Abstract: An active tunable filter circuit for use as an integratable active filter in a mobile radio apparatus, comprises an active amplifier circuit (A) including a reactive feedback network including a first tunable element (L1) set to pass with amplification a wanted input signal, and a passive resonant circuit (P) coupled to the active amplifier circuit and including an inductive element (LFB, L3 or L4) and an inactive semiconductor element (FET2, FET3 or FET4) having an interelectrode capacitance which in operation resonates with the inductive element at a harmonic of the wanted signal. In one configuration (FIG. 1) the circuit comprises a band pass filter with amplification and in another configuration (FIG. 6-not shown) the circuit comprises a harmonic notch filter with amplification.

Abstract: A communication system economically mitigates the frequency-selective multipath effects and co-channel interference in wireless LANS. The communication system comprising a wireless local area network (LAN) formed by a plurality of spacially separated transceivers (TR, TR?). Each of the transceivers has a transmitting section (10) for transmitting data by a combination of dual code spread spectrum techniques and a receiving section (12) for recovering the data. The receiving section (12) comprises a plurality of diversity antennas (ANT 1 to ANT n), an adaptive forward equal gain combiner (60) having a plurality of branches (62 to 74 and 62? to 74?), each branch being coupled to a respective one of the diversity antennas. The adaptive forward equal gain combiner (60) selects a signal in one of the branches as a reference signal and co-phases the signals in the remaining branches with the reference signal.

Abstract: An active tunable filter circuit for use as an integratable active filter in a mobile radio apparatus, comprises an active amplifier circuit (A) including a reactive feedback network including a first tunable element (L1) set to pass with amplification a wanted input signal, and a passive resonant circuit (P) coupled to the active amplifier circuit and including an inductive element (LFB, L3 or L4) and an inactive semiconductor element (FET2, FET3 or FET4) having an interelectrode capacitance which in operation resonates with the inductive element at a harmonic of the wanted signal. In one configuration (FIG. 1) the circuit comprises a band pass filter with amplification and in another configuration (FIG. 6-not shown) the circuit comprises a harmonic notch filter with amplification.

Abstract: A radio frequency power amplifier (16) for use in at least 2 frequency bands, comprises a power amplifier (32) having a passive adjustable input matching network (30), a passive variable output power matching network (34, 36) and a source (48) of tuning voltages for adjusting the input and output networks so that the power amplifier functions as a narrowband amplifier in a predetermined one of the at least 2 frequency bands. The source of tuning voltages may comprise a look-up table.

Abstract: A communication system comprises a wireless local area network (LAN) formed by a plurality of spacially separated transceivers (TR, TR′). Each of the transceivers has a transmitting section (10) for transmitting data by a combination of dual code spread spectrum techniques with transmit diversity. More particularly an input data stream is split into quadrature related channels (I,Q). Each of the channels comprises a frequency up-converter (42, 44, 46), a spread spectrum stage (50, 52) for spreading the up-converted channel signal by a respective one of two parallel produced PN codes (PN1, PN2) and an antenna (18, 20) for propagating its respective spread spectrum signal, the antennas (18, 20) being located where convenient in the coverage area of the respective transmitting section.

Abstract: A communication system comprises a wireless local area network (LAN) formed by a plurality of spacially separated transceivers (TR, TR′). Each of the transceivers has a transmitting section (10) for transmitting data by a combination of dual code spread spectrum techniques and a receiving section (12) for recovering the data. The receiving comprises a plurality of diversity antennas (ANT 1 to ANTn), an adaptive forward equal gain combiner (60) having a plurality of branches (62 to 74 and 62′ to 74′), each branch being coupled to a respective one of said diversity antennas, an in-phase splitter (92) for splitting an output from the combiner into two output channels, means (94 to 98) for demodulating the signals in the output channels, means (104 to 108) for correlating the signals in each of the output channels with respective ones of the dual spreading codes and means (110) for recovering data from the correlated signals.

Abstract: A short range communications system in which transmitted signals are distorted by multipath effects and non-linear characteristics of circuit elements and cause constellation errors in a received signal. These errors are determined by a receiving transceiver (TR′) which transmits a control signal to a transmitting transceiver (TR). The control signal is applied to a stage (12) to adjust the magnitude of input baseband data prior to modulation in a modulator (14) to predistort the constellation of the modulated signals in such a way that the distortion is effectively eliminated in propagation.