Standing wave ratio detecting apparatus

A standing wave ratio detecting apparatus provided with detector means for detecting a traveling wave and a reflected wave to obtain a traveling wave detection voltage V.sub.F and a reflected wave detection voltage V.sub.R and with a standing wave ratio indication meter, comprising:

• an integration circuit connected to the output side of a traveling wave detector in said detector means and made up of a resistor and a capacitor for integrating said traveling wave detection voltage V.sub.F to obtain an integrated voltage V'.sub.F ;
• an operational amplifier, connected to a junction point of said resistor and said capacitor making up said integration circuit and to the output side of a reflected wave detector in said detector means, for comparing said average voltage V'.sub.F from said integration circuit with said reflected wave detection voltage V.sub.R from said detector means to deliver said output voltage E.sub.o at a high level when said average voltate V'.sub.F is greater than said reflected wave detection voltage V.sub.R and to deliver said output voltage E.sub.o at a low level when V'.sub.F is smaller than V.sub.R ;
• a switching element connected to the output side of said operational amplifier and to a junction point of said resistor in said integration circuit and the output side of said traveling wave detector, said switching element being kept in a high-impedance state when said output voltage E.sub.o of said operational amplifier is at a low level to expedite the charging of said capacitor in said integration circuit and being kept in a low-impedance state when said output voltage E.sub.o is at a high level to discharge electric charges stored in said capacitor;
• a voltage dividing circuit including a first voltage-dividing resistor and a second voltage-dividing resistor for conducting such a control as making said output voltage V'.sub.F of said integration circuit approximately equal to said reflected wave detection voltage V.sub.R in cooperation with said switching element, said first voltage-dividing resistor being connected to the output side of said operational amplifier and to the earth side of said capacitor in said integration circuit, said second voltage-dividing resistor being connected to a junction point of said capacitor and said first voltage-dividing resistor and to the ground, the resistance of said second voltage-dividing resistor being far smaller than the resistance of said first voltage-dividing resistor;
• and
• a smoothing circuit connected to the output side of said operational amplifier and to said standing wave ratio indication meter for deriving an average voltage corresponding to a ratio V.sub.R /V.sub.F of said reflected wave detection V.sub.R to said traveling wave detection voltage V.sub.F from said output voltage E.sub.o of said operational amplifier to supply said average voltage to said standing wave ratio indication meter.