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 current mirror circuit comprising a first current mirror circuit with a first error correction transistor connected between the base and collector of the first transistor of the first current mirror; a second error correction transistor connected to the first error correction transistor and a second current mirror circuit connected to an input current source and the base of the second error correction transistor. The second error correction transistor samples the signal from the collector of first error correction transistor and feeds its base current, which is almost equivalent to the base current of the first error correction transistor, to the input of the second current mirror circuit. The second current mirror circuit combines the input current source current with the base current of the second error correction transistor and generates a current which is fed to the collector of the first transistor of the first current mirror circuit.

Abstract: A selective calling, paging and priority signalling system for two way communications between at least one primary and a plurality of remote stations. An automatic selective calling mode is provided in which the primary station operator enters the address of the desired unit and activates his microphone. Unmuting data packet will then be transmitted to the addressed remote station, unmuting the remote station. When the transmission ends, a mute data packet is transmitted, remuting the remote station.

Abstract: In accordance with the present invention there is provided an auxiliary battery charging terminal that may selectively engage battery charging circuitry inside a portable radio pager. There is provided a current conducting cap having a downwardly and outwardly flared rim that deforms to lock under the crimped edge an insulating seal ring of a standard rechargeable cell by application of a compressive axial force. The auxiliary battery charging terminal is further provided with a central tip axially projecting upwardly from the cap. The auxiliary terminal may be further provided with a cap of reduced diameter to circumferentially engage the raised battery cathode terminal on the battery cell. A mating recess in a remote battery charging receptacle may receive the tip to captivate the battery cell against lateral displacement. The tip may be further provided with a rounded apex to relieve localized frictional forces upon insertion and removal of the battery cell from the remote battery charging receptacle.

Abstract: In accordance with the present invention there is provided an amplifier and integral signal shunt attenuator. The amplifier consists of an active amplifying device that is normally biased for signal amplification. The active amplifying device has a characteristic signal transfer impedance between its input and output and a characteristic signal shunt impedance across its input. The amplifier is configured such that the power dissipated by the active amplifying device may be limited. During transmission standby, the active amplifying device may be rebiased to lower the shunt impedance with respect to the transfer impedance. Thus, the undesirable signal is no longer fed-through the transfer impedance but is substantially shunted across the relatively low shunt impedance.

Abstract: A digital voice storage mobile control terminal adapted for use in multiple unit land mobile radio communications system. The mobile control terminal utilizes up to eight 64K dynamic RAMs to store up to 42 seconds of speech comprising up to eight separate messages as well as a CVSD encoder-decoder to digitize speech messages.

Abstract: An improved encoder/decoder circuit which utilizes a phase locked loop frequency synthesizer configuration to permit both encoder and decoder operation. In addition, a sampling filter detector is employed to permit monolithic integration of the circuit and minimize sensitivity to vibration. The sampling filter detector has digitally controlled bandwidth which permits rapid response to reverse burst turn-off. In addition, the circuit includes a pulse adder to implement an energy limited reverse burst turn-off mode.

Abstract: An improved channel scanning radio which automatically monitors a channel being monitored by the scanning circuitry at the time of the microphone is taken off-hook by treating that channel as a priority channel for a short period after the microphone is returned to the hang-up position. This permits the operator to automatically monitor a channel of interest without stopping the scan function.

Abstract: Apparatus for processing received Loran C signals and compensating for envelope cycle discrepancy (ECD). A measure of ECD is determined during the fine settle operation and compared to a reference value which is an average over a period of time. If the difference between the reference and the ECD measure is greater than a threshold, the decision made by the fine settle operation is rejected and the fine settle process is restarted. If the difference is less than the predetermined threshold the decision is accepted as being an accurate fine settle determination.

Abstract: A method for preparing a printed circuit board for mounting of surface mounted RF components such that the lead inductance of the components is minimized. The process consists of producing plated through apertures in the printed circuit board to create a component body hole with lead contacts extending to the edge of the component body hole. The resulting aperture is then blanked to remove portions of the metal lining to provide electrical isolation between the lead contacts while maintaining lead contacts that extend to the edge of the component body hole. A component is then soldered into position such that solder is wicked through the plated through apertures to create solder contact of the leads at the edge of the component body hole. This results in substantial reduction in lead inductance improving RF amplifier gain and stability and improving bandwidth characteristics.

Abstract: An absorptive resonant cavity filter suitable for use on the output of a transmitter power amplifier and capable of substantially constant predetermined resistive input impedance at all frequencies. The structure comprises a bandpass cavity which instead of an input coupling loop employs a conductor coupled from the input and configured along the wall of the cavity to form a transmission line of predetermined impedance and terminated by a resistor of similar impedance value.

Abstract: A shock-resistant low profile crystal package and internal crystal mounting apparatus capable of adequately protecting a multi-electrode crystal plate from high-G forces occasionally experienced by the mishandling of the particular article in which the component has been mounted. The crystal plate is positioned within an aperture of the base member and is supported about its edge during wire-bonding of the electrode pattern to the terminal connecting pins of the base member. Since the crystal plate is free-floating about its central position, the crystal can undergo thin film metallization of an electrode pattern from either side of the crystal plate to achieve desired frequency parameters. A ceramic retaining ring is placed on top of the crystal plate and the overall package is hermetically sealed by the welding of a cover to each end thereof.

Abstract: A digital voice storage system adapted for use in a multiple unit land mobile radio communications system. The system utilizes a PSK signalling system with fixed length data packets to control a system capable of multiple message storage of speech at mobile stations. Up to eight 64K dynamic RAMS are used in conjunction with a microprocessor to store up to 42 seconds of speech comprising up to eight separate messages. In addition, the system permits base interrogation of mobiles to determine if a message has been stored for review by the base operator and to determine the remaining recording capacity and total recording capacity of the mobile.

Abstract: A transmitter power control circuit which provides normal power control functions, and provides a high speed loop response when abrupt changes in output power are required. The circuit utilizes an electronic switch to provide adaptive filtering to permit narrow bandwidth filtering during normal steady state operation of the transmitter and wide bandwidth filtering during desired abrupt changes in transmitter power output. This allows rapid changes in transmitter output power when desired, while substantially eliminating undesired noise during normal operation.

Abstract: An improved digital demodulator and detector for phase-shift-keyed digital signals providing coherent detection with high sensitivity and stability on noisy channels. Digital sampling is used in conjunction with a digital phase locked loop system in which basic time increments are subtracted or added to an equilibrium timing loop to provide simultaneous carrier demodulation and bit recovery.

Abstract: A unique carrier data operated squelch for use with a demodulator detector for phase shift keyed digital signals. The counts transitions in the PSK signal by examining a narrow time window around the phase transitions. The number of data transitions that fall inside and outside the window is correlated with a predetermined threshold. The inventive carrier squelch permits parameter programmability and is particularly suitable for implemenation utilizing a microprocessor.