The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 09, 1996
Filed:
Nov. 18, 1994
Akira Takayama, Soma, JP;
Alps Electric Co., Ltd., Tokyo, JP;
Abstract
The invention provides a filter circuit for use in a double-conversion TV tuner exhibiting low diode insertion loss, in which intermodulation distortion does not occur even when an incoming signal has a large amplitude. In the filter circuit according to one preferred embodiment of the invention, there are provided three bandpass filters (BPFs) which allow corresponding RF signals in different frequency bands to pass through them, and six variable attenuation diodes whose impedance is controlled by an AGC voltage applied to an AGC terminal (16). There are also provided switching diodes (20) disposed between an input terminal (1) and the inputs of three BPFs so that the switching diodes (20) select exclusively one of three BPFs so as to apply an RF signal received at the input terminal (1) only to the selected BPF (it will be assumed hereinbelow that the BPF (21) is selected). In this arrangement, not only the impedance of variable attenuation diodes (22, 23) in the selected BPF (21) which provides the extracted RF signal, but the impedance associated with all variable attenuation diodes is controlled by the AGC voltage.