Abstract
An all-optical photonic microwave phase shifter that can realize a continuous 360° phase shift over a wide frequency range is presented. It is based on the new concept of controlling the amplitude and phase of the two RF modulation sidebands via a Fourier-domain optical processor. The operating frequency range of the phase shifter is largely increased compared to the previously reported Fourier-domain optical processor based phase shifter that uses only one RF modulation sideband. This is due to the extension of the lower RF operating frequency by designing the amplitude and phase of one of the RF modulation sidebands while the other sideband is designed to realize the required RF signal phase shift. The two-sideband amplitude-and-phase-control based photonic microwave phase shifter has a simple structure as it only requires a single laser source, a phase modulator, a Fourier-domain optical processor and a single photodetector. Investigation on the bandwidth limitation problem in the conventional Fourier-domain optical processor based phase shifter is presented. Comparisons between the measured phase shifter output RF amplitude and phase responses with theory, which show excellent agreement, are also presented for the first time. Experimental results demonstrate the full -180° to + 180° phase shift with little RF signal amplitude variation of less than 3 dB and with a phase deviation of less than 4° over a 7.5 GHz to 26.5 GHz frequency range, and the phase shifter exhibits a long term stable performance.
Highlights
Microwave phase shifters are essential components in phased-array beamforming networks for radar and satellite communication systems [1, 2]
The left sideband at the frequencies of more than 20 GHz away from the optical carrier is filtered out. This is because the experimental result in [15] shows the output RF signal amplitude response of the Fourier-domain optical processor (FD-OP) based phase shifter is almost frequency independent at the frequencies above 20 GHz, and the left sideband at this frequency range is not required to compensate for the unwanted effect caused by the limited FD-OP resolution
A photonic microwave phase shifter has been presented. It is based on the new operation principle that involves controlling the amplitude and phase of the two RF modulation sidebands. It has the ability of extending the phase shifter lower RF operating frequency, which results in a large increase in the operating frequency range compared to the conventional FD-OP based phase shifter that involves only one sideband
Summary
Microwave phase shifters are essential components in phased-array beamforming networks for radar and satellite communication systems [1, 2] In such systems, the phase shifters need to provide full 0°-360° phase shift while having frequency-independent amplitude and phase responses. The experimental results presented in [15] show the phase shifter has a frequency-dependent amplitude response We provide detailed theoretical and experimental investigation on the frequency and phase-shift dependent characteristic in the conventional FD-OP based phase shifter and provide a solution to extend the phase shifter operating frequency range to cover all the X, Ku, K, and Ka bands. The novel FDOP based photonic microwave phase shifter inherits all the advantages of the conventional structure while having a wider operating frequency range. The stability of the novel FD-OP based photonic microwave phase shifter is experimentally measured for the first time
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