3 kW L band mode S solid state transmitter (STX2000)

This paper describes a L band solid state pulsed transmitter which has been developed to equip a new mode S station for air traffic control in the frame of the programme POEMS (Pre-Operational European Mode S Station). The STX2000 transmitter was designed with the new available technologies to meet the mode S requirements defined by the International Civil Aviation Organisation (ICAO) but it is also compatible with the present air traffic communication system. Compared to the old generation, it typically delivers more power (3 kW peak at 1030 MHz) to a 2 channel rotating antenna: sum channel (directional propagation) and control channel (omnidirectional propagation) with the capability of a dynamic output power attenuation (0 dB to 12 dB) in order to modify the radar range according to the aircraft position. The maximum 2400 mode S interrogations per second can be transmitted on the sum channel with a duty cycle which can reach 64% during 4.8 ms (96 consecutive made S interrogations). Regarding the air traffic control application, a precise safety analysis defined tests that have to be run in operation to report any failure which may affect the system performance and to protect the transmitter itself (for instance, output RF transistor junction temperature measurements).