CN101726712B - Radio frequency signal generating device - Google Patents
Radio frequency signal generating device Download PDFInfo
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- CN101726712B CN101726712B CN2009102728756A CN200910272875A CN101726712B CN 101726712 B CN101726712 B CN 101726712B CN 2009102728756 A CN2009102728756 A CN 2009102728756A CN 200910272875 A CN200910272875 A CN 200910272875A CN 101726712 B CN101726712 B CN 101726712B
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Abstract
本发明公开了一种射频信号产生装置，控制电路与数字频率合成器的配置端口相连接，控制电路与自动电平控制电路的运算放大器参考端相连，控制电路与压控振荡器调谐端相连，时钟分配电路与数字频率合成器、混频器、梳状谱产生电路相连，数字频率合成器与时钟分配电路、混频器相连，本振信号与开关相连，开关与正交调制电路本振输入端口相连，梳状谱产生电路输出端口与第三混频器相连，压控振荡器与第三混频器、混频器、控制电路相连，混频器与带通滤波器相连，带通滤波器与自动电平控制电路相连，自动电平控制电路输出端口与混频器相连，混频器与带通滤波器相连。本发明具有数字化控制、通用性好，成本低，频率设置灵活，杂散与相位噪声性能好。
The invention discloses a radio frequency signal generating device, the control circuit is connected with the configuration port of the digital frequency synthesizer, the control circuit is connected with the reference terminal of the operational amplifier of the automatic level control circuit, and the control circuit is connected with the tuning terminal of the voltage-controlled oscillator. The clock distribution circuit is connected with the digital frequency synthesizer, mixer and comb spectrum generation circuit, the digital frequency synthesizer is connected with the clock distribution circuit and the mixer, the local oscillator signal is connected with the switch, and the switch is connected with the quadrature modulation circuit local oscillator input The ports are connected, the output port of the comb spectrum generation circuit is connected with the third mixer, the voltage-controlled oscillator is connected with the third mixer, the mixer, and the control circuit, the mixer is connected with the band-pass filter, and the band-pass filter The device is connected with the automatic level control circuit, the output port of the automatic level control circuit is connected with the mixer, and the mixer is connected with the band-pass filter. The invention has digital control, good versatility, low cost, flexible frequency setting, and good stray and phase noise performance.
Description
Technical field
The present invention relates to the radio-frequency signal source technical field; More specifically relate to a kind of radio frequency signal generating device; A kind of digitized low noise radio-frequency signal source that carries out fast frequency switching and amplitude, phase modulation (PM), this device also can be used for nuclear magnetic resonance spectrometer and magnetic resonance imager.
Background technology
Radio-frequency signal source is the nuclear magnetic resonance apparatus essential important component.Typical radiofrequency signal compositor is frequency synthesizer (Programmable Test Source; PTS), it mainly by the standard frequency module (SGA, SGB); High frequency resolution generation module (DM; DMA) form with three frequency mixing module, three parts, wherein the standard frequency module produces several groups of standard frequencies and delivers to the high frequency resolution generation module, and the high frequency resolution generation module produces high-resolution signal through two mixing-frequency division method; Be transferred to three frequency mixing module then, the method through three mixing produces last output frequency.It is that radio frequency sending set and receiver provide local oscillation signal that existing NMR system radiating portion adopts the radiofrequency signal compositor, partly carries out exporting power amplifier to behind frequency, phase place and the amplitude modulation(PAM) at transmitter unit then.The annexation of existing NMR system radiating portion is: the output of frequency synthesizer is connected to rf broadband orthogonal modulation module local oscillation signal input end, as the local oscillation signal use of this module; The output of Direct Digital Frequency Synthesizers is connected to the middle frequency input terminal of rf broadband orthogonal modulation module; The controlled signal of frequency, phase place and the amplitude that Direct Digital Frequency Synthesizers produces is as the intermediate-freuqncy signal of rf broadband orthogonal modulation module, and intermediate-freuqncy signal and local oscillation signal export power amplifier to after rf broadband orthogonal modulation module is modulated.The problem that this structure exists is that the radiofrequency signal compositor only provides wide frequency ranges adjustable fundamental frequency signal; Other function uses the analog quadrature modulation technology to accomplish; And the analog quadrature modulation technical pattern of wide frequency ranges is complicated, and spurious signal suppresses ability simultaneously, costs an arm and a leg.
Summary of the invention
The objective of the invention is to be to provide a kind of radio frequency signal generating device; The present invention introduces local oscillation signal in three frequency mixing module of radiofrequency signal compositor; Make frequency synthesizer realize outside the signal source function, can not only accomplish the pulse emission function of transmitter, and can be used as the receiver local oscillator in the reception stage and use through the switching of different local oscillation signals; The former transmitter of instead, the economize on hardware cost.The present invention is with radiofrequency signal compositor and the integrated realization integrated design of transmitter, and this device has Digital Control, stable output signal, index is good, hardware cost is low, the expanding application scope.
To achieve these goals, the present invention adopts following technical measures:
Adopt programmable gate array (FPGA, Field Programmable Gate Array) as system's control core, simple in structure, operation facility; Adopt Direct Digital Frequency Synthesizers (DDS; Direct DigitalSynthesizer) alternative frequency synthesizer (PTS) internal standard frequency synthesis module (SGA; SGB) and the high frequency resolution generation module (DM DMA), realizes that frequency, phase place and amplitude are flexibly, switch apace; In three frequency mixing module, add the orthogonal modulation chip, the signal through selecting different frequency is as local oscillator, makes the different frequency of signal source output, thereby realizes the dual-use function of this signal source as the transmitter and receiver local oscillator.That incorporate design makes is simple in structure, cost is lower.
A kind of radio frequency signal generating device, it is made up of FPGA control circuit, signal generator module, three parts of three frequency mixing module.Wherein the FPGA control circuit is realized the quick configuration of Direct Digital Frequency Synthesizers (DDS), the reference input adjusting of automatic level control circuit (ALC) and the VT control of voltage controlled oscillator (VCO); Signal generator module provides the external timing signal of FPGA; And provide three frequency mixing module each input signal; Produce signal like local oscillation signal (LO, Local Oscillator), pectination spectrum signal and by Direct Digital Frequency Synthesizers (DDS) and clock distribution circuit through frequency mixer (Mixer 1) mixing; Three frequency mixing module realize the mixing and the modulation of signal, produce high-precision frequency signal.It is characterized in that: the FPGA control circuit is made up of FPGA control chip and peripheral circuit thereof; The FPGA control circuit is connected with the configured port of digital frequency synthesizer; The FPGA control circuit links to each other with the operational amplifier reference edge of automatic level control circuit; The FPGA control circuit links to each other with the voltage controlled oscillator tuning end; The FPGA control circuit is mainly accomplished the control of each modular circuit, and signal generator module produces circuit by clock distribution circuit, digital frequency synthesizer (DDS), first frequency mixer (Mixer1), local oscillation signal (LO), switch and pectination spectrum to be formed, and clock distribution circuit produces circuit with digital frequency synthesizer (DDS), first frequency mixer (Mixer1), pectination spectrum and links to each other; Digital frequency synthesizer (DDS) links to each other with clock distribution circuit, first frequency mixer (Mixer1); Local oscillation signal (LO) links to each other with switch, and switch links to each other with quadrature modulation circuit, and the pectination spectrum produces circuit and links to each other with three-mixer (Mixer3); Three frequency mixing module are made up of second frequency mixer (Mixer2), three-mixer (Mixer3), the 4th frequency mixer (Mixer4), first BPF. (BPF1), second BPF. (BPF2), low-pass filter (LPF), automatic level control circuit (ALC), voltage controlled oscillator (VCO), quadrature modulation circuit; Voltage controlled oscillator (VCO) links to each other with three-mixer (Mixer3), the 4th frequency mixer (Mixer4), FPGA control circuit; Three-mixer (Mixer3) links to each other with BPF. (BPF1); First BPF. (BPF1) links to each other with automatic level control circuit (ALC); Automatic level control circuit (ALC) links to each other with second frequency mixer (Mixer2); Second frequency mixer (Mixer2) links to each other with second BPF. (BPF2); Second BPF. (BPF2) links to each other with quadrature modulation circuit; Quadrature modulation circuit links to each other with the 4th frequency mixer (Mixer4), and the 4th frequency mixer (Mixer4) links to each other with low-pass filter (LPF), and local oscillation circuit links to each other with quadrature modulation circuit in three frequency mixing module through switch.The FPGA control circuit is connected with the configured port of digital frequency synthesizer (DDS), carries out the control word configuration, to export required frequency, phase place and amplitude; The FPGA control circuit links to each other with the operational amplifier reference edge of automatic level control circuit (ALC), datum and real-time regulated is provided, with the scope of control circuit output level; The FPGA control circuit links to each other with voltage controlled oscillator (VCO) tip, and VT is provided, and with control voltage controlled oscillator (VCO) output signal frequency, three suitable mixed frequency signals is provided.Described FPGA control circuit is: FPGA control chip, digital analog converter (DAC; Digital Analog Converter) chip and peripheral circuit thereof, peripheral circuit are introduced interface, control signal introducing interface and output interface by power circuit, clock signal and are formed.
Signal generator module is divided into three parts, is respectively clock distribution circuit, pectination spectrum generation circuit and local oscillation signal (LO).The signal output port of clock distribution circuit links to each other with the signal input port of digital frequency synthesizer (DDS), first frequency mixer (Mixer1), pectination spectrum generation circuit respectively; Digital frequency synthesizer (DDS) links to each other with clock distribution circuit signal output port, first frequency mixer (Mixer1); The signal output port of local oscillation signal (LO) links to each other with switch; Switch links to each other with quadrature modulation circuit, and the signal output port that the pectination spectrum produces circuit links to each other with three-mixer (Mixer3).Wherein clock distribution circuit produces the input clock of digital frequency synthesizer (DDS), pectination spectrum generation circuit and local oscillator (LO); The road signal mixing that the signal that digital frequency synthesizer (DDS) produces and clock distribution circuit produce is afterwards as one road input signal of three frequency mixing module; The signal that the pectination spectrum produces the circuit generation links to each other with three-mixer (Mixer3); As one road input signal of three frequency mixing module, local oscillation circuit is sent into the orthogonal modulation module through switch.Described clock distribution circuit is: the 30MHz input signal is connected to the power splitter merit and is divided into two-way; One the tunnel exports the pectination spectrum to produces circuit; One the road to frequency multiplier MPS9600-30M produces the 960MHz signal, is divided into two-way through the power splitter merit then, and one the tunnel exports Direct Digital Frequency Synthesizers (DDS) to; One the road exports two-way 320MHz signal after being connected to clock distribution chip AD9514 three frequency division again; One the tunnel exports FPGA control circuit clock signal input terminal mouth to, and another road exports first frequency mixer (Mixer 1) to, with connect digital frequency synthesizer (DDS) 7 output signal mixings after export second frequency mixer (Mixer 2) to.Described pectination spectrum produces circuit and is: the 30MHz input signal is pectination spectrum signal at interval through exporting 30MHz after input coupling, biasing resistor, diode, output coupling and the power adjustments.Described quadrature modulation circuit is: through input port second BPF. (BPF2) output signal is connected to quadrature power splitter input end; Quadrature power splitter output terminal is connected to the orthogonal modulation chip again; The signal output port of local oscillation signal (LO) also is connected to the orthogonal modulation chip through switch, output after modulating through the orthogonal modulation chip.
Three frequency mixing module by by second, third, the 4th frequency mixer (Mixer2, Mixer3, Mixer4), first, second BPF. (BPF1, BPF2), low-pass filter (LPF), automatic level control circuit (ALC), voltage controlled oscillator (VCO), quadrature modulation circuit form.Voltage controlled oscillator (VCO) links to each other with three-mixer (Mixer3), the 4th frequency mixer (Mixer4), FPGA control circuit; The signal output port of three-mixer (Mixer3) links to each other with the signal input port of first BPF. (BPF1); The signal output port of first BPF. (BPF1) links to each other with the signal input port of automatic level control circuit (ALC); The signal output port of automatic level control circuit (ALC) links to each other with second frequency mixer (Mixer2); The signal output port of second frequency mixer (Mixer2) links to each other with the signal input port of second BPF. (BPF2); The signal output port of second BPF. (BPF2) links to each other with the signal input port of quadrature modulation circuit; The signal output port of quadrature modulation circuit links to each other with the 4th frequency mixer (Mixer4), and the signal output port of the 4th frequency mixer (Mixer4) links to each other with the signal input port of low-pass filter (LPF).Make input signal through after second frequency mixer (Mixer2) and twice mixing of the 4th frequency mixer (Mixer4) in three frequency mixing module, obtain required frequency.The signal merit that voltage controlled oscillator (VCO) produces is divided into two-way; One the tunnel be that 1275MHz first BPF. (BPF1) links to each other after pectination spectrum produces the signal mixing that circuit produces with centre frequency; Carry out sending into first frequency mixer (Mixer1) output signal mixing in second frequency mixer (Mixer 2) and the signal generating circuit again after the power control through automatic level control circuit (ALC) after the filtering; Second frequency mixer (Mixer2) is that 915MHz second BPF. (BPF2) links to each other with centre frequency; Output links to each other with quadrature modulation circuit after the filtering, modulates with local oscillation signal (LO) signal.When nuclear magnetic resonance spectrometer was in emission state, local oscillation signal (LO) signal was got 7.5MHz and is sent into quadrature modulation circuit; When being in accepting state, local oscillation signal (LO) is got 30MHz and is sent into quadrature modulation circuit.The signal output port of quadrature modulation circuit links to each other with the 4th frequency mixer (Mixer4), exports signal mixing with a road of voltage controlled oscillator (VCO) and gets required frequency.Last the 4th frequency mixer (Mixer4) output is connected to low-pass filter (LPF) and carries out exporting behind the LPF.
The present invention adopts FPGA as the control core, can realize the quick configuration of DDS chip frequency, phase place and amplitude control word and the precision control of ALC datum and VCO VT.(PTS) compares with frequency synthesizer, and be not only easy to operate, and simple in structure, extensibility is strong.
The present invention has adopted the DDS device with digital quadrature modulation function, alternative frequency synthesizer (PTS) internal standard frequency synthesis module and high frequency resolution generation module.DDS has point-device frequency output characteristics, can guarantee the resolution and the handoff response time of output frequency, and modulation function makes this DDS to modulate the signal that produces, and realizes the soft pulse of different shape.Change quadrature modulator local oscillator incoming frequency, promptly can be used as the local oscillator of receiver, the economize on hardware cost.Specifically be embodied as: local oscillation signal (LO) is connected to quadrature modulation circuit through switch.When being in emission state, local oscillation signal (LO) is got 7.5MHz and is sent into quadrature modulation circuit; When being in accepting state, local oscillation signal (LO) is got 30MHz and is sent into quadrature modulation circuit.Need not to change the DDS output frequency like this, as long as through switching manipulation, just can accomplish the switching between transmitter and receiver local oscillator, easy and simple to handle, the response time is short, and simple in structure, cost is low.
The present invention has improved the radio frequency (RF of existing NMR system radiating portion; Radio Frequency) orthogonal modulation module through launching in the method for three frequency mixing module introducing local oscillation signal and receiving the synthetic of signal, realizes than the orthogonal modulation in the narrow-band scope; To be divided into device than wideband orthogonal in the alternative existing RF orthogonal modulation module of the quadrature power splitter of narrow-band scope; Improved spurious signal and suppressed ability, simplified structure reduces cost.
Adopt the method for three mixing to realize frequency synthesis among the present invention.One of design object of frequency synthesis is to utilize standard module repetitive construct frequency, and three mixing methods can satisfy this target.Only need to change the VCO output frequency, utilize three frequency mixing module, in this invention, can make output frequency with the 30MHz step change, the frequency adjustment of littler stepping is then realized by DDS.And three the mixing method have the function that offsets of drift, make the output signal that good phase noise characteristic arranged.
Through demonstration, reference frequency output of the present invention is 0.1MHz～600MHz, has expanded the frequency output area of existing scheme greatly; Frequency resolution of the present invention reaches 0.1Hz, and high-precision frequency control can be provided; Phase resolution of the present invention reaches 0.022 degree, and high-precision phase control can be provided; Frequency switching time of the present invention is low to moderate 100ns, can realize that frequency switches fast.
The present invention compared with prior art, effect has the following advantages:
1) compare with frequency synthesizer (PTS), adopt FPGA to realize Digital Control, structure is simpler, more convenient operation.
2) compare with frequency synthesizer (PTS), adopt DDS to substitute PTS precise frequency synthesis unit, make circuit structure simpler, frequency synthesis is easier, and precision is higher, and change of frequency is more flexible.
3) adopt the DDS that is with modulation function, expanded the signal source function, make it with better function, use more extensive.
4) local oscillation circuit and quadrature modulation circuit have been added; Under the prerequisite that does not change the DDS output frequency, make the transmitter and receiver local oscillator of signal source timesharing as nuclear magnetic resonance spectrometer, expanded the usable range of signal source; And simple to operate, frequency is switched fast.
5) compare with existing NMR system radiating portion, do not use the wideband orthogonal power splitter, do not carry out the analog quadrature modulation of wide frequency ranges, improved spurious signal and suppressed ability, simplified structure has reduced cost.
6) adopt three frequency mixing methods to realize the synthetic of frequency, offset the frequency drift that VCO produces, obtain better signal phase noisiness.
7) realized the integrated design of transmitter in frequency synthesizer (PTS) and the nuclear magnetic resonance spectrometer, made designs simplification, with low cost.
8) in the FPGA control circuit, embed the output stability that corresponding control algolithm can improve automatic level control circuit, the control output power only fluctuates in very little scope.
9) total system all can be passed through operator's operated from a distance, has realized the target of remote digital control.
Description of drawings
Fig. 1 is a kind of radio frequency signal generating device structural representation
Wherein: (1) FPGA control circuit: EP3C40; (2) signal generator module: produce circuit by clock distribution circuit, digital frequency synthesizer, first frequency mixer, local oscillation signal, switch and pectination spectrum and form; (3) three frequency mixing module are made up of second frequency mixer, three-mixer, the 4th frequency mixer, first BPF., second BPF., low-pass filter, automatic level control circuit, voltage controlled oscillator, quadrature modulation circuit; (4) clock distribution circuit: the 30MHz signal inputs to the power splitter merit and is divided into two-way; One the tunnel directly exports; One road to frequency multiplier MPS9600-30M (rich prestige integrated circuit company limited) produces the 960MHz signal; Be divided into two-way through the power splitter merit then, the one tunnel directly exports, and one the road is connected to output again behind clock distribution chip AD9514 (ADI company) frequency division; (5) switch; (6) the pectination spectrum produces circuit: the 30MHz input signal is pectination spectrum signal (7) Direct Digital Frequency Synthesizers (DDS) at interval: AD9957 (ADI company) through exporting 30MHz after input coupling, biasing resistor, diode, the output coupling, and (8) local oscillation signal (LO): the 30MHz signal inputs to the power splitter merit and is divided into two-way, and one the tunnel directly exports; One the road is connected to output again behind clock distribution chip AD9514 (ADI company) frequency division; (9) voltage controlled oscillator (VCO): ROS-1445+ (Mini-Circuits), frequency mixer (Mixer3) ADE-25MH (Mini-Circuits) and frequency mixer (Mixer4) ADE-11X (Mini-Circuits) automatic level control circuit (ALC) are sent in VCO output respectively after power splitter is divided into to two-way: the electricity that input signal is formed through four pin diodes is connected to amplifier GALI-5 (Mini-Circuits) output after transferring controlled attenuator circuit, and output place meets level detection chip AD8361 (ADI company); Detect output and be connected to operational amplifier OP177 (ADI company); Operational amplifier output is fed back to the diode electrically-tuned attenuator circuit of pin with the control decay, (10) automatic level control circuit (ALC), (11) quadrature modulation circuit: input signal is connected to the quadrature power splitter; And then be connected to the orthogonal modulation chip and local oscillation signal (LO) signal is modulated; (12) first frequency mixer Mixer1:ADE-11X (Mini-Circuits), (13) second frequency mixer Mixer2:ADE-25MH (Mini-Circuits), (14) three-mixer Mixer3:ADE-25MH (Mini-Circuits); (15) the 4th frequency mixer Mixer4:ADE-11X (Mini-Circuits); (16) the-BPF. BPF1:5CX15-1275/U6 (rich subelectron science and technology), (17) second BPF. BPF2:SF2053E (RF Monolithics), (18) low-pass filter LPF:LFCN-575 (Mini-Circuits).
Embodiment
Embodiment 1:
1 couple of the present invention does further detailed description below in conjunction with accompanying drawing:
Can know according to Fig. 1: the nuclear magnetic resonance spectrometer radio-frequency signal source mainly is made up of FPGA control circuit 1, signal generator module 2,3 three parts of three frequency mixing module.Wherein FPGA control circuit 1 is realized the quick configuration of Direct Digital Frequency Synthesizers (DDS) 7, the reference input adjusting of automatic level control circuit (ALC) 10 and the VT control of voltage controlled oscillator (VCO) 9; Signal generator module 2 provides the external timing signal of FPGA; And provide three frequency mixing module each input signal, produce signals like local oscillation signal (LO), pectination spectrum signal and by Direct Digital Frequency Synthesizers (DDS) 7 and clock distribution circuit 4 through first frequency mixer (Mixer 1) mixing; Three frequency mixing module 3 realize the mixing and the modulation of signal, produce high-precision frequency signal.
FPGA control circuit 1 mainly comprises FPGA and DAC.FPGA control circuit 1 links to each other with the signal output port of the reference voltage input terminal of the signal input end mouth of Direct Digital Frequency Synthesizers (DDS) 7, automatic level control circuit (ALC) 10, voltage controlled oscillator (VCO) 9 VT input ends, clock distribution circuit 4 respectively as the control core; Be used to receive external timing signal, and accomplish the control of each modular circuit.Wherein clock is provided by clock distribution circuit 4; Behind the FPGA control circuit 1 receive clock signal; Produce one group of control signal and carry out the configuration operation of Direct Digital Frequency Synthesizers (DDS) 7; Produce another group signal simultaneously and drive DAC, and DAC output is connected to the operational amplifier OP177 reference input of automatic level control circuit (ALC) 10 and the VT input end of voltage controlled oscillator (VCO) 9, to accomplish automatic electric-level control and voltage controlled oscillator output.Described FPGA control circuit 1 is: FPGA control chip, digital analog converter (DAC; Digital Analog Converter) chip and peripheral circuit thereof, peripheral circuit are introduced interface, control signal introducing interface and output interface by power circuit, clock signal and are formed.Its annexation is: power circuit, clock signal are introduced interface, control signal is introduced interface and linked to each other with the FPGA control chip, and the FPGA control chip links to each other with digital analog converter and output interface, and digital analog converter links to each other with output interface.
Three frequency mixing module 3 mainly are made up of second frequency mixer (Mixer2) 13, three-mixer (Mixer3) 14, the 4th frequency mixer (Mixer4) 15, first BPF. (BPF1) 16, second BPF. (BPF2) 17, low-pass filter (LPF) 18, automatic level control circuit (ALC) 10, voltage controlled oscillator (VCO) 9 and quadrature modulation circuit 11.FPGA control circuit 1 is through the output of adjustment VT control voltage controlled oscillator (VCO) 9 signals; Its output is divided into two-way through the power splitter merit; One the tunnel delivers to three-mixer (Mixer3) 14 carries out mixing with the pectination spectrum signal that the pectination spectrum produces circuit 6 generations; Signal after the mixing is delivered to first BPF. (BPF1) 16; The centre frequency of first BPF. (BPF1) 16 is 1275MHz, and through first BPF. (BPF1), 16 frequency-selectings, the effect of frequency-selecting is to choose suitable voltage controlled oscillator (VCO) 9 output signal frequencies.Because it is identical that the power of each signal of pectination spectrum can't be adjusted to, and voltage controlled oscillator (VCO) 9 output signal powers also descend with the rising of frequency, so the 1275MHz signal power that obtains behind the mixing and filtering is also unstable.Filtered signal is delivered to automatic level control circuit (ALC) 10 input ports; Through adjustment automatic level control circuit (ALC) 10 reference voltage to confirm the value of output level; Output level is detected the back negative feedback to the diode electrically-tuned attenuator circuit of pin, the power of signal is only fluctuateed in very little scope.Second frequency mixer (Mixer2) 13 is delivered in the output of automatic level control circuit (ALC) 10; With the 12 output signal mixings of first frequency mixer (Mixer1) in the signal generating circuit; Second frequency mixer (Mixer2) 13 links to each other with second BPF. (BPF2) 17; The centre frequency of second BPF. (BPF2) 17 is 915MHz, chooses the LSB of mixed frequency signal through it.Second BPF. (BPF2), 17 outputs link to each other with quadrature modulation circuit 11, modulate with local oscillation signal (LO) 8.When the probe of nuclear magnetic resonance spectrometer was in emission state, the output port of local oscillation signal (LO) 8 was got 7.5MHz and is sent into quadrature modulation circuit 11; When the probe of nuclear magnetic resonance spectrometer was in accepting state, the output port of local oscillation signal (LO) 8 was got 30MHz and is sent into quadrature modulation circuit 11.Quadrature modulation circuit 11 outputs link to each other with the 4th frequency mixer (Mixer4) 15, export signal mixing with a road of voltage controlled oscillator (VCO) 9 and get required frequency.Last the 4th frequency mixer (Mixer4) 15 outputs are connected to low-pass filter (LPF) 18 and carry out exporting behind the LPF.
The control core of magnetic nuclear resonance radio frequency signal source is a FPGA control circuit 1.According to required output frequency f
0, produce signal f by FPGA control circuit 1 control Direct Digital Frequency Synthesizers (DDS) 7
1, and control voltage controlled oscillator (VCO) 9 produces signal f
2f
1Signal f with clock distribution circuit 4 generations
3After second frequency mixer (Mixer1), 12 mixing, get upper side band, be (f
1+ f
3).And the signal f that voltage controlled oscillator (VCO) 9 produces
2Produce the signal f that circuit 6 produces with the pectination spectrum
CombAfter three-mixer (Mixer3) 14 mixing, select the signal f that frequency is 1275MHz through first BPF. (BPF1), 16 frequency-selectings
1275M, f
1275M, automatic level control circuit (ALC) 10 is connected to second frequency mixer (Mixer2) 13 and signal (f after carrying out the power adjustment
1+ f
3) export second BPF. (BPF2), 17 frequency-selectings to after the mixing and take off sideband, be (f
1275M-(f
1+ f
3)), this signal definition is f
4Signal f
4With local oscillation signal f
LOAfter the quadrature modulation circuit modulation, remove LSB, be (f
4-f
LO).The signal f that last voltage controlled oscillator (VCO) 9 produces
2With signal (f
4-f
LO) through the 4th frequency mixer (Mixer4) 15 mixing, and to select LSB through low-pass filter (LPF) 18 promptly be required frequency, its expression formula is: f
0=f
1+ f
2+ f
3+ f
LO-f
1275M, f wherein
1275MBe f
2With f
CombThe mixing gained, f
1Frequency range be 25MHz～55MHz, f
2Frequency range be 915MHz～1455MHz, f
3Frequency be 360MHz, f
LOFrequency be 7.5MHz or 30MHz, when nuclear magnetic resonance spectrometer is in emission state, f
LOFrequency be 7.5MHz, when nuclear magnetic resonance spectrometer is in accepting state, f
LOFrequency be 30MHz.
Claims (3)
1. radio frequency signal generating device; It is made up of FPGA control circuit (1), signal generator module (2) and three frequency mixing module (3); It is characterized in that: FPGA control circuit (1) is made up of FPGA control chip and peripheral circuit thereof; Signal generator module (2) produces circuit (6) by clock distribution circuit (4), Direct Digital Frequency Synthesizers (7), first frequency mixer (12), local oscillation signal (8), switch (5) with the pectination spectrum and forms; Three frequency mixing module (3) are made up of second frequency mixer (13), three-mixer (14), the 4th frequency mixer (15), first BPF. (16), second BPF. (17), low-pass filter (18), automatic level control circuit (10), voltage controlled oscillator (9), quadrature modulation circuit (11); FPGA control circuit (1) is connected with the configured port of Direct Digital Frequency Synthesizers (7); FPGA control circuit (1) links to each other with the operational amplifier reference edge of automatic level control circuit (10); FPGA control circuit (1) links to each other with voltage controlled oscillator (9) tip; Clock distribution circuit (4) produces circuit (6) with Direct Digital Frequency Synthesizers (7), first frequency mixer (12), pectination spectrum and links to each other, and Direct Digital Frequency Synthesizers (7) links to each other with clock distribution circuit (4), first frequency mixer (12), and local oscillation signal (8) links to each other with switch (5); Switch (5) links to each other with quadrature modulation circuit (11), and the pectination spectrum produces circuit (6) and links to each other with three-mixer (14); Voltage controlled oscillator (9) links to each other with three-mixer (14), the 4th frequency mixer (15), FPGA control circuit (1); Three-mixer (14) links to each other with first BPF. (16); First BPF. (16) links to each other with automatic level control circuit (10); Automatic level control circuit (10) links to each other with second frequency mixer (13), and second frequency mixer (13) links to each other with second BPF. (17), and second BPF. (17) links to each other with quadrature modulation circuit (11); Quadrature modulation circuit (11) links to each other with the 4th frequency mixer (15), and the 4th frequency mixer (15) links to each other with low-pass filter (18).
2. a kind of radio frequency signal generating device according to claim 1 is characterized in that: described local oscillation signal (8) links to each other with quadrature modulation circuit (11) in three frequency mixing module (3) through switch (5).
3. a kind of radio frequency signal generating device according to claim 1; It is characterized in that: described peripheral circuit is introduced interface, control signal introducing interface and output interface by power circuit, clock signal and is formed; Power circuit, clock signal are introduced interface, control signal is introduced interface and linked to each other with the FPGA control chip; The FPGA control chip links to each other with digital analog converter and output interface, and digital analog converter links to each other with output interface.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009102728756A CN101726712B (en) | 2009-11-20 | 2009-11-20 | Radio frequency signal generating device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009102728756A CN101726712B (en) | 2009-11-20 | 2009-11-20 | Radio frequency signal generating device |
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| CN102780490B (en) * | 2012-08-14 | 2014-12-10 | 武汉滨湖电子有限责任公司 | DDS (direct digital synthesis) type ultra-wide band frequency-modulated signal generating circuit and method |
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| CN103529431A (en) * | 2013-09-24 | 2014-01-22 | 北京环境特性研究所 | Broadband fast multifunctional signal generation assembly |
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| WO2016023147A1 (en) * | 2014-08-11 | 2016-02-18 | 华为技术有限公司 | Apparatus and method for processing multiband signal |
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| CN104570861A (en) * | 2014-12-23 | 2015-04-29 | 天津光电通信技术有限公司 | FPGA-based radio frequency signal source circuit |
| CN106997033B (en) * | 2016-01-22 | 2019-05-14 | 北京大学 | A kind of multi-channel magnetic resonance RF transmission method and device |
| CN106656050B (en) * | 2016-11-24 | 2023-05-12 | 安徽四创电子股份有限公司 | S-band octave high-performance frequency synthesizer |
| CN110824396A (en) * | 2018-08-10 | 2020-02-21 | 西门子(深圳)磁共振有限公司 | Radio frequency generation system and local coil |
| CN110412491B (en) * | 2019-08-01 | 2021-05-07 | 合肥菲特微电子技术有限公司 | Controller and method for radio frequency emission carrier frequency phase of nuclear magnetic resonance imaging spectrometer |
| CN110531291B (en) * | 2019-08-26 | 2021-09-28 | 中国科学院合肥物质科学研究院 | Topological structure of high-intensity magnetic field condensed nuclear magnetic resonance spectrometer system |
| CN110677169B (en) * | 2019-10-19 | 2021-07-23 | 北京工业大学 | A dual-channel voice signal simultaneous interpretation transceiver |
| CN111965576B (en) * | 2020-07-07 | 2023-05-16 | 无锡鸣石峻致医疗科技有限公司 | Single-port double-frequency coil |
| CN114337853B (en) * | 2022-01-18 | 2024-05-07 | 广东圣大电子有限公司 | Pulse modulation device for simulating Gaussian waveform |
| CN114866039B (en) * | 2022-07-07 | 2022-11-11 | 成都嘉纳海威科技有限责任公司 | Low-power-consumption transmitting multifunctional chip |
| CN115685231B (en) * | 2023-01-04 | 2023-05-16 | 武汉中科锐择光电科技有限公司 | Frequency modulation laser radar system and method for improving coherent detection distance |
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