CN108169720B - X-band low-phase noise navigation frequency modulation continuous wave radar transmitting system - Google Patents
X-band low-phase noise navigation frequency modulation continuous wave radar transmitting system Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
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Abstract
The invention relates to an X-band low-phase noise navigation frequency modulation continuous wave radar transmitting system, which consists of a linear frequency modulation module, a frequency mixing type phase-locked loop module, a high-stability local oscillation module and a frequency multiplication power amplification module; the linear frequency modulation module comprises a first oscillator, a DDS, a first band-pass filter and a microprocessor; the mixing type phase-locked loop module is formed by sequentially connecting a phase discriminator, a loop filter, a voltage-controlled oscillator, a mixer and a second band-pass filter; the high-stability local oscillation module is formed by connecting a second oscillator and a first frequency multiplier, and the output end of the first frequency multiplier is connected with a mixer of the mixing type phase-locked loop module; the frequency multiplication power amplification module is mainly formed by sequentially connecting a second frequency multiplier, a radio frequency filter and a power amplifier, wherein the input end of the second frequency multiplier is connected with the other output end of the voltage-controlled oscillator of the frequency mixing type phase-locked loop module, and the power amplifier outputs an X-band linear frequency modulation signal. The invention has the advantages of improving the phase noise performance, reducing the cost and the like.
Description
Technical Field
The invention belongs to the technical field of navigation radar transmitting systems, and particularly relates to a marine X-band navigation frequency modulation continuous wave radar transmitting system.
Background
The marine navigation radar is mainly used for detecting and tracking marine targets, assists in ship navigation collision avoidance and ensures navigation safety.
The traditional marine navigation radar is based on a non-coherent pulse magnetron system, but is limited by the system, and has the following limitations: 1. the magnetron generally needs 3 minutes of preheating time and cannot be directly used; 2. the distance resolution of the magnetron radar is limited by the width of the modulation pulse, and the distance resolution is poor when the magnetron radar is far away; 3. the minimum working distance is limited due to the influence of magnetron leakage pulses; 4. the magnetron needs high-voltage modulation, so that the reliability of the whole radar is reduced; 5. the magnetron needs to be replaced after being used for a period of time, and the maintenance cost is increased.
Along with the development of technology, the solid-state navigation radar adopting the linear frequency modulation technology has the advantages of using solid-state devices, being good in reliability, needing no preheating time, good in distance resolution, small in minimum acting distance, small in transmitting power, free of radiation damage to human bodies, low in price and the like, but because the linear frequency modulation continuous wave radar adopts the solid-state oscillator to generate the transmitted linear frequency modulation signals, the final low-frequency signals can be directly generated after the transmitted signals and the received echo signals are mixed in a coherent manner, and the phase noise of a radar transmitting system can directly influence the detection capability of the radar system on small targets, which is an unresolved problem, so that how to reduce the phase noise of the whole transmitting system is a research focus and a problem to be solved urgently.
Disclosure of Invention
The invention aims to overcome the defects that the phase noise of an X-band low-phase noise navigation frequency modulation continuous wave radar transmitting system in the prior art directly influences the detection capability of the radar system on small targets and is high in price, and provides the X-band low-phase noise navigation frequency modulation continuous wave radar transmitting system which can reduce the design and manufacturing cost and optimize the noise coefficient.
The aim of the invention is achieved by the following technical scheme.
An X-band low-phase noise navigation frequency modulation continuous wave radar transmitting system is characterized by mainly comprising a linear frequency modulation module, a frequency mixing type phase-locked loop module, a high-stability local oscillation module and a frequency multiplication power amplification module; the linear frequency modulation module comprises a first oscillator, a DDS (direct digital synthesizer), a first band-pass filter and a microprocessor, wherein the input end of the DDS is connected with the first oscillator, the output end of the DDS is connected with the first band-pass filter, and the DDS is controlled by the microprocessor which is electrically connected with the DDS; the frequency mixing type phase-locked loop module is formed by sequentially connecting a phase discriminator, a loop filter, a voltage-controlled oscillator, a frequency mixer and a second band-pass filter into a closed loop, and the phase discriminator is connected with the output end of the first band-pass filter of the linear frequency modulation module; the high-stability local oscillation module is formed by connecting a second oscillator and a first frequency multiplier, and the output end of the first frequency multiplier is connected with a mixer of the mixing type phase-locked loop module; the frequency multiplication power amplification module is mainly formed by sequentially connecting a second frequency multiplier, a radio frequency filter and a power amplifier, wherein the input end of the second frequency multiplier is connected with the other output end of the voltage-controlled oscillator of the frequency mixing type phase-locked loop module, and the power amplifier outputs an X-band linear frequency modulation signal.
And outputting a signal to the DDS by a first vibration source of the linear frequency modulation module, wherein the first oscillator is used as a reference clock of the DDS. The DDS is controlled by a microprocessor, can directly generate a linear frequency modulation signal, and has good modulation linearity and small phase noise; the linear frequency modulation signal output by the DDS is filtered by a first band-pass filter, then the linear frequency modulation signal enters a frequency discriminator and a loop filter of a frequency mixing type phase-locked loop module and is input into a voltage-controlled oscillator, one voltage-controlled oscillator is output by two paths, one voltage-controlled oscillator is transmitted to a frequency multiplication power amplification module of the system, and the other voltage-controlled oscillator is added with a feedback signal and is transmitted to the frequency mixer; meanwhile, a second oscillator of the high-stability local oscillator module generates a local oscillator signal with relatively lower frequency, the local oscillator signal is subjected to frequency multiplication by a first frequency multiplier of the high-stability local oscillator module and then is input into a mixer of the mixed phase-locked loop module, the mixer is mixed with the other path of signal output by the voltage-controlled oscillator to generate an intermediate frequency signal, and the intermediate frequency signal is used as a feedback signal to enter the phase discriminator to form a closed-loop phase lock after passing through a second band-pass filter; after the phase of the mixed phase-locked loop is locked, the feedback signal is consistent with the phase of the output reference signal of the linear frequency modulation module. The output signal of the frequency mixing phase-locked loop module is transmitted to a second frequency multiplier of the frequency multiplication power amplification module by the voltage-controlled oscillator, and the signal output by the second frequency multiplier is filtered by the radio frequency filter and amplified by the power amplifier, so that an X-band linear frequency modulation signal is finally output.
The technical key point of the invention is that a phase-locked loop (PLL) design working at a lower frequency than an X-band is adopted, and a frequency multiplication mode is used to convert signals into the X-band, so that the complexity of a system is slightly increased, the cost of system design and manufacture and the noise coefficient of optimization are greatly reduced.
Preferably, the first oscillator adopts a surface acoustic wave oscillator, and the first oscillator is used as a reference clock of the DDS, and the working frequency of the first oscillator is 868MHz; the frequency of the mixed phase-locked loop module is locked at about 4.3 GHz.
The design adopts the design of the frequency mixing phase-locked loop module with the frequency of about 4.3GHz, compared with the design of 8-12GHz of the frequency of the X wave band, the frequency is lower than the frequency of the X wave band, namely, the voltage-controlled oscillator and the frequency mixer with lower price can be adopted, and the design and manufacturing cost can be greatly saved. The linear frequency modulation signal output by the frequency mixing type phase-locked loop module enters the frequency multiplication power amplification module and is changed to the X-band radio frequency after frequency multiplication.
The prior art directly generates an X wave band, and the structure is high in cost, particularly, because an N-times frequency divider is used in a phase-locked loop closed loop, the phase noise of a signal in the bandwidth of a loop filter can be eventually deteriorated by 20log (N) dB on the basis of the phase noise of a DDS reference signal, and the invention avoids the defect.
In the preferred scheme, an AD9957 chip of ADI company is selected as the DDS, and an 8-order Chebishov band-pass filter with 1dB ripple fluctuation in the passband is connected to an AD9557 output port.
After AD9557 is output, a Chebishov band-pass filter with 8-order and 1dB ripple fluctuation in the passband is designed, so that a high-quality intermediate-frequency linear frequency modulation signal can be obtained.
Preferably, the phase detector is an ADF4002 chip from ADI, and the ADF4002 is composed of a low noise digital phase detector, a precise current pump, a programmable N-times frequency divider and a 14-bit reference counter.
The voltage-controlled oscillator adopts ROS_4725_119 of Mini Circuits company, and has excellent performance, and the non-harmonic spurious suppression degree can reach 90dBc.
Preferably, the loop filter adopts a 3-order passive loop filter, and the bandwidth of the loop filter is 15MHz.
Preferably, the output port of the voltage controlled oscillator is connected to a linear amplifier implemented using BFP640 transistor from Infrax.
This is not only used to amplify the output power of the voltage controlled oscillator, but also to reduce the pulling effect of the voltage controlled oscillator and to improve the frequency stability of the output of the voltage controlled oscillator.
The design of the high-stability local oscillator module is based on a high-stability surface acoustic wave oscillator, the output frequency of the oscillator is multiplied by 5 and then is output, the signals output by the 5 times of frequency and the signals output by the voltage-controlled oscillator are mixed by a mixer to generate an intermediate frequency feedback signal, and the intermediate frequency feedback signal is filtered by a second band-pass filter to inhibit fundamental waves and other unused harmonic components and only retain 5 times of harmonic components.
The surface acoustic wave oscillator is also realized by adopting a colpitts structure and a surface acoustic wave resonator, and in order to better improve the phase noise performance of the surface acoustic wave oscillator, the surface acoustic wave resonator is selected from RO3164D-3 of RFM company.
Preferably, the second frequency multiplier adopts a Infrax BFP640 triode which is biased in a B-type amplifying region, and the output frequency of the voltage-controlled oscillator is multiplied to an X wave band by utilizing the nonlinearity of the amplifier; the output end of the filter is connected with a 4-order Butterworth band-pass filter.
The beneficial effects of the invention are as follows:
1. the N frequency divider in a phase-locked loop closed loop in the prior art is avoided, so that the 20log (N) dB phase noise performance of the whole system is improved;
2. the technical scheme that the PLL working at lower frequency is adopted, and then the frequency multiplication mode is used to convert signals into X wave bands is adopted, so that the system design cost is well reduced;
3. the defect of poor modulation linearity of the linear frequency modulation signal generated by directly controlling the voltage-controlled oscillator of the X-band through voltage in the prior art is avoided, and the defects of phase noise and high cost existing in the generation of the X-band frequency modulation signal through the DDS, the mixer and the oscillator are overcome;
4. the phase noise performance improves the detection capability of the radar system on small targets;
5. after AD9557 is output, an 8-order Chebishov band-pass filter with 1dB ripple fluctuation in a passband is designed, and the out-of-band rejection degree non-harmonic spurious suppression degree is improved to 90dBc.
6. The output end of the voltage-controlled oscillator is connected with a linear amplifier realized by adopting BFP640 triode of Indeluxe company, which is not only used for amplifying the output power of the voltage-controlled oscillator, but also is used for reducing the traction effect of the voltage-controlled oscillator and improving the frequency stability of the output of the voltage-controlled oscillator.
7. A3-order passive loop filter is adopted, the defect that the low-bandwidth loop filter reduces the locking time of the phase-locked loop is overcome, and the bandwidth of the loop filter is 15MHz.
Drawings
FIG. 1 is a block schematic diagram of the structure of one embodiment of the present invention;
FIG. 2 is a block diagram of a prior art voltage controlled oscillator generating an X-band FM signal;
FIG. 3 is a block diagram of a prior art method for generating an X-band FM signal directly through a DDS, a mixer and an oscillator;
FIG. 4 is a block diagram of a prior art method for generating an X-band FM signal by a DDS and N-fold phase locked loop;
fig. 5 is a schematic diagram showing an actual measurement of a frequency of a transmitted chirp signal of an X-band low-phase noise marine navigation fm continuous wave radar transmitting system according to an embodiment of the invention.
In the figure, a chirp module 1; a first oscillator 11; DDS12; a first band-pass filter 13; a microprocessor 14; a mixer-type phase-locked loop module 2; a phase detector 21; a loop filter 22; a voltage-controlled oscillator 23; a mixer 24; a second band-pass filter 25; a high-stability local oscillation module 3; a second oscillator 31; a first frequency multiplier 32; a frequency multiplication power amplification module 4; a second frequency multiplier 41; a radio frequency filter 42; a power amplifier 43.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the attached drawings: the present embodiment is implemented on the premise of the technical scheme of the present invention, and a detailed implementation manner and a specific operation process are provided, but the protection scope of the present invention is not limited to the following embodiments.
Examples: as shown in FIG. 1, an X-band low-phase noise navigation frequency modulation continuous wave radar transmitting system mainly comprises a linear frequency modulation module 1, a frequency mixing type phase-locked loop module 2, a high-stability local oscillation module 3 and a frequency multiplication power amplification module 4; the linear frequency modulation module 1 comprises a first oscillator 11, a DDS (direct digital synthesizer) 12, a first band-pass filter 13 and a microprocessor 14, wherein the input end of the DDS12 is connected with the first oscillator 11, the output end of the DDS12 is connected with the first band-pass filter 13, and the DDS12 is controlled by the microprocessor 14 electrically connected with the DDS12; the frequency mixing type phase-locked loop module 2 is formed by sequentially connecting a phase discriminator 21, a loop filter 22, a voltage controlled oscillator 23, a frequency mixer 24 and a second band-pass filter 25 into a closed loop, wherein the phase discriminator 21 is connected with the output end of the first band-pass filter 13 of the linear frequency modulation module 1; the high-stability local oscillation module 3 is formed by connecting a second oscillator 31 and a first frequency multiplier 32, and the output end of the first frequency multiplier 32 is connected with the mixer 24 of the mixed phase-locked loop module 2; the frequency multiplication power amplification module 4 mainly comprises a second frequency multiplier 41, a radio frequency filter 42 and a power amplifier 43 which are sequentially connected, wherein the input end of the second frequency multiplier 41 is connected with the other output end of the voltage-controlled oscillator 23 of the mixing type phase-locked loop module 2, and the power amplifier 43 outputs X-band linear frequency modulation signals.
In the chirp module 1, since the phase noise of the reference clock of the DDS12 directly affects the phase noise of the frequency signal generated by the DDS12, the first oscillator 11 in the chirp module 1 is implemented based on a colpitts structure and is matched with a surface acoustic wave resonator, and the surface acoustic wave resonator adopts RO3164D-3 of the RFM company, and the resonance frequency of the surface acoustic wave resonator is 868.35MHz. The first oscillator 11 generates a stable 868.35MHz oscillation frequency as a clock reference for the AD9957DDS12 chip. The microprocessor 14 uses STM32F103 of ST company as a micro-processing chip, and generates intermediate frequency linear frequency modulation signals by the microprocessor 14 digitally controlling AD9957, specifically, CS, SCLK and SDI/O pins of the AD9957 chip are controlled by a serial interface, and 290MHz to 310MHz linear frequency modulation signals, namely, the intermediate frequency is 300MHz and the bandwidth is 20 MHz. And then an 8-order Chebishov first band-pass filter 13 is adopted, the bandwidth of the first band-pass filter 13 is 20MHz, the center frequency is 300MHz, and the in-band fluctuation is 1dB, so that out-of-band spurious signals brought by the synthesis of DDS12 digital signals are effectively filtered. Because the 8-order chebishov band-pass filter adopts a lumped parameter design, attenuation in the whole band is larger, and the chirp module 1 finally outputs the ADF4002 phase discriminator 21 in the mixed phase-locked loop module 2 as a reference signal, the ADF4002 has certain requirements on the input amplitude of the reference signal, and therefore, the amplitude amplification is carried out on the generated chirp signal after the 8-order chebishov band-pass filter. The BFR193 broadband low-noise triode of the Infei-Rake company is adopted as an amplifying tube, the Wal-Diffuse circuit formed by the two low-noise triodes BFR193 is adopted as a low-noise amplifying circuit, and the Wal-Diffuse circuit can effectively reduce the Miller effect that the input capacitance of the input end of the amplifier is obviously increased, so that the bandwidth of the low-noise amplifier is improved.
The technical scheme of the invention avoids the defect of poor modulation linearity of the linear frequency modulation signal generated by directly controlling the voltage-controlled oscillator of the X wave band to generate the linear frequency modulation signal by voltage in the prior art, and is shown in figures 2 and 3.
The technical scheme of the invention also overcomes the defects of phase noise and high cost existing in the generation of X-band frequency modulation signals through the DDS, the mixer and the oscillator, and is shown in fig. 4.
After being amplified, the chirped signal enters a REFIN pin of the ADF4002 phase discriminator 21 of the mixer-type phase-locked loop module 2. Microprocessor 14 also connects the LE, CLK and DATA pins of ADF4002 phase detector 21 through a serial interface, controls phase detector 21, and sets the value of loop divide N to 1. The feedback loop pin RFINA of the ADF4002 phase detector 21 receives a closed loop feedback loop signal generated by mixing signals from the voltage controlled oscillator 23 and the high stability local oscillator module 3. The frequency-mixing phase-locked loop module 2 adopted in the design removes an N-times frequency divider of a traditional phase-locked loop on a closed loop, and adopts a mode of mixing with another local oscillator F1 to convert the frequency of the voltage-controlled oscillator Fvco to the frequency Fvco-F1 of an intermediate frequency signal, and because the frequency mixer 24 can generate some spurious frequency spurious, the mixed signal passes through a second band-pass filter 25 and then enters the phase discriminator 21 for phase comparison, and when the phase-locked loop is locked, the output frequency of the first oscillator 11 is Fvco=F1+Fref. The advantage of this design is that the output phase noise of Fvco is not corrupted by 20log (N) dB. This also effectively improves the output phase noise performance.
The phase detector 21 in this design uses ADF4002 chips from ADI corporation, where the ADF4002 consists of a low noise digital phase detector, a precision current pump, a programmable N-fold frequency divider and a 14-bit reference counter. The voltage controlled oscillator 23 is selected from ROS_4725_119 of Mini Circuits. The performance is excellent, and the non-harmonic spurious suppression degree can reach 90dBc.
The most important design and difficulty in designing a PLL design is the loop filter 22, and the performance of the loop filter 22 has a significant impact on the output frequency lock time, signal frequency spurs, phase noise, and stability of the overall phase locked loop. A low bandwidth loop filter 22 may enhance spurious and phase noise performance but may reduce the time that the phase locked loop locks. A 3-order passive loop filter is used in this design. The loop filter bandwidth is 15MHz.
The output of the voltage-controlled oscillator 23 is connected with a linear amplifier realized by adopting BFP640 triode of Ying Fei Ling company, which is not only used for amplifying the output power of the voltage-controlled oscillator, but also is more important to reduce the traction effect of the voltage-controlled oscillator 23 and improve the frequency stability of the output of the voltage-controlled oscillator 23.
Because the signal of the high-stability local oscillator module 3 is mixed with the frequency output by the voltage-controlled oscillator 23 to generate the intermediate frequency feedback signal entering the phase discriminator 21, the phase noise performance of the high-stability local oscillator module 3 directly affects the phase noise performance of the intermediate frequency feedback signal, and aiming at the defect, the high-stability local oscillator module 3 is designed based on a high-stability surface acoustic wave oscillator, then the output frequency of the second oscillator 31 is output after being multiplied by 5, the output frequency is then passed through the second band-pass filter 25, fundamental waves and other unused harmonic components are restrained, only 5 harmonic components are reserved, and finally the 5 harmonic components are amplified and output, so that the influence of the phase noise of the high-stability local oscillator module 3 on the phase noise performance of the mixed intermediate frequency feedback signal can be overcome. The surface acoustic wave oscillator is also realized by adopting a colpitts structure and a surface acoustic wave resonator, and in order to better improve the phase noise performance of the surface acoustic wave oscillator, the surface acoustic wave resonator is selected from RO3164D-3 of RFM company. The working frequency of the surface wave resonator is 868.35MHz, the idle quality factor is 24000, the 50 ohm load quality factor is 4000, and the frequency temperature coefficient is only 0.032 ppm/DEG C. The 5-frequency multiplier is realized by adopting an MGA86563 low-noise GaAs MMIC amplifier of Agilent company, the working frequency of MGA86563 can work to 6GHz, MGA86563 is biased in a B-class amplifying region, 5-order harmonic components are generated by utilizing nonlinearity of MGA86563, after being filtered by a second band-pass filter 25, 5-order harmonic frequency components are amplified linearly by utilizing a BFP640 triode of Infei-Ling company (BFP 640 is biased in a A-class linear amplifying region), and a signal of 4.341GHz is generated after 868.35MHz is subjected to 5-frequency multiplication.
The frequency-doubling power amplification module 4 mainly consists of a second frequency multiplier 41, a microstrip bandpass (radio frequency) filter 42 and a power amplifier 43. The second frequency multiplier 41 employs a Infrax BFP640 triode biased in the class B amplifying region to multiply the output frequency of the voltage controlled oscillator 23 to the X band, i.e., a chirp signal having a center frequency of 9.282GHz and a bandwidth of 40MHz, by utilizing the nonlinearity of the amplifier. Since the second frequency multiplier introduces other harmonic components, a 4-order Butterworth band-pass filter is designed at the output of the second frequency multiplier, and the Butterworth filter has good in-band flatness, so that the power amplitude of the frequency-multiplied linear frequency modulation signal cannot be influenced, and the design of the whole filter is realized by adopting a microstrip line because the second frequency multiplier works in an X band. The 4-order butterworth band-pass filter has a bandwidth of 1.5GHz and an insertion loss of 0.5dB. After passing through the rf filter 42, the signal enters the power amplifying circuit. In order to save the design cost, the design does not use an expensive single-chip X-band power amplification chip, but adopts a mode of combining series connection and parallel connection to design the whole power amplification circuit. The power amplifier consists of a 2-stage serial amplifying driving circuit and a 1-stage parallel amplifying circuit. The 1 st stage of the serial amplification driving circuit adopts an amplifying circuit designed by a BFP64 triode, the 2 nd stage adopts an amplifying circuit designed by an NLB-400 chip, signals are divided into two paths through a microstrip power distribution circuit and are respectively subjected to power amplification, the 2 paths of signals after power distribution are respectively amplified in series through the NLB-400 chip and a power amplifying circuit designed by a BFP650 triode, and the two paths of amplified signals are subjected to power synthesis through a microstrip power synthesis circuit and output through an SMA interface after being further filtered through a radio frequency filter 43. The gain of the entire power amplifier is 21dB and the peak power of the final output signal is 20dBm.
The X-band low-phase noise marine navigation frequency modulation continuous wave radar transmitting system is provided with two power supply modules, and the power supply modules provide required working voltage and current for each module. The linear frequency modulation module 1 is connected to the mixed phase-locked loop module 2 through an SMA cable, the high-stability local oscillation module 3 is also connected to the left side of the mixed phase-locked loop module 2 through an SMA connector, the output of the mixed phase-locked loop module 2 is connected to the frequency multiplication power amplification module 4 through the SMA connector, and finally the radio frequency linear frequency modulation signal is output through an output port.
Fig. 5 is a schematic diagram of the frequency of a chirp signal transmitted by the actually measured X-band low-phase noise marine navigation fm continuous wave radar transmitting system. As can be seen from the graph, the center frequency point of the frequency modulation signal is 9.28GHz, the bandwidth is 40MHz, and the output power is 19.24dBm. According to the measurement, when the output signal is 9.28GHz, the phase noise at the frequency offset of 1kHz is only-115 dBc/Hz. The performance of the phase noise is good, and the requirement of the marine navigation frequency modulation continuous wave radar on the phase noise can be completely met.
The X-band low-phase noise navigation frequency modulation continuous wave radar transmitting system has the advantages of improving the phase noise performance of the whole system, reducing the design cost of the system and the like. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (8)
1. An X-band low-phase noise navigation frequency modulation continuous wave radar transmitting system is characterized by comprising a linear frequency modulation module, a frequency mixing type phase-locked loop module, a high-stability local oscillation module and a frequency multiplication power amplification module; the linear frequency modulation module comprises a first oscillator, a DDS (direct digital synthesizer), a first band-pass filter and a microprocessor, wherein the input end of the DDS is connected with the first oscillator, the output end of the DDS is connected with the first band-pass filter, and the DDS is controlled by the microprocessor which is electrically connected with the DDS; the frequency mixing type phase-locked loop module is formed by sequentially connecting a phase discriminator, a loop filter, a voltage-controlled oscillator, a frequency mixer and a second band-pass filter into a closed loop, and the phase discriminator is connected with the output end of the first band-pass filter of the linear frequency modulation module; the high-stability local oscillation module is formed by connecting a second oscillator and a first frequency multiplier, and the output end of the first frequency multiplier is connected with a mixer of the mixing type phase-locked loop module; the frequency multiplication power amplification module is formed by sequentially connecting a second frequency multiplier, a radio frequency filter and a power amplifier, wherein the input end of the second frequency multiplier is connected with the other output end of the voltage-controlled oscillator of the frequency mixing type phase-locked loop module, and the power amplifier outputs an X-band linear frequency modulation signal.
2. The X-band low-phase noise navigation frequency modulation continuous wave radar transmitting system according to claim 1, wherein the first oscillator adopts a surface acoustic wave oscillator, the first oscillator is used as a reference clock of the DDS, and the working frequency of the first oscillator is 868MHz; the frequency of the mixed phase-locked loop module is locked at about 4.3 GHz.
3. The system of claim 2, wherein the DDS is an AD9957 chip of ADI company, and an 8-order chebishov band-pass filter with 1dB ripple fluctuation in passband is connected to the output port of AD 9557.
4. The system of claim 1, 2 or 3, wherein the phase detector is an ADF4002 chip from ADI corporation, the ADF4002 comprising a low noise digital phase detector, a precision current pump, a programmable N-fold divider and a 14-bit reference counter.
5. The X-band low phase noise pilot frequency modulated continuous wave radar transmission system of claim 4, wherein the loop filter is a 3-order passive loop filter, and the loop filter bandwidth is 15MHz.
6. The X-band low phase noise pilot frequency modulated continuous wave radar transmission system of claim 5, wherein the output port of the voltage controlled oscillator is connected to a linear amplifier implemented using a BFP640 triode from intel-fuling corporation.
7. The system of claim 6, wherein the high-stability local oscillator module is designed based on a high-stability surface acoustic wave oscillator, and the output frequency of the oscillator is multiplied by 5 and then output, the output signal of the 5 times frequency and the output signal of the voltage-controlled oscillator are mixed by a mixer to generate an intermediate frequency feedback signal, and the intermediate frequency feedback signal is filtered by a second bandpass to suppress fundamental wave and other unused harmonic components and only retain 5 times harmonic components.
8. The X-band low-phase noise pilot frequency modulated continuous wave radar transmission system of claim 7, wherein the second frequency multiplier employs a inflorescence BFP640 triode biased in a class B amplification region, which multiplies the output frequency of the voltage controlled oscillator to the X-band by the nonlinearity of the amplifier; the output end of the filter is connected with a 4-order Butterworth band-pass filter.
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| CN109714052B (en) * | 2018-12-19 | 2023-04-11 | 安徽华东光电技术研究所有限公司 | X-waveband coaxial medium frequency source |
| CN110830060B (en) * | 2019-11-26 | 2021-09-10 | 北京无线电测量研究所 | Radio frequency signal generating device and method |
| CN111585567B (en) * | 2020-01-03 | 2023-03-03 | 石家庄数英仪器有限公司 | Rapid tracking synchronous sampling system with frequency holding function |
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