The phase performance of digital radio frequency memories (DRFMs)

The Digital Radio Frequency Memory (DRFM) is a device which samples a radio signal, usually at microwave frequencies, and regenerates it after a controlled delay. It is anticipated that DRFMs will replace analogue delay lines in the next generation of Radar Test and Electronic Counter Measures (ECM) equipment. The minimum DRFM consists of: a downconverter from radio frequencies to baseband, a digital delay line, and an upconverter back to the original input frequency. The paper outlines the basic hardware configurations. For the designer of coherent or interferometric systems, the relative phase of the input and output signals is of key importance. This is particularly true for counters to Doppler and angle tracking radar systems. An investigation into the likely phase errors introduced by DRFM sampling and reconstruction is given