Background technology
Radar is in the receiving course to the pulse-modulated signal of its emission, because the influence of multipath fading, and the influence of radar receiver inside (as amplifier, frequency mixer etc.) nonlinear device, can make the rising edge of pulse-modulated signal and negative edge produce conditions of streaking.The rising edge of modulation signal and negative edge can surpass 1us in the time of serious.Therefore in the radar receiving processing system of reality, need to be equipped with high-precision dynamic detection module.And in fact, Dynamic High-accuracy detection technology is also to be in advanced person's in the present age the passive radar, the core technology of long baseline " time difference method direction finding positioning equipment ".In order to improve the precision of time difference method direction finding, require dynamic cymoscope under the actual signal environment (the signal edge may reach the us magnitude), in big as far as possible dynamic range, to reach as far as possible little time-delay variable quantity and the shake of alap forward position.Because the time-of-arrival direction finding location is a hot spot technology in the electronic warfare field, therefore since the seventies in last century six, the technical research and the discussion of dynamic detection is just arranged always.At the specific implementation method of this problem, what be most widely used is the method that the simulation detection adds the comparison decision circuit afterwards, and wherein the method for threshold judgement is the most typical with half-power threshold method and maximum-slope method.But, owing to be subjected to the influence of analog device characteristic, the result that the method for employing simulation detection obtains is often not ideal enough, be difficult to the pulse detection of the long rising edge of reply, actual drift when long rising edge and jitter error performance often reach more than the 100ns order of magnitude, and this causes the Radar Signal Processing of rear end and system performance and has a strong impact on.
Widely used analog amplitude detection in radar at present, employing be to carrying out the mode of threshold judgement behind the direct amplitude discrimination of radar signal; This system mainly adopts analog device to realize having shortcomings such as volume is big, low in energy consumption, is eliminated gradually in High Definition Systems.Microwave detector and digital quadrature wave detector become new detection mode gradually, microwave detector is mainly by extraction and the direct decision operation of microwave device realization to amplitude, and the digital quadrature wave detector mainly is by directly the sampled data amplitude of carrying out being extracted and decision operation after the AD sampling.
Through the prior art literature search is found, the patent No. is 200420108665.6 Chinese patent, patent name is: the integrated coaxial ripple wave detector that declines, be serially connected with respectively every straight high-pass filtering circuit on the internal and external conductor of its input coaxial port in this patent, high-pass filtering circuit back serial connection II type power attenuation network, above-mentioned attenuation network back connects detection crystal and impedance matching network thereof, and the feeble signal of detection crystal output is delivered to the input port of low-frequency amplifier again; Above-mentioned all circuit are concentrated to be placed in the metallic shield box, and the output signal of low-frequency amplifier is exported by erection joint, and microwave signal to be measured is imported via radio-frequency joint.This device goes for the needs of demodulation system generally speaking, but can't rise at overlength/the negative edge pulse realizes accurate detection operation, suppressed the application of High Definition Systems in real system such as time-of-arrival direction finding location greatly.
Summary of the invention
The present invention is directed to above-mentioned the deficiencies in the prior art, a kind of digital high precision dynamic cymoscope has been proposed, can carry out accurate detection shaping at the overlength rising edge and the negative edge of radar received pulse modulation signal, and output amplitude is the dynamic rectified signal of digital high precision of Transistor-Transistor Logic level, the present invention have integrated degree height, volume little, make and debug simple, stable and reliable for performance, characteristics such as versatility is good.
The present invention is achieved through the following technical solutions, the present invention includes: analog-digital converter, programmable gate array, phaselocked loop, power module, wherein:
Analog-digital converter (Analog to Digital Converter, ADC) pulse signal that will import overlength rising/negative edge wherein carries out analog to digital conversion, obtains digital sampled signal, and outputs to programmable gate array;
(Field Programmable Gate Array FPGA) realizes the pulse signal of overlength rising edge is carried out digital detection programmable gate array, output TTL Digital Logic waveform;
(Phase Loop Lock PLL) provides system clock for analog-digital converter and programmable gate array to phaselocked loop;
Power module provides the direct supply of high stable for above-mentioned module.
Described programmable gate array comprises: digitizing envelope extract block, envelope shaping module, self-adaptation dynamic decision thresholding module, video pulse Shaping Module, wherein:
The digitizing envelope extract block adopts digitizing extract real-time envelope technique, to the amplitude information of digital sampled signal extraction signal carrier, obtains the signal envelope of input pulse signal;
The envelope shaping module is carried out envelope shaping to the signal envelope that the digitizing envelope extract block transmits, offset the interference of noise to signal envelope, promptly, carry out digital smoothness simultaneously, improve the noise robustness of system with further elimination The noise by the low pass filter filters out high frequency noise;
Self-adaptation dynamic decision thresholding module adopts self-adaptation dynamic decision threshold technique to through the signal envelope of envelope shaping, forms the dynamic decision thresholding, and with compare judgement through the signal envelope that postpones, obtain the video pulse of TTL waveform;
The video pulse Shaping Module carries out shaping pulse to the video pulse of TTL waveform, and rigid removal duration length is less than the spuious short pulse of the burr of setting value, to remove the ghost pulse information that noise brings.
Described digitizing envelope extract block, it adopts the digital quadrature technology, by signal orthogonalization being obtained real-time I/Q (inphase/orthogonal, in-phase/quadrature-phase) two paths of data, and then the operation of extracting signal amplitude.
Described self-adaptation dynamic decision thresholding module, the self-adaptation dynamic decision threshold technique that it adopts, be meant amplitude and noise floor according to the input pulse signal, self-adaptation, dynamically adjust the decision threshold of monopulse, and determine the amplitude of the video pulse of output TTL waveform according to decision threshold: if the amplitude of signal envelope is less than decision threshold, output 0, otherwise export 1, to remove the conditions of streaking of rising edge and negative edge.
Compared with prior art, the present invention has following beneficial effect:
(1) the present invention adopts the rising edge of method paired pulses modulation signal of digital signal processing and the conditions of streaking of negative edge accurately to proofread and correct, outputting standard, the little TTL pulse signal of shake, for the measurement of back-end system with stable reference signal is provided synchronously, obtained measuring accuracy index than 1~2 order of magnitude of the dynamic detection skill upgrading of simulation;
(2) use " high-efficiency digital orthogonalization technology " and " self-adaptation dynamic decision thresholding " two gordian techniquies in the programmable gate array among the present invention, played the effect of saving digitized hardware resource and guaranteeing the measuring accuracy of time-delay variable quantity respectively.Simultaneously, adopt digitized processing framework, made full use of the intrinsic advantage of FPGA and digitized processing, guaranteed characteristics such as system integration degree height, volume are little, it is simple, stable and reliable for performance to make and debug, versatility is good based on FPGA;
(3) the hardware testing result of system shows, the present invention shakes ahead of the curve, delays time and reached magnitude about 10ns on the important indicators such as variable quantity and output pulse width precision, under the part situation even less than 5ns, substantially exceeded the precision property of simulation dynamic cymoscope (usually more than 200ns) on the performance.
Embodiment
Below in conjunction with drawings and Examples the solution of the present invention is elaborated: present embodiment is being to implement under the prerequisite with the technical solution of the present invention; provided detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.
As shown in Figure 1, present embodiment comprises: analog-digital converter, programmable gate array, phaselocked loop, power module, wherein:
The pulse signal that analog-digital converter will be imported overlength rising/negative edge wherein carries out analog to digital conversion, obtains digital sampled signal, and outputs to programmable gate array;
Programmable gate array is realized the pulse signal of overlength rising edge is carried out digital detection, output TTL Digital Logic waveform;
Phaselocked loop provides system clock for analog-digital converter and programmable gate array;
Power module provides the high stability direct supply for above-mentioned module.
Described programmable gate array is for the model of altera corp is the FPGA of EP2S60F1020I4.
Described analog-digital converter, it realizes bandpass sampling with the sampling rate greater than 400MHz to input signal, and the A/D sampling rate in the present embodiment is 500MHz, and this is because cross when hanging down when sampling rate, can cause owing sampling, thereby make the performance rapid deterioration of system; In addition, in order to satisfy the high precision time-delay variable quantity of index request, also be necessary to adopt sampling rate greater than 400MHz.
As shown in Figure 2, mounting structure synoptic diagram for present embodiment, for avoiding electromagnetic crosstalk, the present embodiment system is made up of main circuit board, clock circuit plate and electric source filter circuit plate three parts, analog-digital converter, programmable gate array are set on the main circuit board, on the clock circuit plate phaselocked loop is set, on the power filter plate power module is set, the main circuit that ADC and FPGA are installed adopts 116.3 x 86.4mm
26 layers of printed board, the clock circuit that PLL is installed adopts 60.7 x 86.4mm
26 layers of printed board, the electric source filter circuit that power module is installed adopts 180 x 58.6mm
26 layers of printed board, the top layer and the bottom of 3 printed boards are signals layer, and components and parts are installed, the middle layer be one deck power supply, a layer signal, one deck simulation ground and power supply, one deck digitally; To numeral and analog power isolation filter, simulate ground and digitally separately and by magnetic bead be connected; 3 circuit boards adopt the shielding box shielding, both can realize that the space of electromagnetic signal isolated, and make things convenient for the ground connection nearby of radiofrequency signal port again, have avoided the phase mutual interference of radiofrequency signal at cabinet inside.
Described programmable gate array comprises: digitizing envelope extract block, envelope shaping module, self-adaptation dynamic decision thresholding module, video pulse Shaping Module, wherein:
The digitizing envelope extract block adopts digitizing extract real-time envelope technique, ADC sampled data is at a high speed extracted the amplitude information of signal carrier accurately, thereby obtain the signal envelope of input pulse signal;
The envelope shaping module is carried out envelope shaping to the signal envelope that the digitizing envelope extract block transmits, offset the interference of noise to signal envelope, promptly, carry out digital smoothness simultaneously, improve the noise robustness of system with further elimination The noise by the low pass filter filters out high frequency noise;
Self-adaptation dynamic decision thresholding module adopts self-adaptation dynamic decision threshold technique to through the signal envelope of envelope shaping, forms the dynamic decision thresholding, and with compare judgement through the signal envelope that postpones, obtain the video pulse of TTL waveform;
The video pulse Shaping Module carries out shaping pulse to the video pulse of TTL waveform, and rigid removal duration length is less than particular value T
1The spuious short pulse of the burr of=100ns is to remove the ghost pulse information that noise brings.
Described digitizing envelope extract block, the technology of the digitizing extract real-time envelope that it adopts, be meant the digital quadrature technology efficiently that adopts, by signal orthogonalization being obtained real-time I/Q (inphase/orthogonal, in-phase/quadrature-phase) two paths of data, and then the operation of extracting signal amplitude.
The envelope that extracts signal in digital information processing system has 3 kinds of methods usually: Hilbert (Hilbert) amplitude demodulation method, detection-filter method and high pass absolute value demodulation method, present embodiment adopts Hilbert amplitude demodulation method, the Hilbert conversion and the real part of analytic signal be signal itself, imaginary part is its Hilbert conversion, the amplitude of analytic signal is the envelope of signal, in the present embodiment, the Hilbert conversion can realize by FFT easily.
Suppose given continuous time signal x (t), its Hilbert conversion is made as
The Hilbert transducer is that amplitude characteristic is 1 all-pass filter.Signal is by behind the Hilbert transducer, and its negative frequency composition is done+90 ° phase shift, and the positive frequency composition is done 90 ° phase shift.Be made as the analytic signal of signal, then have:
Because the intermediate-freuqncy signal that x (t) is modulated by envelope signal can be designated as:
x(t)=A(t)
*cos(ωt+φ)
Then:
Characteristics according to analytic signal:
z(t)=A(t)*cos(ωt+φ)+j*A(t)*sin(ωt+φ)=A(t)*e
j(ωt+φ)
Can obtain envelope signal A (t) to z (t) delivery:
|z(t)|=|A(t)*e
j(ωt+φ)|=|A(t)|=A(t)
To the discrete signal x (n) that obtains after x (t) sampling, the analytic signal z (n) that also can use the same method and obtain it.
Described self-adaptation dynamic decision thresholding module, the self-adaptation dynamic decision threshold technique that it adopts is meant amplitude and noise floor according to the input pulse signal, self-adaptation, dynamically adjusts the decision threshold of monopulse.Determine the amplitude of the video pulse of output TTL waveform then according to decision threshold: if the amplitude of signal envelope less than decision threshold, is exported 0, otherwise exported 1; Thereby remove the conditions of streaking of rising edge and negative edge.
As shown in Figure 3, described self-adaptation dynamic decision thresholding module, its process of carrying out self-adaptation dynamic decision thresholding is specific as follows: whether at first adjudicate the current demand signal amplitude greater than noise gate ξ
2If signal is less than noise gate ξ
2, whether the signal length that detects accumulative total this moment surpasses T
1=100ns is if the signal cumulative length surpasses T
1, illustrate to have effective pulse signal and just disappeared.Upgrade decision threshold ξ according to the amplitude peak of current pulse signal thus
1, getting decision threshold is 1/2 of amplitude peak, as shown in Figure 4.If signal is greater than noise gate ξ
2, illustrate to have useful signal, then trigger the amplitude peak of upgrading pulse signal; When the signal length that adds up surpasses T
2During=4us, upgrade decision threshold ξ according to the amplitude peak of current pulse signal
1Then according to the decision threshold ξ that dynamically updates
1,, obtain the video pulse of TTL waveform to comparing judgement through the signal envelope that postpones 4us.
As shown in Figure 5, be the test result figure of present embodiment hardware system, among the figure, signal 1 is the modulation sync waveform of input pulse modulation signal, and signal 2 is the pulse-modulated signal of long rising edge, and rising edge is spun out 2us; Signal 3 is the output TTL pulse waveform of system.Infiniium 54845A (the 1.5GHz that test adopts Agilent company to produce; 8GSa/s) digital oscilloscope shows.System output signal (signal 3) is highly stable with the relative delay of input modulating signal (signal 2) as we can see from the figure.By system's DCO, present embodiment is in frequency input signal 275~475MHz scope, in that (the signal rising edge<100ns) He under the relatively poor situation (signal rising edge 1us~2us), the TTL video pulse of output is imported the time-delay variable quantity of modulating pulse relatively all less than 5ns under the reasonable situation of input signal rising edge; Forward position shake signal to noise ratio (S/N ratio) during greater than 6 decibels less than 5ns, signal to noise ratio (S/N ratio) during less than 6 decibels less than 10ns, substantially exceeded the precision property of simulation dynamic cymoscope (usually more than 200ns) on the performance.
From present embodiment as can be seen, present embodiment can be realized the detection function to the input signal of long rising edge well, and have integrated degree height, volume little, make and debug simple, stable and reliable for performance, characteristics such as versatility is good.