| 摘要 |
PURPOSE:To suppress leakage to an RF signal input terminal of a local oscillation frequency (2nd local oscillation signal) near the pass band of a band pass filter especially by arranging a specific notch filter preventing the leakage of a local oscillation signal in parallel between both sides of a main line between a microwave signal (RF signal) input terminal and a frequency converting section. CONSTITUTION:An RF signal inputted from a terminal 1 propagates through a main line 5 and is impressed to a frequency converting section 6. The 1st local oscillation signal is inputted to a terminal 2 and the 2nd local oscillation signal is inputted to a terminal 3. An intermediate frequency signal is outputted to a terminal 4. Notch filters 7, 8 are arranged in parallel at both sides while clipping the main line 5. The frequency being 1/5 of the 2nd local oscillation frequency to be attenuated is selected to the notch filters so as to form notch filters utilizing the harmonic mode. That is, the notch filter 7 is formed as a high impedance line whose tip end is open with 1/4 wavelength of the frequency being 1/5 of the 2nd local oscillation frequency and the notch filter 8 is formed as a high impedance line whose tip end is open with 1/4 wavelength of the frequency being (5/6)X(1/5) of the 2nd local oscillation frequency. |
