Abstract
Microwave photonic channelizer based on coherent frequency combs (OFCs) enables processing of ultra-wideband RF signals using low-frequency components. The channel number usually equals to the comb line number of the OFCs and the bandwidth for the microwave input is determined by the frequency spacing of the OFCs. However, the generation of coherent OFCs with large comb lines and large frequency spacing is extremely challenging, limiting greatly the potential of the OFC-based channelizer. In this paper, a microwave photonic channelizer based on polarization multiplexing and photonic dual output image reject mixing is proposed and demonstrated. A broadband signal can be divided into 8 channels using only one optical carrier and a pair of dual-polarization local oscillators (DP-LOs). Each DP-LO has only 2 spectral lines with orthogonal polarization states. In addition, by introducing a pair of OFCs with $N$ comb lines, $8N$ channels can be output. The requirement of the comb line number is efficiently reduced, and the in-band interference is greatly suppressed by introducing the polarization multiplexing and the photonic dual-output image-reject mixing. A proof-of-concept experiment is carried out. An RF signal with 9.6-GHz bandwidth centered at 14 GHz is successfully divided into 8 channels with 1.2-GHz bandwidth, and the in-band interference is effectively suppressed for each channel. In addition, RF signals with 2.4-GHz bandwidth centered at 24.8 and 30.8 GHz are also successfully channelized, respectively.
Highlights
Microwave photonic channelization has been widely studied in recent years, due to the wideband RF signal processing capability which is urgently required in modern RF systems [1]–[4], including radar, electronic warfare, satellite payload and so on
The requirement of the comb line number is efficiently reduced and the in-band interference is greatly suppressed by introducing the polarization multiplexing and the photonic dualoutput image-reject mixing
An RF signal with 9.6-GHz bandwidth centered at 14 GHz is successfully divided into 8 channels with 1.2-GHz bandwidth, and the in-band interference is effectively suppressed for each channel
Summary
Microwave photonic channelization has been widely studied in recent years, due to the wideband RF signal processing capability which is urgently required in modern RF systems [1]–[4], including radar, electronic warfare, satellite payload and so on. The microwave photonic channelization realizes the function of slicing a wideband RF signal into narrowband channels compatible with current electronics by introducing photonic technologies [5]–[15]. There are three main methods to realize the microwave photonic channelization. The RF signal is modulated to the optical domain, which is sliced into a number of channels through using. The RF signal is copied to the comb lines of an optical frequency comb (OFC), which is filtered by a periodic optical filter with a slightly different filtering period as compared with the comb line frequency spacing [8]–[11]. The third method is based on two coherent OFCs having slightly different comb line frequency spacings [12]–[14]. The two OFCs can be equivalently realized by using linear frequency
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