CN103701459A - Method for generating modulated signal and demodulated local oscillator signals - Google Patents
Method for generating modulated signal and demodulated local oscillator signals Download PDFInfo
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- CN103701459A CN103701459A CN201310560707.3A CN201310560707A CN103701459A CN 103701459 A CN103701459 A CN 103701459A CN 201310560707 A CN201310560707 A CN 201310560707A CN 103701459 A CN103701459 A CN 103701459A
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Abstract
The invention discloses a method for generating modulated signal and demodulated local oscillator signals. Through the method, a sinusoidal signal with fixed frequency is generated and provided to a phase modulator as the modulated signal. The modulation frequency of the modulated signal depends on the length of an optical fiber from the phase modulator to a faraday rotation mirror. Two LO (Local Oscillator) signals are generated by the method, wherein one LO signal is used for demodulating a singled frequency harmonic component of the modulated frequency to obtain sine information of an optical rotation angle; the other one LO signal is used for demodulating a doubled frequency harmonic component of the modulated frequency to obtain cosine information of the optical rotation angle. The method provided by the invention can improve the detection sensitivity and stability, and lay a foundation for realizing magnitude measurement of to-be-tested current by detecting phase difference of polarized light.
Description
Technical field
The present invention relates to the method for the generation of a kind of modulation signal and demodulation local oscillation signal, particularly a kind of all-fiber current transformator is controlled the method for the modulation signal of SLED light source and the generation of demodulation local oscillation signal.
Background technology
With FPGA, control DDS; can realize frequency and amplitude adjusted scope is larger; more accurate; the patent No. is 200910243603.3; name is called " a kind of low-rate spread spectrum communication transmission base band system " and discloses and relate to a kind of low-rate spread spectrum communication transmission base band system; described field programmable gate array for system (FPGA) and Direct Digital Frequency Synthesizers (DDS) realize the low rate spread spectrum transmitting baseband system that parameter can arrange, and specifically comprise: fpga chip, DDS chip and peripheral module; Fpga chip comprises: clock signal generation module; RS-232 serial communication module; Central Control Module; Framing module; Channel coding module; PN code generator module; Numeral formed filter module; With DDS working state control device.DDS chip comprises: phase accumulator module, waveform ROM module, D/A modular converter and low-pass filtering module, for digital-to-analogue conversion and signal modulation; The input/output port of fpga chip is connected with the input port of DDS chip, by data to be modulated input and state control signal to DDS chip, the mode of operation of control DDS chip.
The patent No. is 201310003878.6, name is called " implementation method that the anti-forwarding of radio frequency-modulating fuze is disturbed " and proposes the method that the anti-forwarding of a kind of radio frequency-modulating fuze is disturbed, be intended to a kind ofly can adjust flexibly triangular wave frequency and change fuze function range, and can improve the digitlization jamproof fuze implementation method of the anti-forwarding interference performance of fuse equipment.The present invention is achieved by following technical proposals: in programmable gate array chip FPGA, design a triangular wave generator being formed by triangular wave frequency control word, N position phase accumulator, data cut position processor and triangular wave phase look-up table successively, a BPSK modulator being cross-linked between balanced GOLD code generator and digital to analog converter; After known triangular modulation frequency, in DDS triangular wave generator, adopt the computing formula of triangular wave frequency control word: the triangular wave frequency control word calculating is delivered to N position phase accumulator and add up, cut out the low 18 of data, retain the high 14 of data; Deliver to triangular wave look-up table, complete the phase place of triangular signal to the conversion of amplitude.
Above-mentioned patent all provides modulation signal and produces local oscillation signal to phase-modulator for relating to the DDS scheme realizing based on FPGA, and the implementation of DDS numerical portion and simulation part, and how adjustable in the inner phase place that adopts Logical Design to realize local oscillation signal of FPGA.
Summary of the invention
For above problem, the invention provides a kind of method that DDS scheme realizing based on FPGA provides modulation signal to phase-modulator and produces local oscillation signal.
In order overcoming the above problems, to the invention provides a kind of method that all-fiber current transformator is controlled the modulation signal of SLED light source and the generation of demodulation local oscillation signal, to comprise the following steps:
1. the generation of modulation signal:
By DDS technology, realize the Specifeca tion speeification that needs to determine DDS before frequency synthesis:
The clock frequency of system is made as clk, and the figure place of phase accumulator is N, and frequency control word is M, and the frequency of system output signal is
, frequency resolution is
;
System crystal oscillator frequency passes through at phase-locked loop frequency division of FPGA internal configurations, and fractional frequency signal can be used as the clock signal clk of system, and clk is the trigger source of phase accumulator, address register and wave memorizer; Frequency control word is M position, and the figure place of phase accumulator is N position, the configuration one amount of capacity wave memorizer that is K, and the high L position of intercepting phase accumulator is given and is re-used as sampling address after address register wave memorizer is sampled; Wave memorizer output be parallel digital signal, utilize digital to analog converter to carry out digital-to-analogue conversion to it and obtain current signal, increase one-level operational amplifier after digital to analog converter, current signal is converted to voltage signal; The voltage signal of changing due to digital to analog converter is stair-stepping, after stepped signal, increases one-level low pass filter it is carried out to smoothing processing.
2. the generation of demodulation local oscillation signal:
Signal from harmonic wave phase division is processed thought, processes solution timing need to use two-way local oscillation signal (LO:Local Oscillator) at the signal of receiving terminal.One road LO is used for a frequency multiplication harmonic component of demodulation modulating frequency to obtain the sinusoidal information of angle of rotation, and another road LO is used for two frequency multiplication harmonic components of demodulation modulating frequency to obtain optically-active cosine of an angle information.
In coherent demodulation theory, require the phase alignment of LO and modulated signal, if there is phase difference between them
, in the primary signal demodulating, have
cosine value product term, when
time, this product term value is 1.Through polarization maintaining optical fibre transmission and Faraday effect, there is phase difference between the signal receiving and modulation signal in light signal, therefore, require the adjustable DDS signal source of phase place of system after phase-modulator.
The signal receiving and the phase difference between modulation signal are unknown to be measured, can not in systems soft ware, set this phase difference in advance, the solution of the present invention is to observe two paths of signals by oscilloscope, the phase place of adjusting LO by button on system hardware is to phase alignment, by this value of software records, in the phase accumulator of DDS, be made as initial phase again.Because light path system is after design completes, this phase difference is changeless, so this scheme is feasible.
Useful effect:
The sinusoidal signal that produces Liao Yi road fixed frequency offers phase-modulator as modulation signal.By phase-modulator, the fiber lengths to Faraday mirror determines the modulating frequency of modulation signal.
Produced two-way demodulation local oscillation signal (LO:Local Oscillator).One road LO is used for a frequency multiplication harmonic component of demodulation modulating frequency to obtain the sinusoidal information of angle of rotation, and another road LO is used for two frequency multiplication harmonic components of demodulation modulating frequency to obtain optically-active cosine of an angle information.
Improved the sensitivity and the stability that detect, for obtain the big or small realization of electric current to be measured by detecting the phase difference of polarised light, laid a good foundation.
Accompanying drawing explanation
Fig. 1 is DDS module logical architecture;
Fig. 2 is the FPGA logical architecture figure that the adjustable DDS of phase place realizes.
Embodiment
Below in conjunction with accompanying drawing, the present invention is described in further details.
As shown in Figures 1 and 2: the method for the generation of a kind of modulation signal and demodulation local oscillation signal, its concrete grammar is following steps:
1. the generation of modulation signal:
By DDS technology, realize the Specifeca tion speeification that needs to determine DDS before frequency synthesis:
The clock frequency of system is made as
clk, the figure place of phase accumulator is N, and frequency control word is M, and the frequency of system output signal is
, frequency resolution is
System crystal oscillator frequency is 50MHz, can be by being downconverted to 12MHz at PLL of FPGA internal configurations, and the frequency stability of using PLL frequency division to obtain is high, phase stabilization.The 12MHz signal that frequency division obtains can be used as the clock signal of system, as the trigger source of phase accumulator, address register and wave memorizer.Frequency control word is 30, and the figure place of phase accumulator is 32, and the configuration one amount of capacity wave memorizer that is 2KB is given and is re-used as sampling address after address register wave memorizer is sampled for high 11 of intercepting phase accumulator.Theoretical reference frequency output is like this 0.003Hz～3MHz, and stepping is 0.003Hz.DDS module logical architecture is now as shown in Fig. 1:
What wave memorizer was exported is parallel digital quantity, need to it, carry out digital-to-analogue conversion with digital to analog converter (DAC:Digital to Analog Converter) and obtain analog quantity.The result of DAC conversion is current signal, increases one-level operational amplifier after DAC to realize I-V conversion, is converted into voltage signal.Due to the retention performance of DAC, the voltage of conversion is stair-stepping, need to after stepped signal, increase one-level low pass filter (LPF:Low Pass Filter) it is carried out to smoothing processing.Output modulation signal sine wave as shown in Figure 2, frequency 900KHz.
2. the generation of demodulation local oscillation signal:
Signal from harmonic wave phase division is processed thought, processes solution timing need to use two-way local oscillation signal (LO:Local Oscillator) at the signal of receiving terminal.One road local oscillation signal is used for a frequency multiplication harmonic component of demodulation modulating frequency to obtain the sinusoidal information of angle of rotation, and another road local oscillation signal is used for two frequency multiplication harmonic components of demodulation modulating frequency to obtain optically-active cosine of an angle information.
In coherent demodulation theory, require the phase alignment of local oscillation signal and modulated signal, if there is phase difference between them, meeting in the primary signal demodulating
some cosine value product terms, when
=0 o'clock, this product term value was 1.Through polarization maintaining optical fibre transmission and Faraday effect, there is phase difference between the signal receiving and modulation signal in light signal, therefore, require the adjustable DDS signal source of phase place of system after phase-modulator.
The signal receiving and the phase difference between modulation signal are unknown to be measured, can not in systems soft ware, set this phase difference in advance, the scheme adopting is herein to observe two paths of signals by oscilloscope, the phase place of adjusting local oscillation signal by button on system hardware is to phase alignment, by this value of software records, in the phase accumulator of DDS, be made as initial phase again.Because light path system is after design completes, this phase difference is changeless, so this scheme is feasible.
The fpga logic Organization Chart that the DDS that phase place is adjustable realizes improves to some extent on the basis of Fig. 1, has introduced adjustable initial phase module, as shown in Figure 2 on address register.
The foregoing is only the preferred embodiments of the present invention, be not restricted to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., within all should being included in claim scope of the present invention.
Claims (7)
1. a method for the generation of modulation signal and demodulation local oscillation signal, is characterized in that: comprise the following steps:
1. the generation of modulation signal:
By DDS technology, realize the Specifeca tion speeification that needs to determine DDS before frequency synthesis:
The clock frequency of system is made as clk, and the figure place of phase accumulator is N, and frequency control word is M, and the frequency of system output signal is
, frequency resolution is
;
System crystal oscillator frequency passes through at phase-locked loop frequency division of FPGA internal configurations, and fractional frequency signal can be used as the clock signal clk of system, and clk is the trigger source of phase accumulator, address register and wave memorizer; Frequency control word is M position, and the figure place of phase accumulator is N position, the configuration one amount of capacity wave memorizer that is K, and the high L position of intercepting phase accumulator is given and is re-used as sampling address after address register wave memorizer is sampled; Wave memorizer output be parallel digital signal, utilize digital to analog converter to carry out digital-to-analogue conversion to it and obtain current signal, increase one-level operational amplifier after digital to analog converter, current signal is converted to voltage signal; The voltage signal of changing due to digital to analog converter is stair-stepping, after stepped signal, increases one-level low pass filter it is carried out to smoothing processing.
2. the 2. generation of demodulation local oscillation signal:
At the signal of receiving terminal, process solution timing and need to use two-way local oscillation signal (LO:Local Oscillator).
3.Yi road LO is used for a frequency multiplication harmonic component of demodulation modulating frequency to obtain the sinusoidal information of angle of rotation, and another road LO is used for two frequency multiplication harmonic components of demodulation modulating frequency to obtain optically-active cosine of an angle information.
4. in coherent demodulation theory, require the phase alignment of LO and modulated signal, if there is phase difference between them
, in the primary signal demodulating, have
cosine value product term, when
time, this product term value is 1.
5. through polarization maintaining optical fibre transmission and Faraday effect after phase-modulator, there is phase difference between the signal receiving and modulation signal in light signal, therefore, requires the adjustable DDS signal source of phase place of system.
6. the method for the generation of a kind of modulation signal according to claim 1 and demodulation local oscillation signal, it is characterized in that: the solution of the present invention is to observe two paths of signals by oscilloscope, the phase place of adjusting LO by button on system hardware is to phase alignment, by this value of software records, in the phase accumulator of DDS, be made as initial phase again.
7. the method for the generation of a kind of modulation signal according to claim 2 and demodulation local oscillation signal, is characterized in that: described light path system is after design completes, and this phase difference is to immobilize.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104483554A (en) * | 2014-12-31 | 2015-04-01 | 思澜科技（成都）有限公司 | Digital phase demodulating method and system for bioelectricity impedance measurement |
| CN106940394A (en) * | 2017-04-24 | 2017-07-11 | 南京南瑞继保电气有限公司 | It is a kind of to realize the method that optical current mutual inductor is measured at a high speed |
| CN109426176A (en) * | 2017-08-22 | 2019-03-05 | 中国计量科学研究院 | A kind of isolation of multichannel and the synchronous sine wave generating system and its method of clock |
| CN115060659A (en) * | 2022-08-18 | 2022-09-16 | 天津大学 | Optical rotation angle measuring method based on proportional method and rapid digital phase-locked demodulation algorithm |
Citations (1)
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| CN202330519U (en) * | 2011-08-10 | 2012-07-11 | 武汉烽火富华电气有限责任公司 | Optical current mutual inductor for magneto-optic glass using interference close-loop detection |
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2013
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Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN202330519U (en) * | 2011-08-10 | 2012-07-11 | 武汉烽火富华电气有限责任公司 | Optical current mutual inductor for magneto-optic glass using interference close-loop detection |
Non-Patent Citations (1)
| Title |
|---|
| 牟渊: "全光纤电流互感器信号处理技术研究", 《中国优秀硕士学位论文全文数据库 工程科技Ⅱ辑》, no. 7, 15 July 2013 (2013-07-15), pages 042 - 342 * |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104483554A (en) * | 2014-12-31 | 2015-04-01 | 思澜科技（成都）有限公司 | Digital phase demodulating method and system for bioelectricity impedance measurement |
| CN104483554B (en) * | 2014-12-31 | 2023-07-04 | 思澜科技（成都）有限公司 | Digital phase demodulation method and system for bioelectrical impedance measurement |
| CN106940394A (en) * | 2017-04-24 | 2017-07-11 | 南京南瑞继保电气有限公司 | It is a kind of to realize the method that optical current mutual inductor is measured at a high speed |
| CN109426176A (en) * | 2017-08-22 | 2019-03-05 | 中国计量科学研究院 | A kind of isolation of multichannel and the synchronous sine wave generating system and its method of clock |
| CN115060659A (en) * | 2022-08-18 | 2022-09-16 | 天津大学 | Optical rotation angle measuring method based on proportional method and rapid digital phase-locked demodulation algorithm |
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Application publication date: 20140402 |