Injection-locked ring oscillator, BFSK signal demodulation circuit structure and method
By injecting a locked ring oscillator and a BFSK signal demodulation circuit structure, the BFSK signal is directly demodulated, solving the problems of high power consumption and narrow locking range in the prior art, and achieving the effect of low power consumption and wide frequency locking.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHENGDU CHENXIN IOT TECH CO LTD
- Filing Date
- 2026-05-11
- Publication Date
- 2026-07-24
AI Technical Summary
Existing BFSK signal demodulation circuits are complex in structure, require high-power modules, and have a narrow lock-in range, making it difficult to handle wide-band offset BFSK signals and resist PVT bias.
An injection-locked ring oscillator is used to convert external radio frequency signals into differential current through an injection stage. The ring oscillator and envelope detector circuit are combined to directly demodulate the BFSK signal. Frequency adjustment and locking are achieved using a switching network and a delay unit.
It reduces power consumption, simplifies design complexity, expands the locking range, and improves anti-interference capabilities, making it suitable for low-power IoT applications.
Smart Images
Figure CN122456987A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wireless communication technology, and in particular to an injection-locked ring oscillator, a BFSK signal demodulation circuit structure and method. Background Technology
[0002] In the era of the Internet of Things, wireless communication systems with long range, low power consumption, and low cost have become particularly important. Traditional receiver architectures are roughly divided into three types: superheterodyne receivers, zero-IF receivers, and low-IF receivers. These traditional architectures all require down-conversion operations to reduce the complexity of subsequent sampling and demodulation circuits. Therefore, they require high-power modules such as mixers and phase-locked loops, which greatly increases the power consumption of the receiver.
[0003] In recent years, research on injection-locked technology has shown that oscillators respond differently to different injection signals. Therefore, utilizing the amplitude characteristics of the oscillator to directly demodulate BFSK modulated signals in the RF domain not only avoids down-conversion and other operations, reducing system complexity, but also reduces the use of modules such as mixers, meeting the low-power requirements of IoT applications. However, existing BFSK demodulation methods based on LC oscillators still have limitations. The on-chip inductors required in the LC structure occupy a large chip area, which is not conducive to the miniaturization and high integration design of the system. In addition, the narrow locking range of LC oscillators also limits their ability to process wide-band offset BFSK signals, making it difficult to resist the influence of PVT deviation without adding additional calibration circuitry.
[0004] Therefore, an injection-locked ring oscillator and a BFSK signal demodulation circuit structure and method were developed to solve the above problems. Summary of the Invention
[0005] This invention proposes an injection-locked ring oscillator, a BFSK signal demodulation circuit structure and method to solve the problems of complex structure and high accuracy requirements of existing BFSK signal demodulation circuits.
[0006] The present invention achieves the above objectives through the following technical solutions: In a first aspect, the present invention provides an injection-locked ring oscillator, comprising: The injection stage is used to receive external radio frequency signals and convert them into differential current. A ring oscillator includes a switch and seven delay units connected end-to-end. The switch is used to switch the number of delay units between five and seven stages. The differential output of the injection stage is connected to the differential input of the ring oscillator.
[0007] Furthermore, the ring oscillator includes seven delay units connected end to end. The input terminal of the switch is connected to the output terminal of the fourth delay unit, and the output terminal of the switch is switched between the input terminal of the fifth delay unit and the input terminal of the seventh delay unit.
[0008] Furthermore, the differential output of the injection stage is connected to the differential input of the fourth-stage delay unit of the ring oscillator.
[0009] Furthermore, the differential output of the injection stage is connected to the differential input of the ring oscillator via a coupling capacitor.
[0010] Furthermore, the injection stage includes an AC coupling capacitor, a first input NMOS differential pair, a current source load PMOS pair, and a first tail current source transistor. The AC coupling capacitor is connected to the gate of the NMOS differential pair, the source of the current source load PMOS pair is connected to the power supply, the drain of the current source load PMOS pair is connected to the drain of the first input NMOS differential pair, the drain of the first tail current source transistor is connected to the source of the first input NMOS differential pair, and the source of the first input NMOS differential pair is grounded.
[0011] Furthermore, the delay unit includes a pair of tuning capacitors, a second input NMOS differential pair, a resistive load, and a second tail current source transistor. One end of the resistive load is connected to the power supply, and the other end of the resistive load is connected to the drain of the second input NMOS differential pair. The drain of the second tail current source transistor is connected to the source of the second input NMOS differential pair, and the source of the second input NMOS differential pair is grounded. One end of each of the two tuning capacitors in the tuning capacitor pair is connected to the other end, and the other ends are respectively connected to the drain of the second input NMOS differential pair to form a tuning capacitor pair.
[0012] Secondly, the present invention also discloses a BFSK signal demodulation circuit structure, comprising: Low-noise amplifier; the low-noise amplifier is used to receive BFSK signals. A voltage-controlled amplifier, the input of which is connected to the signal output of a low-noise amplifier; An injection-locked ring oscillator, wherein the injection-locked ring oscillator is one type of injection-locked ring oscillator, and the output terminal of the voltage-controlled amplifier is connected to the input terminal of the injection-locked ring oscillator; Envelope detection circuit, the input terminal of which is connected to the output terminal of injection-locked ring oscillator; The baseband circuit has its input terminal connected to the output terminal of the envelope detector circuit.
[0013] Thirdly, the present invention also discloses a BFSK signal demodulation method, comprising: The BFSK signal is processed by a low-noise amplifier and a voltage-controlled amplifier to obtain the FSK signal. The FSK signal is injected into the ring oscillator through the injection stage in the injection-locked ring oscillator, which is the injection-locked ring oscillator described above, and outputs the ASK signal. The baseband data envelope can be directly obtained by envelope detection of the ASK signal; The final demodulated data is then obtained by amplification and quantization using baseband circuitry.
[0014] Furthermore, after the FSK signal is injected into the ring oscillator through the injection stage in the injection-locked ring oscillator, the following operations are performed: The switching network in the ring oscillator is controlled to switch between the fifth-stage delay unit and the seventh-stage delay unit to complete the free oscillation frequency adjustment and achieve coarse frequency modulation; By adjusting the load capacitance of each delay unit, the free oscillation frequency can cover the BFSK signal frequency, thus achieving fine frequency tuning in the same mode. When the external radio frequency approaches the free oscillation frequency, the injected current provides a phase reference within the ring oscillator and pulls the flip-off time of each stage of the delay unit, and the loop enters lockout.
[0015] The beneficial effects of this invention are as follows: The proposed injection-locked ring oscillator, BFSK signal demodulation circuit structure and method have a simple architecture and significantly reduced power consumption; no precise local oscillator and coherent phase-locked loop are required, reducing design and calibration complexity; the locking bandwidth and injection strength are adjustable, and sensitivity and anti-interference capability can be balanced according to the scenario; the locking establishment is fast and the end-to-end latency is low, making it suitable for wake-up and intermittent communication. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of a BFSK signal demodulation circuit structure in an embodiment of this application; Figure 2 This is a schematic diagram of the circuit structure of the ring oscillator in the embodiments of this application; Figure 3 This is a schematic diagram of the circuit structure of the injection stage in an embodiment of this application; Figure 4 This is a schematic diagram of the circuit result of the delay unit in the embodiment of this application; Figure 5 This is a schematic diagram illustrating the relationship between the amplitude of the ring oscillator and the injection frequency in an embodiment of this application. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0018] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0019] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0020] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0021] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.
[0022] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0023] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0024] The present invention provides an injection-locked ring oscillator, comprising: The injection stage is used to receive external radio frequency signals and convert them into differential current. A ring oscillator includes a switch and seven delay units connected end-to-end. The switch is used to switch the number of delay units between five and seven stages. The differential output of the injection stage is connected to the differential input of the ring oscillator.
[0025] like Figure 2 As shown, in one embodiment, the ring oscillator includes seven delay units connected end to end. The input terminal of the switch is connected to the output terminal of the fourth delay unit, and the output terminal of the switch is switched between the input terminal of the fifth delay unit and the input terminal of the seventh delay unit.
[0026] In one embodiment, the differential output of the injection stage is connected to the differential input of the fourth-stage delay unit of the ring oscillator.
[0027] In one embodiment, the differential output of the injection stage is connected to the differential input of the ring oscillator via a coupling capacitor.
[0028] like Figure 3 As shown, in one embodiment, the injection stage includes an AC coupling capacitor, a first input NMOS differential pair, a current source load PMOS pair, and a tail current source transistor. The input signal is connected to the gate of the first input NMOS differential pair through the AC coupling capacitor. The source of the current source load PMOS pair is connected to a power supply, and its drain is connected to the drain of the NMOS differential pair. The drain of the tail current source transistor is connected to the source of the first input NMOS differential pair, and its source is grounded.
[0029] like Figure 4 As shown, in one embodiment, the delay unit includes a pair of tuning capacitors, a second input NMOS differential pair, a resistive load, and a tail current source transistor. One end of the resistive load is connected to a power supply, and the other end is connected to the drain of the second input NMOS differential pair. The drain of the tail current source transistor is connected to the source of the second input NMOS differential pair, and the source is grounded. Two tuning capacitors are connected at one end and their other ends are respectively connected to the drains of the second input NMOS differential pair to form a tuning capacitor pair.
[0030] like Figure 1 As shown, a BFSK signal demodulation circuit structure includes: Low-noise amplifier; the low-noise amplifier is used to receive BFSK signals. A voltage-controlled amplifier, the input of which is connected to the signal output of a low-noise amplifier; An injection-locked ring oscillator, wherein the injection-locked ring oscillator is one type of injection-locked ring oscillator, and the output terminal of the voltage-controlled amplifier is connected to the input terminal of the injection-locked ring oscillator; Envelope detection circuit, the input terminal of which is connected to the output terminal of injection-locked ring oscillator; The baseband circuit has its input terminal connected to the output terminal of the envelope detector circuit.
[0031] like Figure 1 As shown, the BFSK signal is processed by a low-noise amplifier and a voltage-controlled amplifier and then injected into a ring oscillator, thereby converting the BFSK signal into an ASK signal. The baseband data envelope can be directly obtained through envelope detection, and finally the baseband circuit amplifies and quantizes to obtain the final demodulated data.
[0032] The present invention also provides a BFSK signal demodulation method, comprising: The BFSK signal is processed by a low-noise amplifier and a voltage-controlled amplifier to obtain the FSK signal. The FSK signal is injected into the ring oscillator through the injection stage in the injection-locked ring oscillator, which is the injection-locked ring oscillator described above, and outputs the ASK signal. The baseband data envelope can be directly obtained by envelope detection of the ASK signal; The final demodulated data is then obtained by amplification and quantization using baseband circuitry.
[0033] In one embodiment, after the FSK signal is injected into the ring oscillator through the injection stage in the injection-locked ring oscillator, the following operations are performed: The switching network in the ring oscillator is controlled to switch between the fifth-stage delay unit and the seventh-stage delay unit to complete the free oscillation frequency adjustment and achieve coarse frequency modulation; By adjusting the tuning voltage of the tuning capacitor pair, the load capacitance of each delay unit is changed, thereby adjusting the free oscillation frequency to cover the BFSK signal frequency, achieving fine frequency tuning in the same mode. When the external radio frequency approaches the free oscillation frequency, the injected current provides a phase reference within the ring oscillator and pulls the flip-off time of each stage of the delay unit, and the loop enters lockout.
[0034] The working principle of this invention for BSK signal demodulation is as follows: This injection-locked ring oscillator consists of an injection stage and a differential ring oscillator with switchable stages. The injection stage uses a differential amplifier with a current source load. External RF signals are converted into differential currents within the injection stage and then injected into the differential nodes of the ring oscillator through coupling capacitors. Due to capacitive coupling and a high-impedance load, external signals primarily act on the AC path, resulting in a stable DC operating point, high injection efficiency, and a wider locking range. The bias voltage and tail current jointly set the injection stage gain and linearity, allowing adjustment of the injection strength without altering the loop DC, providing a margin for subsequent FSK locking.
[0035] The ring oscillator consists of multiple differential delay units with resistive loads connected end-to-end. The switching network switches between five and seven stages to perform coarse frequency tuning. Fewer stages result in a higher free oscillation frequency; more stages result in a lower free oscillation frequency. Further fine-tuning is achieved within the same mode by adjusting the load capacitance at each stage, allowing the free oscillation frequency to cover the target two FSK frequency points and their drift range. This provides a wider operating bandwidth between low-frequency and high-frequency modes.
[0036] When the external RF frequency approaches the free oscillation frequency f0, the injected current provides a phase reference within the loop and pulls the flip-off times of each stage, causing the loop to enter lockout. After lockout, phase jitter and beat frequency are significantly reduced, and the output envelope is stable; when deviating from the lockout band, pulling occurs, and amplitude modulation occurs. Utilizing the amplitude difference in the lockout state, FSK can be converted to ASK: when the input is keyed between high and low frequencies, the loop oscillator presents two stable envelope levels respectively, and the bit sequence can be recovered by comparing the subsequent envelope detection with the threshold.
[0037] Figure 5 As shown, when a signal is injected into a freely oscillating oscillator, two states will occur. If the injection strength is high enough, the oscillator will lock at the injection frequency f. inj This is referred to as the locked state. If the injected signal strength is insufficient to lock the oscillator, a modulation effect will occur. This structure utilizes the locked state; when two injected signals of different frequencies both lock the oscillator, the oscillator's ring eigenvalue amplitude A0 and the injected frequency f... inj The relationship is decreasing. If the received BFSK signal is injected into a ring oscillator, the FSK signal can be converted into an ASK signal, which can then be demodulated by direct detection.
[0038] The advantages of this invention compared to the prior art are as follows: 1. The architecture is simple and power consumption is significantly reduced.
[0039] This invention uses an injection-locked ring oscillator as the demodulation core. The received binary frequency shift keying signal is directly injected into the oscillator after passing through a low-noise amplifier and a voltage-controlled amplifier. The mapping from frequency to amplitude is completed in the radio frequency domain, and the baseband data is obtained through envelope detection. There is no need for high-power modules such as mixers and phase-locked loops, the link is greatly simplified, and the standby and operating power consumption is significantly reduced, making it suitable for battery-powered and energy-harvesting IoT terminals.
[0040] 2. No need for precise local oscillators and coherent phase-locked loops, reducing design and calibration complexity.
[0041] This invention relies on an injection locking mechanism to pull the oscillator into a locked state using an external carrier, no longer depending on the precise frequency and phase recovery loop of the local oscillator. This fundamentally avoids problems such as frequency synthesis phase synchronization and in-phase, positive cross-channel imbalance, and zero intermediate frequency DC bias. The startup time is shortened, and the requirements for factory and field calibration due to process voltage and temperature changes are significantly reduced.
[0042] 3. Adjustable locking bandwidth and injection strength; sensitivity and anti-interference capability can be balanced according to the scenario.
[0043] This invention allows for the setting of lock-in bandwidth and amplitude slope relative to frequency by adjusting the gain of the voltage-controlled amplifier and the bias and delay parameters of the ring oscillator. In weak signal scenarios, injection is increased to enhance lock-in and amplitude contrast, while in interference-intensive scenarios, the effective response is appropriately narrowed to improve selectivity.
[0044] 4. Locking establishes fast end-to-end latency, suitable for wake-up and intermittent communication.
[0045] The establishment time of the injection lock in this invention is much shorter than that of the traditional phase-locked loop lock. The subsequent stage uses a simulated envelope path, resulting in low link latency. This makes it suitable for short data packets, low duty cycle operation, and fast wake-up strategies, thereby further reducing the average power consumption of the system and improving the response speed of event-driven applications.
[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. An injection-locked ring oscillator, characterized in that, include: The injection stage is used to receive external radio frequency signals and convert them into differential current. A ring oscillator includes a switch and seven delay units connected end-to-end. The switch is used to switch the number of delay units between five and seven stages. The differential output of the injection stage is connected to the differential input of the ring oscillator.
2. The injection-locked ring oscillator according to claim 1, characterized in that, The ring oscillator includes seven delay units connected end to end. The input terminal of the switch is connected to the output terminal of the fourth delay unit, and the output terminal of the switch is switched between the input terminal of the fifth delay unit and the input terminal of the seventh delay unit.
3. The injection-locked ring oscillator according to claim 2, characterized in that, The differential output of the injection stage is connected to the differential input of the fourth-stage delay unit of the ring oscillator.
4. An injection-locked ring oscillator according to claim 1 or 2, characterized in that, The differential output of the injection stage is connected to the differential input of the ring oscillator via a coupling capacitor.
5. The injection-locked ring oscillator according to claim 1, characterized in that, The injection stage includes an AC coupling capacitor, a first input NMOS differential pair, a current source load PMOS pair, and a first tail current source transistor. The AC coupling capacitor is connected to the gate of the NMOS differential pair, the source of the current source load PMOS pair is connected to the power supply, the drain of the current source load PMOS pair is connected to the drain of the first input NMOS differential pair, the drain of the first tail current source transistor is connected to the source of the first input NMOS differential pair, and the source of the first input NMOS differential pair is grounded.
6. The injection-locked ring oscillator according to claim 1, characterized in that, The delay unit includes a tuning capacitor pair, a second input NMOS differential pair, a resistive load, and a second tail current source transistor. One end of the resistive load is connected to the power supply, and the other end of the resistive load is connected to the drain of the second input NMOS differential pair. The drain of the second tail current source transistor is connected to the source of the second input NMOS differential pair, and the source of the second input NMOS differential pair is grounded. One end of each of the two tuning capacitors in the tuning capacitor pair is connected to the other end, and the other end is connected to the drain of the second input NMOS differential pair respectively to form a tuning capacitor pair.
7. A BFSK signal demodulation circuit structure, characterized in that, include: Low-noise amplifier; the low-noise amplifier is used to receive BFSK signals. A voltage-controlled amplifier, the input of which is connected to the signal output of a low-noise amplifier; An injection-locked ring oscillator, wherein the injection-locked ring oscillator is an injection-locked ring oscillator as described in any one of claims 1-6, and the output terminal of the voltage-controlled amplifier is connected to the input terminal of the injection-locked ring oscillator; Envelope detection circuit, the input terminal of which is connected to the output terminal of injection-locked ring oscillator; The baseband circuit has its input terminal connected to the output terminal of the envelope detector circuit.
8. A BFSK signal demodulation method, characterized in that, include: The BFSK signal is processed by a low-noise amplifier and a voltage-controlled amplifier to obtain the FSK signal. The FSK signal is injected into the ring oscillator through the injection stage in the injection-locked ring oscillator, which is an injection-locked ring oscillator as described in any one of claims 1-6, and outputs the ASK signal; The baseband data envelope can be directly obtained by envelope detection of the ASK signal; The final demodulated data is then obtained by amplification and quantization using baseband circuitry.
9. A BFSK signal demodulation method according to claim 8, characterized in that, After the FSK signal is injected into the ring oscillator through the injection stage in the injection-locked ring oscillator, the following operations are performed: The switching network in the ring oscillator is controlled to switch between the fifth-stage delay unit and the seventh-stage delay unit to complete the free oscillation frequency adjustment and achieve coarse frequency modulation; By adjusting the tuning voltage of the tuning capacitor pair, the load capacitance of each delay unit is changed, thereby adjusting the free oscillation frequency to cover the BFSK signal frequency, achieving fine frequency tuning in the same mode. When the external radio frequency approaches the free oscillation frequency, the injected current provides a phase reference within the ring oscillator and pulls the flip-off time of each stage of the delay unit, and the loop enters lockout.