An interference cancellation type space diversity system transmits digital microwaves in a sure and stable manner. Signals coming in through two spaced antennas are combined together into a single input signal and the composite signal is processed by a demodulator into a baseband signal which is identical with a transmitted signal. The demodulated baseband signal is processed by a frequency/amplitude characteristic detector network, which comprises a correlation circuit and an identification circuit, thereby controlling output phases of the antennas.

An apparatus for performance improvement of a burst mode digital wireless receiver has a processing circuit for processing a plurality of received signals and providing a processed signal and a delay circuit for introducing a predetermined delay to the processed signal. The delay circuit is coupled to the processing circuit. The predetermined delay is such that the processed signal is delayed to correspond with a later data burst. The processing circuit weights and combines the received signals, where the processing circuit reduces a mean squared error of an output signal. The processing circuit weights and combines the received signals using a predetermined symbol pattern within a sync sequence within a time slot.

For diversity reception from a plurality of antennas, particularly in an automotive vehicle (FIG. 4), the respectively received signals are mixed with a local oscillator signal to form a plurality of IF signals (u.sub.1 . . . u.sub.n). The respective IF signals are weighted with a weighting coefficient which is derived from a sum circuit of all the IF signals, and the respective IF signal, which weighting circuit includes an integrator to minimize temporal variations in the amplitude of the sum signal. The sum signal forms the actual IF signal, for further processing, and demodulating to derive an audio signal. Preferably, the signals from the antennas are branched, and the branch signals phase-shifted 90.degree., which, again, are weighted by similarly generated weighting coefficients, and the weighted, phase-shifted signals are combined in the adding or summing circuit (70) to form said eventual IF signal for demodulation.

According to the receiving method for mobile reception has a plurality of individual receiving antennas, also known as diversity receiving method, on the individual antenna output signals an auxiliary modulation is superimposed and the antenna output signals are added to give a summation signal which as amplified selected intermediate-frequency summation signal is then demodulated in relation to amount and frequency or phase, the phase position of an individual signal in relation to the phase position of the summation signal and/or the amplitude contribution of an individual signal to the amplitude of the summation signal thereby being determined. This information is utilized for optimizing the useful signal with a view to optimum interference suppression for example in that the phases and/or amplitudes of the high-frequency individual signals are changed in dependence upon the phase position and/or amplitude contribution determined. With low circuitry expenditure this then gives a substantially improved reception quality in mobile systems. Receiving antenna systems for carrying out the method are described.

A diversity receiving system for differential detection of minimum shift key (MSK) signals. The system may be advantageously implemented in order to realize high quality mobile satellite communication systems where shadowing is a significant problem and channel bandwidth and power are constrained. Signals from each of a plurality of receiving branches are translated to different intermediate frequencies which differ from each other by multiples of the transmitted signal symbol rate. The intermediate frequency signals are summed and detected via a common differential detector, the latter being followed by a low pass filter having a bandwidth corresponding to a fraction of the symbol rate. The plural signals are easily and stabely combined at an intermediate frequency stage without phase adjusters, signal quality measurement circuits or switching controllers. Moreover, the error rate performance is equivalent to that of post detection equal gain combining diversity schemes, which require plural complete receiving systems.