Abstract: An audio FM transmitter is disclosed that may achieve high-precision frequency control as well as compact size and low cost by enabling FM modulation using a fractional-N type PLL circuit.

Abstract: In a periphery monitoring system for monitoring movements of a mobile object around an installation location of a Doppler sensor, a signal output from the Doppler sensor is subjected to an FFT analysis, and a total sum of the frequency levels of all of the frequency bands obtained through the FFT analysis is calculated at predetermined time intervals. A reference level and abnormal level are set based on the calculated total sum. If the calculated total sum exceeds the abnormal level and falls to or below the abnormal level before a first set period passes since the exceeding of the abnormal level, the periphery status is determined to be abnormal. If the total sum exceeds the abnormal level but does not fall to or below the abnormal level even after the first set period passes since the exceeding of the abnormal level, the periphery status is determined to be normal, and the reference level is updated to a new reference level set based on total sums calculated during the first set period.

Abstract: In a periphery monitoring system for monitoring movements of a mobile object around an installation location of a Doppler sensor, a signal output from the Doppler sensor is subjected to an FFT analysis, and a total sum of the frequency levels of all of the frequency bands obtained through the FFT analysis is calculated at predetermined time intervals. A reference level and abnormal level are set based on the calculated total sum. If the calculated total sum exceeds the abnormal level and falls to or below the abnormal level before a first set period passes since the exceeding of the abnormal level, the periphery status is determined to be abnormal. If the total sum exceeds the abnormal level but does not fall to or below the abnormal level even after the first set period passes since the exceeding of the abnormal level, the periphery status is determined to be normal, and the reference level is updated to a new reference level set based on total sums calculated during the first set period.

Abstract: A compact and lightweight wireless microphone and transmitter. The transmitter is connected to the microphone using a standard connector. The transmitter includes a low-frequency amplifier for amplifying a received voice signal and a surface acoustic wave oscillator providing a high-frequency oscillation signal. A modulator combines the amplified voice signal and the high frequency oscillation signal into a modulated signal. The modulated signal is amplified using a high-frequency amplifier to create a high-frequency modulated signal. The high-frequency modulated signal is output as radio waves through an antenna. A power supply is included for powering the transmitter. To improve sound quality, the transmitter additionally includes a compander circuit for improving signal-to-noise ratio and increasing a dynamic range through a logarithmic compression algorithm.

Abstract: A compact and lightweight wireless microphone and transmitter. The transmitter is connected to the microphone using a standard connector. The transmitter includes a low-frequency amplifier for amplifying a received voice signal and a surface acoustic wave oscillator providing a high-frequency oscillation signal. A modulator combines the amplified voice signal and the high frequency oscillation signal into a modulated signal. The modulated signal is amplified using a high-frequency amplifier to create a high-frequency modulated signal. The high-frequency modulated signal is output as radio waves through an antenna. A power supply is included for powering the transmitter. To improve sound quality, the transmitter additionally includes a compander circuit for improving signal-to-noise ratio and increasing a dynamic range through a logarithmic compression algorithm.

Abstract: A wireless microphone use UHF band carrier FM transmitter adopting a PLL system, which has a voltage controlled crystal oscillation type modulator (VCXO) for performing FM modulation on an oscillation frequency of a crystal oscillation circuit by an input of a modulation signal AF of an acoustic signal and which uses an FM modulated signal fr obtained from the VCXO as a reference signal Vr to be input to an analog phase comparator (PC) of a PLL circuit 60. The PC performs a phase comparison operation at a high speed (10 MHz or more), therefore a cutoff frequency of a loop filter (62) may be a high band frequency of about 100 KHz to 1 MHz so that the cutoff frequency considerably higher than the highest audible frequency 20 KHz can be selected. The filter output moves at an inaudible frequency and therefore there is no audible noise generated even due to vibration, feedback, etc.