Abstract
We propose a photonic method to generate and transmit dual-band dual-chirp microwave waveforms based on a dual-polarization dual-parallel Mach-Zehnder modulator (DP-DPMZM). The key novelty of this work is the generation of dual-band dual-chirp waveforms with flexible central frequency relationship to meet the requirement of the dual-band radar system, and transmission of the generated waveforms with elimination of power fading. In the proposed method, dual-band dual-chirp microwave waveforms are generated by applying two different RF signals and a parabolic coding signal to the DP-DPMZM. By properly adjusting the DC biases of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> -DPMZM and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -DPMZM, dispersion-induced power fading effect in the transmission of the generated waveforms can be compensated. A proof-of-concept experiment is conducted to generate and transmit dual-band dual-chirp microwave signals at C-band and X-band (centered at 7 GHz and 10 GHz) with tunable bandwidth. The proposed system has a simple structure and good reconfigurability, which has great potential in applications such as dual-band radar systems.
Highlights
Chirped microwave signals play a significant role in radar systems and are usually used to increase the pulse compression ratio and range resolution [1]
We propose a photonic method to generate and transmit dual-band dual-chirp microwave waveforms based on a dual-polarization dual-parallel Mach-Zehnder modulator (DP-DPMZM)
The four sub-MZMs of the DP-DPMZM were all biased at minimum transmission point (MITP) to realize carrier-suppressed modulation
Summary
Chirped microwave signals play a significant role in radar systems and are usually used to increase the pulse compression ratio and range resolution [1]. The use of a polarization-division multiplexing dual-parallel Mach-Zehnder modulator (DPMZM) was proposed in [7] to generate two frequency-quadrupling chirped signals in two different bands In this scheme, two 90° hybrid couplers are needed, which limit the bandwidth and frequency range of the generated microwave signals. The power fading effect induced by chromatic dispersion can be compensated by adjusting the direct current (DC) biases of x-DPMZM and y-DPMZM In this scheme, the center frequency of the generated dual-chirp microwave waveforms in different bands can be tuned to fulfill the needs of dual-band radar, which is hard to achieve based on conventional dual-band waveform generation schemes by using an optical frequency comb or high-order sideband modulation. The proposed scheme has good reconfigurability and simple structure, which can find potential applications in real-world scenarios
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