Abstract: An apparatus comprising a quadrature network, an RF combining circuit and a weighting network. The quadrature network may be configured to generate a first and a second signal in response to an input signal. The RF combining circuit may be configured to generate an output signal comprising the input signal variably phase shifted from a selectable fixed phase starting point in response to the first signal, the second signal and one or more weighting signals. The weighting network may be configured to generate the weighting signals in response to a voltage control signal and one of four possible output selections. The voltage control signal may be configured to control the variable phase shift.

Abstract: A device and method used to transmit/receive an input message bearing signal at variable bandwidths using a variable frequency bandwidth control signal as an input for changing the bandwidth of the output signal.

Abstract: Sine and cosine weighting functions are applied to phase quadrature versions of an input signal to be phase shifted, and the weighted results are summed to provide a phase shifted output signal with an amplitude which is relatively independent of the phase shift. A weighting circuit comprises two translinear sine shaping circuits having differential current outputs providing weighting signals from input currents supplied thereto, the input currents of the two sine shaping circuits being offset relative to one another so that the differential current outputs of the two sine shaping circuits are provided in accordance with a sine function and a cosine function, respectively, of a control signal.

Abstract: A frequency converters used in communications receivers. Such frequency converters can be used for converting a signal from a Radio Frequency (RF) to a low frequency suitable for processing such as demodulation. The inventors have made the unexpected discovery that when the gates of the MESFETs of a double-balanced mixer are left open-circuited and allowed to self-bias, the drop in mixer linearity at high LO power levels is reduced thereby increasing the LO power range of operation. This invention can be used as an improved scale-down mixer as well as an upconverter mixer.

Abstract: A linear gain controlled amplifier comprising a differential transistor pair having an input and an output. The input is connected to a current supply which includes both AC and DC components. A voltage is derived which is proportional to the DC current component and this is compared with a control signal to produce an error signal which is supplied to the gain control terminals of the differential transistor pair. Traditionally, gain control has been implemented using a closed loop consisting of a power detector, a loop filter and a gain control element. The output of the power detector is compared with a reference voltage in a comparator, the output of which is filtered by the loop filter and applied to a control input of the gain control element. Most power detectors are either inaccurate or expensive and elaborate and may exhibit a control error of several decibels.

Abstract: A tree mixer includes a first differential pair of transistors which divide current from a first current source between the transistors in dependence upon a first differential input signal supplied to first input terminals. Two second differential pairs of transistors have controlled paths which conduct current, divided between the transistors of the differential pair in dependence upon a second differential input signal supplied to second input terminals, dependent upon current passed by a respective transistor of the first pair of transistors, to produce a product signal at output terminals. One or more second current sources provide for the total current passed by the first pair of transistors to be greater than the total current passed by the two second pairs of transistors, for improved linearity without increasing noise. A quadrature phase modulator can include two such mixers with common output circuitry.

Abstract: A double mode surface wave resonator comprises two IDTs (inter-digital transducers), arranged side by side between reflection gratings, on a surface of a piezoelectric substrate to provide for coupling of surface waves therebetween, each IDT having interleaved electrodes extending from a common rail between the two IDTs and from a respective outer rail of the IDT. One or each of the IDTs and its outer rail is divided into two halves for providing a differential signal connection to the resonator. The electrodes of the IDTs can be arranged in spatial synchronism with adjacent fingers of the reflection gratings to reduce spurious longitudinal modes.