Code Power Measurement Methodology for GPS Block IIR-M and IIF On-orbit Test Procedures

摘要

A new measurement methodology is presented for determining the C/A, P(Y) and M-code signal power levels in on-orbit tests of the modernized IIR (IIR-M) and IIF GPS satellites. This methodology is an extension of the prior methodology used by Stanford Research Institute International (SRI International) for the measurement of the C/A and P(Y) code power levels. A brief introduction into the code power methodology of SRI International is discussed, followed by the proposed modernization test procedure. With the aid of a constellation diagram (phase plot) of the in-phase (I) and quadrature (Q) signals, and several equations of the Coherent Adaptive Subcarrier Modulation (CASM) method (mathematically equivalent to the Interplex implementation), code power can be directly calculated. Code power calculations for both contractor implementations are also discussed, where M-code is modulated on either the in-phase or quadrature signal.