A method for frequency synthesis of even-order signals with low phase noise and low spurious

Abstract

The present invention discloses a method for frequency synthesis of even-order signals with low phase noise and low spurious signals, which belongs to the field of frequency synthesis technology and comprises the steps of: utilizing an anti-phase coherent reference signal input to a comb generator to generate a comb signal with odd-order inversion and even-order in-phase characteristics, and adopting an in-phase coupler to perform power synthesis. Because power synthesis is vector superposition, the in-phase signal is superimposed and the anti-phase signal is cancelled, thereby realizing even-order signal extraction and odd-order signal suppression, thereby realizing half reduction of the spurious frequency points of the comb spectrum, doubling the frequency difference between adjacent spurious points of the main signal and the main signal, reducing the difficulty of filter design and reducing the implementation volume. At the same time, a narrowband coupler is utilized to reflect the signal outside the passband and has no parasitic passband characteristics, thereby solving the problem of far-end parasitic passband in a single-stage bandpass filter, filtering out the near-end and far-end spurious of the main signal, and realizing frequency synthesis with higher spurious suppression and lower phase noise in a smaller volume.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency synthesis, and more specifically to a method for synthesizing the frequency of even-order signals with low phase noise and low spurious emission. Background Art

[0002] Frequency synthesis technology is widely used in modern electronic information systems, including communications and radar. In heterodyne and superheterodyne frequency conversion systems, the performance of the frequency source directly impacts key metrics such as system sensitivity and range. With technological advancements and the widespread adoption of integrated detection, interference, exploration, and communication applications, these systems are increasingly demanding lower phase noise and higher spurious suppression from frequency sources.

[0003] Frequency synthesis technology includes indirect frequency synthesis technology (phase-locked loop), direct digital frequency synthesis technology (DDS) and direct frequency synthesis technology.

[0004] Indirect frequency synthesis, also known as phase-locked loop (PLL) frequency synthesis, utilizes a phase detector, loop filter, and voltage-controlled oscillator to form a phase-locked loop (PLL). Externally controlled, the PLL locks to a stable output frequency. While it offers advantages such as low cost and simplicity, it is limited by the performance of the digital phase detector, making it difficult to improve phase noise and spurious signal suppression, making it difficult to directly meet the demands of high-performance applications. Direct digital frequency synthesis uses a DA to generate the output frequency, enabling extremely fine Hz steps. However, due to the limitations of digital components, it is difficult to improve phase noise and spurious signal suppression. Furthermore, the peripheral circuitry is complex, requiring significant hardware requirements, making it difficult to meet the demands of high-performance, miniaturized applications. Direct frequency synthesis uses mixing, multiplication, and division to perform addition, subtraction, multiplication, and division operations on a reference signal, eliminating the need for an additional digital noise floor. However, due to the influence of active components in the synthesis chain, the output signal phase noise can deteriorate to varying degrees compared to theoretically calculated values. Furthermore, all frequencies in direct frequency synthesis are generated analogously, generating a significant number of spurious signals that must be filtered separately. This makes filter design challenging, necessitating significant hardware requirements, and the size of the implementation increases exponentially with improved spurious signal suppression.

[0005] Existing low spurious and low phase noise frequency synthesis reports are as follows:

[0006] In 2016, Zhao Yani published a paper titled "Design of a Low-Phase-Noise, Low-Spurious 650MHz Point-Frequency Source." The proposed solution uses a phase-locked loop (PLL) with integer phase detection to generate a 650MHz point-frequency source. This approach is simple and easy to implement. However, it cannot avoid the impact of the phase detector on the near-end phase noise of the synthesizer circuit. The measured phase noise is -116dBc / Hz at 1kHz and -114dBc / Hz at 10kHz, significantly worse than a direct-combination solution at the same frequency, making further improvement difficult.

[0007] In 2017, Zhou Min et al. published the paper "Design and Verification of a Low-Phase-Noise Frequency Source." The proposed scheme is a typical direct frequency synthesis circuit, using cascaded comb lines to generate the desired frequency. The input reference is 100 MHz, the output signal is 8 GHz, and the effective frequency multiplication is 80 times. This is achieved using a two-stage comb line generator. Comb line generator 1 generates a 1 GHz intermediate frequency. With a reference input of 100 MHz, spurious signals at 0.9 GHz and 1.1 GHz near 1 GHz exist, requiring bandpass filter 1 to filter them out. Bandpass filter 1 suppresses out-of-band spurious signals at frequencies 1 / 10 of the main signal frequency on either side of 1 GHz. Furthermore, these spurious signals cannot be processed by subsequent circuits and are coupled to the final output via comb line generator 2. Given the same structure, filter order is positively correlated with out-of-band suppression. Higher out-of-band suppression requires higher filter order and larger size. Furthermore, when the filter order exceeds 5, the increase in out-of-band suppression achieved by simply increasing the filter order significantly decreases, making the design of high-suppression filters difficult and challenging. Bandpass filter 1 in this paper is bulky and difficult to optimize. Furthermore, while the paper uses cascaded comb lines to achieve the final frequency output, while this eliminates the noise floor introduced by digital devices, the circuit's extensive use of amplifiers and comb line generators introduces an additional 6dB of phase noise, making further optimization difficult. Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for frequency synthesis of even-order signals with low phase noise and low spurious emission, so as to achieve frequency synthesis with higher spurious suppression and lower phase noise in a smaller volume.

[0009] The object of the present invention is achieved through the following solutions:

[0010] A method for frequency synthesis of even-order signals with low phase noise and low spurious emission, comprising the steps of:

[0011] Step 1: Establish a low phase noise, low spurious even-order signal frequency synthesis circuit: connect the anti-phase coupler C1 to the amplifier circuit A1 and the amplifier circuit A2 respectively; connect the amplifier circuit A1 to the comb line generator 1, connect the comb line generator 1 to the transmission circuit B1, and connect the transmission circuit B1 to the narrowband in-phase coupler C2; connect the amplifier circuit A2 to the comb line generator 2, connect the comb line generator 2 to the transmission circuit B2, connect the transmission circuit B2 to the narrowband in-phase coupler C2, connect the narrowband in-phase coupler C2 to the bandpass filter F1, connect the bandpass filter F1 to the extremely narrow bandpass filter F2, and connect the extremely narrow bandpass filter F2 to the constant temperature circuit T1;

[0012] Step 2: Low noise reference signal f ref The power is divided by the inverting coupler C1 to generate two equal-amplitude inverted reference signals, expressed as cosω ref t and cos(ωref t+180°), two equal-amplitude and inverted reference signals are respectively passed through amplifier circuit A1 and amplifier circuit A2, and the amplitudes of A1 and A2 are respectively amplified, and additional phase offset is introduced.

[0013] Step 3: The input reference signals of comb generator 1 and comb generator 2 are equal in amplitude and inverted in phase, and the phase difference of the odd-order comb signals generated by comb generator 1 and comb generator 2 is (2N+1)*180°, that is, inverted; the phase difference of the even-order comb signals is 2N*180°=N*360°, that is, in phase, where N is an integer; the wide-spectrum comb signals output by comb generator 1 and comb generator 2 are respectively transmitted through transmission circuit B1 and transmission circuit B2 to coupler C2, and phase offset is introduced respectively. and The two sets of comb line signals are transmitted to the input end of coupler C2 through transmission circuits B1 and B2, with odd-order signals kept in anti-phase and even-order signals kept in phase;

[0014] Step 4: Use narrowband in-phase coupler C2 to perform power synthesis on the wide spectrum comb line. The original inverted odd-order comb line signals are vector-superimposed and canceled in C2; the original in-phase even-order comb line signals are vector-superimposed and multiplied in C2; the main signal 2Nf in the comb line signal output by C2 is ref The spurious signals on both sides are 2(N-1)f ref and 2(N+1)f ref , 2f frequency difference from the main signal ref , compared with the stray frequency difference f of a single comb line generator ref Double;

[0015] Step 5: Cascade the bandpass filter F1 at the output of C2. The passband frequency of the bandpass filter is 2Nf. ref , filter out the frequency difference 2f on both sides of the main signal ref and far-end spurious.

[0016] Furthermore, the phase shift introduced by the amplifier circuit A1 and the amplifier circuit A2 is the same. The two amplifier circuits use equipment of the same model and batch, and have the same gain at the same frequency point, A1=A2.

[0017] Furthermore, comb generators 1 and 2 use the same model and batch of equipment. In this scheme, under the condition of equal-amplitude and inverted-phase reference input, the generated comb spectrum signals have the same frequency and amplitude, with odd-order phase difference of (2N+1)*180°, indicating anti-phase; and even-order phase difference of 2N*180°, indicating in-phase.

[0018] Furthermore, the transmission circuit B1 and the transmission circuit B2 are symmetrical, and for the same frequency comb point frequency, the introduced phase offset is the same.

[0019] Furthermore, the center frequency of the operating frequency band of the narrowband coupler C2 is the synthetic signal frequency 2Nf ref , it has suppression and reflection effects on signals outside the passband, and has no parasitic passband.

[0020] Furthermore, the parasitic passband of the bandpass filter F1 is outside the passband of the narrowband coupler C2, and the narrowband coupler C2 cooperates with the bandpass filter F1 to generate the 2(N+1)f ref It effectively suppresses other high-order comb signals and has no parasitic passband as a whole.

[0021] Furthermore, the extremely narrow bandpass filter F2 is cascaded with the bandpass filter F1, and the output end is the output of the entire circuit; the extremely narrow bandpass filter F2 is used to filter out the main signal 2Nf ref The additional noise introduced by the active devices on both sides of the near end is optimized to optimize the output signal phase noise.

[0022] Furthermore, the extremely narrow bandpass filter F2 adopts any one of a surface acoustic wave filter, a crystal filter, and a thin film bulk acoustic wave resonator filter.

[0023] Furthermore, the constant temperature circuit T1 realizes the stable working temperature of the extremely narrow bandpass filter F2, reduces the temperature drift of the extremely narrow passband, and makes the main signal frequency 2Nf ref Both high and low temperatures are within the F2 passband frequency.

[0024] Furthermore, the passband frequencies of the extremely narrow bandpass filter F2 are set at the kHz level, the 10kHz level and the 100kHz level, respectively forming effective out-of-band suppression for the 10kHz, 100kHz and 1MHz positions on both sides of the frequency-deviation main signal.

[0025] The beneficial effects of the present invention include:

[0026] The technical solution of the present invention proposes a low-phase-noise, low-spurious even-order signal frequency synthesis method, which uses an inverted reference input comb generator to generate an odd-order signal inverted and an even-order signal in phase, and adopts a co-phase coupler to realize odd-order signal synthesis cancellation and even-order signal synthesis superposition, thereby reducing the spectral spurious of the comb signal, extending the interval frequency between signals, reducing the difficulty of filter design, reducing the implementation volume, and improving the spurious suppression of the synthesis circuit.

[0027] The present invention's technical solution phase-coheres even-order signals at the input coupler, synthesizes the main signal, and superimposes its power, improving it by 3dB. The random noise floor introduced by the amplifier and comb generator is uncorrelated and does not superimpose. The main signal power is increased by 3dB within the 1Hz spectrum relative to the noise floor, and phase noise is optimized by 3dB.

[0028] The technical solution of the present invention utilizes a narrowband coupler to reflect out-of-band signals without parasitic passband characteristics, and cooperates with a subsequent single-stage bandpass filter to effectively suppress the near-end and far-end signals of the comb spectrum, thereby solving the problem of high-order comb spectrum signals leaking through the parasitic passband of the single-stage bandpass filter.

[0029] In addition, the constant temperature circuit T1 is used in conjunction with the extremely narrow bandpass filter F2 to solve the problem of main signal suppression caused by the extremely narrow bandpass filter's narrow passband and easy temperature drift, and effectively filter out the additional noise near the main signal at all temperatures, further improving the output signal spectrum purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 A circuit diagram of an embodiment of the present invention;

[0032] Figure 2 Schematic diagram of optimizing output signal spurious suppression according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] All features disclosed in all embodiments in this specification, or steps in all methods or processes implicitly disclosed, except for mutually exclusive features and / or steps, can be combined and / or expanded or replaced in any manner.

[0034] After creative thinking, the inventors of the present invention realized that direct frequency synthesis technology has no additional noise from digital devices and does not require control, but there are the following implementation difficulties to be overcome.

[0035] 1) It is difficult to improve spurious suppression. Direct coupling uses mixing, multiplication, and division to achieve frequency addition, subtraction, multiplication, and division operations, but it introduces a large number of spurious signals, which need to be filtered out by filters. The closer the spurious frequency is to the main signal, the higher the Q value of the required filter waveform coefficient, and high spurious suppression cannot be achieved by directly increasing the filter order. The difficulty of filter design and the implementation space increase with the increase in spurious suppression requirements. Secondly, in the direct coupling scheme of the comb generator, the output of the comb generator is a multiple-order integer multiple of the input signal, and the spectrum is rich. Although the bandpass filter can extract the main signal and filter out near-end spurious signals, there is a far-end parasitic passband. There is leakage of high-order comb signals in the parasitic passband, which requires additional processing, further increasing the implementation volume.

[0036] 2) Additional phase noise is difficult to filter out. The use of active devices in direct frequency synthesis circuits will introduce additional noise deterioration of 5dB to 10dB. System applications usually focus on the phase noise at 10kHz and 100kHz frequency offsets on both sides of the main signal. The higher the frequency of the output main signal, the smaller the relative frequency difference of the 10kHz and 100kHz frequency offsets relative to the main signal. If a filter is used for filtering, the filter passband must be extremely narrow. At room temperature, this can be achieved using technical means such as surface acoustic wave filters, crystal filters, and thin film bulk acoustic wave resonator filters. However, all of the above filters have temperature drift. Under extremely narrow relative bandwidth conditions, ambient temperature fluctuations will cause the filter passband to drift away from the main signal frequency, resulting in high loss and high suppression of the main signal, making it difficult to meet usage requirements.

[0037] In order to solve the above technical problems and achieve frequency synthesis with higher spurious suppression and lower phase noise in a smaller volume, the present invention proposes a low phase noise, low spurious even-order signal frequency synthesis method, which uses the characteristics of odd-order inversion and even-order in-phase of the comb signal generated by the inverse-phase reference signal input comb generator, and adopts an in-phase coupler for power synthesis. Because power synthesis is vector superposition, the in-phase signal is superimposed and the inverse-phase signal is cancelled, which realizes the extraction of even-order signals and the suppression of odd-order signals, and reduces the spurious frequency points of the comb spectrum by half. The frequency difference between the adjacent spurious points of the main signal is doubled compared with the main signal, which reduces the difficulty of filter design and reduces the implementation volume. At the same time, the narrowband coupler is used to reflect the signal outside the passband and has no parasitic passband characteristics, which solves the problem of far-end parasitic passband in the single-stage bandpass filter and filters out the near-end and far-end spurs of the main signal.

[0038] At the same time, the even-order signals from the input coupler are added in phase, increasing their power by 3dB. However, the random noise floor introduced by active components such as the comb generator is uncorrelated and does not add. The increase in the main signal power within the 1Hz spectrum relative to the noise floor results in an increase in phase noise. The circuit of the present invention achieves a 3dB improvement in phase noise compared to a direct frequency synthesis solution that does not employ the present invention's techniques.

[0039] Furthermore, considering the temperature drift of the extremely narrow filter used to filter out additive noise, a temperature-stable, extremely narrow bandpass filter is implemented in conjunction with a constant-temperature circuit. This reduces the filter's passband temperature drift and filters out additive noise introduced by active components near the main signal, further improving the output signal's spectral purity. The circuit of this invention enables high-performance frequency synthesis with low phase noise and spurious signals in a compact package.

[0040] In a specific embodiment, the technical solution of the present invention proposes a low phase noise, low spurious even-order signal frequency synthesis circuit, comprising a 3dB anti-phase coupler C1, an amplifier circuit A1, an amplifier circuit A2, a comb line generator 1, a comb line generator 2, a transmission circuit B1, a transmission circuit B2, a 3dB narrowband in-phase coupler C2, a bandpass filter F1, an extremely narrow bandpass filter F2, and a constant temperature circuit T1. Figure 1 , Figure 2 shown.

[0041] In a further embodiment of the invention, C1 is a 3dB anti-phase coupler, and the low noise reference signal f ref The power is divided by coupler C1 to generate two equal-amplitude and anti-phase reference signals, which are expressed as cosω. ref t and cos(ω ref t+180°).

[0042] In a further embodiment of the invention, the two inverted reference signals are respectively amplified by the amplifier circuit A1 and the amplifier circuit A2, and the amplitudes of A1 and A2 are respectively amplified, and an additional phase offset is introduced. The present invention adopts a symmetrical design, and the two amplifier circuits introduce the same phase shift. The two amplifier circuits use equipment of the same model and batch, with the same gain at the same frequency point, A1=A2.

[0043] In a further embodiment of the invention, the input reference signals of comb line generators 1 and 2 are of equal amplitude and opposite phase, and the comb line generators 1 and 2 utilize the same model and batch of equipment. The phase difference of the odd-order comb line signals generated by comb line generators 1 and 2 is (2N+1)*180°, i.e., they are out of phase; the phase difference of the even-order comb line signals is 2N*180°=N*360°, i.e., they are in phase, where N is an integer.

[0044] In a further embodiment of the invention, the broadband comb line signals outputted by comb line generator 1 and comb line generator 2 are respectively transmitted through transmission circuit B1 and transmission circuit B2 to coupler C2, and phase shift is introduced respectively. and In the present invention, the transmission circuits B1 and B2 are symmetrical, and for the same frequency comb point frequency, the introduced phase offset is the same. The two groups of comb line signals are transmitted to the input end of the coupler C2 through the transmission circuits B1 and B2. The odd-order signals remain in anti-phase, and the even-order signals remain in phase.

[0045] In a further invention concept, a 3dB narrowband in-phase coupler C2 is used to synthesize power. The original inverted odd-order comb line signals are vector-superimposed and canceled in C2; the original in-phase even-order comb line signals are vector-superimposed and multiplied in C2. The main signal 2Nf in the comb line signal output by C2 is ref The spurious signals on both sides are 2(N-1)f refand 2(N+1)f ref , 2f frequency difference from the main signal ref , compared with the stray frequency difference f of a single comb line generator ref Double.

[0046] In a further embodiment of the invention, a bandpass filter F1 is connected to the output of C2, and the center frequency of the bandpass filter is 2Nf. ref , filter out the frequency difference 2f on both sides of the main signal ref and far-end spurious.

[0047] In a further embodiment of the invention, C2 is a narrowband coupler, and the center frequency of the working frequency band is the composite signal frequency 2Nf ref , it has the function of suppressing and reflecting the signals outside the passband, and has no parasitic passband. The parasitic passband of the bandpass filter F1 is outside the passband of the narrowband coupler C2. The narrowband coupler C2 cooperates with the bandpass filter F1 to generate the 2(N+1)f ref It effectively suppresses other high-order comb signals and has no parasitic passband.

[0048] In a further embodiment of the invention, an extremely narrow bandpass filter F2 is connected in cascade to the bandpass filter F1, and the output end is the output of the entire circuit. F2 is used to filter out the main signal 2Nf ref The additional noise introduced by the active devices on both sides of the near end is optimized to optimize the output signal phase noise.

[0049] Optionally, the extremely narrow bandpass filter F2 may be implemented by a high-Q filter such as a surface acoustic wave filter, a crystal filter, or a thin film bulk acoustic wave resonator filter.

[0050] Optionally, the passband frequency of the extremely narrow bandpass filter can be set at the kHz level, the 10kHz level and the 100kHz level, respectively forming effective out-of-band suppression for the 10kHz, 100kHz and 1MHz positions on both sides of the frequency-deviation main signal.

[0051] In a further inventive concept, the constant temperature circuit T1 realizes the working temperature stability of the extremely narrow bandpass filter F2, reduces the temperature drift of the extremely narrow passband, and makes the main signal frequency 2Nf ref Both high and low temperatures are within the F2 passband frequency.

[0052] In the actual project product development and research, a 1GHz low phase noise and low spurious point frequency source circuit was also developed using the technical solution of the present invention. The phase noise is better than -133dBc / Hz@1kHz, and the spurious suppression reaches -70dBc, which better meets the needs of engineering applications.

[0053] It should be noted that within the scope of protection defined in the claims of the present invention, the following embodiments can be combined and / or expanded or replaced in any logical way from the above specific implementation methods, such as disclosed technical principles, disclosed technical features or implicitly disclosed technical features.

[0054] Example 1

[0055] A method for frequency synthesis of even-order signals with low phase noise and low spurious emission, comprising the steps of:

[0056] Step 1: Establish a low phase noise, low spurious even-order signal frequency synthesis circuit: connect the anti-phase coupler C1 to the amplifier circuit A1 and the amplifier circuit A2 respectively; connect the amplifier circuit A1 to the comb line generator 1, connect the comb line generator 1 to the transmission circuit B1, and connect the transmission circuit B1 to the narrowband in-phase coupler C2; connect the amplifier circuit A2 to the comb line generator 2, connect the comb line generator 2 to the transmission circuit B2, connect the transmission circuit B2 to the narrowband in-phase coupler C2, connect the narrowband in-phase coupler C2 to the bandpass filter F1, connect the bandpass filter F1 to the extremely narrow bandpass filter F2, and connect the extremely narrow bandpass filter F2 to the constant temperature circuit T1;

[0057] Step 2: Low noise reference signal f ref The power is divided by the inverting coupler C1 to generate two equal-amplitude inverted reference signals, expressed as cosω ref t and cos(ω ref t+180°), two equal-amplitude and inverted reference signals are respectively passed through amplifier circuit A1 and amplifier circuit A2, and the amplitudes of A1 and A2 are respectively amplified, and additional phase offset is introduced.

[0058] Step 3: The input reference signals of comb generator 1 and comb generator 2 are equal in amplitude and inverted in phase, and the phase difference of the odd-order comb signals generated by comb generator 1 and comb generator 2 is (2N+1)*180°, that is, inverted; the phase difference of the even-order comb signals is 2N*180°=N*360°, that is, in phase, where N is an integer; the wide-spectrum comb signals output by comb generator 1 and comb generator 2 are respectively transmitted through transmission circuit B1 and transmission circuit B2 to coupler C2, and phase offset is introduced respectively. and The two sets of comb line signals are transmitted to the input end of coupler C2 through transmission circuits B1 and B2, with odd-order signals kept in anti-phase and even-order signals kept in phase;

[0059] Step 4: Use narrowband in-phase coupler C2 to perform power synthesis on the wide spectrum comb line. The original inverted odd-order comb line signals are vector-superimposed and canceled in C2; the original in-phase even-order comb line signals are vector-superimposed and multiplied in C2; the main signal 2Nf in the comb line signal output by C2 is refThe spurious signals on both sides are 2(N-1)f ref and 2(N+1)f ref , 2f frequency difference from the main signal ref , compared with the stray frequency difference f of a single comb line generator ref Double;

[0060] Step 5: cascade the bandpass filter F1 at the output of C2. The passband center frequency of the bandpass filter is 2Nf. ref , filter out the frequency difference 2f on both sides of the main signal ref and far-end spurious.

[0061] Example 2

[0062] Based on Example 1, the phase shift introduced by the amplifier circuit A1 and the amplifier circuit A2 is the same. The two amplifier circuits use equipment of the same model and batch, and have the same gain at the same frequency point, A1=A2.

[0063] Example 3

[0064] On the basis of Example 1, the combing line generator 1 and the combing line generator 2 use equipment of the same model and the same batch.

[0065] Example 4

[0066] Based on Example 1, the transmission circuit B1 and the transmission circuit B2 are symmetrical. For the same frequency comb point frequency, the introduced phase offset is the same.

[0067] Example 5

[0068] Based on Example 1, the center frequency of the working frequency band of the narrowband coupler C2 is the synthetic signal frequency 2Nf ref , it has suppression and reflection effects on signals outside the passband, and has no parasitic passband.

[0069] Example 6

[0070] On the basis of Example 1, the parasitic passband of the narrowband filter F1 is outside the passband of the narrowband coupler C2. The narrowband coupler C2 cooperates with the bandpass filter F1 to generate the 2(N+1)f ref It effectively suppresses other high-order comb signals and has no parasitic passband as a whole.

[0071] Example 7

[0072] On the basis of embodiment 1, the extremely narrow bandpass filter F2 is cascaded with the bandpass filter F1, and the output end is the output of the entire circuit; the extremely narrow bandpass filter F2 is used to filter out the main signal 2Nf refThe additional noise introduced by the active devices on both sides of the near end is optimized to optimize the output signal phase noise.

[0073] Example 8

[0074] Based on the first embodiment, the extremely narrow bandpass filter F2 adopts any one of a surface acoustic wave filter, a crystal filter, and a thin film bulk acoustic wave resonator filter.

[0075] Example 9

[0076] On the basis of Example 1, the constant temperature circuit T1 realizes the working temperature stability of the extremely narrow bandpass filter F2, reduces the temperature drift of the extremely narrow passband, and makes the main signal frequency 2Nf ref Both high and low temperatures are within the F2 passband frequency.

[0077] Example 10

[0078] Based on Example 1, the passband frequencies of the extremely narrow bandpass filter F2 are set at the kHz level, the 10kHz level and the 100kHz level, respectively forming effective out-of-band suppression for the 10kHz, 100kHz and 1MHz positions on both sides of the frequency-deviation main signal.

[0079] The units involved in the embodiments of the present invention may be implemented in software or hardware, and the units described may also be provided in a processor. In some cases, the names of these units do not limit the units themselves.

[0080] According to one aspect of an embodiment of the present invention, a computer program product or computer program is provided, comprising computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the methods provided in the various optional implementations described above.

[0081] As another aspect, embodiments of the present invention further provide a computer-readable medium, which may be included in the electronic device described in the above embodiments, or may exist independently and not incorporated into the electronic device. The computer-readable medium carries one or more programs, and when executed by the electronic device, the electronic device implements the methods described in the above embodiments.

[0082] The parts not involved in the present invention are the same as the existing technology or can be implemented by using the existing technology.

[0083] The above technical solution is only one embodiment of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and it is not limited to the method described in the above specific embodiment of the present invention. Therefore, the method described above is only preferred and does not have a restrictive meaning.

[0084] In addition to the above examples, those skilled in the art may obtain other embodiments based on the above disclosure or by utilizing knowledge or technology in related fields to make modifications. The features of each embodiment may be interchangeable or replaced. The modifications and changes made by those skilled in the art do not depart from the spirit and scope of the present invention and should be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for frequency synthesis of even-order signals with low phase noise and low spurious emission, characterized in that: Including steps: Step 1: Establish a low phase noise, low spurious even-order signal frequency synthesis circuit: connect the anti-phase coupler C1 to the amplifier circuit A1 and the amplifier circuit A2 respectively; connect the amplifier circuit A1 to the comb line generator 1, connect the comb line generator 1 to the transmission circuit B1, and connect the transmission circuit B1 to the narrowband in-phase coupler C2; connect the amplifier circuit A2 to the comb line generator 2, connect the comb line generator 2 to the transmission circuit B2, connect the transmission circuit B2 to the narrowband in-phase coupler C2, connect the narrowband in-phase coupler C2 to the bandpass filter F1, connect the bandpass filter F1 to the extremely narrow bandpass filter F2, and connect the extremely narrow bandpass filter F2 to the constant temperature circuit T1; Step 2: Low noise reference signal f ref The power is divided by the anti-phase coupler C1 to generate two equal-amplitude anti-phase reference signals, expressed as cosω ref t and cos(ω ref t+180°), two equal-amplitude and inverted reference signals are respectively passed through amplifier circuit A1 and amplifier circuit A2, and the amplitudes of A1 and A2 are respectively amplified, and additional phase offset is introduced. Step 3: The input reference signals of comb generator 1 and comb generator 2 are equal in amplitude and inverted in phase, and the phase difference of the odd-order comb signals generated by comb generator 1 and comb generator 2 is (2N+1)*180°, that is, inverted; the phase difference of the even-order comb signals is 2N*180°=N*360°, that is, in phase, where N is an integer; the wide-spectrum comb signals output by comb generator 1 and comb generator 2 are respectively transmitted through transmission circuit B1 and transmission circuit B2 to coupler C2, and phase offset is introduced respectively. and The two sets of comb line signals are transmitted to the input end of coupler C2 through transmission circuits B1 and B2, with odd-order signals kept in anti-phase and even-order signals kept in phase; Step 4: Use narrowband in-phase coupler C2 to perform power synthesis on the wide spectrum comb line. The original inverted odd-order comb line signals are vector-superimposed and canceled in C2; the original in-phase even-order comb line signals are vector-superimposed and multiplied in C2; the main signal 2Nf in the comb line signal output by C2 is ref The spurious signals on both sides are 2(N-1)f ref and 2(N+1)f ref , 2f frequency difference from the main signal ref , compared with the stray frequency difference f of a single comb line generator ref Double; Step 5: Cascade the bandpass filter F1 at the output of C2. The center passband frequency of the bandpass filter is 2Nf. ref , filter out the frequency difference 2f on both sides of the main signal ref and far-end spurious.

2. The low phase noise, low spurious even-order signal frequency synthesis method according to claim 1, characterized in that: The phase shift introduced by amplifier circuit A1 and amplifier circuit A2 is the same. The two amplifier circuits use equipment of the same model and batch, and have the same gain at the same frequency point, A1=A2.

3. The low phase noise, low spurious even-order signal frequency synthesis method according to claim 1, characterized in that: Comb line generator 1 and comb line generator 2 use equipment of the same model and the same batch, and do not introduce additional phase difference when generating comb line spectra for the same frequency input signal.

4. The low phase noise, low spurious even-order signal frequency synthesis method according to claim 1, characterized in that: Transmission circuit B1 and transmission circuit B2 are symmetrical. For the same frequency comb point frequency, the introduced phase offset is the same.

5. The low phase noise, low spurious even-order signal frequency synthesis method according to claim 1, characterized in that: The center frequency of the operating frequency band of the narrowband coupler C2 is the synthetic signal frequency 2Nf ref , it has suppression and reflection effects on signals outside the passband, and has no parasitic passband.

6. The low phase noise, low spurious even-order signal frequency synthesis method according to claim 1, characterized in that: The parasitic passband of the bandpass filter F1 is outside the passband of the narrowband coupler C2; the narrowband coupler C2 cooperates with the bandpass filter F1 to generate the 2(N+1)f ref It effectively suppresses other high-order comb signals and has no parasitic passband as a whole.

7. The low phase noise, low spurious even-order signal frequency synthesis method according to claim 1, characterized in that: The extremely narrow bandpass filter F2 is cascaded with the bandpass filter F1, and the output end is the output of the entire circuit; the extremely narrow bandpass filter F2 is used to filter out the main signal 2Nf ref The additional noise introduced by the active devices on both sides of the near end is optimized to optimize the output signal phase noise.

8. The low phase noise and low spurious even-order signal frequency synthesis method according to claim 1, characterized in that: The extremely narrow bandpass filter F2 is a surface acoustic wave filter, a crystal filter, or a thin film bulk acoustic wave resonator filter.

9. The low phase noise, low spurious even-order signal frequency synthesis method according to claim 1, characterized in that: The constant temperature circuit T1 realizes the working temperature stability of the extremely narrow bandpass filter F2, reduces the temperature drift of the extremely narrow passband, and makes the main signal frequency 2Nf ref Both high and low temperatures are within the F2 passband frequency.

10. The low phase noise, low spurious even-order signal frequency synthesis method according to claim 1, characterized in that: The passband frequencies of the extremely narrow bandpass filter F2 are set at the kHz level, the 10kHz level and the 100kHz level, respectively forming effective out-of-band suppression for the 10kHz, 100kHz and 1MHz positions on both sides of the frequency-deviation main signal.

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