CIRCUIT FOR COUPLING RADIO RECEIVER AND RADIO TRANSMITTER TO A COMMON ANTENNA FOR DUPLEX OPERATION

• US 3,733,608 A
• Filed: 12/09/1971
• Issued: 05/15/1973
• Est. Priority Date: 12/09/1971
• Status: Expired due to Term

• Current Assignee: Demetrios G. Afendras, Maynard H. Mcghay
• Original Assignee: Demetrios G. Afendras, Maynard H. Mcghay
• Inventors: McGhay, Maynard H., Afendras, Demetrios G.
• Primary Examiner(s): Gensler, Paul L.
• Application Number:
  US05/206,484
• Time in Patent Office: 523 Days
• Field of Search: 333/6,705,73R,76 334/42,43,45 325/21-25 343/180
• US Class Current: 370/339
• CPC Class Codes: H04B 1/50 using different frequencies for the two directions of communication

Abstract

Antenna coupling circuit for duplex radio transmission and reception by use of a common antenna (duplexer), including plurality of helical resonator sections provided within conductive enclosures in a conductive housing. A helical winding is provided in each enclosure having one end connected to the housing, and an adjustable conductive stud forms a capacitor with the other end of the winding. The winding and enclosure form a parallel tuned resonator, and the series capacitor forms therewith a series tuned circuit. One series tuned circuit at the receiver frequency is coupled to the antenna by a transmission line having a length equal to an odd multiple of a quarter wave length at the transmitter frequency, and this junction is connected to the transmitter through a circuit which may include additional tuned circuits. A second series tuned circuit at the transmitter frequency is coupled to the antenna by a transmission line having a length equal to an odd multiple of a quarter wave length at the receiver frequency, and this junction is connected to the receiver through a circuit which may include additional tuned circuits. A reactance may be connected in parallel with the first series tuned circuit to provide an anti-resonant circuit at the transmitter frequency, and a different reactance may be connected in parallel with the second tuned circuit to provide an anti-resonant circuit at the receiver frequency. Additional resonator sections can be connected in the transmitter and/or receiver branches of the circuit.

Claims

1. Coupling apparatus for selectively coupling signals from an antenna to a radio receiver operating on a first frequency band, and for coupling signals from a transmitter operating on a second frequency band closely spaced with respect to the first frequency band to the antenna, the coupling apparatus including in combination:

a conductive housing including a plurality of conductive enclosures;

antenna terminal means, receiver terminal means and transmitter terminal means connected to said housing;

a helical winding in each of said enclosures, each of said windings having first and second ends, with said first end connected to said conductive housing, and each winding forming with the associated conductive enclosure a helical resonator having parallel resonant characteristics;

first means coupled to said second end of one of said windings forming a variable capacitive reactance in series with said helical resonator formed thereby and cooperating therewith to provide a first series resonant circuit tuned to the second frequency band;

first transmission line means having a length equal to an odd multiple of a quarter wave length in the first frequency band connected to said first means for connecting said first series resonant circuit to said antenna terminal means;

first circuit means connecting said receiver terminal means to said first resonant circuit;

second means coupled to said second end of another one of said windings forming a variable capacitive reactance in series with said helical resonator formed Thereby and cooperating therewith to provide a second series resonant circuit tuned to the first frequency band;

second transmission line means having a length equal to an odd multiple of a quarter wave length in the second frequency band connected to said second means for connecting said second series resonant circuit to said antenna terminal means; and

second circuit means coupling said transmitter terminal means to said second resonant circuit.

2. Coupling apparatus in accordance with claim 1, further including first reactance means coupled across said first series resonant circuit and cooperating therewith to provide an anti-resonant circuit in the first frequency band, and second reactance means coupled across said second series resonant circuit and cooperating therewith to provide an anti-resonant circuit in the second frequency band.

3. Coupling apparatus in accordance with claim 2 wherein said conductive housing includes a conducting base portion, an insulator secured to said base portion for each helical winding, and a conductive plate secured to each of said insulators, and wherein said first and second reactance means each includes a capacitor having one electrode connected to said conducting base, and a second electrode connected to said conductive plate.

4. Coupling apparatus in accordance with claim 3 wherein said capacitors of said first and second reactance means are adjustable.

5. Coupling apparatus in accordance with claim 4 wherein one of said first and second reactance means includes a coil connected to said conducting base and to said conductive plate, in parallel with said capacitor thereof.

6. Coupling apparatus in accordance with claim 1 wherein said first circuit means includes a further helical winding cooperating with a further conductive enclosure to form a helical resonator, said further helical winding having first and second ends, with said first end connected to said enclosure, further means coupled to said second end of said further helical winding forming a further series resonant circuit tuned to the second frequency band, and further transmission line means having a length equal to an odd multiple of a quarter wave length in the first frequency band connecting said further series resonant circuit to said first series resonant circuit.

7. Coupling apparatus in accordance with claim 1 wherein said second circuit means includes a further helical winding cooperating with a further conductive enclosure to form a helical resonator, said further helical winding having first and second ends, with said first end converted to said enclosure, further means coupled to said second end of said further helical winding forming a further series resonant circuit tuned to the first frequency band, and further transmission line means having a length equal to an odd multiple of a quarter wave length in the second frequency band connecting said further series resonant circuit to said second series resonant circuit.

8. Coupling apparatus in accordance with claim 1 wherein said second circuit means includes a plurality of further helical windings cooperating with further conductive enclosures to form a plurality of helical resonators, said further helical windings each having first and second ends, with said first ends connected to said enclosures, further means coupled to said second ends of said further helical windings forming a plurality of further series resonant circuits tuned to the first frequency band, and a plurality of further transmission line means each having a length equal to an odd multiple of a quarter wave length in the second frequency band connected between said further series resonant circuits and connecting one of said further series resonant circuits to said first series resonant circuit.

9. Coupling apparatus in accordance with claim 1 wherein said conductive housing includes a conducting base portion, an insulator secured to said base portion for each helical winding, and a conductive plate secured to each of said insulators, and wherein said means coupled to said second end of said windings includes a threaded conductive stud supported by a threaded conductive sleeve secured to said conductive plate.

10. Coupling apparatus in accordance with claim 9 wherein said conducting base has openings therein, and said transmission line means each includes an outer conductor connected to said base and an inner conductor connected to one of said conductive plates.

11. Coupling apparatus in accordance with claim 9 wherein said threaded sleeve extends through said base portion and is insulated therefrom, and said conductive stud has an end accessible from the bottom of said base portion through said conductive sleeve to permit adjustment of said stud end of the capacitive reactance formed thereby.

12. Coupling apparatus in accordance with claim 11 including a capacitor extending through said base portion and having a first conductive electrode connected to said base portion and a second conductive electrode connected to said conductive plate, said capacitor having an adjustable element accessible from the bottom of said conductive base.

13. Coupling apparatus in accordance with claim 1 wherein said conductive housing includes an extruded aluminum member having a plurality of tubular sections, a base member at one end of said tubular sections and supporting said extrusion, and a top plate secured to said extrusions at the opposite end of said tubular sections, and wherein said helical windings are secured to said top plate and said means coupled to said second end of said windings is secured to said base member.

14. Coupling apparatus in accordance with claim 13 wherein said base member is channel shaped, and including a cover plate for said base member forming a closed structure therewith, and wherein said transmission line means is within said closed structure.