PULSED SOLID STATE POWER AMPLIFIERS FOR 30/20 GHZ SATCOM TERMINAL UPLINK TRANSMITTER

THE EVOLUTION OF ADVANCED 30/20 GHZ SATCOM SYSTEMS FOR DEPLOYMENT IN THE LATE 1980'S AND EARLY 1990'S EMPHASIZES THE USE OF WIDEBAND PREDOMINANTLY DIGITAL TRAFFIC, SERVICINGMANY DISPERSED USER GROUND TERMINALS VIA A SINGLE SOPHISTICATED SATELLITE, OPERATED IN FREQUENCY OR TIME DOMAIN MULTIPLE ACCESS (FDMA OR TDMA) MODES. IN FACT, THE ADVANCED COMMUNICATIONS TECHNOLOGY SATELLITE (ACTS) CURRENTLY BEING DEVELOPED UNDER NASA SPONSORSHIP WILL, ALONG WITH THE ASSOCIATED 30/20 GHZ GROUND TERMINALS UNDER DEVELOPMENT, BECOME THE PROTOTYPE AND PRECURSOR OF THE 30/20 GHZ SATCOM SYSTEM OF THE FUTURE. IN ORDER TO FULLY EXPLOIT THE PLANNED UTILIZATION OF ACTS AND ITS 30/20 GHZ SUCCESSOR SATELLITES FOR LARGE SCALE COMMUNICATIONS BETWEEN MANY 30/20 GHZ SMALL TERMINALS, IT ISIMPERATIVE THAT EARTH STATION 30 HHZ TRANSMITTERS BE SIMPLE,RELIABLE AND INEXPENSIVE, WHILE PROVIDING SUFFICIENT RF POWER, TYPICALLY 8-16W TO ACCOMODATE TDMA BURST RATES OF 13.75-27.5 MB/S. WHEREAS THESE POWER LEVELS CAN BE PROVIDED BY COMBINATORIAL SOLID STATE POWER AMPLIFIERS (SSPA'S) COMPRISING 1-2W IMPATT (OR FET) BUILDING BLOCKS AND 8-16 WAY OUTPUT POWER COMBINERS, THE AVERAGE UPLINK BURST DUTY CYCLE OF 0.025 SUGGESTS THAT A PULSED SSPA USING HIGHER PEAK POWER PULSED IMPATT BUILDING BLOCKS CAN RESULT IN A SIMPLER, LOWER COST 30 GHZ TRANSMITTER. ACCORDINGLY, THE PROPOSED PHASE I STUDY PROGRAM WILL INVESTIGATE THE SUITABILITY OF A PULSED IMPATT AMPLIFIER ANDITS ASSOCIATED INTRAPULSE GAIN PHASE BEHAVIOR AND TRANSIENT CHARACTERISTICS TO ACCOMMODATE TDMA TRAFFIC WITHOUT DEGRADATION. IF SUCCESSFUL, A PULSED 30 GHZ IMPATT SSPA DESIGN WILL BE GENERATED WHICH COULD BE THE BASIS OF A PHASE II HARDWARE DEVELOPMENT PROGRAM.