Apparatus and method for radio channel selection

An improved radio communication system of the type wherein a first radio has a transmission section, a receiving section and a tuning section for tuning sequentially at a relatively slow rate to each in a set of carrier frequencies for transmission of a test signal and a second radio has a transmission section, a receiving section and a tuning section for tuning sequentially at a relatively higher rate to each in the set of frequencies for detecting the test signal, the improvement comprising:

• first control means coupled to switch and control the operation of the first radio;
• first tuning means coupled to the first control means and to the tuning section of the first radio and responsive to the control means for tuning the first radio at a variable rate;
• means coupled to the first control means and to the transmission section of the first radio and responsive to the first control means for generating a continuously cycling test signal to be transmitted by the first radio on a carrier frequency, each cycle comprising a plurality of time periods wherein the test signal assumes the form of a plurality of tones, the total time of the cycle not exceeding the time spent by the second radio tuned to any carrier frequency for receiving the test signal;
• means coupled to the first control means and to the receiving section of the first radio for detecting an answer signal transmitted by the second radio;
• second means coupled to switch and control the operation of the second radio;
• second tuning means coupled to the second control means and to the tuning section of the second radio and responsive to the second control means for tuning the second radio at a variable rate;
• means coupled to the second control means and to the receiving section of the second radio for detecting the test signal and for evaluating, with the aid of the test signal, the signal-to-noise ratio of each carrier frequency on which the test signal is detected and for indicating to the second control means the value of the signal-to-noise ratio;
• and
• means coupled to the second control means and to the transmission section of the second radio and responsive to the second control means for generating an answer signal to be transmitted on the carrier frequency having the highest signal-to-noise ratio.

A radio communication system comprising:

• a first radio comprising a tuning section for tuning to each of a set of carrier frequencies taken at one rate for transmitting a test signal, and further for tuning, after each test signal transmission on a carrier frequency, to each frequency in the set taken at a higher rate for detecting an answer signal;
• a second radio comprising a tuning section for tuning at the higher rate to each carrier frequency in the set for receiving the test signal, and for transmitting the answer signal after the test signal has been detected on separate transmissions of the same carrier frequency;
• and
• at least two channel selection means, one selection means connected to each radio to control the operations thereof, each channel selection means including:
• means for automatically controlling the operation of the radio and for automatically controlling the production of signals, the control means coupled to switch the radio between transmission and reception;
• signal generating means coupled to the radio transmission section and to the control means and responsive to the control means for generating a signal comprising a plurality of tones;
• signal detecting means coupled to the radio reception section and to the control means for detecting a signal comprising a plurality of tones and for evaluating, with the aid of the signal the transmission quality of a carrier frequency on which the signal was detected;
• and
• tuning means coupled to the radio tuning section and to the control means and responsive to the control means for tuning the radio at varying rates.