Abstract: In cellular telephony, a plurality of communication signals which are received at a base station for wireless transmission are multiplexed onto a single physical medium which runs up a mast. This reduces the use of cabling running up the mast with an attendant savings in cost.

Abstract: The use of wideband or software defined radio is attractive in terms of cost reduction since it allows re-use of base stations for different transmission modes. However, wideband radio also introduces the problem of how to deal with high level interfering signals. Presently, such signals saturate parts of the receive circuit—typically the ADC. By detecting interference and determining its frequency, it is possible to tune a bandpass or bandpass with notch filter, to take the interfering signal out of the reception band of the receiver thereby taking the ADC out of saturation whilst retaining the ability to resolve low level signals.

Abstract: Very low passband ripple is provided in a wide bandwidth high frequency SAW FIR filter using slanted finger IDTs by one or more of three techniques: cancelling regenerated SAWs at parallel-connected input IDTs of two SAW filters which are similar except for a quarter-wavelength difference in spacing of the input and output IDTs, this difference varying with wavelength across the IDT aperture; shaping edges of shield electrodes to provide quarter-wavelength differences in, and hence cancellation of, SAWs reflected at the edges, the differences varying with wavelength across the IDT aperture; and making pairs of slanted shield electrodes symmetrical to compensate for refraction of SAWS by the shield electrodes.

Abstract: Very low passband ripple is provided in a wide bandwidth high frequency SAW FIR filter using slanted finger IDTs by one or more of three techniques: cancelling regenerated SAWs at parallel-connected input IDTs of two SAW filters which are similar except for a quarter-wavelength difference in spacing of the input and output IDTs, this difference varying with wavelength across the IDT aperture; shaping edges of shield electrodes to provide quarter-wavelength differences in, and hence cancellation of, SAWs reflected at the edges, the differences varying with wavelength across the IDT aperture; and making pairs of slanted shield electrodes symmetrical to compensate for refraction of SAWs by the shield electrodes.

Abstract: Two oscillators produce respective signals at two different frequencies each dependent upon a parameter such as temperature in accordance with a polynomial with coefficients which are different for the two oscillators. A ratio of the frequencies is inverse to a ratio of a selected one of the coefficients of the polynomials. A mixer produces, at a sum or difference frequency of the two signals, an output signal for which a corresponding coefficient of a respective polynomial is substantially zero. The arrangement can be cascaded to produce zero coefficients for a plurality of terms in the polynomial.

Abstract: Very low passband ripple is provided in a wide bandwidth high frequency SAW FIR filter using slanted finger IDTs by one or more of three techniques: cancelling regenerated SAWs at parallel-connected input IDTs of two SAW filters which are similar except for a quarter-wavelength difference in spacing of the input and output IDTs, this difference varying with wavelength across the IDT aperture; shaping edges of shield electrodes to provide quarter-wavelength differences in, and hence cancellation of, SAWs reflected at the edges, the differences varying with wavelength across the IDT aperture; and making pairs of slanted shield electrodes symmetrical to compensate for refraction of SAWs by the shield electrodes.

Abstract: A low noise amplifier (LNA) in a LNA arrangement is selectively bypassed, without detracting from the performance of the LNA arrangement when it is not bypassed, by selecting components of an input signal which are reflected at the input of the LNA. These reflected signal components can be increased, when the LNA is bypassed, by interrupting a supply voltage to the LNA and/or shunting the input of the LNA to ground. The arrangement can be a balanced LNA arrangement, using two LNAs and two quadrature couplers, or it can be an unbalanced LNA arrangement.

Abstract: Acoustic resonators such as surface acoustic wave (SAW) devices and thin film bulk acoustic resonators (FBAR) can be configured to produce a band reject filter. Such a filter overcomes the insertion loss and power handling limitations of conventional band pass configurations and as such can be used in power amplifier and duplexer applications.

Abstract: Acoustic resonators such as surface acoustic wave (SAW) devices and thin film bulk acoustic resonators (FBAR) can be configured to produce a band reject filter. Such a filter overcomes the insertion loss and power handling limitations of conventional band pass configurations and as such can be used in power amplifier and duplexer applications.

Abstract: A spatial harmonic transducer of a SAW device is made directional for SAWs at a spatial harmonic signal frequency of the transducer by a reflector for reflecting SAWs at that frequency. The transducer comprises repeated groups of consecutive electrodes having a predetermined polarity sequence, positioned to operate coherently for SAWs at the signal frequency. The reflector comprises reflector electrodes for producing constructive and destructive interference in opposite SAW directions, with electrode widths and spacings of at least a quarter wavelength at the signal frequency. A SAW device with two such spatial harmonic SPUDTs using different polarity sequences can provide desirable characteristics for filters and delay lines at frequencies of about 2 GHz.

Abstract: A spatial harmonic transducer of a SAW device is made directional for SAWs at a spatial harmonic signal frequency of the transducer by a reflector for reflecting SAWs at that frequency. The transducer comprises repeated groups of consecutive electrodes having a predetermined polarity sequence, positioned to operate coherently for SAWs at the signal frequency. The reflector comprises reflector electrodes for producing constructive and destructive interference in opposite SAW directions, with electrode widths and spacings of at least a quarter wavelength at the signal frequency. A SAW device with two such spatial harmonic SPUDTs using different polarity sequences can provide desirable characteristics for filters and delay lines at frequencies of about 2 GHz.

Abstract: A filter comprises a shallow bulk acoustic wave (SBAW) longitudinally coupled double mode resonator (LCR) and a reactance coupled between an input and an output of the resonator. Due to its use of a piezoelectric substrate with high electromechanical coupling and an orientation for propagating SBAWs, the resonator has a relatively poor stop band attenuation in a shoulder region on a high frequency side of its pass band. At frequencies in the shoulder region, a signal coupled via the resonator from the input to the output is reduced by a signal of opposite phase coupled via the reactance with a similar attenuation, thereby improving attenuation in the shoulder region. The reactance can be a capacitance formed on the substrate surface.

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: A tuneable E-plane waveguide filter is presented. Tuning is achieved using sliders inserted into the cavities of the insert of the waveguide filter. The sliders are inserted through gaps or notches in the insert, or through notches in the waveguide housing. The positions of the sliders is adjusted to fine-tune the frequency response of the waveguide filter, overcoming limits on narrow relative bandpasses imposed by manufacturing tolerances. When a desired frequency response is achieved, the sliders are fixed in position. Assembly and tuning is less expensive and less complex than tuneable H-plane waveguide filters.

Abstract: A tapered IDT function is provided in an IDT of a SAW device having fingers substantially parallel to one another by applying a static electric field to a piezoelectric substrate of the SAW device to generate in the substrate a strain which varies across the aperture of the IDT, thereby varying a center frequency of the IDT across the aperture of the IDT. The electric field can be perpendicular to the fingers and created by applying a dc voltage between conductors at least one of which can be tapered or angled, either in the region of the IDT to produce a strain directly or adjacent to the IDT to produce a strain indirectly, or it can be parallel to the fingers, two fields with opposite directions being created at the two sides of the IDT.

Abstract: A feed forward power amplifier has a main amplifier and an error compensation path that compares the input and output of the main amplifier and subsequently adjusts the output signal from the main amplifier. Currently, such a design requires the implementation of a delay apparatus to delay the output of the main amplifier in order to compensate for the delay within the error compensation path. This delay apparatus implemented within a high-power area costs the power amplifier in terms of money, size, and/or efficiency. With the implementation of a phase compensation filter within the error compensation path, the delay apparatus can be removed. The phase compensation filter has a frequency versus phase characteristic with a positive slope for a limited bandwidth and a constant frequency versus gain characteristic. This allows, for the limited bandwidth, the characteristic of the error compensation path to be similar to that of the undelayed output of the main amplifier.

Abstract: A SAW device has tapered trasnsducers each of which is divided into two or more tapered transducer parts, which are arranged in line with one another in one or more SAW tracks with the tapers of adjacent tapered transducer parts complementary to one another to provide a compact arrangement. The tapered transducer parts can be symmetrically or asymmetrically tapered to provide different frequency bands for band or bandwidth switching of the SAW device. Input and output impedances of the SAW device can be maintained during such switching by switching of dummy transducer parts also provided on the same piezoelectric substrate.