Abstract:
A transmitter architecture is disclosed which offers a new combination of signal shaping and power control which optimizes transmitter noise figure performance. The disclosed apparatus and method is implemented by separating the shaping element (303) from the power control elements (406, 412, 418) in frequency. Placing the shaping element (303) at a fixed intermediate frequency (IF) allows for the use of readily available, temperature stable shaping elements while distributing the power control elements (406, 412, 418) at radio frequency (RF) facilitates optimization of noise figure performance in the transmitter (200).
Abstract:
A transceiver (100) includes a radio frequency power amplifier (116) which is biased by an active bias circuit (110). Active bias circuit (110) provides a low cost bias circuit for amplifier (116) which adjusts the bias over changes in temperature and supply voltage levels to provide a constant output power. A set of control inputs (122-126) coming from controller (108) provide for power output level adjustement for the amplifier (116) in a frequency modulated (FM) environment and for both power and modulation level adjustments in an amplitude modulated (AM) environment.
Abstract:
A bi-level current limiting circuit is provided for purposes of maintaining safe battery operation in hostile or otherwise volatile environments. The bi-level current limiting circuit includes two sub-circuits, a first sub-circuit for establishing a maximum current level output from a battery pack into which the circuit is incorporated, and a second sub-circuit for establishing a steady state current level output.
Abstract:
A system and method for transmitting a facsimile message to one or more of a plurality of facsimile selective call receivers (40) each capable of decompressing a facsimile message on the basis of a facsimile codebook which is optimized for an image of a predetermined fixed resolution. In a processor (20) of the selective call terminal, the image of the facsimile message is segmented into a plurality of subimages (I1-In). Each subimage is compressed on the basis of the codebook to generate a compressed subimage for each subimage. A paging protocol signal is generated including information representative of the plurality of compressed subimages. At the selective call receiver (40), the decoder/controller extracts the information representative of the compressed subimages (CI1-CIn) and decompresses each compressed subimage on the basis of the stored codebook to display the facsimile message.
Abstract:
The present invention provides a unique access control scheme (100) for assigning a plurality of time slots in a fair manner among subscriber units (508, 514) using a single time slot in a frame and subscriber units (508, 514) using multiple time slots in a frame in a communication system.
Abstract:
A method and apparatus is provided for operating a radio communication system (100). The system (100) has a sequence of communication channels (205), including a reservation channel, and a channel hopping protocol for operating on the sequence (205). A hop period is defined for the channel hopping protocol. A transceiver (113) monitors the reservation channel to find an open communication slot (213), having a duration less than the channel hop period, and cyclically channel hops through the sequence of communication channels in the open slot (213). The transceiver (113) reserves the communication slot (213) for a subsequent cycle through the sequence by transmitting a reservation signal on the reservation channel.
Abstract:
A method and communication system (100) provide for automatic optimization of data throughput by adjusting the encoder (108) to use a long packet length and an increased channel coding efficiency during periods of low error counts and a short packet length and an increased channel coding redundancy during periods of high error counts.
Abstract:
A battery charging system (200) comprises a battery pack (206) and charger (202). Battery pack (206) includes a thermistor (212) for determining the temperature of battery pack (206) and a zener diode (210) in parallel with the thermistor (212) for informing charger (202) of the current capacity of battery (206) or of another battery parameter. Charger (202) includes a transistor (220) and zener diode (214) for effectively switching between measuring thermistor (212) and zener diode (210) at charger input terminal (224). This effectively reduces the number of battery and charger contacts required to measure two battery parameters as compared to the prior art.
Abstract:
A method and device for selectively reducing the frequency-temperature shift of piezoelectric crystals. The piezoelectric device (100) includes a substrate (102), a piezoelectric element (106) and a temperature-dependent interface structure (120) for beneficially stressing the piezoelectric element at a predetermined temperature range. The substrate (102), piezoelectric element (106) and temperature-dependent interface structure (120) define a piezoelectric package having a predetermined non-compensated third order Bechmann curve having a low temperature end and a high temperature end, with an inflection point trerebetween, whereby the frequency-temperature shift is reducible on the third order Bechmann curve.
Abstract:
Subscriber power levels are adjusted to enhance interference cancellation in a DS-CDMA communication system. A base-station (503) of the communication system receives signals from a plurality of subscribers (509-512) and evaluates each signal. Based on the evaluation, particular subscribers are commanded to control their power levels such that different predetermined targets for the particular subscribers are maintained. The predetermined targets include, but are not limited to, received power, frame erasure rate, bit error rate and signal quality. The resulting power levels received at the base-station (503) are substantially different, which is beneficially employed to enhance interference cancellation in the DS-CDMA communication system.