CN107688166A

CN107688166A - A kind of real-time production method of Arbitrary distribution WBFM noise based on FPGA

Info

Publication number: CN107688166A
Application number: CN201710621843.7A
Authority: CN
Inventors: 奚俊; 李俊
Original assignee: 724th Research Institute of CSIC
Current assignee: 724th Research Institute of CSIC
Priority date: 2017-07-27
Filing date: 2017-07-27
Publication date: 2018-02-13

Abstract

The present invention relates to a kind of real-time production method of Arbitrary distribution WBFM noise based on FPGA.This method builds Arbitrary distribution randomizer, be i.e. the distributed density curves sampled value to prestore in the ROM according to built in FPGA, equally distributed M sequence carried out than small selection, to obtain the random number for meeting distribution first in FPGA；Secondly, using the method for Linear Mapping, by the random number Linear Mapping of acquisition to FM noise bandwidth, the random frequency for meeting distribution is obtained；Finally, using direct digital frequency synthesis technology, the random frequency that upper step obtains is converted into FM noise.The real-time production method of WBFM noise of the present invention, with real-time is high, resource occupation is small, produces the characteristics of grass is wide, design bandwidth 600MHz, spectral density is the FM noise of normal distribution, data valid bit number 16, during system clock 250MHz, FPGA block ram resource consumptions are less than 256KB, the FM noise formation time is less than 1us, the generation available for radar interference simulator FM noise.

Description

A kind of real-time production method of Arbitrary distribution WBFM noise based on FPGA

Technical field

The invention belongs to data signal generation technology.

Background technology

FM noise is the main implementation of radar interference simulator pressing type noise, is widely used in radar chaff In.In radar interference simulator, pressing type noise jamming has a variety of different jamming signal types；The noise frequency of disturbance pattern Spectrum density need to match different distribution curves, can just obtain optimal interference effect.For example, realizing arrowband spot jamming, adjust Noise spectrum density processed can reach optimum jamming effect when being and being just distributed very much；When implementing broadband acoustical interference, being uniformly distributed to make Energy is more average on frequency spectrum, reaches more preferable interference effect；Therefore, FM noise need to have a variety of spectral densities to adapt to Disturbance pattern.On the other hand, with radar frequency agile technology extensive use, radar, can be by quickly cutting on frequency domain Frequency, avoid disturbed frequency band；Effectively to disturb radar, it is desirable to suppress noise can according to radar beam frequency change and Quick change, that is, possess compared with high real-time.Producing, there is high real-time, strong randomness and spectral density to obey any given point The FM noise of cloth is with a wide range of applications.

In radar interference simulator technical field, the existing implementation of FM noise is mainly：1. software mode is used, In the FM noise that computer generation is accordingly distributed, by high speed data lines, digital-to-analogue conversion device is transferred to, realizes Arbitrary distribution FM noise produces；The advantage of which is：Computer has powerful disposal ability, and the frequency modulation that can produce Arbitrary distribution is made an uproar Sound；But transmission rate is limited to, its real-time is not strong.2.ROM storage modes, the pseudo-random signal for obeying given distribution is stored In onboard ROM, by reading data in real-time, it is mixed through digital-to-analogue conversion, and with simulation local oscillator, realizes Arbitrary distribution FM noise Produce；The advantage of which is：It is real-time；But ROM size is limited to, typically prestore noise spectrum density topological classes It is few, and need to be complicated with simulation local oscillator mixing, circuit.

The present invention proposes that a kind of logical construction is simple, and resource occupation is few, and real-time is high, directly by PLD The FM noise production method independently realized.

The content of the invention

The purpose of the present invention is：A kind of real-time production method of Arbitrary distribution WBFM noise based on FPGA is provided.

Realize that technical solution of the invention is：In three steps, the first step, in FPGA, construction is any for this programme Distribution random numbers generator, its function are：M sequence is chosen, obtains the random number for meeting given distribution, specific method is such as Under：Uniform sampling in given distributed density curves, sample point are stored in onboard ROM；It is more according to M sequence basis in FPGA Item formula, obtains two groups of equally distributed M sequences；One group of address as ROM, address ROM；Another group corresponding with ROM addresses Output valve compares, only when random number is less than ROM readouts, current ROM addresses is defeated as the random number for meeting given distribution Go out；Second step, the random number for meeting given distribution are mapped in FM noise bandwidth, to obtain the random frequency for meeting given distribution Rate, specific side are as follows：The random number B for meeting given distribution that will have been obtained, carries out linear transformation so that random number by formula 1 Change be limited to all the time in noise bandwidth, so as to obtain meeting the random frequency of given distribution；3rd step, previous step is obtained Random frequency, as DDS incoming frequencies, you can directly synthesize FM noise.

Compared with prior art, its remarkable advantage is the present invention：For big data quantity transmission bottleneck existing for software approach The problem of causing real-time not high, all processing directly produces FM noise of the invention by PLD, improves Real-time；For ROM memory-types, storage data quantity is big, and randomness is not strong, and the problem of Digital Analog Hybrid Circuits complexity, this hair Bright FM noise uses：1. the sample point of a small amount of given distributed density curves is stored in onboard ROM；2. meet given distribution Random number is screened to obtain by M sequence by equally distributed random number through thresholding；3. the random frequency of zoop is given by meeting The random number of distribution, which is mapped in the bandwidth range of zoop, to be obtained；Meet given point 4. directly synthesizing finally by DDS The frequency-shift keying noise of cloth；This method, storage data quantity is few, can store the sample point of a variety of distributions simultaneously；Zoop produces Realized completely by FPGA internal logics, improve circuit complexity.

Hardware platform of the invention based on FPGA, is programmed using VHDL language, actual applied to engineering.

Brief description of the drawings

Fig. 1 is the real-time production method flow chart of Arbitrary distribution WBFM noise of the present invention.

Fig. 2 is normal distribution FM noise spectral density curve map of the present invention.

Fig. 3 is normal distribution FM noise spectrogram of the present invention.

Embodiment

As shown in figure 1, specific implementation method of the present invention is：

1. m sample point of uniform sampling in given distributed density curves, is stored in onboard ROM；

Inside 2.FPGA, two groups of M sequences M1, M2, wherein M1 number of bits and sample are produced according to M sequence primitive polynomial This number of bits is identical, and M2 number of bits is identical with ROM addresses number of bits；Using M2 as address, addressing ROM is obtained To value A, if A>M1, then M2 is exported, is otherwise given up, so as to obtain meeting the random number B of given distribution；

3. realize the mapping of random number and random frequency：According to formulaWill be each random in B Number is mapped in the bandwidth range of zoop, obtains random frequency；

4. it is last, by the random frequency of acquisition, DDS IP kernel is inputted, spectral density is obtained and meets any given distribution tune Frequency noise.

Technical scheme of the present invention has the characteristics of real-time is high, resource occupation is small, and design bandwidth 100MHz frequency spectrums are close Spend the FM noise for normal distribution, data valid bit number 16, during system clock 250MHz, FPGA block ram resources Consumption is less than 256KB, and the FM noise formation time is less than 1us, FM noise spectral density curve such as Fig. 2, FM noise frequency spectrum Such as Fig. 3, meet the requirement of most of radar interference simulator FM noise designs.

Claims

A kind of 1. real-time production method of Arbitrary distribution WBFM noise based on FPGA, it is characterised in that：In FPGA In device FPGA, Arbitrary distribution randomizer is built, i.e. the distributed density curves sampling to be prestored in the ROM according to built in FPGA Value, equally distributed M sequence is carried out than small selection, to obtain the random number for meeting given distribution；Secondly, Linear Mapping is utilized Method, by random number Linear Mapping to the FM noise bandwidth for meeting given distribution, obtain the random frequency for meeting given distribution Rate；Finally, using direct digital frequency synthesis technology, the random frequency that upper step obtains is converted into FM noise, produces frequency modulation Noise.
2. a kind of real-time production method of Arbitrary distribution WBFM noise based on FPGA according to claim 1, it is special Sign is：Described to construct Arbitrary distribution randomizer in FPGA, specific method is as follows：In given distributed density curves Uniform sampling, sample point are stored in onboard ROM；In FPGA, according to M sequence primitive polynomial, obtain two groups and be uniformly distributed M sequence；One group of address as ROM, address ROM；Another group compared with output valve corresponding to ROM addresses, is only worked as random number During less than ROM output valves, exported current ROM addresses as the random number for meeting given distribution.
3. a kind of real-time production method of Arbitrary distribution WBFM noise based on FPGA according to claim 1, it is special Sign is：Using the method for Linear Mapping, the random number for meeting distribution is mapped in FM noise bandwidth, acquisition meets distribution Random frequency, specific side is as follows：The random number B for meeting given distribution that will have been obtained, by formula Carry out linear transformation so that the change of random number is limited in noise bandwidth all the time, so as to obtain meeting the random of given distribution Frequency, n is B number of bits in formula, and fout is the random frequency of output, and BW be frequency-shift keying noise bandwidth, and f1 is counts Word FM noise lowest frequency points.