Channel switching device for mobile radio communication equipment

• US 3,913,017 A
• Filed: 03/28/1974
• Issued: 10/14/1975
• Est. Priority Date: 03/28/1973
• Status: Expired due to Term

• Current Assignee: Kazuo Imaseki
• Original Assignee: Kazuo Imaseki
• Inventors: Imaseki, Kazuo
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Hearn, Robert
• Application Number:
  US05/455,836
• Time in Patent Office: 565 Days
• Field of Search: 325/18-21,16,25,52,64,56,301-307,312-314,333-335,464,51,53,54 340/147A,147B,147C,147F,147G,147LP,150,182,184,412,171 343/200,201,205 179/41A
• US Class Current: 455/422.1
• CPC Class Codes: H03J 5/24 with a number of separate pretuned tuning circuits or separate tuning elements selectively brought into circuit, e.g. for waveband selection or for television channel selection
• CPC Class Codes: H04W 48/18 Selecting a network or a communication service

Abstract

A channel switching device for use in a mobile radio communication system is disclosed. The device is intended for use in systems wherein the service area is divided into a plurality of zones each having a fixed base station and each accommodating a plurality of mobile stations. The base stations have a plurality of frequency-divided communication channels exclusively assigned to them. The mobile stations are provided with a detector and a switching circuit which are responsive to the received signal to controllably switch between channels. When the received signal exceeds a predetermined threshold, only the channels assigned to the zone in which the mobile station is located are selectively switched or scanned. On the other hand, when the received signal falls below the threshold, all the channels in the service area are scanned.

Claims

1. In a mobile radio communication system covering a service area divided into a plurality of zones each having a fixed base station and each accommodating a plurality of mobile stations, each base station having a plurality of frequency-divided communication channels exclusively assigned to it, the improvement in said mobile stations comprising:

a receiver and a transmitter having a common local oscillator input, detecting means responsive to a signal received by said receiver for comparing said received signal to a predetermined threshold, channel switching means responsive to said detecting means for controllably switching between channels assigned to a zone in which said mobile station is located when said received signal exceeds said threshold and for controllably switching between all the channels in the service area when said received signal is below said threshold, said channel switching means including switched local oscillator means for supplying local oscillation frequencies for all the channels in the service area to said common local oscillator input, said switched local oscillator means having a plurality of crystal resonators, and matrix means for selectively energizing one of said crystal resonators, and counter means for selectively controlling said matrix means, said counter means including a reversible counter, a clock pulse source for incrementing or decrementing said reversible counter, and addition/subtraction control means responsive to said detecting means for controlling said reversible counter to add or subtract pulses from said clock pulse source.

2. The improvement as recited in claim 1 wherein said reversible counter is a binary counter and said matrix means converts the binary count accomulated in said reversible counter to an output corresponding to a specific channel.