OF THE DISCLOSURE
The present disclosure primarily relates to a radio proximity fuse, and more particularly
to radio proximity fuse that detects target at higher range, rejects jamming and clutter
interference signals and achieves maximum kill of the target.
BACKGROUND
Generally, proximity fuses have been designed as air target intercept system for detecting
target based on the target distance and the time required for reaching the target.
Conventional proximity fuses determine the target distance by using a Frequency
Modulated Continuous wave (FMCW) principle, in which the target distance is measured
based on reflection of a frequency modulated signal having a linearly increasing sweep
frequency. However, the detection of target is very difficult at a short range and the
proximity fuses are subject to the risk of being influenced by undesired disturbing signals
which may cause false detonation.
Further, the transmitting signal leaks to the receiver degrading the system sensitivity.
Furthermore, few typical fuses do not have anti-jam capability since they are usually
narrowband. Moreover, the performance of the fuses degrades due to Radar Cross
Section (RCS) fluctuations of target and lack of clutter rejection capability. Also, the
optimum frequency at which the target must be detonated is estimated beforehand
thereby introducing substantial data errors in the fusing the target. There are many
problems associated with all the prior systems known in the art.
Therefore, there is a need for a radio proximity fuse to overcome the above mentioned
difficulties or problems. Consequently, those skilled in the art will appreciate the present
disclosure that provides many advantages and overcomes all the above and other
limitations.
3
SUMMARY OF THE DISCLOSURE
Accordingly, the present disclosure relates to a method of detecting a target by a radio
proximity fuse, said method comprising transmitting a radio frequency (RF) signal,
modulated with a pseudo random noise (PN) code and receiving the RF signal reflected
from the target after a non-zero time delay. Further, the method comprising performing
correlation and Fourier transform of the received signal with the transmitted RF signal
and detecting target signal upon determining correlation and determining wavelet
transform coefficients of the target signal and estimating a neural frequency based on the
wavelet transform coefficients thus determined and generating a signal to trigger
detonation when the estimated neural frequency is lesser than or equal to a dynamically
determined optimum fusing frequency.
Further, the present disclosure relates to a radio proximity fuse, comprising a code
generator configured to generate a pseudo random noise (PN) code and at least one
transmitter configured to transmit a radio frequency (RF) signal modulated with the
generated random noise code towards the target. The fuse further comprises a receiver
configured to receive and sample the signal reflected from a target and a digital signal
processing unit. The DSP unit comprising a pre-processor operatively coupled with said
receiver and configured to perform correlation and Fourier transform of the sampled
signal with the transmitted RF signal and detect the target signal on successful
correlation; and a processor operatively coupled with said pre-processor and configured
to determine wavelet transform coefficients of the desired target signal, estimate a neural
frequency based on the wavelet transform coefficients and generate a signal to trigger
detonation when the estimated neural frequency is lesser than or equal to a dynamically
determined optimum fusing frequency.
BRIEF DESCRIPTION OF THE DRAWINGS
The disclosure itself, together with further features and added advantages, will become
apparent from consideration of the following detailed description, taken in conjunction
with the accompanying drawings. One or more embodiments of the present disclosure are
4
now described, by way of example only, with reference to the accompanied drawings
wherein like reference numerals represent like elements and in which:
FIG. 1 illustrates a block diagram of a RF module of a Radio proximity fuse (RPF) in
accordance with an embodiment of the present disclosure.
FIG. 2 illustrates a block diagram of a DSP module of the RPF in accordance with an
embodiment of the present disclosure.
FIG. 3a-3b illustrates wave diagram of output signal at receiver and fig. 3c-3d represents
graphical diagram of signal processed by DSP module of the RPF in accordance with an
embodiment of the present disclosure.
FIG. 4 is a flowchart diagram illustrating a method of detecting target by RPF in
accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION
While the disclosure is susceptible to various modifications and alternative forms,
specific embodiment thereof has been shown by way of example in the drawings and will
be described in detail below. It should be understood, however that it is not intended to
limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is
to cover all modifications, equivalents, and alternative falling within the spirit and the
scope of the disclosure.
The terms “comprises”, “comprising”, or any other variations thereof, are intended to
cover a non-exclusive inclusion, such that a setup, device or method that comprises a list
of components or steps does not include only those components or steps but may include
other components or steps not expressly listed or inherent to such setup or device or
method. In other words, one or more elements in a system or apparatus proceeded by
“comprises… a” does not, without more constraints, preclude the existence of other
elements or additional elements in the system or apparatus.
5
Accordingly, the present disclosure relates to a method of detecting a target by a radio
proximity fuse, said method comprising transmitting a radio frequency (RF) signal,
modulated with a pseudo random noise (PN) code and receiving the RF signal reflected
from the target after a non-zero time delay. Further, the method comprising performing 2-
D processing using correlation and Fourier transform of the received signal with the
transmitted RF signal and detecting target signal upon determining correlation and
determining wavelet transform coefficients of the target signal and estimating a neural
frequency based on the wavelet transform coefficients thus determined and generating a
signal to trigger detonation when the estimated neural frequency is lesser than or equal to
a dynamically determined optimum fusing frequency.
In one embodiment of the present disclosure, the PN code is a multiple pulse repetition
frequency (multi-PRF) of PN code for modulating the RF signal.
In another embodiment of the present disclosure, performing the 2-D processing using
correlation and Fourier transform of the received signal comprising acts of: processing
the received signal with the PN code samples, wherein the PN code is time reversed PN
code; removing clutters from the processed signal; comparing the processed signal
amplitude value with an adaptively generated threshold amplitude value of a previous
received signal; and setting a target signal detection flag to indicate detection of the
target, when the amplitude value of the processed signal exceeds the threshold amplitude
value, and the range and relative velocity of the processed signal is within predetermined
target range and relative velocity limits.
In yet another embodiment of the present disclosure, the clutter signal is detected when
the range value and relative velocity of the processed signal exceeds the predetermined
target range and target velocity.
In still another embodiment of the present disclosure, the optimum fusing frequency is
determined based on target characteristics parameter values received dynamically from
an externally connected guidance radar system.
In another embodiment of the present disclosure, realizing the transmitter and receiver
using multi-function MMIC chips.
6
Further, the present disclosure relates to a radio proximity fuse, comprising a code
generator configured to generate a pseudo random noise (PN) code and at least one
transmitter configured to transmit a radio frequency (RF) signal modulated with the
generated random noise code towards the target. The fuse further comprises a receiver
and a digital signal processing unit. The receiver is configured to receive the signal
reflected from a target after a non-zero time delay. The DSP unit comprising a preprocessor
operatively coupled with said receiver and configured to perform 2-D
processing using correlation and Fourier transform of the sampled signal with the
transmitted RF signal and detect the target signal on successful correlation; and a
processor operatively coupled with said pre-processor and configured to determine
wavelet transform coefficients of the desired target signal, estimate a neural frequency
based on the wavelet transform coefficients and generate a signal to trigger detonation
when the estimated neural frequency is lesser than or equal to a dynamically determined
optimum fusing frequency.
In one embodiment of the present disclosure, the pre-processor is realized using Field
Programmable Gate Array (FPGA).
In another embodiment of the present disclosure, the transmitter and receiver are realized
using multi-function MMIC chips.
In yet another embodiment of the present disclosure, the transmitter MMIC comprises
coupler, amplifier, mixer and power divider circuit and wherein the receiver MMIC
comprises low-noise amplifier and mixer circuit.
In still another embodiment of the present disclosure, the code generator is configured to
generate a pulse repetition frequency (PRF) of PN code for modulating transmitter signal.
7
In yet another embodiment of the present disclosure, the said code generator including a
timing control circuit configured to generate multiple pulse repetition frequency of PN
code at regular intervals of time.
In one embodiment of the present disclosure, the pre-processor is configured to: process
the received signal samples with the PN code samples, wherein the PN code is time
reversed PN code; remove clutters from the processed signal; compare the processed
signal amplitude value with an adaptively generated threshold amplitude value of
previous received signal; and set a target signal detection flag to indicate detection of the
target, when the amplitude value of the processed signal exceeds the threshold amplitude
value, and, the range and relative velocity of the processed signal is within predetermined
target range and relative velocity limits.
In another embodiment of the present disclosure, prior to processing the received signal,
the pre-processor is configured to detect the clutter signal when the range value and
relative velocity of the processed signal exceeds the predetermined target range and
target velocity.
In yet another embodiment of the present disclosure, the said processor is configured to
predetermine an optimum fusing frequency based on target characteristics values
received dynamically from an externally connected guidance radar system.
In still another embodiment of the present disclosure, a RF Source unit coupled with at
least one transmitter and configured to provide RF Signal to the proximity fuse.
In the following detailed description of the embodiments of the disclosure, reference is
made to the accompanying drawings that form a part hereof, and in which are shown by
way of illustration specific embodiments in which the disclosure may be practiced. These
embodiments are described in sufficient detail to enable those skilled in the art to practice
the disclosure, and it is to be understood that other embodiments may be utilized and that
changes may be made without departing from the scope of the present disclosure. The
following description is, therefore, not to be taken in a limiting sense.
8
The present disclosure relates to a radio proximity fuse (RPF) and a method of detecting
target using the proximity fuse. The RPF comprises a Transceiver or RF module (100)
and a Digital signal processing (DSP) module (200) operatively coupled to each other
and configured to detect the target and determine an optimum fusing frequency at which
the target is detonated.
FIG. 1 illustrates a block diagram of a RF module of a Radio proximity fuse (RPF) in
accordance with an embodiment of the present disclosure.
According to the present disclosure, a RF module (100) as shown in fig.1 is designed
using RF MMIC chips to reduce number of connectors and interconnecting cables for
achieving better isolation between the transmitter and receiver of the transceiver and
improving reliability and repeatability of the system.
In one embodiment, the RF module (100) comprises a transmitter (102) operatively
configured to transmit RF code modulated signals via one or more transmitting antennas
106-A, 106-B towards the target, and further comprises a receiver (104) operatively
configured to receive the reflected or echoed signals from the target through receiving
antenna (108). The transmitter (102) and the receiver (104) can be realized using multifunction
MMIC chips to achieve isolation, repeatability and reliability of the system.
The transmitter (102) is operatively coupled to receive an input radio frequency (RF)
signal from a RF Source (110). The RF Source (110) comprises a Dielectric resonating
oscillator that is configured to generate the RF signal for feeding as input to the
transmitter (102).
The transmitter MMIC (102) comprises a decoupler (112), an amplifier (114), a mixer
(118) and a power divider circuit (120). The coupler is configured to couple power from
RF source to the transmitter and supply one part of the RF signal to the local oscillator
(LO) port of the mixer in the receiver (104). The RF signal is then amplified by the
amplifier (114) to increase the power of the signal suitable for transmission.
9
The RF signal is then modulated with a Pseudo random noise (PN) code (116) generated
by a code generator in Pre-processor to generate a PN code modulated RF signal. In one
embodiment, the code generator is configured to generate a multiple pulse repetition
frequency (multi-PRF) code for modulating the RF signal. The code generator (116) is
further configured to vary the PN code (116) in every cycle of PN sequence so that the
PN code (116) cannot be detected by the target and thereby avoiding hacking of the
transmitted signal by the target. The PN code modulated RF signal is then fed to the
mixer (118) and the power divider circuit (118) to generate a modulated RF signal for
transmission via the antennas 106-A and 106-B. The RF signal in digital form is
converted to analog RF signal and then transmitted towards the target.
The receiver (104) is configured to receive the signal reflected from the target to
determine validity of the reflected signal. The receiver (104) determines the delay
between transmission of the RF signal and the reception of the reflected signal and rejects
the reflected signal if the delay is determined to be zero, thus, achieving the isolation
between the transmitter (102) and the receiver (104) and enhancing the performance of
the system. By means of rejecting zero delay signals, the leakage of the transmitted signal
to the closely located receiver is prevented.
The receiver MMIC (104) comprises a low-noise amplifier (LNA) (122) and mixer
circuit (124). The LNA (122) is configured to receive the signal reflected or echoed from
the target, and filter the unnecessary and unwanted jamming and noise or interference
signals. The filtered signal is then fed to the radio frequency (RF) port of the mixer (124).
As the transmitted RF signal has a time varying property, this property of the received
signal will be different from that of the transmitted signal by an amount dependant on the
rate at which the property of the RF signal varies and the time it takes for the RF signal to
travel between the antenna to the target or the ground and back. As the time it takes for
the RF signal to travel between the antenna to the target or the ground and back is
directly related to the distance or proximity of the antenna from the ground or the target,
the difference between the transmitted and received signal can be used to generate a
range signal indicative of the distance between the fuse and the ground or target.
10
The mixer (124) generates an intermediate frequency (IF) output signal which is
representative of the difference between the frequencies of the transmitted signal at LO
port and received signal (LO) ports. The IF output signal is then fed to the DSP module
(200) for further processing.
FIG. 2 illustrates a block diagram of a DSP module of the RPF in accordance with an
embodiment of the present disclosure.
The DSP module (200), as shown in fig.2, is designed using Field Programmable Gate
Array (FPGA) and DSP processor chips. The DSP module (200) comprises a differential
amplifier (202), an anti-aliasing filter (204), an analog-to-digital converter (ADC), a preprocessor
(208) and a DSP processor (210) operatively connected and configured to
detect the target and determine an optimum frequency to detonate the target.
The pre-processor (208) comprises a PN code generator (212) to generate a Pseudo
random noise (PN) code (116) that is modulated with the transmitted signal to generate a
PN code modulated RF signal. In one embodiment, the code generator (212) is
configured to generate a multiple pulse repetition frequency (multi-PRF) code and
provide the same as input to the mixer (118) of the RF module (100) for modulating the
RF signal. The code generator (212) is further configured to vary the PN code (116) in
every cycle of PN sequence so that the PN code cannot be detected by the target and
thereby avoiding hacking of the transmitted signal by the target.
The reflected signal from the target is received, down converted, amplified, filtered and
sampled before the actual detection of target. The differential amplifier (202) is
configured to receive the IF signal and amplify to increase the power of the signal
suitable for further processing. The amplified IF signal is then fed to the anti-aliasing
filter (204) that is configured to filter the IF signal so as to restrict the bandwidth of the IF
signal to fall within a predetermined bandwidth rate before sampling by the pre-processor
(208). The filtered IF signal in analog form is then converted to its digital counterpart by
11
the ADC (206). The ADC (206) converts the IF analog signal into a corresponding digital
signal for further processing by the pre-processor (208) and DSP (210).
In one embodiment, the pre-processor (208) is realized using FPGA and can be
configured to meet the requirement of RPF system with different specifications. The preprocessor
(208) is configured to receive the IF signal and determine the range and
velocity of the target. As the time it takes for the RF signal to travel between the antenna
to the target or the ground and back is directly related to the distance or proximity of the
antenna from the ground or the target, the difference between the transmitted and
received signal can be used to generate a range signal indicative of the distance between
the fuse and the ground or target. In one example, the pre-processor (208) determines the
range of target of 150m with ±0.75m accuracy.
The pre-processor (108) is configured to perform digital 2-D processing of the IF signal
using correlation with the transmitted RF signal and then Fourier transforming the IF
signal. To perform the 2-D processing technique, the pre-processor (208) is configured
to sample the IF signal with the PN code samples. In one embodiment, the PN code
samples are time reversed PN code samples of transmitted signal, Correlated with IF
signal samples and then the IF signal samples are subjected to FFT. After FFT process,
determination of clutter signals is performed. The pre-processor (108) is configured to
determine the clutter signal when the range and Doppler value of the received IF signal
exceeds a predetermined range and Doppler value. If the range of the IF signal does not
exceed the predetermined range and Doppler value, then the received IF signal is
considered as a valid, non-clutter signal and then processed further.
The pre-processor (208) is further configured to determine target detection by comparing
the amplitude value of the IF signal with an adaptively generated threshold value. The
adaptive threshold value is determined based on the amplitude of a previously received
signal and the amplitude of the present IF signal. If the amplitude of the IF signal is
determined to exceed the adaptive threshold value, and when the amplitude and relative
velocity of the processed signal is within predetermined target range and relative velocity
12
limits, the pre-processor (208) determines the target detection and sets a target signal
detection flag as TRUE.
The processor (210) is configured to receive the samples of IF signal and further
processes the signal when the target signal detection flag is set as TRUE. The processor
(210) is further configured to determine a neural fusing frequency and generate a firing
pulse flag signal when the neural frequency exceeds a predetermined optimum fusing
frequency. The processor (210) performs wavelet transformation using Morlet wavelets
on the received IF signals and generate wavelet transform coefficients. The coefficients
are used in a trained neural network for estimating the exact neural frequency.
The processor (210) is further configured to compare the neural frequency with a
predetermined optimum fusing frequency and generate a firing pulse enable/flag signal
when the neural frequency is less than or equal to the optimum fusing frequency. If the
neural frequency is determined to be greater than the optimum fusing frequency, then the
processor (210) re calculates the wavelet transformation coefficients for a predetermined
time period. The optimum fusing frequency is predetermined based on target
characteristics parameter values received from an externally connected guidance radar
system. The optimum fusing frequency is predetermined based on target characteristics
parameters such as interrupt velocity, target velocity and crossing angle between intercept
vehicle missile and target.
The processor (210) is also configured to compute the time to generate the fire enable
signal so that maximum number of fragments hit the target and achieve maximum kill of
the target. The time for fusing is calculated based on one or more parameters including
range of the target, the Doppler frequency variation over time as the relative velocity
between the RPF and target changes, fragment velocity and density along a particular
direction, dynamic variation of mean ejection angle of fragments and the approach angle
of target with respect to the intercept vehicle. The time for processing one batch of data
in DSP processor is 0.2 ms.
After generating the firing pulse enable signal, the processor (210) provides the enable
flag signal to the pre-processor (208) which in turn provides the flag signal to a
13
detonation circuit. The detonation circuit receives the firing pulse flag signal and
detonates the circuit thereby firing the fragments towards the target and achieving
maximum kill of the target.
The RPF as described in the above paragraphs is configured to withstand the environment
factors such as random vibration having 0.014g2/Hz, acceleration of 35g and temperature
in the range of -40ºC to +71ºC. Further, the RPF is configured to operate under thermal
shock, tropical heating, shock, bump, and saline atmosphere.
FIG. 3a-3b illustrates wave diagram of output signal at receiver and fig. 3c-3d represents
graphical diagram of signal processes by DSP module of the RPF in accordance with an
embodiment of the present disclosure.
The signal reflected from the target including Doppler modulated coded signal is shown
in fig. 3a, and the reflected signal that is received at the receiver, matched and filtered is
shown in fig.3b. Further, fig. 3c indicate the correlation of the received signal with the
transmitted signal illustrating a range-Doppler mapping and fig. 3d represents the time
diagram at which the firing pulse is provided as output.
FIG. 4 is a flowchart diagram illustrating a method of detecting target by RPF in
accordance with an embodiment of the present disclosure.
The flowchart as illustrated in fig. 4 depicts the method performed by the DSP module
(200) of the RPF to detect the target and generate a firing pulse flag signal to trigger the
detonation of the warhead fragments.
At block 405, reflected signal from target is received. In one embodiment, the RF signal
that was transmitted towards the target is reflected or echoed and received at the receiver
of the RPF. At the receiver, the signal is received, down converted, amplified, filtered
and sampled before the actual detection of target.
At block 410, digital correlation and FFT is performed. In one embodiment, the preprocessor
(208) is configured to perform 2-D processing using digital correlation of the
IF signal with the transmitted RF signal and then Fourier transforming the IF signal on
14
successful correlation. To perform the 2-D processing using digital correlation, the preprocessor
(208) samples the IF signal with the PN code where the PN code samples are
time reversed PN code samples of the transmitted signal, correlated with IF signal
samples and, then the IF signal samples are subjected to FFT.
At block 415, determination of signal beyond predetermined range. In one embodiment,
the pre-processor (208) is configured to compare the amplitude of the signal samples with
a predetermined range value to determine clutter signals. Based on the comparison, if the
signals samples are beyond the predetermined range and Doppler value, then the method
flows towards a ‘YES’ path to block 420; otherwise, the method flow towards a ‘NO’
path to block 425.
At block 420, clutter signal is determined. In one embodiment, if the received signal
amplitude is determined to be greater than the predetermined range value and Doppler
value, then the received signal is a clutter signal that must be rejected by the preprocessor
(208) .
At block 425, target detection is performed and target signal detection flag is set based on
detection. In one embodiment, if the received signal amplitude is determined to be within
the predetermined range, then the received is a valid non-clutter signal received from the
target. The pre-processor (208) determines target detection by comparing the amplitude
value of the IF signal with an adaptively generated threshold value. The adaptive
threshold value is determined based on the amplitude of a previously received signal and
the amplitude of the present IF signal. If the amplitude of the IF signal is determined to
exceed the adaptive threshold value, and, when the range and relative velocity of the
processed signal is within predetermined target range and relative velocity limits, the preprocessor
(208) determines the target detection and enables a target signal detection flag
as TRUE.
At block 430, wavelet transform is performed. In one embodiment, the processor (210) is
configured to receive the samples of IF signal and further process the signal when the
target signal detection flag is set as TRUE. The processor (210) performs wavelet
transformation on the received IF signals to generate wavelet transform coefficients. The
15
processor (210) performs wavelet transformation using Morlet wavelets on the received
IF signals and generate wavelet transform coefficients.
At block 435, neural frequency is estimated. In one embodiment, the processor (210) is
configured to determine the neural frequency based on wavelet transform coefficients
thus generated at block 430. The coefficients are used in a trained neural network for
estimating the exact neural frequency. Furthermore, the processor (210) is configured to
compute the time to generate the firing pulse enable signal so that maximum number of
fragments hit the target and achieve maximum kill of the target. The time for fusing is
calculated based on one or more parameters that is independent of RCS fluctuations such
as range of the target, the Doppler frequency variation over time as the relative velocity
between the RPF and target changes, fragment velocity and density along a particular
direction, dynamic variation of mean ejection angle of fragments and the approach angle
of target with respect to the intercept vehicle. The time for processing each batch of data
is 0.2 ms.
At block 440, parameters of the moving target are received. In one embodiment, the
processor (210) receives one or more target characteristics parameter values from an
externally connected guidance radar system. For example, the target characteristics
parameters may include interrupt velocity, target velocity and crossing angle.
At block 445, an optimum fusing frequency is determined. In one embodiment, the
processor (210) is configured to determine the optimum fusing frequency based on the
one or more target characteristics parameter values received from the externally
connected guidance radar system.
At block 450, the neural frequency is compared with the predetermined optimum fusing
frequency. In one embodiment, the processor (210) compares the neural frequency
estimated at block 435 with the optimum fusing frequency predetermined at block 445. If
the neural frequency is greater than the optimum fusing frequency, then the method flow
towards the ‘YES’ path to block 430; otherwise it flows to block 455.
16
At block 455, a firing flag signal is generated. In one embodiment, the processor (210)
determines that the neural frequency is not greater than the optimum fusing frequency by
the ‘NO’ path and generates a firing flag signal to trigger the detonation. After generating
the firing pulse flag signal, the processor (210) provides the enable flag signal to the preprocessor
(208) which in turn provides the flag signal to a detonation circuit. The
detonation circuit receives the firing pulse flag signal and detonates the circuit thereby
firing the fragments towards the target and achieving maximum kill of the target.
ADVANTAGES OF THE PRESENT DISCLOSURE
1. Achieves anti-jamming and clutter rejection capabilities.
2. A wideband design is adopted to make the system immune to counter-measures.
3. Avoids interference and jamming of signals.
4. Detection criteria are independent of RCS fluctuations.
5. Low volume, less weight and easy to manufacture.
6. Involves less manufacturing and operating cost.
7. Dynamic estimation of time and frequency is implemented to avoid substantial
errors that occur due to pre-estimation.
The foregoing detailed description has described only a few of the many possible
implementations of the present disclosure. While considerable emphasis has been placed
herein on the particular features of this disclosure, it will be appreciated that various
modifications can be made, and that many changes can be made in the preferred
embodiments without departing from the principles of the disclosure. These and other
modifications in the nature of the disclosure or the preferred embodiments will be
apparent to those skilled in the art from the disclosure herein, whereby it is to be
distinctly understood that the foregoing descriptive matter is to be interpreted merely as
illustrative of the disclosure and not as a limitation.

We Claim:
1. A method of detecting a target by a radio proximity fuse, said method comprising:
transmitting a radio frequency (RF) signal, modulated with a pseudo random
noise (PN) code;
receiving the RF signal reflected from the target after a non-zero time delay;
performing 2-D processing using correlation and Fourier transform of the
received signal with the transmitted RF signal and detecting target signal upon
determining correlation;
determining wavelet transform coefficients of the target signal and estimating a
neural frequency based on the wavelet transform coefficients thus determined; and
generating a signal to trigger detonation when the estimated neural frequency is
lesser than or equal to a dynamically determined optimum fusing frequency.
2. The method as claimed in claim 1, wherein the PN code is a multiple pulse
repetition frequency (multi-PRF) of PN code for modulating the RF signal.
3. The method as claimed in claim 1, wherein performing the 2-D processing using
correlation and Fourier transform of the received signal comprising acts of:
processing the received signal with the PN code samples, wherein the PN code is
time reversed PN code;
removing clutters from the processed signal;
comparing the processed signal amplitude value with an adaptively generated
threshold amplitude value of a previous received signal; and
setting a target signal detection flag to indicate detection of the target, when the
amplitude value of the processed signal exceeds the threshold amplitude value, and, the
range and relative velocity of the processed signal is within predetermined target range
and relative velocity limits.
4. The method as claimed in claim 3, wherein the clutter signal is detected when the
range value and relative velocity of the processed signal exceeds the predetermined target
range and target velocity.
18
5. The method as claimed in claim 1, wherein the optimum fusing frequency is
determined based on target characteristics parameter values received dynamically from
an externally connected guidance radar system.
6. A radio proximity fuse, comprising:
a code generator (212) configured to generate a pseudo random noise (PN) code
(116);
at least one transmitter (102) configured to transmit a radio frequency (RF) signal
modulated with the generated random noise code towards the target;
a receiver (104) configured to receive the signal reflected from a target after a
non-zero time delay; and
a digital signal processing unit (200) comprising:
a pre-processor (208) operatively coupled with said receiver and
configured to perform 2-D processing using correlation and Fourier transform of
the sampled signal with the transmitted RF signal and detect the target signal on
successful correlation; and
a processor (210) operatively coupled with said pre-processor and
configured to determine wavelet transform coefficients of the desired target
signal, estimate a neural frequency based on the wavelet transform coefficients
and generate a signal to trigger detonation when the estimated neural frequency is
lesser than or equal to a dynamically determined optimum fusing frequency.
7. The proximity fuse as claimed in claim 6, wherein the pre-processor is realized
using Field Programmable Gate Array (FPGA).
8. The proximity fuse as claimed in claim 6, wherein the transmitter and receiver are
realized using multi-function MMIC chips.
9. The proximity fuse as claimed in claim 8, wherein the transmitter MMIC comprises
coupler, amplifier, mixer and power divider circuit and wherein the receiver MMIC
comprises low-noise amplifier and mixer circuit.
19
10. The proximity fuse as claimed in claim 6, wherein the code generator is configured
to generate a pulse repetition frequency (PRF) of PN code for modulating transmitter
signal.
11. The proximity fuse as claimed in claim 6, wherein the said code generator including
a timing control circuit configured to generate multiple pulse repetition frequency of PN
code at regular intervals of time.
12. The proximity fuse as claimed in claim 6, wherein the pre-processor is configured
to:
process the received signal samples with the PN code samples, wherein the PN
code is time reversed PN code;
remove clutters from the processed signal;
compare the processed signal amplitude value with an adaptively generated
threshold amplitude value of previous received signal; and
set a target signal detection flag to indicate detection of the target, when the
amplitude value of the processed signal exceeds the threshold amplitude value, and, the
range and relative velocity of the processed signal is within predetermined target range
and relative velocity limits.
13. The proximity fuse as claimed in claim 12, wherein prior to processing the received
signal, the pre-processor is configured to detect the clutter signal when the range value
and relative velocity of the processed signal exceeds the predetermined target range and
target velocity.
14. The proximity fuse as claimed in claim 6, wherein the said processor is configured
to predetermine an optimum fusing frequency based on target characteristics values
received dynamically from an externally connected guidance radar system.
15. The proximity fuse as claimed in claim 6, including a RF Source unit coupled with
at least one transmitter and configured to provide RF signal to the proximity fuse.