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Hard Limiting
| Fundamentals | |
|---|---|
| Title | Hard Limiting |
| Author(s) | J.A Ávila Rodríguez, University FAF Munich, Germany. |
| Level | Advanced |
| Year of Publication | 2011 |
During the design of the GPS M-Code different multiplexing options were considered to achieve a constant envelope [P.A. Dafesh et al., 2006][1]. Together with the majority voting, hard-limiting of the C/A Code, P(Y) Code and M-Code signals was another considered option.
The hard-limiting approach basically forces the non-constant envelope of the sum of C/A Code and M-Code on one phase and P(Y) on the orthogonal phase (assuming we want to place the M-Code on the same phase as the C/A Code) to be constant by limiting the variation of the amplitude to its minimum value. The problem though is that the C/A Code and M-Code suffer from significant power losses and distortions. Indeed, the total efficiency of the hard-limiting modulation is roughly of 83 % as shown in [P.A. Dafesh et al., 2006] [1], what corresponds to approximately 0.8 dB of overall combining losses. Moreover, the power split between the different signals is not easy to achieve.