Mainly divided into two categories: BAWSMR- solid mounted resonator and FBAR- thin film bulk acoustic resonator. Excellent performance, supporting high frequency, but complex process and high cost. BAW filter can be used to form RF front-end module, which can be used in various scenarios of wireless communication.
A filter is a filter circuit composed of capacitors, inductors and resistors. The filter can effectively filter out the frequency point of a specific frequency in the power line or frequencies other than the frequency point to obtain a power signal of a specific frequency, or remove the power signal of a specific frequency.
Main parameters of the filter:
Center frequency: the frequency f0 of the filter passband, which is generally taken as f0=(f 1+f2)/2, and f 1 and f2 are 1dB or 3dB of the bandpass or bandstop filter. Narrow-band filters usually take the minimum insertion loss as the center frequency to calculate the passband bandwidth.
Cut-off frequency: refers to the right frequency point of low-pass filter passband and the left frequency point of high-pass filter passband. It is usually defined by the relative loss point 1dB or 3dB. The reference standard of relative loss is: low-pass is insertion loss based on DC, and Qualcomm is insertion loss based on sufficient Qualcomm frequency band without parasitic stopband.
Passband bandwidth: refers to the spectrum width to pass, BW=(f2-f 1). F 1 and f2 are based on the insertion loss at the center frequency f0. Insertion loss: attenuation caused by introducing a filter into an original signal in a circuit, characterized by loss at the center or cutoff frequency. If full-band interpolation loss is needed, it should be emphasized.