In the last few decades, increasing research effort has focused on the design of telecommunication payload systems with advanced features and lower costs in space applications. In this context, photonic solutions have already proven the potential to achieve additional functionalities, such as multiplexing or switching of RF or microwave signals, with consequent additional benefits in terms of size and mass reduction. In this paper, we report on the design of a 2 × 2 switching cell based on a thermo-optic interferometric configuration, whose key element is a sub-wavelength grating. We have theoretically demonstrated a broadband operation, with better performance in terms of operating wavelength range and compactness with respect to the existing interferometric cells. The switching cell shows a worst extinction ratio of about 13 dB, insertion loss of less than 2 dB, crosstalk of 12 dB, over a bandwidth of 150 nm, within a footprint as small as 240 µm × 9 µm. To demonstrate its potential use as a routing fabric in flexible telecommunication satellite payloads, as an example, the designed switching cell has been used as a building block of an 8 × 8 dilated Banyan matrix, where large bandwidth (150 nm), low crosstalk (−38 dB), small footprint (≈1620 µm × 576 µm) and relatively low power consumption (276 mW) have been achieved.

Photonic generation and transmission of Linearly Chirped Microwave Waveform (LCMW) with a high Time-BandWidth Product (TBWP), of the order of 10 2 or more, is a widely used approach in Synthetic Aperture Radar (SAR) payloads to realize high range resolution, improving the distinction between two or more targets on the same bearing. In standard payload systems, an electronic approach based on voltage-controlled oscillator or digital signal processing, is used as LCMW generator, with both limited TBWP and operating frequency. In this context, a photonic approach plays a crucial role, ensuring low phase noise, high TBWP and operation frequency of the order of GHz, with a significant reduction of mass and size with respect to the electronic counterparts. Here, we propose the design of a Ka-band photonic LCMW generator, based on a frequency-tuneable Opto-Electronic Oscillator (OEO) and a Recirculating Phase Modulation Loop (RPML), with high spectral purity and high chirp rate in a small footprint. The OEO heart is a one-dimensional photonic crystal ring resonator with an ultra-high Q factor value and an optical delay > 10 μs. A low-frequency optical signal, with a high chirp rate and TBWP values of the order of 10 2 -10 3 , is generated in the RPML section.

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