An exact expression for the output autocorrelation function of an FM discriminator is derived when the input of the FM discriminator is an FM signal, cochannel interference and Gaussian noise. The modulating baseband signals for the FM signal and the cochannel interference are assumed FDM signals whose statistics are modeled by a stationary Gaussian random process. The interaction among signal, interference and noise are determined by which the NPR (noise-power-ratio) can be calculated.>

In transmitting a band-limited PSK/TDMA signal via satellite, the signal is distorted due to the nonlinearities of an earth station HPA and a satellite TWTA. To reduce the impairments due to these nonlinearities, a new TWTA linearizer, called a soft-limiter type linearizer (SL-LRZ), has been developed. The overall amplitude characteristic of a TWTA associated with an SL-LRZ is linear up to saturation and has a constant envelope beyond saturation. As to the AM/PM conversion characteristic, it has almost zero phase shift, irrespective of the operating point. The TWTA with SL-LRZ gives better bit error rate (BER) performance and less out-of-band emission (OBE) compared to cases where TWTA is operated by itself or with a conventional linearizer. In this paper, the impact of the new TWTA linearizer upon the transmission performance of a QPSK/TDMA signal is described. The transmission performance over a nonlinear satellite channel has been evaluated experimentally using a 120 Mbit/s QPSK modem and an INTELSAT V channel simulator.

The limitation in the effective use of the geostationary orbit is the intersatellite interference problem. A theoretical approach to realize an optimal usage of the orbit is provided in this paper, with particular attention to the constraints of service arcs, existence of spotbeam operating systems and different frequency plannings. The problem is formulated as a nonlinear programming problem and the sequential unconstrained minimization technique is applied to solve it numerically. Example computations are also given and various interference criteria are evaluated in terms of orbit utilization.

This paper provides a general analysis of the transmission characteristics of a coherent PSK signal, where anM-ary coherent signal is transmitted via a repeater system composed of a cascade ofNbandpass hard limiters. The probability density function of a composite phase of the signal and noise over the system is newly derived to obtain an error probability. In addition, the comparison with the repeater system composed of a cascade ofNlinear amplifiers is made to clarify the features of the transmission characteristics. It is found that the probability density function of the composite phase over the system is symmetric about each input carrier-to-noise power ratio (CNR), and it reduces to some well-known results. It is also shown that for a reasonably large input CNR in each stage, the presence of the bandpass hard limiter (BPHL) provides some improvement, but that for small input CNR it causes degradation in performance.