Citation
Abstract
This article summarizes the design concepts, analyses, and development of an X-band (8145 MHz) transponder low-loss linear phase modulator for deep space spacecraft applications. A single-section breadboard circulator-coupled reflection phase modulator has been analyzed, fabricated, and evaluated. A linear phase deviation of 92 deg with a linearity tolerance of +8 percent was measured for this modulator from 8257 MHz to 8634 MHz over the temperature range —20 deg C to +75 deg C. The measured insertion loss and the static delay variation with temperature were 2 +0.3 dB and 0.16 psec/deg C, respectively. Based on this design, cascaded sections have been modeled, and simulations were performed to provide an X-band deep space transponder (DST) phase modulator with +2.5 radians (+143 deg) of peak phase deviation to accommodate downlink signal modulation with composite telemetry data and ranging, with a deviation linearity tolerance of +8 percent and insertion loss of less than 10 +0.5 dB. A two-section phase modulator using constant gamma hyperabrupt varactors and an efficient modulator driver circuit was breadboarded. The measured results satisfy the DST phase-modulator requirements and show excellent agreement with the predicted results.
Details
- Volume
- 42-105
- Published
- May 15, 1991
- Pages
- 136–145
- File Size
- 450.9 KB