Abstract: A method and apparatus provides control of the gain of an input amplifier (306) in a radio receiver (300), such as in a radiotelephone handset (104). The radio receiver (300) includes an automatic gain control circuit (318). The automatic gain control circuit (318) includes a timer circuit (370) which provides asynchronous, digital automatic gain control circuit to perform a coarse gain adjustment. The automatic gain control circuit (318) further includes an integrator (366) which provides analog automatic gain control for providing remaining needed gain regulation. The automatic gain control circuit (318) provides substantial reduction in input signal acquisition time for the radio receiver (300).

Abstract: A method determines the signal usability of an adjacent channel in a multi-cell communication system without the aid of synchronization symbols. In general, a three step search is used to arrive at the adjacent channel signal quality. The first step is a coarse timing phase search. This is accomplished through a signal quality estimates (606). The second step arrives at the optimum time phase by first interpolating (608) the received signal around the time phase selected in the first step to generate additional samples. After the interpolation (608), signal quality estimates are calculated (610) for the time phases immediately surrounding the time phase found in the first step. The optimum time phase corresponds to the maximum of these quality estimates. Finally, in the third step, the signal quality estimate is calculated for the optimum time phase. This provides the adjacent channel signal quality estimate desired.

Abstract: Electronic devices using microprocessors requiring additional external memory can have security protection for the microprocessors while in an expanded mode of operation. A microprocessor having a security access circuit allows executable code to be stored in a peripheral storage device, such as external EPROM, while maintaining protection to the microprocessor EEPROM by monitoring if an instruction code is generated from an internal memory source or an external memory source.

Abstract: A tuning circuit for a reference oscillator (200) including voltage variable capacitors (222, 224) in a back to back configuration and providing a control terminal for voltage controlled tuning of the reference oscillator (200). Also included in the tuning circuit is a modulation bias circuit for modulating the reference oscillator (200).

Abstract: A radio having two architectural platforms integrated in one integrated circuit (IC). A synthesizer controller (312) selects between an offset local oscillator (LO) synthesizer (318) and a second LO synthesizer (316) to provide a common architecture for either an Frequency Division Duplex (FDD) or Time Division Duplex (TDD) system design while providing isolation between the two frequency sources. An offset LO signal (319) is translated to an isolated LO signal 310 and combined with a main LO signal (322) to provide the FDD platform. A second LO signal (314) is translated into the isolated LO signal 310 and combined with the main LO signal (322) to provide the TDD platform. The second LO synthesizer signal (314) is common to both systems in the receive mode.

Abstract: A transceiver (100) is provided for transmitting during the transmission bursts (12) of a frame and receiving during the receiving time-slot windows (14). The transceiver (100) includes a receiver (320) for receiving a repeating radio frequency data (16) signal at any time within the receiving time-slot window (14) and for demodulating the repeating radio frequency data signal down to a baseband data signal. A data detector and clock recovery device (330) recovers the valid data (CHMP) from the baseband data signal. For controlling the receiver (320) and data detector and clock recovery device (330), a control circuit (400) modifies the receiving time-slot windows (14) to only receive and detect when valid data is expected (52).

Abstract: A communication unit may operate in either a trunking communication system and a cellular communication system when the coverage areas of each system overlap. Typically, the communication unit is affiliated with the trunking communication system and operates normally therein. When a call is received or being placed via the cellular communication system, the communication unit transfers its affiliation to the cellular communication system and operates therein. The communication unit is prompted by the trunking communication system to transfer its affiliation for incoming calls and does so automatically for outgoing calls. Once the communication ends, the communication unit transfers its affiliation back to the trunking communication system within a predetermined period of time.

Abstract: A multi-bandwidth SAW filter for an input signal is provided which includes an SAW transducer having a selectable length corresponding to the desired bandwidth of the filter. The SAW filter is responsive to a control signal which corresponds to a selectable bandwidth of the filter to present the input signal to an appropriately lengthed SAW transducer.

Abstract: A digital communication device (10) comprises a signal quality detector (18) that determines the quality of the received signals and instantaneously mutes and unmutes the voice output (22) of the digital radio communication device when the quality drops below a selected level to prevent noise bursts from being heard by the user of the communication device.

Abstract: A transceiver (100) is provided for transmitting during the transmission bursts (12) of a frame and receiving during the receiving time-slot windows (14). The transceiver (100) includes a receiver (320) for receiving a repeating radio frequency data (16) signal at any time within the receiving time-slot window (14) and for demodulating the repeating radio frequency data signal down to a baseband data signal. A data detector and clock recovery device (330) recovers the valid data (CHMP) from the baseband data signal. For controlling the receiver (320) and data detector and clock recovery device (330), a control circuit (400) modifies the receiving time-slot windows (14) to only receive and detect when valid data is expected (52).

Abstract: A communication system 100 for determining the optimum direction (206) for transmitting and receiving a signal in a radio comprises a receiver for receiving a carrier signal being a time divided signal having an instruction signal, a transmitter for transmitting a time divided signal, a directional antenna (10) coupled to said receiver and transmitter, and a steering device (28) for changing the phase of the carrier signal in accordance with the instruction signal.

Abstract: A communication device (16) comprises first and second transceivers and apparatus for determining when the communication device (16) is in an on-site area (11) and when the communication device (16) is in an off-site area. The first transceiver transmits and receives signals on a first communication medium (17), when the communication device (16) is in a first area (11); whereas, second transceiver transmits and receives signals on a second communication medium (28), when the communication device (16) is in a second area.

Abstract: A radio communication device, having a receive mode and a transmit mode, includes a receiver portion, a transmitter portion, and multiple oscillators for providing reference waveforms for the radio communication device. During the receive mode, the receiver portion receives signals having a selected frequency, converts received signals to at least a first intermediate frequency (IF), and a transmitter oscillator produces a first waveform having a frequency equal to a multiple of the first intermediate frequency during the receive mode. During the transmit mode, the transmitter portion requires a reference waveform having an offset frequency equivalent to the first IF frequency to produce a radio frequency signal. Thus, the radio communication device also comprises a divider coupled to the transmitter oscillator for dividing the frequency of the first waveform to the required offset frequency in the transmit mode.

Abstract: Certain operational characteristics of a crystal (104) are measured during a testing and grading process. Once determined, information representing these operational characteristics are stored in memory (120) and utilized by a controller (122) to increment a phase increment register (114) upon determining the crystals ambient temperature via a temperature sensing circuit (124). The value stored in the phase increment register (114) is then sent to a phase accumulator (116) where successive phase increments are summed together. This summed value is in turn sent to a sine lookup table (118) where the instantaneous phase value is converted into sine amplitude. Finally, a digital to analog converter (126) converts the amplitude bit stream into an analog signal for use as a reference oscillator frequency having extremely high frequency resolution.

Abstract: A communication unit (10), capable of operating in either cellular or trunked communication modes, comprises a receiver (14), a transmitter (16), and a dual synthesizer (18), coupled to the receiver and to the transmitter. The dual synthesizer comprises a main synthesizer (124) and an offset synthesizer (132). The offset synthesizer comprises a phase modulator (131) and an offset voltage-controlled oscillator (134). A protocol controller (20) comprises modulator circuitry for modulating only the offset voltage-controlled oscillator when communication unit operates in the cellular mode, and for modulating both the phase modulator and the offset voltage-controlled oscillator when the communication unit operates in the trunked mode.

Abstract: A communication device (508) for use in a Time Division Multiplex (TDM) communication system (500) includes a transmitter, a receiver, and a frequency scanner for quickly scanning the radio frequency communication channels to determine an available channel. The communication device (508) also includes a phase locked loop (100) for providing a reference signal for the communication device (508) and locking to the available channel. This phase locked loop (100) includes a Voltage Control Oscillator (VCO) (104) having a control signal input (103). The phase locked loop (100) also includes a first filter (110) and a second filter (108). The first filter (110) has a wide frequency response. The second filter (108) includes a storage element (222) and has a narrow frequency response. The phase locked loop (100) also includes a switching circuit (106) which determines which one of the two filters (110, 108) gets coupled to the voltage control oscillator (104).

Abstract: A repeater (30) is provided for relaying communication between a subscriber unit (24) and a central station (10) when the repeater recognizes transmission from the subscriber unit to the central station but detects a lack of response by the central station to that subscriber unit or when the repeater recognizes a transmission from a subscriber unit (26) requesting the repeater for service. The repeater asks the central station for a channel upon which to communicate. Alternately, a predetermined channel may be used for the relayed communication.

Abstract: A centralized communication system controller (102) measures and stores a historical record of each subscriber unit's communication activity. By examining this historical record, the controller predicts the subscriber unit's communication activity over a future time interval. A code based upon this prediction is transmitted to the subscriber unit (110), which causes the subscriber unit to enter an energy saving mode and deactivate (208) non-essential circuits for a time period represented by the code. In this way, the duration of the "sleep" interval may be optimally varied based upon the subscriber unit's communication history. In another aspect of the invention, unexpected messages for a subscriber unit in the energy saving mode are stored (114) electronically until the conclusion of the "sleep" interval. This message storing function enhances system efficiency when the subscriber unit's communication history does not correlate with actual commuication traffic.

Abstract: This radio includes a port for communication with the radio and can be used for programming its memory in order to set the radio personality. A gate is provided for selectively enabling and disabling communication through the port. The gate is controlled by signals transmitted to the radio. A memory retains the last transmitted control signal.

Abstract: An improved communication system is disclosed wherein at least one reprogramming station is added to a communication system. The reprogramming station is constructed and arranged to communicate with the subscriber units thereby either reprogramming or regrouping them. The subscribing units receive the reprogramming command and acknowledge individually, altering a memory means until either reprogrammed back to the original state, or to another state. In another mode, the reprogramming station transmits a regrouping command wherein two or more groups are combined to form a super group.