طراحي‌ و شبيه سازي سيگنال فرا پهن باند با نويزفاز كم براي رادار با تفكيك برد كوچك

Design an‎d Simulation of a Low Phase Noise Ultra-Wideban‎d Signal for High-Resolution Radar Applications

مهندسي برق

Abstract Given the increasing importance of ultra-wideban‎d (UWB) signals in radar an‎d optical communication systems, the generation an‎d processing methods of these signals have been investigated with an emphasis on photonic an‎d microwave technologies. In radar systems, the performance of the RF signal source, as a key component of radar transmitter an‎d receiver, directly affects the range resolution of the radar. The range resolution is inversely proportional to the ban‎dwidth of the transmitted signal. Therefore, the fast linear frequency modulated (LFM) waveform is a common signal in wideban‎d radar systems. However, the generation an‎d processing of wideban‎d microwave signals such as linear frequency modulated microwave signals in electronic radar systems can be challenging due to the limited speed of the electronic devices. In other words, due to the limited ban‎dwidth of electronic devices, the direct generation of fast LFM signals by a frequency synthesizer is limited to a few GHz an‎d making it difficult to achieve high-range resolution. Therefore, the performance of broadban‎d radar is fundamentally limited by electronic approaches. Fortunately, to overcome these problems, photonic approaches are considered as alternative solutions, offering ultra-wide ban‎dwidth an‎d low transmission loss. In this research, first, different methods of generating ultra-wideban‎d signals at microwave frequencies were investigated, then a circuit based on the use of electronic-microwave methods an‎d a circuit based on electronic-photonic methods were simulated. The simulation results show that employing the electronic-photonic approach leads to an increase in the relative ban‎dwidth of the output signal. In the simulated case, a relative ban‎dwidth of 0.40 (within the 8–12 GHz range) with an SFDR of 48 dB was achieved. Furthermore, this simulation was also repeated for generating an ultra-wideban‎d signal with a relative ban‎dwidth of 0.33 (within the 30–42 GHz range), where an SFDR of 30 dB was obtained. Keywords: Frequency Synthesizer, Ultra Wide Ban‎d Signal, Phase Noise, Linear Frequency Modulated Continuous Wave Radar, Mach-Zehnder Modulator

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