Radio test loop having common combiner cable connecting transmitters, spaced at nλ/2 therealong, with receivers, via frequency converter

Claim 1

A radio test loop, comprising: a plurality of radio transmitters, each arranged to supply RF transmitting power to a transmitting antenna at a respective frequency at a relatively high output impedance; a plurality of radio receivers, each arranged to receive RF power received by a receiving antenna as a result of radio transmissions by respective ones of said radio transmitters; each said radio transmitter, in addition to having an antenna line for supplying said RF transmitting power therefrom, also having a test signal output line arranged to supply RF transmitting power at a respective frequency at a relatively low output impedance as a respective test signal; a radio test loop unit including a frequency converter for converting each said test signal to a respective receiving frequency for each said radio receiver, for permitting each said radio receiver to be tested in succession in respect to each said radio transmitter, as respective pairs; said radio test loop unit having an input for receiving said test signals, and an output effectively connected to said radio receiver for providing RF power input thereto as a result of test signals being supplied by respective ones of said radio transmitters; and a common combiner cable serially connecting each said test signal output line at a respective connection with said input of said radio test loop unit with a spacing of nλ/2 between each said connection, wherein λ is the wave length at an average transmitting frequency of each said test signal, and n is a small integer, whereby only the respective relatively low output impedance of the test signal of a respective said transmitter which is being tested appears in said input of said radio test loop unit.