Title:
AUTOMATIC FREQUENCY CONTROL CIRCUIT FOR FILTER CIRCUIT
Document Type and Number:
Japanese Patent JP3140191
Kind Code:
B2
Abstract:
PURPOSE: To enable small-scale and high-accuracy control by comparing the phases of input and output signals from one filter and impressing the output to plural filters so as to respectively control the frequency characteristics of the plural filters.
CONSTITUTION: The input and output signals of a first LPF 8A in a second filter circuit 8 are respectively impressed through amplifiers 31 and 32 to a phase comparator 33. With the comparison output (error signal) of this comparator 33, the cut-off frequency of a filter circuit 8A is controlled, and the frequencies of other filters 7A-7E and 8A-8E are automatically controlled. The filter 8A is constituted so as to have phase difference of almost 90° between input and output terminals, and the cut-off frequency is set a little higher than 1.7MHz. A temperature compensating circuit 37 cancels fluctuation caused by the temperature characteristics of the respective filters 7A-7E and 8A-8E. Since the respective filters 7A-7E and 8A-8E are set at the almost equal frequency, the control signal for input and output signals of one of those filters can be used for properly controlling the other filter as well.
Inventors:
Ryosuke Inagaki
Application Number:
JP22684892A
Publication Date:
March 05, 2001
Filing Date:
August 26, 1992
Export Citation:
Assignee:
ROHM Co., Ltd.
International Classes:
G11B20/02; G11B20/00; H03H11/04; H03H11/12; H04N9/87; (IPC1-7): H03H11/04; G11B20/02
Domestic Patent References:
| JP1264009A | ||||
| JP522076A |
Other References:
【文献】米国特許5072298(US,A)
Attorney, Agent or Firm:
Shizuo Sano