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IET Communications (17518628)19(1)
This paper investigates the momentary extraction of a part of the frequency components of the signal resulting from the frequency modulation process. Based on this analysis, a new method for extracting frequency information is proposed. The changes of the instantaneous periods of the FM signal are investigated, and a simple method to determine the instantaneous frequency of the signal in the time domain is proposed. The proposed method was evaluated through simulations and compared against conventional FM demodulation techniques. In similar SNR, the relative error power of the proposed method is approximately 2 dB less than other conventional types of FM demodulators. © 2025 The Author(s). IET Communications published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
IET Communications (17518628)18(17)pp. 993-1001
This paper investigates the changes in the waveform of a sinusoidal carrier resulting from amplitude modulation (AM) process. Based on this analysis, a novel method for extracting amplitude information is proposed. The proposed method uses the behaviour of the amplitude limitation which does not significantly affect the slope of the sinusoidal signal near zero crossing points. A simple comparator is used to convert the changes in sinusoidal slope near zero crossing points into pulse width changes. A simple circuit is proposed which keeps the output pulse width of the comparator constant by a simple control loop. The accuracy of the method is evaluated through simulation and is experimentally tested. If the modulation index is high and the amplitude of the input signal to the detector is limited, the proposed method can yield up at least 9 dB improvement in relative error power. However, if the modulation index is small, the improvement in relative error power can be at least 35 dB compared to other conventional types of AM demodulators. © 2024 The Author(s). IET Communications published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
IET Science, Measurement and Technology (17518822)17(9)pp. 351-360
Low-frequency noise, generated inherently by the number or mobility fluctuation of carriers, is a crucial concern for the design of analog and digital circuits. Unified modelling based on experimental validation of near-DC noise in amplifiers is a long-standing open problem. This article develops a model for low-frequency noise by deriving new bounds for carrier capturing and releasing. According to the proposed model, a measurement system is suggested that operates in a wide frequency range and even at very low frequencies. The system is noise-tolerant, since the amplifier is selected based on acceptable noise levels. Among the advantages are the independence from specialized structural noise models for each component and the low cost of the measurement system. The evaluation results show that the proposed method leads to a promising improvement in the low-frequency noise measuring and is superior to conventional models in the normalized root mean square error indicator. Findings reveal that the proposed measurement method can estimate the flicker noise around the DC frequency, and the proposed model agrees reasonably with the proposed measurement circuit. © 2023 The Authors. IET Science, Measurement & Technology published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
Biomedical Signal Processing and Control (17468108)80
Biomedical signals are frequently contaminated by colored noise; consequently, noise recognition and reduction are critical to biomedical systems. Conventional techniques have not been sufficiently focused on noise classification and using dominant noise, which facilitates noise recognition and reduction. In addition, the dependence of previous methods on threshold and calibration parameters decreases the performance of noise reduction methods. Hence, this paper enriches empirical mode decomposition (EMD) by dominant noise and presents an adaptive denoising method based on deep learning. The proposed method first identifies the dominant noise using mode decomposition and a two-step long short-term memory (LSTM) deep classifier. Then, detected intrinsic features are used for noise-aided mode decomposition. Finally, denoising is adaptively performed using the most relevant components to the dominant noise. This method is capable of accurately classifying and suppressing white and colored noise. The proposed method is validated by ECG and audio datasets. The evaluation results show that the suggested method leads to a promising improvement in noise classification, moreover, noise reduction is superior to the conventional methods in terms of SNR and RMSE criteria. As a result, the suggested method can impact noise reduction performance in real-world applications by utilizing dominant noise detection. © 2022 Elsevier Ltd
IEEE Transactions on Aerospace and Electronic Systems (00189251)56(6)pp. 4723-4733
The effect of jammer on radar or jamming performance has been and is being assessed on the basis of range reduction where consistency in tracking target ability is more important than range reduction in a tracking radar. A new criterion known as relative radar functionality destruction time is defined and introduced as the relative of functionality destruction time of radar to one period of jammer, where jammer signal and target echo power are of concern. The effective parameters in relative time of the receiver functioning destruction are assessed. Next, this criterion is applied in the assessment of simple conical scan radar receiver against a conventional jamming (sweep noise jamming). This criterion is modeled and simulated on a search radar in the jamming environment where the minimum required standard deviation of noise for destroying the radar function yields. By implementing the structure of a frequency modulated continuous wave tracking radar structure, a simple target based on digital radio frequency memory method and one type of jamming against this radar in a simultaneous manner, the functionality destruction is extracted for different radar parameters. This new criterion on outperforms its counterparts. © 1965-2011 IEEE.
Multidimensional Systems And Signal Processing (15730824)30(1)pp. 93-117
An anti-deception jamming technique is proposed for moving target indication in a pulse-Doppler (PD) radar. The deceive targets are produced by digital radio frequency memory, which tries to pull off the range and velocity gates of real targets. Similar to orthogonal frequency division multiplexing, we use different sets of orthogonal sub-carriers in consecutive coherent pulse intervals (CPIs). By changing sub-carriers in different CPIs, we show that the deceive targets appear as interference in receiving signals. The generalized likelihood ratio test is used for detection and discrimination of real targets. The performance of the proposed method is achieved analytically and by simulations. Furthermore, we implement a hardware block using a TMS6416-DSK DSP for a PD radar prototype exploiting the proposed algorithm to deception discrimination. The presented results demonstrate the good accordance with theoretical predictions. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
Analog Integrated Circuits and Signal Processing (09251030)100(1)pp. 193-198
In this letter, the effects of number of quantization levels are studied in the airborne digital radio frequency memory (DRFM). The artificial signal, produced by DRFM, has quantized amplitude that results in different cross-correlations (with respect to the real target echo signal), when correlated by continuous reference signal. The proposed method includes a technique to release from the estimation of amplitude fluctuations. Then, a closed-form expression is presented for likelihood ratio test discrimination. Simulation results prove the efficiency and robustness of the proposed method. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
Signal, Image and Video Processing (18631711)11(6)pp. 1025-1032
In this article, the effects of the number of quantization levels and the sampled signal are considered in the airborne digital radio frequency memory (DRFM). A different model of analog-to-digital conversion is proposed. The histogram of the proposed model is utilized to release synchronization of signals for integration. Then, the local variance technique is used to highlight the differences between a continuous signal and the sampled pre-quantized DRFM signal. Furthermore, the effects of analog reconstruction filter on a DRFM signal are considered. Simulation results show the efficiency and robustness of the proposed method. Finally, a hardware implementation is provided to prove the proposed method. © 2017, Springer-Verlag London.
IEEE Access (21693536)5pp. 11455-11467
In this paper, the effects of phase noise difference in receiving signals are introduced to discriminate targets. Oscillators and signal sources have their own phase noise levels and specific patterns. This property can be used for discriminating a real target from the airborne digital radio frequency memory (DRFM) in continuous wave tracking radar sensor networks with linear frequency modulation. A simulated signal made through complex circuits by DRFM has higher phase noise with different patterns. To investigate the phase noise level of oscillators, a system is provided to measure the phase noise. Then, the probability of detection ( P-{D} ) and the probability of false alarm ( P-{fa} ) can be achieved by defining an appropriate threshold to evaluate the performance of discriminating between real targets and DRFM targets. The phase noise powers are measured through the same sets of circuits and coherent time periods in various radar sensor systems. To control the amplitude fluctuation of the received signal, the normalization of signal phase power is defined in phase noise bandwidths. The likelihood ratio test is used for target discrimination by a threshold level to achieve the minimum P-{fa} of target discrimination. The proposed method has a simple structure without any additional complexities, and is easily compatible with common radar systems. Two real DRFM systems are used to evaluate the performance of the proposed method in both the L-band and X-band frequencies. The presented results are investigated in different ranges, Doppler frequencies, signal-to-noise ratios, and signal-to-jammer ratios. The experimental results prove the capability of proposed method in radar sensor networks. © 2013 IEEE.
Chinese Optics Letters (16717694)15(10)
In this Letter, a method based on the effects of imperfect oscillators in lasers is proposed to distinguish targets in continuous wave tracking lidar. This technique is based on the fact that each lidar signal source has a specific influence on the phase noise that makes real targets from the false ones. A simulated signal is produced by complex circuits, modulators, memory, and signal oscillators. For example, a deception laser beam has an unequal and variable phase noise from a real target. Thus, the phase noise of transmitted and received signals does not have the same power levels and patterns. To consider the performance of the suggested method, the probability of detection (PD) is shown for various signal-to-noise ratios and signal-to-jammer ratios based on experimental outcomes. © 2017 Chinese Optics Letters.
Electronics Letters (1350911X)53(12)pp. 808-810
By using the effects of non-ideal oscillators, a technique is proposed to discriminate targets in continuous wave (CW) tracking radar. This method is based on the fact that each oscillator has an individual effect on the phase noise that helps to recognise real targets from the simulated ones. A simulated fake target, made through complex circuits, e.g. a digital RF memory, has a different phase noise from a real backscatter. Therefore, the transmitted and received signals are different in phase noise levels and patterns. To evaluate the performance of the proposed technique, the probability of detection (PD) is shown in different signal-to-noise ratios, ranges, and signal-tojammer ratios based on an experimental setup. © The Institution of Engineering and Technology.
In recent decades, S-parameters have been used to model the Linear High Frequency Amplifier behavior. Using the S-parameter, the source and load reflection coefficient can be calculated, which is useful for designing the Input and Output matching network in linear amplifier. The S-parameter cannot model the behavior of the nonlinear amplifiers. X-parameter were introduced to modeling nonlinear amplifier behavior. In this paper we introduce a new algorithm and simulated based on the X-parameter analytical computations, whose purpose is to achieve an optimum load reflection coefficient to minimize the output second harmonic power and increase the dynamic range of a nonlinear amplifier. © 2016 IEEE.
IEEE Transactions on Microwave Theory and Techniques (15579670)64(11)pp. 3492-3500
In the last decades, several analytical approaches for linear RF modeling and design have been introduced. In general, using these approaches, source and load reflection coefficients are calculated for designing input and output matching networks. This reflection coefficient is set to achieve a specific target such as maximum output power and minimum noise or an intermediate condition. The most common linear design approach is the use of S-parameters. However, S-parameters cannot model the nonlinear behavior of amplifiers. Nonlinear RF systems such as power amplifiers are typically designed using nonlinear models and/or load-pull measurements. Recently, X-parameters have been presented to model nonlinear device behavior. In this paper, a new design approach based on X-parameters has been introduced and will be verified by simulations and experimental results. Also, it will be indicated that this method speeds up the design procedure when compared with the load-pull method. Using this approach, we can calculate the load reflection coefficient at the fundamental frequency for minimizing a specific harmonic output power. Finally, the application of this approach in minimizing a specific harmonic in the output signal and increasing the dynamic range of the amplifier will be investigated. © 2016 IEEE.
In this paper, we address the problem of direction-of-arrival (DOA) estimation using a novel spatial sampling scheme based on difference set (DS) codes, called DS-spatial sampling. It is shown that the proposed DS-spatial sampling scheme can be modeled by a deterministic dictionary with minimum coherence. We also develop a low complexity compressed sensing (CS) model for DOA estimation. The proposed methods can reduce the number of array elements as well as the number of receivers. Compared with the conventional DOA estimation algorithm, the proposed sampling and processing method can achieve significantly higher resolution. © 2015 IEEE.
A deception jamming recognition method is proposed based on Adaptive Kernel Local Fisher Discriminant Analysis. The digital radio frequency memory (DRFM) in jammer creates multiple repeat false targets, are commonly utilized in practical applications for limitation of defense radar tracking and discrimination unit. So as to face with decision scheme groups of discriminating among targets and RGPO signals, an analytic form of the embedding transformation and the solution is resorted which can be simply calculated by solving a generalized eigenvalue problem. The practical utility and scalability of the LFDA algorithm can diminish non-linear dimensionality states by applying the kernel trick. The experimental consequences demonstrate that the probability of recognition accuracy performance of the proposed KLFDA in RGPO deception jamming algorithm is greater than 90% when SNR is higher than 4dB. © 2015 IEEE.
In this paper a new method is introduced for evaluating effect of sweep noisy barrage jammer on tracking radars. In this method, jammer interfering energy that injected in radar receiver bandwidth is calculated during jammer scan period, then according to the minimum signal to jammer power ratio that is required for receiver proper functioning (kJα), ratio of receiver proper functioning time to the jamming scan period or ratio of receiver destruction time to the jammer scan period is determined. These parameters are more important than only presence of jammer in receiver bandwidth. We define new performance criteria to evaluate the jammer effect on tracking radars. This is done by considering ratio of receiver destruction time to jammer scan period and the ratio of received power from the jammer to received power from the target at receiver front end. © 2014 IEEE.
