  An FPGA-based digital-receiver has been developed for a low-frequency imaging
radio interferometer, the Murchison Widefield Array (MWA). The MWA, located at
the Murchison Radio-astronomy Observatory (MRO) in Western Australia, consists
of 128 dual-polarized aperture-array elements (tiles) operating between 80 and
300\,MHz, with a total processed bandwidth of 30.72 MHz for each polarization.
Radio-frequency signals from the tiles are amplified and band limited using
analog signal conditioning units; sampled and channelized by digital-receivers.
The signals from eight tiles are processed by a single digital-receiver, thus
requiring 16 digital-receivers for the MWA. The main function of the
digital-receivers is to digitize the broad-band signals from each tile,
channelize them to form the sky-band, and transport it through optical fibers
to a centrally located correlator for further processing. The digital-receiver
firmware also implements functions to measure the signal power, perform power
equalization across the band, detect interference-like events, and invoke
diagnostic modes. The digital-receiver is controlled by high-level programs
running on a single-board-computer. This paper presents the digital-receiver
design, implementation, current status, and plans for future enhancements.
