Low phase noise, low spurious odd order signal frequency synthesis circuit and method

Abstract

This invention discloses a low-phase-noise, low-spurious odd-order signal frequency synthesis circuit and method, belonging to the field of frequency synthesis technology. It includes an anti-coupler C1, amplifier circuits A1 and A2, a comb generator (first and second), transmission circuits B1 and B2, a narrowband anti-coupler C2, a bandpass filter F1, an ultra-narrow bandpass filter F2, and a temperature-controlled circuit T1. This invention extends the frequency interval between signals, increases the frequency difference between spurious signals and the main signal, reduces the design difficulty of the filter, shrinks the implementation size, and improves the spurious suppression performance of the synthesis circuit.

Description

Technical Field

[0001] This invention relates to the field of frequency synthesis technology, and more specifically, to a low-phase-noise, low-spurious-odd-order signal frequency synthesis circuit and method. Background Technology

[0002] Frequency synthesis technology has wide applications and is an important functional component of heterodyne and superheterodyne frequency conversion systems, as well as a core unit of modern electronic information systems such as communication and jamming systems. The performance of the frequency synthesis circuit directly affects key indicators such as the system's dynamic range and sensitivity, thus impacting system performance. Therefore, lower phase noise, higher spurious suppression, and smaller implementation size remain important research directions for frequency synthesis technology.

[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 uses a phase-locked loop (PLL) consisting of a phase detector, loop filter, and voltage-controlled oscillator (VCO). Through external control, the PLL loop is locked, outputting a stable frequency. It offers advantages such as low cost and simple design, but requires control components and is limited by the characteristics of digital phase detectors, making it difficult to improve phase noise and spurious suppression, thus failing to directly meet the requirements of high-performance applications. Direct digital frequency synthesis uses a digital analog-to-digital converter (DA converter) to generate the output frequency, producing extremely fine steps at the Hz level. However, it is also limited by digital components, making it difficult to improve phase noise and spurious suppression. Furthermore, it requires external clock and control circuits, resulting in complex circuitry and high hardware footprint, making it difficult to meet the demands of high-performance and miniaturized applications. Direct frequency synthesis generates the desired frequency through addition, subtraction, multiplication, and division operations on the reference signal, without the influence of additional digital components, achieving lower phase noise. However, due to the influence of active components in the synthesis link, phase noise is degraded. In addition, all frequencies are generated analogally, producing a large amount of spurious signals that need to be filtered out separately. Spurious suppression is determined by the out-of-band rejection capability of the filter; the higher the performance requirements, the more complex the filter, increasing implementation difficulty and space requirements.

[0005] The following are existing technical solutions for low spurious and low phase noise frequency synthesis:

[0006] 1. In 2016, Zhao Yani published a paper titled "Design of a Low-Phase-Noise, Low-Spurious 650MHz Point Frequency Source." The proposed scheme uses a phase-locked loop (PLL) integer phase detector to generate a 650MHz point frequency source. The scheme is simple and easy to implement. However, this scheme cannot avoid the influence of the phase detector on the near-end phase noise of the synthesis circuit. The measured phase noise levels are -116dBc / Hz@1kHz and -114dBc / Hz@10kHz, which are significantly different from the phase noise of a direct-coupled scheme at the same frequency, and further improvement is difficult.

[0007] 2. In 2017, Zhou Min et al. published a paper titled "Design and Verification of Low-Phase-Noise Frequency Sources." The proposed scheme is a typical direct frequency synthesis circuit, using cascaded comb generators to generate the required frequency. The input reference is 100MHz, the output signal is 8GHz, and the effective harmonics are 80 times, achieved using a two-stage comb generator. Comb generator 1 generates a 1GHz intermediate frequency. With a reference input of 100MHz, spurious signals exist at 0.9GHz and 1.1GHz near 1GHz, requiring filtering by bandpass filter 1. Bandpass filter 1 provides out-of-band suppression at frequencies 1 / 10th of the main signal frequency on both sides of 1GHz, i.e., spurious signal suppression at the 1GHz point frequency. Furthermore, these spurious signals cannot be processed in subsequent stages and are coupled to the final output via comb generator 2. Under the same structure, the filter order is positively correlated with out-of-band suppression; higher out-of-band suppression requirements necessitate higher filter orders and larger sizes. Simultaneously, when the filter order exceeds 5, the increase in out-of-band suppression from simply increasing the filter order significantly decreases, making high-suppression filters difficult to design and implement. The bandpass filter 1 in the paper occupies a large volume and is difficult to optimize. In addition, although the paper uses cascaded comb lines to achieve the final frequency output and no digital devices are introduced to increase the noise floor, the circuit uses a large number of amplifiers and comb line generators, which introduces additional phase noise and degrades the circuit by 6dB, making further optimization difficult. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a low-phase-noise, low-spurious odd-order signal frequency synthesis circuit and method. This invention extends the frequency interval between signals, increases the frequency difference between spurious signals and the main signal, reduces the design difficulty of subsequent filters, reduces the implementation size, and improves the spurious suppression performance of the synthesis circuit. It utilizes a comb generator with an inverting reference input to generate a comb spectrum signal where even-order signals are in phase and odd-order signals are out of phase. Odd-order signals are synthesized and even-order signals are canceled through an inverting coupler, increasing the power of the odd-order signal by 3dB. Because the noise floor added by active devices does not overlap, the phase noise is improved by 3dB. It uses a narrow-band inverting coupler to suppress reflections outside the passband, solving the parasitic passband problem of a single narrow-band bandpass filter and simplifying the filter link design. It employs a temperature-controlled circuit to address the problem of the main signal falling into the stopband due to temperature drift in ultra-narrow-band bandpass filters at high and low temperatures, achieving full-temperature stability of the ultra-narrow-band passband filter and further optimizing the output signal phase noise.

[0009] The objective of this invention is achieved through the following solution:

[0010] A low-phase-noise, low-spurious-odd-order signal frequency synthesis circuit includes:

[0011] Anti-coupler C1, amplifier circuit A1, amplifier circuit A2, comb generator 1, comb generator 2, transmission circuit B1, transmission circuit B2, narrowband anti-coupler C2, bandpass filter F1, ultra-narrow bandpass filter F2, constant temperature circuit T1.

[0012] The anti-coupler C1 is connected to amplifier circuit A1 and amplifier circuit A2 respectively; amplifier circuit A1 is connected to comb generator one, comb generator one is connected to transmission circuit B1, transmission circuit B1 is connected to narrowband anti-coupler C2; amplifier circuit A2 is connected to comb generator two, comb generator two is connected to transmission circuit B2, transmission circuit B2 is connected to narrowband anti-coupler C2; narrowband anti-coupler C2 is connected to bandpass filter F1, bandpass filter F1 is connected to ultra-narrow bandpass filter F2, ultra-narrow bandpass filter F2 is connected to constant temperature circuit T1.

[0013] Furthermore, the extremely narrow bandpass filter F2 is implemented using a high-Q filter, which can be any one of a surface acoustic wave (SAW) filter, a crystal filter, or a thin-film bulk acoustic resonator filter.

[0014] A method for synthesizing low-phase-noise, low-spurious-odd-order signal frequencies, based on the low-phase-noise, low-spurious-odd-order signal frequency synthesis circuit described above, includes the following steps:

[0015] S1, low-noise reference signal f ref The inverting coupler C1 divides the signal into two equal-amplitude, inverting reference signals, denoted as cosω. ref t and cos(ω) ref (t+180°), the two equal-amplitude inverted reference signals are amplified by amplifier circuits A1 and A2 respectively, and an additional phase shift is introduced.

[0016] S2, the input reference signals of comb generator 1 and comb generator 2 are equal in amplitude and out of phase. The odd-order phase difference between the comb signals generated by comb generator 1 and comb generator 2 is (2N+1)*180°, i.e., out of phase; the even-order phase difference is 2(N+1)*180°=(N+1)*360°, i.e., in phase, where N is an integer. The broadband comb signals output by comb generator 1 and comb generator 2 are transmitted to coupler C2 through transmission circuit B1 and transmission circuit B2, respectively, introducing phase shifts. and Two sets of comb signals are transmitted to the input of coupler C2 via transmission circuits B1 and B2. Odd-order signals remain in phase, while even-order signals remain in phase.

[0017] S3 uses a narrowband anti-phase coupler C2 to synthesize the input comb signal. C2 introduces a 180° phase difference into each frequency point of the input signal within the operating frequency band. The original inverted odd-order comb signals are superimposed with a 180° phase difference within C2 to become in-phase, resulting in vector superposition and power multiplication. The original in-phase even-order comb signals are superimposed with a 180° phase difference within C2 to become inverted, resulting in vector superposition and cancellation. The main signal (2N+1)f in the comb signal output by C2... ref The spurious signals on both sides are (2N-1)f ref and (2N+3)f ref 2f frequency difference from the main signal ref The spurious frequency difference f relative to a single comb generator ref Double;

[0018] A bandpass filter F1 is cascaded at the output of S4 and C2. The passband frequency of the bandpass filter is (2N+1)f. ref Filter out the frequency difference 2f between the two sides of the main signal ref and remote straying.

[0019] Furthermore, amplifier circuits A1 and A2 are symmetrical, have the same electrical length, and introduce the same phase shift. Furthermore, the two amplifier circuits use the same model and batch of equipment, and have the same gain at the same frequency point, A1 = A2.

[0020] Furthermore, both comb generator 1 and comb generator 2 use the same model and batch of equipment, generating comb spectra from input signals of the same frequency without introducing additional phase differences. In this scheme, under the condition of equal amplitude and inverted phase reference input, the generated comb spectrum signals are of the same frequency and amplitude; odd-order signals have a phase difference of (2N+1)*180° and are inverted; even-order signals have a phase difference of 2(N+1)*180° and are in phase.

[0021] Furthermore, transmission circuits B1 and B2 are symmetrical and have the same electrical length. For the same comb point frequency, the introduced phase shift is the same.

[0022] Furthermore, the center frequency of the operating frequency band of the narrowband coupler C2 is the synthesized signal frequency (2N+1)f. ref The narrowband filter F1 suppresses and reflects signals outside the passband and has no parasitic passband; the parasitic passband of the narrowband filter F1 is located outside the passband of the narrowband coupler C2; the narrowband coupler C2, in conjunction with the bandpass filter F1, affects the (2N+3)f signal generated by the comb generator. ref It effectively suppresses other higher-order comb signals and has no parasitic passbands overall.

[0023] Furthermore, the extremely narrow bandpass filter F2 is cascaded with the bandpass filter F1, and the output is the output of the entire circuit; the extremely narrow bandpass filter F2 is used to filter out the main signal (2N+1)f refThe additional noise introduced by active devices on both sides near the ends is optimized to reduce the phase noise of the output signal.

[0024] Furthermore, the passband bandwidth of the ultra-narrow bandpass filter is set to the order of 10kHz, 100kHz, and MHz, which effectively suppresses phase noise at positions of 100kHz, 1MHz, and 10MHz on both sides of the frequency offset main signal, respectively.

[0025] Furthermore, the constant temperature circuit T1 is used to stabilize the operating temperature of the ultra-narrow bandpass filter F2, reduce the temperature drift of the ultra-narrow passband, and ensure that the main signal frequency (2N+1)f ref It remains within the F2 passband frequency at both high and low temperatures.

[0026] The beneficial effects of this invention include:

[0027] The present invention proposes a low-phase-noise, low-spurious odd-order signal frequency synthesis circuit and method. It uses an inverted reference signal to generate odd-order inverted and even-order in-phase combline signals, and uses an inverting coupler to achieve the synthesis and superposition of odd-order combline signals and the synthesis and cancellation of even-order combline signals. This reduces spectral spuriousness of the combline signals, expands the frequency interval between signals, reduces the design difficulty of the filter, reduces the implementation size, and improves the spurious suppression of the synthesis circuit.

[0028] The technical solution of this invention features phase coherence of the odd-order signals input to the coupler, main signal synthesis, and power superposition, resulting in a 3dB improvement. Random noise introduced by the amplifier and comb generator is uncorrelated and does not superimpose. The main signal power is increased by 3dB relative to the noise floor within a 1Hz frequency spectrum, and phase noise is optimized by 3dB.

[0029] The technical solution of this invention utilizes a narrowband coupler to reflect out-of-band signals and has no parasitic passband characteristics. Combined with a subsequent single-stage bandpass filter, it effectively suppresses near- and far-end signals of the comb spectrum, thus solving the problem of parasitic passband leakage of high-order comb spectrum signals through a single-stage narrowband filter.

[0030] The technical solution of this invention uses a constant temperature circuit T1 in conjunction with an ultra-narrow bandpass filter F2 to solve the problem of main signal suppression caused by temperature drift due to the narrow passband of the ultra-narrow bandpass filter. This achieves effective filtering of near-end additional noise of the main signal under full temperature conditions, further improving the spectral purity of the output signal.

[0031] In the technical solution of this invention embodiment, the dual comb generator, in conjunction with the anti-phase coupler, achieves even-order signal cancellation and odd-order signal superposition, thereby improving spurious frequency offset, reducing the design difficulty of spurious suppression filters, and enhancing spurious suppression.

[0032] In the technical solution of this invention embodiment, coherent signal power is synthesized, main signal power is superimposed, noise floor is not superimposed, and phase noise is optimized by 3dB.

[0033] In the technical solution of this invention embodiment, a 3dB narrowband anti-coupler is used in conjunction with a bandpass filter F1 to compensate for the parasitic passband of F1 and the problem of easy leakage of high-order signals in the comb.

[0034] In the technical solution of this invention embodiment, the ultra-narrow bandpass filter is prone to temperature drift under temperature fluctuations due to its narrow passband, causing the filter passband to deviate from the main signal. It is combined with a constant temperature circuit to achieve full-temperature stability and filter out near-end additional phase noise. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram illustrating the optimization of output signal spurious suppression in an embodiment of the present invention. Detailed Implementation

[0038] All features disclosed in all embodiments of this specification, or steps in all methods or processes implied in the disclosure, may be combined and / or extended or replaced in any way, except for mutually exclusive features and / or steps.

[0039] In view of the current state of the technology, the inventors of this invention, after creative thinking, have realized that: direct frequency synthesis technology has no added noise from digital devices and requires no control, but the following technical difficulties need to be overcome:

[0040] 1) Spurious signal suppression is difficult to improve. Direct-connection uses mixing, frequency multiplication, and frequency division to perform frequency addition, subtraction, multiplication, and division operations, but it introduces a large number of spurious signals, which need to be filtered out. The closer the spurious frequency is to the main signal, the higher the Q value of the required filter waveform coefficients needs to be. Moreover, high spurious signal suppression cannot be achieved by directly increasing the filter order. The design difficulty and implementation space of the filter increase exponentially with the increase in spurious signal suppression requirements. Secondly, in the direct-connection scheme of the comb generator, the output of the comb generator is a multiple integer multiple of the input signal, with a rich spectrum. Although the bandpass filter can extract the main signal and filter out near-end spurious signals, there is a parasitic passband at the far end. There is leakage of high-order comb signals in the parasitic passband, which needs to be processed separately, further increasing the implementation size.

[0041] 2) Additional phase noise is difficult to filter out. The use of active devices in direct frequency synthesis circuits introduces additional noise, degrading the signal by 5dB to 10dB. System applications typically focus on phase noise at frequency offsets of 10kHz and 100kHz on either side of the main signal. The higher the output main signal frequency, the smaller the relative frequency difference between the 10kHz and 100kHz offset positions relative to the main signal. If filters are used to filter this noise, an extremely narrow passband is required. At room temperature, this can be achieved using surface acoustic wave (SAW) filters, crystal filters, and thin-film bulk acoustic wave resonator (BAS) filters. However, all of these filters exhibit temperature drift. Under extremely narrow relative bandwidth conditions, ambient temperature fluctuations can 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 the application requirements.

[0042] To address the aforementioned technical problems discovered by the inventors of this invention, and to achieve higher spurious suppression and lower phase noise frequency synthesis in a smaller volume, this invention proposes a low-phase-noise, low-spurious odd-order signal frequency synthesis circuit and method. In this invention, the technical solution utilizes the characteristic of odd-order signals being out of phase and even-order signals being in phase, generated by two comb line generators, with an inverted coherent reference signal input. An inverting coupler is used to introduce another 180° phase difference, and power synthesis is performed. In-phase signals are superimposed, and inverted signals are canceled, achieving odd-order signal extraction and even-order signal suppression. This reduces spurious frequency points in the comb line spectrum by half, doubles the frequency difference between adjacent spurious points of the main signal, reduces the filter design difficulty, and decreases the implementation volume. Simultaneously, by utilizing a narrowband coupler to reflect signals outside the passband without parasitic passband characteristics, the problem of far-end parasitic passbands in single-stage bandpass filters is solved, filtering out near-end and far-end spurious signals of the main signal.

[0043] Simultaneously, the odd-order signals input to the coupler are anti-phase coherent. After superimposing the 180° phase difference introduced by the coupler, the signal vector synthesis is superimposed, increasing the power by 3dB. However, the random noise floor introduced by active devices such as the comb generator is uncorrelated and does not superimpose. The increase in power of the main signal relative to the noise floor within the 1Hz spectrum is equivalent to an increase in phase noise. Therefore, the circuit of this invention has a 3dB phase noise optimization compared to the direct frequency synthesis scheme that does not use the technology of this invention.

[0044] Furthermore, in a further inventive concept, considering the temperature drift problem of ultra-narrow bandpass filters that can be used to filter out additional noise, the technical solution of this invention adopts a constant temperature circuit to realize a temperature-stable ultra-narrow bandpass filter circuit, which reduces the temperature drift of the filter passband, filters out the additional noise introduced by active devices on both sides of the main signal, and further improves the spectral purity of the output signal.

[0045] In other embodiments, the present invention provides a low-phase-noise, low-spurious odd-order signal frequency synthesis circuit and method, wherein the circuit includes a 3dB anti-coupler C1, an amplifier circuit A1, an amplifier circuit A2, a comb generator 1, a comb generator 2, a transmission circuit B1, a transmission circuit B2, a 3dB narrowband anti-coupler C2, a bandpass filter F1, an ultra-narrow bandpass filter F2, and a temperature control circuit T1, as shown. Figure 1 As shown.

[0046] In other embodiments, C1 is a 3dB anti-coupler, and the low-noise reference signal f ref The coupler C1 divides the signal into two equal-amplitude, opposite-phase reference signals, denoted as cosω. ref t and cos(ω) ref (t+180°).

[0047] In other embodiments, the two inverted reference signals are amplified by amplifier circuits A1 and A2 respectively, and an additional phase shift is introduced. This invention employs a symmetrical design, with both amplifier circuits having the same electrical length and introducing the same phase shift. The two amplifier circuits use the same model and batch of equipment, and have the same gain at the same frequency point, A1 = A2.

[0048] In other embodiments, the input reference signals of comb generator 1 and comb generator 2 are of equal amplitude and out of phase, and comb generator 1 and comb generator 2 use the same model and batch of equipment. The odd-order phase difference of the comb signals generated by comb generator 1 and comb generator 2 is (2N+1)*180°, that is, out of phase; the even-order phase difference is 2(N+1)*180°=(N+1)*360°, that is, in phase, where N is an integer.

[0049] In other embodiments, the broadband combing signals output by combing generator 1 and combing generator 2 are transmitted to coupler C2 via transmission circuit B1 and transmission circuit B2, respectively, introducing phase shifts. and In this invention, transmission circuits B1 and B2 are symmetrical and have the same electrical length. For the same comb point frequency, the introduced phase shift is the same. Two sets of comb signals are transmitted to the input of coupler C2 via transmission circuits B1 and B2. Odd-order signals remain in phase, while even-order signals remain in phase.

[0050] In other embodiments, a 3dB narrowband anti-phase coupler C2 is used to synthesize the input comb signal. C2 introduces a 180° phase difference into each frequency point of the input signal within the operating frequency band. The original inverted odd-order comb signals are superimposed with the 180° phase difference within C2 to become in-phase, resulting in vector superposition and power multiplication; the original in-phase even-order comb signals are superimposed with the 180° phase difference within C2 to become out-of-phase, resulting in vector superposition and cancellation. The main signal (2N+1)f in the comb signal output by C2 ref The spurious signals on both sides are (2N-1)f ref and (2N+3)f ref 2f frequency difference from the main signal ref The spurious frequency difference f relative to a single comb generator ref Double.

[0051] In other embodiments, a bandpass filter F1 is cascaded at the output of C2, and the center frequency of the passband of the bandpass filter is (2N+1)f. ref Filter out the frequency difference 2f between the two sides of the main signal ref and remote straying.

[0052] In other embodiments, C2 is a narrowband coupler with a center frequency of the synthesized signal frequency (2N+1)f. ref It suppresses and reflects signals outside the passband, and has no parasitic passband. The narrowband coupler C2, in conjunction with the bandpass filter F1, controls the (2N+3)f signal generated by the comb generator. ref It effectively suppresses other higher-order comb signals and eliminates parasitic passbands.

[0053] In other implementations, the extremely narrow bandpass filter F2 is cascaded with the bandpass filter F1, and the output is the output of the entire circuit. F2 is used to filter out the main signal (2N+1)f ref The additional noise introduced by active devices on both sides near the ends is optimized to reduce the phase noise of the output signal.

[0054] In other implementations, the extremely narrow bandpass filter F2 can be implemented using high-Q filters such as surface acoustic wave (SAW) filters, crystal filters, and thin-film bulk acoustic wave resonator filters.

[0055] In other embodiments, the passband bandwidth of the ultra-narrow bandpass filter can be set to the order of 10kHz, 100kHz, and MHz, respectively, to effectively suppress phase noise at positions of 100kHz, 1MHz, and 10MHz on both sides of the frequency offset main signal.

[0056] In other embodiments, the temperature-controlled circuit T1 stabilizes the operating temperature of the ultra-narrow bandpass filter F2, reduces the temperature drift of the ultra-narrow passband, and ensures that the main signal frequency (2N+1)f ref It remains within the F2 passband frequency at both high and low temperatures.

[0057] Therefore, the circuit using the technical solution of this invention can achieve high-performance frequency synthesis with low phase noise and low spurious emissions in a relatively small volume. In actual project product development, a 1.5GHz low phase noise and low spurious emission point frequency source circuit was developed using the technical solution of this invention. The phase noise is better than -129dBc / Hz@1kHz, and the spurious emission suppression reaches -75dBc, which well meets the needs of engineering applications.

[0058] Example 1

[0059] A low-phase-noise, low-spurious-odd-order signal frequency synthesis circuit includes:

[0060] Anti-coupler C1, amplifier circuit A1, amplifier circuit A2, comb generator 1, comb generator 2, transmission circuit B1, transmission circuit B2, narrowband anti-coupler C2, bandpass filter F1, ultra-narrow bandpass filter F2, constant temperature circuit T1.

[0061] The anti-coupler C1 is connected to amplifier circuit A1 and amplifier circuit A2 respectively; amplifier circuit A1 is connected to comb generator one, comb generator one is connected to transmission circuit B1, transmission circuit B1 is connected to narrowband anti-coupler C2; amplifier circuit A2 is connected to comb generator two, comb generator two is connected to transmission circuit B2, transmission circuit B2 is connected to narrowband anti-coupler C2; narrowband anti-coupler C2 is connected to bandpass filter F1, bandpass filter F1 is connected to ultra-narrow bandpass filter F2, ultra-narrow bandpass filter F2 is connected to constant temperature circuit T1.

[0062] Example 2

[0063] Based on Example 1, the ultra-narrow bandpass filter F2 is implemented using a high-Q filter, which includes any one of surface acoustic wave (SAW) filters, crystal filters, and thin-film bulk acoustic resonator filters.

[0064] Example 3

[0065] A method for synthesizing low-phase-noise, low-spurious-odd-order signal frequencies, based on the low-phase-noise, low-spurious-odd-order signal frequency synthesis circuit as described in Example 1, includes the following steps:

[0066] S1, low-noise reference signal f ref The inverting coupler C1 divides the signal into two equal-amplitude, inverting reference signals, denoted as cosω. ref t and cos(ω) ref (t+180°), the two equal-amplitude inverted reference signals are amplified by amplifier circuits A1 and A2 respectively, and an additional phase shift is introduced.

[0067] S2, the input reference signals of comb generator 1 and comb generator 2 are equal in amplitude and out of phase. The odd-order phase difference between the comb signals generated by comb generator 1 and comb generator 2 is (2N+1)*180°, i.e., out of phase; the even-order phase difference is 2(N+1)*180°=(N+1)*360°, i.e., in phase, where N is an integer. The broadband comb signals output by comb generator 1 and comb generator 2 are transmitted to coupler C2 through transmission circuit B1 and transmission circuit B2, respectively, introducing phase shifts. and Two sets of comb signals are transmitted to the input of coupler C2 via transmission circuits B1 and B2. Odd-order signals remain in phase, while even-order signals remain in phase.

[0068] S3 uses a narrowband anti-phase coupler C2 to synthesize the input comb signal. C2 introduces a 180° phase difference into each frequency point of the input signal within the operating frequency band. The original inverted odd-order comb signals are superimposed with a 180° phase difference within C2 to become in-phase, resulting in vector superposition and power multiplication. The original in-phase even-order comb signals are superimposed with a 180° phase difference within C2 to become inverted, resulting in vector superposition and cancellation. The main signal (2N+1)f in the comb signal output by C2... ref The spurious signals on both sides are (2N-1)f ref and (2N+3)f ref 2f frequency difference from the main signal ref The spurious frequency difference f relative to a single comb generator ref Double;

[0069] A bandpass filter F1 is cascaded at the output of S4 and C2. The center frequency of the bandpass filter is (2N+1)f. ref Filter out the frequency difference 2f between the two sides of the main signal ref and remote straying.

[0070] Example 4

[0071] Based on Example 3, amplifier circuits A1 and A2 are symmetrical, have the same electrical length, and introduce the same phase shift. Furthermore, the two amplifier circuits use the same model and batch of equipment, and have the same gain at the same frequency point, A1 = A2.

[0072] Example 5

[0073] Based on Example 3, both comb generator 1 and comb generator 2 use the same model and batch of equipment. While generating comb spectra from input signals of the same frequency, no additional phase difference is introduced. In this scheme, under the condition of equal amplitude and inverted phase reference input, the generated comb spectrum signals are of the same frequency and amplitude; odd-order signals have a phase difference of (2N+1)*180° and are inverted; even-order signals have a phase difference of 2(N+1)*180° and are in phase.

[0074] Example 6

[0075] Based on Example 3, transmission circuits B1 and B2 are symmetrical and have the same electrical length. For the same comb point frequency, the introduced phase shift is the same.

[0076] Example 7

[0077] Based on Example 3, the center frequency of the operating frequency band of the narrowband coupler C2 is the synthesized signal frequency (2N+1)f. ref The narrowband filter F1 suppresses and reflects signals outside the passband and has no parasitic passband; the parasitic passband of the narrowband filter F1 is located outside the passband of the narrowband coupler C2; the narrowband coupler C2, in conjunction with the bandpass filter F1, affects the (2N+3)f signal generated by the comb generator. ref It effectively suppresses other higher-order comb signals and has no parasitic passbands overall.

[0078] Example 8

[0079] Based on Example 3, the extremely narrow bandpass filter F2 is cascaded with the bandpass filter F1, and the output is the output of the entire circuit; the extremely narrow bandpass filter F2 is used to filter out the main signal (2N+1)f ref The additional noise introduced by active devices on both sides near the ends is optimized to reduce the phase noise of the output signal.

[0080] Example 9

[0081] Based on Example 3, the passband bandwidth of the ultra-narrow bandpass filter is set to the order of 10kHz, 100kHz, and MHz, which effectively suppresses the phase noise at positions of 100kHz, 1MHz, and 10MHz on both sides of the frequency offset main signal, respectively.

[0082] Example 10

[0083] Based on Example 3, the constant temperature circuit T1 is used to stabilize the operating temperature of the ultra-narrow bandpass filter F2, reduce the temperature drift of the ultra-narrow passband, and make the main signal frequency (2N+1)f ref It remains within the F2 passband frequency at both high and low temperatures.

[0084] The units described in the embodiments of the present invention can be implemented in software or hardware, and the described units can also be located in a processor. The names of these units do not necessarily limit the specific unit itself.

[0085] According to one aspect of this application, 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 alternative implementations described above.

[0086] In another aspect, this application also provides a computer-readable medium, which may be included in the electronic device described in the above embodiments; or it may exist independently and not assembled into the electronic device. The computer-readable medium carries one or more programs, which, when executed by the electronic device, cause the electronic device to perform the methods described in the above embodiments.

[0087] All parts not covered in this invention are the same as or can be implemented using existing technologies.

[0088] The above technical solution is only one embodiment of the present invention. For those skilled in the art, based on the application methods and principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the methods described in the above specific embodiments of the present invention. Therefore, the methods described above are only preferred and are not restrictive.

[0089] In addition to the examples above, other embodiments may be obtained by those skilled in the art based on the above disclosure or by making modifications using knowledge or technology in related fields. The features of each embodiment may be interchanged or replaced. Modifications and changes made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A method for synthesizing odd-order signal frequencies with low phase noise and low spurious emissions, characterized in that, Based on a low phase noise, low spurious odd-order signal frequency synthesis circuit, the circuit includes: an anti-coupler C1, an amplifier circuit A1, an amplifier circuit A2, a comb generator I, a comb generator II, a transmission circuit B1, a transmission circuit B2, a narrowband anti-coupler C2, a bandpass filter F1, an ultra-narrow bandpass filter F2, and a constant temperature circuit T1. Anti-coupler C1 is connected to amplifier circuit A1 and amplifier circuit A2 respectively; amplifier circuit A1 is connected to comb generator one, comb generator one is connected to transmission circuit B1, transmission circuit B1 is connected to narrowband anti-coupler C2; amplifier circuit A2 is connected to comb generator two, comb generator two is connected to transmission circuit B2, transmission circuit B2 is connected to narrowband anti-coupler C2; narrowband anti-coupler C2 is connected to bandpass filter F1, bandpass filter F1 is connected to ultra-narrow bandpass filter F2, ultra-narrow bandpass filter F2 is connected to constant temperature circuit T1; including the following steps: S1, Low-noise reference signal The inverting coupler C1 divides the signal into two equal-amplitude, inverting reference signals, which are represented as follows: and The two equal-amplitude, inverted reference signals are amplified by amplifier circuits A1 and A2 respectively, and an additional phase shift is introduced. , ; S2, the input reference signals of comb generator 1 and comb generator 2 are equal in amplitude and out of phase. The odd-order phase difference between the comb signals generated by comb generator 1 and comb generator 2 is (2N+1) * 180°, i.e., out of phase; the even-order phase difference is 2(N+1) * 180° = (N+1) * 360°, i.e., in phase, where N is an integer. The broadband comb signals output by comb generator 1 and comb generator 2 are transmitted to narrowband anti-phase coupler C2 through transmission circuits B1 and B2, respectively, introducing phase shifts. and The two sets of comb signals are transmitted to the input of the narrowband anti-phase coupler C2 via transmission circuits B1 and B2. The odd-order signals remain inverted, while the even-order signals remain in phase. S3 uses a narrowband anti-phase coupler C2 to synthesize the input comb signal. C2 introduces a 180° phase difference into each frequency point of the input signal within the operating frequency band. The original inverted odd-order comb signals are superimposed with the 180° phase difference within C2 to become in-phase, resulting in vector superposition and power multiplication. The original in-phase even-order comb signals are superimposed with the 180° phase difference within C2 to become inverted, resulting in vector superposition and cancellation. The main signal in the comb signal output by C2... Spurious signals on both sides are and Frequency difference compared to the main signal The stray frequency difference relative to a single comb generator Double; S4, C2 output end cascade band-pass filter F1, band-pass filter passband center frequency is , filter out the main signal both sides of the frequency difference and far-end spur.

2. The low phase noise, low spurious odd order signal frequency synthesis method of claim 1, wherein, The extremely narrow bandpass filter F2 is implemented using a high-Q filter, which can be any one of a surface acoustic wave (SAW) filter, a crystal filter, or a thin-film bulk acoustic resonator filter.

3. The low phase noise, low spurious odd order signal frequency synthesis method of claim 1, wherein, Amplifier circuits A1 and A2 are symmetrical, have the same electrical length, and introduce the same phase shift. = Furthermore, both amplifier circuits use the same model and batch of equipment, and have the same gain at the same frequency point, so A1=A2.

4. The low phase noise, low spurious odd order signal frequency synthesis method of claim 1, wherein, Comb generator 1 and comb generator 2 use the same model and batch of equipment to generate comb spectra for input signals of the same frequency without introducing additional phase difference.

5. The low phase noise, low spurious odd order signal frequency synthesis method of claim 1, wherein, Transmission circuits B1 and B2 are symmetrical and have the same electrical length. For the same comb point frequency, the introduced phase shift is the same. = .

6. The method for synthesizing low-phase-noise, low-spurious-order odd-order signals according to claim 1, characterized in that, The narrow-band anti-phase coupler C2 has a center frequency of the operating band at the composite signal frequency There is inhibition and reflection of signals outside the passband, and there is no spurious passband. The spurious passband of the narrow-band filter F1 is located outside the passband of the narrow-band inverting coupler C2; the narrow-band inverting coupler C2 cooperates with the band-pass filter F1 to produce an effective suppression of the comb-line generator and other high-order comb-spectrum signals, and the overall spurious passband is suppressed.

7. The method for synthesizing low-phase-noise, low-spurious-order odd-order signal frequencies according to claim 1, characterized in that, The very narrow bandpass filter F2 is cascaded with the bandpass filter F1, and the output is the output of the entire circuit; the very narrow bandpass filter F2 is used to filter out the main signal. The additional noise introduced by active devices on both sides near the ends is optimized to reduce the phase noise of the output signal.

8. The low phase noise, low spurious odd order signal frequency synthesis method of claim 1, wherein, The passband bandwidth of the ultra-narrow bandpass filter is set to the order of 10kHz, 100kHz, and MHz, which effectively suppresses phase noise at positions of 100kHz, 1MHz, and 10MHz on both sides of the frequency offset main signal, respectively.

9. The method for synthesizing low-phase-noise, low-spurious-order odd-order signals according to claim 1, characterized in that, The constant temperature circuit T1 is used to realize the working temperature stability of the extremely narrow band filter F2, reduce the temperature drift of the extremely narrow band, and make the main signal frequency be within the F2 passband frequency at high and low temperatures.

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