Simultaneous telemetry and PN ranging transmission through UQPSK modulation: system analysis

The current CCSDS standard for simultane- ously transmitting high-rate telemetry (60 ksps-2 Msps) and ranging in scientific missions is based on a scheme that is not bandwidth efficient and creates spectrum management havocs. The new schemes under consider- ation are based on the regenerative PN ranging format [4] and on suppressed carrier modulation. Here the UQPSK (Unbalanced Quaternary Phase Shift Keying) solution is analyzed: the telemetry sym- bols and the ranging code chips are transmitted with different rates and powers on the in-phase and quadra- ture channels, respectively. This scheme results to be suitable for telemetry rates lower than 2 Msps with neg- ligible impact on the telemetry signal and a small in- crease of the ranging acquisition time (factor 1.6). Ad- ditionally, an optimum value of the power ratio is found around 15 dB.