Abstract: The invention provides an apparatus and a method for determining the frequency of a radio frequency signal. The coherency of a received signal is determined and only the frequency of a coherent signal is determined. Zero amplitude transitions of coherent signals are counted in respective time periods. If the counts in each time period agree within a quantization error, the accumulated counts for a fixed time period are employed to determine a frequency. The frequency determining apparatus and method are particularly useful with a frequency agile radio receiver for detecting the presence of radio frequency signals from nearby mobile and stationary transmitters. Upon determination of the frequency of the nearby transmitter, the channel of transmission can be determined from a memory within the receiver and the receiver can be tuned to monitor the transmission. Additional tests to verify the frequency determination may be applied using squelch and window detector circuits of the radio receiver.

Abstract: A method and apparatus provide for monitoring radio frequency signals and, in conjunction with the monitoring, determining frequency of a received dominant radio frequency signal. Zero amplitude transitions of the signal are counted in primary and secondary sampling periods to determine frequency and frequency stability. The method and apparatus can be used to tune to radio frequency signals having frequencies in a list of frequencies to be monitored and detecting signals in the radio frequency spectrum on other frequencies. The monitoring and scanning may occur simultaneously, sequentially, or in any order or sequence. The frequencies of dominant signals received are determined and added to the list for monitoring. The receiver may be tuned to a frequency determined immediately upon determination of the frequency determined, after storage of the frequency determined, only after a signal on the currently monitored frequency terminates, or upon other conditions.

Abstract: A method and apparatus provide for monitoring radio frequency signals and, in conjunction with the monitoring, determining frequency of a received dominant radio frequency signal. Zero amplitude transitions of the signal are counted in primary and secondary sampling periods to determine frequency and frequency stability. The method and apparatus can be used to tune to radio frequency signals having frequencies in a list of frequencies to be monitored and detecting signals in the radio frequency spectrum on other frequencies. The monitoring and scanning may occur simultaneously, sequentially, or in any order or sequence. The frequencies of dominant signals received are determined and added to the list for monitoring. The receiver may be tuned to a frequency determined immediately upon determination of the frequency determined, after storage of the frequency determined, only after a signal on the currently monitored frequency terminates, or upon other conditions.

Abstract: The invention provides an apparatus and a method for determining the frequency of a radio frequency signal. The coherency of a received signal is determined and only the frequency of a coherent signal is determined. Zero amplitude transitions of coherent signals are counted in respective time periods. If the counts in each time period agree within a quantization error, the accumulated counts for a fixed time period are employed to determine a frequency. The frequency determining apparatus and method are particularly useful with a frequency agile radio receiver for detecting the presence of radio frequency signals from nearby mobile and stationary transmitters. Upon determination of the frequency of the nearby transmitter, the channel of transmission can be determined from a memory within the receiver and the receiver can be tuned to monitor the transmission. Additional tests to verify the frequency determination may be applied using squelch and window detector circuits of the radio receiver.