Phase-locked loop circuit
By using a switching module to switch the connection between the phase detector or the preset voltage module and the loop filter module in the phase-locked loop circuit, the problem of phase noise introduced by the preset voltage is solved, and the phase-locked loop can be fast locked and its stability is improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHENZHEN CITY SIGLENT TECH
- Filing Date
- 2026-04-15
- Publication Date
- 2026-05-15
AI Technical Summary
Preset voltage introduces phase noise, affecting the phase noise performance of the phase-locked loop system.
By switching the phase detector or the preset voltage module with the loop filter module, phase noise can be introduced by the preset voltage module, voltage fluctuations in the loop filter module can be reduced, and the stability of the phase-locked loop can be improved.
This reduces the locking time of the phase-locked loop (PLL), avoids loop instability and parameter changes, and improves the stability and phase noise performance of the PLL.
Smart Images
Figure CN122052777A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of phase-locked loop (PLL) technology, specifically to a PLL circuit. Background Technology
[0002] With the continuous development of communication technology, electronic devices are placing increasingly higher demands on circuit performance, especially in terms of phase noise, which affects signal demodulation and modulation. Currently, phase-locked loops (PLLs) rely on frequency dividers to multiply the frequency, but at high frequencies, the phase noise is not particularly excellent due to the noise floor limitations of the frequency divider and phase detector. Therefore, PLLs replace frequency dividers with mixers, which not only eliminates the noise floor of the frequency divider but also allows the phase detector to achieve a better noise floor, significantly improving the output phase noise.
[0003] Mixing introduces a lot of harmonics and spurious signals, which can easily lead to false locking or loss of lock-in. Therefore, the mixing phase-locked loop needs an additional preset voltage to be preset to near the desired frequency so that the phase-locked loop can capture and lock normally.
[0004] Current technical solutions primarily rely on preset voltages from the DAC output. However, this introduces phase noise from the preset circuit, degrading the system's phase noise. Therefore, new technical solutions are needed. Summary of the Invention
[0005] The main technical problem this application addresses is that the preset voltage introduces phase noise.
[0006] According to the first aspect, one embodiment provides a phase-locked loop circuit, including a phase detector, a mixer module, a loop filter module, a voltage-controlled oscillator, a preset voltage module, and a switching module;
[0007] The voltage-controlled oscillator is used to generate an output signal of a corresponding frequency according to the input voltage;
[0008] The mixing module is used to perform mixing processing on the output signal to obtain a mixed signal;
[0009] The phase detector is used to receive the reference signal and the mixed signal, and output a phase control signal according to the phase difference between the reference signal and the mixed signal;
[0010] The preset voltage module is used to control the loop filter module to output a preset voltage;
[0011] The switching module is used to connect the phase detector or the preset voltage module to the loop filter module; wherein...
[0012] When it is necessary to preset the voltage of the voltage-controlled oscillator, the switching module connects the preset voltage module to the loop filter module. The preset voltage module controls the loop filter module to output a preset voltage, and the voltage-controlled oscillator can generate the output signal of a preset frequency according to the preset voltage.
[0013] After voltage pre-conditioning of the voltage-controlled oscillator is completed, the switching module connects the phase detector to the loop filter module. The loop filter module receives the phase control signal, filters the phase control signal, and outputs a phase control voltage. The voltage-controlled oscillator can generate an output signal that is synchronized with the frequency of the reference signal according to the phase control voltage.
[0014] In some embodiments, the loop filter module includes an active filter circuit configured to be connected to a reference voltage;
[0015] When the switching module connects the preset voltage module to the loop filter module, the preset voltage module is used to obtain the voltage output by the active filter circuit, and to perform feedback control on the active filter circuit according to the voltage output by the active filter circuit, so that the active filter circuit outputs the preset voltage under the reference voltage.
[0016] When the switching module connects the phase detector to the loop filter module, the active filter circuit filters the phase control signal and outputs the phase control voltage.
[0017] or,
[0018] The loop filter module includes a passive filter circuit. When the switch module connects the preset voltage module to the loop filter module, the preset voltage module is used to output a preset voltage to the loop filter module, so that the passive filter circuit filters the preset voltage and outputs the preset voltage.
[0019] When the switching module connects the phase detector to the loop filter module, the passive filter circuit filters the phase control signal and outputs the phase control voltage.
[0020] In some embodiments, when the loop filter module includes an active filter circuit, the preset voltage module includes a voltage output source, an adder circuit, and a voltage sampling circuit.
[0021] The voltage output source is used to output a preset voltage;
[0022] The voltage sampling circuit is used to obtain the voltage output by the active filter circuit;
[0023] The adder circuit receives the preset voltage and the voltage output by the active filter circuit respectively, performs summation processing, and outputs the summed voltage to the active filter circuit.
[0024] The active filter circuit outputs the preset voltage based on the summed voltage and the reference voltage; wherein the preset voltage and the preset voltage have a preset relationship.
[0025] In some embodiments, the active filter circuit includes a first operational amplifier and a first filter circuit;
[0026] The first input terminal of the first operational amplifier receives the reference voltage, the second input terminal receives the voltage output by the preset voltage module, and the first filter circuit is connected in parallel between the second input terminal and the output terminal of the first operational amplifier.
[0027] When the switching module connects the preset voltage module to the loop filter module, the first operational amplifier is used to output the preset voltage according to the voltage output by the preset voltage module and the reference voltage, and the first filter circuit can be used to filter the preset voltage.
[0028] When the switching module switches from connecting the preset voltage module to the loop filter module to connecting the phase detector to the loop filter module, the first filter circuit can be used to maintain the voltage at the second input and output terminals of the first operational amplifier.
[0029] In some embodiments, the first filter circuit includes a first resistor, a first capacitor, and a second capacitor;
[0030] The two ends of the first capacitor are connected in parallel to the second input and output terminals of the first operational amplifier, and the two ends of the second capacitor connected in series with the first resistor are connected in parallel to the second input and output terminals of the first operational amplifier.
[0031] In some embodiments, the adder circuit includes a second operational amplifier; the first input terminal of the second operational amplifier is used to receive the preset voltage and the voltage output by the voltage sampling circuit, respectively, and the second input terminal is used to connect to the output terminal.
[0032] In some embodiments, the phase-locked loop circuit further includes a second filter circuit and / or a third filter circuit;
[0033] The second filtering circuit is used to filter the phase control signal and input it to the loop filtering module when the switching module connects the phase detector to the loop filtering module;
[0034] The third filtering circuit is used to filter the preset voltage or phase control voltage output by the loop filtering module and then input it to the voltage-controlled oscillator.
[0035] In some embodiments, the second filter circuit is an RC filter circuit; and / or, the third filter circuit is an RC filter circuit.
[0036] In some embodiments, the mixing module includes a local oscillator, a mixer, and a mixing filter;
[0037] The local oscillator is used to generate a local oscillation signal;
[0038] The mixer is used to mix the local oscillation signal and the output signal and then output the result.
[0039] The mixing filter is used to filter the signal output by the mixer and then output the mixed signal.
[0040] According to the second aspect, one embodiment provides a phase-locked loop circuit, including a phase detector, a loop filter module, a voltage-controlled oscillator, a preset voltage module, and a switching module;
[0041] The voltage-controlled oscillator is used to generate an output signal of a corresponding frequency according to the input voltage;
[0042] The phase detector is used to receive a reference signal and the output signal, and output a phase control signal based on the phase difference between the reference signal and the output signal;
[0043] The preset voltage module is used to control the loop filter module to output a preset voltage;
[0044] The switching module is used to connect the phase detector or the preset voltage module to the loop filter module; wherein...
[0045] When it is necessary to preset the voltage of the voltage-controlled oscillator, the switching module connects the preset voltage module to the loop filter module. The preset voltage module controls the loop filter module to output a preset voltage, and the voltage-controlled oscillator can generate the output signal of a preset frequency according to the preset voltage.
[0046] After the voltage-controlled oscillator is preset, the switching module connects the phase detector to the loop filter module. The loop filter module receives the phase control signal, filters the phase control signal, and outputs a phase control voltage. The voltage-controlled oscillator can generate the frequency of the output signal that is synchronized with the frequency of the reference signal according to the phase control voltage.
[0047] According to the phase-locked loop circuit of the above embodiment, the switching module can selectively connect either a phase detector or a preset voltage module to the loop filter module. When the voltage-controlled oscillator (VCO) needs to be preset, the preset voltage module is connected to the loop filter module, and the preset voltage module independently controls the loop filter module to output a preset voltage, causing the VCO to generate an output signal at a preset frequency to achieve near-synchronization with the reference signal frequency. After the voltage preset of the VCO is completed, the phase detector is connected to the loop filter module, and the phase detector independently controls the loop filter module to output a phase control voltage, enabling the VCO to quickly generate an output signal synchronized with the reference signal frequency based on the phase control voltage at the preset frequency, thereby completing phase locking. Since the switching module can selectively connect either a phase detector or a preset voltage module to the loop filter module, switching the switching module can avoid the introduction of phase noise by the preset voltage module. Furthermore, since both the phase detector and the preset voltage module independently control the output of the loop filter module, voltage fluctuations in the loop filter module can be reduced during switching, thereby improving the stability of the phase-locked loop. Attached Figure Description
[0048] Figure 1 This is a schematic diagram of a phase-locked loop circuit structure according to one embodiment;
[0049] Figure 2 This is a schematic diagram of a phase-locked loop circuit structure according to another embodiment;
[0050] Figure 3 This is a schematic diagram of a phase-locked loop circuit structure according to another embodiment;
[0051] Figure 4 This is a schematic diagram of a phase-locked loop circuit structure according to one embodiment. Detailed Implementation
[0052] The present application will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by related similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; the relevant operations can be fully understood based on the description in the specification and general technical knowledge in the art.
[0053] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.
[0054] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).
[0055] In current technical solutions, the preset circuit mainly uses the preset voltage output by the DAC and the voltage output by the phase detector to be coupled and superimposed through resistive coupling or other methods. Therefore, the phase noise of the preset circuit will also be introduced during coupling, which will degrade the phase noise of the system.
[0056] In some embodiments of this application, by switching the switching module, the preset voltage module can be connected to the loop filter module only when a preset voltage output is required, and the phase detector can be connected to the loop filter module when the preset voltage output is not required. This switching of the switching module avoids the introduction of phase noise by the preset voltage module. Furthermore, both the phase detector and the preset voltage module independently control the output of the loop filter module, reducing voltage fluctuations in the loop filter module during switching, shortening the lock-up time of the phase-locked loop, and preventing loop instability and changes in loop parameters.
[0057] Some embodiments provide a phase-locked loop circuit. Please refer to [reference needed]. Figure 1 The phase-locked loop circuit includes a phase detector 10, a mixer module 20, a loop filter module 30, a voltage-controlled oscillator 40, a preset voltage module 50, and a switching module 60. These components are described in detail below.
[0058] The voltage-controlled oscillator 40 is used to generate an output signal of a corresponding frequency based on the input voltage. The frequency of the output signal generated by the voltage-controlled oscillator 40 is preset to be related to the input control voltage; therefore, the frequency of the output signal can be controlled by the corresponding control voltage.
[0059] The mixing module 20 is used to perform mixing processing on the output signal to obtain a mixed signal, which can be used to realize frequency shifting of the phase-locked loop, such as frequency multiplication of the phase-locked loop based on frequency shifting.
[0060] Please refer to Figure 2In some embodiments, the mixing module 20 includes a local oscillator 22, a mixer 24, and a mixing filter 26. The local oscillator 22 generates a local oscillation signal, the mixer 24 mixes the local oscillation signal and the output signal, and the mixing filter 26 filters the signal output by the mixer 24 to output a mixed signal. The mixing filter 26 can be selected to filter different frequency bands as needed; for example, a low-frequency filter can be selected to achieve frequency multiplication of the phase-locked loop.
[0061] Phase detector 10 is used to receive reference signal and mixing signal, and output phase control signal according to the phase difference between reference signal and mixing signal. The phase control signal is filtered by loop filter module 30 and outputs phase control voltage. Voltage controlled oscillator 40 receives phase control voltage and controls the frequency of output signal.
[0062] The preset voltage module 50 is used to control the output preset voltage of the loop filter module 30, and the voltage-controlled oscillator 40 receives the preset voltage and controls the frequency of the output signal.
[0063] The switch module 60 is used to connect the phase detector 10 or the preset voltage module 50 to the loop filter module 30.
[0064] In some embodiments, when the voltage-controlled oscillator 40 needs to be voltage preset, the switching module 60 connects the preset voltage module 50 to the loop filter module 30. The preset voltage module 50 controls the loop filter module 30 to output a preset voltage. The voltage-controlled oscillator 40 can generate an output signal of a preset frequency according to the preset voltage, thereby enabling the phase-locked loop to be preset to near the desired frequency based on the preset voltage. Here, "near" means within a certain range of the desired frequency, thus roughly locking the desired frequency. After the voltage preset of the voltage-controlled oscillator 40 is completed, the switching module 60 connects the phase detector 10 to the loop filter module 30. The loop filter module 30 receives the phase control signal, filters the phase control signal, and outputs a phase control voltage. The voltage-controlled oscillator 40 can generate an output signal frequency synchronized with the reference signal frequency according to the phase control voltage, that is, the output signal reaches the desired frequency, thereby achieving the locking of the desired frequency. Synchronization with the reference signal frequency means that the frequency of the output signal and the frequency of the reference signal have a preset relationship and change synchronously. For example, the frequency of the output signal can be the same as the frequency of the reference signal, or the frequency of the output signal can be different from the frequency of the reference signal after the frequency shifting is performed by the mixing module 20.
[0065] Since the phase detector 10 has already generated a corresponding phase control signal based on the preset frequency output signal when the voltage-controlled oscillator 40 generates the preset frequency output signal according to the preset voltage, it can further control the frequency of the output signal on the basis of the preset frequency, so that the phase-locked loop can quickly lock the reference signal.
[0066] In the above embodiments, the switching module 60 can selectively connect the phase detector 10 or the preset voltage module 50 to the loop filter module 30, thereby avoiding phase noise introduced by the preset voltage module 50. Furthermore, both the phase detector 10 and the preset voltage module 50 independently control the output of the loop filter module 30, which can reduce voltage fluctuations in the loop filter module 30 and improve the stability of the phase-locked loop.
[0067] In some embodiments, the loop filter module 30 includes an active filter circuit configured to be connected to a reference voltage Vref.
[0068] Specifically, when the switching module 60 connects the preset voltage module 50 to the loop filter module 30, the preset voltage module 50 acquires the voltage output by the active filter circuit and performs feedback control on the active filter circuit based on the output voltage, causing the active filter circuit to output a preset voltage at the reference voltage Vref. When the switching module 60 connects the phase detector 10 to the loop filter module 30, the active filter circuit filters the phase control signal and outputs a phase control voltage.
[0069] Please refer to Figure 3 In some embodiments, the active filtering circuit includes a first operational amplifier U1 and a first filtering circuit. The first input terminal of the first operational amplifier U1 receives a reference voltage Vref, and the second input terminal of the first operational amplifier U1 receives the voltage output by the preset voltage module 50 when the switching module 60 connects the preset voltage module 50 to the loop filtering module 30, and receives a phase control signal when the switching module 60 connects the phase detector 10 to the loop filtering module 30. The first filtering circuit is connected in parallel between the second input terminal and the output terminal of the first operational amplifier U1.
[0070] Specifically, when the switching module 60 connects the preset voltage module 50 to the loop filter module 30, the first operational amplifier U1 outputs a preset voltage based on the voltage output by the preset voltage module 50 and the reference voltage Vref, and the first filter circuit can be used to filter the preset voltage. When the switching module 60 switches from connecting the preset voltage module 50 to the loop filter module 30, and then switches from connecting the phase detector 10 to the loop filter module 30, the first filter circuit can be used to maintain the voltage at the second input and output terminals of the first operational amplifier U1.
[0071] In the above embodiments, the preset voltage module 50 performs feedback control on the active filter circuit based on the voltage output by the active filter circuit, thereby controlling the output preset voltage of the active filter circuit. The first filter circuit can maintain the voltage at the second input and output terminals of the first operational amplifier U1, so that when the switching module 60 connects the phase detector 10 to the loop filter module 30, it can avoid voltage fluctuations at the second input and output terminals of the first operational amplifier U1 and maintain them near the voltage required by the voltage-controlled oscillator 40. Therefore, when the phase detector 10 controls the output phase control voltage of the loop filter module 30, the phase detector 10 loop does not need to be rebalanced. Thus, the phase-locked loop can lock quickly without causing changes in the noise loop parameters.
[0072] In some embodiments, the first filter circuit includes a first resistor R2, a first capacitor C3, and a second capacitor C2. The two ends of the first capacitor C3 are connected in parallel to the second input and output terminals of the first operational amplifier U1. The two ends of the second capacitor C2, connected in series with the first resistor R2, are also connected in parallel to the second input and output terminals of the first operational amplifier U1. The first capacitor C3 and the second capacitor can maintain the voltage at the second input and output terminals of the first operational amplifier U1 based on the charging and discharging process. Additionally, the first capacitor C3 and the second capacitor C2 can also isolate DC signals, allowing the first operational amplifier U1 to be driven by the preset voltage module 50.
[0073] Please refer to Figure 2 In some embodiments, the preset voltage module 50 includes a voltage output source 52, an adder circuit 54, and a voltage sampling circuit 56. The voltage output source 52 is used to output a preset voltage, the voltage sampling circuit 56 is used to acquire the voltage output by the active filter circuit, and the adder circuit 54 receives the preset voltage and the voltage output by the active filter circuit respectively, performs summation processing, and outputs the summed voltage to the active filter circuit, so that the active filter circuit outputs the preset voltage according to the summed voltage and the reference voltage Vref.
[0074] The voltage output source 52 can output a preset voltage according to preset requirements. The adder circuit 54 adds the preset voltage to the voltage at the output of the first operational amplifier U1 to obtain a summed voltage. When the summed voltage output by the adder circuit 54 is greater than the reference voltage Vref, the voltage at the output of the first operational amplifier U1 decreases and is used by the voltage sampling circuit 56 to output to the adder circuit 54, causing the summed voltage output by the adder circuit 54 to decrease, ultimately making the summed voltage equal to the reference voltage Vref. Conversely, when the summed voltage output by the adder circuit 54 is less than the reference voltage Vref, the voltage at the output of the first operational amplifier U1 increases and is used by the voltage sampling circuit 56 to output to the adder circuit 54, causing the summed voltage output by the adder circuit 54 to increase, ultimately making the summed voltage equal to the reference voltage Vref. When the summed voltage equals the reference voltage Vref, the preset voltage output by the first operational amplifier U1 and the preset voltage have a preset relationship, thus enabling the loop filter module 30 to output a preset voltage based on the preset voltage module 50.
[0075] Please refer to Figure 3 In some embodiments, the voltage output source 52 may be implemented based on a digital-to-analog converter (DAC). In some embodiments, the voltage sampling circuit 56 may be implemented based on a sampling resistor R4.
[0076] In some embodiments, the adder circuit 54 includes a second operational amplifier U2. The first input terminal of the second operational amplifier U2 is used to receive a preset voltage and the voltage output from the active filter circuit, respectively, and the second input terminal is connected to the output terminal. The second operational amplifier U2 also has peripheral circuitry to form the adder circuit 54. This peripheral circuitry includes resistors R5, R6, and R7. One end of resistor R5 is connected to the voltage output source 52 to receive the preset voltage output by the voltage output source 52, and the other end of resistor R5 is connected to the first input terminal of the second operational amplifier U2. One end of resistor R6 is connected to the voltage sampling circuit 56 to receive the voltage output from the active filter circuit sampled by the voltage sampling circuit 56, and the other end of resistor R6 is connected to the first input terminal of the second operational amplifier U2. The two ends of resistor R7 are connected to the output terminal and the second input terminal of the second operational amplifier U2, respectively.
[0077] Please refer to Figure 2 In some embodiments, the switching module 60 includes a first switch 62 and a second switch 64. The first switch 62 is used to connect the phase detector 10 and the loop filter module 30, and the second switch 64 is used to connect the preset voltage module 50 and the loop filter module 30. The first switch 62 and the second switch 64 connect the phase detector 10 to the loop filter module 30 or the preset voltage module 50 to the loop filter module 30 by turning them on and off.
[0078] Please refer to Figure 3 The process by which the preset voltage module 50 controls the loop filter module 30 to output the preset voltage is as follows: When voltage preset is required, the first switch 62 is open, and the second switch 64 is open. At this time, the first capacitor C3 and the second capacitor C2 have DC blocking function, and the first switch 62 is open. The resistance value of resistor R8 is set to be relatively large, and the inverting input terminal of the first operational amplifier U1 is driven by the preset voltage module 50. When the inverting input terminal of the first operational amplifier U1 is larger than the reference voltage Vref at the non-inverting input terminal, the output voltage of the first operational amplifier U1 will decrease. Since the second operational amplifier U2, resistors R5, R6, and R7 form a summing circuit, the output voltage of the second operational amplifier U2 will decrease due to the decrease in the output voltage of the first operational amplifier U1, ultimately making the output voltage of the second operational amplifier U2 equal to the reference voltage Vref. Conversely, when the inverting input terminal of the first operational amplifier U1 is smaller than the reference voltage Vref at the non-inverting input terminal, the output voltage of the second operational amplifier U2 will also be adjusted to match the reference voltage Vref.
[0079] The voltage at the output of the first operational amplifier U1 is controlled by the DAC, resistor R5, and resistor R6. The second operational amplifier U2 and resistor R7 form a voltage follower circuit. The output voltage of the second operational amplifier U2 is equal to the input voltage at its non-inverting input, and ultimately equal to the reference voltage Vref. Therefore, the relationship between the output voltage VDAC of the DAC and the output voltage Vo of the first operational amplifier U1 is as follows:
[0080] Vo=(VREF*(R5+R6)-VDAC*R6) / R5;
[0081] When the reference voltage Vref=0, i.e. grounded, it can be simplified to Vo=-VDAC*(R6 / R5). Therefore, the voltage at the output of the first operational amplifier U1 is controlled by the voltage output of the DAC.
[0082] Once the preset voltage is applied, the first switch 62 turns on, while the second switch 64 turns off. Since the voltages across the first capacitor C3 and the second capacitor C2 are near the reference voltage Vref and the voltage required by the voltage-controlled oscillator 40, the loop locks quickly without causing changes in the noise loop parameters. Furthermore, because the second switch 64 is off, and resistors R5 and R6 can be set to very large values, the preset voltage module 50 essentially does not introduce additional phase noise, ensuring the system's phase noise performance. For example, resistors R5 and R6 can be set to values above 10kΩ, while the output resistance of the first operational amplifier U1 is typically low, usually around 10Ω. Therefore, according to the voltage divider relationship, noise can be suppressed by 20*Log(10k / 10) = 60dB, thus essentially preventing the introduction of additional phase noise.
[0083] The above is a description of the preset voltage output of the preset voltage module 50 and the control loop filter module 30.
[0084] Please refer to Figure 3 In some embodiments, the phase-locked loop circuit further includes a second filter circuit and / or a third filter circuit. The second filter circuit filters the phase control signal before inputting it to the loop filter module 30 when the switching module 60 connects the phase detector 10 to the loop filter module 30. The third filter circuit filters the preset voltage or phase control voltage output by the loop filter module 30 before inputting it to the voltage-controlled oscillator 40. In some embodiments, the second filter circuit is an RC filter circuit, including resistors R8 and R1 and capacitor C1. In some embodiments, the third filter circuit is an RC filter circuit, including resistor R3, capacitor C5, and capacitor C4.
[0085] The above is a description of the loop filter module of active filtering.
[0086] In some embodiments, the loop filter module 30 includes a passive filter circuit. When the switch module 60 connects the preset voltage module 50 to the loop filter module 30, the preset voltage module 50 outputs a preset voltage to the loop filter module 30, so that the passive filter circuit filters the preset voltage and outputs the preset voltage. When the switch module 60 connects the phase detector 10 to the loop filter module 30, the passive filter circuit filters the phase control signal and outputs a phase control voltage. In this case, the preset voltage module 50 may only include a voltage output source 52 for outputting the preset voltage.
[0087] In some embodiments, the passive filter circuit can be an RC filter circuit or a filter circuit of other structures, which will not be described in detail here.
[0088] The above is an explanation of the phase-locked loop circuit for frequency mixing.
[0089] Among them, phase-locked loop circuits can also be non-mixed. The following is a detailed explanation of the differences between non-mixed and mixed phase-locked loop circuits.
[0090] Please refer to Figure 4 Some embodiments provide a phase-locked loop circuit, which includes a phase detector 10, a loop filter module 30, a voltage-controlled oscillator 40, a preset voltage module 50, and a switching module 60.
[0091] The voltage-controlled oscillator 40 is used to generate an output signal of a corresponding frequency according to the input voltage.
[0092] The phase detector 10 is used to receive the reference signal and the output signal, and output a phase control signal based on the phase difference between the reference signal and the output signal.
[0093] The preset voltage module 50 is used to control the output preset voltage of the loop filter module 30.
[0094] The switching module 60 is used to connect the phase detector 10 or the preset voltage module 50 to the loop filter module 30.
[0095] When it is necessary to preset the voltage of the voltage-controlled oscillator 40, the switching module 60 connects the preset voltage module 50 to the loop filter module 30. The preset voltage module 50 controls the loop filter module 30 to output the preset voltage, and the voltage-controlled oscillator 40 can generate an output signal of a preset frequency according to the preset voltage.
[0096] After the voltage-controlled oscillator 40 is preset, the switching module 60 connects the phase detector 10 to the loop filter module 30. The loop filter module 30 receives the phase control signal, filters the phase control signal, and outputs the phase control voltage. The voltage-controlled oscillator 40 can generate an output signal that is synchronized with the frequency of the reference signal according to the phase control voltage.
[0097] In some embodiments, the phase detector 10, loop filter module 30, voltage-controlled oscillator 40, preset voltage module 50 and switch module 60 can all adopt the solutions in the above embodiments, and will not be described again here.
[0098] Those skilled in the art will understand that all or part of the functions of the various methods in the above embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, which may include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to achieve the above functions. For example, the program can be stored in the memory of a device, and when the program in the memory is executed by the processor, all or part of the above functions can be achieved. In addition, when all or part of the functions in the above embodiments are implemented by computer programs, the program can also be stored in a server, another computer, disk, optical disk, flash drive, or external hard drive, etc., and can be downloaded or copied to the memory of a local device, or the system of the local device can be updated. When the program in the memory is executed by the processor, all or part of the functions in the above embodiments can be achieved.
[0099] The above examples illustrate this application only to aid understanding and are not intended to limit its scope. Those skilled in the art to which this application pertains can make various simple deductions, modifications, or substitutions based on the ideas presented.
Claims
1. A phase-locked loop circuit, characterized in that, It includes a phase detector, a mixer module, a loop filter module, a voltage-controlled oscillator, a preset voltage module, and a switching module; The voltage-controlled oscillator is used to generate an output signal of a corresponding frequency according to the input voltage; The mixing module is used to perform mixing processing on the output signal to obtain a mixed signal; The phase detector is used to receive the reference signal and the mixed signal, and output a phase control signal according to the phase difference between the reference signal and the mixed signal; The preset voltage module is used to control the loop filter module to output a preset voltage; The switching module is used to connect the phase detector or the preset voltage module to the loop filter module; wherein... When it is necessary to preset the voltage of the voltage-controlled oscillator, the switching module connects the preset voltage module to the loop filter module. The preset voltage module controls the loop filter module to output a preset voltage, and the voltage-controlled oscillator can generate the output signal of a preset frequency according to the preset voltage. After the voltage-controlled oscillator is preset, the switching module connects the phase detector to the loop filter module. The loop filter module receives the phase control signal, filters the phase control signal, and outputs a phase control voltage. The voltage-controlled oscillator can generate an output signal that is synchronized with the frequency of the reference signal according to the phase control voltage.
2. The phase-locked loop circuit as described in claim 1, characterized in that, The loop filter module includes an active filter circuit, which is configured to be connected to a reference voltage; When the switching module connects the preset voltage module to the loop filter module, the preset voltage module is used to obtain the voltage output by the active filter circuit, and to perform feedback control on the active filter circuit according to the voltage output by the active filter circuit, so that the active filter circuit outputs the preset voltage under the reference voltage. When the switching module connects the phase detector to the loop filter module, the active filter circuit filters the phase control signal and outputs the phase control voltage. or, The loop filter module includes a passive filter circuit. When the switch module connects the preset voltage module to the loop filter module, the preset voltage module is used to output a preset voltage to the loop filter module, so that the passive filter circuit filters the preset voltage and outputs the preset voltage. When the switching module connects the phase detector to the loop filter module, the passive filter circuit filters the phase control signal and outputs the phase control voltage.
3. The phase-locked loop circuit as described in claim 2, characterized in that, When the loop filter module includes an active filter circuit, the preset voltage module includes a voltage output source, an adder circuit, and a voltage sampling circuit; The voltage output source is used to output a preset voltage; The voltage sampling circuit is used to obtain the voltage output by the active filter circuit; The adder circuit receives the preset voltage and the voltage output by the active filter circuit respectively, performs summation processing, and outputs the summed voltage to the active filter circuit. The active filter circuit outputs the preset voltage based on the summed voltage and the reference voltage; wherein the preset voltage and the preset voltage have a preset relationship.
4. The phase-locked loop circuit as described in claim 2 or 3, characterized in that, The active filter circuit includes a first operational amplifier and a first filter circuit; The first input terminal of the first operational amplifier receives the reference voltage, the second input terminal receives the voltage output by the preset voltage module, and the first filter circuit is connected in parallel between the second input terminal and the output terminal of the first operational amplifier. When the switching module connects the preset voltage module to the loop filter module, the first operational amplifier is used to output the preset voltage according to the voltage output by the preset voltage module and the reference voltage, and the first filter circuit can be used to filter the preset voltage. When the switching module switches from connecting the preset voltage module to the loop filter module to connecting the phase detector to the loop filter module, the first filter circuit can be used to maintain the voltage at the second input and output terminals of the first operational amplifier.
5. The phase-locked loop circuit as described in claim 4, characterized in that, The first filter circuit includes a first resistor, a first capacitor, and a second capacitor; The two ends of the first capacitor are connected in parallel to the second input and output terminals of the first operational amplifier, and the two ends of the second capacitor connected in series with the first resistor are connected in parallel to the second input and output terminals of the first operational amplifier.
6. The phase-locked loop circuit as described in claim 3, characterized in that, The adder circuit includes a second operational amplifier; the first input terminal of the second operational amplifier is used to receive the preset voltage and the voltage output by the voltage sampling circuit, respectively, and the second input terminal is used to connect to the output terminal.
7. The phase-locked loop circuit as described in claim 1, characterized in that, It also includes a second filter circuit and / or a third filter circuit; The second filtering circuit is used to filter the phase control signal and input it to the loop filtering module when the switching module connects the phase detector to the loop filtering module; The third filtering circuit is used to filter the preset voltage or phase control voltage output by the loop filtering module and then input it to the voltage-controlled oscillator.
8. The phase-locked loop circuit as described in claim 7, characterized in that, The second filter circuit is an RC filter circuit; and / or, the third filter circuit is an RC filter circuit.
9. The phase-locked loop circuit as described in claim 1, characterized in that, The mixing module includes a local oscillator, a mixer, and a mixing filter; The local oscillator is used to generate a local oscillation signal; The mixer is used to mix the local oscillation signal and the output signal and then output the result. The mixing filter is used to filter the signal output by the mixer and then output the mixed signal.
10. A phase-locked loop circuit, characterized in that, It includes a phase detector, a loop filter module, a voltage-controlled oscillator, a preset voltage module, and a switching module; The voltage-controlled oscillator is used to generate an output signal of a corresponding frequency according to the input voltage; The phase detector is used to receive a reference signal and the output signal, and output a phase control signal based on the phase difference between the reference signal and the output signal; The preset voltage module is used to control the loop filter module to output a preset voltage; The switching module is used to connect the phase detector or the preset voltage module to the loop filter module; wherein... When it is necessary to preset the voltage of the voltage-controlled oscillator, the switching module connects the preset voltage module to the loop filter module. The preset voltage module controls the loop filter module to output a preset voltage, and the voltage-controlled oscillator can generate the output signal of a preset frequency according to the preset voltage. After the voltage-controlled oscillator is preset, the switching module connects the phase detector to the loop filter module. The loop filter module receives the phase control signal, filters the phase control signal, and outputs a phase control voltage. The voltage-controlled oscillator can generate an output signal that is synchronized with the frequency of the reference signal according to the phase control voltage.