Receiving circuit, and receiving apparatus and transmitting/receiving apparatus using the receiving circuit

A receiving circuit, comprising:

• a variable gain amplifying apparatus for amplifying a received modulated signal;
• a high pass filter for removing low frequency components of said modulated signal which is cascaded to said variable gain amplifying apparatus;
• a switch for fixing the output voltage of said high pass filter to a reference voltage;
• a low pass filter for removing high frequency components of said modulated signal which is cascaded to a cascaded circuit of said variable gain amplifying apparatus and said high pass filter and makes it possible to change the cutoff frequency;
• and
• a gain control apparatus for changing the gain of said variable gain amplifying apparatus in order to change the size of the modulated signal that passes through said variable gain amplifying apparatus, said high pass filter and said low pass filter, wherein
• in response to control for changing the gain of said variable gain amplifying apparatus, said gain control apparatus controls said switch, and thereby, fixes the output of said high pass filter at said reference voltage for a constant period of time, and in addition, controls said low pass filter, and thereby, makes the cutoff frequency of said low pass filter higher than the original cutoff frequency for a constant period of time.