Acoustic filter with harmonic rejection

摘要

In order to avoid spurious responses at the third harmonic of the signal frequency, a surface acoustic wave filter employs a multi-strip track coupler in which the spacing d of the elements is an integral multiple I of the acoustic wavelength lambda of the third harmonic. When the condition d=I lambda is satisfied, the coupler blocks transmission of the third harmonic from the input transducer track to the output transducer track. This basic principle can also be used to block other frequencies.