The diversity receiver including plural antennas and one receiver comprises a detector means to detect a signal voltage responsive to an antenna output from an IF amplifier of the receiver and a comparator which is supplied with the signal voltage separated in two courses, one including a fixed bias applying circuit and the other including a time constant circuit, so as to select one of the antennas which is in a good receiving condition.
A portable radio used with this invention has two different types of antenna, such as a monopole antenna and a loop antenna. The diversity reception system continuously selects that one of the antenna which provides the better received signal. Antenna selection is performed such that the received signal level is compared with two or more preset threshold levels, and antennas are switched when and only when the received signal level fails to satisfy certain predetermined conditions.
An automotive radio system employs a plurality of corrective actions in response to the detection of multipath interference to reduce distortion audible to a listener. The speed of the vehicle is determined since the number of multipath events per unit time and the expected duration of each multipath event vary according to vehicle speed. The corrective action taken in response to detection of multipath interference depends upon the vehicle speed. In a diversity antenna system, antenna switching is suspended at high vehicle speed while filtering of the audio output to reduce noise is suspended at lower vehicle speeds.
An antenna diversity receiver with a variable delay time for antenna switching is disclosed. The antenna diversity receiver includes an antenna selective switching means for coupling one of a plurality of antennas to a RF receiver input. A multipath detector controls the antenna selective switching means. A switching disabling means automatically disables the antenna selective switching means over a disabling period. In order to accurately immunize the receiver the disabling period is controlled by an adjacent channel detector to increase the period with increasing adjacent channel interferences and to decrease the period with descreasing channel interferences.
Antenna selection control apparatus for a diversity antenna system including at least two antennas. The received power strength is measured from a selected antenna and compared with a reference power level. The reference power level is adjusted depending upon the signal to noise ratio of received signals, and if the selected antenna falls below the adjusted threshold another antenna is selected.
An antenna diversity technique for use in wireless personal communications is disclosed. In the so called microcellular phone environment, fading in signal reception is an important consideration. A new way of performing the antenna diversity involves antenna switching during a period of data reception which may results in minimum bit hits to data. The system only requires single receiving part.
