Abstract: A stacked power amplifier is provided in which an input signal is independently coupled to each of a series of amplifying devices in the stack. A transformer is used at the input circuit of each device to create an RF swing across each amplifying device which is substantially equal. This results in an equal distribution of RF and DC voltage among the devices in the stack.

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.

Abstract: A SAW (surface acoustic wave) device tapped delay line comprises a continuous pattern of bifurcated inter-digital fingers having a constant pitch of .lambda./2 and forming a first IDT (inter-digital transducer), a plurality of second IDTs, substantially identical to one another and arranged with a predetermined pitch P for consecutively receiving a SAW propagated from the first IDT with respective propagation delays, and grounded dummy fingers in regions between adjacent IDTs. The first IDT is apodized in accordance with a Hermitian response to provide it with a pass band centered at a first frequency, and .lambda. is the wavelength of a SAW at a second frequency different from the first frequency and within the pass band. P is an integral multiple of .lambda./2, so that there is a constant finger periodicity throughout the SAW device whereby reflections between the second IDTs are avoided.

Abstract: A SAW device tapped delay line includes an apodized input IDT (inter-digital transducer) and a plurality of substantially identical unapodized output IDTs arranged to receive, after delays which successively increase by an amont T, a SAW propagated from the input IDT. Each output IDT is terminated with a low impedance which is constituted by the low input impedance of a buffer amplifier, to minimize acoustic regeneration by the output IDTs. Grounded dummy fingers with the same metallization ratio as the output IDTs are provided between adjacent output IDTs to provide a constant SAW velocity. The delay line is particularly suited to use in an equalizer of a microwave radio transmission system, in which the delay T is the inverse of the symbol rate of the system. Intermediate frequency automatic time domain equalizer (IF ATDE) arrangements using the SAW device tapped delay line are described.

Abstract: A SAW (surface acoustic wave) device includes a substrate having thereon at least one apodized IDT (inter-digital transducer). The axis of the apodization pattern is inclined towards a driven conductive rail of the IDT at the ends of the pattern, whereby the driven end fingers have a low capacitive coupling to a ground plane on which the substrate is supported. The capacitive coupling to the ground plane may also be reduced by supporting the substrate on the ground plane via an insulating support, whereby an air gap or the insulating support decreases the capacitance between the IDT and the ground plane.

Abstract: A SAW device includes aligned IDTs (inter-digital transducers) with a continuous pattern of fingers between their front edges. Each IDT may be symmetrical about its center, and includes front and back edge reflection suppressing regions of fingers of successively decreasing length, which serve to suppress surface acoustic wave reflections at the respective edges. Optional shield regions between the two front edge suppressing regions, and between the back edge suppressing regions and acoustic absorbers, include fingers of successively increasing length complementary to and adjacent the fingers of successively decreasing length of the reflection suppressing regions. The IDTs may be apodized or unapodized, and each IDT may include dummy fingers between its active region and each reflection suppressing region.

Abstract: Each IDT (inter-digital transducer) of a SAW (surface acoustic wave) device is formed on a thin resistive doped silicon film having the same pattern as the IDT, which improves adhesion of the IDT to the substrate. The silicon film also constitutes electroacoustic absorbers between the IDTs and edges of the substrate, and can have a linearly tapered edge adjacent to each IDT to suppress reflections at the absorber boundary. The SAW device is formed by sputtering silicon onto the substrate, subsequently forming the IDTs, and then etching the silicon from areas where it is not wanted.

Abstract: Each IDT (inter-digital transducer) of a SAW (surface acoustic wave) device has a linearly tapered back edge formed by reflection-suppressing fingers of successively decreasing length spaced apart with a pitch of lambda/4 behind the active region of the IDT, where lambda is the wavelength of a SAW to be propagated, whereby SAW reflections at the back edge of the IDT are substantially eliminated. A thin resistive doped silicon film between the back edge of each IDT and the adjacent edge of the substrate absorbs waves propagated via this back edge. The film underlies the IDTs to provide improved adhesion to the substrate.

Abstract: A surface acoustic wave (SAW) device has an input interdigitated transducer (IDT) and an output IDT. One of the transducers is formed as two loops which are interconnected so that unwanted magnetic feedthrough voltages induced in or by such current loops cancel, while currents producing or produced by the SAW add.

Abstract: An equalizer arrangement comprises a fixed-characteristic equalizer which is supplemented by a variable-amplitude notch equalizer to enable proper equalization of signals transmitted via cables of arbitrarily mixed cable gauges. Automatic control of the notch amplitude is provided by detecting a predetermined signal level in the equalized signal, comparing this with its correct value, and controlling an up/down counter accordingly. The count of the counter determines a current flow through a diode which constitutes a variable resistance of the equalizer.

Abstract: To enable increased power coupling into a SAW device for which voltage breakdown is a limiting factor in determining the maximum power which can be coupled, each transducer of the SAW device is replaced by a plurality of series-connected inter-digital transducers (IDTs). For operation in an Nth harmonic mode, there may be N series-connected IDTs which are offset from one another by 1/N wavelengths of the fundamental frequency for which the individual IDTs are designed; for high frequency SAW devices, this further increases the power which can be coupled into the device. The SAW device is particularly useful in a delay-line oscillator to constitute a microwave source for a local oscillator in a radio repeater.