Abstract: A cellular phone having a fixed calling capacity limiting use of the phone to emergency situations. Two call sequences are stored in memory permitting telephonic communication with only the two fixed sites associated with the two call sequences. Telephonic communication must be effectuated with a first fixed site, and then terminated, prior to effectuation of telephonic communication with a second fixed site. Telephonic communication with a second fixed site is permitted during a predetermined, limited time period.

Abstract: A linear-to-exponential converter circuit for generating a temperature-independent signal which is exponentially related to an input signal. An amplifier stage forming an exponential multiplier is comprised of a bipolar junction transistor which, characteristic of bipolar junction transistors, generates a current at a collector electrode which is dependent upon temperature. A signal to be amplified by the expontential multiplier formed of the bipolar junction transistor is first provided to a temperature compensation circuit. The temperature compensation circuit introduces a temperature dependency upon the input signal which is the inverse to that of the temperature dependency of the bipolar junction transistor of the amplification circuit. The temperature dependency of the amplified signal is removed, and a temperature-invariant signal is produced thereby.

Abstract: System and method for determining an absolute phase value of a differentially-encoded, DQPSK signal. A stored set of sequences of an ID sequence is compared with a received ID-sequence of a differentially-encoded, DQPSK signal transmitted to the receiver. The stored and the received ID sequences are correlated, and the stored values of the ID sequence are adjusted by the value of the calculated correlation.

Abstract: A low pass filter circuit for a radiotelephone which filters harmonic, spectral components of a modulated signal generated by the radiotelephone. The filter circuit is comprised of inductors and capacitors wherein each inductor and each capacitor of the filter is comprised of a distributed-element portion and a discrete-element portion. The distributed element portions of each inductor and each capacitor of the filter attenuate higher-frequency, spectral components of a signal applied thereto. The discrete element components of each inductor and each capacitor of the filter attenuate lower-frequency, spectral components of the signal applied thereto.

Abstract: A gain control system for controlling signal levels of the signal received by a receiver. The gain control system is operable to control the signal levels of the signal when the signal is comprised of either a conventional, constant envelope signal, such as an FM signal, or a non-constant envelope signal, such as a TDMA composite modulated signal. The gain control system may be advantageously embodied in a dual-mode radiotelephone operable to receive both conventional, FM signals and TDMA, composite modulated signals.

Abstract: A capacitive power supply for powering a portable electrical device, such as a radiotelephone. The capacitive power supply is comprised of capacitors stacked vertically in a series connection of capacitive values capable of generating currents of levels great enough to power a radiotelephone for an extended period of time.

Abstract: A method and apparatus for detecting the state of charge of a battery during charging or discharging thereof. Voltage levels across the battery are measured during battery charging or discharging, and compared with preset values representative of a normal battery characteristic charge or discharge curve. The normal charge or discharge curve is modified responsive particular battery characteristics indicated by measured battery voltage levels, and, preferably, also responsive to measured battery temperature levels to form a modified normal battery charge or discharge curve. The modified normal battery charge or discharge curve is divided into curve portions defined by voltage levels and rates of changes of the voltage levels. Each curve portion defines a particular state of charge of the battery.

Abstract: A dielectric block filter assembly which is surface-mounted upon a circuit board. The circuit board includes an opening formed to extend therethrough, and parallel-extending projecting members, formed of a portion of the printed circuit board, which extend into the opening formed to extend through the circuit board. The dielectric block filter includes a bottom mounting surface having notches corresponding to the projecting members. Each notch includes a seating surface for seating against corresponding ones of the projecting members in mated engagement therewith.

Abstract: A fractional-N type frequency synthesizer (700) for use in a radiotelephone (901). The synthesizer (700) utilizes multiple latched accumulators (401, 403, 405, 407), within an accumulator network, to perform multiple integrals of an input signal (439). The outputs of the accumulators are combined in series to form a data output signal (453). The data output signal (453) is input to a divider network (703) and used as a variable divisor of the frequency input from a variable oscillator (701) into the divider network (703).

Abstract: A battery charger for charging a nickel metal hydride battery with a fast charging current. The battery charger is operative to step-down, or constantly reduce, the magnitude of a charging current applied to a nickel metal hydride battery as the temperature level of the battery increases during charging thereof. As the temperature levels of the battery exceeds preset values, the magnitude of the charging current is reduced. When the temperature levels of the battery exceeds a maximum value, application of a fast charging current is terminated, and a trickle charging current is applied to the battery.

Abstract: A frequency control system for a dual-mode radiotelephone (152-238; 252-320) operative to receive either an FM signal or a DQPSK signal. In a first embodiment, when operative to receive the FM signal, the frequency of the reference oscillator (192) of the radiotelephone (152-222) is maintained in a fixed relation with the frequency of the FM signal. When operative to receive the DQPSK signal, the reference oscillator (192) is maintained in a fixed relation with the frequency of the DQPSK signal as determined by a digital signal processor (212). In a second embodiment, when operative to receive the FM signal, the frequency of an offset control oscillator (320) is maintained in a fixed relation with the frequency of the FM signal. When operative to receive the DQPSK signal, the reference oscillator (292) is maintained in a fixed relation with the frequency of the DQPSK signal as determined by a digital signal processor (312).

Abstract: A modulator circuit for generating a modulated, DQPSK signal. The modulator circuit includes an encoder for receiving a binary bit stream comprised of bit pairs defining differential phase changes. An encoder receives a bit stream of which bit pairs thereof define differential phase changes. The encoder encodes the bit pairs into codewords which are stored and then supplied to an I-accumulator, a Q-accumulator, and a memory element. The memory element contains pre-multiplied values which are supplied to the I- and the Q-accumulators which add terms of the pre-multiplied values to form I-portions and Q-portions of a DQPSK-modulated signal. The I- and Q-portions may then be supplied to a quadrature modulator.

Abstract: A keypad apparatus for a radio telephone has the keypad circuit (200) inked onto the lightpipe (105), thereby, allowing freedom in designing the shape of the keypad (103) and reducing the amount of circuitry required on the main circuit board (109) contained within the housing (107) of the radiotelephone.

Abstract: A method of generating a first signal (115) in a radiotelephone (101) representing the detection of speech on a second signal having background noise, a magnitude, a zero crossing rate and divided in time by frames having a predetermined time period. In absence of speech, the method characterizes the background noise (209) and computes background noise thresholds (211). The method computes an average of the magnitude of the second signal and a zero crossing rate of the second signal for a given frame (215). Then, compares said average of the magnitude (217) and said zero crossing rate (221) of the second signal to said background noise threshold. Upon one of said average of the magnitude and said zero crossing rate consecutively exceeding said background noise thresholds for a first predetermined number of frames, the transceiver(107) is turned on.

Abstract: The present disclosure includes a discussion of a power amplifier controller which powers up a power amplifier (203) without a substantial burst of frequency noise. The controller has a RF output power detector (211) which generates a signal (229) correllated to the power level of the power amplifier (203). This signal (229) is compared (215) to a reference signal (213) to determine if the power amplifier (203) is active. The signal (227) generated by this comparator (215) is used to determine the voltage level of the Automatic Output Control (AOC) signal (231).

Abstract: A housing assembly for supportively housing a circuit board in fixed engagement therewithin. The housing assembly forms a support surface for receiving the circuit board at an unlocked posiiton. Sliding translation of the circuit board is permitted upon the support surface to position the circuit board at a locked position. Translation of the circuit board causes elastic deformation of clamps which exert clamping forces responsive thereto to affix the circuit board in position at the locking position.

Abstract: A current mirror having improved turn-on and turn-off characteristics capable of operation an expanded voltage range. A cascode circuit comprising a portion of the current mirror is of a high characteristic impedance to increase thereby the voltages over which the current mirror may generate a constant current output. A switching circuit comprised of tandemly-positioned transistors having differing transistor characteristics decreases the transistor turn-on and turn-off times to enhance the characteristics of the current mirror.

Abstract: A signal weighting system for associating a confidence level with portions of a communication signal transmitted upon a multipath channel and received by a receiver. A signal received by the receiver is equalized by an equalizer circuit, such as a maximum likelihood sequence estimator, and the equalized signal generated thereby is supplied to an adaptive filter which is synthesizes portions of the multipath channel. The signal received by the receiver is altered responsive to values of a filtered, equalized signal generated by the adaptive filter.

Abstract: A dielectric filter assembly and mounting therefor. The mounting bracket forms a support surface and includes integrally formed strip members for interconnecting electrodes formed upon a face surface of the dielectric filter and a circuit disposed upon an electrical circuit board. Once interconnected, reflow solder connections are formed between the strip members and the electrodes and the strip members and the circuit disposed upon the circuit board. The strip member is then severed from the mounting bracket to electrically isolate the electrode disposed upon the face surface of the dielectric filter, while maintaining the electrical connection between the electrodes formed upon the dielectric filter and the circuit disposed upon the circuit board.

Abstract: A dielectric block filter construction having resonating cavities formed therein to form one half wave-wavelength resonators thereby. The resonating cavities span opposing side surfaces of the dielectric block forming the dielectric block filter to define openings at the opposing side surfaces. Outer surfaces of the dielectric block, including the opposing side surfaces having the openings defined thereat, are coated with an electrically-conductive material except for portions of one side surface of the dielectric block about peripheral surfaces of input and output couplers formed on the one surface. Because the opposing outer surfaces are coated with the electrically-conductive material, the opposing outer surfaces of the dielectric block are self-shielding to prevent propagation of electromagnetic radiation through openings defined by the resonating cavities of the dielectric block.