Patent ID: 6977554

Claim:
A variable gain amplifier, comprising: a divider for dividing a input signal; a fixed variable gain amplifier for amplifying an output signal of the divider; a microstrip ring hybrid for outputting a plurality of signals which have the same or different phases, the microstrip ring hybrid comprising a plurality of input terminals and output terminals having a constant impedance; a switch for selectively inputting an output of the variable gain amplifier to any one of the input terminals of the microstrip ring hybrid; a transmission line for delaying the output signal of the divider; and a combiner for combining each of the output signals of the microstrip ring hybrid and a signal passing through the transmission line and outputting the combined signal, wherein the output power is controlled by selectively inputting the output of the variable gain amplifier to any one of the input terminals of the microstrip ring hybrid by means of the switches.