DESIGN AND PERFORMANCE OF A MULTI-MODE MULTI-RATE TELEMETRY TRANSMITTER

Abstract

Typical telemetry transmitter designs have focused on analog-circuit implementations, which suffer limitations when required to support multi-mode and multi-rate capabilities. In this paper, we introduce a transmitter design (and associated techniques) that employ an all-digital baseband line-up that utilizes only one single-rate clock. Thus, keeping the analog hardware to a minimum and providing the maximum possible flexibility through digital programmability, in order to efficiently support multi-mode (i.e., various modulation schemes) and multi-rate (i.e., various bit-rates) capabilities. The telemetry standard is defined in the IRIG 106-04 specification document published by the Range Commanders Council (RCC) government telemetry group [1]. The Telemetry standard supports several modulation schemes all of which fall under the general modulation family of continuous phase modulation (CPM). Out of such a family of modulation schemes, the work presented in this paper focuses on two modulation schemes as examples, namely, SOQPSK and the PCM/FM. However, this does not limit the scope of the ideas and techniques proposed in this paper. We present various design techniques as well as implementation considerations. We also present actual measured results using a test-bed and a synthesizer IC that have been developed in our laboratories. Finally, we compare the measured results with simulations in order to validate the performance of our implemented design.