Clock phase demodulation method and molecular clock

Abstract

The embodiment of the invention provides a clock phase demodulation method and a molecular clock, and the method comprises the steps: determining a demodulation phase initial value of an Nth harmonic based on an Nth harmonic signal outputted by the clock; wherein the N is a positive integer and is an odd number; determining a first phase change value of the Mth harmonic signal along with time based on the Mth harmonic signal output by the clock; determining a second phase change value, changing along with time, of the L-th harmonic signal based on the L-th harmonic signal output by the clock; wherein M and L are positive integers and are even numbers; calculating a target demodulation phase based on the demodulation phase initial value, the first phase change value and the second phase change value; wherein the target demodulation phase is a demodulation phase used under the condition that frequency locking is carried out by adopting Nth harmonic waves. Through the method, the calculation amount of phase demodulation of the clock can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of clock control, and in particular to a clock phase demodulation method and a molecular clock. Background Art

[0002] In order to avoid the influence of low-frequency detection noise and low-frequency phase noise, molecular clocks usually use higher modulation frequencies (greater than 100kHz). The frequency locking effect is more susceptible to the change of demodulation phase, which causes the frequency stability performance of molecular clocks to change over time.

[0003] However, the demodulation effect achieved by the current phase demodulation method for the clock is relatively poor. Summary of the invention

[0004] The purpose of the present application is to provide a clock phase demodulation method and a molecular clock, which can reduce the calculation amount of clock phase demodulation and improve the effect of phase demodulation.

[0005] In the first aspect, an embodiment of the present application provides a clock phase demodulation method, which is applied to a clock, and the clock phase demodulation includes: based on the Nth harmonic signal output by the clock, determining the initial demodulation phase value of the Nth harmonic; wherein N is a positive integer and an odd number; based on the Mth harmonic signal output by the clock, determining the first phase change value of the Mth harmonic signal that changes with time; based on the Lth harmonic signal output by the clock, determining the second phase change value of the Lth harmonic signal that changes with time; wherein M and L are positive integers and are even numbers; based on the initial demodulation phase value, the first phase change value and the second phase change value, calculating the target demodulation phase; wherein the target demodulation phase is the demodulation phase used when frequency locking is performed using the Nth harmonic.

[0006] In the above implementation, by combining the phase changes of at least two even-numbered harmonic signals to calculate the demodulation phase of the odd-numbered harmonic signal, the demodulation phase synchronization function in the normal clock frequency locking process can be realized, reducing the sensitivity of the clock frequency stability to environmental factors and the aging of the clock frequency stability. On this basis, there is no need to occupy the frequency locking time, avoiding the deterioration of the clock frequency locking performance. Furthermore, using the phase change as the calculation basis of the demodulation phase can reduce the problem of mislocking caused by the multi-valued nature of the phase calculation.

[0007] In an optional embodiment, the target demodulation phase is calculated based on the demodulation phase initial value, the first phase change value and the second phase change value, including: determining the target phase change value of the Nth harmonic according to the first phase change value and the second phase change value; determining the target demodulation phase according to the target phase change value and the demodulation phase initial value.

[0008] In the above implementation, based on the phase change value corresponding to the even-order harmonic signal, the change of the Nth harmonic is determined, and then combined with the phase change to determine the real-time target demodulation phase; thereby better adapting to the changing phase demodulation requirements of the clock locked at different times and stages.

[0009] In an optional implementation, the target phase change value is determined by the following formula:

[0010]

[0011] in, Indicates the target phase change value; represents a second phase change value; Indicates the first phase change value.

[0012] In an optional embodiment, the method of determining a first phase change value of the Mth harmonic signal that changes with time based on the Mth harmonic signal output by the clock includes: determining a first initial phase value of the Mth harmonic signal based on the Mth harmonic signal output by the clock; performing phase estimation on the Mth harmonic signal output in real time based on a set algorithm to obtain a first phase estimation value of the Mth harmonic signal; and determining a first phase change value of the Mth harmonic signal based on the first initial phase value and the first phase estimation value.

[0013] In an optional embodiment, the method of determining a first initial phase value of the Mth harmonic signal based on the Mth harmonic signal output by the clock includes: calculating the amplitude and phase of the signal curve at each scanning frequency point according to the Mth harmonic signal and the detection signal output by the clock; wherein the scanning frequency point is determined by configuring the scanning frequency condition in the process of the clock outputting the microwave signal; from the amplitudes of the signal curve calculated at each scanning frequency point, selecting a first target amplitude whose amplitude of the signal curve meets the set conditions, and taking the phase at the scanning frequency point where the first target amplitude is located as the first initial phase value.

[0014] In an optional embodiment, the first target amplitude whose amplitude satisfies a set condition is selected from the amplitudes of the signal curve calculated at each scanning frequency point, comprising: determining a set of first target scanning frequency points greater than the molecular resonance frequency from the plurality of scanning frequency points; wherein the molecular resonance frequency is determined by a spectrum curve formed by a detection signal output by the clock; and determining, based on the amplitudes of the signal curves of each first target scanning frequency point in the set of the first target scanning frequency points, a signal curve with the largest amplitude as the first target amplitude.

[0015] In an optional implementation, the amplitude and phase of the signal curve are calculated using the following formula:

[0016]

[0017] Among them, v sweep，i represents the i-th scanning frequency point; v0 represents the center frequency value; I M (v0+v swepp，i ) indicates that at the scanning frequency point v sweep，i I signal under; Q M (v0+v sweep，i ) means that at the Mth harmonic, at the scanning frequency point v sweep，i Q signal under; A M (v0+v sweep，i ) means that at the Mth harmonic, at the scanning frequency point v sweep，i The amplitude of the signal curve below; φ M (v0+v sweep，i ) means that at the Mth harmonic, at the scanning frequency point v sweep，i The next phase.

[0018] In an optional embodiment, the phase of the Mth harmonic signal output in real time is estimated based on a set algorithm to obtain a first phase estimation value of the Mth harmonic signal, including: using the set algorithm to calculate the Mth harmonic signal output in real time to obtain a phase estimation value of the Mth harmonic signal; and unwrapping the phase estimation value to obtain a first phase estimation value.

[0019] In an optional embodiment, the method of using a set algorithm to calculate the Mth harmonic signal output in real time to obtain a phase estimate of the Mth harmonic signal includes: using Fourier transform to calculate the Mth harmonic signal output in real time to obtain a phase estimate of the Mth harmonic signal.

[0020] In an optional embodiment, the method of determining a second phase change value of the L-order harmonic signal that changes with time based on the L-order harmonic signal output by the clock includes: determining a second initial phase value of the L-order harmonic signal based on the L-order harmonic signal output by the clock; performing phase estimation on the L-order harmonic signal output in real time based on a set algorithm to obtain a second phase estimation value of the L-order harmonic signal; and determining a second phase change value of the L-order harmonic signal based on the second initial phase value and the second phase estimation value.

[0021] In an optional embodiment, the second initial phase value of the Lth harmonic signal is determined based on the Lth harmonic signal output by the clock, including: at each scanning frequency point, according to the Lth harmonic signal and the detection signal output by the clock, calculating the amplitude and phase of the signal curve; wherein the scanning frequency point is determined by configuring the scanning frequency condition in the process of the clock outputting the microwave signal; from the amplitudes of the signal curve calculated at each scanning frequency point, selecting a second target amplitude whose amplitude of the signal curve meets the set conditions, and taking the phase at the scanning frequency point where the second target amplitude is located as the second initial phase value.

[0022] In an optional embodiment, the second target amplitude of the signal curve whose amplitude satisfies a set condition is selected from the amplitudes of the signal curve calculated at each scanning frequency point, comprising: determining a set of second target scanning frequency points greater than the molecular resonance frequency from the plurality of scanning frequency points; wherein the molecular resonance frequency is determined by a spectrum curve formed by a detection signal output by the clock; and determining, based on the amplitudes of the signal curves of each second target scanning frequency point in the set of the second target scanning frequency points, a signal curve with the largest amplitude as the second target amplitude.

[0023] In an optional implementation, the amplitude and phase of the signal curve are calculated using the following formula:

[0024]

[0025] φ L (v0+v sweep，i )=arg(I L (v0+v sweep，i )+iQ L (v0+v sweep，i )).

[0026] Among them, v sweep，i represents the i-th scanning frequency point; v0 represents the center frequency value; I L (v0+v sweep，i ) indicates that at the scanning frequency point v sweep，i I signal under; Q L (v0+v sweep，i ) means that at the Lth harmonic, at the scanning frequency point v sweep，i Q signal under; A L (v0+v sweep，i ) means that at the Lth harmonic, at the scanning frequency point v sweep，i The amplitude of the signal curve below; φ L (v0+v sweep，i ) means that at the Lth harmonic, at the scanning frequency point vsweep，i The next phase.

[0027] In an optional embodiment, the phase of the Lth harmonic signal output in real time is estimated based on a set algorithm to obtain a second phase estimation value of the Lth harmonic signal, including: using the set algorithm to calculate the Lth harmonic signal output in real time to obtain a phase estimation value of the Lth harmonic signal; and unwrapping the phase estimation value to obtain a second phase estimation value.

[0028] In the above implementation, the calculated phase estimate can also be unwrapped to solve the ambiguity problem in the phase signal. The jump caused by the phase change exceeding 2π can be improved, and the real phase information can be restored by unwrapping operation, so that the phase estimate obtained by subsequent calculation can be more accurate.

[0029] In an optional embodiment, the method of using a set algorithm to calculate the Lth harmonic signal output in real time to obtain a phase estimate of the Lth harmonic signal includes: using Fourier transform to calculate the Lth harmonic signal output in real time to obtain a phase estimate of the Lth harmonic signal.

[0030] In a second aspect, an embodiment of the present application provides a molecular clock, comprising: a microwave output unit, a digital-to-analog converter, a control module and an analog-to-digital converter; the microwave output unit is used to output an analog detection signal and a clock signal; the analog-to-digital converter is used to convert the analog detection signal output by the microwave output unit into a digital detection signal; the control module is used to use the above-mentioned method to determine a frequency control signal to control the microwave output unit; the digital-to-analog converter is used to convert the frequency control signal calculated by the control module into an analog control signal, and transmit the analog control signal to the microwave output unit to adjust the clock signal output by the microwave output unit.

[0031] In an optional embodiment, the microwave output unit includes: a transmitting module, which is used to receive the control of the control module and scan the center frequency of the microwave signal; a crystal oscillator system connected to the transmitting module, which is used to output a crystal oscillator signal to the transmitting module, and the transmitting module is also used to output a frequency signal based on the crystal oscillator signal; a receiving module, which is used to detect the scanned microwave signal to obtain an analog detection signal; and a molecular gas chamber connected between the transmitting module and the receiving module, which is used to resonate and absorb microwaves of a specific frequency of the frequency signal of the transmitting module, and transmit the processed microwave signal to the receiving module. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 A schematic diagram of the structure of a molecular clock provided in an embodiment of the present application;

[0034] Figure 2 Another schematic diagram of the structure of the molecular clock provided in the embodiment of the present application;

[0035] Figure 3 A flowchart of a clock phase demodulation method provided in an embodiment of the present application.

[0036] Icon: 110 - microwave output unit; 120 - control module; 130 - analog-to-digital converter; 140 - digital-to-analog converter; 111 - crystal oscillator system; 112 - transmitting module; 113 - molecular gas chamber; 114 - receiving module. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application.

[0038] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present application, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be interpreted as a limitation of the present application.

[0040] In the description of this application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it 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, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0041] High-precision clocks mainly include atomic clocks and molecular clocks. Atomic clocks use the interaction between electromagnetic radiation and the excited state of specific atoms to achieve time measurement, and use the absorption peak generated by laser penetrating a glass gas chamber as a frequency reference. Molecular clocks use the electromagnetic wave molecular rotation spectrum generated by the quantized rotational energy level transition of polar gas molecules under the action of an electromagnetic field to achieve time measurement. Molecular clocks use high-frequency electromagnetic waves that penetrate the rotation spectrum peak of polar gases in the gas chamber as a frequency reference. Compared with atomic clocks, molecular clocks have a relatively simpler structure, but can also achieve relatively accurate timing.

[0042] In order to avoid the influence of low-frequency detection noise and low-frequency phase noise, molecular clocks usually use higher modulation frequencies (for example, usually greater than 100kHz), and the frequency locking effect is more susceptible to changes in the demodulation phase, resulting in the frequency stability performance of the molecular clock changing over time. Based on this type of problem, the current processing methods are: 1. Traditional atomic clocks usually use analog signals or digital signals to achieve phase synchronization of modulation and demodulation. The synchronization signal is the same frequency as the modulation frequency or an integer division of the modulation frequency. Due to electromagnetic coupling, the synchronization signal component is inevitably present in the detection signal, resulting in an additional error signal, which in turn leads to frequency deviation. 2. Molecular clocks use homologous high-frequency clocks to achieve phase synchronization between the phase-locked amplifier module and the frequency modulation module. However, the phase synchronization of this method is open-loop, and the phase synchronization effect is easily affected by changes in the characteristics of the detection signal filter and the loop bandwidth of the phase-locked loop. These changes may come from aging of device characteristics or changes in environmental factors. Or the optimal demodulation phase can be obtained through a spectrum scanning process. However, this process is time-consuming and cannot be performed simultaneously with clock frequency locking. If a spectrum scan is performed once after power-on, the phase synchronization effect will still be affected by environmental factors during subsequent operation. 3. If the spectrum is re-scanned multiple times to update the phase information during the operation of the molecular clock, the clock frequency stability performance will be reduced due to the long time occupied. 4. When the molecular clock frequency is normally locked, if the phase calculation is performed directly on the odd-order harmonics used for locking. Since the power of the odd-order error signal is very small in the frequency locking state, it cannot provide effective information about the phase for demodulation phase locking.

[0043] Based on the above research, the embodiments of the present application provide a clock phase demodulation method and a molecular clock. By combining the phase change of the even harmonics, the phase change of the odd harmonics is determined, thereby determining the demodulation phase of the odd harmonics. The clock frequency can be better maintained stable while using less calculation and time consumption. The clock phase demodulation method and molecular clock provided by the present application are introduced in combination with several embodiments.

[0044] Figure 1 This is a schematic diagram of the structure of the molecular clock provided in the embodiment of the present application. Figure 1 As shown, the molecular clock may include: a microwave output unit 110 , a control module 120 , an analog-to-digital converter 130 , and a digital-to-analog converter 140 .

[0045] The control module 120 is connected to the microwave output unit 110 ; the analog-to-digital converter 130 is connected to both the control module 120 and the microwave output unit 110 ; and the digital-to-analog converter 140 is also connected to both the control module 120 and the microwave output unit 110 .

[0046] In this embodiment, the microwave output unit 110 is used to output microwave signals and clock signals.

[0047] The microwave signal is used as a basis for determining a control signal for outputting a control clock signal.

[0048] Optionally, the control signal for controlling the molecular clock device to output the clock signal can be obtained by processing the microwave signal based on the control module 120, the analog-to-digital converter 130 and the digital-to-analog converter 140. Optionally, the microwave output unit can directly output the clock signal, or can output it based on the control signal of the clock signal.

[0049] The control module 120 may be used to control the microwave output unit 110 to scan the center frequency of the microwave signal to output an analog detection signal.

[0050] The control module 120 may be a processing chip having computing capabilities.

[0051] Since the signal output by the microwave output unit 110 and the control signal required to control the clock signal output by the microwave output unit 110 are both analog signals, and the signals calculated and processed by the control module 120 need to be digital signals. Based on this, the molecular clock device is provided with an analog to digital converter 130 (analog to digital converter, referred to as ADC), which can convert the analog detection signal obtained from the microwave output unit 110 into a digital detection signal, so as to facilitate the control module 120 to calculate and process the detection signal.

[0052] Exemplarily, the analog-to-digital converter 130 may convert the analog detection signal into a digital detection signal sequence with a sampling period as the time interval, and the digital detection signal sequence includes multiple digital detection signals. For example, the i-th digital detection signal in the digital detection signal sequence may be represented as P i .

[0053] The control module 120 provided in the embodiment of the present application can also be used to obtain a frequency control signal based on the digital detection signal. Considering that the frequency control signal calculated by the control module 120 is a digital signal, in order to facilitate the use of the microwave output unit 110, the molecular clock device is provided with a digital to analog converter 140 (digital to analog converter, referred to as DAC). The digital to analog converter 140 can be used to convert the frequency control signal calculated by the control module 120 into an analog control signal, and transmit the analog control signal to the microwave output unit 110, and the analog control signal is used to adjust the clock signal output by the microwave output unit 110.

[0054] Optionally, the digital-to-analog converter 140 may have low integral nonlinearity and differential nonlinearity.

[0055] In this embodiment, the analog control signal controls the frequency of the crystal oscillator of the microwave output unit 110 to achieve closed-loop locking of the molecular clock frequency.

[0056] In this embodiment, the control module 120 may send a scanning control signal to the microwave output unit 110 , and the scanning control signal is used to control the microwave output unit 110 to start center frequency scanning to scan the center frequency of the microwave signal.

[0057] When the center frequency scan is started, the microwave output unit 110 can scan with a specified frequency as the frequency step, a specified time as the single step time, a preset number of points as the scanning points and a preset starting frequency to obtain a center frequency signal, and use the center frequency signal as the analog detection signal.

[0058] Optionally, the microwave output unit 110 can perform single or multiple scans according to a sawtooth wave based on a specified frequency as frequency step, a specified time as single step time, a preset number of points as scanning points and a preset starting frequency to obtain a center frequency signal.

[0059] Optionally, the control module 120 may be implemented by a single chip microcomputer.

[0060] Optionally, the control module 120 is further configured to control the microwave output unit 110 to perform frequency modulation to output multiple harmonic signals.

[0061] Exemplarily, the control module 120 may set the modulation frequency and the maximum frequency deviation of the microwave signal of the microwave output unit 110 to achieve frequency modulation of the microwave signal of the microwave output unit 110 .

[0062] Through the frequency modulation of the control module 120, the microwave output unit 110 can output an Nth harmonic signal.

[0063] Optionally, the control module 120 may input a modulation control signal to the microwave output unit 110 to implement frequency modulation on the microwave signal of the microwave output unit 110. Exemplarily, the frequency modulation method used by the microwave output unit 110 may be sinusoidal frequency modulation.

[0064] When the frequency modulation is started, the microwave output unit 110 can perform sinusoidal frequency modulation at a preset modulation frequency and a preset maximum frequency deviation to obtain a modulation frequency signal.

[0065] Optionally, the signal obtained by the microwave output unit 110 based on center frequency scanning and frequency modulation output frequency can be used as the analog detection signal.

[0066] Exemplarily, the peak value of the spectrum curve may be used as the estimated value of the spectrum line amplitude.

[0067] The control module 120 can start the center frequency scanning and start the frequency modulation, and at each scanning frequency point, the demodulation phase Nth harmonic demodulation phase φ dem，N Set to 0 to measure I lp，N，i , Q pl，N，i The average value is used as the N-order I and Q signal I at this frequency point. N (v0+v sweep，i ), Q N (v0+v sweep，i ). At each scanning frequency point, the amplitude A of the N-order derivative curve is calculated according to the following formula: N (v0+v sweep，i ) and phase φ N (v0+v sweep，i ):

[0068]

[0069] φ N (v0+v sweep，i )=arg(I N (v0+v sweep，t )+iQ N (v0+v sweep，i ));

[0070] Choose a value greater than the molecular resonance frequency and making the amplitude A of the Nth order derivative curveN (v0+v sweep，i ) Maximum scanning frequency point v sweep，i The phase φ at this scanning frequency point N (v0+v sweep，i ) as the optimal demodulation phase estimation value. The optimal demodulation phase estimation value can also be used as the demodulation phase initial value of the Nth harmonic.

[0071] In this embodiment, Figure 2 As shown, the microwave output unit 110 includes a transmitting module 112, which is used to receive the control of the control module 120 and scan the center frequency of the microwave signal to output an analog detection signal.

[0072] The transmitting module 112 can be used as a frequency synthesis system. The transmitting module 112 performs frequency synthesis on the reference clock signal and outputs a microwave frequency signal close to the molecular resonance frequency to the molecular gas chamber 113. Exemplarily, the transmitting module 112 can also apply center frequency scanning and frequency modulation to the microwave frequency signal.

[0073] Exemplarily, the transmitting module 112 may include a phase-locked loop circuit and a first mixer.

[0074] The phase-locked loop circuit can receive the reference clock of the molecular clock and use it as the input signal of the phase-locked loop circuit. The output signal of the phase-locked loop circuit can be used as the local oscillator input signal of the first mixer. The first mixer mixes the local oscillator input signal and the intermediate frequency input signal to obtain the output signal of the first mixer, and the output signal can be used as the microwave signal output by the transmitting module 112.

[0075] Taking the microwave output unit 110 including a crystal oscillator system 111 as an example, the crystal oscillator system 111 can output a reference clock, and the reference clock can be input into a phase-locked loop circuit as an input signal of the phase-locked loop circuit.

[0076] In this embodiment, the input intermediate frequency input signal may be a low frequency signal with a center frequency scanning function and frequency modulation.

[0077] Exemplarily, the first mixer is also used to receive the control of the control module 120, and mix the output signal of the phase-locked loop circuit with the intermediate frequency input signal obtained by N-fold modulation to obtain the N-th harmonic signal output by the first mixer.

[0078] Exemplarily, the first mixer is also used to receive the control of the control module 120, and mix the output signal of the phase-locked loop circuit with the intermediate frequency input signal based on the first frequency as the frequency step, the first time as the single-step time, the preset number of points as the scanning point number and the preset starting frequency to output a center frequency signal.

[0079] Exemplarily, the intermediate frequency input signal may be generated by a digital frequency synthesizer (Direct Digital Synthesizer, DDS for short).

[0080] Under the central frequency scanning effect, the microwave frequency signal output by the transmitting module 112 can be scanned and obtained, and under the central frequency scanning effect, microwave frequency signals of different frequencies can be obtained.

[0081] Optionally, the center frequency scanning and frequency modulation characteristics may be controlled by the control module 120. Exemplarily, the control module 120 may transmit a signal to the transmitting module 112 of the microwave output unit 110 to control the transmitting module 112 to start the center frequency scanning and frequency modulation through the signal.

[0082] When the center frequency scan is started, the transmitting module 112 of the microwave output unit 110 can obtain a center frequency signal based on the first frequency as frequency stepping, the first time as single step time, the preset number of points as scanning points and the preset starting frequency.

[0083] Optionally, the transmitting module 112 can perform single or multiple scans according to a sawtooth wave based on a specified frequency as frequency step, a specified time as single step time, a preset number of points as scanning points and a preset starting frequency to obtain a center frequency signal.

[0084] When the frequency modulation is enabled, the transmitting module 112 can output an Nth harmonic signal.

[0085] In this embodiment, Figure 2 As shown, the microwave output unit 110 includes a receiving module 114, which is used to detect the microwave signal obtained by scanning to obtain an analog detection signal.

[0086] The receiving module 114 can be used as a detection system. The receiving module 114 receives the microwave frequency signal output by the molecular gas chamber 113 of the microwave output unit 110, and obtains an analog detection signal whose frequency is positively correlated with the power of the received signal through detection.

[0087] Exemplarily, the receiving module 114 may include a voltage-controlled oscillator, a second mixer, and an envelope detector.

[0088] The output signal of the voltage-controlled oscillator is used as the local oscillator input signal of the second mixer; the microwave signal received by the receiving module 114 is used as the radio frequency input signal of the second mixer; the second mixer mixes the local oscillator input signal and the radio frequency input signal and outputs the mixed signal to the envelope detector; the envelope detector detects the received signal and outputs it as the detection signal.

[0089] Optionally, the output signal of the voltage-controlled oscillator may also be used as the local oscillator input signal of the second mixer after frequency multiplication.

[0090] Optionally, the second mixer can mix the local oscillator input signal and the radio frequency input signal and transmit the mixed signals to the envelope detector. The envelope detector can be used to detect and obtain a signal that is positively correlated to the power of the received signal.

[0091] By implementing the above receiving module and the detection processing provided by the envelope detector, the microwave signal can be detected and the output signal can be proportional to the peak value of the input signal.

[0092] In this embodiment, Figure 2 As shown, the microwave output unit 110 may further include a crystal oscillator system 111 and a molecular gas chamber 113 .

[0093] The crystal oscillator system 111 can be connected to the transmitting module 112 to output a crystal oscillator signal to the transmitting module 112, and the transmitting module 112 is also used to output a frequency signal based on the crystal oscillator signal. Exemplarily, the crystal oscillator signal output by the crystal oscillator system 111 can be used as a reference clock and input to the transmitting module 112, and the transmitting module 112 processes it as a reference signal.

[0094] Optionally, the crystal oscillator system 111 may include a crystal oscillator and a frequency synthesis system. The crystal oscillator is used to output a frequency signal. The frequency synthesis system may convert the frequency signal output by the crystal oscillator into a suitable frequency as a clock signal output and a reference clock output.

[0095] In this embodiment, the frequency control signal obtained by the control module 120 is output as an analog control signal to the crystal oscillator system 111 via the digital-to-analog converter 140 to adjust the crystal oscillator frequency output to achieve the adjustment of the clock signal of the molecular clock.

[0096] The molecular gas chamber 113 may be connected between the transmitting module 112 and the receiving module 114 to resonate and absorb microwaves of a specific frequency of the frequency signal of the transmitting module 112 and transmit the processed microwave signal to the receiving module 114 .

[0097] By way of example, the specific frequency may represent a molecular resonance frequency.

[0098] Optionally, the molecular gas chamber 113 may be a sealed cavity with microwave coupling windows, and the windows are connected by microwave waveguides. Exemplarily, the molecular gas chamber 113 may include two microwave coupling windows. Among them, one microwave coupling window can be used as a receiving window and the other as a transmitting window. Exemplarily, the molecular gas chamber 113 may also include only one window, which can realize a common window for transmitting and receiving signals.

[0099] Exemplarily, the molecular gas chamber 113 is filled with a molecular gas of a certain pressure. The transition between the rotational energy levels of the molecules causes the molecules to resonate and absorb microwaves with a frequency close to the molecular resonance frequency.

[0100] See also Figure 3 , is a flow chart of a clock phase demodulation method provided in an embodiment of the present application. The clock phase demodulation method provided in an embodiment of the present application can be applied to a clock, for example, the clock is Figure 1 or Figure 2 The molecular clock shown in the figure is used to perform the steps in the clock phase demodulation method. The molecular clock is used as an example for the following description. Figure 3 The example shown is used to explain in detail the specific process of the clock phase demodulation method provided in the embodiment of the present application.

[0101] Step 210: Determine an initial demodulation phase value of the Nth harmonic based on the Nth harmonic signal output by the clock.

[0102] Wherein, N is a positive integer and an odd number.

[0103] Optionally, at each scanning frequency point, the amplitude and phase of the signal curve can be calculated based on the Nth harmonic signal and the detection signal of the clock output; from the amplitudes of the signal curve calculated at each scanning frequency point, a third target amplitude whose amplitude of the signal curve meets the set conditions is selected, and the phase at the scanning frequency point where the third target amplitude is located is used as the initial value of the demodulation phase.

[0104] The scanning frequency point is determined by configuring the scanning frequency condition in the process of outputting microwave signals by the clock and is determined by the scanning frequency condition.

[0105] Optionally, a set of third target scanning frequency points greater than the molecular resonance frequency can be determined from a plurality of scanning frequency points, and the signal curve with the largest amplitude is determined as the third target amplitude according to the amplitude of the signal curve of each third target scanning frequency point in the set of third target scanning frequency points. The molecular resonance frequency is determined by the spectrum curve formed by the detection signal output by the clock.

[0106] For example, the amplitude A of the derivative curve of the Nth harmonic signal N (v0+v sweep，i ) and phase φ N (v0+v sweep，i ) can be expressed as the following formula:

[0107]

[0108] φ N (v0+v sweep，i )=arg(I N(v0+v sweep，i )+iQ N (v0+v sweep，i ));

[0109] Choose a value greater than the molecular resonance frequency and making the amplitude A of the Nth order derivative curve N (v0+v sweep,t ) Maximum scanning frequency point v sweep,t The phase φ at this scanning frequency point N (v0+v sweep,t ) as the optimal demodulation phase estimation value. The optimal demodulation phase estimation value can also be used as the demodulation phase initial value of the Nth harmonic.

[0110] Step 220: Based on the Mth harmonic signal output by the clock, determine a first phase change value of the Mth harmonic signal that changes with time.

[0111] M is a positive integer and an even number. Optionally, M can be any even number. Of course, in order to reduce the amount of calculation, the even number can be a smaller even number, for example, the value of M can be 2, 4, etc.

[0112] The first phase change value may be a phase change between the Mth harmonic signal at an initial time and a current time. The initial time may be a time for determining an initial value of the demodulated phase, or a time for determining an initial phase value of the Mth harmonic signal as a reference.

[0113] It is understandable that the calculated first phase change value may be different as the clock running time is different.

[0114] Step 230: Based on the Lth harmonic signal output by the clock, determine a second phase change value of the Lth harmonic signal that changes with time.

[0115] Wherein, M and L are positive integers and are even numbers.

[0116] Optionally, L can be any even number, and L can be an even number different from M. Of course, in order to reduce the amount of calculation, the even number can be a smaller even number, for example, when M can be 2, the value of L can be 4; when M can be 4, the value of L can be 6, etc.

[0117] The second phase change value may be a phase change between the Lth harmonic signal at the initial moment and the current moment.

[0118] The first phase change value and the second phase change value may be determined in a similar manner, except that they are determinations of phase changes of different sub-harmonics.

[0119] Step 240, calculating a target demodulation phase based on the demodulation phase initial value, the first phase change value, and the second phase change value.

[0120] The target demodulation phase is the demodulation phase used when the Nth harmonic is used for frequency locking.

[0121] In an optional implementation, step 240 may include step 241 and step 242 .

[0122] Step 241: Determine a target phase change value of the Nth harmonic according to the first phase change value and the second phase change value.

[0123] Optionally, the target phase change value is determined by the following formula:

[0124]

[0125] in, Indicates the target phase change value; represents a second phase change value; Indicates the first phase change value.

[0126] Optionally, the target phase change value is determined by the following formula:

[0127]

[0128] in, Indicates the target phase change value after unwrapping; represents the first phase change value after unwinding; Represents the second phase change value after unwrapping.

[0129] Step 242, determining a target demodulation phase according to the target phase change value and the demodulation phase initial value.

[0130] The target demodulation phase can be expressed by the following formula:

[0131]

[0132] in, Indicates the calculated real-time optimal demodulation phase, which can be used as the target demodulation phase; Indicates the initial value of the demodulation phase corresponding to the Nth harmonic; Indicates the target phase change value after unwrapping corresponding to the Nth harmonic.

[0133] The following analyzes the relationship between the phase of odd-order harmonics and the phase of Euler-order harmonics in combination with the characteristics of harmonic signals.

[0134] The detection signal of the odd-numbered Nth harmonic of the modulation frequency of the detection signal used for frequency locking can be:

[0135]

[0136] Among them, U det,N A represents the detection signal of the Nth harmonic; det,N Represents the amplitude of the detection signal of the Nth harmonic; f m Indicates the modulation frequency; φ m Indicates the phase of the modulated signal; φ PLL represents the angle of the closed-loop transfer function of the phase-locked loop at the modulation frequency; φ0 represents the random additional phase determined by the power-on timing; φ spectrum，N represents the additional phase of the Nth harmonic caused by modulation and demodulation; k filter Represents the slope of the filter's phase-frequency characteristic; φ filter，0 It represents the intercept of the phase-frequency characteristic of the filter; t represents the running time.

[0137] The phase of the Nth harmonic expressed as cosine can be shown as follows:

[0138]

[0139] φ′≡φ m +φ PLL (t)+φ0+k filter (t)f m ;

[0140] φ″=φ filter，0 (t).

[0141] It can be determined from the above formula that the phase of the Nth harmonic can contain only two degrees of freedom, namely: φ′≡φ m +φ PLL (t)+φ0+k fllter (t)f m and φ″≡φ fllter，0 Based on this, the phase characteristics of any two even-order M and L harmonics can be used to estimate the optimal demodulation phase of the odd-order N harmonic.

[0142] From this we can determine that:

[0143] The phase of odd-order harmonics can be expressed using two terms of the phase of even-order harmonics:

[0144]

[0145] Furthermore, due to the characteristic that the phase changes slowly with time and the amplitude is small (i.e. the phase change will not exceed 2π in a short time), when only considering the change of each phase, we have:

[0146]

[0147] in, Respectively express The result after unwinding; Respectively The amount of change.

[0148] From this we can determine:

[0149] Based on the above analysis, it can be determined that the phase change of the even-order harmonics can be used to estimate the phase change of the odd-order harmonics.

[0150] In the above manner, by utilizing the relationship between the phases of even-order harmonics and odd-order harmonics, the change in the phase of odd-order harmonics can be estimated based on the change in the phase of even-order harmonics.

[0151] In an optional implementation, the above step 220 may include steps 221 to 223 .

[0152] Step 221: Determine a first initial phase value of the Mth harmonic signal based on the Mth harmonic signal output by the clock.

[0153] Step 222: Based on a set algorithm, a phase estimation is performed on the Mth harmonic signal output in real time to obtain a first phase estimation value of the Mth harmonic signal.

[0154] Step 223: Determine a first phase change value of the Mth harmonic signal according to the first initial phase value and the first phase estimated value.

[0155] The above step 221 may include: at each scanning frequency point, according to the Mth harmonic signal and the detection signal output by the clock, calculating the amplitude and phase of the signal curve; from the amplitude of the signal curve calculated at each scanning frequency point, selecting the first target amplitude of the signal curve whose amplitude meets the set condition, and taking the phase at the scanning frequency point where the first target amplitude is located as the first initial phase value. The scanning frequency point is determined by configuring the scanning frequency condition in the process of the clock outputting the microwave signal and the scanning frequency condition.

[0156] Optionally, a set of first target scanning frequency points greater than the molecular resonance frequency is determined from multiple scanning frequency points; and according to the amplitudes of the signal curves of each first target scanning frequency point in the set of first target scanning frequency points, the signal curve with the largest amplitude is determined as the first target amplitude.

[0157] The molecular resonance frequency is determined by the spectrum curve formed by the detection signal output by the clock.

[0158] The amplitude and phase of the signal curve of the Mth harmonic can be calculated by the following formula:

[0159]

[0160] Among them, v sweep，i represents the i-th scanning frequency point; v0 represents the center frequency value; I M (v0+v sweep，i ) indicates that at the scanning frequency point v sweep，i I signal under; Q M (v0+v sweep，i ) means that at the Mth harmonic, at the scanning frequency point v sweep，i Q signal under; A M (v0+v sweep，i ) means that at the Mth harmonic, at the scanning frequency point v sweep，i The amplitude of the signal curve below; φ M (v0+v sweep，i ) means that at the Mth harmonic, at the scanning frequency point v sweep，i The next phase.

[0161] Optionally, the above step 222 may include: using a set algorithm to calculate the Mth harmonic signal output in real time to obtain a phase estimation value of the Mth harmonic signal; and performing unwrapping processing on the phase estimation value to obtain a first phase estimation value.

[0162] Optionally, Fourier transform may be used to calculate the Mth harmonic signal output in real time to obtain a phase estimation value of the Mth harmonic signal.

[0163] In an optional implementation, the above step 230 may include steps 231 to 233 .

[0164] Step 231: Determine a second initial phase value of the Lth order harmonic signal based on the Lth order harmonic signal output by the clock.

[0165] Step 232: Based on the set algorithm, the phase of the Lth harmonic signal output in real time is estimated to obtain a second phase estimation value of the Lth harmonic signal.

[0166] Step 233: Determine a second phase change value of the Lth harmonic signal according to the second initial phase value and the second phase estimated value.

[0167] The above-mentioned step 231 may include: at each scanning frequency point, calculating the amplitude and phase of the signal curve according to the Lth harmonic signal and the detection signal output by the clock; from the amplitudes of the signal curve calculated at each scanning frequency point, selecting a second target amplitude of the signal curve whose amplitude meets the set conditions, and using the phase at the scanning frequency point where the second target amplitude is located as the second initial phase value.

[0168] The scanning frequency point is determined by configuring the scanning frequency condition in the process of outputting microwave signals by the clock and is determined by the scanning frequency condition.

[0169] Optionally, a set of second target scanning frequency points greater than the molecular resonance frequency can be determined from a plurality of scanning frequency points; and according to the amplitude of the signal curve of each second target scanning frequency point in the set of second target scanning frequency points, the signal curve with the largest amplitude is determined as the second target amplitude. The molecular resonance frequency is determined by the spectrum curve formed by the detection signal output by the clock.

[0170] The amplitude and phase of the Lth harmonic signal curve can be calculated by the following formula:

[0171]

[0172] Among them, v sweep，i represents the i-th scanning frequency point; v0 represents the center frequency value; I L (v0+v sweep，i ) indicates that at the scanning frequency point v sweep,i I signal under; Q L (v0+v sweep，i ) means that at the Lth harmonic, at the scanning frequency point v sweep，i Q signal under; A L (v0+v sweep,i ) means that at the Lth harmonic, at the scanning frequency point v sweep,i The amplitude of the signal curve below; φ L (v0+v sweep,i ) means that at the Lth harmonic, at the scanning frequency point v sweep，i The next phase.

[0173] Optionally, the above step 232 may include: using a set algorithm to calculate the Lth harmonic signal output in real time to obtain a phase estimation value of the Lth harmonic signal; and performing unwrapping processing on the phase estimation value to obtain a second phase estimation value.

[0174] Optionally, Fourier transform may be used to calculate the Lth harmonic signal output in real time to obtain a phase estimation value of the Lth harmonic signal.

[0175] Through the above method provided in the embodiment of the present application, it is possible to realize the demodulation phase synchronization function during the normal locking process of the clock frequency, reduce the sensitivity of the clock frequency stability to environmental factors and the aging of the clock frequency stability. Under this scheme, no low-frequency signal is required to realize the phase synchronization function, and the frequency deviation caused by electromagnetic coupling is avoided. Since the phase calculation of the odd-order harmonics that need to be locked is not required, there is no need to occupy the frequency locking time, and the deterioration of the clock frequency locking performance is avoided. In the embodiment of the present application, the nonlinearity of the spectral line type is utilized, and the even-order IQ signal is used as the error signal of the odd-order demodulation phase to realize the demodulation phase synchronization function during the normal locking process of the clock frequency, and reduce the sensitivity of the clock frequency stability to environmental factors and the aging of the clock frequency stability. The phase change amount is used as the estimated value to avoid the problem of mislocking caused by the multi-valued nature of the phase calculation.

[0176] The above description is only an optional embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0177] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A clock phase demodulation method, characterized in that: Applied to clock, the clock phase demodulation includes: Based on the Nth harmonic signal output by the clock, determine the initial value of the demodulation phase of the Nth harmonic; wherein N is a positive integer and an odd number; Based on the Mth harmonic signal output by the clock, determining a first phase change value of the Mth harmonic signal that changes with time; Based on the Lth harmonic signal output by the clock, determine a second phase change value of the Lth harmonic signal that changes with time; wherein M and L are positive integers and are even numbers; Based on the demodulation phase initial value, the first phase change value and the second phase change value, a target demodulation phase is calculated; wherein the target demodulation phase is the demodulation phase used when frequency locking is performed using an Nth harmonic.

2. The method according to claim 1, characterized in that The step of calculating a target demodulation phase based on the demodulation phase initial value, the first phase change value, and the second phase change value comprises: Determining a target phase change value of the Nth harmonic according to the first phase change value and the second phase change value; A target demodulation phase is determined according to the target phase change value and the demodulation phase initial value.

3. The method according to claim 2, characterized in that The target phase change value is determined by the following formula: in, Indicates the target phase change value; represents a second phase change value; Indicates the first phase change value.

4. The method according to claim 1, characterized in that: The step of determining a first phase change value of the Mth harmonic signal that varies with time based on the Mth harmonic signal output by the clock includes: Based on the Mth harmonic signal output by the clock, determining a first initial phase value of the Mth harmonic signal; Based on a set algorithm, a phase estimation is performed on the Mth harmonic signal output in real time to obtain a first phase estimation value of the Mth harmonic signal; A first phase change value of the Mth harmonic signal is determined according to the first initial phase value and the first phase estimated value.

5. The method according to claim 4, characterized in that The step of determining a first initial phase value of the Mth harmonic signal based on the Mth harmonic signal output by the clock includes: At each scanning frequency point, the amplitude and phase of the signal curve are calculated according to the Mth harmonic signal and the detection signal output by the clock; wherein the scanning frequency point is determined by configuring the scanning frequency condition in the process of the clock outputting the microwave signal; A first target amplitude of the signal curve that satisfies a set condition is selected from the amplitudes of the signal curve calculated at each scanning frequency point, and the phase at the scanning frequency point where the first target amplitude is located is used as a first initial phase value.

6. The method according to claim 5, characterized in that The step of selecting a first target amplitude whose amplitude of the signal curve satisfies a set condition from the amplitudes of the signal curve calculated at each scanning frequency point comprises: Determine a set of first target scanning frequency points greater than the molecular resonance frequency from the plurality of scanning frequency points; wherein the molecular resonance frequency is determined by a spectrum curve formed by a detection signal output by the clock; According to the amplitudes of the signal curves of the first target scanning frequency points in the set of the first target scanning frequency points, the signal curve with the largest amplitude is determined as the first target amplitude.

7. The method according to claim 5, characterized in that The amplitude and phase of the signal curve are calculated by the following formula: Among them, v sweep，i represents the i-th scanning frequency point; v0 represents the center frequency value; I M (v0+v swepp，i ) indicates that at the scanning frequency point v sweep，i I signal under; Q M (v0+v sweep，i ) means that at the Mth harmonic, at the scanning frequency point v sweep，i Q signal under; A M (v0+v sweep，i ) means that at the Mth harmonic, at the scanning frequency point v sweep，i The amplitude of the signal curve below; φ M (v0+v sweep，i ) means that at the Mth harmonic, at the scanning frequency point v sweep，i The next phase.

8. The method according to claim 4, characterized in that The method of performing phase estimation on the Mth harmonic signal output in real time based on the set algorithm to obtain a first phase estimation value of the Mth harmonic signal includes: Using a set algorithm to calculate the Mth harmonic signal output in real time, to obtain a phase estimation value of the Mth harmonic signal; The phase estimate is unwrapped to obtain a first phase estimate.

9. The method according to claim 8, characterized in that The method of calculating the Mth harmonic signal output in real time by using a set algorithm to obtain a phase estimation value of the Mth harmonic signal includes: The Mth harmonic signal output in real time is calculated by using Fourier transform to obtain a phase estimation value of the Mth harmonic signal.

10. A molecular clock, characterized in that: include: Microwave output unit, digital-to-analog converter, control module and analog-to-digital converter; The microwave output unit is used to output analog detection signals and clock signals; The analog-to-digital converter is used to convert the analog detection signal output by the microwave output unit into a digital detection signal; The control module is used to determine a frequency control signal using the method described in any one of claims 1 to 9 to control the microwave output unit; A digital-to-analog converter is used to convert the frequency control signal calculated by the control module into an analog control signal, and transmit the analog control signal to the microwave output unit to adjust the clock signal output by the microwave output unit.

11. The molecular clock according to claim 10, characterized in that: The microwave output unit comprises: A transmitting module, used to receive control from the control module and scan the center frequency of the microwave signal; A crystal oscillator system connected to the transmitting module, used to output a crystal oscillator signal to the transmitting module, and the transmitting module is also used to output a frequency signal based on the crystal oscillator signal; A receiving module, used for detecting the microwave signal obtained by scanning to obtain an analog detection signal; The molecular gas chamber connected between the transmitting module and the receiving module is used for resonantly absorbing microwaves of a specific frequency of the frequency signal of the transmitting module and transmitting the processed microwave signal to the receiving module.

Images