US 4,359,743 A · Broadband RF isolator

Abstract

A broadband RF isolator system for connection between RF devices such as inear antennas is disclosed. In accordance with this invention, two or more antennas are spaced several wavelengths apart, connected to coaxial feeds and choked at their adjacent ends to establish the electrical length. In one embodiment of the invention, the isolator is formed by placing a second line adjacent the coaxial line connected to the upper antenna. The addition of this second line forms a balanced transmission line having a given characteristic impedance. The second line is terminated at one end by a resistor having a resistance equal to the value of the characteristic impedance. In a second embodiment the second line is replaced by a coaxial sleeve which is also terminated at one end with a resistor having a resistance value equal to the characteristic impedance. In four additional embodiments, which are essentially variations of the second basic embodiment, coaxial sleeves are also utilized to form the isolation system.

Claims17

Dependent claims

A broadband RF isolator system comprising:

at least one RF device;
said RF device including a conductive RF shield means for reducing the effects of RF fields on a portion of said RF device;
said RF device having means for inducing stray RF currents on the outside surface of said shield means;
isolator means coupled to said shield means for suppressing said stray RF currents;
said isolator means including a first conductor and a resistor;
said first conductor and said outside surface of said shield means forming a transmission line means of substantial electrical length;
and
said resistor connected between said shield means and said first conductor and having an impedance substantially equal to the characteristic impedance of said transmission line means.

5 more elements

In an antenna system comprising:

at least a first and a second antenna;
said second antenna being spaced apart from said first antenna;
a first coax feeder cable connected to said first antenna and a second coax feeder cable connected to said second antenna;
said second coax feeder cable passing through said first antenna;
an RF isolator means for forming a transmission line of substantial electrical length with a linear section of said second coax feeder cable, said RF isolator means being mounted between said first and second antennas;
and
resistance means connected between said means for forming a transmission line and said second coax feeder cable and having a resistance valve equal to the characteristic impedance of said transmission line.

4 more elements

A broadband antenna system for at least first and second radio apparatus adapted to operate simultaneously in relative close proximity, comprising in combination:

at least two dipole antennas, each including a pair of tubular radiating elements, respectively coupled to said first and second radio apparatus, said antennas being mounted one above the other and having a predetermined spacing therebetween with said respective pairs of radiating elements being aligned generally along a common vertical axis;
a first coaxial transmission feedline coupling said first radio apparatus to the upper dipole antenna, running through the pair of radiating elements of said lower dipole antenna and the lower radiating element of said upper dipole antenna and additionally being configured to provide a first cable choke section adjacently below the lower radiating element of the upper dipole antenna, a second cable choke section adjacently above the radiating element of the lower dipole antenna, and a third cable choke section adjacently below the lower radiating element of the lower dipole antenna;
a second coaxial transmission feedline coupling said second radio apparatus to the lower dipole antenna, being fed through the lower radiating element thereof, and configured to provide a fourth cable choke section adjacently below the lower radiating element of said lower dipole antenna;
an RF isolator comprising a third transmission line means of substantial electrical length coupled to said first transmission feedline intermediate said first and second cable choke sections, the third transmission line means being formed from a straight part of the first transmission feedline between said first and second cable choke sections and at least one additional element, the lengthwise direction of said at least one additional element and said straight part of the first transmission feedline being parallel, and resistance means connected between said at least one additional element and said first transmission feedline said resistance means having a value substantially equal to the value of the characteristic impedance of the third transmission line.

1 more element

Dependencies are inferred from the claim text.

Broadband RF isolator

Life of this patent

Broadband RF isolator

Life of this patent

Abstract

Claims17