A wide-band inverse-sine phase modulator is demonstrated. The modulator has application in a LINC amplifier for linear amplification at microwave frequencies using commonly available saturating amplifiers or injection-locked oscillators. A bandwidth greater than 10 MHz at a carrier frequency of 96 MHz with distortion products 40 dB or greater below desired components has been shown. The distortion behavior as a second-order effect of the loop delay as predicted by analysis has been verified. The output of the inverse-sine phase modulator and its conjugate, generated by a second phase modulator, were subtracted as in a LINC amplifier, to provide at least 40-dB suppression of the zeroth order and even-order components.

It is observed that the estimation of mean signal strength in the mobile radio environment has inherent uncertainties. These may not influence the observed distribution of the mean signal strength but would certainly mask efforts to obtain level crossing rates and duration of fades. A new parameter, duration of stay, is defined which appears to be insensitive to the granular variations of the mean signal strength and would be helpful in the determination of the switching rate in a base station diversity system.

A theoretical and experimental comparison of performance has been made between two types of predetection switching space diversity mobile radio systems. This comparison was made at a frequency of 840 MHz using simulated Rayleigh fading for a vehicle speed of about 80 mi/h. The switch diversity system was a conventional receiver antenna switching technique with two simulated physically separated receiving antennas and a single transmitting antenna. The feedback diversity system used a single receiving antenna with two simulated physically separated transmitting antennas. The transmitting antennas were switched remotely from the receiver. The difference in the performance of the two systems was shown to be primarily due to time delay inherent in the remote antenna switching technique.