Oscillation timing and frequency selective absorption element 2

Ask 1. what is a surface wave filter?
Surface acoustic wave filter (SAWF) is an integrated filter. Its characteristics are small volume, light weight, simple manufacturing process, high center frequency, wide relative bandwidth, and rectangular coefficient close to 1., the working frequency can not be too low, and the general working frequency is between several MHz~ 1GHz.
Figure 15-1 shows the schematic diagram of the saw filter, which is made of piezoelectric material. The signal wave is connected to the transmission transducer. By the anti piezoelectric effect, the electrical signal is transformed into mechanical vibration. The mechanical vibration is propagated along the surface of the substrate. When the receiver is transferred to the receiving transducer, the receiver is transformed into an electrical signal and then sent to the load. Obviously, the fork of the interdigital transducer is different, and the ability to transmit and attenuate different frequency signals will be different.

Q2. How to detect and maintain SAW filters?
When the sound surface is damaged, it can not be repaired. In case of emergency repair, a 0.01 F capacitor test can be connected to the output and the output terminal, as shown in Figure 15-3. The selectivity of SAWF can reach 35 ~ 40 dB, 10 ~ 50 dB higher than LC, and the group delay characteristic is good, and the SAWF is approximately a constant in the pass-band.

Q3. What is a ceramic filter?
Ceramic filter is the general term of frequency selection network composed of ceramic vibrators. In the circuit, it can play the role of filter notch filter and frequency discriminator, replacing the traditional LC circuit with low noise level and high signal-to-noise ratio, the advantages of small size without adjustment, stable work, and cheap price, the disadvantage is that the frequency can not be adjusted.

Q4. How is the ceramic filter classified? The ceramic filter converts the Telecom number into mechanical vibration by using the piezoelectric effect of the ceramic material, and then the mechanical vibration is converted into the Telecom number at the output end. Because the mechanical vibration is very sensitive to the frequency response, the Q value of the quality factor is very high, and the amplitude-frequency and phase-frequency characteristics are very ideal. The ceramic filter has two ends and three ends.

This article is from ALLICDATA ELECTRONICS　LIMITED.