阅读说明：本技术 一种通用化的频率合成器及合成方法 (Universal frequency synthesizer and synthesis method ) 是由 杜珂 朱红辉 于 2021-08-11 设计创作，主要内容包括：本发明公开了一种通用化的频率合成器及合成方法,所述频率合成器包括晶振,还包括依次相连的梳状谱电路、可变参考环、分频器Ⅰ和锁相环,所述锁相环包括依次环状相连的鉴相器Ⅱ、滤波器Ⅴ、宽带VCO和分频器Ⅱ,所述可变参考环包括依次相连的功分器Ⅰ、滤波器Ⅰ、DDS电路、鉴相器Ⅰ、滤波器Ⅲ、CRO振荡器和功分器Ⅱ,所述功分器Ⅰ还依次连接有滤波器Ⅱ、混频器、以及与鉴相器Ⅰ相连的滤波器Ⅳ,所述功分器Ⅱ还分别连接于混频器和分频器Ⅰ,所述混频器与功分器Ⅱ之间连接有放大器,所述分频器Ⅰ与鉴相器Ⅱ相连。本发明整体结构简单,设计合理,生成的频率信号具有低相位噪声低杂散和细步进以及宽带功能,是一种通用化频率源,可应用于多个平台。(The invention discloses a universal frequency synthesizer and a synthesis method, wherein the frequency synthesizer comprises a crystal oscillator, a comb spectrum circuit, a variable reference ring, a frequency divider I and a phase-locked loop which are sequentially connected, the phase-locked loop comprises a phase discriminator II, a filter V, a broadband VCO and a frequency divider II which are sequentially connected in a ring shape, the variable reference ring comprises a power divider I, a filter I, a DDS circuit, a phase discriminator I, a filter III, a CRO oscillator and a power divider II which are sequentially connected, the power divider I is further sequentially connected with a filter II, a mixer and a filter IV connected with the phase discriminator I, the power divider II is further respectively connected with the mixer and the frequency divider I, an amplifier is connected between the mixer and the power divider II, and the frequency divider I is connected with the phase discriminator II. The invention has simple integral structure and reasonable design, and the generated frequency signal has the functions of low phase noise, low stray, fine stepping and broadband, is a universal frequency source and can be applied to a plurality of platforms.)

1. The utility model provides a frequency synthesizer of universalization, includes the crystal oscillator, its characterized in that, still includes consecutive comb spectrum circuit, variable reference ring, frequency divider I and phase-locked loop, the phase-locked loop is including cyclic annular continuous phase discriminator II, wave filter V, broadband VCO and frequency divider II in proper order, variable reference ring is including consecutive merit branch ware I, wave filter I, DDS circuit, phase discriminator I, wave filter III, CRO oscillator and merit divide ware II, merit divides ware I still to have connected gradually wave filter II, mixer and the continuous wave filter IV of phase discriminator I, merit divides ware II still to be connected in mixer and frequency divider I respectively, be connected with the amplifier between mixer and the merit divides the ware II, frequency divider I links to each other with phase discriminator II.

2. The universal frequency synthesizer according to claim 1, wherein the first output terminal of the power divider i is connected to the first input terminal of the phase discriminator i through the filter i and the DDS circuit in sequence, and the second output terminal of the power divider i is connected to the first input terminal of the mixer through the filter ii.

3. The universal frequency synthesizer according to claim 2, wherein the output terminal of the phase detector i is connected to the input terminal of the power divider ii through the filter iii and the CRO oscillator in sequence, the first output terminal of the power divider ii is connected to the input terminal of the frequency divider i, the second output terminal of the power divider ii is connected to the second input terminal of the mixer through the amplifier, and the output terminal of the mixer is connected to the second input terminal of the phase detector i through the filter iv.

4. A universal frequency synthesizer according to claim 3, wherein the output terminal of the frequency divider i is connected to the first input terminal of the phase detector ii, the output terminal of the phase detector ii is connected to the input terminal of the filter v, the output terminal of the filter v is connected to the input terminal of the wideband VCO, the first output terminal of the wideband VCO is connected to the second input terminal of the phase detector ii through the frequency divider ii, and the second output terminal of the wideband VCO outputs the signal source.

5. A generalized frequency synthesizer according to claim 1, wherein said divider i is a 16 divider and said divider ii is a 4 divider.

6. A generalized frequency synthesizer in accordance with claim 1, characterized in that said filter iv is a low pass filter.

7. A generalized frequency synthesizer according to claim 1, wherein said crystal oscillator is a thermostatted crystal oscillator.

8. A method of synthesising a generalised frequency synthesiser as claimed in any one of claims 1 to 7 including the steps of:

1) the crystal oscillator generates a first reference signal through oscillation, and the first reference signal is sent to the comb spectrum circuit to generate a comb spectrum signal and output the comb spectrum signal;

2) the comb spectrum signal is divided into two paths through a power divider I to be output: one path of the signal is filtered and stray by a filter I and is expanded to generate a second signal which is provided to a DDS circuit as a reference clock, and the DDS circuit simultaneously generates an intermediate frequency signal which is provided to a phase discriminator I as a reference signal; one path is filtered and stray by a filter II and is expanded to generate a third signal which is provided for a frequency mixer to perform interpolation local oscillation;

3) dividing a radio frequency signal of the CRO oscillator into two paths for output through a power divider II, amplifying one path of the radio frequency signal through an amplifier, transmitting the amplified radio frequency signal to a mixer so as to be mixed with a third signal, filtering stray signals through a filter IV, transmitting the amplified radio frequency signal to a phase discriminator I, performing phase discrimination comparison on the phase discriminator I and intermediate frequency signals output by a DDS circuit, transmitting the phase discriminator I and the intermediate frequency signals to a filter III, filtering stray signals through the filter III, transmitting the filtered radio frequency signals to the CRO oscillator to form a closed loop, completing a phase locking function, and generating an S-band variable reference signal;

4) the variable reference signal of the S wave band is transmitted to a frequency divider I through a power divider II for frequency division to generate a low-frequency signal which is used as a reference signal of a phase discriminator II;

5) and after frequency division is carried out on the radio frequency signal of the broadband VCO through the frequency divider II, the radio frequency signal is transmitted to the phase discriminator II, phase discrimination comparison is carried out on the radio frequency signal and a low-frequency signal generated by the frequency divider I, a low-frequency error signal is output and sent to the filter V, stray is filtered out through the filter V, and then a low-frequency direct current signal is output to tune the broadband VCO oscillator, a loop is formed, the phase locking function is completed, and a frequency signal is synthesized.

Technical Field

The invention relates to the technical field of radio frequency microwave, in particular to a universal frequency synthesizer and a synthesis method.

Background

The frequency synthesizer is an important component of electronic systems such as radars, instrument tests, electronic reconnaissance and countermeasure, navigation, space flight and communication, and the like, and at present, the demand of the electronic systems for generalization of the frequency synthesizer is more and more urgent; and a universal frequency synthesizer can be applied to a plurality of platforms, so that the redesign cost and the redesign risk are reduced. Therefore, low phase noise, low spurs, ultra-small frequency hopping steps, and wideband synthesis are important indicators of frequency synthesizer designers.

At present, a plurality of frequency synthesizer design schemes exist, but the schemes cannot simultaneously give consideration to low phase noise, low spurious, ultra-small frequency hopping stepping and broadband synthesis, and can not realize generalization. For example, only by adopting a direct analog synthesis method, a low-phase noise index is easily obtained, but an ultra-small frequency hopping step and high spurious suppression index are not easy to make, and the bandwidth is not easy to make; only a direct digital synthesis method is adopted, so that low-phase noise indexes and superfine small stepping signals are easily obtained, but the signal frequency is low and the bandwidth is narrow; only the method of indirect phase-locked frequency synthesis is adopted, the broadband can be made, but the ultra-fine small step and high spurious suppression indexes are difficult to meet at the same time.

Chinese granted patent publication No. CN207427123U, publication date 2018, 5.9, discloses an ultra wide band low phase noise frequency source using the phase-locked loop filtering principle, which "includes a reference crystal oscillator, a main loop circuit and an auxiliary loop circuit; the reference crystal oscillator outputs three paths of reference signals, the output end of the first path of reference signal is connected with the signal input end of the frequency doubling link, the main loop circuit comprises a comb spectrum harmonic generator, the output end of the second path of reference signal of the reference crystal oscillator is connected with the signal input end of the comb spectrum harmonic generator, the auxiliary loop circuit comprises a second phase discriminator and a second amplifier, and the output end of the third path of reference signal of the reference crystal oscillator is connected with the reference input end of the second phase discriminator. The auxiliary loop circuit in the prior art is directly added in the phase-locked loop circuit, the structure is complex, the synthesis steps are complex, three paths of reference signals are output by the reference crystal oscillator, and only three filters are arranged in the transmission process of part of the reference signals, the high spurious suppression indexes are general in realization effect, and the technical problem of universal frequency source synthesis which simultaneously has low phase noise, low spurious, ultra-small frequency hopping stepping and broadband synthesis indexes cannot be solved.

Disclosure of Invention

The invention aims to provide a universal frequency synthesizer and a synthesis method, and aims to solve the technical problems that the existing frequency synthesizer proposed in the background technology has a complex structure, complicated synthesis steps and a general loop filtering effect, cannot simultaneously give consideration to low phase noise, low spurious, ultra-small frequency hopping stepping and broadband indexes, and cannot synthesize a universal frequency source well.

In order to achieve the purpose, the invention adopts the following technical scheme:

a universal frequency synthesizer comprises a crystal oscillator, a comb spectrum circuit, a variable reference ring, a frequency divider I and a phase-locked loop which are sequentially connected, wherein the phase-locked loop comprises a phase discriminator II, a filter V, a broadband VCO and a frequency divider II which are sequentially connected in a ring shape; the crystal oscillator is a constant-temperature crystal oscillator, the frequency divider I is a 16-frequency divider, the frequency divider II is a 4-frequency divider, and the filter IV is a low-pass filter.

Wherein, the first output end of the power divider I is connected with the first input end of the phase discriminator I through the filter I and the DDS circuit in sequence, the second output end of the power divider I is connected with the first input end of the frequency mixer through the filter II, the output end of the phase discriminator I is connected with the input end of the power divider II through the filter III and the CRO oscillator in sequence, the first output end of the power divider II is connected with the input end of the frequency divider I, the second output end of the power divider II is connected with the second input end of the frequency mixer through the amplifier, the output end of the frequency mixer is connected with the second input end of the phase discriminator I through the filter IV, the output end of the frequency divider I is connected with the first input end of the phase discriminator II, the output end of the phase discriminator II is connected with the input end of the filter V, the output end of the filter V is connected with the input end of the broadband, the first output end of the VCO broadband is connected with the second input end of the phase discriminator II through the frequency divider II, a second output of the wideband VCO outputs a signal source.

The invention also provides a synthesis method of the universal frequency synthesizer, which comprises the following specific operation steps:

1) the crystal oscillator generates a first reference signal through oscillation, and the first reference signal is sent to the comb spectrum circuit to generate a comb spectrum signal and output the comb spectrum signal;

2) the comb spectrum signal is divided into two paths through a power divider I to be output: one path of the signal is filtered and stray by a filter I and is expanded to generate a second signal which is provided to a DDS circuit as a reference clock, and the DDS circuit simultaneously generates an intermediate frequency signal which is provided to a phase discriminator I as a reference signal; one path is filtered and stray by a filter II and is expanded to generate a third signal which is provided for a frequency mixer to perform interpolation local oscillation;

3) dividing a radio frequency signal of the CRO oscillator into two paths for output through a power divider II, amplifying one path of the radio frequency signal through an amplifier, transmitting the amplified radio frequency signal to a mixer so as to be mixed with a third signal, filtering stray signals through a filter IV, transmitting the amplified radio frequency signal to a phase discriminator I, performing phase discrimination comparison on the phase discriminator I and intermediate frequency signals output by a DDS circuit, transmitting the phase discriminator I and the intermediate frequency signals to a filter III, filtering stray signals through the filter III, transmitting the filtered radio frequency signals to the CRO oscillator to form a closed loop, completing a phase locking function, and generating an S-band variable reference signal;

4) the variable reference signal of the S wave band is transmitted to a frequency divider I through a power divider II for frequency division to generate a low-frequency signal which is used as a reference signal of a phase discriminator II;

5) and after frequency division is carried out on the radio frequency signal of the broadband VCO through the frequency divider II, the radio frequency signal is transmitted to the phase discriminator II, phase discrimination comparison is carried out on the radio frequency signal and a low-frequency signal generated by the frequency divider I, a low-frequency error signal is output and sent to the filter V, stray is filtered out through the filter V, and then a low-frequency direct current signal is output to tune the broadband VCO oscillator, a loop is formed, the phase locking function is completed, and a frequency signal is synthesized.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention adopts a mixed frequency synthesis mode combining direct analog synthesis, direct digital synthesis and indirect digital phase-locked synthesis, utilizes the direct analog synthesis and direct digital synthesis modes to generate a variable narrow-band reference signal of an S wave band, generates a final frequency signal of 10-20G through a frequency division phase-locked synthesis mode after frequency division of the variable narrow-band reference signal of the S wave band, and consists of a crystal oscillator, a comb spectrum circuit, a variable reference ring, a frequency divider I and a broadband phase-locked loop which are sequentially connected, has simple integral structure and reasonable design, generates the frequency signal with low phase noise, low spurious fine stepping and broadband functions, is a universal frequency source and can be applied to a plurality of platforms;

2. the comb spectrum signal is divided into two paths through the power divider and is transmitted to the variable reference ring, wherein a line from the power divider I to the phase discriminator I is provided with a filter I, a line from the power divider I to the mixer is provided with a filter II, a line from the mixer to the phase discriminator I is provided with a filter IV, a line from the phase discriminator I to the power divider II is provided with the filter IV, meanwhile, an S-band variable reference signal generated by the variable reference ring is transmitted to the phase-locked loop after frequency division, the phase-locked loop is provided with a filter V, and in the whole frequency source synthesis process, all key transmission lines of the signal are provided with the filters, so that the loop filtering characteristic is exerted to the maximum extent to filter out stray signals, and the low stray characteristic of frequency source output is greatly improved.

Drawings

FIG. 1 is a block diagram of the modules of the present invention.

Detailed Description

Embodiments of the present invention are described below with reference to the accompanying drawings:

as shown in fig. 1, a generalized frequency synthesizer includes a crystal oscillator, a comb spectrum circuit, a variable reference ring, a frequency divider i and a phase-locked loop, which are connected in sequence, where the phase-locked loop includes a phase discriminator ii, a filter v, a wideband VCO and a frequency divider ii, which are connected in sequence in a ring shape, and the variable reference ring includes a power divider i, a filter i, a DDS circuit, a filter ii, a phase discriminator i, a filter iii, a CRO oscillator, a power divider ii, an amplifier, a mixer and a filter iv.

Wherein, the first output end of the power divider I is connected with the first input end of the phase discriminator I through the filter I and the DDS circuit in sequence, the second output end of the power divider I is connected with the first input end of the frequency mixer through the filter II, the output end of the phase discriminator I is connected with the input end of the power divider II through the filter III and the CRO oscillator in sequence, the first output end of the power divider II is connected with the input end of the frequency divider I, the second output end of the power divider II is connected with the second input end of the frequency mixer through the amplifier, the output end of the frequency mixer is connected with the second input end of the phase discriminator I through the filter IV (low pass filter), the output end of the frequency divider I is connected with the first input end of the phase discriminator II, the output end of the phase discriminator II is connected with the input end of the filter V, the output end of the filter V is connected with the input end of the broadband VCO, the first output end of the broadband VCO is connected with the second input end of the phase discriminator II through the frequency divider II, a second output of the wideband VCO outputs a signal source.

The synthesis method of the generalized frequency synthesizer comprises the following specific operation steps:

firstly, an external constant-temperature crystal oscillator oscillates to generate a 100MHz reference signal, the reference signal is sent to a comb spectrum circuit, and after the 100MHz comb spectrum signal is generated, the reference signal is divided into two paths through a power divider I to be output: one path generates 1200MHz signals with high stray rejection degree after being filtered and expanded by the filter I; one path is filtered by the filter II to remove stray and expanded, and then generates 3200MHz signals with high stray rejection degree and provides the 3200MHz signals to a frequency mixer for interpolation local oscillation; the 1200MHz signal is provided for the DDS circuit as a reference clock, the DDS circuit generates a fine stepping intermediate frequency signal at the same time, the frequency range of the intermediate frequency signal is 12-80MHz, the intermediate frequency signal is provided for the phase discriminator I to be used as a reference signal, and the 3200MHz signal is provided for the mixer to be used as an interpolation local oscillator; meanwhile, dividing a radio frequency signal of the CRO oscillator into two paths for output through a power divider II, amplifying one path of the radio frequency signal through an amplifier, transmitting the amplified signal to a mixer so as to be mixed with a 3200MHz signal, filtering stray signals through a filter IV, transmitting the filtered signal to a phase discriminator I, performing phase discrimination comparison on the phase discriminator I and an intermediate frequency signal output by a DDS circuit, transmitting the phase discriminated signal to a filter III, filtering stray signals through a filter III, transmitting the filtered signal to the CRO oscillator to form a closed loop, completing a phase locking function, and generating a 3212-frequency 3280MHz S-band variable reference signal; then, the variable reference signal of the S wave band is transmitted to a frequency divider I through a power divider II for frequency division, the frequency divider I is a 16-frequency divider, and a low-frequency signal of 200.75-205MHz is generated and used as a reference signal of a phase discriminator II; and finally, frequency division is carried out on the radio frequency signal of the broadband VCO through a frequency divider II, the radio frequency signal is transmitted to a phase discriminator II, phase discrimination comparison is carried out on the radio frequency signal and the low frequency signal generated by the frequency divider I, a low frequency error signal is output and transmitted to a filter V, stray is filtered out through the filter V, the frequency divider II is a 4-frequency divider, a low frequency direct current signal is output to tune the broadband VCO oscillator, a loop is formed, the phase locking function is completed, and finally a 10-20G universal frequency source is generated.

The S-band variable reference signal is generated by interpolation mixing of an interpolation local oscillator and a DDS intermediate frequency signal, the interpolation local oscillator and a DDS clock are both from the comb spectrum circuit S-band variable reference signal, the phase noise is very low, and the phase noise relation between the interpolation local oscillator and the DDS clock and the crystal oscillator signal meets 20 lgN; and after frequency division of the S-band variable reference signal, the S-band variable reference signal and a broadband VCO are phase-locked to synthesize a final frequency source in a range of 10-20G, wherein the phase-locked mode is an integer mode, the noise floor of the phase discriminator II is very low, the noise contribution of the S-band variable reference signal is lower than that of a subsequent phase discriminator II, the finally output phase noise of the 10-20G generalized frequency source directly depends on the noise floor of the phase discriminator II, and the low-noise phase discriminator II is selected to meet the low-phase noise requirement of the generalized frequency source.

The frequency hopping of the intermediate frequency signal output by the DDS circuit is stepped, the mu Hz level is met, and the near-end stray index is high; in summary, since the S-band variable reference signal is generated by interpolating and mixing the local oscillator and the DDS intermediate frequency signal, the near-end spurious signal of the S-band variable reference signal mainly depends on the near-end spurious of the intermediate frequency signal output by the DDS circuit, which is better than 88 dBc; therefore, the frequency source near-end stray in the range of 10-20G only depends on the variable reference signal of the S wave band, the degradation is about 16dB, and 70dBc is met; and the frequency modulation step of the frequency source in the range of 10-20G is also dependent on the S-band variable reference signal, satisfying the level of muHz.

Finally, the typical phase noise of the frequency source: < -93dBc @1 KHz; stray: < -70 dBc; frequency hopping and stepping: less than 0.1 Hz; the synthesis range is as follows: 10-20 GHz. The frequency source signal has the functions of low phase noise, low spurious, fine stepping and broadband, and is a universal frequency source.