CN115580361A - Test calibration equipment DRFM (digital radio frequency modulation) of electronic countermeasure equipment and working method thereof - Google Patents
Test calibration equipment DRFM (digital radio frequency modulation) of electronic countermeasure equipment and working method thereof Download PDFInfo
- Publication number
- CN115580361A CN115580361A CN202211200722.2A CN202211200722A CN115580361A CN 115580361 A CN115580361 A CN 115580361A CN 202211200722 A CN202211200722 A CN 202211200722A CN 115580361 A CN115580361 A CN 115580361A
- Authority
- CN
- China
- Prior art keywords
- signal
- converter
- signals
- frequency
- memory
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/10—Monitoring; Testing of transmitters
- H04B17/15—Performance testing
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/20—Monitoring; Testing of receivers
- H04B17/29—Performance testing
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K3/00—Jamming of communication; Counter-measures
- H04K3/60—Jamming involving special techniques
- H04K3/65—Jamming involving special techniques using deceptive jamming or spoofing, e.g. transmission of false signals for premature triggering of RCIED, for forced connection or disconnection to/from a network or for generation of dummy target signal
Abstract
An electronic countermeasure equipment test calibration device DRFM and a working method thereof. To electronic countermeasure equipment. The method comprises the following steps: down-converting an input radio frequency signal to a baseband or an intermediate frequency; the A/D converter is connected with the down-conversion and converts the signal output by the down-conversion into a digital signal; the memory is connected with the A/D converter and stores the digital signals converted by the A/D converter; the interference generating unit is connected with the memory and generates an interference signal through the control unit; and the D/A converter is connected with the interference generating unit, reads data in the memory, converts the data into intermediate frequency or baseband analog signals through the D/A converter, and converts the intermediate frequency or baseband analog signals into radio frequency signals through the orthogonal up-converter. The invention improves the frequency storage precision and reduces the possibility of being identified by the tested equipment.
Description
Technical Field
The invention relates to electronic countermeasure equipment, in particular to test calibration equipment DRFM of the electronic countermeasure equipment and a working method of the test calibration equipment DRFM.
Background
Electronic warfare is an important component of modern warfare, and electronic countermeasure equipment is one of the cores of modern electronic warfare. With the continuous emergence of electronic countermeasure equipment, the performance index of the electronic countermeasure equipment needs to be tested and evaluated in a test field, so that corresponding electronic countermeasure equipment test calibration equipment is needed. On one hand, the electronic countermeasure equipment test calibration equipment needs to detect and receive radiation signals of the tested equipment, accurately measures parameters of the radiation signals and accurately identifies fine characteristics of the radiation signals; on the other hand, the electronic countermeasure equipment test calibration device also needs to generate various interference signals, wherein deception interference is an important interference mode, including distance deception interference, speed deception interference, distance-speed deception interference and the like, and is used for checking the anti-interference performance of the tested device. A Digital Radio Frequency Memory (DRFM) is an important means for carrying out high-fidelity sampling on a radiation source signal to carry out fine feature analysis and generate deception jamming signals, and stores the received radar signal after down-conversion, so that the radar signal can be sent to a signal processing board for parameter measurement and fine feature analysis on one hand, and can also be subjected to time delay or frequency modulation on the other hand to generate various deception jamming signals which are transmitted out after up-conversion to interfere tested equipment. Therefore, the performance of the test calibration facility DRFM is critical to the test evaluation of the performance of the electronic countermeasure equipment. The test calibration device used as the basis for the judgment must be capable of performing accurate measurement and accurate analysis on the tested device on the one hand, and the interference signal generated by the test calibration device must have small additional information so as to avoid the identification of the tested device on the other hand.
Disclosure of Invention
Aiming at the problems, the invention provides the test calibration equipment DRFM of the electronic countermeasure equipment and the working method thereof, which adopt an amplitude quantization system to carry out theoretical analysis and simulation on the frequency spectrum of quantization distortion, a sampling process, the precision of a copied frequency spectrum and the like so as to be convenient for optimizing an interference strategy and analyzing the performance of test calibration equipment, and provides a phase correction method under the condition of non-full-pulse storage, so that the frequency storage precision is improved, and the possibility of being identified by the test equipment is reduced.
The technical scheme of the invention is as follows: an electronic countermeasure equipment test calibration apparatus DRFM comprising:
down-converting, which down-converts an input radio frequency signal to baseband or an intermediate frequency;
the A/D converter is connected with the down-conversion and converts the signal output by the down-conversion into a digital signal;
the memory is connected with the A/D converter and stores the digital signals converted by the A/D converter;
the interference generating unit is connected with the memory and generates an interference signal through the control unit; and
and the D/A converter is connected with the interference generating unit, reads data in the memory, converts the data into intermediate frequency or baseband analog signals through the D/A converter, and converts the intermediate frequency or baseband analog signals into radio frequency signals through the orthogonal up-converter.
Specifically, a phase correction unit is arranged between the memory and the interference generation unit, and performs phase correction when copying and connecting the stored pulse signals.
Specifically, the memory is a dual-port memory.
Specifically, the down-conversion includes a quadrature down-converter and a local oscillator connected to each other.
A working method of a DRFM (digital radio frequency identification) test calibration device of electronic countermeasure equipment comprises the following steps:
100 According to the frequency of the received radio frequency signal, tuning a local oscillator to enable the output of the down converter to be positioned in a baseband or an intermediate frequency so as to intercept a radiation source signal;
2) The down-conversion consists of quadrature down-conversion and a local oscillator, and generates a baseband or intermediate frequency in-phase signal I (t) and a quadrature signal Q (t);
3) The baseband or intermediate frequency I (t) and Q (t) signals are digitally converted through an A/D converter (or called an analog-to-digital converter);
4) Storing the digitized I (n), Q (n) signals in a memory; after the signal is stored, reading out the I (n) and Q (n) signals in the memory at a certain clock cycle (usually a sampling cycle) for coherent replication of the threat signal;
5) The interference generating unit realizes selection of various interference working modes of the DRFM through the control unit so as to complete different application requirements and generate corresponding I '(n) and Q' (n);
6) D/A converting the generated digital signals I '(n), Q' (n) by a D/A converter to reconstruct a baseband or intermediate frequency signal;
7) And performing up-conversion on baseband or intermediate frequency I '(t) and Q' (t) signals through an orthogonal up-converter to complete coherent replication of the original signals and reconstruct radio frequency signals.
Specifically, when the memory is connected to a computer or a signal processing board in step 4), the stored signal may be subjected to a characteristic analysis for generating a desired signal waveform.
Specifically, in step 3), the model of the a/D converter is ADC12DJ3200.
Specifically, the model of the D/A converter is AD9164.
Specifically, in step 7), the signal between the time T0 and the time T0 is cyclically copied N times when the signal is copied, and truncation is performed when the signal is copied to a required length L, where N = Int (L/T0), and Int is a rounding operation, so that the signal is subjected to both phase correction and reflects the characteristics of the signal itself.
The DRFM adopts an amplitude quantization system, theoretically analyzes and simulates the frequency spectrum of quantization distortion, a sampling process, the precision of a copied frequency spectrum and the like so as to be convenient for optimizing an interference strategy and analyzing the performance of a test calibration device, and provides a phase correction method under the condition of non-full pulse storage, so that the frequency storage precision is improved, and the possibility of being identified by a tested device is reduced.
Drawings
Figure 1 is a flow chart of the operation of an amplitude quantized quadrature two channel DRFM,
figure 2 is a schematic diagram of a sine wave quantization scenario,
figure 3 is a schematic diagram of sample signal reception,
figure 4 is the result of a spectral simulation with no phase discontinuity,
figure 5 is a result of a spectral simulation with a phase discontinuity of 90,
figure 6 is a result of a spectral simulation with a phase discontinuity of 180,
figure 7 is the result of a spectrum simulation with the number of copies N =50,
figure 8 is a schematic block diagram of a sample storage mode phase correction,
figure 9 is a schematic diagram of 3bit phase quantization,
figure 10 is a schematic diagram of a replica sinusoidal pulse signal end-to-end,
figure 11 is a schematic diagram of a non-single frequency signal waveform,
figure 12 is a schematic diagram of a signal received in a quasi-sample manner,
figure 13 is a diagram of an original signal and its spectrum,
figure 14 is a graph of a signal and its spectrum at a sample storage period T1,
fig. 15 is a diagram of a signal and its spectrum at the time of sampling the memory period T2.
Detailed Description
According to the special requirements of test calibration equipment, the DRFM adopts an amplitude quantization system, theoretical analysis and simulation are carried out on the frequency spectrum of quantization distortion, a sampling process, the precision of a copied frequency spectrum and the like, so that an interference strategy is optimized, the performance of the test calibration equipment is analyzed, and a phase correction method under the condition of non-full-pulse storage is provided, so that the frequency storage precision is improved, and the possibility of being identified by test equipment is reduced.
Compared with phase quantization, the multi-bit amplitude quantization DRFM can preserve the amplitude, phase and frequency information of the original signal with high fidelity, and has the capability of analyzing complex waveforms and fine features, and can distinguish simultaneously arriving signals. A larger unambiguous bandwidth can be obtained after quadrature amplitude sampling.
Work flow of amplitude quantization orthogonal dual-channel DRFM
The working principle of the amplitude quantized quadrature two channel DRFM is shown in fig. 1. The input radio frequency signal is down converted to baseband or intermediate frequency, then converted into digital signal by A/D converter, and sent to high-speed dual-port RAM of DRFM for storage. After a desired delay, the data is read from the memory, converted to an intermediate frequency or baseband analog signal by a D/a converter, and upconverted to a radio frequency signal. DRFM uses dual port memory as high speed digital memory to ensure simultaneous signal recording and reconstruction. Different delays can be generated by controlling the read-write time difference of the memory through the controller, the phase modulation is carried out on the stored signals to generate Doppler frequency shift, and the deceptive jamming is realized. Furthermore, the signal may also be amplitude modulated by the controller, which is also a point in its superiority over the phase quantization regime. When fine feature analysis is required, it can be read out from the memory for analysis.
The working process of the DRFM is as follows:
(1) Tuning a local oscillator according to the frequency of the received radio frequency signal to enable the output of the down converter to be positioned in a base band or an intermediate frequency so as to intercept a radiation source signal;
(2) Down conversion. The system consists of quadrature down-conversion and a local oscillator and generates a baseband or intermediate frequency in-phase signal I (t) and a quadrature signal Q (t);
(3) Digitization of the baseband or intermediate frequency I (t), Q (t) signals. Realized by an a/D (analog to digital converter) in the figure.
(4) The digitized I (n), Q (n) signals are stored in a memory. After signal storage, the I (n), Q (n) signals in the memory are read out at a certain clock cycle (usually a sampling cycle) for coherent replication of the threat signals.
(5) An interference signal is generated. Through the controller, various interference working modes of the DRFM can be selected, so that different application requirements are met, and corresponding I '(n) and Q' (n) are generated.
(6) The baseband or intermediate frequency signal is reconstructed. That is, the generated digital signals I '(n), Q' (n) are D/a converted.
(7) The radio frequency signal is reconstructed. And performing up-conversion on the baseband or intermediate frequency I '(t) and Q' (t) signals to finish coherent replication of the original signals.
(8) When a memory in the DRFM is associated with a computer or signal processing board, characterization of the stored signal may also be implemented, or used to generate the desired signal waveform.
Spectral analysis of quantized distortion
The sources of DRFM spurious signals are mainly three: local oscillator leakage, mirror response and cross modulation occurring during up-down conversion, harmonics caused by quantization. Parasitic signals resulting from the first two factors. Can be suppressed by careful design of the circuit and selection of the devices. The present invention focuses on analyzing harmonics caused by quantization.
A large number of harmonics are generated during the digital quantization, and a general expression of the amplitude of the quantized harmonics is derived below, thereby facilitating analysis of the spectrum of the quantized distortion.
For the down-converted quadrature two-channel input signal, it can be expressed as:
wherein the content of the first and second substances,
a (t) is the amplitude of the signal,
in order to be the initial phase of the signal,
is the angular frequency of the signal. To simplify the analysis, a (t) is normalized to 1,
ideally, I (t) and Q (t) differ by only 90 °, so that either channel signal can be analyzed.
Without loss of generality, consider a sinusoidal signal x (t) = sin ω i t。
It is assumed that the signal is uniformly quantized into q discrete values, i.e. q is the number of quantization levels. As shown in fig. 2, it may be formed by different pulses x of alternating polarity 1 (t)、x 2 (t) and (8230), and overlapping.
According to the Fourier series expansion property of the sine function, the following can be obtained:
A 1n ＝0；A 2n ＝0；…
…
Wherein, A 1n 、A 2n 、…、B 1n 、B 2n Are fourier series expansion coefficients. It can be seen that the fourier series expansion of each alternating polarity pulse has only an odd sinusoidal term. Thus, the Fourier coefficients of the Fourier series expansion of the waveform after the superposition of q/2 alternating pulses can be expressed as:
this is to quantify the magnitude of each odd harmonic generated. Thus, the Fourier series expansion of the quantized waveform can be expressed as:
if the amplitude of each odd harmonic is converted into the relative value of the amplitude of the original signal, the following steps are performed:
as can be seen from the above equation, the relative value of the harmonic amplitude is related to the harmonic order n and the quantization level number q, and the general trend is that the larger the harmonic order, the smaller the amplitude, and the larger the quantization level number, the smaller the harmonic. The number q of quantization levels is determined by the number of quantization bits, q =2 m Where m is the number of significant digits of the A/D converter. The higher the number of quantized bits and the higher the sampling rate, the higher the fidelity of the replica signal.
Selection of A/D converter and D/A converter
From the above analysis, the multi-bit amplitude quantization DRFM can be used for analyzing signal fine features and captured signal spectrum, and radar interference on complex waveforms. But too high a number of bits is not meaningful for low signal-to-noise ratio input signals. In addition, due to the limitation of the device, the a/D converter with high bit number and high sampling rate is difficult to implement and the cost is also quite high.
In the occasion of high fidelity, the requirement of quantization bit number is usually more than 6 bits, so that the dynamic range of the system can be ensured, the accurate recovery of signals and the accurate measurement of parameters can be ensured, and the capacity of processing simultaneously arriving signals can be realized.
The effect of the number of quantization bits n on the signal-to-noise ratio of the reconstructed signal can be estimated by:
S/N＝6.02n+1.76+10lg(f s /2f i )。
in the formula, S/N is the power ratio of the main frequency power and the spurious level of the reconstructed signal, and fs and fi are the sampling frequency and the signal frequency respectively.
When m =8, i.e., the number of significant bits of the a/D converter is 8, q =2 m =256, to B' 2n+1 The calculation results are shown in table 1:
table 1 relative amplitude of each harmonic in 8bit amplitude quantization
As can be seen from table 1, when the number of significant digits of the a/D converter is 8, the relative amplitude of each harmonic already meets the requirement of the equipment index. At the same time, modern electronic countermeasure equipment requires increasingly wider bandwidths, typically requiring 1GHz, and therefore requires a sampling rate of at least 2Gsps for the a/D converter.
The invention adopts ADC12DJ3200 chips of TI company in combination with mainstream A/D converter products adopted by the current electronic warfare equipment. The ADC12DJ3200 is a 12-bit high-speed dual channel analog-to-digital converter (ADC) with a significand greater than 8 bits. In combination with the reality, the 12-bit conversion result is 8-bit truncated in consideration of the transmission rate and the storage capacity. The ADC12DJ3200 has the sampling rate of 3200MSPS in a dual-channel mode, and the sampling rate of the device can reach 6400MSPS in a single-channel mode. Programmable tradeoffs in channel count (dual channel mode) and nyquist bandwidth (single channel mode) allow flexible hardware to be developed to meet the requirements of high channel count or wide transient signal bandwidth applications. ADC12DJ3200 uses a high speed JESD204B output interface, with up to 16 serial lanes, with serial output lane rates up to 12.8Gbps.
The corresponding D/A converter is realized by an AD9164 chip of ADI company. AD9164 is a high performance 16-bit digital-to-analog converter (DAC) and direct digital frequency synthesizer (DDS) that supports update rates up to 6 GSPS. The DAC inner core is based on a four-channel switch structure and matched with a 2-time interpolation filter, so that the effective update rate of the DAC is up to 12GSPS in some modes. The high dynamic range and bandwidth make these DACs well suited for the most demanding high-speed Radio Frequency (RF) DAC applications.
In the invention, the conversion rates of the ADC12DJ3200 and the AD9164 are both 2.4Gsps under the control of a device clock network, and the bandwidth requirement of 1GHz is met.
Sampling process and spectral feature analysis
The sampling process directly affects the spectral characteristics of the output signal, as will be demonstrated by the following analysis.
Consider a fourier series expansion of the quantized input signal:
let the sampling signal be:
wherein, T s In order to be the sampling period of time,
the sampled output signal may be represented as: x is the number of p (t)＝x q (t)·p(t)。
Wherein x is q (t) Fourier transform:
fourier transform of p (t):
according to the convolution theorem, there are:
Storage mode analysis of DRFM
The storage mode of the DRFM is divided into three types, namely full pulse storage, sample pulse storage and quasi-sample pulse storage. The full pulse storage means that the memory stores all input pulse signals. The stored data is read out at a given time as required, and the signal is reconstructed by the D/a. With a DRFM operating in this manner, the output signal is at exactly the same frequency as the input and therefore has very high coherence. It can produce drag and false target interference. Because the signals in the duration are all stored, the amplitude quantized DRFM can also be used for analyzing the fine characteristics of the signals or interfering the intra-pulse frequency and phase modulation signals (pulse pressure radar), and the capability of processing complex signals is strong. Are often used for storage of complex signals. However, when the signal pulse duration is long, a large-capacity memory is required for storing the full signal, in other words, the number of radiation source signals that can be recorded by the memory is reduced when the storage capacity is constant. At this time, sample pulse storage or quasi-sample pulse storage is generally adopted.
In sample pulse storage, the DRFM records only a small segment (e.g., 0.1 us) of the beginning of the input signal and then controls the stored data to be read out repeatedly. Since the signal frequency is not synchronous with the sampling clock, even if the signal is a single carrier frequency signal, the initial phase point and the ending phase of the intercepted signal are not necessarily continuous, so that the inconsistency of the output frequency, namely the coherence is deteriorated. To improve the coherence, phase correction must be performed when reading out the data. The advantage of sample pulse storage is that the memory can store multiple radiation source signals and therefore has the ability to interfere with multiple radiation sources. Sample pulse storage is generally only suitable for storage of intra-pulse frequency-constant signals.
The pilot sample is a technology for periodically controlling the working time of receiving and transmitting of the DRFM jammer and performing alternate receiving and transmitting on signals. When the system alternately receives and transmits, attention needs to be paid to whether the receiving and transmitting switch is completely disconnected with the other end, and the influence on the normal work of the system caused by the bypass of the other end is avoided.
The problem of signal receiving and transmitting isolation is solved to a certain extent by the standard sample storage mode. And the system has a smaller delay time because the pulse signal is stored intermittently. Although the signals obtained by the quasi-sampling are intermittent and may miss important information in the signals, the signals can be sampled for a plurality of times by reducing the alternation time, so that the coherence of the interference signals and the original signals is ensured.
In summary, the invention adopts a full-pulse storage method when performing fine feature analysis on the received signal; when the modulation interference is carried out on the intra-pulse fixed carrier frequency receiving signal, a sample storage mode is adopted; when the modulation interference is carried out on the complex modulation received signal in the pulse, a quasi-sample storage mode is adopted.
Frequency storage precision and spectrum analysis of sample storage mode
The general workflow of sample sampling and frequency storage is as follows: during a specific time period, a signal with certain carrier wave characteristics is sampled and stored, and then the output is repeatedly copied in an end-to-end mode. The spectral and frequency accuracy of the replica output signal is analyzed in the following two cases, one being that the received signal is a continuous wave signal and the other being that the received signal is a pulsed signal.
Considering the first continuous wave case, the replicated output is repeated an unlimited number of times.
Let the sinusoidal pulse signal as shown in the figure, its expression is:
the sinusoidal pulse is applied with a period T 0 Repeating indefinitely to obtain a sinusoidal pulse sequence, whose expression is:
for a sinusoidal pulse signal x (t), its fourier transform is:
therefore, x r (t) Fourier transform: the carrier frequency of the sinusoidal pulse signal is,
wherein, ω is i Being the carrier frequency, omega, of a sinusoidal pulse train signal 0 The pulse repetition frequency of the sinusoidal pulse train signal.
The expression result shows that the frequency spectrum of the output signal is repeatedly copied for infinite times and is discrete, and the frequency is established at +/-m omega 0 At a discrete frequency point of, and, when ω is i ＝±mω 0 Reaching a maximum value. Therefore, when the carrier frequency ω of the sinusoidal pulse signal is input i Not necessarily exactly equal to an integer multiple m omega of the pulse repetition frequency of the sinusoidal pulse train signal 0 Then, a frequency error is generated, which can be specifically expressed as:
Δω＝ω i -ω 0 ·mod(ω i /ω 0 ) Mod represents the nearest integer.
Transforming this expression to obtain:
it can be seen that the phase difference at the head and tail is observed when the copy is repeated
And reproducing the width T of the sinusoidal pulse signal 0 The frequency error of the replica signal is determined.
The smaller the frequency error is; t is 0 The larger the frequency error.
Considering the second pulse case, the replicated output is repeated a finite number of times.
Assume that the waveform of the duplicate output is as shown. T is r Long sinusoidal pulse of width T 0 Short sinusoidal pulses of width are connected end to end. In this mode of operation, the replica output signal is head-to-tailWhere there is a certain phase error, the sample signal is received as shown in fig. 3.
T designed for replication 0 The short sinusoidal pulse signal of width is:
the sinusoidal pulse is applied with a period T 0 Repeating the above steps N times to obtain a sinusoidal pulse sequence, wherein the expression is as follows:
then the long sinusoidal pulse signal x r (t) Fourier transform:
wherein, f i Is the carrier frequency of the sinusoidal pulse train signal.
As can be seen from the above equation, the output signal is repeated a finite number of times, and its frequency spectrum is continuous. Due to the width T of the sinusoidal pulse signal 0 (i.e., the sampling period width) is not necessarily exactly equal to the carrier period T of the sinusoidal pulse train signal i Integer multiple of the number of the first and second phases, so that phase discontinuity occurs at the end-to-end of the cyclic copy. The phase discontinuity and the width T of the sinusoidal pulse signal 0 Determines the magnitude of the frequency error and the relative amplitude. In addition, the number of times of repetitive reproduction N and the sinusoidal pulse signal width T 0 Directly affecting the width of the spectrum.
Because the quantitative analysis of the above formula is difficult, the invention performs simulation analysis on the amplitude spectrum of the reproduced output signal under the following conditions.
1) The effect of phase discontinuity on the amplitude spectrum of the replica output signal;
2) The influence of the number of repeated copying times N on the amplitude spectrum of the copied output signal;
3) The effect of the replica sinusoidal pulse signal width on the amplitude spectrum of the replica output signal.
Due to the reproduction of the sinusoidal pulse signal width T 0 Similar to the effect in the case of continuous waves, which is not described here, simulation analysis is performed only for the first two cases.
a) Influence of phase discontinuity on the spectrum:
the results of the spectrum simulation with no phase discontinuity are shown in fig. 4.
As can be seen from the figure, the spectral characteristics at this time are: no frequency storage error and small harmonic wave of frequency storage signal.
The results of the spectral simulation with the phase discontinuity of 90 are shown in fig. 5.
As can be seen from the figure, the spectral characteristics at this time are: the frequency storage has errors, the harmonic power is increased, and the peak power of the frequency spectrum of the frequency storage signal is reduced.
The results of the spectral simulation with a phase discontinuity of 180 are shown in fig. 6.
As can be seen from the graph, the spectral characteristics at this time are: the frequency storage error is increased, two equal peak values appear on two sides of the input frequency, and the frequency storage signal frequency spectrum peak power is further reduced.
According to the simulation result, as the phase error increases, the frequency storage error increases, the harmonic power increases, and the peak power of the frequency storage signal spectrum gradually decreases, so that the frequency storage precision and the deceptive jamming effect are greatly reduced, and even become the basis for the identification of the other party.
b) Influence of the number of copies on the spectrum:
the increase in the number of copies does not significantly improve the frequency storage accuracy, but the spectrum becomes narrower as the number of copies increases. Fig. 7 shows a spectrum simulation result when the number of copies N = 50.
Sample storage mode phase correction
From the above analysis, it can be seen that the phase difference between the head and the tail of the pulse signal is repeated
Is a key influencing factor for determining the frequency error, harmonic power and signal power of the reproduced signal。
The smaller the frequency error, and therefore it is necessary to phase correct the stored pulse signal at the time of the replica connection. The phase correction should be done before the modulation produces an interfering signal, as shown in fig. 8.
The phase correction method described in the literature is basically performed around the phase quantization method. The invention provides a phase correction method in an amplitude quantization mode on the basis of comparing advantages and disadvantages in the amplitude quantization mode and the phase quantization mode.
The phase quantization is to divide one period of the sinusoidal signal into 2 N And N is the number of bits for phase quantization, and then the phase code generated in each phase interval is stored by a memory. During reconstruction, the phase code is converted into a stepped sine wave. A common use is 3-bit phase quantization, as shown in fig. 9.
As can be seen from FIG. 9, 3-bit phase quantization divides the sine wave period into 2 3 =8 phase intervals, each phase interval being 360 °/2 3 =45 °. Phase quantization retains only the phase (frequency) characteristics of the signal and therefore has lower requirements on critical devices a/D and D/a and is easier to implement than amplitude quantization. However, the parasitic level is high, the processing capability of the amplitude modulation signal is limited, signals arriving at the same time are difficult to distinguish, and the method is only suitable for storing and recovering simple signals. For the radar interference of a complex system or the requirement that an interference signal accurately imitates the waveform of a radiation source emission signal, especially a radiation source signal with amplitude modulation or a mixed signal of a plurality of signals, multi-bit amplitude quantization is more advantageous, phase correction in a sample storage mode is more accurate, and the only defect is that the real-time performance is poor.
Fig. 10 is a schematic diagram of the reproduction of sinusoidal pulse signals in an exemplary storage mode.
The length of the replica signal is T0, and as can be seen from the figure, since T0 is not an integral multiple of the period of the sine wave signal, a phase error exists when the signals are connected end to end. When the signal is copied, the signal can be searched from the first address of the storage signal, and the phase of the signal at the time T0 is the same as that of the signal at the time T0, so that the signal between the time T0 and the time T0 is circularly copied for N times when the signal is copied to a required length L and then is cut off, wherein N = Int (L/T0), and Int is a rounding operation. In this way, the replicated signal is both phase corrected and characteristic of the signal itself.
However, large errors may occur with this approach for signals with amplitude modulation information, such as communication signals.
For quadrature two-channel signals I (t) and Q (t), the phase is
The phase value of a certain two instants is related to the signal amplitudes I (t) I and Q (t) I, so that for a signal with an amplitude modulated signal or a mixture of several signals, even if the signals at two different instants have the same phase and the same amplitude, it does not mean that the signals at two different instants are at the same periodic instant of the signal. Fig. 11 shows the waveform of a tacon signal, which has two frequencies of 15Hz and 135Hz, and is strictly speaking a mixed modulation signal with two frequencies of 15Hz and 135 Hz.
As can be seen from fig. 11, the amplitudes at times t1, t2, and t3 are equal, and the phase values may be the same. If the sample receiving wave gate is cut off at the time t3 and the searching is started from the first address of the storage signal according to the method, the time t1 is considered to be the first address of the copy signal, and the copy signal and the original signal have serious deviation. Therefore, signals in a period of time before the time t3 are required to participate in comparison and search, the time t2 is finally confirmed to be the first address of the copied signal through amplitude and phase comparison, and then the signals between the time t2 and the time t3 are circularly copied, so that the copied signal truly reflects the characteristics of the original signal and is subjected to phase correction. This is also one of the characteristics that amplitude quantization is superior to phase quantization.
Frequency storage analysis of standard sample storage mode
The difference between the standard sample storage mode frequency storage and the sample storage mode frequency storage is that the standard sample storage mode frequency storage stores original sampling signals according to a certain period, as shown in fig. 12.
The quasi-sample storage mode is generally used for signal frequency storage with intra-pulse modulation, and because intra-pulse signals do not have single frequency characteristics, a splicing mode of the quasi-sample storage mode cannot be adopted. The invention explains the factors influencing the frequency storage precision and the signal recovery in the mode by carrying out simulation analysis on the standard sample storage frequency spectrum of the linear frequency modulation signal.
The frequency storage diagrams of the standard sample storage method are shown in fig. 13 to 15.
In fig. 14 and 15, T1> T2. It can be seen that as the time between the quasi-sample intervals decreases, the signal is sampled more and stored, and the information of the spectrum is preserved more. Therefore, in the quasi-sample frequency storage mode, on the premise of meeting the real-time requirement, the sampling storage period should be reduced as much as possible, so that more original signal information can be reserved, and higher coherence between the stored signal and the original signal is ensured.
The disclosure of the present application also includes the following points:
(1) The drawings of the embodiments disclosed herein only relate to the structures related to the embodiments disclosed herein, and other structures can refer to general designs;
(2) In case of conflict, the embodiments and features of the embodiments disclosed in this application can be combined with each other to arrive at new embodiments;
the above are only the embodiments disclosed in the present application, but the scope of the present disclosure is not limited thereto, and the scope of the present disclosure shall be subject to the scope of the claims.
Claims (9)
1. An electronic countermeasure equipment test calibration apparatus DRFM, comprising:
down-converting an input radio frequency signal to a baseband or an intermediate frequency;
the A/D converter is connected with the down-conversion and converts the signal output by the down-conversion into a digital signal;
the memory is connected with the A/D converter and used for storing the digital signals converted by the A/D converter;
the interference generating unit is connected with the memory and generates an interference signal through the control unit; and
and the D/A converter is connected with the interference generating unit, reads data in the memory, converts the data into an intermediate frequency or baseband analog signal through the D/A converter, and converts the intermediate frequency or baseband analog signal into a radio frequency signal through the orthogonal up-converter.
2. The DRFM test calibration device for electronic countermeasure equipment according to claim 1, wherein a phase correction unit is provided between said memory and said interference generating unit for performing phase correction when the stored pulse signal is connected in duplicate.
3. The DRFM test calibration apparatus for electronic countermeasure equipment according to claim 1, wherein said memory is a dual port memory.
4. The device DRFM according to claim 1, wherein said down-conversion comprises a quadrature down-converter and a local oscillator connected to each other.
5. A working method of a DRFM (digital radio frequency identification) test calibration device of electronic countermeasure equipment is characterized by comprising the following steps:
1) Tuning a local oscillator according to the frequency of the received radio frequency signal to enable the output of the down converter to be positioned in a base band or an intermediate frequency so as to intercept a radiation source signal;
2) Down-converting to produce a baseband or intermediate frequency in-phase signal I (t) and a quadrature signal Q (t);
3) The baseband or intermediate frequency I (t), Q (t) signals are converted digitally through an A/D converter;
4) Storing the digitized I (n), Q (n) signals in a memory; after the signals are stored, reading out the I (n) and Q (n) signals in the memory in a certain clock cycle for coherent replication of the threat signals;
5) The interference generating unit realizes selection of various interference working modes of the DRFM through the control unit so as to complete different application requirements and generate corresponding I '(n) and Q' (n);
6) D/A converting the generated digital signals I '(n), Q' (n) through a D/A converter to reconstruct a baseband or intermediate frequency signal;
7) And performing up-conversion on baseband or intermediate frequency I '(t) and Q' (t) signals through an orthogonal up-converter to complete coherent replication of the original signals and reconstruct radio frequency signals.
6. The method as claimed in claim 5, wherein when the memory in step 4) is connected to a computer or a signal processing board, the characteristic analysis of the stored signal is used to generate the desired signal waveform.
7. The method as claimed in claim 5, wherein in step 3), the A/D converter is of the type ADC12DJ3200.
8. The method according to claim 5, wherein said D/A converter is of type AD9164.
9. The method as claimed in claim 5, wherein in step 7), the signal is copied N times between time T0 and time T0, and then truncated when copied to the required length L, wherein N = Int (L/T0), and Int is a rounding operation, so that the signal is both phase-corrected and reflects the characteristics of the signal itself.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211200722.2A CN115580361A (en) | 2022-09-29 | 2022-09-29 | Test calibration equipment DRFM (digital radio frequency modulation) of electronic countermeasure equipment and working method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211200722.2A CN115580361A (en) | 2022-09-29 | 2022-09-29 | Test calibration equipment DRFM (digital radio frequency modulation) of electronic countermeasure equipment and working method thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115580361A true CN115580361A (en) | 2023-01-06 |
Family
ID=84582481
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211200722.2A Pending CN115580361A (en) | 2022-09-29 | 2022-09-29 | Test calibration equipment DRFM (digital radio frequency modulation) of electronic countermeasure equipment and working method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115580361A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116506040A (en) * | 2023-06-27 | 2023-07-28 | 西安晟昕科技股份有限公司 | Evaluation method for signal defense of electronic equipment |
| CN116699529A (en) * | 2023-08-01 | 2023-09-05 | 西安擎飞电子科技有限公司 | Low-storage-resource-consumption full-pulse storage DRFM method and system |
-
2022
- 2022-09-29 CN CN202211200722.2A patent/CN115580361A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116506040A (en) * | 2023-06-27 | 2023-07-28 | 西安晟昕科技股份有限公司 | Evaluation method for signal defense of electronic equipment |
| CN116506040B (en) * | 2023-06-27 | 2023-09-05 | 西安晟昕科技股份有限公司 | Evaluation method for signal defense of electronic equipment |
| CN116699529A (en) * | 2023-08-01 | 2023-09-05 | 西安擎飞电子科技有限公司 | Low-storage-resource-consumption full-pulse storage DRFM method and system |
| CN116699529B (en) * | 2023-08-01 | 2023-10-20 | 西安擎飞电子科技有限公司 | Low-storage-resource-consumption full-pulse storage DRFM method and system |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN115580361A (en) | Test calibration equipment DRFM (digital radio frequency modulation) of electronic countermeasure equipment and working method thereof | |
| CN102325058B (en) | Frequency change system group delay test method | |
| US3947827A (en) | Digital storage system for high frequency signals | |
| Mishali et al. | Xampling: Signal acquisition and processing in union of subspaces | |
| CN101300497B (en) | Data compression for producing a spectrum trace | |
| US11237204B2 (en) | Real-time jitter impairment insertion for signal sources | |
| JP2001237701A (en) | Signal analyzing device | |
| Wu et al. | The design of digital radar receivers | |
| US3991409A (en) | Digital storage system for high frequency signals | |
| JP2006292710A (en) | Wide band realtime digital spectrum system | |
| CN106199187B (en) | A kind of test method of multi-tone signal relative phase | |
| Jenq | Digital-to-analog (D/A) converters with nonuniformly sampled signals | |
| EP3507954B1 (en) | Time sequenced spectral stitching | |
| US20080291987A1 (en) | Test Signal Generating Apparatus for Communications Equipment and Test Signal Generating Method for Communications Equipment | |
| Ehrman et al. | Real-time software simulation of the HF radio channel | |
| JPH04229703A (en) | Method for generating phase correlation waveform | |
| WO2000013032A1 (en) | Low-power/wideband transfer function measurement method and apparatus | |
| Grabowski | SDR-based LFM signal generator for radar/SAR systems | |
| D’Arco et al. | A time base option for arbitrary selection of sample rate in digital storage oscilloscopes | |
| CN115567125A (en) | Multichannel calibration and signal coherent recovery method and device for broadband channelization reception | |
| CN110933006A (en) | Parallel digital synthesis method and circuit of FM modulation signal | |
| US6088403A (en) | Signal extraction method and apparatus | |
| Patel et al. | Characterization of phase and amplitude quantization effects in a direct digital synthesis-based waveform generator for future software-defined GPS payloads | |
| US6484018B1 (en) | Method and apparatus for defining and generating local oscillator signals for down converter | |
| Raze et al. | Non coherent spectral analysis of ADC using FFT windows: An alternative approach |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |