Abstract :
Mobile radio services in metropolitan areas suffer from congestion of relatively few channels. A necessary step toward maximum use of allocated channels is to provide access to some or to all of them by every mobile subscriber. A method for obtaining access to such a multiplicity of channels by relatively economic means, and thereby to obtain a trunking advantage, is discussed here. The channel generator makes use of two crystal-controlled oscillators, a modulator, a filter and a switch-controlled phase-locked oscillator. Coarse channel selection is obtained by means of a binary LC network. A fine tuning control, constant and independent of channel setting, avoids locking to adjacent unwanted frequencies. A transistor sampling switch has been used as a reliable phase discriminator avoiding DC amplifiers. Potential problem areas are discussed.
