Microwave photonic frequency generation and conversion unit design for Ka-band satellite payloads

A key challenge for HTS (high throughput satellite) providers is the provision of higher capacities whilst operating within a challenging mass-power-volume envelope. As payload requirements become more demanding, there is a move toward Ka-band, with even higher frequencies being used for Q/V-band feeder links. In order to satisfy the demand for reconfigurability and higher operating frequencies, there has been increased activity in microwave photonic (MWP) payload design. Two of the key functionalities that have been identified in microwave photonic payload design are the frequency generation unit (FGU) and frequency conversion unit (FCU). In this paper, we describe a proof-of-concept MWP FGU-FCU unit, which is configured as a breadboard demonstrator. The FGU is based on an X-band dual-loop optoelectronic oscillator, which provides a low phase noise microwave modulated LO to the following FCU stage. This unit is based on the application of electro-optic mixing in a Mach-Zehnder modulator. Incoming high frequency Ka-band signals (27.5-29.5 GHz) are applied to the RF drive of the EOM and are down-converted to a lower band (19.7-20.2 GHz) through subsequent photo-detection in the Optical-to-Electrical conversion (O/E) block. An optical amplifier (OA) is placed in the photonic link to compensate the opto-electronic conversion losses at the optical domain of the income signals. Hence the EOM, OA and O/E chain comprises the frequency conversion unit (FCU). We also outline potential paths to a fully integrated combined MWP FGU-FCU.