Abstract: A digital subscriber line (DSL) communication system that utilizes the high frequency band of a standard telephone line does not require the use of a plain old telephone service (POTS) splitter in the resident's home, which provided isolation between the POTS frequency band (0 to 4 kHz) and the DSL frequency band. A digital subscriber line modem utilizes either constant envelope modulation or quadrature amplitude modulation for outputting DSL signals upstream to a central office. When a telephone in the resident's home is detected as being off-hook, then the constant envelope modulation is used by the DSL modem in order to lessen the intermodulation product distortion that results in audible noise heard by a user of the telephone. When the telephone is on-hook, then another type of modulation, such as QAM, is used to maximize the upstream data rate capability in the DSL frequency band, since any noise generated by the QAM is not a problem due to the non-use of the POTS frequency band.

Abstract: A cordless telephone system connectable to the public switched telephone network having a base station and one or more handsets communicating with the base station by an RF link using a time division duplex direct sequence spread spectrum quadrature modulation technique, having a gain imbalance compensation system for balancing the gain between the I and Q channels. Gain imbalance estimation is performed as part of a calibration cycle when the handset is in the cradle of the base station. The controller of the unit causes another unit to send a data signal with a frequency error. The baseband receiver performs the operation .vertline.I.vertline.-.vertline.Q.vertline., which is an indication of gain error. The results are stored in an accumulator over a set period of time. The controller reads the accumulator and uses an iterative process, increasing or decreasing the gain link compensation until no gain imbalance error is obtained.

Abstract: A cordless direct sequence spread spectrum telephone using a direct conversion radio architecture wherein the code sequence used for spreading and despreading is an even code sequence to prevent addition of low frequency noise in the down-conversion process, the preferred even code being a 12-chip code and, more particularly, being an even 12-chip code that is generated by adding one bit to an inverted, shifted, and/or reversed 11-chip Barker sequence.

Abstract: A cordless telephone system connectable to the public switched telephone network having a base station and one or more handsets communicating with the base station by an RF link utilizing a DBPSK I and Q demodulator with a digital AGC loop. When R .angle..theta. is being received instead of I and Q data, the phase information (.angle..theta.) is connected to the I input of the DBPSK demodulator. The amplitude information (R) and the output of the digital AGC logic are applied as differential inputs to the Q input of the DBPSK demodulator. The I input to the AGC logic is set to zero. The Q input to the AGC logic is supplied with the R data. The AGC servo loop with the differential Q inputs to the DBPSK demodulator creates a high resolution A/D converter for R. The theta information is used to demodulate the incoming bipolar data, which may be either MSK or FSK, if a limiter-discriminator or other FM demodulator is used.

Abstract: A frequency acquisition and compensation device and method for direct sequence spread spectrum communications systems has an identification (ID) sequence in an acquisition frame which is received by a receiving station and an ID sequence stored in an ID register. A received acquisition frame is demodulated using dot product and cross product demodulation. An ID detector detects the ID sequence in the demodulated dot product, cross product, or inverse cross product acquisition frame. When the ID is detected by the dot product demodulator, the receive frame timing is adjusted to coincide with a time interval when the ID was detected. Also, when the ID sequence stored in the ID register matches either the dot product, cross product or inverted cross product of the received ID sequence, the system microcontroller updates the automatic frequency control value.

Abstract: A direct sequence spread spectrum communication system in a digital cordless telephone having a basestation and a handset that each implement an extended .linevert split.EE.linevert split.+.linevert split.E.linevert split.-.linevert split.L.linevert split.-.linevert split.LL.linevert split. time tracking system and peak matched filter demodulation within a related window to permit one sample per chip analog-to-digital conversion and demodulation for longer code sequences (providing savings in hardware and complexity) and to permit enhanced two sample per chip analog-to-digital conversion and demodulation for shorter code sequences (providing more robust fading immunity).

Abstract: A cordless telephone system connectable to the public switched telephone network having a base station and one or more handsets communicating with the base station by an RF link utility time division duplex direct sequence spread spectrum modulation technique, having a digital variable rate automatic gain control loop. The gain is varied by changing the scale factor for the discriminator output. A high gain scale factor is used during signal acquisition. When the signal has been acquired, a low scale factor is utilized during signal tracking. The controller in the base station and in the handset causes gain use of the different scale factor at the appropriate time.

Abstract: A method for testing a communication link between first and second components of a system, which components communicate via a selected one of a plurality of broadcast channels, the second component being powered by a self-contained power source, the method comprising: causing the first component to scan a plurality of the broadcast channels in sequence in a receiving mode during a scanning period and to broadcast a test signal over the selected channel during the scan; and maintaining the second component in an inactive state in which energy consumption is minimized and in which the second component is unresponsive to broadcast signals during a major part of the scanning period, placing the second component in an active state in which the second component can detect the test signal during a time when the test signal is being broadcast, and causing the second component to broadcast a response signal upon detection of the test signal.

Abstract: A frequency error calibration, estimation and compensation device and method for direct sequence spread spectrum systems, such as digital cordless telephones having a handset and a base station. Initial frequency calibration occurs when the handset is physically coupled to the base station. The allowable frequency error range is divided into a plurality of frequency bins. Both the handset and base station transmit and receive messages using a predetermined frequency offset bin as an estimate of the frequency error. A signal quality value is determined and then a next bin is selected and a next signal quality value is determined. Once a signal quality value has been determined for each frequency bin, a communications link is established between the handset and the base station to allow automatic frequency control tracking to fine tune the frequency offset value. If the signal quality is not above a threshold value, the procedure is repeated.