A circuit and method for broadening the locking range of an injection-locked oscillator
The described circuit enhances the lock-in range of injection-locked oscillators by selecting the most stable oscillator based on lock detection, addressing instability due to PVT variations, ensuring stable clock signals without increased power consumption.
Patent Information
- Application Number
- CN202111197412.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-10-14
- Publication Date
- 2025-07-15
- Estimated Expiration
- 2041-10-14
AI Technical Summary
The locking range of the injection locked oscillator is small, and it is impossible to maintain a stable locking within the range of the free oscillation frequency of the on-chip oscillator, resulting in unstable clock signal.
N injection locked oscillators and lock detectors with different free oscillation frequencies are used to judge the locking situation through the self-sampler and alignment monitor, turn off the unlocked oscillator, select the most stable oscillator output clock signal, and widen the locking range.
Without increasing power consumption, the locking range of the injection locked oscillator is broadened, and a stable locking of the frequency changes of the on-chip oscillator is achieved, providing a stable clock signal.
Smart Images
Figure CN114124086B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of oscillators, and relates to a circuit and method for broadening the locking range of an injection-locked oscillator. Background Art
[0002] Generally, a frequency signal is required in a chip circuit for the clock of the circuit, or the local oscillator signal, carrier generation signal, etc. of a communication circuit. In the CMOS (Complementary Metal-Oxide Semiconductor) process, due to the deviation of PVT, the free oscillation frequency of the on-chip oscillator will change, and a clock with the required frequency cannot be obtained. Currently, for the frequency signal required in the chip circuit, using an injection-locked oscillator is a common method. The injection-locked oscillator follows a reference signal with a specific frequency to obtain a high-precision clock signal. However, due to the small locking range of injection locking, the on-chip oscillator can only be locked to the target frequency by the reference signal when its free oscillation is near the frequency of the reference signal. Generally, the locking range of injection locking is much lower than the free oscillation frequency change range caused by PVT. Therefore, when the free oscillation frequency exceeds the locking range, the oscillator cannot be locked by the reference signal, and at this time, the reference signal instead has a negative impact on the oscillator, reducing the stability of the clock. Summary of the Invention
[0003] In order to solve the above technical problems existing in the prior art, the present invention provides a circuit and method for broadening the locking range of an injection-locked oscillator, and the specific technical solutions are as follows:
[0004] A circuit for broadening the locking range of an injection-locked oscillator includes: N injection-locked oscillators and a locking detector, where N≥2, and the locking detector includes: an alignment monitor, a clock selector, and N self-samplers. A pulse reference signal is input into the N injection-locked oscillators. The output of each injection-locked oscillator is connected to the clock selector and the corresponding self-sampler. The self-sampler samples the output of the N injection-locked oscillators injected with the pulse reference signal using the pulse reference signal, and outputs the sampling result to the alignment monitor. The alignment monitor monitors the sampling result of the self-sampler, judges the locking situation of the injection-locked oscillator, and turns off the unlocked oscillator. The clock selector selects the locked oscillator. After the detection is completed, the locking detector stops working, and the clock selector transmits the clock signal output by the locked oscillator to the system.
[0005] Further, the pulse reference signal has a target frequency and provides a reference clock for the injection-locked oscillator.
[0006] Further, the injection-locked oscillator includes an oscillator and an injection stage. The pulsed reference signal is connected to the oscillator through the injection stage. The free oscillation frequencies of the oscillators are different, where the free oscillation frequencies of some oscillators are less than the frequency of the pulsed reference signal, and some are greater than the frequency of the pulsed reference signal. When PVT changes, the free oscillation frequencies of the N oscillators are simultaneously affected and increase or decrease.
[0007] Further, the N self-samplers use the falling edge of the pulsed reference signal as the clock to sample the outputs of the N injection-locked oscillators respectively. According to the self-alignment property of injection locking, if the oscillator is locked, the pulsed reference signal shapes the edge of the oscillator output. When the free oscillation frequency is lower than the frequency of the pulsed reference signal, the pulsed reference signal will self-align the rising edge of the oscillator output, and a high level is sampled. When the free oscillation frequency is higher than the frequency of the pulsed reference signal, the pulsed reference signal will self-align the falling edge of the oscillator output, and a low level is sampled. If the oscillator is not locked, the pulsed reference signal cannot shape the edge of the oscillator output, and the sampling result will have a jump.
[0008] Further, the alignment monitor monitors the sampling results of the self-samplers to determine whether the injection-locked ring oscillator is locked. The alignment monitor consists of several finite-bit counters. When the most significant bit of one of the counters jumps to 1, it is determined that the oscillator is not locked. At this time, the unlocked oscillator is turned off. When N - 1 oscillators are determined to be unlocked, the judgment ends, and the alignment monitor stops working.
[0009] Further, the clock selector consists of a multiplexer. The output of the alignment monitor is processed and connected to the clock selector. The clock selector selects one of the outputs of the N injection-locked oscillators as the system clock.
[0010] A method for broadening the locking range of an injection-locked oscillator includes the following steps:
[0011] Step 1, for N injection-locked oscillators with different free oscillation frequencies, input a pulsed reference signal with the same target frequency.
[0012] Step 2, based on the self-alignment characteristic of the injection-locked oscillator, the self-sampler samples the outputs of the N injection-locked oscillators of the input pulsed reference signal, and samples the low level or high level when the oscillator is locked, and the sampling result has high and low jumps when the oscillator is not locked.
[0013] Step 3, use the alignment monitor to monitor the sampling results, and according to the sampling results, determine whether the oscillator is locked, and then turn off the unlocked oscillator.
[0014] Step 4, the clock selector selects the locked oscillator and outputs the clock.
[0015] Advantageous effects:
[0016] To improve the locking range of the injection-locked oscillator, the present invention employs N oscillators with different oscillation frequencies. By judging the locking conditions of the N oscillators, the locked and most stable oscillator is selected, and the unlocked oscillators are turned off, enabling the injection-locked oscillator to broaden the locking range without increasing power consumption. This method does not require an external debugging circuit and fully automatically realizes the judgment and selection of injection locking, enabling the locking range to cover the free oscillation frequency variations of the oscillator caused by PVT. Description of the Drawings
[0017] Figure 1 is the circuit schematic diagram of the present invention;
[0018] Figure 2 is the circuit schematic diagram of the embodiment of the present invention. Detailed Embodiments
[0019] In order to make the objectives, technical solutions, and technical effects of the present invention clearer and more understandable, the following further elaborates on the present invention in conjunction with the drawings in the specification.
[0020] As Figure 1 shown, a circuit for broadening the locking range of an injection-locked oscillator includes: N injection-locked oscillators and a locking detector, where N≥2. The locking detector detects the output signals of the N injection-locked oscillators injected with a pulsed reference signal and outputs the required clock signal. The locking detector specifically includes: an alignment monitor, a clock selector, and N self-samplers.
[0021] The pulsed reference signal has a target frequency and provides a reference clock for the injection-locked oscillator. The injection-locked oscillator has different free oscillation frequencies, and after injecting the pulsed reference signal, a clock signal following the pulsed reference signal is generated.
[0022] The injection-locked oscillator includes an oscillator and an injection stage. The pulsed reference signal is connected to the oscillator through the injection stage. The free oscillation frequencies of the oscillators are different, where the free oscillation frequencies of some oscillators are less than the frequency of the pulsed reference signal, and some are greater. When PVT changes, the free oscillation frequencies of the N oscillators are simultaneously affected and increase or decrease.
[0023] A pulse reference signal is input into N injection-locked oscillators with different free oscillation frequencies. The output of each injection-locked oscillator is connected to a clock selector and a corresponding self-sampler. The self-sampler samples the outputs of the N injection-locked oscillators injected with the pulse reference signal using the pulse reference signal and outputs the sampling results to an alignment monitor. The alignment monitor monitors the sampling results of the self-sampler, judges the locking situation of the injection-locked oscillators, and shuts down the unlocked oscillators. After the detection is completed, the locking detector stops working, and the clock selector selects the locked oscillator and transmits the clock signal output by the locked oscillator to the system.
[0024] Embodiment:
[0025] As Figure 2 shown: The circuit of the present invention uses two injection-locked ring oscillators to expand the locking range.
[0026] Each of the injection-locked ring oscillators includes three-stage delay units and an NMOS injection stage. The gate of the NMOS injection stage is connected to the pulse reference signal, the source is grounded, and the drain is connected to the oscillator loop. The free oscillation frequency of the injection-locked ring oscillator 1 is lower than the frequency of the pulse reference signal, and the free oscillation frequency of the injection-locked ring oscillator 2 is higher than the frequency of the pulse reference signal.
[0027] The two self-samplers use the falling edge of the pulse reference signal as the clock to sample the outputs of the two injection-locked ring oscillators respectively. Due to the self-alignment of injection locking, when the free oscillation frequency is lower than the frequency of the pulse reference signal, if the injection-locked ring oscillator is locked, the pulse reference signal will self-align with the rising edge of the output of the injection-locked ring oscillator, and a high level is sampled. When the free oscillation frequency is higher than the frequency of the pulse reference signal, if the injection-locked ring oscillator is locked, the pulse reference signal will self-align with the falling edge of the output of the injection-locked ring oscillator, and a low level is sampled. If the injection-locked ring oscillator is not locked, the sampling result will have a jump.
[0028] The alignment monitor monitors the sampling results of the self-sampler to judge whether the injection-locked ring oscillator is locked. The alignment monitor consists of several finite-bit counters. When the highest bit of one of the alignment monitors jumps to 1, it is determined that the oscillator is not locked. At this time, the unlocked injection-locked ring oscillator is shut down. When N - 1 oscillators are determined to be unlocked, the judgment ends, and the alignment monitor stops working.
[0029] The clock selector consists of a two-to-one data selector. The output of the alignment monitor is connected to the clock selector after being processed. The clock selector selects one of the outputs of the two injection-locked ring oscillators and inputs it to the subsequent circuit.
[0030] In an oscillator circuit, a method for broadening the locking range of an injection-locked oscillator according to the present invention is specifically as follows: two ring oscillators with different free oscillation frequencies are used and are simultaneously locked by a pulsed reference signal. The free oscillation frequency of ring oscillator 1 is lower than the frequency of the pulsed reference signal, while that of ring oscillator 2 is higher than the frequency of the pulsed reference signal. When the circuit is affected by PVT, the free oscillation frequencies of the two ring oscillators change in the same direction. If the frequencies of the two ring oscillators become lower, the free oscillation frequency of ring oscillator 2 will be closer to the reference frequency, while the free oscillation frequency of ring oscillator 1 will move away from the reference frequency. A locking detector is used to detect whether the two ring oscillators are locked. Based on the self-alignment characteristic of the injection-locked ring oscillator, when the oscillator is locked, a self-sampler samples the output of the oscillator by the pulsed reference signal, sampling a low level or a high level; when the oscillator is not locked, the sampling result has high and low jumps. An alignment monitor monitors the sampling result to determine whether the oscillator is locked, and then turns off the unlocked oscillator to stop detection to save power. A clock selector selects the locked oscillator and outputs the clock. This method broadens the injection-locking range to cover the frequency range varying with PVT without increasing the circuit power consumption, achieving stable clock generation with low power consumption.
[0031] The above is only the preferred embodiment of the present invention and does not impose any formal restrictions on the present invention. Although the implementation process of the present invention has been described in detail above, for those skilled in the art, they can still modify the technical solutions described in the foregoing examples or make equivalent replacements for some of the technical features. Any modifications, equivalent replacements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A circuit for broadening the locking range of an injection-locked oscillator, characterized in that Comprising: N injection - locked oscillators and a locking detector, where N≥2. The locking detector includes: an alignment monitor, a clock selector, and N self - samplers. A pulsed reference signal is input into the N injection - locked oscillators. The output of each injection - locked oscillator is connected to the clock selector and the corresponding self - sampler. The self - sampler samples the output of the N injection - locked oscillators injected by the pulsed reference signal using the pulsed reference signal and outputs the sampling result to the alignment monitor. The alignment monitor monitors the sampling results of the self - samplers, judges the locking condition of the injection - locked oscillators, and shuts down the unlocked oscillators. The clock selector selects the locked oscillator and transmits the clock signal output by this oscillator to the system.
2. The circuit for broadening the locking range of an injection-locked oscillator according to claim 1, characterized in that The pulsed reference signal has a target frequency and provides a reference clock for the injection - locked oscillators.
3. A circuit for broadening the locking range of an injection-locked oscillator according to claim 1, characterized in that, The injection - locked oscillator includes an oscillator and an injection stage. The pulsed reference signal is connected to the oscillator through the injection stage. The free - oscillation frequencies of the oscillators are different. Among them, the free - oscillation frequencies of some oscillators are less than the frequency of the pulsed reference signal, and some are greater than the frequency of the pulsed reference signal. When PVT changes, the free - oscillation frequencies of the N oscillators are affected simultaneously and increase or decrease.
4. A circuit for broadening the locking range of an injection-locked oscillator as described in claim 1, characterized in that, The N self - samplers use the falling edge of the pulsed reference signal as the clock to sample the outputs of the N injection - locked oscillators respectively. According to the self - alignment property of injection locking, if the oscillator is locked, the pulsed reference signal shapes the edge of the oscillator output. When the free - oscillation frequency is lower than the frequency of the pulsed reference signal, the pulsed reference signal aligns the rising edge of the oscillator output, and a high level is sampled. When the free - oscillation frequency is higher than the frequency of the pulsed reference signal, the pulsed reference signal aligns the falling edge of the oscillator output, and a low level is sampled. If the oscillator is not locked, the pulsed reference signal cannot shape the edge of the oscillator output, and the sampling result jumps.
5. The circuit for broadening the locking range of an injection-locked oscillator according to claim 1, characterized in that, The alignment monitor monitors the sampling results of the self - samplers to judge whether the injection - locked ring oscillator is locked. The alignment monitor consists of several finite - bit counters. When the most significant bit of one of the counters jumps to 1, it is determined that this oscillator is not locked. At this time, the unlocked oscillator is shut down. When N - 1 oscillators are determined to be unlocked, the judgment ends, and the alignment monitor stops working.
6. The circuit for broadening the locking range of an injection-locked oscillator according to claim 1, characterized in that, The clock selector consists of a multiplexer. The output of the alignment monitor is processed and connected to the clock selector. The clock selector selects one of the outputs of the N injection - locked oscillators as the system clock.
7. A method for broadening the locking range of an injection-locked oscillator, characterized in that, Including the following steps: Step 1: Input the same pulsed reference signal with a target frequency into N injection - locked oscillators with different free - oscillation frequencies. Step 2: Based on the self - alignment characteristic of the injection - locked oscillator, use N self - samplers corresponding to the injection - locked oscillators respectively to sample the outputs of the N injection - locked oscillators input with the pulsed reference signal, and sample the low level or high level when the oscillator is locked, and the sampling result with high - low jumps when the oscillator is not locked. Step 3, use an alignment monitor to monitor the sampling result, and based on the sampling result, determine whether the oscillator is locked, and then turn off the unlocked oscillator; Step 4, the clock selector selects the locked oscillator and outputs the clock.