The phase shifter is the key component for phased array systems. However, the previously proposed microwave photonic phase shifter always has a complex structure and is difficult to operate. In this paper, a simple microwave photonic phase shifter based on waveplate rotation is proposed. It is composed of a cascaded quarter-wave plate (QWP) and a half-wave plate (HWP), the QWP is used to control the amplitude and HWP is adopted to control the phase of the microwave signal. By fixing the rotating angle of QWP, the phase of the microwave signal will be linearly changed with the rotation angle of the HWP. Compared with other schemes, the proposed method is easy to use. A proof-of-concept experiment is performed. Experimental result shows that a wide phase shift range of 542.38° can be realized and the power fluctuation can be within 0.47 dB. For a 360° phase shift, the power fluctuation can be maintained within 0.33 dB.
Microwave photonic mixer owns the advantages of wide frequency coverage range and large processing bandwidth. However, the LO spurious of the mixer is still high, which severely limits its application where the LO spurious locate at the band of interest. In this paper, a novel microwave photonic mixer with complete suppression of LO spurious is proposed. A dual-drive mach-zehnder modulator (DD-MZM) is adopted. The LO signal and RF signal are applied to the DD-MZM through the two driven ports. The optical signal is controlled to make the LO signal to be the phase modulation and the IF signal to be the intensity modulated. Finally, after the intensity detection completed by the photodetector, only the IF signal will be preserved and the LO spurious can be all suppressed. A proof-of-concept experiment is performed. Experimental result shows that 50-dB suppression of LO spurious can be realized.
As a fast and accurate active ranging technique, LiDAR (Light Detection and Ranging) plays an increasingly important role in the future intelligent society. Driven by the fast-booming miniaturized robotics industries, the small-size, lightweight, and low-power LiDAR with a high update rate shows huge application perspectives and is highly desired. In this paper, a novel microwave-photonic frequency-modulated continuous wave (FMCW) LiDAR on a silicon-photonic chip is proposed, which can realize simultaneous distance and speed sensing. The FMCW generation, LiDAR signals passive processing and photoelectric detection are integrated into a single silicon photonic chip with a footprint of about 1mm×2 mm. Also, a phase-based signal demodulation scheme is proposed for this LiDAR, which makes the update rate of the LiDAR equal to the DAQ sampling rate, greatly increasing the dynamic performance of the LiDAR. Numerical verifications show this LiDAR can reach a micrometer resolution and megahertz update rate. The results of the proof-of-concept experiment will be given in the near future.
KEYWORDS: Frequency conversion, Microwave photonics, Single mode fibers, Digital signal processing, Antennas, Modulation, Telecommunications, Signal processing, Optical signal processing, Modulators
Microwave photonic frequency conversion and transmission is highly needed in modern distributed communication systems. However, the periodically power fading and co-frequency interference limits the working frequency range, transmission distance, and the number of channels. To address the above questions, a novel dual-channel microwave photonic frequency conversion and transmission method is proposed. A DPol-DPMZM modulator is applied and the dual-channel intermediate frequency (IF) signals and the local oscillator (LO) signal are both applied to the DPol-DPMZM modulator to produce optical sidebands of IF and LO signals. Through the jointly manipulate phase of optical sidebands, the periodically power fading and co-frequency interference problems can be simultaneously addressed, which guarantees the broadband and multi-channel performance of microwave photonic frequency conversion and transmission system.
Frequency-swept interferometry (FSI) is intrinsically suitable for static ranging. For dynamic targets, its ranging accuracy is deteriorated by the Doppler phenomenon, and its measurement rate is restricted by the frequency sweep rate (usually kHz level), which prevents the acquisition of accurate time-varying distance details. To solve the problems, a novel microwave-photonic dynamic FSI (MP-DFSI) for fast ranging is proposed in this paper, which uses a single-frequency laser and an electro-optic modulator (EOM) to constitute a dual-sweep laser to provide two ideal mirrored laser sweeps. The instantaneous phases of the MP-DFSI signals are modulated by both the target distance and velocity in measurement, we investigate and model the modulation relationship, present a new data fusion demodulation method for high-accuracy fast ranging, which can effectively eliminate the Doppler error and recover the continuously-varying distance at each sampling point during a whole frequency-sweep cycle. Numerical verifications demonstrate that the measurement rate of the proposed MP-DFSI can reach 10 MHz with 1 μm ranging accuracy, showing the MP-DFSI has the ability of high-accuracy fast-ranging for dynamic targets.
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