WIDE BAND FREQUENCY CHARACTERISTIC MEASURING CIRCUIT FOR RECEIVING CONVERTER

PURPOSE:To obtain a measuring circuit which enables measurement of wide band frequency characteristic of a down converter for receiving used for satellite communication with one sweeper. CONSTITUTION:A frequency signal which is swept over a wide band from a sweep oscillator 2 is inputted into an LO input terminal of a receiving converter 1 to be measured and an output from an LO output terminal is mixed with an output of a reference oscillator 3 by means of a mixer 4. An output of the mixer 4 is limited in band with a bandpass filter 5 to obtain an output of an arbitrary level with a step attenuator 6. The output is inputted into an RF input terminal while a frequency conversion is accomplished by a local oscillation signal generated based on a signal inputted into the LO input terminal to pick up an IF output thereof at an IF output terminal thereby achieving an observation of the frequency characteristic with a scalar network 7.