CN114070302B - Broadband fine stepping frequency synthesis circuit and method - Google Patents

Broadband fine stepping frequency synthesis circuit and method Download PDF

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CN114070302B
CN114070302B CN202210046614.8A CN202210046614A CN114070302B CN 114070302 B CN114070302 B CN 114070302B CN 202210046614 A CN202210046614 A CN 202210046614A CN 114070302 B CN114070302 B CN 114070302B
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frequency
unit
output
broadband
switch
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CN114070302A (en
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赵翔
刘武广
陈昌锐
张文锋
周广晏
王燕
金广华
陈睿
苏梦蜀
陈远林
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CETC 29 Research Institute
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H03L7/083—Details of the phase-locked loop the reference signal being additionally directly applied to the generator
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H03L7/085—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H03L7/085—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal
    • H03L7/093—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal using special filtering or amplification characteristics in the loop
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H03L7/099—Details of the phase-locked loop concerning mainly the controlled oscillator of the loop

Abstract

The invention discloses a broadband fine stepping frequency synthesis circuit and a method, which relate to the technical field of frequency synthesis and comprise a reference unit, an intermediate frequency unit, a local oscillator unit and a spread spectrum unit. The reference unit generates a low-noise reference signal, and the output end of the reference unit is connected with the signal input end of the intermediate frequency unit and the signal input end of the local oscillator unit. The intermediate frequency unit generates a fine stepping broadband intermediate frequency signal, and the output end of the intermediate frequency unit is connected with the signal input end of the spread spectrum unit. The local oscillation unit generates a low-phase-noise local oscillation signal, and the output end of the local oscillation unit is connected with the signal input end of the spread spectrum unit. The local oscillation signal and the intermediate frequency signal are mixed in the frequency spreading unit, and the output of the frequency spreading unit is the output of the frequency synthesis circuit. The invention adopts comb line cascade to directly realize low phase noise local oscillation; a DDS + phase-locked loop is adopted to realize fine stepping broadband intermediate frequency; the working bandwidth is efficiently expanded through means of mixing frequency shifting, interpolation filling, frequency band splicing and the like, and octave-spanning broadband fine stepping frequency synthesis is realized.

Description

Broadband fine stepping frequency synthesis circuit and method
Technical Field
The present invention relates to the field of frequency synthesis technologies, and in particular, to a wideband fine-step frequency synthesis circuit and method.
Background
The frequency synthesis technology is widely applied, is an important functional component of heterodyne and superheterodyne frequency conversion systems, and is a core unit of modern electronic information systems such as communication, interference and the like. The development of modern electronic information technology puts higher and more comprehensive requirements on the performance index of a frequency source, and a broadband and fine-stepping frequency synthesis technology becomes a main research direction and development trend.
The frequency synthesis technology includes a phase-locked loop frequency synthesis technology, a direct digital frequency synthesis technology (DDS), and a direct frequency synthesis technology.
Phase-locked loops are the most widely used frequency synthesis method, and are rapidly developed along with the updating of digital devices. The typical scheme adopts a phase discriminator, a loop filter and a voltage-controlled oscillator to form a phase-locked loop and generate a phase-locked baseband. And then spread the spectrum by frequency multiplication or frequency division. The phase-locked loop is simple in technical scheme and easy to realize broadband application, but is limited by the characteristics of digital devices, frequency stepping and stray suppression are difficult to take into account, and phase noise is difficult to promote.
The direct digital frequency synthesis can realize the output of extremely fine stepping frequency, but is limited by the highest clock frequency of the device, low output frequency and narrow bandwidth, and is difficult to satisfy the broadband application.
The direct frequency synthesis generates the required frequency through addition, subtraction, multiplication and division operation on the reference signal, has no noise of an additional digital device, and has the characteristic of low phase noise. However, all frequency points are generated by an analog mode, the synthesis efficiency is low, the hardware occupation is multiplied along with the increase of the number of the frequency points, and the requirements of broadband and fine stepping are difficult to be considered.
The existing wideband frequency synthesis circuit has been reported as follows:
in 1.2016, Roming et al published a paper "a design implementation of a small millimeter wave broadband frequency source". The phase discriminator is matched with the broadband VCO to achieve the 11 GHz-20 GHz phase-locked loop circuit, the frequency-doubled spread spectrum is used for reaching 22 GHz-40 GHz, and the phase discriminator has the advantages of being simple in scheme, easy to achieve, wide in coverage frequency band and the like. But the scheme can not process decimal frequency division stray introduced by decimal phase discrimination of the phase-locked loop, and the stray is restrained by 60dBc under the frequency stepping of 25 MHz. While the spurious suppression index is guaranteed, the frequency resolution is difficult to further improve. In addition, the phase noise is difficult to improve due to the phase detector noise floor.
In 2.2019, Sunkco et al published a paper "wideband fine step agile frequency synthesizer". In the scheme, DDS is adopted to generate fine step reference, and 5 GHz-10 GHz baseband signals are realized through phase locking. And respectively carrying out frequency division and frequency multiplication on the baseband signals through switch gating, and expanding the frequency spectrum to 2 GHz-18 GHz. The scheme has the characteristic of broadband fine stepping, but the phase noise is determined by the noise floor of the phase discriminator in the phase-locked loop and is difficult to promote.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a broadband fine stepping frequency synthesis circuit and a broadband fine stepping frequency synthesis method, gives consideration to the index requirements of broadband fine stepping and low phase noise, innovatively combines the three technical advantages of a phase locking technology, a DDS (direct digital synthesis) technology and a direct frequency synthesis technology, and adopts comb line cascade to directly realize low phase noise local oscillation; a DDS + phase-locked loop is adopted to realize fine step intermediate frequency with the resolution up to 1 Hz; the high-efficiency spread spectrum is filled through frequency mixing shifting and interpolation, a broadband fine stepping frequency synthesis circuit with multiple octaves and frequency stepping reaching 1Hz is realized, and the low-phase noise and the like are achieved.
The purpose of the invention is realized by the following scheme:
a broadband fine stepping frequency synthesis circuit comprises a reference unit, an intermediate frequency unit, a local oscillator unit and a spread spectrum unit, wherein a low-noise reference signal generated by the reference unit is output to the intermediate frequency unit and the local oscillator unit, a fine stepping intermediate frequency signal is generated in the intermediate frequency unit, and a low-phase-noise local oscillator signal is generated in the local oscillator unit; the input end of the spread spectrum unit is connected with the output of the local oscillation unit and the output of the intermediate frequency unit, and the output end of the spread spectrum unit is the output of the frequency synthesis circuit.
Further, the reference unit comprises a first comb spectrum generator, a power divider and a filter
Figure 180055DEST_PATH_IMAGE001
Filter and method for manufacturing the same
Figure 918204DEST_PATH_IMAGE002
(ii) a The first comb spectrum generator inputs a low-phase noise reference signal provided by a crystal oscillator
Figure 562812DEST_PATH_IMAGE003
Produced by stepping into
Figure 222464DEST_PATH_IMAGE003
The low additional noise broadband comb spectrum signal passes through the filter after being divided into two parts
Figure 977930DEST_PATH_IMAGE001
Filter and method for manufacturing the same
Figure 101744DEST_PATH_IMAGE002
Extracting a first low noise reference signal
Figure 917253DEST_PATH_IMAGE004
A second low noise reference signal
Figure 595359DEST_PATH_IMAGE005
。
Further, the intermediate frequency unit comprises a DDS, a phase discriminator, a loop filter, a voltage-controlled oscillator and a directional coupler; first low noise reference signal
Figure 655981DEST_PATH_IMAGE004
Inputting a DDS, and selecting a DDS low-spurious performance section as the input of a phase discriminator; the phase discriminator, loop filter, voltage-controlled oscillator and directional coupler constitute phase-locked loop, and the output signal generated by the voltage-controlled oscillator
Figure 368722DEST_PATH_IMAGE006
The ultra-fine stepping signal generated by the DDS and the pre-frequency division in the phase discriminator
Figure 558395DEST_PATH_IMAGE007
Real-time phase comparison, control of pressure controlAn oscillator output frequency; the DDS and the phase-locked loop are adjusted in a matching way to generate low-stray and fine-stepping broadband intermediate-frequency signals, and the intermediate-frequency coverage frequency band is
Figure 989377DEST_PATH_IMAGE008
。
Furthermore, the local oscillator unit comprises a second comb spectrum generator, a first switch, a second switch and a band-pass filter
Figure 86646DEST_PATH_IMAGE009
Bandpass filter
Figure 653893DEST_PATH_IMAGE010
Bandpass filter
Figure 811205DEST_PATH_IMAGE011
The local oscillation adjusting circuit; a second low-noise reference signal generated by the reference unit
Figure 729482DEST_PATH_IMAGE012
A frequency interval of
Figure 630442DEST_PATH_IMAGE012
The broadband comb spectrum signal of (1); the first switch and the second switch are single-pole three-throw switches, and the comb spectrum signal is gated by selecting one from three; band-pass filter
Figure 816311DEST_PATH_IMAGE009
Bandpass filter
Figure 144524DEST_PATH_IMAGE010
Bandpass filter
Figure 487781DEST_PATH_IMAGE011
The pass bands are respectively
Figure 926852DEST_PATH_IMAGE013
Dot frequency and for off-center frequencies
Figure 468692DEST_PATH_IMAGE014
And the far-end comb spectrum signal forms effective suppression; the frequency difference of adjacent local oscillation frequency points is the same
Figure 967806DEST_PATH_IMAGE015
(ii) a The output end of the second switch is cascaded with the local oscillator adjusting circuit to amplify the gated dot-frequency local oscillator, so that the signal power is enough to excite the rear-stage frequency mixer.
Further, the frequency spreading unit comprises a mixer, a third switch, a fourth switch and a band-pass filter
Figure 595097DEST_PATH_IMAGE016
To band pass filter
Figure 103439DEST_PATH_IMAGE017
(ii) a The input end of the frequency mixer is connected with the output ends of the intermediate frequency unit and the local oscillator unit, the output end of the frequency mixer is connected with a third switch, and the third switch is connected with a band-pass filter
Figure 765364DEST_PATH_IMAGE016
To band pass filter
Figure 936845DEST_PATH_IMAGE017
Connected, band-pass filter
Figure 989114DEST_PATH_IMAGE016
To band pass filter
Figure 35568DEST_PATH_IMAGE017
Are connected to the fourth switch.
A method based on the wideband fine step frequency synthesis circuit as described in any one of the above, comprising the following steps in a spreading unit:
s1, carrying out frequency mixing and carrying out local oscillation frequency mixing and carrying out broadband intermediate frequency;
s2, interpolation filling, namely, the interpolation filling is carried out on adjacent local oscillators by using the broadband intermediate frequency in the step S1, and adjacent frequency bands output by frequency mixing are effectively spliced:
Figure 552000DEST_PATH_IMAGE018
；
Figure 392917DEST_PATH_IMAGE019
；
s3, mixing frequency in time-sharing mode, and carrying out local oscillation on multiple points
Figure 729220DEST_PATH_IMAGE020
And (3) time-sharing mixing with broadband intermediate frequency, and respectively generating:
Figure 579365DEST_PATH_IMAGE021
respectively, the up-conversion is generated:
Figure 950303DEST_PATH_IMAGE022
six sections of signals; the third switch and the fourth switch are both single-pole six-throw switches, so that six-way gating is realized; six-way passage respectively matched with band-pass filter
Figure 962121DEST_PATH_IMAGE016
To band pass filter
Figure 549835DEST_PATH_IMAGE017
Local oscillator leakage and high-order intermodulation stray in six-section mixing output are filtered;
s4, splicing frequency bands, namely, effectively splicing the three output frequency bands generated by down-conversion and the three output frequency bands generated by up-conversion in the step S3:
Figure 672512DEST_PATH_IMAGE023
；
s5, outputting, overlapping the six signals of the mixing output, cascade matching, covering
Figure 366799DEST_PATH_IMAGE024
And (4) broadband output.
The invention has the beneficial effects that:
the invention adopts the cascade of comb spectrum generators, efficiently expands the reference frequency, generates high-frequency and large-step comb spectrum signals and realizes the multiplexing of low-phase noise point frequency generation units. The DDS is used as a reference and is matched with a phase discriminator to realize digital phase locking, so that the problems of low output frequency and narrow bandwidth caused by the fact that a single DDS is limited by a device clock are solved; meanwhile, the problem that a single phase-locked loop is limited by a phase discriminator and high stray rejection and fine stepping frequency output are difficult to be considered at the same time is solved; and the fine stepping broadband intermediate frequency with the resolution reaching Hz level is realized. The local oscillation signal directly generated by the comb spectrum generator is mixed and shifted to the intermediate frequency, so that the output frequency is improved, and the low phase noise characteristic is considered; intermediate frequency signals realized by the DDS + phase-locked loop are filled in interpolation of adjacent local oscillators, effective coverage of output signals is guaranteed, and fine stepping characteristics are considered. By optimizing the frequency mixing scheme, the local oscillator and the intermediate frequency signals are multiplexed, the output frequency band cascade splicing is realized, and the broadband spectrum required to be output is efficiently covered. The invention combines the advantages of DDS, phase-locked loop and direct frequency synthesis, effectively improves output frequency, expands working bandwidth, reduces frequency step, and has the characteristic of low phase noise.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic block diagram of a circuit according to an embodiment of the present invention.
Detailed Description
All features disclosed in all embodiments in this specification, or all methods or process steps implicitly disclosed, may be combined and/or expanded, or substituted, in any way, except for mutually exclusive features and/or steps.
The drawings of embodiments of the invention include figure 1. The technical concept, operation principle, efficacy and operation of the present invention will be further described in detail with reference to fig. 1.
The technical problems solved by the invention are as follows: in order to solve the defects of the prior art in the background and consider the index requirements of broadband fine stepping and low phase noise, the invention provides a broadband fine stepping frequency synthesis scheme, which comprises a circuit and a method. The scheme innovatively combines the advantages of three technologies, namely a phase locking technology, a DDS technology and a direct frequency synthesis technology. Adopting comb line cascade to directly realize low phase noise local oscillation; a DDS + phase-locked loop is adopted to realize fine step intermediate frequency with the resolution up to 1 Hz; the broadband fine stepping frequency synthesis circuit realizes multi-octave and frequency stepping up to 1Hz by filling high-efficiency spread spectrum through frequency mixing shifting and interpolation, and has the advantage of low phase noise.
The invention provides a broadband fine stepping frequency synthesis circuit, comprising: a reference unit, an intermediate frequency unit, a local oscillator unit and a spread spectrum unit, as shown in fig. 1.
The reference cell includes: comb spectrum generator 1, power divider and filter
Figure 549518DEST_PATH_IMAGE001
Filter and method for manufacturing the same
Figure 860414DEST_PATH_IMAGE002
. The comb spectrum generator 1 inputs a low-phase noise reference signal provided by a crystal oscillator
Figure 786782DEST_PATH_IMAGE003
Produced by stepping into
Figure 397891DEST_PATH_IMAGE003
Low additive noise broadband comb spectrum signal. The comb spectrum signal passes through the filter after being divided into two parts
Figure 751512DEST_PATH_IMAGE001
Filter and method for manufacturing the same
Figure 549704DEST_PATH_IMAGE002
Extracting a low noise reference signal
Figure 781228DEST_PATH_IMAGE004
、
Figure 981265DEST_PATH_IMAGE005
。
The intermediate frequency unit includes: DDS, a phase discriminator, a loop filter, a voltage-controlled oscillator and a directional coupler. Low noise reference signal
Figure 709049DEST_PATH_IMAGE004
And inputting a DDS, and selecting a DDS low-spurious performance section as the input of the phase discriminator. The phase discriminator, loop filter, voltage-controlled oscillator and directional coupler constitute phase-locked loop, and the output signal generated by the voltage-controlled oscillator
Figure 994537DEST_PATH_IMAGE006
The ultra-fine stepping signal generated by the DDS and the pre-frequency division in the phase discriminator
Figure 528287DEST_PATH_IMAGE007
And comparing the phase in real time and controlling the output frequency of the voltage-controlled oscillator. The DDS and the phase-locked loop are adjusted in a matching way to generate a low-stray and step-by-step broadband intermediate frequency signal with the frequency range of 1Hz
Figure 848410DEST_PATH_IMAGE008
。
The local oscillation unit includes: comb spectrum generator 2, switch 1, switch 2, band-pass filter
Figure 543833DEST_PATH_IMAGE009
Bandpass filter
Figure 316617DEST_PATH_IMAGE010
Bandpass filter
Figure 388478DEST_PATH_IMAGE011
And the local oscillation adjusting circuit. Low phase noise dot frequency produced by reference cell
Figure 500791DEST_PATH_IMAGE012
The frequency interval generated by the comb spectrum generator 2 is
Figure 131230DEST_PATH_IMAGE005
The broadband comb spectrum signal of (1). The switch 1 and the switch 2 are single-pole 3-throw switches, and 3-to-1 gating is carried out on the comb spectrum signals. Band-pass filter
Figure 125731DEST_PATH_IMAGE009
Bandpass filter
Figure 266862DEST_PATH_IMAGE010
Bandpass filter
Figure 30419DEST_PATH_IMAGE011
The pass bands are respectively
Figure 333224DEST_PATH_IMAGE013
Dot frequency and for off-center frequencies
Figure 18283DEST_PATH_IMAGE014
And the far-end comb spectrum signal forms effective suppression. The frequency difference of adjacent local oscillation frequency points is the same
Figure 228685DEST_PATH_IMAGE015
. The output end of the switch 2 is cascaded with a local oscillator adjusting circuit to amplify the gated dot-frequency local oscillator, so that the signal power is enough to excite the rear-stage frequency mixer.
The spread spectrum unit includes: mixer, switch 3, switch 4, band-pass filter
Figure 315590DEST_PATH_IMAGE016
To band pass filter
Figure 789296DEST_PATH_IMAGE017
(ii) a The input end of the frequency mixer is connected with the output ends of the intermediate frequency unit and the local oscillator unit, the output end of the frequency mixer is connected with a switch 3, and the switch 3 is connected with a band-pass filter
Figure 525433DEST_PATH_IMAGE016
To band pass filter
Figure 742788DEST_PATH_IMAGE017
Connected, band-pass filter
Figure 480937DEST_PATH_IMAGE016
To band pass filter
Figure 125545DEST_PATH_IMAGE017
Is connected to the switch 4. The output of the spread spectrum unit is the output of the frequency synthesis circuit.
1. The local oscillation mixing shifts the broadband intermediate frequency, and the mixing output signal is stepped, namely the intermediate frequency signal is stepped, so that the frequency precision reaches 1 Hz.
2. And (5) interpolation filling of the broadband intermediate frequency to adjacent local oscillators. The adjacent frequency bands of the mixing output are effectively spliced, frequency points are not missed, and the intermediate frequency bandwidth is not less than the adjacent local oscillation frequency difference:
Figure 581934DEST_PATH_IMAGE018
；
Figure 540663DEST_PATH_IMAGE019
；
3. multi-point local oscillator
Figure 398897DEST_PATH_IMAGE020
And (3) time-sharing mixing with broadband intermediate frequency, and respectively generating:
Figure 745565DEST_PATH_IMAGE025
respectively, the up-conversion is generated:
Figure 187785DEST_PATH_IMAGE026
the total number of the signals is 6. The switch 3 and the switch 4 are single-pole six-throw switches, and six-way gating is achieved. Six-way passage respectively matched with band-pass filter
Figure 746943DEST_PATH_IMAGE016
To band pass filter
Figure 194105DEST_PATH_IMAGE017
And filtering out local oscillator leakage and high-order intermodulation stray in the six-section mixing output.
4. The three output frequency bands generated by the down-conversion and the three output frequency bands generated by the up-conversion are effectively spliced, and no missing frequency points exist. The highest frequency generated by the down-conversion is not lower than the lowest frequency generated by the up-conversion:
Figure 180515DEST_PATH_IMAGE027
i.e. by
Figure 611497DEST_PATH_IMAGE028
。
5. Six-segment signals output by mixing frequency are overlapped, cascaded and covered
Figure 866023DEST_PATH_IMAGE029
And (4) broadband output.
Example 1: as shown in fig. 1, a broadband fine-step frequency synthesis circuit includes a reference unit, an intermediate frequency unit, a local oscillator unit, and a spread spectrum unit, where the reference unit generates a low-noise reference signal and inputs the low-noise reference signal to the intermediate frequency unit and the local oscillator unit, the intermediate frequency unit generates a broadband intermediate frequency signal, the local oscillator unit outputs a low-phase-noise local oscillator signal, and an input end of the spread spectrum unit is connected to the local oscillator unit output and the intermediate frequency unit output.
In the embodiment, comb line cascade is adopted to directly realize low-phase-noise local oscillation; a DDS + phase-locked loop is adopted to realize fine stepping broadband intermediate frequency; the working bandwidth is efficiently expanded through means of mixing frequency shifting, interpolation filling, frequency band splicing and the like, the octave-crossing broadband fine stepping frequency synthesis is realized, and the method has the advantage of low phase noise.
Example 2: on the basis of the embodiment 1, the reference unit comprises a first comb spectrum generator, a power divider and a filter
Figure 433270DEST_PATH_IMAGE001
Filter and method for manufacturing the same
Figure 856161DEST_PATH_IMAGE002
(ii) a The first comb spectrum generator inputs a low-phase noise reference signal provided by a crystal oscillator
Figure 508859DEST_PATH_IMAGE003
Produced by stepping into
Figure 409819DEST_PATH_IMAGE003
The low additional noise broadband comb spectrum signal passes through the filter after being divided into two parts
Figure 300415DEST_PATH_IMAGE001
Filter and method for manufacturing the same
Figure 628628DEST_PATH_IMAGE002
Extracting a first low noise reference signal
Figure 267158DEST_PATH_IMAGE004
A second low noise reference signal
Figure 971808DEST_PATH_IMAGE005
。
Example 3: on the basis of the embodiment 1, the intermediate frequency unit comprises a DDS, a phase discriminator, a loop filter, a voltage-controlled oscillator and a directional coupler; first low noise reference signal
Figure 513648DEST_PATH_IMAGE004
Inputting a DDS, and selecting a DDS low-spurious performance section as the input of a phase discriminator; the phase discriminator, loop filter, voltage-controlled oscillator and directional coupler constitute phase-locked loop, and the output signal generated by the voltage-controlled oscillator
Figure 12763DEST_PATH_IMAGE006
The ultra-fine stepping signal generated by the DDS and the pre-frequency division in the phase discriminator
Figure 640053DEST_PATH_IMAGE007
Comparing the phase in real time, and controlling the output frequency of the voltage-controlled oscillator; the DDS and the phase-locked loop are adjusted in a matching way to generate low-stray and fine-stepping broadband intermediate-frequency signals, and the intermediate-frequency coverage frequency band is
Figure 86078DEST_PATH_IMAGE008
。
Example 4: on the basis of embodiment 1, the local oscillator unit includes a second comb spectrum generator, a first switch, a second switch, and a band-pass filter
Figure 482424DEST_PATH_IMAGE009
Bandpass filter
Figure 152440DEST_PATH_IMAGE010
Bandpass filter
Figure 267026DEST_PATH_IMAGE011
The local oscillation adjusting circuit; a second low-noise reference signal generated by the reference unit
Figure 80524DEST_PATH_IMAGE012
A frequency interval of
Figure 331377DEST_PATH_IMAGE012
The broadband comb spectrum signal of (1); the first switch and the second switch are single-pole three-throw switches, and the comb spectrum signal is gated by selecting one from three; band-pass filter
Figure 172294DEST_PATH_IMAGE009
Bandpass filter
Figure 774176DEST_PATH_IMAGE010
Bandpass filter
Figure 358742DEST_PATH_IMAGE011
The pass bands are respectively
Figure 932942DEST_PATH_IMAGE013
Dot frequency and for off-center frequencies
Figure 944761DEST_PATH_IMAGE014
And the far-end comb spectrum signal forms effective suppression; the frequency difference of adjacent local oscillation frequency points is the same
Figure 33939DEST_PATH_IMAGE015
(ii) a The output end of the second switch is cascaded with the local oscillator adjusting circuit to amplify the gated dot-frequency local oscillator, so that the signal power is enough to excite the rear-stage frequency mixer.
Example 5: on the basis of the embodiment 1, the frequency spreading unit comprises a mixer, a third switch, a fourth switch and a band-pass filter
Figure 422195DEST_PATH_IMAGE016
To band pass filter
Figure 904034DEST_PATH_IMAGE017
(ii) a The input end of the frequency mixer is connected with the output ends of the intermediate frequency unit and the local oscillator unit, the output end of the frequency mixer is connected with a third switch, and the third switch is connected with a band-pass filter
Figure 352333DEST_PATH_IMAGE016
To band pass filter
Figure 928808DEST_PATH_IMAGE017
Connected, band-pass filter
Figure 855175DEST_PATH_IMAGE016
To band pass filter
Figure 403968DEST_PATH_IMAGE017
Are connected to the fourth switch.
Example 6: on the basis of any of the above embodiments, a method for wideband fine step frequency synthesis circuit includes the following steps in a spreading unit:
the spread spectrum unit comprises the following steps:
s1, carrying out frequency mixing and carrying out local oscillation frequency mixing and carrying out broadband intermediate frequency;
s2, interpolation filling, namely, the interpolation filling is carried out on adjacent local oscillators by using the broadband intermediate frequency in the step S1, and adjacent frequency bands output by frequency mixing are effectively spliced:
Figure 757589DEST_PATH_IMAGE018
；
Figure 555781DEST_PATH_IMAGE019
；
s3, mixing frequency in time-sharing mode, and carrying out local oscillation on multiple points
Figure 285840DEST_PATH_IMAGE020
And (3) time-sharing mixing with broadband intermediate frequency, and respectively generating:
Figure 485877DEST_PATH_IMAGE030
respectively, the up-conversion is generated:
Figure 511864DEST_PATH_IMAGE032
six sections of signals; the third switch and the fourth switch are both single-pole six-throw switches, so that six-way gating is realized; six-way passage respectively matched with band-pass filter
Figure 62931DEST_PATH_IMAGE016
To band pass filter
Figure 331101DEST_PATH_IMAGE017
Local oscillator leakage and high-order intermodulation stray in six-section mixing output are filtered;
s4, splicing frequency bands, namely, effectively splicing the three output frequency bands generated by down-conversion and the three output frequency bands generated by up-conversion in the step S3:
Figure 385645DEST_PATH_IMAGE023
；
s5, outputting, overlapping the six signals of the mixing output, cascade matching, covering
Figure 346648DEST_PATH_IMAGE034
And (4) broadband output.
In the development and development of project products, the method is adopted to develop a broadband fine stepping frequency synthesis circuit with the frequency of 8 GHz-32 GHz and 1Hz stepping, and the engineering application requirements are well met.
The parts not involved in the present invention are the same as or can be implemented using the prior art.
The above-described embodiment is only one embodiment of the present invention, and it will be apparent to those skilled in the art that various modifications and variations can be easily made based on the application and principle of the present invention disclosed in the present application, and the present invention is not limited to the method described in the above-described embodiment of the present invention, so that the above-described embodiment is only preferred, and not restrictive.
Other embodiments than the above examples may be devised by those skilled in the art based on the foregoing disclosure, or by adapting and using knowledge or techniques of the relevant art, and features of various embodiments may be interchanged or substituted and such modifications and variations that may be made by those skilled in the art without departing from the spirit and scope of the present invention are intended to be within the scope of the following claims.

Claims (5)

1. A broadband fine step frequency synthesis circuit is characterized by comprising a reference unit, an intermediate frequency unit, a local oscillator unit and a spread spectrum unit, wherein a low-noise reference signal generated by the reference unit is output to the intermediate frequency unit and the local oscillator unit, a fine step intermediate frequency signal is generated in the intermediate frequency unit, and a low-phase-noise local oscillator signal is generated in the local oscillator unit; the input end of the spread spectrum unit is connected with the output of the local oscillation unit and the output of the intermediate frequency unit, and the output end of the spread spectrum unit is the output of the frequency synthesis circuit; the frequency spreading unit comprises a mixer, a third switch, a fourth switch and a band-pass filter
Figure 867520DEST_PATH_IMAGE001
To band pass filter
Figure 170325DEST_PATH_IMAGE002
(ii) a The input end of the frequency mixer is connected with the output ends of the intermediate frequency unit and the local oscillator unit, the output end of the frequency mixer is connected with a third switch, and the third switch is connected with a band-pass filter
Figure 527488DEST_PATH_IMAGE001
To band pass filter
Figure 941152DEST_PATH_IMAGE002
Connected, band-pass filter
Figure 700161DEST_PATH_IMAGE001
To band pass filter
Figure 173867DEST_PATH_IMAGE002
Are connected to the fourth switch.
2. The wideband fine step frequency synthesizer circuit of claim 1, wherein the reference cell comprises a first comb spectrum generator, a power divider, a filter
Figure 516862DEST_PATH_IMAGE003
Filter and method for manufacturing the same
Figure 734216DEST_PATH_IMAGE004
(ii) a The first comb spectrum generator inputs a low-phase noise reference signal provided by a crystal oscillator
Figure 613311DEST_PATH_IMAGE005
Produced by stepping into
Figure 257919DEST_PATH_IMAGE005
The low additional noise broadband comb spectrum signal is divided after the second power divisionNon-passing filter
Figure 589674DEST_PATH_IMAGE003
Filter and method for manufacturing the same
Figure 345140DEST_PATH_IMAGE004
Extracting a first low noise reference signal
Figure 141058DEST_PATH_IMAGE006
A second low noise reference signal
Figure 831934DEST_PATH_IMAGE007
。
3. The wideband fine step frequency synthesis circuit according to claim 2, wherein the intermediate frequency unit comprises a DDS, a phase detector, a loop filter, a voltage controlled oscillator, a directional coupler; first low noise reference signal
Figure 775619DEST_PATH_IMAGE006
Inputting a DDS, and selecting a DDS low-spurious performance section as the input of a phase discriminator; the phase discriminator, loop filter, voltage-controlled oscillator and directional coupler constitute phase-locked loop, and the output signal generated by the voltage-controlled oscillator
Figure 711607DEST_PATH_IMAGE008
The ultra-fine stepping signal generated by the DDS and the pre-frequency division in the phase discriminator
Figure 424348DEST_PATH_IMAGE009
Comparing the phase in real time, and controlling the output frequency of the voltage-controlled oscillator; the DDS and the phase-locked loop are adjusted in a matching way to generate low-stray and fine-stepping broadband intermediate-frequency signals, and the intermediate-frequency coverage frequency band is
Figure 20546DEST_PATH_IMAGE010
。
4. The wideband fine step frequency synthesizer circuit of claim 1, wherein the local oscillator unit comprises a second comb spectrum generator, a first switch, a second switch, a band pass filter
Figure 451527DEST_PATH_IMAGE011
Bandpass filter
Figure 424162DEST_PATH_IMAGE012
Bandpass filter
Figure 522568DEST_PATH_IMAGE013
The local oscillation adjusting circuit; a second low-noise reference signal generated by the reference unit
Figure 24088DEST_PATH_IMAGE014
A frequency interval of
Figure 207945DEST_PATH_IMAGE014
The broadband comb spectrum signal of (1); the first switch and the second switch are single-pole three-throw switches, and the comb spectrum signal is gated by selecting one from three; band-pass filter
Figure 482806DEST_PATH_IMAGE011
Bandpass filter
Figure 904560DEST_PATH_IMAGE012
Bandpass filter
Figure 108139DEST_PATH_IMAGE013
The pass bands are respectively
Figure 248134DEST_PATH_IMAGE015
Dot frequency and for off-center frequencies
Figure 156047DEST_PATH_IMAGE016
And far-end comb spectrum signalEffective inhibition is formed; the frequency difference of adjacent local oscillation frequency points is the same
Figure 573253DEST_PATH_IMAGE017
(ii) a The output end of the second switch is cascaded with the local oscillator adjusting circuit to amplify the gated dot-frequency local oscillator, so that the signal power is enough to excite the rear-stage frequency mixer.
5. A method for a wideband fine step frequency synthesis circuit according to any of claims 1 to 4, wherein the spreading unit comprises the steps of:
s1, carrying out frequency mixing and carrying out local oscillation frequency mixing and carrying out broadband intermediate frequency;
s2, interpolation filling, namely, the interpolation filling is carried out on adjacent local oscillators by using the broadband intermediate frequency in the step S1, and adjacent frequency bands output by frequency mixing are effectively spliced:
Figure 72367DEST_PATH_IMAGE018
；
Figure 575024DEST_PATH_IMAGE019
；
s3, mixing frequency in time-sharing mode, and carrying out local oscillation on multiple points
Figure 83366DEST_PATH_IMAGE020
And (3) time-sharing mixing with broadband intermediate frequency, and respectively generating:
Figure 590964DEST_PATH_IMAGE021
respectively, the up-conversion is generated:
Figure 526559DEST_PATH_IMAGE022
six sections of signals; the third switch and the fourth switch are both single-pole six-throw switches, so that six-way gating is realized; six-way channels are respectively matchedCombined band-pass filter
Figure 516511DEST_PATH_IMAGE001
To band pass filter
Figure 297386DEST_PATH_IMAGE002
Local oscillator leakage and high-order intermodulation stray in six-section mixing output are filtered;
s4, splicing frequency bands, namely, effectively splicing the three output frequency bands generated by down-conversion and the three output frequency bands generated by up-conversion in the step S3:
Figure 689184DEST_PATH_IMAGE023
；
s5, outputting, overlapping the six signals of the mixing output, cascade matching, covering
Figure 530101DEST_PATH_IMAGE024
And (4) broadband output.
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