Abstract: Embodiments provide a charge pump circuit which produces a bias voltage that is applied to a transient suppression device used to clamp both positive and negative transients on signal lines. The bias voltage can be set to a level that is above the sum of a DC voltage differential between positive and negative signal lines and the maximum signal voltage.

Abstract: Embodiments provide a charge pump circuit which produces a bias voltage that is applied to a transient suppression device used to clamp both positive and negative transients on signal lines. The bias voltage can be set to a level that is above the sum of a DC voltage differential between positive and negative signal lines and the maximum signal voltage.

Abstract: Embodiments provide a charge pump circuit which produces a bias voltage that is applied to a transient suppression device used to clamp both positive and negative transients on signal lines. The bias voltage can be set to a level that is above the sum of a DC voltage differential between positive and negative signal lines and the maximum signal voltage.

Abstract: A system and method for conveying supervisory signaling and power over the same twisted wire pairs in a cable as are used to carry data communications in accordance with a predetermined communications protocol. Supervisory signals having first and second differential components are generated. The first component is coupled to both wires of one of the twisted wire pairs as a common mode signal and the second component of the supervisory signal is coupled to both wires of another twisted pair as a common mode signal. The first and second components are recovered at the remote end of the cable. Physical interfaces are AC coupled to the respective twisted pairs at both ends of the cable and positive and negative voltage rails powered by a power sourcing device are coupled to predetermined twisted pairs to convey a DC voltage over the cable which may be used to power a remote electronic device.

Abstract: A wireless broadband communications system that can maintain high data rates while taking into account channel interference resulting from operating in shared frequency bands, signal fading resulting from dynamic channel degradation, and signal distortion resulting from compliance with maximum power output regulations. In one mode of operation, the system performs adaptive modulation by transmitting a first signal over a selected channel using a first modulation mode having a level of distortion associated therewith resulting from operating the system at a predetermined maximum power output level. Next, a SINAD level is measured on the first channel. The level of distortion associated with the first modulation mode is then subtracted from the measured SINAD level to obtain a first noise level.

Abstract: A wireless broadband communications system that can transmit signals over communications links with multiple modes of diversity, thereby allowing signals having very low correlation to propagate over the link along multiple orthogonal paths. The system can be implemented as a non-line-of-sight (NLOS) system or a line-of-sight (LOS) system. The NLOS system employs orthogonal frequency division modulation (OFDM) waveforms to reduce multi-path interference and frequency selective fading, adaptive modulation to assure high data rates in the presence of channel variability, and spectrum management to achieve increased data throughput and link availability. The LOS system employs space-time coding and spatial and polarization diversity to minimize ground bounce nulls. The system achieves levels of link availability, data throughput, and system performance that have heretofore been unattainable in wireless broadband communications systems.

Abstract: A wireless broadband communications system that increases data throughput and link availability through more efficient use of the electromagnetic spectrum allocated to the system. In one mode of operation, the system periodically measures a noise or interference level associated with each one of a plurality of communications channels, and generates a histogram of the measurements associated with each channel. Next, the system determines a noise/interference level estimate for each channel as a predetermined percentile of the histogram associated with the respective channel. The system then selects a respective one of the channels having the lowest noise/interference level estimate for subsequent signal transmission.

Abstract: Techniques for facilitating and reducing the costs associated with the installation of a wireless broadband communications system. In one mode of operation, the system employs a first transceiver to identify n channels having the n lowest levels of noise and interference associated therewith by a spectrum management technique. Next, the first transceiver transmits a predetermined code over the n channels to a second transceiver, which attempts to identify the predetermined code within a captured transmission. In the event the code is correctly identified, the second transceiver measures a noise and/or interference level associated with the corresponding channels. The channel having the lowest measured noise and interference level is then selected for use in system installation.

Abstract: A reduced data rate communication system, such as for example a fixed wireless access system, comprises a plurality of user stations each capable of communicating with a common base station. The user stations can make voice or data calls. The data rate available during a data call is controlled in accordance with the bandwidth or channel capacity whilst still allowing access to the required number of users. The data rate may be reduced prior to or during the data call.

Abstract: A fractional-N frequency synthesizer having a programmable divider and a control circuit therefor, wherein said control circuit incorporates a digital delta-sigma modulator operating as an interpolator.

Abstract: An interferometer type DF system uses an array of five antennas (A,B,C,D,E) arranged at the apices of a regular pentagon to define five wide apertures along the sides of the pentagon and a further five apertures along the diagonals. The phases of the signals received by each antenna, are measured modulo 2.pi. and processed to give a unique bearing of the radio source to the accuracy of the widest aperture defined by the array. One method of processing the phases is to calculate from them the Fourier coefficients of the Fourier series representing the spatial phase distribution. By comparing the difference between each calculated coefficient and a corresponding order coefficient of a set of imaginary antenna phases expressed as integral multiples of 2.pi., the complete 2.pi. phase differences between the measured phases modulo 2.pi. can be found.

Abstract: The invention relates to phase locked loops in which a variable-frequency voltage-controlled oscillator (VCO) feeds a phase comparator via an adjustable divider having a division factor N. The comparator compares the phases of the divided frequency (Fd) and a reference frequency (Fr), and adjusts the VCO to produce phase equality. To enable the VCO frequency (FO) to be adjusted in smaller steps than Fr and yet maintain a loop bandwidth greater than the step size with good spurious performance (thus providing a "fractional N synthesizer"), Fo is made slightly more than N.Fr. The phase detector thus produces a phase error signal. At periodic instants, determined by the period of the frequency difference between Fo and N.Fr, a control unit temporarily increases N by unity so as to bring Fd and Fr into phase.