A baseband recorder for radio pulsar observations

Digital signal recorders are becoming widely used in several subfields of c entimetre-wavelength radio astronomy. We review the benefits and design con siderations of such systems and describe the Princeton Mark IV instrument, an implementation designed for coherent-dedispersion pulsar observations. F eatures of this instrument include corrections for the distortions caused b y coarse quantization of the incoming signal, as well as algorithms that ef fectively excise both narrow-band and broad-band radio frequency interferen ce. Observations at 430 MHz, using the Mark IV system in parallel with a sy stem using a 250-kHz filter bank and incoherent dedispersion, demonstrated timing precision improvement by a factor of 3 or better for typical millise cond pulsars.