Microwave circulator comprising a plurality of directional couplers connected together by isolation amplifiers

Claim 2

A circulator comprising at least three hybrid directional couplers, each of said hybrid directional couplers having four ports, one of said ports receiving a microwave signal which is transmitted to a diagonally opposite second port, the third port receiving a fixed fraction of the power and the fourth port receiving effectually no power, at least three isolator means, each of said isolator means connecting said second port of one of said at least three hybrid directional couplers to said third port of another of said at least three hybrid directional couplers so that each directional coupler is connected to another via an isolator means to form a circulator having at least three arms, each of said isolator means being configured to transmit a microwave signal from said second port of one of said hybrid directional couplers to said third port of said another of said hybrid directional couplers and imposing a substantial insertion loss in any reflected signals transmitting in a direction opposite thereto.

Claim 3

The circulator according claim 1 wherein each of said isolator means comprises: means for amplifying a microwave signal; and means connected to said amplifying means for transmitting said microwave signal while isolating said amplifying means from signals travelling in a direction opposite to said microwave signal to be transmitted.

Claim 4

The circulator according to claim 1 wherein each of said isolator means comprises: means for amplifying a microwave signal, said means for amplifying taking the form of a common gate FET; means connected to said amplifying means for transmitting said microwave signal while isolating said amplifying means from signals travelling in a direction opposite to said microwave signal to be transmitted, said means for transmitting taking the form of a common drain FET exhibiting substantial insertion loss for reflected signals travelling in said direction opposite to said microwave signal to be transmitted; a capacitor interposed in a signal path between said means for amplifying and said means for transmitting, said capacitor being sized to pass high frequency signals to said common drain FET and block low frequency signals in either direction in said signal path; and a plurality of series L-C circuits, each of said plurality of series L-C circuits being connected intermediate a reference point and selected portions of one of said means for amplifying and said means for transmitting to drain off low frequency signals and noise.