Abstract: A system for single path processing identical, substantially identical, close or interfering frequencies with a single analog-to-digital converter. The system receives a plurality of input signals at various frequencies and front end circuits filter out first and second frequencies. A mixer and a front end oscillator are in communication with one of the front end circuits for mixing a front end frequency with one of the first and second frequencies prior to the analog-to-digital converter. A summer combines the output of the mixer with the output of one of the front end circuits. An analog-to-digital converter is connected to the summer for converting the analog input signal to a digital output signal. The first and second frequencies may be separately processed after they have been combined, even if they were identical frequencies.

Abstract: A system for detecting and removing undesirable noise, such as beats and tones, from radio signals. The system includes a manual oscillator that is a manually tuned by a user to a selected manual frequency from one of a plurality of frequencies. An electronic oscillator is electronically tuned to a selected electronic frequency from one of the plurality of frequencies. A processor isolates and stores at least one interference frequency associated the selected electronic frequency and determines a correction signal to correct any interference frequencies within a particular selected electronic frequency. The selected manual frequency is corrected using the determined correction signal for the particular selected electronic frequency when the selected manual frequency is the same as the particular selected electronic frequency.

Abstract: A system for single path processing identical, substantially identical, close or interfering frequencies with a single analog-to-digital converter. The system receives a plurality of input signals at various frequencies and front end circuits filter out first and second frequencies. A mixer and a front end oscillator are in communication with one of the front end circuits for mixing a front end frequency with one of the first and second frequencies prior to the analog-to-digital converter. A summer combines the output of the mixer with the output of one of the front end circuits. An analog-to-digital converter is connected to the summer for converting the analog input signal to a digital output signal. The first and second frequencies may be separately processed after they have been combined, even if they were identical frequencies.

Abstract: A system for detecting and removing undesirable noise, such as beats and tones, from radio signals. The system includes a manual oscillator that is a manually tuned by a user to a selected manual frequency from one of a plurality of frequencies. An electronic oscillator is electronically tuned to a selected electronic frequency from one of the plurality of frequencies. A processor isolates and stores at least one interference frequency associated the selected electronic frequency and determines a correction signal to correct any interference frequencies within a particular selected electronic frequency. The selected manual frequency is corrected using the determined correction signal for the particular selected electronic frequency when the selected manual frequency is the same as the particular selected electronic frequency.

Abstract: An FM radio receiver comprises a radio frequency tuning circuit for selecting a frequency modulated signal from an antenna and a local oscillator tuning circuit for tuning to an oscillating signal so as to convert the frequency modulated signal to an intermediate frequency. In the radio frequency tuning circuit, a capacitance variable ratio is set so as to be capable of receiving continuously the frequencies of both a first FM receiving band used in Japan and a second FM receiving band used in the US and Europe. The local oscillator tuning circuit is so constructed that an inductance value and a capacitance variable ratio can be switched so that the receiver is set to lower heterodyne for reception in Japan or upper heterodyne for reception in the US or Europe. As a result, a single receiver design can be configured for reception of FM radio broadcasting in either Japan or the US or Europe using a common front-end circuit, without increasing the number of components.

Abstract: An AM radio receiver includes search tuning such as seek or scan tuning features whose stop thresholds for locking onto a received frequency are adapted to environmental conditions. In the preferred embodiment, wideband signal strength, preferably derived from the automatic gain control of the radio frequency amplifier, provides a representative signal to the microprocessor for adapting the thresholds used during search tuning. The thresholds are increased when significant energy is present in the AM band and proportioned to the level of that energy. The decision logic of the microprocessor adapts thresholds according to the tuned signal strength, to wideband signal strength, to nighttime operation during which ionosphere conditions increase transmissibility of distant radio signals, and to intermediate frequency (IF) count validity to reduce the probability of stopping on audibly noisy frequencies when the RF signal environment is noisy.