Search

We propose a photonic scheme to generate binary phase-coded microwave pulses and dual-chirp microwave waveforms without baseband-modulated signals (background noise) based on a dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM) which contains x-DDMZM and y-DDMZM at two different polarization states. A radio frequency (RF) signal from a microwave source is transferred into two differential RF signals and employed into one arm of x-DDMZM and one arm of y-DDMZM, while a baseband signal from an arbitrary waveform generator is divided by an electronic coupler and then driven into the two other arms of DP-DDMZM. By adjusting the phase differences between the x-DDMZM and the y-DDMZM, binary phase-coded pulses and dual-chirp signals without baseband-modulated signals are generated. The proposed scheme can eliminate the interference caused by baseband-modulated signals, and satisfy different radar applications for different frequency bands. Experimental results show that phase-coded signals at 15 GHz with the bit rates of 1 Gb/s and 2 Gb/s and dual-chirp signals at 10 GHz and 15 GHz with the time durations of 0.5 μs are successfully generated. The reported scheme is well analyzed in theory and verified by experiment.

We propose a photonic scheme to generate binary phase-coded microwave pulses and dual-chirp microwave waveforms without baseband-modulated signals (background noise) based on a dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM) which contains x-DDMZM and y-DDMZM at two different polarization states. A radio frequency (RF) signal from a microwave source is transferred into two differential RF signals and employed into one arm of x-DDMZM and one arm of y-DDMZM, while a baseband signal from an arbitrary waveform generator is divided by an electronic coupler and then driven into the two other arms of DP-DDMZM. By adjusting the phase differences between the x-DDMZM and the y-DDMZM, binary phase-coded pulses and dual-chirp signals without baseband-modulated signals are generated. The proposed scheme can eliminate the interference caused by baseband-modulated signals, and satisfy different radar applications for different frequency bands. Experimental results show that phase-coded signals at 15 GHz with the bit rates of 1 Gb/s and 2 Gb/s and dual-chirp signals at 10 GHz and 15 GHz with the time durations of 0.5 μs are successfully generated. The reported scheme is well analyzed in theory and verified by experiment. [ABSTRACT FROM AUTHOR]

We propose a photonic scheme to generate dual-chirp microwave waveforms based on a widely tunable optoelectronic oscillator (OEO) using a dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM). The upper DDMZM is properly biased to serve as a phase modulator and further constructs OEO loop to generate radio frequency (RF). The lower DDMZM injected by the combination of the RF and a single-chirp signal is utilized to generate a dual-chirp microwave waveform with an arbitrarily tunable central frequency. The RF from the OEO replaces external millimeter-wave source in our scheme, which improves the phase noise performance of RF in high-frequency range, alleviates the complexity of the system, and increases the possibility of integration. Dual-chirp microwave waveforms centered at 10 GHz with a bandwidths of 0.4 GHz and 1 GHz, and centered at 15 GHz with a bandwidth of 0.4 GHz are successfully generated. The proposed scheme is theoretically analyzed and experimentally demonstrated. [ABSTRACT FROM AUTHOR]

Accurate timing synchronization is fundamental for the orthogonal time frequency space (OTFS) system to work properly, but the severe Doppler effect makes it a challenging task in high-mobility environments and high carrier frequency systems. To tackle this challenge, we propose a timing synchronization algorithm based on the Radon-Wigner transform (RWT) of chirp signals for OTFS modulation systems in high-mobility environments, which makes full use of the anti-Doppler performance of chirp signals and the energy aggregation characteristics of RWT to achieve accurate timing synchronization in high-Doppler conditions. Firstly, a training sequence consisting of a dual-chirp signal is transformed from the time domain to the delay-Doppler domain and then superimposed on the user data at the transmitter side. Subsequently, the timing synchronization of the OTFS system is implemented by detecting the peak value of the chirp signal after RWT and computing the difference in peak position between the transmitted and received chirp signals. Simulation results demonstrate that the proposed scheme offers a superior performance gain in low signal-to-noise ratio and high-Doppler conditions. • A timing synchronization algorithm for orthogonal time frequency space systems in high-mobility environments. • Dual-chirp training sequences are superimposed on user data in the delay-Doppler domain. • The Radon-Wigner transform was utilized for frame detection and timing offset estimation. • The superimposition of the training sequence does not introduce extra overhead. • It does not have any acquisition range limitations and robust to low signal-to-noise ratio and high-Doppler conditions. [ABSTRACT FROM AUTHOR]

A photonic approach to generating a dual-chirp microwave waveform using a single dual-parallel Mach-Zehnder modulator (DPMZM) is proposed and experimentally demonstrated. A dual-chirp microwave waveform can be used in a radar system to improve its range-Doppler resolution. In the proposed approach, a baseband single-chirp waveform is applied to one sub-Mach-Zehnder modulator (sub-MZM) in the DPMZM and a microwave carrier is applied to the other sub-MZM. By biasing the two sub-MZMs at the minimum transmission point to suppress the optical carrier, a dual-chirp microwave waveform with a central frequency upconverted to the frequency of the microwave carrier is generated. A theoretical analysis is performed, which is then verified by a proof-of-concept experiment. A dual-chirp microwave waveform at 6 GHz with a tunable bandwidth at 200 MHz and 2 GHz is generated. [ABSTRACT FROM PUBLISHER]