Abstract: An odd order N-pole, (N-1)/2 zero elliptic filter (300) is provided having (N-1)/2 BAW resonators (302 and 304). The first Bulk Acoustic Wave (BAW) resonator (302) operates at a first mode number and a first center frequency and the second BAW resonator (304) operates at a second mode number, and a first center frequency. Operating BAW resonators (302 and 304) at differing modes allows the unwanted passbands (201) of the first BAW resonator (302) to be attenuated by the stopband of the second BAW resonator (304) and vice versa.

Abstract: The present invention relates to a monolithic crystal filter having a passband of at least 30 Khz and a center frequency greater than 120 Mhz. This filter includes a piezoelectric substrate, a plurality of input electrodes conductively coupled together via a thin coupling bar, a plurality of output electrodes conductively coupled together via another thin coupling bar, and at least one common electrode disposed opposite to the plurality of input and output electrodes. The input and output electrodes are aligned on the substrate such that they electroacoustically couple along a crystallographic axes thereof. Multicoupling is provided along another crystallographic axes via the plurality of conductively coupled input and output electrodes, respectively. As a result of multicoupling, fifth overtone mode operation is now possible.

Abstract: An overtone oscillator of the feedback type is provided by a transistor, a crystal resonant at a fundamental frequency and higher odd overtone frequencies, and a feedback circuit that includes the crystal, a second transistor connected in cascade with the first transistor and an RC network. This feedback circuit provides the correct phase shift to achieve and sustain oscillations at the desired overtone frequency.

Abstract: An audio processor for use in an angular modulation transmitter for performing pre-emphasizing, limiting, and low pass filtering functions. Novel pre-emphasis, limiter and low pass filter stages are disclosed.

Abstract: A direct FM modulator includes an oscillator comprising a current conducting device providing amplification to sustain oscillations and a frequency determining circuit connected thereto for controlling the frequency of oscillation. The frequency determining circuit includes a piezoelectric element in series with a voltage variable capacitance and an adjustable capacitance coupled across this series combination. The capacitance of the voltage variable capacitance is changed by a modulating voltage to provide frequency deviation about the center frequency of oscillation. A frequency linearization of the crystal oscillator is provided by a selected value of capacitance coupled across the varactor and the capacitance value of the adjustable capacitance such that the frequency deviation vs. voltage is maximum at the initial reference bias voltage and is symmetrical about this reference bias.

Abstract: A network for temperature compensation of a crystal oscillator over an extended temperature range encompassing two points of inflection of the drift characteristic of an AT cut crystal. The oscillator is of the type having, in loop connection, an AT cut quartz crystal and a voltage variable capacitance device. The compensation network utilizes a three resistor, three thermistor electrical network for generating a temperature dependent bias voltage applied to the variable capacitance device to compensate for changes in the self-resonant frequency of the crystal due to temperature variation. A method for determining the component values for the compensation network is also disclosed.