Transverse Surface Acoustic Wave Research Articles

Noise and dynamic range optimization of SAW transversal filters

A model for surface acoustic wave (SAW) transversal filters with special attention to the system and circuit designer's point of view is summarized. In the ideal situation the SAW transversal filter is driven with a voltage and the short-circuit current is sensed, which results in a minimization of the triple transit echo distortion. The aperture (width) of the SAW device is the only parameter that is not determined by the frequency dependence of the transfer and therefore it can be used to optimize the SAW device in relation to the electronic circuitry. Noise and dynamic range calculations on an amplifier-filter-amplifier configuration, are performed. It is shown that for a low noise floor at the input of the SAW device, the aperture of this device should be chosen large. However, the dynamic range of the amplifier-filter-amplifier configuration can be maximized by choosing a small aperture.

A 2 GHz surface transverse wave oscillator with low phase noise

A hybrid oscillator at 1.9805 GHz using acoustic surface transverse wave (STW) delay lines operating at the third harmonic as the frequency controlling element is discussed. The STW delay lines were fabricated on 37.5 degrees -rotated Y-cut quartz substrates with a photolithographic technique. A very thin metallization (25 nm) was used to obtain low insertion loss. A split isolated electrode design was used for the transducers. The Q-value and the untuned insertion loss of the STW filter were 3400 and 21 dB, respectively. The phase noise and temperature stability of the oscillator were characterized. At a power output of 6.5 dBm a single-sideband phase noise-to-carrier ratio of -100 dBc/Hz at 1 kHz was attained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Timing Recovery with SAW Transversal Filters in the Regenerators of Undersea Long-Haul Fiber Transmission Systems

Surface-acoustic-wave (SAW) filters have been generally accepted as the best available choice for timing recovery in repeatered transoceanic fiber transmission systems operating in the range of 300 Mbit/s as well as in other digital transmission systems operating from approximately 0.1 to 1 or 2 Gbit/s. The SAW technology is ready and reliable, filter size is consistent with the severe space limitations of undersea repeater housings, and cost is reasonable, especially for the transversal (tapped-delay-line) filter type. This paper updates the relationship between system performance and the characteristics of transversal SAW filters, which have a finite impulse response and non-minimum-phase behavior. New results relate to passband ripple (typical in these filters), thermal characteristics, and the impact of the-delay-line structure on filter ringing time.

Timing recovery with SAW transversal filters in the regenerators of undersea long-haul fiber transmission systems

Surface-acoustic-wave (SAW) filters have been generally accepted as the best available choice for timing recovery in repeatered transoceanic fiber transmission systems operating in the range of 300 Mbit/s as well as in other digital transmission systems operating from approximately 0.1 to 1 or 2 Gbit/s. The SAW technology is ready and reliable, filter size is consistent with the severe space limitations of undersea repeater housings, and cost is reasonable, especially for the transversal (tapped-delay-line) filter type. This paper updates the relationship between system performance and the characteristics of transversal SAW filters, which have a finite impulse response and non-minimum-phase behavior. New results relate to passband ripple (typical in these filters), thermal characteristics, and the impact of the delay-line structure on filter "ringing" time.

Propagation of Transverse Surface Acoustic Waves in Rotated Y-Cut Quartz Substrates Under Heavy Periodic Metal Electrodes

Abstmct-A theory of the propagation of transverse surface acoustic waves on a piezoelectric substrate with heavy periodic metal electrodes on the surface is presented. The mechanical properties of these electrodes are assumed to be nonnegligible. Dispersion relations for waves near the stopband of the periodic electrode array are analyzed. It is found that the mass of the electrodes exerts a considerable effect on the shape and mutual positions of the stopbands for short-circuited and electrically isolated electrodes. The discussion is based on an approximation for the effective surface impedance that relates the amplitudes of the electric and elastic fields observed at the surface of a piezoelectric substrate. The parameters of this approximation are given for rotated Y-cut quartz substrate. The theory presented can readily be generalized to the case of Rayleigh surface waves.

Suppression of bulk modes in SAW transversal filters by gold transducers

Unwanted bulk modes in surface-acoustic-wave (SAW) transversal filters are demonstrated to be dependent on the transducer metallisation. Experimental results are presented that compare Au with the more conventional Al metallisation and show that bulk modes can be suppressed by > 20 dB.

Novel programmable high-speed analog transversal filter

A totally monolithic surface acoustic wave transversal filter has been demonstrated which utilizes an integrated multiplexed FET array to program the desired filter function. The device is based on ZnO on Si SAW technology with the FET array being fabricated using a standard NMOS processing schedule. Experimental results are presented which show the analog correlation of RF modulated waveforms (f o = 100 MHz) with various preprogrammed filter functions.