| 摘要 |
PURPOSE:To improve the frequency characteristic and to make the conversion loss constant with respect to an intermediate frequency signal (IF signal) by inserting a distributed coupled type DC block having a length of nearly 1/4 wavelength of a local oscillation signal on the way of a microstrip line in a way the distance from a diode to the open end of the said block is not selected to be a specific value. CONSTITUTION:The distributed coupling type DC block 12 having a length of nearly 1/4 wavelength of a local oscillation signal is inserted on the way of a local oscillation signal input line 111 of an up-converter. Part of the IF signal inputted from an IF signal input terminal 3 is leaked toward a terminal 701 of a 3dB directional coupler, but the IF signal is almost totally reflected by the DC block 12 and not almost leaked toward a local signal input terminal 1. The distance from the diode to the distributed type DC block open terminal is selected to avoid the value to be an integral number of multiple of a half wavelength of the local oscillation signal so as to prevent the circuit to be resonated to the IF signal. Thus, a constant conversion loss is provided to the IF signal and an excellent frequency characteristic is given in the band of the IF signal.
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