Abstract: An RF filter includes elongate radiator elements constructed from printed circuit board (PCB) materials and using PCB fabrication techniques. The radiator elements are spacedly disposed and contained within a shielded enclosure. The filter apparatus has input and output leads exterior to the filter to pass a signal to be filtered. The filter is tuned by the shape and of the elongate radiator elements and shielded enclose and by conductive leads extending from the shielded enclosure toward the elongate radiator elements. The shape and number of the conductive lead elements may be varied to control RF coupling between radiator elements and the tuning of the filter.

Abstract: Apparatus for and method of processing received signals for use with multiple antenna spatial diversity receivers used in a digital communications system. The receiver has received signal phase modulator apparatus for each diversity received signal. The phase modulator provides a two state phase perturbation of zero or pi radians, based on the carrier frequency, which is switched to modulate the phase of the received signal for a fifty percent duty cycle over a symbol period.