Patent ID: 8538364
Filing Date: 2013-09-17
Classification: H03H,H04B

Abstract:
1. A filter circuit capable of allowing settings of a first cutoff frequency and a second cutoff frequency, comprising: a first filter including a first capacitor and a first resistor; a second filter including a second capacitor and a second resistor; a first filter switch circuit for coupling the first filter on a signal path; a second filter switch circuit for coupling the second filter on the signal path; and a charging circuit coupled to the second filter, wherein the charging circuit comprises at least a charging resistor and a charging switch that are coupled in series with one end of the second capacitor of the second filter and in series with the other end of the second capacitor, respectively, wherein, for setting up the first cutoff frequency, the first filter switch circuit is controllably turned on while the second filter switch circuit is controllably turned off for a first time period so that the first filter participates in operation of the filter circuit, wherein, for setting up the second cutoff frequency, the first filter switch circuit is controllably turned off while the second filter switch circuit is controllably turned on for a second time period subsequent to the first time period so that the second filter participates in operation of the filter circuit, and wherein the charging switch of the charging circuit is controllably turned on for the first time period so that the second capacitor of the second filter can be charged via the charging resistor of the charging circuit.