Abstract: An adaptable homotropic antenna system for use with a portable communication transceiver is described. The antenna system can be used for reception or transmission and can be completely enclosed within the portable transceiver housing. The homotropic antenna system evaluates the quality of a received signal and if the signal is below a predetermined threshold level, an alternate antenna will be selected. The antenna system will continue to sample the available antennas until an antenna produces a signal of acceptable quality.

Abstract: A circuit and technique for directing an adaptable antenna system is described. The invention is coupled to the output of an RF receiver configured to provide a data signal output, and evaluates the quality of the receiver data signal. The invention switches antennas when the signal quality deteriorates below a predetermined level.

Abstract: A battery door latching mechanism comprising two cantilevered posts incorporated in the base housing of a radio receiving device that interface with a headed rib on the base of a battery door. A recessed area in the battery housing surrounds the two cantilevered members, and prevents them from becoming overstressed due to deflection during shock, yet allowing them to deflect enough for attachment of the battery door to the housing.

Abstract: A low profile antenna comprised of a driven element and a parasitic element spaced above a ground plane. The driven element is connected at one end to the feedpoint of the radio device to which it is attached, the opposite end thereof being free. The parasitic element is connected to the ground plane by its end nearest the feedpoint, the opposite end thereof being free. In the preferred embodiment the parasitic element length and the driven element length are both approximately equal to a quarter wavelength at the operating frequency.

Abstract: A radio receiver from antenna to detector designed to be realized substantially on an integrated-circuit chip comprises a single tunable oscillator and a plurality of mixers. An input signal from an antenna is connected as an input to a first mixer and mixed with a signal derived from the oscillator. The signal may be taken directly, may be multiplied to a desired level or may be divided to a desired level. A particular output from the first mixer is selected by a first tunable filter. The output of the first tunable filter is taken as an input to a second mixer where it is mixed with a second signal derived from the oscillator. The process of mixing and application of the mixed signal to a tunable filter to select a desired frequency is continued as needed until the signal is reduced to a desired intermediate frequency range where it is amplified as needed to a level sufficient to drive a discriminator.

Abstract: An assembly for a pager having a main housing that is generic to a family of papers having different outputs. A subassembly housing contains the output circuitry for each member of the family of pagers. A generic circuit is mounted on a circuit board that is slideable within the main housing between a first and second position. The circuit board, in a first position, allows the subassembly housing to mate with the main housing. The subassembly housing is locked into mated engagement with the main housing when the circuit board is slid from its first position to its second position. The locking engagement is provided by a tongue-like projection mounted on the circuit board which is received by a cavity in the subassembly housing when the circuit board slides to its second position. In conjunction with this flange mounted on the subassembly housing engages a first end of the circuit board.

Abstract: A wide area coverage radio communication system of the type adapted to relay a message substantially simultaneously from a plurality of fixed location sites to a plurality of portable or mobile units includes a plurality of repeaters at each of the sites. Each of the repeaters is arranged to transmit and receive on a respective different frequency duplex pair or channel. Control means at one of the sites senses channel availability at all of the sites and causes one repeater at each of the sites to transmit the message on its respective different frequency. Access to the system by the portable units is provided on a trunked basis through the control means.

Abstract: A shock absorbing mechanism for protecting a fragile quartz crystal includes a Teflon coating on the internal surface of the crystal enclosure. The enclosure is provided with a plurality of detents arranged so that when the crystal is shocked in its most fragile plane a plurality of these Teflon coated detents are struck simultaneously to distribute the shock across the surface of the crystal.

Abstract: A programmable bias circuit for use with a data limiter circuit is described. The limiter and bias circuit are coupled to a portable data receiver which is adapted to communicate in a coded system. Frequency disparities between a transmitted word sync signal and the portable data terminal local oscillator signal will cause a DC offset voltage in the received data signal. The programmable bias circuit is controlled by a decoder within the portable data terminal. If the terminal is in an idle state, the programmable bias circuit will be set to rapidly follow offset voltage shifts until a transmitted word sync signal has been detected. After word sync has been detected, a slower, more stable time constant circuit is programmably activated for the duration of the digital data message. The fast time constant circuit is activated at the end of the received data signal.

Abstract: A high gain vertically polarized antenna section includes a hollow conductive central cylinder which is used to encase feed lines and power dividers used for feeding the antenna section. The cylinder is surrounded by an array of symmetrically disposed vertical radiating elements arranged in a plurality of symmetrical columns. A plurality of ring transmission lines or shorted quarter-wave stubs are utilized to distribute electrical energy to each of the vertical radiators in a manner such that the instantenous current flow is in the same direction in all of the vertical radiating elements. Any horizontal currents in the ring transmission lines or shorted quarter-wave is substantially cancelled by out-of-phase horizontal currents.

Abstract: An improved multiple frequency digital phase-locked loop circuit is described. The improved digital phase-locked loops utilizes a single circuit to effect both phase and frequency adjustments. The multiple frequency digital phase-locked loop effects phase adjustments by selectively combining or subtracting a reference clock signal with a derived programmable clock signal thereby generating a composite digital phase-locked loop clock signal. The multiple frequency provides frequency adjustments by selectively adding or subtracting pulses from the composite clock signal at a rate determined by a programmably controllable clock signal. The improved multifrequency digital phase-locked loop is suitable for use as a tone detector with the addition of a lock detector wherein the phase-locked loop can be programmed for a plurality of known operating frequencies.

Abstract: A unitary phase and frequency adjust network for use in a multiple frequency digital phase-locked loop circuit is described. The unitary phase and frequency adjust network utilizes a single circuit to effect both phase and frequency adjustments. The multiple frequency digital phase-locked loop effects phase adjustments by selectively combining or subtracting a reference clock signal with a derived programmable clock signal thereby generating a composite digital phase-locked loop clock signal. The phase and frequency adjust network effects frequency shifts by selectively adding or subtracting pulses from the composite clock signal at a rate determined by a programmably controlled clock signal.

Abstract: A method and corresponding apparatus for maintaining constant bandwidth over a frequency spectrum in a microwave, dielectric resonator waveguide filter. Bandwidth is determined by the product of the resonant center frequency and the interresonator coupling coefficient. To maintain constant bandwidth while changing center frequency, the interresonator coupling coefficient must be chosen such that it varies inversely with changes in center frequency. The interresonator coupling coefficient is a function of the physical dimensions of the waveguide and the dielectric resonators, the dielectric constant and the spatial location of the resonators within the waveguide. Once the physical and spatial parameters have been established, the center frequency of the filter may be adjusted by altering the thickness of the resonators without changing the filter bandwidth.

Abstract: A double-sided flexible electronic circuit module is provided having a flexible printed circuit board. The flexible circuit board has a plurality of conductive paths on each surface and a plurality of conductively plated-through apertures being connected to the conductive paths. One side of the flexible circuit board is adapted to carry components with leads; the other side of the flexible circuit board is adapted to receive components without leads. A carrier member, larger than the flexible circuit board and of a size and shape sufficient to accommodate the placement of at least one flexible circuit board, is also provided. The carrier member has a plurality of apertures which are in alignment with the apertures of the flexible circuit board, and a plurality of elongated slots in predetermined positions which extend the entire width of the flexible circuit board which is temporarily affixed onto the carrier member.

Abstract: There is disclosed a new and improved frequency modulation system and method for providing a frequency modulated signal which varies in frequency from a center frequency in response to the amplitude of an analog modulating signal. The system and method utilizes a frequency shift synthesizer to provide the frequency modulated signal and digital techniques for quantizing the amplitude modulating signal and providing dividing factors to the frequency shift synthesizer responsive to the amplitude quantization.

Abstract: A method and corresponding apparatus for maintaining constant bandwidth over a frequency spectrum in a microwave, dielectric resonator waveguide filter. Bandwidth is determined by the product of the resonant center frequency and the interresonator coupling coefficient. To maintain constant bandwidth while changing center frequency, the interresonator coupling coefficient must be chosen such that it varies inversely with changes in center frequency. The interresonator coupling coefficient is a function of the physical dimensions of the waveguide and the dielectric resonators, the dielectric constant and the spatial location of the resonators within the waveguide. Once the physical and spatial parameters have been established, the center frequency of the filter may be adjusted by altering the thickness of the resonators without changing the filter bandwidth.