Transmit receive module for space ground link subsystem (SGLS) and unified S-band (USB) satellite telemetry, tracking and commanding (TT and C), and communications

To support the operation of a large number of satellites at various orbits, a network of antennas distributed around the globe is needed to contact satellites at predetermined time and location. These satellites require efficient telemetry, tracking and commanding (TT and C) for payload operation. Currently large mechanically steered parabolic antennas provide transmit and receive (TR) capabilities in support of satellite operations (SATOPS). Reflector antennas have been used because of relatively low acquisition cost. S-band component technology provided by the cellular telephone industry will now allow an affordable electronically scanned antenna (ESA). Current SA TOPS require a more efficient and flexible antenna system. The ESA can offer superior performance, operability, adaptability and maintainability for satellite operation. This paper presents the design of a TR module which can provide two separate transmit (Tx) and two receive (Rx) links to a satellite. The TR module is part of a dome shaped antenna which could provide multiple simultaneous ground to satellite links. This geodome antenna provides multiple simultaneous operations with pointing and acquisition taking seconds. One dome antenna can replace the capability of three parabolic dishes. The low cost TR module has been developed by the AFRL/Information Grid Division (IFG) and Princeton Microwave Technology Incorporated for the next generation of the AF Satellite Control Network (AFSCN). The TR module consists of two Tx channels each capable of 20 dB of output power and two Rx channels with a gain of 30 dB per channel. In addition, beam switching and on board digital control has been implemented where the Tx and Rx channels provide four bit phase shift and five bit amplitude control. In addition to the control functions, built-in test (BIT) circuits monitor the health and status of the RF devices. This function utilizes a microcontroller to output digital data for each of the power and low noise amplifiers, via A/D converters. The bandwidth of the TR module has been designed to cover both the unified S-band (USB) and satellite ground link subsystem (SGLS). The TR functions are combined at the output via a ceramic resonator diplexer comprised of a bandpass-bandstop filter. The control of the TR module is conducted via a single programmable logic device (PLD) controller through a DAQ computer interface. The TR module has been designed to meet the cost objective for a dome antenna with approximately 47000 TR modules. The paper details the performance and methods used to achieve the performance goals. A 78 element triangular panel of TR modules has been successfully tested at an AFRL antenna test site. A six panel subarray was successfully demonstrated at a NASA flight test facility in August 2004, where a subarray of 468 TR modules provided TT and C to low Earth orbit satellites. This paper provides a detailed layout of the TR module and its measured characteristics.