Abstract: A resynchronization method for use in a communication system, such as a second generation cordless telephone system 800, begins by determining that synchronization has been lost by a receiving unit (830). The receiving unit than mutes any transmit data and generates zero data which is combined with a pattern generated by pattern generator (812). The transmission is then received by handset (830), which detects the pattern generated by pattern generator (812) using pattern detector (850). Pattern detector (850) then generates a pattern detected signal (852) which causes handset (840) to also stop sending data and generate a pattern accompanied by zero data. Base station (830) detects the pattern and again generates another pattern accompanied with zero data which is transmitted to handset (840). Handset (840) after decoding the pattern for the second time begins to resumes the normal transmission of data to base station (830).

Abstract: A base site circuit (38) for operating in a communication system (10) having a plurality of base sites capable of allocating a communication channel for use by a communication unit (16) in response to a communication channel request from the communication unit. The base site circuit includes a receiver (34) that operates in a low sensitivity mode when there are no communication channel requests received, and that operates in a high sensitivity mode which is activated by a control signal. The base site further includes a transmitter (34) which is activated by the control signal and a control circuit (32) coupled to both the receiver and the transmitter, for controlling the receiver and the transmitter. The control circuit (32) provides the control signal to the transmitter and to the receiver, in response to a communication channel request.

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 receiver (10) is provided where an information signal (11) is received (12) and examined to determine (20) its signal strength. When the signal strength is at least equal to a threshold, an unmodulated signal (40) is added to the received signal to improve the sensitivity of the receiver.

Abstract: A method for re-establishing a communication link that has been lost between a portable unit (406) and a fixed unit or base station (402) provides for a way of quickly re-establishing the lost communication link, on the previously used RF channel. The method is begun by transmitting a link re-establishment code word (900) using MUX 1 after determining that synchronization has been lost (502) for a predetermined period of time (504). This is followed by automatically switching the portable unit (406) from MUX 1 to MUX 3 communication protocol. Followed by re-establishing communication (re-establish synchronization) between the portable (406) and base station (402) in MUX 3 and switching the two communication devices (402 and 406) back to MUX 1 after the communication link has been re-established. The same steps can be followed by base site (402) if it had been the first to detect loss of the communication link.

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: An electronic device (100) operating on a battery voltage (126) is disclosed having a regulator (108) for producing a first reference voltage (106) and a second reference voltage (110). The electronic device (100) includes an A/D converter (114) for comparing the battery voltage (126) to the first reference voltage (106) to produce a first sample. The A/D converter (114) also compares the second reference voltage (110) to the first reference voltage (106) to produce a second sample. The two samples are then subtracted at a micro-computer (112) to produce a difference sample. The micro-computer (112) compares the difference sample to a first value and detects low battery conditions when the difference sample is below the first value.

Abstract: A base station allocates radio channels to radio telephone handsets in a second generation cordless telephone (CT2) communication systems by scanning each channel in a first band, and scanning each channel in a second band to measure an RSS level for each channel scanned. The base station scans the second band at a rate that is substantially faster than the rate at which it scans the first band. If a link request is received on a first channel within the first band, from a calling radio telephone, the base station determines whether the first channel has an RSS level above a predetermined threshold. If the RSS level of the first channel is above the threshold, and the calling radio telephone handset is capable of operating on the second band, the base station re-assigns a second channel, that is within the second band, to the calling radio telephone handset.

Abstract: A method and apparatus for choosing the most optimum communication channel in a system (100) having a plurality of communication channels provides for reduced interference and increased system capacity. By establishing a set of threshold levels and comparing these threshold levels to receive signal strength level measurements for each of the communication channels, a communication device originating a call can be guaranteed of establishing communication using the communication channel with the least chance of being affected by interference or of affecting other channels already in use.

Abstract: A low profile antenna includes a rectangular driven element and a rectangular ground plate spaced from the driven element. A coaxial transmission has its center conductor connected to an end of the driven element and its ground connection connected to the end of the driven element spaced from the center conductor connection. An inductance is coupled between the coaxial cable shield and the ground plate.

Abstract: A low-profile antenna for operating in the 800 to 900 mHz range and especially suited for use with portable, hand-held electronic apparatus. The antenna features printed circuit board construction for precision fabrication, broadband operations and enhanced efficiency. The antenna includes a driven element in close association with a parasitic element printed on one surface of the printed circuit board in a side-by-side, parallel relation. A conductive strip is included on the other side of the board spanning the free ends of the driven and parasitic elements to enhance the coupling therebetween.

Abstract: An antenna switch (302) includes a radio terminal (R) and first and second antenna terminals (A1 and A2). When the second antenna terminal (A2) is unterminated, the radio terminal (R) is coupled to the first antenna terminal (A1). When the second antenna terminal (A2) is connected to a remote antenna system (304), the switch automatically couples the radio terminal (R) to the second antenna terminal (A2). Thus, the switch does not require a separate control terminal (C) and control signal to switch between the first and second antenna terminals. Instead, the switch is controlled by the presence or absence of a DC current at the second antenna terminal (A2). The remote antenna system includes a remote antenna (308) and a low pass filter (310) coupled between the remote antenna and ground. An alternate embodiment is described which includes a DC amplifier (402).

Abstract: A low profile antenna comprised of a driven element and a parasitic element spaced above a ground plane. The driven element is connected at one end to the feedpoint of the radio device to which it is attached, the opposite end thereof being free. The parasitic element is connected to the ground plane by its end nearest the feedpoint, the opposite end thereof being free. In the preferred embodiment the parasitic element length and the driven element length are both approximately equal to a quarter wavelength at the operating frequency.

Abstract: A low profile antenna comprised of a driven element and a parasitic element spaced above a ground plane. The driven element is connected at one end to the feedpoint of the radio device to which it is attached, the opposite end thereof being free. The parasitic element is connected to the ground plane by its end nearest the feedpoint, the opposite end thereof being free. In the preferred embodiment the parasitic element length and the driven element length are both approximately equal to a quarter wavelength at the operating frequency.