Abstract: A communication device (104) includes a radio frequency power amplifier (202) and a bias circuit (204). The power amplifier (202) includes a depletion mode MESFET (214) for RF power amplification. To properly bias the MESFET (214) in a circuit including logic components powered by a conventional battery (136), the bias circuit (204) includes a level shifter (223) to provide the necessary gate-to-source voltage for the MESFET (214). To maintain the RF output power from the communication device (104) constant over temperature, the bias circuit (204) output voltage varies over temperature to track the temperature variation of the MESFET (214).

Abstract: A communication device (100) employs a local oscillator (104) having an improved charge pump circuit (122). The charge pump circuit (122) has current mirrors (204, 208) in which a first transistor (224, 270) is biased to provide a substantially constant current. A resistor (226, 272) selectively conducts a reference current to bias a mirror transistor (228, 274). The current mirror (204, 208) provides improved dynamic performance thereby reducing global phase error of the communication device (100).

Abstract: The radio frequency transceiver was developed for use in a time division duplex (TDD) radiotelephone communication system. The transceiver includes a local oscillator which generates at least two local oscillator signals at different times. Each local oscillator signal has a unique frequency. During a first time period, the radio frequency transceiver receives a radio frequency signal. The first radio frequency signal is combined with one of the local oscillator signals, forming an intermediate frequency signal. During a second time period and substantially during the first time period, the transceiver generates a frequency offset signal. The frequency offset signal is combined with the second local oscillator signal, forming a second radio frequency signal. The intermediate frequency signal and the offset frequency signal are designed to have different frequencies to avoid the self-quieting problem inherent in a TDD communication system.

Abstract: A radio communication device (103) provides several radio communication services including radiotelephone service, electronic mail service, faxing service etc. . . . The radio communication device has a main body housing element (107) and a movable housing element (109), radio circuitry (113), a touch screen display (119), and a switch (127). In a closed position, the radio communication device (103) has a first set of limited radiotelephone functions such as phone number input and sending and receiving phone calls. In an opened position, the radio communication device (103) has a different set of user functions which include radiotelephone functions, advanced radiotelephone functions, and messaging functions. The switch (127) provides a signal responsive to the movable housing element (109) moving to the open position. Thus, switching the radio communication device (103) between a first set of user functions and the second set of user functions.

Abstract: A programmable voltage controlled attenuator (100) meets the dynamic range and gain requirements for various communication protocols using a single bias generator circuit (104). A control voltage input, Vcnt, and a slope select input provide the dynamic range and attenuation for a voltage controlled attenuator (VCA) (109.).

Abstract: A correlation circuit (200) for detecting a correct phase for data bits in a received data stream includes a clock generator (204) configured to generate a plurality of clock signals, each clock signal having a predetermined unique clock phase. A plurality of data correlators (210, 212, 214, 216, 218, 220) generate respective pass indications when respective unique clock phases are adequate for accurate detection of the data bits in the data stream. In response to the pass indications, a control circuit (206) provides a clock signal for clocking the data. The control circuit (206) includes a delay block (278) and decision logic (270) for selectively delaying one clock phase of the generated plurality of clock phases. The control circuit may provide one of the generated clock phases or a delayed clock phase for clocking the received data.

Abstract: An improved speech coder provides a more natural sounding replication of speech by modifying the mean-squared error criterion for the selected speech coder parameters. Specifically, the modification emphasizes the signal components that the speech coder has difficulty matching, i.e. the high frequencies. This emphasis is constrained to certain limitations to avoid over-emphasizing the speech.

Abstract: A Vector-Sum Excited Linear Predictive Coding (VSELP) speech coder provides improved quality and reduced complexity over a typical speech coder. VSELP uses a codebook which has a predefined structure such that the computations required for the codebook search process can be significantly reduced. This VSELP speech coder uses single or multi-segment vector quantizer of the reflection coefficients based on a Fixed-Point-Lattice-Technique (FLAT). Additionally, this speech coder uses a pre-quantizer to reduce the vector codebook search complexity and a high-resolution scalar quantizer to reduce the amount of memory needed to store the reflection coefficient vector codebooks. Resulting in a high quality speech coder with reduced computations and storage requirements.

Abstract: A method for synchronizing communication between a transmitting unit (102) and a receiving unit (104) in a telecommunication system (100) includes calculating a reverse checksum for the received data. At the transmitting unit (102), data including a length indicator is serially transmitted. At the receiving unit (104), the data are received and stored in a buffer. A checksum is calculated beginning with the last-received data while maintaining a length count. When the checksum verifies and when the length count matches the transmitted length indicator, the received data is considered valid and communication is considered synchronized.

Abstract: An electronic circuit (412) comprises a biasing circuit (414) and an amplifier (416). Biasing circuit (414) biases amplifier (416) with a first current when a supply voltage of electronic circuit (412) is within a predetermined voltage range corresponding to a first supply voltage, and biases amplifier (416) with a second current when the supply voltage is within a predetermined voltage range corresponding to a second supply voltage. The first current and the second current provide separate operating points for amplifier (416), operating points which may, upon design, provide substantially the same operating characteristics. The operating points change with the supply voltage in order to minimize power dissipation. Electronic circuit (412) is suitable for use in an integrated circuit, where it can be used in various electronic systems which provide different supply voltages or have a potential for using lower-voltage technology in the future.