US 4,602,227 AGranted

Coaxial LC phase-shifter for phase-controlled television broadcast switching circuit

AssigneeRCA Corporation

InventorsRaymond N. Clark, Anthony N. Schmitz

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Abstract

A television broadcast transmitter includes two power amplifiers or transmitters, a dummy load and an antenna. A noncontacting switching arrangement includes directional couplers or hybrids operated as controllable phase-shifters under the control of pairs of variable reactive terminations. Signals arriving at the antenna or load port by two paths combine in-phase to couple signal to that port, or combine out-of-phase to cancel signal. If the out-of-phase condition is inaccurate, cancellation may be incomplete, resulting in crosstalk. To avoid the need for accurate positioners to position the variable reactive termination at the position providing the desired phase-shift, a particular structure of the reactive termination is used. The reactive termination is a short-circuited coaxial line with an axial gap in the center conductor at a position less than one quarter operating frequency wavelength from the short circuit. The center conductor is hollow around the gap and lined with insulating material, and an elongated conductive slug is actuated to selectively occupy one or two positions within the center conductor, one position remote from the gap whereby a minimum series capacitance results, and the second position straddling the gap, whereby the series capacitance increases. The slug is actuated by a rod passing through the short circuit. The rate of change of phase-shift as a function of actuator position is small near the extremes of actuation positions, whereby errors in actuator position do not affect the phase-shift.

Claims18

Dependent claims

An arrangement for controlling high-power, high-frequency first and second signals from first and second sources, respectively, for switching said first and second signals between first and second loads in a first mode of operation and for combining said first and second signals and applying the resulting combined signal to one of said first and second loads in a second mode of operation, said arrangement comprising:

a first coupler comprising first, second, third and fourth ports, said first and second ports being input ports coupled to said first and second sources, respectively, and said third and fourth ports being output ports, each of which produces a combination signal resulting from a combination of said first and second signals;
second and third couplers, each having an input port, an output port, and third and fourth additional ports, said input ports of each of said second and third couplers being coupled to said third and fourth output ports of said first coupler, respectively, for providing phase-shifts to said respective combination signals as they pass between said input and output ports of each of said second and third couplers;
a fourth coupler comprising first and second input ports coupled to said output ports of said second and third couplers, respectively, for receiving phase-shifted combination signals therefrom, and further comprising a first output port coupled to said first load and a second output port coupled to said second load;
and
reactive terminating means coupled to said third and fourth additional ports of said second and third couplers for controlling the magnitude of said phase-shifts for selecting one of said first and second modes of operation, said reactive terminating means comprising first and second pairs of coaxial inductance-capacitance circuits, said first pair of coaxial inductance-capacitance circuits being coupled to said third and fourth additional ports of said second coupler, said second pair of coaxial inductance-capacitance circuits being coupled to said third and fourth additional ports of said third coupler, each of said coaxial inductance-capacitance circuits including elongated coaxial transmission-line means including an outer conductor without a gap, first and second portions of a hollow inner conductor concentric with said outer conductor, said first portion of said inner conductor being axially separated from said second portion of said inner conductor by a non-conductive gap, and the end of said second portion of said inner conductor remote from said gap being short-circuited to said outer conductor, the length of said second portion being less than one-quarter wavelength at said high frequency.

2 more elements

An improved arrangement for switching signals from first and second sources of first and second high-power signals at a high operating frequency respectively, between first and second loads in a first mode of operation, and for combining said first and second signals from said first and second source for application to one of said first and second loads in a second mode of operation, said arrangement comprising:

first and second transmission-lines mutually coupled along quarter-wavelength portions for forming a first coupler, said first coupler having first and second ports each of which is coupled to one end of said quarter-wavelength portions of said first transmission-line, said first coupler having third and fourth ports each of which is coupled to one end of said quarter-wavelength portion of said second transmission-line;
third and fourth transmission-lines mutually coupled along quarter-wavelength portions for forming a second coupler, said second coupler having first and second ports, each of which is coupled to one end of said quarter-wavelength portion of said third transmission line, said second coupler having third and fourth ports, each of which is coupled to one end of said quarter-wavelength portion of said fourth transmission-line;
third and fourth couplers each including first and second input ports and third and fourth output ports;
said first source being coupled with said first input port of said third coupler, said second source being coupled with said second input port of said third coupler, said third output port of said third coupler being coupled with said first port of said first coupler, said fourth output port of said third coupler being coupled with said first port of said second coupler, said third port of said first coupler being coupled with said first input port of said fourth coupler;
said third port of said second coupler being coupled with said second input port of said fourth coupler;
said third output port of said fourth coupler being coupled with said first load;
and said fourth output port of said fourth coupler being coupled with said second load, the improvement comprising
first and second coaxial inductance-capacitance circuits coupled to said second and fourth ports of said first coupler respectively, and third and fourth inductance-capacitance circuits coupled to said second and fourth ports of said second coupler, respectively, for providing a reactive termination for each of said second and fourth ports of said first and second couplers;
and
each of said first, second, third and fourth coaxial inductance-capacitance circuits including
elongated coaxial transmission line means comprising an elongated outer conductor without a gap and an inner conductor, said inner conductor having a gap at a transverse location thereby dividing said inner conductor into a first portion proximate an input end of said coaxial inductance-capacitance circuit and a second portion remote from said input end, said inner conductor further including a hollow along at least a portion of its length in the vicinity of said gap;
conductive shorting means coupled to said second portion of said inner conductor and to said outer conductor for short-circuiting said inner conductor to said outer conductor at a location less than one quarter-wavelength at the operating frequency from said gap;
elongated conductive capacitance varying means movably located within said hollow to occupy a range of positions extending from a first position straddling said gap to a second position entirely within one of said first and second portions of said inner conductor;
and
control means for controlling said capacitance varying means in pairs for controlling the coupling between said sources and said loads.

12 more elements

a first coupler comprising first, second, third and fourth ports, said first and second ports being input ports coupled to said first and second sources, respectively, and said third and fourth ports being output ports, each of which produces a combination signal resulting from a combination of said first and second signals;
a second coupler comprising first and second input ports adapted for receiving phase-shifted combination signal, and further comprising a first output port coupled to said first load and a second output port coupled to said second load;
phase shifting means coupled to said first and second couplers for coupling and phase-shifting said combination signal from said third port of said first coupler to said first input port of said said second coupler and for coupling and phase-shifting said combination signal from said fourth port of said first coupler to said second input port of said second coupler, said phase shifting means comprising coupling means including an input port coupled to one of said third and fourth ports of said first coupler for receiving said combination signal therefrom and also including an output port coupled to one of said first and second input ports of said second coupler for coupling phase-shifted combination signal thereto, said coupling means further including third and fourth additional ports;
and
reactive terminating means coupled to said third and fourth additional ports of said coupling means for controlling the magnitude of said phase-shift for selecting one of said first and second modes of operation, said reactive terminating means comprising a pair of coaxial inductance-capacitance circuits, each member of said pair of coaxial inductance-capacitance circuits being coupled to one of said third and fourth additional ports of said coupling means, each of said coaxial inductance-capacitance circuits including elongated coaxial transmission-line means including an outer conductor without an axial gap and an inner conductor, said inner conductor including first and second portions concentric with said outer conductor, said first portion of said inner conductor being axially separated from said second portion of said inner conductor by a non-conductive gap, and the end of said second portion of said inner conductor remote from said gap being short-circuited to said outer conductor at a position selected so that the length of said second portion between said gap and the position of said short-circuit is less than one-quarter wavelength at said high frequency.

2 more elements

Dependencies are inferred from the claim text.