Patent ID: 8306499
Filing Date: 2012-11-06
Classification: H03H,H04H,H04N

Abstract:
1. A high-frequency filter whose passband is a predetermined frequency band for digital television broadcast, and whose stopband is a mobile telephone terminal transmission band which is near to the passband, the high-frequency filter comprising: a notch filter including: a first characteristic having predetermined pass loss in the passband, and having a predetermined attenuation amount in the stopband; and a second characteristic having a passband which is included in the predetermined frequency band and is narrower than the predetermined frequency band, and having, in the stopband, an attenuation amount larger than the predetermined attenuation amount; a low-pass filter including: a first characteristic which has an attenuation pole set to be near to the stopband, and thereby has an attenuation amount larger than the predetermined attenuation amount; and a second characteristic which has an attenuation pole set to be distant from the stopband, and thereby has, in the passband which is the predetermined frequency band, pass loss smaller than the predetermined pass loss; and a control section which, if a channel selected by a user is a low-band channel that is within the passband and on a lower-frequency side of a threshold frequency in the passband, operates the notch filter and the low-pass filter by combining the first characteristic of the notch filter and the first characteristic of the low-pass filter, and if the channel selected by the user is a high-band channel that is within the passband and on a higher-frequency side of the threshold frequency, operates the notch filter and the low-pass filter by combining the second characteristic of the notch filter and the second characteristic of the low-pass filter.