RF Frequency Selective Switch by Multiple PMIM Conversions

Nowadays, broadband and multi-channel radio frequency (RF) processing has been widely used in communication, radar, countermeasure, and other applications. At present, multiple-input and multiple-output (MIMO)-oriented microwave photonic signal processing technology is relatively scarce, so this paper proposes an RF frequency selective switch (FSS) based on multiple phase modulation to intensity modulation (PMIM) conversions. PMIM conversion has been used in narrowband microwave photonic filtering in the past. We extend it to a wideband and arbitrarily reconfigurable RF spectrum processing unit through an optical frequency comb and periodic optical filter. Although we use the incoherent combination of a multi-wavelength light source, we can obtain any frequency response including rectangles only by using all positive tap coefficients. Using an optical wavelength selective switch (WSS), we obtain RF FSS, and the spectral resolution of RF FSS is much better than that of optical WSS, which is improved by more than two orders of magnitude. The above principles, including single-channel reconfigurable filtering and multi-channel RF FSS, are verified by experiments. Our technology provides a stable solution for future RF MIMO signal processing.