CN115184878A - Intermittent frequency self-adaptive adjustment method of frequency modulation slope agility LFM radar - Google Patents
Intermittent frequency self-adaptive adjustment method of frequency modulation slope agility LFM radar Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/36—Means for anti-jamming, e.g. ECCM, i.e. electronic counter-counter measures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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Abstract
The invention provides an intermittent frequency self-adaptive adjusting method of a frequency modulation slope agility LFM radar, which comprises the following steps: step one, performing down-conversion on a radar signal to obtain an LFM complex envelope signal; step two, delaying the LFM complex envelope signal to obtain a corresponding delay signal; mixing the LFM complex envelope signal with a corresponding delay signal and inputting the mixed signal into a frequency discriminator to obtain a frequency difference; and step four, taking the obtained frequency difference as an intermittent frequency, and carrying out intermittent processing on the LFM complex envelope signal. The invention solves the problem of self-adaptive adjustment of the intermittent frequency and realizes the self-adaptive change of the intermittent frequency along with the frequency modulation slope. The adaptive adjustment implementation is simple and only requires mixing the LFM signal with its delayed signal and passing through the frequency discriminator. Meanwhile, the problem of pulse peak position jump formed by intermittent forwarding is solved. The pulse peak position is only related to the delay time of the signal, and the pulse peak position does not jump as long as the delay time is fixed.
Description
[ technical field ] A method for producing a semiconductor device
The invention discloses an intermittent frequency self-adaptive adjusting method of an LFM radar with an agile frequency modulation slope, relates to the field of radar signal processing of an LFM system, and particularly relates to a technology for processing LFM radar signals with an agile frequency modulation slope.
[ background of the invention ]
As a large time-bandwidth product signal, a Linear Frequency Modulated (LFM) signal can effectively solve the contradiction between the radar detection range and the range resolution, and is widely applied to radar systems. Intermittent forwarding can generate multiple pulse peaks after pulse compression processing by using the range-doppler coupling characteristic of LFM signals. However, for the LFM radar of an advanced system such as frequency modulation slope agility, the position of a plurality of pulse peak values subjected to pulse compression processing jumps in a distance dimension due to fixed intermittent frequency of the conventional intermittent forwarding, so that the same-order pulse peak value cannot be effectively accumulated among a plurality of pulses, and the intermittent forwarding effect is influenced. Aiming at an LFM radar system with an advanced system of frequency modulation slope agility, an intermittent frequency self-adaptive adjusting method is researched, the pulse peak position does not jump after pulse compression, and the application range of intermittent forwarding can be widened.
[ summary of the invention ]
The technical problem to be solved by the invention is as follows: the provided intermittent frequency self-adaptive adjusting method realizes no jump of pulse peak position after pulse compression under the condition of intermittent forwarding.
The technical scheme adopted by the invention is as follows:
firstly, performing down-conversion on a radar signal to obtain an LFM complex envelope signal;
and intercepting the LFM signal by using a radar receiver, and mixing the LFM signal with a local oscillator signal to realize down conversion to obtain an LFM complex envelope signal which is recorded as u (t).
Secondly, delaying the LFM complex envelope signal to obtain a corresponding delay signal;
and (3) carrying out shunt processing on the LFM complex envelope signal, wherein one path delays for a fixed time delay delta t to obtain a time delay signal u (t-delta t).
Thirdly, mixing the LFM complex envelope signal with a corresponding delay signal and inputting the mixture into a frequency discriminator to obtain a frequency difference;
the complex envelope signal u (t) and the delay signal u (t-delta t) are mixed to obtain
And inputting the signals into a frequency discriminator to obtain the frequency difference delta f (k) of the two signals.
Fourthly, taking the obtained frequency difference as an intermittent frequency, and carrying out intermittent processing on the LFM complex envelope signal;
frequency f of intermittent signal s Setting the frequency difference to be equal to delta f (k), and simultaneously setting the intermittent pulse width according to requirements, thereby obtaining the intermittent control signal p (t | tau, f) s ) Sampling and forwarding of the LFM complex envelope signal u (t) are completed by using the intermittent control signal to form a baseband signal, and the baseband signal is mixed with a local oscillator signal to realize up-conversion, so that a radio frequency signal J (t) is obtained.
The invention has the advantages that:
first, the problem of intermittent frequency adaptive adjustment is solved. And obtaining a frequency difference which linearly changes along with the frequency modulation slope based on the LFM signal and the delay signal frequency discrimination, and taking the frequency difference as an intermittent frequency to realize the self-adaptive change of the intermittent frequency along with the frequency modulation slope.
Second, the adaptive adjustment implementation is simple, and only the LFM signal and its delayed signal need to be mixed and then passed through the frequency discriminator.
Thirdly, the problem of pulse peak position jump formed by intermittent forwarding is solved. The intermittent frequency is changed along with the self-adaptive linearity of the frequency modulation slope, so that the pulse peak position is only related to the delay time of the signal, and the pulse peak position does not jump as long as the delay time is fixed.
[ description of the drawings ]
Fig. 1 is a block diagram of an implementation of intermittent frequency adaptive adjustment.
FIG. 2 (a) is a graph of the peak value of the pulse after three pulses of pulse pressure under the condition of fixed intermittent frequency.
FIG. 2 (b) is a graph showing the peak values of the pulses accumulated after three pulses of pulse pressure under a fixed intermittent frequency.
Fig. 3 (a) is a diagram of the pulse peak after three pulses of pulse pressure when the intermittent frequency is adaptively adjusted.
Fig. 3 (b) is a diagram showing the peak values of the pulses accumulated after three pulses of pulse pressure during the intermittent frequency adaptive adjustment.
[ detailed description ] embodiments
The embodiments of the invention will now be described in detail with reference to the accompanying drawings:
a method for adaptively adjusting the intermittent frequency of an LFM radar with a frequency modulation slope agility comprises the following steps:
firstly, performing down-conversion processing on a radar signal to obtain an LFM complex envelope signal;
let LFM radar signal carrier frequency of radar transmission be f 0 The bandwidth is B, the pulse width of the signal is T, and the LFM signal can be expressed as
Wherein j is unit imaginary number, T is time, e is natural index, and k = B/T is LFM signal frequency modulation slope. Pass and local oscillator frequency of f 0 After the signal mixing realizes down-conversion, the obtained LFM complex envelope signal u (t) is
Secondly, performing time delay on the LFM complex envelope signal u (t) in the first step to obtain a corresponding LFM delay signal;
if the fixed delay is Δ t, the LFM delay signal is
Thirdly, mixing the LFM complex envelope signal u (t) in the first step with the corresponding LFM delay signal u (t-delta t) in the second part to obtain
Then will be
Inputting the frequency discriminator to obtain a frequency difference delta f (k);
where denotes taking the conjugate. d (-) denotes the derivative.
The fourth step is to apply the intermittent frequency f s Setting the frequency difference Δ f (k) equal to that obtained in the third step, forming the intermittent control signal p (t | τ, f) s )；
Setting the intermittent pulse width tau according to the requirement by taking the obtained frequency difference as an intermittent frequency to obtain an intermittent control signal
Wherein
Representing a convolution, n being an integer, f s = Δ f (k), τ is the intermittent pulse width,
denotes an intermittent sampling period, and δ (·) denotes a unit impulse.
And then uses the intermittent control signal p (t | tau, f) s ) Carrying out intermittent processing on the LFM complex envelope signal u (t);
by intermittent control signals p (t | τ, f) s ) After the LFM complex envelope signal u (t) is multiplied to complete intermittent processing, the local oscillator frequency is used as f 0 The signal mixing realizes the up-conversion to obtain a radio frequency signal J (t)
And the radio frequency signal J (t) is forwarded to a radar, so that the linear change of the intermittent frequency of the signal along with the frequency modulation slope of the LFM can be realized. According to the position of the peak of the intermittent forwarding pulse
Where c is the speed of light and n is the same as in equation six, representing the nth order pulse peak. Will f is s Equation of the equation for the peak position of pulse eight is substituted by = k Δ t
Only relevant to the fixed time delay delta t and does not change along with k, thereby ensuring that the position of the pulse peak value does not jump.
As shown in fig. 1, it is a block diagram for implementing intermittent frequency adaptive adjustment. Let the LFM signal pulse length be 100us, and the chirp rates corresponding to the three pulses be k =10 respectively 11 Hz/s、1.2×10 11 Hz/s and 1.3X 10 11 Hz/s. FIG. 2 (a) shows a fixed intermittent frequency f s Under the condition of =0.5MHz, a pulse peak value diagram after three pulse pulses with intermittent pulse width tau =1 us; FIG. 2 (b)Is a graph of the peak values of the pulses accumulated after the three pulses in FIG. 2 (a); fig. 3 (a) shows the intermittent frequency adaptation condition (Δ t =3.33us, f under three pulses) s Automatically adjusted to 0.333MHz, 0.4MHz and 0.5 MHz) pulse pressure; FIG. 3 (b) is a graph of the peak values of the pulses accumulated after the three pulses in FIG. 3 (a). According to the experimental result comparison and analysis shown in the pulse peak value diagram, the intermittent frequency is adaptively adjusted to be a frequency modulation slope linear change function, so that the non-jumping of the intermittent forwarding pulse peak value position is realized, the effective accumulation of the pulse peak value is ensured, and the application range of the intermittent forwarding is improved.
Claims (5)
1. A method for adaptively adjusting the intermittent frequency of an LFM radar with a frequency modulation slope agility is characterized by comprising the following steps:
step one, performing down-conversion on a radar signal to obtain an LFM complex envelope signal;
intercepting the LFM signal by using a radar receiver, and mixing the LFM signal with a local oscillator signal to realize down conversion to obtain an LFM complex envelope signal which is recorded as u (t);
step two, delaying the LFM complex envelope signal to obtain a corresponding delay signal;
the method comprises the steps that an LFM complex envelope signal is subjected to shunt processing, wherein one path delays a fixed time delay delta t to obtain a time delay signal u (t-delta t);
mixing the LFM complex envelope signal with a corresponding delay signal and inputting the mixed signal into a frequency discriminator to obtain a frequency difference;
the complex envelope signal u (t) and the delay signal u (t-delta t) are mixed to obtain
Inputting the signals into a frequency discriminator to obtain the frequency difference delta f (k) of the two signals;
step four, taking the obtained frequency difference as an intermittent frequency, and carrying out intermittent processing on the LFM complex envelope signal;
frequency f of intermittent signal s Setting the frequency difference to be equal to delta f (k), and simultaneously setting the intermittent pulse width according to requirements, thereby obtaining the intermittent control signal p (t | tau, f) s ) Using the intermittent control signalSampling and forwarding of the LFM complex envelope signal u (t) are completed, a baseband signal is formed, and then the baseband signal and a local oscillator signal are mixed to realize up-conversion, so that a radio frequency signal J (t) is obtained.
2. The intermittent frequency adaptive adjustment method of the chirp rate agile LFM radar according to claim 1, wherein: in the first step, the carrier frequency of LFM radar signal emitted by radar is set as f 0 The bandwidth is B, the pulse width of the signal is T, and the LFM signal is expressed as
Wherein j is unit imaginary number, T is time, e is natural index, and k = B/T is LFM signal frequency modulation slope; pass and local oscillator frequency of f 0 After the signal frequency mixing realizes down-conversion, the LFM complex envelope signal u (t) is obtained
3. The intermittent frequency adaptive adjustment method of the chirp rate agile LFM radar according to claim 1, wherein: in the second step, if the fixed delay is Δ t, the LFM delay signal is
4. The intermittent frequency adaptive adjustment method of the chirp rate agile LFM radar according to claim 1, wherein: in the third step, the first step is carried out,
then will be
Inputting the frequency discriminator to obtain a frequency difference delta f (k);
wherein denotes conjugation; d (-) represents the derivative.
5. The intermittent frequency adaptive adjustment method of the chirp rate agile LFM radar according to claim 1, wherein: in the fourth step, the obtained frequency difference is used as an intermittent frequency, and an intermittent pulse width tau is set according to requirements to obtain an intermittent control signal
Wherein
Representing a convolution, n being an integer, f s = Δ f (k), τ is the intermittent pulse width,
represents an intermittent sampling period, δ (·) represents a unit impulse;
by intermittent control signals p (t | τ, f) s ) After the LFM complex envelope signal u (t) is multiplied to complete intermittent processing, the local oscillator frequency is used as f 0 The signal mixing realizes the up-conversion to obtain a radio frequency signal J (t)
The radio frequency signal J (t) is forwarded to a radar, namely, the linear change of the intermittent frequency of the signal along with the frequency modulation slope of the LFM is realized; according to the position of the peak of the intermittent forwarding pulse
Wherein c is the speed of light, and n is consistent with the formula six and represents the peak value of the nth order pulse; will f is s Substituting k Δ t into equation eight, pulse peak position
Only relevant to the fixed time delay delta t and does not change along with k, thereby ensuring that the position of the pulse peak value does not jump.
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| WO2014048193A1 (en) * | 2012-09-28 | 2014-04-03 | 北京理工大学 | Homotype radar co-channel interference suppression method used in ship formation condition |
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