High-frequency signal transmission apparatus and electronic tuner using the same

An electronic tuner comprising:

• an input terminal receiving a high-frequency (HF) signal;
• a local oscillator;
• a mixer receiving the HF signal fed into said input terminal and output of said local oscillator;
• a matching circuit connected to an output of said mixer;
• a band-pass filter connected to an output of said matching circuit;
• an intermediate-frequency (IF) amplifier connected to an output of said band-pass filter;
• and
• an output terminal receiving output of said IF amplifier;
• wherein at least said mixer, said matching circuit, said band-pass filter, and said IF amplifier are composed of balanced circuits and connected by a balanced line;
• wherein said mixer has a high output impedance;
• and
• wherein, for said matching circuit, an impedance of said matching circuit on a side of said band-pass filter is equal to an impedance of said band-pass filter on a side of said matching circuit.

An electronic tuner comprising:

• an input terminal receiving a high-frequency (HF) signal;
• a first local oscillator;
• a first mixer receiving the HF signal fed into said input terminal and output of said first local oscillator;
• a first matching circuit connected to an output of said first mixer;
• a first band-pass filter connected to an output of said first matching circuit;
• a first intermediate-frequency (IF) amplifier connected to an output of said first band-pass filter;
• a second local oscillator;
• a second mixer connected to an output of said first IF amplifier and an output of said second local oscillator;
• a second matching circuit connected to an output of said second mixer;
• a second band-pass filter connected to an output of said second matching circuit;
• a second intermediate-frequency (IF) amplifier connected to an output of said second band-pass filter;
• and
• an output terminal connected to an output of said second IF amplifier;
• wherein at least said first mixer, said first matching circuit, said first band-pass filter, and said first IF amplifier are composed of balanced circuits and connected by a balanced line;
• wherein said first mixer has a high output impedance;
• and
• wherein, for said first matching circuit, an impedance of said first matching circuit on a side of said first band-pass filter is equal to an impedance of said first band-pass filter at a side of said first matching circuit.