Other

Lojack Operating Company, LP

Orest Fedan

Stephen Bourque

A battery protection system with a voltage sensing circuit for sensing the voltage of a battery and disconnecting all loads from the battery, including the voltage sensing circuit itself, when the voltage of the battery drops below a preset limit or when a battery charger is connected to the battery. The battery protection system reconnects the voltage sensing circuit upon disconnection of the battery charger.

Battery protection system

A wireless microphone with the remote transmitter using a duplicate of the radio frequency determining circuits of the radio receiver to insure that the remote transmitter frequency tracks the temperature drift of the radio receiver frequency, and also with a compressor to reduce the dynamic range of the sounds captured by the microphone. The superheterodyne radio receiver having small size and low current consumption by wiring the elements of the receiver in series rather than in parallel with the battery avoiding the use of switching regulators and also by using the same amplifier to amplify the antenna signal and the local oscillator signal and by adjusting the local oscillator current based on the strength of the received radio signal. The wires between the radio receiver and the speaker are part of the antenna for the radio receiver.

Miniature wireless communication system

A SAW resonator filter including a SAW resonator, and a first inductive reactance in parallel with the SAW resonator for shifting the null points below and above the center frequency for establishing substantially symmetrical attenuation about the center frequency.

Surface acoustic wave resonator filter

An improved fast settling bit slicing comparator circuit includes a comparator having a non-inverting and inverting input; the non-inverting input receiving an input signal; a filter circuit for receiving the input signal and being connected with the inverting input of the comparator; a positive feedback circuit interconnected between the output of the comparator and the non-inverting input of the comparator for introducing a predetermined hysteresis offset; the filter circuit including a filter resistance and filter capacitance having a reduced time constant sufficient to compensate for at least a portion of the hysteresis offset. Additionally, the positive feedback circuit may be interconnected with the inverting input of the comparator through the filter circuit for gradually reducing the effect of the hysteresis offset by reducing the differential voltage between the inverting and non-inverting inputs.

Fast settling, bit slicing comparator circuit

A notched SAW image frequency rejection filter system includes a SAW filter having an input, an output and a ground output and an impedance matching network including a first matching inductance connected to the SAW filter output and a second matching inductance connected to the ground output of the SAW filter; the SAW filter having an inherent internal capacitance that produces a predetermined capacitive leakage current at the image frequency; an inherent internal inductance that produces an inductance leakage current at the image frequency; and a boosted inherent parasitic ground inductance at the ground output of the SAW filter for generating a voltage across the second matching inductance to produce a compensation current which is substantially opposite in phase and substantially matched in magnitude with the capacitive leakage current for reducing the capacitive leakage current and increasing the image frequency rejection.

Notched saw image frequency rejection filter system

Dual table temperature compensation for a voltage controlled crystal oscillator is achieved by sensing the temperature of the voltage controlled crystal oscillator (VCXO), retrieving from a first table the frequency error with variations in the temperature sensed, retrieving from a second table the oscillator control voltage corresponding to the frequency error from the first table and applying the oscillator control voltage to the VCXO.

Dual table temperature compensated voltage controlled crystal oscillator system and method

An object detector which illuminates an area with a pulsating beam of light and measures light reflected back by an object in the beam. The light source is chopped by three different chopping frequencies. The light detector uses the highest frequency to reject out of band ambient signals and noise, uses the middle frequency for synchronously detecting the reflected signal, and uses the lowest frequency to ratio the output to the noise floor. The light detector uses linear gain prior to filtering out of band ambient signals to avoid intermodulation effects. The light detector uses logarithmic gain after the filtering to avoid overload and transient effects, without requiring an automatic level control circuit.

Optical object detection having circuitry applying logarithmic function to the average of filtered output

A control system for a switching regulator which linearizes the relationship between the control input signal and the duty ratio of the pulse output. A logarithmic signal generator furnishes a logarithmically increasing signal to a comparator circuit. The comparator circuit compares the logarithmic signal to a control input signal and triggers a pulse generator such that the frequency of the pulses has an exponential relationship to the control input signal. The pulses are averaged and the average is subtracted from a reference signal. The result is then used as the input to the logarithmic signal generator. The resulting relationship between the duty ratio of the pulse output and the control input signal is linear.

Linearized duty radio, variable frequency switching regulator

Disclosed is an oscillator circuit comprised of a sharp bandpass filter having an input and an output; a linear gain stage having an input and an output, the output of the sharp bandpass filter being connected to the input of the linear stage; a limiter having an input and an output, the output of the linear stage being connected to the input of the limiter; and a feedback loop having an input and an output, the output of the limiter being connected to the input of the feedback loop and the output of the feedback loop being connected to the input of the sharp bandpass filter, wherein the improvement being comprised of the limiter being a symmetrical active clamp.

Growing community of inventors

Belmont, MA, United States of America

Orest Fedan