Tuning and control of an acoustic wave filter via a capacitor bank

摘要

In an acoustic wave filter a differential between the target/designed load on the input node or the target/designed load on the output node of a filter module (450) may affect its performance. The tunable filter is configured to reduce effects of impedance mismatches between the input and output loads (VSWR other than expected by filter module nominally). A variable capacitor (98A, 98B, 98C) is employed to modulate acoustic wave resonators (80A, 80B, 80C) to reduce a input signal insertion loss due to an unexpected or non-conforming VSWR (not equal to VSWR the filter model was designed to process). A PROM (448) is configured to include variable capacitor deltas for various VSWR. The control logic module may sense the output load, determine the VSWR differential, and choose the closest set of variable capacitor deltas from the PROM.