SAW filter

SAW filter

(Surface Acoustic Wave filter) A semiconductor device that is used to filter out desired frequencies. Widely used in mobile phones to filter both RF and IF frequencies, a SAW filter uses the piezoelectric effect to turn the input signal into vibrations that are turned back into electrical signals in the desired frequency range.

Two sets of metal electrodes like teeth on a comb are adhered to a quartz crystal and spaced apart (in microns) based on the required frequencies. As few as five and as many as 5,000 electrodes are used. An intriguing analogy from Bruce Thomas at Sawtek, a subsidiary of TriQuint Semiconductor, is that the first set of electrodes is like throwing a large log into a pond, which makes huge waves that cause little sticks to bounce out at the other side (second set).

TC-SAW and BAW
SAW filters are sensitive to high temperatures, and temperature-compensated SAW (TC-SAW) filters were designed to retain their integrity under such conditions. However, TC-SAWs do not support the higher LTE frequencies, but bulk acoustic wave (BAW) filters do. As a result, SAW filters are often used for lower frequencies, while BAWs, which are twice as costly, are used for the high end. See RF filter.
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For the June quarter, our guidance reflects near-term impacts of product mix and costs associated with lower utilization at our SAW filter fabs.
In a conventional narrowband receiver as shown in Figure 3, RF signals and interference are bandpass-filtered by an off-chip SAW filter after the receiver antenna.
Both PTA1.5M and PTA1.5x2M can incorporate the antenna element, an optional SAW filter, the cascadable PT1233D LNA, matching and passives components, on a low cost, easy to integrate10x16 mm single sided PCBA with "back side" copper clad ground plane.
Due to oscillators mismatch, thermal drifts, and Doppler, the carrier can be located with an offset of D = [+ or -] 140 kHz from the central IF; therefore, the signal is filtered by a 500 kHz bandwidth SAW filter, much wider than the signal spectrum.
Wi2Wi added that its 0008i module is fully certified for regulatory compliance and includes an integrated TCXO and RTC clock as well as a SAW filter and LNA.
Thus, a simple, non-switchable SAW filter is sufficient.
Other markets were found, most notably audio buzzers (smoke alarms, TTL compatible tone generators), air ultrasonic transducers (television remote controls and intrusion alarms) and SAW filter devices that employ Surface Acoustic Wave effects to achieve high frequency signal filtering.
The highly compact solution integrates the IF SAW filter, external low noise amplifiers (LNA) for three bands, transmit and RF voltage controlled oscillator (VCO) modules and many of the remaining discrete components found in conventional GSM handset designs including loop filters and tank components.
TriQuint transmit modules integrate the functionality of a PAM with a power detector, the coupler, isolator, the duplexer and the transmit SAW filter into a single module occupying only 40mm.
Because it is a single-conversion tuner, it requires only a single SAW filter. Incorporating both RF and IF AGC amplifiers, this device is appropriate for televisions, set-top boxes and USB memory sticks.
In high gain mode, using a typical SAW filter, 25 dB cascaded gain can be achieved with 2.1 dB noise figure.
This SAW filter is designed for use in a global navigation satellite system.