Dual Function Radar and Communication Signal Design with Combined Waveform Selection and Pulse Repetition Interval Agility

During radar operation, changes in the radar cross section (RCS) of a target have an adverse effect on the radar detection performance. In particular, the RCS of a target with high maneuvering characteristics can be changed rapidly. Therefore, a precise prediction of the RCS change is essential for satisfactory radar detection performance. In this study, a modeling and simulation (M&S) tool was developed for the estimation of radar detection performance. The M&S tool comprises a radar model, target model, and wave propagation model. In particular, pre-obtained RCS simulation data were utilized to consider the effect of the RCS change of the target. Using the developed tool, the RCS based on the relative attitude is extracted from the RCS simulation data and the RCS processed data using the moving average method. The M&S model is verified by comparing the two test results with the radar received signal power. Consequently, we verified that when using the RCS manufacturing data, the signal power is more similar to the test data than the other RCS simulation methods. It is expected that the radar performance on the high-maneuvering target can be estimated using the developed M&S tool.

Cognitive radar has the ability to perceive the environment and target information, and complete the work state optimization through analysis and decision. Radar's behavior is defined as all the characteristics of a radar's performance and the process of changing its state according to the law of change and the external influences. In this paper, the adaptive selection behavior principle of radar emission waveform is firstly described. Then, for the waveform adaptive selection behavior, a black box model is constructed by using neural network. The environment, target characteristics and waveform parameters are used as input training data, and the waveform selection result is taken as output. By learning the training waveform selection process of the radar, we will obtain a neural network model with the same capabilities as the radar adaptive waveform selection system, thus completing the identification of the radar adaptive waveform selection behavior. Finally, through simulation analysis, the method has good results.

Radar usually employs several signal processing methods successively for detection. Each processing step influences the radar detection performance. Thus, analysis of the radar detection performance considering the complete signal processing flow provides significant reference for radar detector design. In this paper, with the assumption that matched filtering, square-law detection, non-coherent integration, cell averaging constant false alarm rate detection and double-threshold detection are employed sequentially for radar detection, radar detection performance in K distributed sea clutter plus Rayleigh distributed thermal noise is analyzed. Mathematical expressions of radar false alarm probability and detection probability are derived. Radar detection performances for four types of Swerling fluctuating targets in various circumstances are presented by simulation. And comprehensive effect of K distributed sea clutter plus Rayleigh distributed thermal noise on radar detection performance is analyzed.

Frequency-agile(FA) radars allow flexible changes in carrier frequency between adjacent pulses, offering significant advantages in anti-jamming performance. However, the discontinuity in echo phase renders the Fast Fourier Transform (FFT) unsuitable, resulting in a high computational burden for coherent integration.To address this challenge, this paper proposes a Frequency-Pulse Repetition Time(PRT) Coupled Agile (FPCA) waveform design scheme, wherein the velocity-induced phase within a coherent processing interval (CPI) is constrained to be an integer multiple of a constant, thereby facilitating subsequent coherent integration. We first derive the analytical relationship between carrier frequency and PRT in FPCA, and then propose two FPCA design approaches: one with a constrained lower PRT bound, and another with both upper and lower PRT bounds.Furthermore, a fast signal processing method tailored for the proposed waveform in multi-target scenarios is developed.After phase cancellation of the echoes, the Velocity Spectrum Profile (VSP) is obtained via FFT, and multiple VSPs are non-coherently accumulated to suppress cross-terms arising from phase compensation, enabling robust estimation of strong target velocities.Velocity compensation and IFFT are then applied to obtain range estimates for strong targets, followed by weak target imaging based on the CLEAN algorithm.Simulation results are provided to validate the effectiveness of the proposed scheme. Compared with existing coherent processing methods for frequency-agile radars, the proposed approach significantly reduces computational complexity, requiring only several to a dozen FFTs to obtain target parameter estimates, thus offering a practical frequency-agile solution for radar platforms with limited computational resources and stringent real-time requirements.

<p indent=0mm>Compared with urban application scenarios, Global Navigation Satellite System (GNSS) navigation receivers that are mounted on high-speed aircraft must handle a higher carrier frequency dynamic and output the measured result at a higher frequency. Both these factors adversely affect the accuracy of the carrier frequency measurement. Herein, we propose an adaptive carrier-tracking algorithm to measure the radial velocity by introducing a fuzzy logic controller in the carrier-tracking loop. The proposed algorithm adaptively adjusts the loop bandwidth as the carrier frequency changes, improving the velocity measurement accuracy while ensuring dynamic adaptability. Herein, the measured result of the loop is used to calculate the input variables of the fuzzy controller, and the output of the fuzzy controller is used to adjust the loop bandwidth. The fuzzy controller adopts a single input and single output Takagi-Sugeno model, which is easy to implement. The analysis and simulation are performed under fixed-, linear-, and sine-shaped Doppler frequency scenarios. The radial velocity between the aircraft and the receiver is set in the range of <sc>±10 km/s,</sc> and the radial acceleration is set in the range of <sc>±30<italic>g</italic>.</sc> To ensure the validity of the measurement results, we output the measurement results at a frequency of 1000 points per second. Simulation results demonstrate that when the input carrier-to-noise ratio is <sc>40 dB Hz,</sc> the velocity accuracy of the proposed algorithm is better than <sc>0.3 m/s</sc> (1<italic>σ</italic>).

It is hypothesized that proportional changes in echo amplitude and carrier frequency might aid obstacle avoidance in cf bats by means of acoustic flow perception. This approach appears to be feasible in principle for single targets, however, obstacle avoidance, unlike prey capture in midair, is invariably prone to constitute a multiple target problem, which has to be addressed in assessing the hypothesis’ validity. In order to map a compound excitation pattern formed by superposition of responses to multiple echoes back into target space by means of an acoustic flow approach, instantaneous (carrier) frequency and amplitude together with their first-order derivatives must be recovered individually for each echo to be perceived as a separate entity. The primal sketch serving as a substrate for this operation is impoverished in that it is only preserving response envelopes. At the same time, the system design might capitalize on knowledge about the transfer functions of the filter bank’s channels as well as at least a rough guess about the echo spectrum. Consequently, it is attempted to explain compound excitation patterns as a sum of superimposed responses to individual echoes, which are known for any given frequency location to a scaling constant.

peer reviewed

Extracorporeal shock wave therapy (ESWT) achieves its therapeutic purpose mainly through the biological effects produced by the interaction of shock waves with tissues, and the accurate measurement and calculation of the mechanical parameters of shock waves in tissues are of great significance in formulating the therapeutic strategy and evaluating the therapeutic effect. This study utilizes the approach of implanting flexible polyvinylidene fluoride (PVDF) vibration sensors inside the tissue-mimicking phantom of various thicknesses to capture waveforms at different depths during the impact process in real time. Parameters including positive and negative pressure changes (P+, P-), pulse wave rise time ([Formula: see text]), and energy flux density (EFD) are calculated, and frequency spectrum analysis of the waveforms is conducted. The dynamic response, propagation process, and attenuation law of the shock wave in the phantom under different impact intensities were analyzed. Results showed that flexible PVDF sensors could precisely acquire the characteristics of pulse waveform propagating within the phantom. At the same depth, as the driving pressure increases, P+ and P- increase linearly, and [Formula: see text] remains constant. At the same driving pressure, P+, P-, and EFD decay exponentially with increasing propagation depth. At the same depth, the spectra of pulse waveforms are similar, and the increasing driving pressure does not cause significant changes in carrier frequency and modulation frequency. The research findings could provide a reference for developing ESWT devices, improving treatment strategies, and enhancing the safety of clinical applications.

A frequency-hopping communication receiver based on Rydberg atoms, whose carrier frequency changes in accordance with a predetermined sequence, is proposed for what we believe to be the first time and experimentally verified. Based on the coherent population trapping (CPT) effect of atoms, a five-level system is built under the assumption of a constant laser wavelength, where the carrier is the resonance band corresponding to different separated quantum states. Pseudo-random binary sequence (PRBS) and complex image signals undergo keying modulation to achieve frequency-domain hopping reception. In the experiment, a dynamic range of 62 dB is demonstrated. The digital transmission with a data rate of 1 Mbps is performed reliably, within a tunable bandwidth of 50 MHz, an instantaneous bandwidth of 700 kHz and a max hopping rate of 20000 hop/s. The proposed atom-based frequency-hopping receiver is suitable for secure communications, satellite uplinks, quantum cryptography, and high-precision scientific research.

This work aims to design and implement a secure frequency hopping spread spectrum system (FHSS) on an FPGA. Design is modelled using the Verilog HDL module. In this work, Xilinx ISE Design suite 14.4 software is used along with the ModelSim simulator and XST synthesizer. The core of the FHSS transmitter is a Direct Digital Synthesizer (DDS) which generate desired frequency signal. This is a very secure communication system because its carrier frequency changes at every fixed interval in a Pseudo-Random manner. In this work, the simulation and synthesis procedure of a frequency hopping binary frequency shift keying (FH/BFSK) spread spectrum system is designed and described.

In an integrated radar and communication system, the filter output of each pulse of the integrated radar and communication waveform usually has high sidelobe level (SLL) and signal-to-noise ratio (SNR) loss as well as serious range sidelobe modulation (RSM). To solve these problems, a joint weighted optimization (JWO) method is proposed to design the filters. In this method, the filters for different integrated radar and communication waveforms are designed by jointly minimizing the RSM, SNR loss, and SLL according to different practical demands. In terms of the RSM, SNR loss, and SLL, the performance of the designed filters is tunable by reasonably changing the weight factors. Finally, several numerical results are presented to verify the effectiveness of the proposed method.

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A generic way of estimating the radar cross section of radar targets is introduced, which can be used to make simple estimates of radar performance. This approach is complemented by simple ways of approximating the detection performance of a well-designed radar and estimates of the resolution to which an operator can detect changes in the performance of a radar.

Due to limitations in the bandwidth resources, sharing the spectrum across several modalities has become increasingly important. In this paper, we will consider OFDM spectral sharing between radar and wireless communication systems. We will define and compute the importance of each sub-carrier to both the modalities by considering the radar detection performance and channel capacity. We will design the OFDM waveforms for communications and radar by appropriately allocating the sub-carriers using these importance functions. Using numerical simulations, we will demonstrate the performance of our proposed design mechanism.

Polarization cancellation is an effective method to improve the radar target detection performance under the main lobe interference environment. Interference suppression ratio is widely used to assessment polarization filter performance. However, the radar target detection performance is determined by the Signal Interference plus Noise Ratio (SINR). It is important to analyze the polarization filter's effect on the improvement of SINR. The paper proposes a mathematical model of the relationship between the changes of SINR with the relevant factors under different interference conditions. The relevant factors conclude the degree of polarization (DoP) of interference and the polarization differences between the target with interference. Based on this model, the effect of relevant factors on radar target detection performance is described. Finally, the model is tested and verified by radar target detection experiments under the jamming conditions. The results of the paper will provide a reference to design the anti-jamming configuration for the polarimetric radar.