Modulated single channel digital radio frequency memory (drfm)

Abstract

A modulated single channel (as opposed to a quadrature channel) digital radio frequency memory (DRFM) system retrievably stores incoming radio frequency (RF) signals in a digital memory and replicates the RF signals at the output. The input RF signal to be stored is mixed with a local oscillator (LO) signal modulated with a waveform pattern to produce an intermediate frequency (IF) signal which is digitized and retrievably stored in the digital memory. The stored digital values are later retrieved from memory after the programmed delay time, and converted back to an analog IF signal and mixed with the local oscillator to produce the output RF signal. The LO signal is modulated with the same waveform used to produce the input IF signal. A controller for controlling the modulation of the LO signal and the memory includes a ROM for storing a pseudo random string of one bit words and an address counter to drive the ROM beginning at a starting address upon the occurrence of the input RF signal. A latch memorizes the starting address and resets the address counter to the starting address after the programmed delay for the output RF signal. The ROM output is converted to an analog signal and applied to modulate the local oscillator signal with the same waveform so that the output RF signal is a replica of the input RF signal.