CN105486920A - Narrow pulse frequency measurement method based on digital channelization technology - Google Patents

Abstract

The invention provides a narrow pulse frequency measurement method based on digital channelization technology, and belongs to the technical field of time frequency measurement. The method mainly comprises the following steps: carrying out high-speed sampling on pulse signals, the pulse width of which is relatively narrow, and analyzing high-speed digital real signals into multi-channel multi-band frequency low-speed digital complex signals through the channelization technology; calculating instantaneous phase and instantaneous amplitude of the multi-channel low-speed digital complex signals through a Cordic algorithm; obtaining instantaneous frequency by utilizing the specific value of phase difference and time; and carrying out multi-point cumulative average on the selected channel instantaneous frequency values to obtain an accurate frequency measurement result. The frequency measurement method can carry out quick and accurate frequency measurement on broadband and narrow pulse width intermediate frequency signals, can output frequency measurement result within 300ns, and has the advantages of large input bandwidth, high frequency measurement precision and wide signal dynamic range and the like.

Description

A kind of burst pulse frequency measurement method based on digital channelizing

Technical field

The present invention relates to a kind of burst pulse frequency measurement method based on digital channelizing, belong to time and frequency measurement technical field.

Background technology

Instantaneous Frequency Measurement is one of the basis realizing radar signal and signal of communication analysis, identification and demodulation; Also be the gordian technique of microwave signal source, it can carry out Quick Measurement to frequency agility signal, directs into suitable intermediate frequency and carries out subsequent treatment again.Instantaneous frequency measurement technology mainly comprises simulation Technology of Frequency Measurement by Using and digital Frequency Measuring technology; Simulation Technology of Frequency Measurement by Using comprises the method for the method based on step-by-step counting timing measured frequency and the phase differential measured frequency based on delay line.Method gordian technique based on step-by-step counting frequency measurement is the Measurement accuracy to the time, the number of pulse is recorded within the set time, calculate the cycle of signal thus realize frequency measurement, this method can reach very high time difference method by the method for temporal interpolation, thus frequency-measurement accuracy is also higher, but it is higher to the amplitude requirement of signal, and dynamic range is less, frequency-measurement accuracy for narrow spaces signal is poor, is not suitable for the frequency measurement of narrow pulse signal.Based on the method for the phase differential measured frequency of delay line, it is very wide that its frequency measurement bandwidth can be done, but its frequency-measurement accuracy is poor.

Summary of the invention

The technical problem to be solved in the present invention is to provide a kind of burst pulse frequency measurement method based on digital channelizing, can carry out frequency measurement fast and accurately, can export frequency measurement result in 300ns to the intermediate-freuqncy signal of large bandwidth, narrow spaces.

The technical scheme that the present invention solves the problems of the technologies described above employing is:

A. paired pulses carries out high-speed sampling;

B. digital channelizing process is carried out to high-speed sampling signal, resolve to multi-path low speed complex signal;

C. utilize Cordic algorithm to carry out instantaneous amplitude and instantaneous phase calculating to the complex signal of each channel, principle formula is as shown in formula (1):

α _i＝tan ^-1(2 ^-i)

d _i＝sign(z ⁱ)

x _i+1＝x _i+d _i×2 ^-i×y _i

y _i+1＝y _i+d _i×2 ^-i×x _i(1)；

D. phase differential measured frequency is utilized, shown in the relation formula (2) of phase place and frequency:

Δθ(i)＝θ(n+i)-θ(n)＝2πfit _s(2)

So instantaneous frequency is exactly:

$f=\frac{\mathrm{\Δ}\mathrm{\θ}\left(i\right)}{2{\mathrm{\πit}}_s}---\left(3\right),$

Wherein (x _i, y _i) be input vector, (x _i+1, y _i+1) be output vector, θ is instantaneous phase, α _ieach angle rotated, d _ithe direction that each iteration rotates, t _sfor the sampling period, f is by measured frequency.

Also step e is comprised after steps d,

E. improve frequency-measurement accuracy by repeatedly calculating to be averaged, computing formula is as follows:

Δθ(1)＝θ(2)-θ(1)

Δθ(2)＝θ(3)-θ(2)

Δθ(3)＝θ(4)-θ(3)

…

Δθ(n-1)＝θ(n)-θ(n-1)(4)

Then, $f=\frac{1}{n-1}\underset{i=1}{\overset{n-1}{\Σ}}\frac{\mathrm{\Δ}\mathrm{\θ}\left(i\right)}{2{\mathrm{\πit}}_s}---\left(5\right).$

The present invention's beneficial effect is compared with prior art:

Along with the development of large scale integrated circuit and high-speed ADC, the application of digital Frequency Measuring technology is more and more extensive, the present invention adopts the method stable performance of digital technology frequency measurement, and bandwidth improves constantly along with the sampling rate of ADC, can obtain very high frequency resolution and larger dynamic range simultaneously.Of the present invention have the advantages such as input tape is roomy, frequency-measurement accuracy is high, dynamic range of signals is large based on channelizing instantaneous frequency measurement (IFM:InstantaneousFrequencyMeasurement) method.

Other features and advantages of the present invention will be set forth in the following description, and, becoming apparent from instructions of part, or understand by implementing the present invention.Object of the present invention and other advantages realize by structure specifically noted in write instructions, claims and accompanying drawing and obtain.

Accompanying drawing explanation

Accompanying drawing only for illustrating the object of specific embodiment, and does not think limitation of the present invention.

Fig. 1 is the process flow diagram of the burst pulse frequency measurement method that the present invention is based on digital channelizing.

Fig. 2 is four channel digital channelization structure schematic diagram of the present invention.

Embodiment

Specifically describe the preferred embodiments of the present invention below in conjunction with accompanying drawing, wherein, accompanying drawing forms the application's part, and together with embodiments of the present invention for explaining principle of the present invention.

Flow process as shown in Figure 1, on hardware, high-speed sampling adopts the processing mode of ADC+FPGA, FPGA comprises a large amount of logical resources and is applicable to carrying out real time signal processing, it is higher that high-speed ADC carries out to intermediate-freuqncy signal the data speed that high-speed sampling obtains, do not mate with the processing speed of FPGA, need to do data speed conversion, a road high speed signal is converted to the process of multi-path low speed signal parallel.Then carry out channelizing process to multi-path low speed parallel data, four channel digital channelizings as shown in Figure 2 can well process four channel parallel datas.

The signal of process of the present invention has a feature, be exactly that bandwidth ratio is larger, the signal being not less than 1GHz can be processed, because the signal to noise ratio (S/N ratio) of broadband signal is low, have a strong impact on the precision of frequency measurement, in order to improve frequency-measurement accuracy, we need broadband signal to be divided into multiple mutually overlapping subband, again respectively subsequent treatment is carried out to each subband, the way that segmentation subband is general is exactly mixing and filtering, just the signal of the certain bandwidth centered by local oscillator can be moved zero intermediate frequency by arranging different local frequencies, the data volume obtained due to high-speed sampling is larger, this mode of sampling splits the words of subband, very large to the requirement of logical resource, and the processing time needed is also larger, the object of frequency Quick Measurement can not be realized, therefore adopt and use digital channelizing technology, it both can realize the division of multiple subband, also real signal can be resolved to complex signal simultaneously, because it takes the mode of extraction, greatly reduce the intractability of follow-up each subband.

The signal of process of the present invention is that instant bandwidth is large, the intermediate-freuqncy signal of narrow pulse width, its pulse width is less than 40ns, when carrying out signal transacting, need the instantaneous phase obtaining signal, the instantaneous phase of complex signal is exactly the arc-tangent value of the ratio of its real part imaginary part, as long as real signal is resolved to the instantaneous phase that complex signal just can obtain signal, it is compare easy to handle in number that real signal is resolved to complex signal, use Cordic algorithm can be easy to realize arctangent cp cp operation in number simultaneously, the plural analytic signal of Cordic algorithm to each channel is utilized to carry out instantaneous amplitude and instantaneous phase calculating, principle formula is as shown in formula (1):

α _i＝tan ^-1(2 ^-i)

d _i＝sign(z ⁱ)

x _i+1＝x _i+d _i×2 ^-i×y _i

y _i+1＝y _i+d _i×2 ^-i×x _i(1)；

Defining variable z in computation process _i, represent the angle do not rotated, be expressed as with following formula

z _i+1＝z _i-d _i×α _i

The target rotated makes z level off to 0, Cordic algorithm by n micro-rotation alpha _iobtain θ phase value, by z _i+1=z _i-d _i× α _i, then as n → ∞, | y _n| → 0, z _∞→ θ=arctan (y _i/ x _i), thus complete the phase extraction of input vector (x, y);

Finally, utilize phase differential measured frequency, shown in the relation formula (2) of phase place and frequency:

Δθ(i)＝θ(n+i)-θ(n)＝2πfit _s(2)

So instantaneous frequency is exactly:

$f=\frac{\mathrm{\Δ}\mathrm{\θ}\left(i\right)}{2{\mathrm{\πit}}_s}---\left(3\right),$

Wherein (x _i, y _i) be input vector, (x _i+1, y _i+1) be output vector, θ is instantaneous phase, α _ieach angle rotated, d _ithe direction that each iteration rotates, t _sfor the sampling period, f is by measured frequency.

Can also improve frequency-measurement accuracy by repeatedly calculating to be averaged, computing formula is as follows:

Δθ(1)＝θ(2)-θ(1)

Δθ(2)＝θ(3)-θ(2)

Δθ(3)＝θ(4)-θ(3)

…

Δθ(n-1)＝θ(n)-θ(n-1)(4)

Then, $f=\frac{1}{n-1}\underset{i=1}{\overset{n-1}{\Σ}}\frac{\mathrm{\Δ}\mathrm{\θ}\left(i\right)}{2{\mathrm{\πit}}_s}---\left(5\right).$

Adopt frequency measurement method provided by the invention, frequency measurement fast and accurately can be carried out to the intermediate-freuqncy signal of large bandwidth, narrow spaces, especially bandwidth is not less than 1GHz, pulsewidth is not less than the signal of 40ns, frequency measurement result can be exported in 300ns, there is higher frequency-measurement accuracy, frequency-measurement accuracy σ≤0.35MHz.

Claims (5)

1., based on a burst pulse frequency measurement method for digital channelizing, it is characterized in that comprising the following steps:

A. paired pulses carries out high-speed sampling;

B. digital channelizing process is carried out to high-speed sampling signal, resolve to multi-path low speed complex signal;

C. utilize Cordic algorithm to carry out instantaneous amplitude and instantaneous phase calculating to the complex signal of each channel, principle formula is as shown in formula (1):

$\begin{array}{cc}\mathrm{\θ}=-\underset{i=1}{\overset{n}{\Σ}}{d}_i{\mathrm{\α}}_i& {\mathrm{\α}}_i\∈\{-1,1\}\end{array}$

α _i＝tan ^-1(2 ^-i)

d _i＝sign(z ⁱ)

x _i+1＝x _i+d _i×2 ^-i×y _i

y _i+1＝y _i+d _i×2 ^-i×x _i(1)；

D. phase differential measured frequency is utilized, shown in the relation formula (2) of phase place and frequency:

Δθ(i)＝θ(n+i)-θ(n)＝2πfit _s(2)

So instantaneous frequency is exactly:

$f=\frac{\mathrm{\Δ}\mathrm{\θ}\left(i\right)}{2{\mathrm{\πit}}_s}---\left(3\right),$

Wherein (x _i, y _i) be input vector, (x _i+1, y _i+1) be output vector, θ is instantaneous phase, α _ieach angle rotated, d _ithe direction that each iteration rotates, t _sfor the sampling period, f is by measured frequency.

2. the burst pulse frequency measurement method based on digital channelizing according to claim 1, is characterized in that also comprising step e after steps d,

E. improve frequency-measurement accuracy by repeatedly calculating to be averaged, computing formula is as follows:

Δθ(1)＝θ(2)-θ(1)

Δθ(2)＝θ(3)-θ(2)

Δθ(3)＝θ(4)-θ(3)

…

Δθ(n-1)＝θ(n)-θ(n-1)(4)

Then, $f=\frac{1}{n-1}\underset{i=1}{\overset{n-1}{\Σ}}\frac{\mathrm{\Δ}\mathrm{\θ}\left(i\right)}{2{\mathrm{\πit}}_s}---\left(5\right).$

3. the burst pulse frequency measurement method based on digital channelizing according to claim 1, it is characterized in that, digital channelizing process in step b comprises: carry out data speed conversion to high-speed sampling signal, be converted to multi-path low speed parallel data, multi-path low speed parallel data is resolved to multi-path low speed complex signal.

4. the burst pulse frequency measurement method based on digital channelizing according to claim 1, it is characterized in that, the bandwidth of pulse described in step a is not less than 1GHz.

5. the burst pulse frequency measurement method based on digital channelizing according to claim 1, it is characterized in that, the pulsewidth of pulse described in step a is not less than 40ns.