Modulation Transfer from TDMA On-Off Bursting to FM Carriers in Memoryless Nonlinear Devices: Part I - Power Spectra

The modulation transfer noise caused by the "on-off" bursts of TDMA signals is modeled and analyzed in detail. Expressions of the power spectra of the RF and the baseband modulation transfer noise have been obtained for the most general case of
L
TDMA and
N
FM carriers in a zero-memory nonlinear amplifier such as a helix-type TWTA. From these general expressions, the RF power spectrum and the baseband modulation transfer noise onto the FM carriers can be readily computed. It is shown that there are only line spectra and no continuous spectrum in the modulation transfer noise caused by the TDMA on-off bursting. The separation of the spectral lines is equal to the TDMA frame rate. The maximum of the power spectrum of the modulation transfer noise is inversely proportional to the square of the TDMA frame duration and is independent of the separation between TDMA and FM carriers. The modulation transfer noise is in general a complicated function of TDMA burst levels, burst patterns, burst lengths, FM carrier levels, carrier sizes, device nonlinearities, and operating points.