Active element microwave power coupler

Claim 2

An RF coupler for connecting RF signals within an operating RF frequency band between two branch terminals and a common terminal, comprising: first and second leads each having one end joined to said common terminal; said first lead coupled to a first one of said branch terminals through a first dual gate FET device having its second gate terminated by a first reactance which is capacitive in said operating RF frequency band; said second lead coupled to the second one of said branch terminals through a second dual gate FET device having its second gate terminated by a second reactance which is inductive in said operating RF frequency band; and means for providing DC bias to the sources, drains, and second gates of said first and second dual gate FET devices, said means for providing DC bias supplying a value of bias to said second gate of said first dual gete FET device which in cooperation with said first reactance yields a desired reference transmission phase shift between said common terminal and said first branch terminal and supplying a value of bias to said second gate of said second dual gate FET device which in cooperation with said second reactance yields a transmission phase shift between said common terminal and said second branch terminal which differs from said reference phase shift by a desired, non-zero, relative phase shift of φ degrees.

Claim 3

The coupler recited in claim 1 wherein: said relative phase shift φ is substantially 90 degrees or less.

Claim 4

The coupler recited in claim 2 wherein φ is substantially 45.

Claim 5

The coupler recited in claim 1 wherein: said bias value on said second gate of said first transistor produces a gain of K; and said bias value on said second gate of said second transistor is additionally selected to produce a gain of K.

Claim 6

The coupler recited in claim 1 wherein: said first lead has its second end coupled to the first gate of said first FET device; said second lead has its second end coupled to the first gate of said second FET device; the drain of said first FET device is coupled to said first branch terminal; and the drain of said second FET device is coupled to said second branch terminal whereby said coupler functions as a power splitter.

Claim 7

The coupler recited in claim 1 wherein: said first lead has its second end coupled to the drain of said first FET device; said second lead has its second end coupled to the drain of said second FET device; the first gate of said first FET device is coupled to said first branch terminal; and the first gate of said second FET device is coupled to said second branch terminal whereby said coupler functions as a power combiner.

Claim 8

The coupler recited in claim 1 including: a third dual gate FET device having its first gate coupled to the drain of said first FET device and its second gate reactively terminated by a reactance of the same type as said first reactance; and a fourth dual gate FET device having its first gate coupled to the drain of said second FET device and its second gate reactively terminated by a reactance of the same type as said second reactance; said means for providing DC bias providing DC bias to the sources, drains and second gates of said third and fourth FET devices.

Claim 9

The coupler recited in claim 7 wherein said first reactance is capacitive and said second reactance is inductive, the values of said reactances and said bias at said second gates being selected whereby said coupler is a quadrature coupler.

Claim 10

A coupler for connecting RF signals between two branch terminals and a common terminal comprising: first and second leads each having one end joined to said common terminal; said first lead coupled to a first one of said branch terminals through a series connection of first and second dual gate FET devices, said first dual gate FET device having its second gate capacitively terminated, said second dual gate FET device having its first gate coupled to the drain of said first dual gate FET devices and having its second gate capacitively terminated, means for applying biasing potential to said first and second FET devices, said second gates of said first and second FET devices being biased at a voltage which causes a signal transmitted between said common terminal and said first branch terminal to experience a reference phase shift; and said second lead coupled to the second one of said branch terminals through a series connection of third and fourth dual gate FET devices, said third dual gate FET device having its second gate inductively terminated, said fourth dual gate FET device having its first gate coupled to the drain of said third dual gate FET device and having its second gate inductively terminated, means for applying biasing potentials to said third and fourth FET devices, said second gates of said third and fourth dual gate FET devices being biased at a voltage which causes a signal transmitted between said common terminal and said second branch terminal to experience a relative phase shift of substantially 90° with respect to said reference phase shift.

Claim 11

A coupler for connecting RF signals between two branch terminals and a common terminal comprising: first and second leads each having one end joined to said common terminal; said first lead coupled to a first one of said branch terminals through a series connection of first and second dual gate FET devices, said first dual gate FET device having its second gate capacitively terminated, said second dual gate FET device having its first gate coupled to the drain of said first dual gate FET devices and having its second gate capacitively terminated, means for applying biasing potential to said first and second FET devices, said second gates of said first and second FET devices being biased at a voltage which causes a signal transmitted between said common terminal and said first branch terminal to experience a reference phase shift; and said second lead coupled to the second one of said branch terminals through a series connection of third and fourth dual gate FET devices, said third dual gate FET device having its second gate inductively terminated, said fourth dual gate FET device having its first gate coupled to the drain of said third dual gate FET device and having its second gate inductively terminated, means for applying biasing potentials to said third and fourth FET devices, said second gates of said third and fourth dual gate FET devices being biased at a voltage which causes a signal transmitted between said common terminal and said second branch terminal to experience a relative phase shift of substantially 90° with respect to said reference phase shift.

Claim 12

The coupler of claim 9 wherein: said bias voltage on said second gates of said third and fourth FET devices produces a gain of K between said common terminal and second branch terminal; and said bias voltage on said second gates of said first and second FET devices is selected to produce a gain of substantially K between said common terminal and said first branch terminal.