Recognition of a special UQPSK modulation type in TDRSS telemetry and command system

The Tracking and Data Relay Satellite System(TDRSS) is a novel space-based tracking, telemetry and command system, which represents a new direction in the international tracking telemetering and command field. The UQPSK modulation was employed in the forward standard signal system of TDRSS, which in-phase channel transmitted information data, and orthogonal channel transmitted the ranging signal. Because of the ranging signal needs less power in transmission, the more power is distributed to information data. Compared to QPSK modulation the power efficiency was improved double, namely 3dB. The Traditional UQPSK modulation has the same code bit rates in the two quadrature channels. But as the two channels transmit different data, so the bit code rates would be different between the in-phase channel and the orthogonal channel. This difference would cause the diversity in the UQPSK modulation signal´s spectrum character. But there are very few studies about recognizing this special UQPSK modulation type in the existing public papers. Therefore it has important significance for studies of this special UQPSK modulation type. Considering this, in this paper we introduced the theoretical basis of the UQPSK modulation and theoretically analyzed the signal feature, then compared the UQPSK modulation´s spectrum which had the same bit code rates or not. Lastly proposed an algorithm based on square spectrum structure for this special UQPSK modulation type. Numerical simulations verify the algorithm availability.