A direct digital radio having a high speed RF front end in communication with an antenna, and a radio subsystem that can be configured to form a multi-channel, full duplex transceiver system. The high speed RF front end provides a digital signal to the radio subsystem. Each transceiver includes a waveform processing subsystem that makes use of a linear, phase-B cubic spline interpolating finite impulse response (IFIR) filter for filtering the received RF signal substantially entirely in the digital domain. The linear phase-B, cubic spline IFIR filter requires significantly fewer hardware components than traditional FIR filters and is ideally suited for implementation using Very Large Scale Integration (VLSI) technology.