Abstract: A digital microphone includes: a cavity resonator operatable in a micrometer, millimeter, or electromagnetic waveband, the cavity resonator having a metal wall including a conductive membrane 32 that vibrates in response to incident acoustic waves and converts the shift of the membrane 32 into a resonance frequency of the cavity resonator; an FM-signal generator that modulates the resonance frequency of the cavity resonator in response to the shift of the membrane 32 and outputs FM signals from the metal wall other than the membrane; and a ??-modulated-signal generator that generates ??-modulated signals from the FM signals. The FM-signal generator includes a slot 36, a micro-strip line 38, and a negative resistive element 40. The ??-modulated-signal generator includes an edge detector 42.

Abstract: A digital microphone includes: a cavity resonator operatable in a micrometer, millimeter, or electromagnetic waveband, the cavity resonator having a metal wall including a conductive membrane 32 that vibrates in response to incident acoustic waves and converts the shift of the membrane 32 into a resonance frequency of the cavity resonator; an FM-signal generator that modulates the resonance frequency of the cavity resonator in response to the shift of the membrane 32 and outputs FM signals from the metal wall other than the membrane; and a ??-modulated-signal generator that generates ??-modulated signals from the FM signals. The FM-signal generator includes a slot 36, a micro-strip line 38, and a negative resistive element 40. The ??-modulated-signal generator includes an edge detector 42.

Abstract: A digital microphone comprises a ?? modulator. The ?? modulator has a resonator including a membrane which vibrates by receiving a sound wave and a wiring pattern disposed opposite to the membrane, an oscillator, including the resonator, for outputting an FM signal according to the vibration of the membrane, and a one-bit quantizer for outputting a one-bit quantized signal by sampling the FM signal with a high-frequency clock.

Abstract: The present invention provides a ?? modulator of a frequency modulation system that can lessen the requirement of linearity for an oscillator. A ?? modulator comprises an oscillating apparatus that changes a frequency thereof according to an input signal, a quantizing means for quantizing a frequency modulation signal output from the oscillating apparatus, and an operation means for applying an operation to a digital signal output from the quantizing means. The oscillating apparatus comprises an oscillator that changes a frequency thereof according to the input signal, a reference signal source that outputs a reference signal at a predetermined frequency, a mixer that receives the signals from the oscillator and the reference signal source, and a low-pass filter that passes a low frequency component of a signal output from the mixer. The center oscillation frequency of the oscillator is set higher than a target center oscillation frequency of the frequency modulation signal.

Abstract: A digital microphone comprises a ?? modulator. The ?? modulator has a resonator including a membrane which vibrates by receiving a sound wave and a wiring pattern disposed opposite to the membrane, an oscillator, including the resonator, for outputting an FM signal according to the vibration of the membrane, and a one-bit quantizer for outputting a one-bit quantized signal by sampling the FM signal with a high-frequency clock.

Abstract: The present invention provides a ?? modulator of a frequency modulation system that can lessen the requirement of linearity for an oscillator. A ?? modulator comprises an oscillating apparatus that changes a frequency thereof according to an input signal, a quantizing means for quantizing a frequency modulation signal output from the oscillating apparatus, and an operation means for applying an operation to a digital signal output from the quantizing means. The oscillating apparatus comprises an oscillator that changes a frequency thereof according to the input signal, a reference signal source that outputs a reference signal at a predetermined frequency, a mixer that receives the signals from the oscillator and the reference signal source, and a low-pass filter that passes a low frequency component of a signal output from the mixer. The center oscillation frequency of the oscillator is set higher than a target center oscillation frequency of the frequency modulation signal.

Abstract: A &Dgr;-&Sgr; converter comprises a &Dgr;-&Sgr; modulator and a digital filter. The &Dgr;-&Sgr; modulator has a comparator having two resonant tunnel diodes connected to each other in series between two terminals and a field effect transistor connected in parallel to one of the resonant tunnel diodes, a conversion input transistor for converting an input voltage into electric current, a capacitor provided so that charge amount thereof is decreased by flow of electric current through the conversion input transistor and an electric potential proportional to the charge amount is used for the input electric potential to the comparator, and a feedback transistor, to which an output of the comparator is inputted, operating in such a way as to increase the charge amount of the capacitance element when the output of the comparator becomes a high level.

Abstract: A semiconductor elements having N-type negative resistance characteristics are connected in series to obtain a series circuit. The two ends of the series circuit serve as drive voltage terminals to which periodic drive voltages are applied. At least one of the semiconductor elements has a control electrode to which a voltage is applied to change the peak current. A connection point between the two semiconductor elements serves as an output terminal.

Abstract: A reduction starter employing a planetary gear type reduction gear mechanism having an outer ring gear displaceable radially of a common axis of a central sun gear and an output shaft carrying planet gears for revolution about the common axis. The outer ring gear is formed by an internally toothed ring gear elastically deformable to assure uniform distribution of load torque to all planet gears. The tooth root bending stress of the ring gear is substantially equalized to the outer periphery bending stress thereof to improve the load performance of the planetary gear type reduction gear mechanism and thus reduce the size and weight of the starter. The outer ring gear has an outer rim of a radial thickness t and a plurality of radially inwardly extending teeth each having a height h. The rim thickness t is determined to'fall with a range of from +.ltoreq.0.8 h to +.gtoreq.0.4 h.