The Effects of Test-Set Distortions on Pulsed-RF Measurements

Abstract

SILVER SPRING, MDBa c kq roundThe work reported i n t h i s paper was accomplished i n support of NWSC a t Crane, Indiana. NWSC i s responsible for the acceptance testing of Surface Navy microwave tubes. Considering the large volume of tubes from different vendors and the need f o r consistent and h i h quality measurements, NUSC developed a prototype Microwave Tube Test Set 9 MTTS) and integrated i t w i t h off-the shelf digital instrumentation. An a HP 9836C controller is used for instrumentation control and data storage, and a printer for data documentation. Ultimately, the MTTS will beused t o evaluate failure mode effects and design changes as well as acceptance of production microwave tubes.The long range objective fs t o have all tube vendors use the NWSC microwave tube t e s t s e t and software t o assure standard acceptance of a l l types of microwave tubes. Vitro provided t h i r d party support i n generating an Acceptance Test t h a t encompassed the MTTS equfpment, interfaces, and software. The reason f o r t h i s approach rather t h a n software testing, only was.that i f tube vendors lost confidence i n the operation of the MTTS and software, i t would tend t o be questioned even i f subsequent modification provided successful system operation. Microwave Tube Test Set (MTTS) DescriptionAs shown i n Figure 1, the MTTS consists of a stabilized S-band TWT source feeding the Tube-Under-Test (TUT) through 17 sections of S-band waveguide and 8 sections of waveguide connecting the NT t o the load. Waveguide couplers are used a t i n p u t and o u t p u t t o provide necessary ports t o power meters a n d voltmeters. Additional couplers and waveguides are used t o connect a phase set across the TUT. All tube measurements are made i n the frequency domain. A system trigger turns on t h e TWT modulator as well as the TUT modulator t o provide normal operating voltages. An instrumented calorimeter i s used t o measure o u t p u t power. A1 1 tests were performed i n accordance w i t h NIL-STD-1311. 55