CX74017-17

Introduction

Very much like its well-established superheterodyne receiver counterpart, introduced in 1918 by Armstrong [1], the origins of the DCR date back to the first half of last century when a single down-conversion receiver was first described by F.M. Colebrook in 1924 [2], and the term homodynewas applied. Additional developments led to the publication in 1947 of an article by D. G. Tucker [3], which first coined the term synchrodyne, in a receiver, which was designed as a precision demodulator for measurement equipment rather than a radio. Another paper by the latter in 1954 [4] reports the various single down-conversion receivers published at the time, and clarifies the difference between the homodyne (sometimes referred to as coherent detector) and the synchrodyne receivers: the former obtains the Local Oscillator (LO) directly, for example, from the transmitter, whereas the latter synchronizes a free- running LO to the incoming carrier.