Abstract
Photonic generation of a bandwidth multiplied linearly chirped signal with phase modulation capability is proposed and its applications in communication and radar systems are demonstrated. In the generator, a dual-polarization quadrature phase shift keying modulator is used to simultaneously perform bandwidth multiplication and phase modulation. The generator can be functionally expanded to a transceiver for wireless communication, which can be used to perform optical generation and coherent demodulation of a phase modulated linearly chirped signal. Meanwhile, the generator can be used to increase the radar detection distance by improving the signal time bandwidth product. The signal generation and application are verified by simulation. A linearly chirped signal with an instantaneous frequency of 8–12 GHz or 16–24 GHz is obtained by using a 4–6 GHz electrical driving signal. The proposed transceiver is demonstrated to perform 156.25-bit/s wireless communication. When the emitting power is 11 dBm and the communication distance is 1 km, the bit error rate can be better than 10−4. While for radar detection, the peak to sidelobe ratio of the compressed pulse is increased from 1.1 dB to 9.2 dB, through which the distance improvement can be verified.
Highlights
Chirped waveform is a form of pulse compression signal, which is widely used in radar system [1]
SIMULATION RESULTS AND DISCUSSION A simulation based on platform Optisystem is performed to verify the feasibility of the proposed signal generator
The laser diode (LD) has a central frequency of 191.3 THz and an optical power of 16 dBm
Summary
Chirped waveform is a form of pulse compression signal, which is widely used in radar system [1]. By choosing two high-order sidebands and beating them with each other, a bandwidth multiplied linearly chirped waveform can be generated This method has simple principle, flexible configuration, and tunable multiplication factor n. Data modulation is inserted in an optical microwave frequency multiplication system to achieve an amplitude shift keying (ASK) linearly chirped signal [26]. An electrical repetitive linearly chirped signal is applied to one quadrature phase shift keying modulator (QPSKM) to generate optical carrier and two high-order optical chirped sidebands, while another QPSKM is driven by a binary sequence to achieve optical data modulation. LD, laser diode; DP-QPSKM, dual-polarization quadrature phase shift keying modulator; PBC, polarization beam combiner; PR, polarization rotator; AWG, arbitrary waveform generator; PPG, pulse pattern generator; OF, optical filter; Pol, polarizer; PD, photodetector. I where Mi represents the i-th element of the binary sequence, which is defined as ‘‘0’’ or ‘‘1’’ for a unipolar NRZ signal
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