Phase shifter

Claim 2

A phase shifter adapted to operate at a preselected center frequency f 0 comprising: an input section of transmission line to which a signal may be applied; a second section of transmission line; a newtork coupled between said input and said second sections, said network comprising: a third section of transmission line matched in impedance to the input and second sections and coupling said input section to said second section; a reentrant transmission line network having substantially negligible energy storage capacity in shunt with said third section of transmission line and; means for switching said reentrant transmission line network between a first condition in which it appears like an open circuit to said input section and a second condition for introducing a differential phase shift to a signal propagating in said main transmission line.

Claim 3

A phase shifter as claimed in claim 1 wherein said reentrant transmission line network comprises first, second and third transmission paths connected in series with one another in the order named, said first and said third transmission paths being connected at one end to spaced points along said third section, and at their other end to opposite ends of said second path, said first and third paths each having a length of substantially (nλ/4) where n is an odd integer and λ is the wavelength of said center frequency, wherein said means for switching comprises first and second controllable differential phase shift means connected between said other end of said first and third paths, respectively, and a point of reference potential and wherein said second path is dimensioned such that it produces a resonance condition with said first and second controllable phase shift means at said frequency f 0 .

Claim 4

A phase shifter as claimed in claim 2 wherein said controllable differential phase shift means comprise diodes which are poled in the same direction.

Claim 5

A phase shifter as claimed in claim 3 wherein said first and third transmission paths have an impedance defined by the formula: Z.sub.1,3 =Z.sub.m √K/2 wherein: Z 1 ,3 =the impedance of the first or third transmission path; Z m =the impedance of said input section of transmission line; and K=Δφ/Δφ D wherein: Δφ is the phase shift of said phase shifter; and Δφ D is the differential phase shift of said diodes.

Claim 6

A phase shifter as claimed in claim 4 wherein said second transmission path has an impedance and length defined by the formula: Z.sub.2 l=(Z.sub.m νK/ω.sub.0) wherein: Z 2 l=the product of the impedance and the length of said second path; Z m =the impedance of said input section of transmission line; ν=the propagation velocity of a said second transmission path; and ω 0 =2πf 0 wherein: f 0 =said center frequency.

Claim 7

A phase shifter as claimed in claim 3 wherein said diodes comprise PIN diodes.

Claim 8

A phase shifter as claimed in claim 2 where said switching means comprises: a first diode connected between said other end of said first transmission path and ground; a second diode connected between said other end of said third transmission path and ground; and means for concurrently controlling the operating states of said diodes so that both of said diodes are in the same operating state.

Claim 9

A phase shifter as claimed in claim 1 wherein said phase shifter comprises: a plurality of said networks.

Claim 10

A phase shifter as claimed in claim 8 wherein each said reentrant transmission line network comprises first, second and third transmission paths connected in series with one another in the order named, said first and said third transmission paths being connected at one end to spaced points along said third section, and at their other end to opposite ends of said second path, said first and third paths each having a length of substantially (nλ/4) where n is an odd integer and λ is the wavelength of said center frequency, and wherein said means for switching comprises first and second controllable differential phase shift means connected between said other end of said first and third paths, respectively, and a point of reference potential.

Claim 11

A phase shifter as claimed in claims 8 or 9 wherein each said controllable differential phase shift means comprise diodes which are poled in the same direction.

Claim 12

A phase shifter as claimed in claim 10 wherein each said first and third transmission path has an impedance defined by the formula: Z.sub.1,3 =Z.sub.m √K/2 wherein: Z 1 ,3 =the impedance of the first or third transmission path; Z m =the impedance of said input section of transmission line; and K=Δφ/Δφ D wherein: Δφ is the phase shift of said phase shifter; and Δφ D is the differential phase shift of said diodes.

Claim 13

A phase shifter as claimed in claim 11 wherein each said second transmission path has an impedance and length defined by the formula: Z.sub.2 l=(Z.sub.m νK/ω.sub.0) wherein: Z 2 l=the product of the impedance and the length of said second path; Z m =the impedance of said input section of transmission line; ν=the propagation velocity of a said second transmission path; and ω 0 =2πf 0 wherein: f 0 =said center frequency.

Claim 14

A phase shifter as claimed in claim 9 wherein each said switching means comprises: a first diode connected between said other end of said first transmission path and ground; a second diode connected between said other end of said third transmission path and ground; and means for concurrently controlling the operating states of said diodes so that both of said diodes are in the same operating state.

Claim 15

A phase shifter as claimed in claims 1 or 8 wherein: said phase shifter is a microstrip circuit.