Abstract: A feedforward linearizer includes a signal cancellation circuit and an error cancellation circuit. The signal cancellation circuit includes a tap delay line, that delay the input signal by a predetermined time delay so as to provide several delayed versions of the input signal. Each delayed version of the input signal is weighted by a tap coefficient. The weighted signals are then added together and fed to the power amplifier. The tap coefficients are derived such that the signals traveling through the upper and lower branch of the signal cancellation loop are aligned and that the output signal of the power amplifier is equalized.

Abstract: A feedforward linearizer for amplifying an input signal comprises a signal cancellation circuit which has a first branch and a second branch. A first amplifier provided in the first branch receives the input signal intended to be amplified and generates an output signal received by a signal cancellation vector modulator. A signal cancellation adder receives the signal generated by the signal cancellation vector modulator and the input signal via the second branch and provides an error signal. The feedforward linearizer also comprises an error cancellation circuit that has a first branch and a second branch. An error cancellation adder in the first branch receives the output signal provided by the first amplifier and generates the output signal of the linearizer. An error cancellation vector modulator in the second branch receives an error signal provided by the signal cancellation adder and provides an error adjusted signal to a second auxiliary amplifier.

Abstract: A cellular communication signal receiver receives a desired signal in the presence of at least one co-channel interference signal. The receiver comprises a channel estimator configured to receive a plurality of training signal samples to estimate the finite impulse response to the desired signal and the co-channel interference signal. The finite impulse response estimates having a predetermined number of channel taps defining the length of the desired channel and the length of co-channel interference channel. A Viterbi decoder is coupled to the channel estimator, and configured to receive the desired and co-channel interference signals. The channel estimator generates channel tap estimates. A power calculator is coupled to the channel estimator and configured to estimate the power of the estimated channel taps.

Abstract: In accordance with the present invention, an optical fiber communications system is provided with an adaptive data equalizer to correct for linear disortion of signals transmitted over optical fibers. A feedback signal from a receiver is used to custom tailor the spectral profile of a launched pulse to thereby minimize the distortion of a received pulse. The system uses optical taps for feedback control in order to adapt to changing conditions in the fiber path.

Abstract: A low noise transistor IC or module comprises a plurality of conventional CMOS transistors which are laid out in parallel in such a way that the effective gate width of the combination of transistors is increased, yet the effective gate resistance and hence the noise figure (NF) of the circuit are reduced. A low noise amplifier incorporating such a module is also described.

Abstract: In accordance with one embodiment of the present intention, an adaptive feedback controller is configured to substantially reduce an error control signal defined by the difference between a command signal and the output signal of a controlled device. The adaptive controller comprises a step generator circuit configured to provide a control signal which is employed to vary the input signal received by the controlled device, The control signal is substantially in the shape of a ramp signal having a given slew rate. An adaptive slew rate computation circuit is coupled to the step generator so as to provide a slew rate compensation signal to the step generator to increase the slew rate of the control signal, when the controlled device is responding to a substantially fast varying input signal. The slew rate compensation circuit decreases the slew rate of the control signal, when the controlled device is responding to a slow varying input signal.

Abstract: An indoor wireless communications system using two-way active-antenna repeaters to distribute signals received from external signal sources within an office, and to extend the range of cordless phone units in use there, is disclosed. The repeaters provide menu-selectable phase-shifting, selectable receiver sensitivity and transmitter power, and selectable signal format conversion to provide added privacy and to prevent interference with communication links in use by third parties within the building. Pattern selection is done by empirical adjustment of an antenna pattern suited to the general floor plan of the area served.

Abstract: A dynamic power amplifier advantageously employed in a wireless terminal for transferring and receiving signals from a base terminal includes an input amplifier adapted to receive an input signal having a given power signal level corresponding to the distance of said wireless terminal to the terminal and adapted to provide an amplifier output signal having a given power output signal level. The dynamic amplifier further includes a power sensor configured to receive the power output signal and to generate a power indication signal corresponding to the power output signal, and a converter adapted to receive the power indication signal in order to generate a biasing signal corresponding to the power indication signal. The biasing signal is applied to the input amplifier so that the operating bias point of the power amplifier varies as a function of the power indication signal.

Abstract: A novel method of making articles that comprise a periodic heteroepitaxial semiconductor structure is disclosed. The method pertains to growth of the periodic structure by MBE, CVD or similar growth techniques, and involves periodically changing the substrate temperature. For instance, a periodic multilayer GaAs/AlGaAs is grown by MBE, with the substrate temperature cycled between 600.degree. C. and 700.degree. C. The novel method can produce multilayer structures of uniformly high material quality.

Abstract: A GaAs-based self-aligned laser with emission wavelength in the approximate wavelength regime 0.87-1.1 .mu.m is disclosed. The laser is a strained layer QW laser and is readily manufacturable. Preferred embodiments of the inventive laser do not comprise Al-containing semiconductor alloy. Lasers according to the invention can for instance be used advantageously as 0.98 .mu.m pump sources for Er-doped fiber amplifiers.

Abstract: Disclosed is an advantageous method of making ridge-waveguide lasers. The method is a self-aligned method that does not comprise any critical alignment steps. Thus it is useful for making lasers that have a very narrow ridge waveguide. Such lasers are desirable because they can suppress lateral higher order modes.

Abstract: Improved heterojunction bipolar transistor (HBT) are disclosed. Inventive devices can attain high cut-off frequency (f.sub.T), exemplarily 80 GHz or higher, and high DC current gain (.beta.), exemplarily 25 or higher. The devices exhibit lateral scaling, permitting reduction in emitter stripe width without unacceptable decrease in .beta.. Exemplarily the stripe width is 1 .mu.m or less. The inventive HBTs are hot electron devices, with the hot electrons in the base region being spatially confined such that relatively few electrons reach the surface of the extrinsic base region. The relatively low bulk and surface recombination rate in the base of inventive HBTs is an important aspect of the invention and makes possible devices having relatively high .beta. and low power consumption.

Abstract: Disclosed is an edge-emitting semiconductor laser that has a single waveguiding structure, and that comprises means for reducing the transverse divergence of the far-field pattern of the laser emission. Typically these means comprise reflecting means (preferably transverse distributed Bragg reflectors) disposed parallel to the junction plane of the laser. Lasers according to the invention can have a highly stable single mode output having a substantially symmetrical far field pattern. Disclosed is also an advantageous method of making ridge-waveguide lasers that can, inter alia, be used to make lasers according to the invention. The method is a self-aligned method that does not comprise any critical alignment steps. Thus it is useful for making lasers that have a very narrow ridge waveguide. Such lasers are desirable because they can suppress lateral higher order modes.

Abstract: Disclosed is apparatus that comprises integrated colliding pulse mode-locked means for generating ultrashort optical pulses. The means advantageously are capable of producing transform-limited (or nearly transform-limited) pulses. Several exemplary embodiments are disclosed. Exemplarily the invention is embodied in InP-based integrated means that produced 1.4 ps pulses at a 32.6 GHz repetition rate.