Frequency converter

A frequency converter comprising:

• a multiplying circuit configured to multiply an RF (Radio Frequency) signal and an LO (Local Oscillation) signal and output a difference frequency signal having a difference frequency between those of the RF and LO signals, said difference frequency signal comprising differential signal components outputted from first and second output terminals, respectively;
• a load circuit connected to said first and second output terminals of the multiplying circuit;
• an output buffer circuit having first and second input terminals connected to said first and second output terminals of the multiplying circuit, respectively, and an output terminal for outputting a signal into a next stage;
• and
• a notch circuit connected to said first and second input terminals of the output buffer circuit and configured to have an impedance characteristic in which impedance is abruptly reduced to provide a valley point at an undesired signal frequency, in order to remove a component with said undesired signal frequency from said difference frequency signal, said notch circuit comprising first and second LC series resonance circuits connected to said first and second output terminals of the multiplying circuit, respectively, and having a resonance frequency in agreement with said undesired signal frequency.