The monopole slot as a two-port diversity antenna for UHF land-mobile radio systems

Urban land-mobile communication systems designed to operate over the upper portion of the UHF band are very susceptible to frequent wide signal variations. Deep fades arise due to the presence of many obstructions in the propagation path between the transmitter and receiver. One way to combat the effects of Rayleigh fading due to multipath propagation is to provide a diversity combiner in the mobile receiving system with two signals, each containing the same information, which fade independently of one another. Such a system can virtually eliminate deep fades from the receiver output. Described herein is a method of obtaining two diversity branches, with independent signals if so desired, from a single two-port antenna which is both well matched to the transponder and efficient over the land-mobile frequency band from 820- 890 MHz. A directive pattern is associated with each port. When operating with a direct wave, signal gain over an omnidirectional antenna is therefore possible.