Future wireless communication, radar, and electronic warfare systems are inevitably evolving towards higher frequency bands, wider bandwidths, and larger dynamic ranges. Achieving high-quality reception of ultrawideband signals has become one of the current research hotspots. Most of the reported microwave photonic channelized receiver schemes are based on the optical frequency comb (OFC) reception principle. However, due to the limitations of OFC generation techniques, it is challenging to significantly enhance the operating frequency range and maximum instantaneous bandwidth of the receiver. Moreover, full-duplex systems can double the spectral efficiency, but they inevitably generate self-interference (SI) signals, which degrade the communication quality. Current research on microwave photonic channelized reception primarily focuses on channelization schemes based on OFCs, especially those employing dual OFCs. This requirement increases system complexity and makes it challenging to expand the number of subchannels due to the limited number of comb lines. Although Kerr OFCs generated by integrating microring resonators (MRRs) can provide a large number of comb lines, their line spacing is not tunable and is susceptible to instability caused by factors such as temperature.

In response to the challenge of generating ideal OFCs in existing channelized receiver schemes based on OFCs, a method for generating 6-line or 8-line OFCs is proposed. The generated combs exhibites low modulation index, high flatness, and flexible tuning of the comb line spacing. To address the issue of low channelization efficiency of a single comb line, a method utilizing an acousto-optic frequency shifter (AOFS) to shift the OFC is proposed, which enhances the channelization efficiency of a single comb line by a factor of three. To tackle the inevitable image interference in superheterodyne receiver architectures, a method for broadband signal image suppression in the digital domain using an in-phase/quadrature (I/Q) balance compensation algorithm is proposed. For the SI problem in full-duplex transceiver systems, a method of introducing a reference signal with the same amplitude but opposite phase as the self-interference signal to directly suppress self-interference in the all-optical domain is proposed.

We carry out experiments to verify the proposed scheme. Fig. 4 shows the experimental results of the 6-line OFC generation, indicating good flatness and out-of-band suppression ratio of the OFC. Fig. 5 presents the experimental results of image suppression for a 300 MHz wideband signal. When the broadband signals of channel 2 and channel 5 are image signals to each other, the image suppression ratio is not less than 33 dB. The same applies to channels 7 and 10, as well as channels 15 and 18. Compared with the Hartley-based image-rejection mixer, our proposed algorithm shows remarkable advantages. Fig. 6 shows the self-interference cancellation experimental results. When the signal bandwidth is 100 MHz, the self-interference depth can exceed 32 dB. It should be noted that due to experimental limitations, it is not feasible to directly generate a broadband signal with a bandwidth of 36 GHz. Therefore, in our experiments, we employ a series of 16-QAM signals with continuous spectra and a bandwidth of 300 MHz each. These signals are used to verify the channelized reception and image suppression capabilities within the 2?38 GHz frequency band through spectral coverage. For the verification of self-interference cancellation, a broadband signal with a bandwidth of 100 MHz is used as the self-interference signal. It is worth mentioning that both the image suppression and self-interference cancellation performance are expected to degrade as the signal bandwidth increases.

Compared to other reported microwave photonic channelization schemes based on dual OFCs, the proposed scheme can achieve instantaneous and complete reception of any wideband signal in the 2?38 GHz range using just a single 6-line OFC. It has obvious advantages in system complexity, cost, operating bandwidth, and maximum instantaneous bandwidth and shows great potential for future applications in radar, electronic warfare, wireless communication, and other fields.