The EISCAT_3D arbitrary waveform exciter and polyphase constant amplitude codes for EISCAT VHF and ESR D/E layer experiments

The performance specifications for the EISCAT_3D third-generation phased-array incoherent-scatter (IS) radar mandate a transmitter subsystem with full arbitrary-waveform capabilities and a power bandwidth of more than 5 MHz. An exciter meeting these requirements, based on the AD9957 digital up-converter chip, is currently under development at the Swedish Institute of Space Physics. An overview of the 3D exciter system and the AD9957 and its capabilities, with emphasis on its performance in an IS system, is given. To verify the capabilities of the AD9957 in a real radar environment, two polyphase codes with good D- and E-layer performance have been developed, viz. a QPSK-coded eight-element set of complementary [A, B] sequences and a complementary-coded set of 71-baud Chu sequences. Features of the two codes are described; results from on-the-air tests will be shown.