| Any ranging system based solely on carrier phase measurements has an operational range limit. Beyond this limit the range measurements become ambiguous and must be resolved. This thesis proposes a dual band direct sequence spread spectrum signal with a structure that allows the carrier cycle ambiguity to be resolved in a three step procedure. A preliminary receiver design that is capable of reporting a range from the proposed signal is presented and evaluated.; In order to simplify construction and reduce the component count the receiver design substitutes simple digital logic blocks for more complex standard direct sequence components. Further simplification is achieved by implementing fast digital signal processing techniques based on a hard-limited sampling approach. The performance of the design was investigated by simulating the three most significant blocks; the IF receiver architecture, the acquisition/tracking block, and the phase measurement block.; It was determined that for the receiver to provide a measurement with a tolerance of less than 1 degree (1sigma) the final downconverted signal must have an energy peak at least 13 dB higher than the noise floor. This compares favourably to signal strengths present at the outputs of existing receivers incorporating the same transceiver chip used in this design. To successfully resolve the ambiguity it was found that, in addition to the above minimum required energy peak, the phase incoherence between transmitter and receiver must not be maximized. If it was maximized the success of the code phase tracking circuitry would be mitigated and resynchronization would be required before the carrier cycle ambiguity could be fully resolved. |
