Variable-length quadratic envelope pulse shaping and automatic gain control for HF radars

We propose a novel digitally based automatic gain control mechanism for HF transceivers, along with a pulse shaping mechanism to suit. The system directly digitises the output waveform, and can allow for low-latency protection and gain control. Output transmit pulses need to have a smooth envelope, in order to maintain a well-behaved frequency spectrum. This is addressed with an low resource cost quadratic envelope. The design has been implemented in FPGA hardware and allows envelope shape to be modified easily, for appropriate spectrum performance.