2. Low-loss" filter configurations

Configurations meeting the "low-loss" requirement are based on three types of techniques:

• single-phase unidirectional transducer (SPUDT) ;

• interdigital interleaved transducer (IIDT) ;

• resonator-based solution.

The SPUDT category has a moderate bandwidth (0.3 to 5%) and an insertion loss of between 5 and 10 dB; they are highly flexible and relatively close to "classic" filters. The IIDT category, on the other hand, has a lower loss, typically less than 5 dB, but with little possibility of out-of-band rejection. Finally, the resonator category offers even lower loss, good out-of-band rejection and very small size.