Tuner

摘要

A center frequency F0 of an IF filter is effectively adjusted. The IF filter filters a down-converted signal centering around the center frequency F0. A pseudo sine wave generation circuit generates a pseudo sine wave having a level change of at least two steps respectively on both positive and negative sides. The pseudo sine wave is made to pass through the IF filter by a switch circuit, and in the state, an F0 adjustment circuit adjusts the center frequency F0 in the IF filter 14 by comparing a phase of the pseudo sine wave with a phase of a signal after passing through the IF filter.

主权项

1. A tuner which down-converts an RF signal to an IF signal and performs signal processing, comprising:
an IF filter which filters a down-converted signal centering around a center frequency F0 to take out the IF signal; a pseudo sine wave generation circuit which generates a pseudo sine wave having a level change of at least two steps respectively on both positive and negative sides; a switch circuit which supplies the pseudo sine wave to the IF filter instead of the RF signal; and an F0 adjustment circuit which adjusts the center frequency F0 of the IF filter,wherein
the pseudo sine wave is made to pass through the IF filter by the switch circuit, and in this state, the F0 adjustment circuit compares a phase of the pseudo sine wave with a phase of the signal after passing through the IF filter and adjusts the center frequency F0 in the IF filter according to an obtained comparison result.