Dapeng Hu

Microwave photonic image rejection mixer based on a DP-QPSK modulator

Abstract A simple image rejection mixer based on a dual-polarization quadrature phase shift keying modulator is presented without a 90° hybrid coupler in electrical field. By properly adjusting DC bias points in the integrated modulator and performing balanced photo-detection, the influence of image components can be well rejected. The simulation results show that a 52.24 dB image suppression ratio (ISR) and a conversion efficiency (CE) of −9.17 dB can be achieved by the proposed mixer. Besides, another research on the ISR and CE against non-ideal parameters is carried out. According to the simulation results, it can be figured that the main factor to influence the ISR and CE is the DC drifting which results both of them changed rapidly as the DC bias points deviate from the settled values. On the other hand, with different extinction ratios and LO signal powers and RF signal powers, the mixer still performs good ISR and CE.

Photonic Generation of Frequency and Bandwidth Multiplying Dual-Chirp Microwave Waveform

A photonic approach to generate a frequency and bandwidth multiplying dual-chirp microwave waveform using a single dual-polarization quadrature phase shift keying (DP-QPSK) modulator is proposed and demonstrated. In the proposed scheme, an RF carrier is applied to one QPSK modulator and a baseband single-chirp waveform is applied to another. By setting the driving signals applied to the modulator and adjusting the dc bias phases in the modulator, high-order optical sidebands can be obtained with the optical carrier suppressed. After optical to electrical conversion, a frequency-doubling and bandwidth-quadrupling, or frequency-quadrupling and bandwidth-octupling dual-chirp microwave can be generated. The approach is verified by simulation. Dual-chirp microwave waveforms with 16-GHz central frequency, 2048-MHz bandwidth and 32-GHz central frequency, 4096-MHz bandwidth are generated through an 8-GHz RF carrier and 512-MHz bandwidth baseband signal. The generated dual-chirp microwave waveform can be used in a radar system to improve its range-Doppler resolution.

Photonic microwave frequency conversion scheme with flexible phase shift

ABSTRACT In this paper, a single, flexible and stable optical frequency conversion scheme with tunable phase shift is proposed. It mainly consists of a dual-parallel binary phase shift keying (DP-BPSK) modulator and a polarization modulator (PolM). Properly setting the values of two DC bias points in the DP-BPSK modulator, the frequency conversion ability can be achieved. Meanwhile, the phase shift can also be realized by controlling the DC voltage that drives the PolM or tuning the polarization controller (PC3). The simulation results show that a 20 GHz RF signal can be converted into a 10 GHz IF signal with the conversion efficiency of −4.45 dB and a full 0° to 360° phase shift. It should be noted that the system performs well against different non-ideal factors such as extinction ratio, DC drifting or different LO and RF amplitudes. In addition, spurious free dynamic range of 82.14 dB·Hz2/3 is achieved and it can be greatly improved if a better extinction ratio is available.