Abstract: An RFID reader is provided. The RFID reader includes a transmitter section and a receiver section. The transmitter section is configured to transmit a first RF signal which includes several carrier frequencies that are effective to simultaneously illuminate a tag at the plurality of carrier frequencies. The receiver section is configured to receive a second RF signal which includes several frequencies which each have the same information.

Abstract: An RFID reader is provided. The RFID reader includes a transmitter section and a receiver section. The transmitter section is configured to transmit a first RF signal which includes several carrier frequencies that are effective to simultaneously illuminate a tag at the plurality of carrier frequencies. The receiver section is configured to receive a second RF signal which includes several frequencies which each have the same information.

Abstract: An apparatus having a transmitter portion and a receiver portion each isolated from each other and comprising a plurality of antennae, each antenna being selectively connectable to both the receiver portion and transmitter portion, said antennae thus being common to both transmitter and receiver. It may be adapted such that one antenna is selectable to be used as a transmitter whilst at the same time an alternative antenna is selectable to be used as a receiving antenna.

Abstract: A linear power amplifier filters an instantaneous input signal to generate a filtered input signal, combines the instantaneous input signal and filtered input signal to generate a modified drain source voltage waveform and modulates a switched mode power supply to the linear power amplifier in accordance with the modified waveform.

Abstract: An RFID reader comprises a receiver section for receiving an RF signal and a transmitter section for transmitting an RF signal. The reader is a multicarrier RFID reader and both the transmitted RF signal and the received RF signal comprise at least two frequencies.

Abstract: A linear power amplifier filters an instantaneous input signal to generate a filtered input signal, combines the instantaneous input signal and filtered input signal to generate a modified drain source voltage waveform and modulates a switched mode power supply to the linear power amplifier in accordance with the modified waveform.

Abstract: An amplifier pre-distorter method and apparatus squares an input signal and splits the signal into inphase and quadrature parts which are processed to generate a polynominal predistortion signal. This simplifies the apparatus and enables implementation in an application specific integrated circuit.

Abstract: A power amplifier system (1) comprises a control circuit; a power amplifier (3) and a delay device (8). The control circuit comprises a detector (4) for detecting an instantaneous power level of an input signal; a threshold comparator (5); and a power supply voltage source (6). The threshold comparator is provided with a plurality of preset thresholds (TH1, TH2, TH3); wherein the threshold comparator compares the detected power level with the preset thresholds; wherein the power supply voltage (V1, V2, V3 and V4) is switched according to the output of the threshold comparator; and wherein the delay device (8) delays the input signal to the power amplifier to enable the power supply voltage to be adapted to the detected power level, such that the efficiency of the power amplifier (3) is optimised.

Abstract: There is provided an apparatus for compensating for envelope frequency and/or carrier wave frequency dependence in third order intermodulation (IM3) products. Frequency dependence compensation reduces peak error power and thereby increases the efficiency of error amplifiers, such as those used in base stations used in telecommunications. In order to compensate for non-linear distortion, the apparatus is configured with a delay or “memory” unit, T1. The apparatus may be implemented as a single RF-ASIC or in a cascade of more than one such ASICs. The apparatus may also be incorporated within a feed forward amplifier arrangement.

Abstract: An amplifier pre-distorter method and apparatus squares and input signal and splits the signal into inphase and quadrature parts which are processed to generate a polynomial predistortion signal. This simplifies the apparatus and enables implementation in an application specific integrated circuit.

Abstract: A direct conversion receiver which compensates for interfering signals introduced during processing. Direct conversion is achieved using direct detection techniques which introduce interfering signals which become inseparable from the wanted signal. A pilot signal (202) is added to an input RF signal (200) prior to passing the summed signal (206) to four separate paths (210, 212, 214, 216). Signal (206) is modulated so that the phase is different in each path using local oscillator signals and switches (230, 232, 234, 236), and then digitised by ADCs (260, 262, 264, 266). Correction is introduced into respective paths (210, 214) by cancellation loops (310, 314) to compensate for unwanted signals prior to the paths being grouped so that the pairs of digitised signals (272, 300; 276; 304) which are 180° out of phase with one another are subtracted to provide output inphase and quadrature signals (220, 224).

Abstract: A radio communications transceiver which operates to transmit radio signals via a transmit antenna and receive radio signals via a receive antenna, wherein said transmit and receive antennas are disposed to provide at least a substantial amount of radio signal isolation therebetween. The radio communications transceiver further includes a cancellation device comprising a first coupler coupled to the transmit antenna and arranged to extract a sample of the transmit signal, a second coupler coupled to the receiver antenna and arranged to extract a sample of the received signal, a correlator fed on first and second inputs with the transmit and the received signal samples respectively, the correlator operating to generate an error signal representative of a correlation of the transmit and received radio signals, which error signal is fed to a modulator which operates to modulate the transmit signal sample, consequent upon the error signal.

Abstract: A choke for reducing common mode signals in high frequency circuits. A microstrip transmission line includes a pair of conductors spaced above a ground plane conductor. In input and output regions the conductors are spaced relatively far apart from each other such that each conductor presents a characteristic impedance that is similar for common mode and for differential mode signals. Between the input and output regions the conductors are located much closes together such that they present different characteristic impedances to common mode and to differential mode signals so as to reflect the common mode signal but not the differential mode signal. In another version a hole in the ground plane beneath the conductors is partially occupied by a conductive island that is coupled to the ground plane through a resistance to absorb the common mode signal rather than reflecting it. Other versions are realized in a pair of parallel coaxial cables and in a coplanar transmission line.