The very basics of a transmitter.
A SuperDARN transmitter is the interface between the radar control signals for transmit and the antenna. A very basic block diagram shows the transmitters inputs and outputs:
Figure 1: A Block Diagram of SuperDARN transmitter showing inputs and outputs.
SuperDARN transmitters are only present on the main array antennas because the interferometer array is a receive-only array.
The SuperDARN transmitter has the following functions:
1) Takes RF pulses and amplifies them before sending them to the antenna to transmit.
2) Switches between transmit mode and receive mode, only allowing the receive path to be open from antenna through to processing when not in transmit mode. This protects the receivers from the transmitter's amplifiers.
3) Has a feedback loop for automatic gain control of the transmitted pulses. This allows the output amplitude to be fairly uniform with time and across transmitters.
4) Has reflection measurement built in, to prevent reflection damage to itself should some problem arise. It will cut out the transmission for a few seconds before trying again if large reflected powers occur. This could happen with very nearby reflections, including feedline problems.