of the Nth harmonic each time it locks the signal component on the frequency ω1, regardless of the phase of the oscillating signal in the LC resonant circuit 720 when the current is injected.

[0121] Therefore, the oscillation circuit 701 of the injection-locked oscillator 700 can be injected into the injection circuit 703 by injecting a significantly lower frequency ω inj The current is forced to oscillate at a predetermined frequency ω1 close to the resonant frequency ω0 of the LC resonant circuit 720.

[0122] Although Figure 7 The injection circuit 713 is shown as an inductor winding connected between the power supply rail 716 and the NMOS transistor, but it is understood that the injection circuit can equivalently include an inductor winding having a first terminal connected to ground and a second terminal connected to a PMOS transistor connected to the power supply rail 816 and configured to receive a voltage –V from the injection clock source 780 inj .

[0123] In some preferred embodiments, Figure 7 The inductor winding shown (including two terminals connected between the power supply rail 716 and the NMOS transistor, respectively) can be replaced by a three-terminal inductor (ie, Figure 8 center-tapped inductor as shown) instead.

[0124] Figure 8 An injection locked oscillator 800 is shown, wherein an injection circuit 803 can be used to inject current into a first inductor winding 811 of the oscillator circuit 801. The injection circuit 803 includes a second inductor winding 815 and an NMOS transistor 817. Figure 7 The difference is that the second inductor winding 815 has three terminals: the first terminal and the second terminal located at the end points of the second inductor winding 815 are connected to the power supply rail 816, and the third terminal located at the midpoint of the second inductor winding 815 is connected to the NMOS transistor 817 in the form of a center tap.

[0125] NMOS transistor 817 is connected to ground and to a clock source 880, which is configured to inject a frequency ω inj A voltage V is applied to the gate of the NMOS transistor 817. inj , the Nth harmonic frequency ω1 of the injection frequency is close to the resonant frequency ω0 of the LC resonant circuit 820.

[0126] When the voltage V inj When applied to the gate of the NMOS transistor 817, current flows from the power supply rail 816 to the ground through the second inductor winding 815 and the NMOS transistor 817. Therefore, a frequency ω is introduced into the second inductor winding 815. inj The current has Nth harmonic frequency ω1.

[0127] The arrangement of the first inductor winding 811 and the second inductor winding 815 is similar to the above Figure 7In this way, the current in the second inductor winding 815 will generate a corresponding induced current in the first inductor winding 811, and the induced current also has a frequency ω inj .

[0128] Although Figure 8 The injection circuit 803 is shown using an NMOS transistor, but may also be implemented using a PMOS transistor with its source connected to the power supply rail 816 and the first and second terminals of the second inductor connected to ground. Fig. 9 An example of such a system is shown.

[0129] Fig. 9 900 according to an embodiment of the present invention. The injection locked oscillator 900 includes two electrically separated circuits: an oscillator circuit 901 and an injection circuit 903. The oscillator circuit 901 includes an LC resonant circuit 920, which includes a first inductor 911 in the form of an inductor winding, a capacitor 913 and a downstream NMOS cross-coupled pair circuit 110, such as Figure 2b shown.

[0130] The oscillator circuit 901 can be used to generate a periodic signal at a resonant frequency ω0 defined by the capacitance of the capacitor 913 and the inductance of the first inductor winding 911. The effect of the NMOS cross-coupling pair circuit is to provide negative impedance in the oscillator circuit 901, reducing the oscillation damping in the above-mentioned LC resonant circuit 920.

[0131] The current is injected into the oscillator circuit using an injection circuit 903. The injection circuit 903 includes a second inductor winding 915 and a PMOS transistor 917. The second inductor winding 915 has three terminals: a first terminal and a second terminal located at the end points of the inductor winding 915, both connected to ground, and a third terminal in the form of a center tap located at the midpoint of the second inductor winding 915, connected to the drain of the PMOS transistor 917. The source of the PMOS transistor 917 is connected to the power supply rail 916, and the gate of the PMOS transistor 917 is connected to the injection clock source 980, which is configured to generate an injection frequency at the injection frequency ω. inj Applied voltage - V inj , which has an Nth harmonic of a frequency ω1 close to the resonant frequency ω0 of the LC resonant circuit 920 .

[0132] When the voltage -V inj When applied to the gate of PMOS transistor 917, the current flows at a frequency ω inj The current flows from the PMOS transistor 917 through the second inductor winding 815 .

[0133] The first inductor winding 911 and the second inductor winding 915 are connected to Figure 8 The first and second inductor windings 915 are coupled and arranged in the same manner to form the primary winding and the secondary winding of the transformer, respectively. inj A corresponding current is induced in the first inductor winding 911. Therefore, in the LC resonant circuit 920, a current with a frequency ω inj An injection current is introduced, which has the Nth harmonic of a frequency ω1 close to the resonant frequency ω0 of the LC resonant circuit 920. If the locking range is large enough, this will cause the oscillation in the LC resonant circuit 920 to be injection locked at the frequency ω1.

[0134] As above Figure 8 As described in the description, the injection current introduced by the PMOS transistor 917 appears in the form of a current spike with a very short duration (tens of picoseconds, for example, no more than 100 ps or no more than 50 ps), which is equivalent to a broadband signal in the frequency domain. The broadband signal contains a frequency component at the Nth harmonic frequency ω1 of the injection signal, which is close to the resonance frequency ω0 of the oscillation signal in the LC resonant circuit 920. This forces the oscillation signal in the LC resonant circuit 920 to perform phase correction at the frequency ω1, regardless of the phase of the oscillation signal in the LC resonant circuit 920 when the injection current is applied.

[0135] and Figure 6 Compared to the injection locked oscillator 600 shown, Figure 7 , Figure 8 and Fig. 9 The illustrated injection locked oscillators 700, 800 and 900 have various advantages. For example, since the NMOS transistors 717 and 817 and the PMOS transistor 917 are not directly connected to the LC resonant circuits 720, 820 and 920, respectively, the parasitic capacitance of the LC resonant circuits 720, 820 and 920 is reduced. In addition, since the injection transistors are located at the center tap of the second inductor winding 815 (and equivalently 915), the parasitic effects seen by the first inductor winding 811 (and equivalently 911) are also reduced.

[0136] Figure 10a-11b Shows the available Figure 8 and 9 The arrangement of the inductor windings of the injection locked oscillators 800 and 900 is shown to allow current to be injected into the LC resonant circuits 820 and 920. Figure 10a-11b In, refer to Figure 8 The injection locked oscillator 800 shown is described with respect to the arrangement of the windings, but it will be appreciated that they are equally applicable to Fig. 9 An injection locked oscillator 900 is shown.

[0137] Fig.10a Shows Figure 8The first inductor winding 811 and the second inductor winding 815 of the injection-locked oscillator 800 are advantageously arranged, and this arrangement can reduce the parasitic capacitance transmitted to the first inductor winding 811 of the resonant circuit 820.

[0138] exist Fig.10a In the arrangement shown, it can be seen that the first inductor winding 811 is composed of three terminals P1, P2, P3 and two winding sections, namely the first winding section 1001a and the second winding section 1003a. Terminals P1 and P2 are connected to opposite sides of the LC resonant circuit 820, respectively, while terminal P3 is connected to a power supply rail, which is used to power the transistors of the cross-coupled pair circuit 110 of the injection-locked oscillator 800. The second inductor winding 815 also includes three terminals P4, P5, P6 and two winding sections: the third winding section 1001b and the fourth winding section 1003b. As shown in FIG. Figure 8 As shown, terminal P6 is connected to NMOS transistor 817 , and terminals P4 and P5 are both connected to power supply rail 816 .

[0139] When a voltage is applied to the gate of the NMOS transistor 817 , current flows from the power supply rail 816 through the third winding portion 1001 b and the fourth winding portion 1003 b of the winding 815 to ground via the NMOS transistor 817 .

[0140] The first winding portion 1001a of the first inductor winding 811 and the third winding portion 1001b of the second inductor winding 815 are arranged in a non-inverting structure, that is, a current is induced in the first winding portion 1001a of the first inductor winding 811, and the current flows from one side of the oscillation circuit to the center tap.

[0141] The second winding portion 1003a of the first inductor winding 811 and the fourth winding portion 1003b of the second inductor winding 815 are arranged in an anti-phase structure, that is, a current is induced in the second winding portion 1003a of the first inductor winding 811, and the current flows from the center tap to the other side of the oscillation circuit.

[0142] Therefore, the current injected at P6 will produce a differential current between P1-P2.

[0143] Therefore, the induced current generated in the first inductor winding 811 flows through the LC resonant circuit 820, so that the injected current can maintain the oscillation of the oscillation circuit at ω1.

[0144] Fig.10bAn example of how to form the first inductor winding 911 and the second inductor winding 815 respectively using one or more ultra-thick metal layers in CMOS technology is provided. It can be seen that in this arrangement, the first inductor winding 811 (having terminals P1, P2 and P3) forms a ring shape, substantially surrounding the second inductor winding 815 (having terminals P4, P5, P6), and the second inductor winding 815 forms an 8-shaped pattern, so that a current can be induced in the first inductor winding 811.

[0145] Fig.11a and 11b Shows Figure 8 The second advantageous arrangement of the first inductor winding 811 and the second inductor winding 815 of the injection locked oscillator 800 can reduce the parasitic capacitor transmitted to the first inductor winding 811 of the oscillation circuit 820 .

[0146] Fig.11a The arrangement shown adopts a three-wire parallel winding arrangement, wherein the inductor winding 811 of the LC resonant circuit 820 includes a first inductor winding portion 1101 and a second inductor winding portion 1103 .

[0147] Fig.11b A second example of how to form the first inductor winding 811 and the second inductor winding 815 respectively using one or more ultra-thick metal layers in CMOS technology is provided. Fig.11b In the arrangement shown, the inductor winding 815 (having terminals P1, P2 and P3) of the injection circuit forms a ring winding around the first inductor winding portion 1101 (having terminals P4, P5) and the second inductor winding portion 1103 (having terminals P6, P7) so that it basically surrounds the first inductor winding portion 1101 and the second inductor winding portion 1103.

[0148] Although Fig.11b Although shown as surrounding the first inductor winding portion 1101 and the second inductor winding portion 1103, in some embodiments, the inductor winding 815 of the injection circuit can be arranged to be vertically offset relative to the first inductor winding portion 1101 and the second inductor winding portion 1103, for example, in a stacked configuration. For example, the first inductor winding portion 1101 and the second inductor winding portion 1103 can be arranged in the first layer, and the inductor winding 815 can be arranged in the second layer. In this embodiment, it is not required that the inductor winding 815 of the injection circuit surround the first inductor winding portion 1101 and the second inductor winding portion 1103, and it is only required to induce current in the first inductor winding portion 1101 and the second inductor winding portion 1103 of the inductor winding 811 of the LC resonant circuit.

[0149] from Fig.11bAs can be seen from the figure, the first inductor winding portion 1101 and the second inductor winding portion 1103 are arranged in an eight-shaped shape, including respective first loops and second loops, and are intertwined, so that the second loop of the first inductor winding portion 1101 (such as Fig.11b The smaller loop shown in FIG. 11 is surrounded by the first loop of the second inductor winding portion 1103, while the first loop of the first inductor winding 1101 (i.e. Fig.11b 815 ) surrounds a second loop of the second inductor winding portion 1103. However, it is understood that the first inductor winding portion 1101 and the second inductor winding portion 1103 can be arranged in a concentric figure eight shape instead, so that the figure eight shape formed by the first inductor winding portion 1101 is substantially surrounded by the figure eight shape formed by the second inductor winding portion 1103, and vice versa. Similarly, two figure eight windings can be formed in a stacked form in separate layers. It is understood that in other embodiments, one of the figure eight windings can be formed in the same layer in a cocircular arrangement with the loop winding 815, for example, the ring winding surrounds the figure eight winding.

[0150] In this arrangement, the current in the inductor winding 815 generates corresponding induced currents in the first inductor winding portion 1101 and the second inductor winding portion 1103 , which together form the inductor winding 811 of the LC resonant circuit 820 .

[0151] Those skilled in the art will appreciate that the present invention is illustrated by describing one or more specific embodiments, but is not limited to these embodiments; the present invention may be subject to many variations and modifications within the scope of the appended claims.

Claims

1. An electronic oscillator circuit comprising: A resonant circuit comprising a first inductor winding and a capacitor; as well as an injection circuit, comprising a second inductor winding and a current controller; wherein the injection circuit is not electrically connected to the resonant circuit; wherein the current controller is configured such that when the current controller is in a first state, the injection current flows from the current controller through the second inductor winding; wherein the current controller is configured such that when the current controller is in the second state, no injection current flows through the second inductor winding; as well as The first inductor winding and the second inductor winding are coupled, so that an injected current in the second inductor winding of the injection circuit induces a corresponding injected current in the first inductor winding of the resonant circuit.

2. The electronic oscillator of claim 1, wherein the first inductor winding comprises a first winding portion and a second winding portion; wherein the first winding portion is connected between the first side of the resonant circuit and the center terminal; wherein the second winding portion is connected between the second side of the resonant circuit and the center terminal; wherein the induced current in the first winding portion flows from the center terminal to the first side of the resonant circuit; as well as The induced current in the second winding portion flows from the second side of the resonant circuit to the center terminal.

3. An electronic oscillator as claimed in claim 1 or 2, wherein the current controller is a PMOS transistor arranged so that the source of the PMOS transistor is connected to a power supply rail or other current supply; wherein the first terminal and the second terminal of the second inductor winding are connected to ground or another current sink; as well as The third terminal of the second inductor winding is connected to the drain of the PMOS transistor.

4. An electronic oscillator as claimed in claim 1 or 2, wherein the current controller is an NMOS transistor arranged so that the source of the NMOS transistor is connected to ground or other current sink; wherein the first terminal and the second terminal of the second inductive winding are connected to a power supply rail or other current supply; and wherein the third terminal of the second inductor winding is connected to the drain of the NMOS transistor; The third terminal is a center tap of the second inductor winding.

5. An electronic oscillator circuit as claimed in any preceding claim, further comprising a first cross-coupled pair circuit connected to the resonant circuit.

6. An electronic oscillator circuit as claimed in claim 5, wherein the first cross-coupled pair circuit comprises a cross-coupled pair of PMOS transistors, the source of each PMOS transistor being connected to a power supply rail or other current supply.

7. An electronic oscillator circuit as claimed in any preceding claim, further comprising a second cross-coupled pair circuit connected to the resonant circuit.

8. An electronic oscillator circuit as claimed in claim 7, wherein the second cross-coupled pair circuit comprises a cross-coupled pair of NMOS transistors, the source of each NMOS transistor being connected to ground or other current sink.

9. An electronic oscillator circuit as described in any of the preceding claims, further comprising an injection clock source, wherein the injection clock source is configured to apply a clock signal to a current controller in the injection circuit with a predetermined duty cycle, so that the current controller transitions from the second state to the first state at a frequency set by the duty cycle.

10. An electronic oscillator as claimed in claim 9, wherein the injection clock source is configured to cause the current controller to transition from the second state to the first state at a frequency close to the resonant frequency of the resonant circuit or having a harmonic component close to the resonant frequency of the resonant circuit.

11. An electronic oscillator as claimed in any preceding claim, wherein the capacitor and the inductive winding are connected in parallel in the resonant circuit.

12. An electronic oscillator as claimed in any preceding claim, wherein the capacitor is one of a switchable capacitor bank.

13. An electronic oscillator as claimed in any preceding claim, wherein the capacitor is a variable capacitor.

14. An electronic oscillator circuit comprising: a resonant circuit (720) comprising an inductor and a capacitor, wherein each of the inductor and the capacitor has a first terminal connected to a first side of the resonant circuit and a second terminal connected to a second side of the resonant circuit; a first current controller (760); and A second current controller (770); wherein the first current controller (760) is connected to the first side of the resonant circuit (720); wherein the second current controller (770) is connected to the second side of the resonant circuit (720); wherein the first current controller (760) is arranged so that it can act as a current source for the resonant circuit; wherein the second current controller (770) is arranged so that it can act as a current sink of the resonant circuit; wherein the first current controller (760) and the second current controller (770) are configured such that when the first current controller (760) and the second current controller (770) are in a first state, the injection current flows from the first current controller to the second current controller through the resonant circuit (720); as well as When the first current controller (760) and the second current controller (770) are in the second state, no current is injected into the resonant circuit (720).

15. The electronic oscillator of claim 14, wherein the first current controller is a PMOS transistor and the second current controller is an NMOS transistor.

16. An electronic oscillator circuit as claimed in claim 14 or 15, further comprising a first cross-coupled pair circuit connected to the resonant circuit.

17. An electronic oscillator circuit as claimed in claim 16, wherein the first cross-coupled pair circuit comprises a cross-coupled pair of PMOS transistors, the source of each PMOS transistor being connected to a power supply rail or other current supply.

18. An electronic oscillator circuit as claimed in any one of claims 14 to 17, further comprising a second cross-coupled pair circuit connected to the resonant circuit.

19. An electronic oscillator as claimed in claim 18, wherein the second cross-coupled pair circuit comprises a cross-coupled pair of NMOS transistors, the source of each NMOS transistor being connected to ground or other current sink.

20. The electronic oscillator circuit of any one of claims 14 to 19, further comprising an injection clock source, wherein the injection clock source is configured to apply a clock signal to the first current controller and the second current controller at a predetermined duty cycle, so that the first current controller and the second current controller transition from the second state to the first state at a frequency set by the duty cycle of the injection clock source.

21. The electronic oscillator of claim 20, wherein the injection clock source is configured to cause the first current controller and the second current controller to transition from the second state to the first state at a frequency close to the resonant frequency of the resonant circuit or having a harmonic component close to the resonant frequency of the resonant circuit.

22. An electronic oscillator as claimed in any one of claims 14 to 21, wherein the capacitor and the inductor are connected in parallel in the resonant circuit.

23. An electronic oscillator as claimed in any one of claims 14 to 22, wherein the capacitor is one of a switchable capacitor bank.

24. An electronic oscillator as claimed in any one of claims 14 to 23, wherein the capacitor is a variable capacitor.

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