New Microwave Repeater System Using Traveling-Wave Tubes

This paper describes a new microwave relaying system using traveling-wave tubes (TWT), and utilizing its large inherent frequency bandwidth. In this system, the increased gain is obtained by amplifying the input signal through the TWT Amplifier, and reamplifying it in the same TWTA after heterodyning the frequency to the second frequency. The signal received could be amplified in the same TWTA more than once simultaneously, and the gain of the TWTA would be increased in proportion to the amplifying times. A 4,000-mc band television repeater using three TWT's, and its measured results are also described; we obtain the results that the over-all gain is above 100 db and is steady within ±0.5 db with the frequency bandwidth of 20 mc, and also, the noise figure is below 15 db. The actual test was carried out by putting the equipment in the TV long-distance relay line as a repeater. From this test it was proved that there is no defect of the operation of the amplifier in using TWT as a reflex amplifier. In this new system, the number of TWT's can be reduced one-half to one-third and the cost of a repeater with increased reliability can be lowered.