Broadband power combining of 5.0 kW coupled-cavity communication TWTs

This paper describes a 5.0 kW communication traveling-wave tube and the results achieved by broadband power combining two of these TWTs. The 5.0 kW TWT, Model 792H, was developed by Hughes Aircraft EDD for Philco-Ford WDL under the sponsorship of USASATCOMA for use in the AN/FSC-78V ground terminal. Two of these high power tubes operating with output powers of 3.7 kW have been power combined to produce up to 7.0 kW with a bandwidth in excess of 400 MHz at the one dB points. This combined power output was achieved with gain variations less than ±0.30 dB over any 125 MHz band. This type of performance is possible because of the TWT´s low amplitude and phase distortion characteristics. The 792H produces 5.0 kW of RF power across a 500 MHz band from 7.9 to 8.4 GHz with 35 dB of gain. The amplitude gain variations of the tube at both rated and small signal are less than ±0.30 dB over the entire 500 MHz band. These tube characteristics were achieved by special internal tube design techniques and the use of an integral equalizer.