NEAR FIELD SPIRAL ANTENNA

• US 3,780,373 A
• Filed: 11/21/1972
• Issued: 12/18/1973
• Est. Priority Date: 11/21/1972
• Status: Expired due to Term

• Current Assignee: Paul F.G. Holst, William R. Brobeck
• Original Assignee: Paul F.G. Holst, William R. Brobeck
• Inventors: Brobeck, William R., Holst, Paul F. G.
• Primary Examiner(s): Lieberman, Eli
• Application Number:
  US05/308,374
• Time in Patent Office: 392 Days
• Field of Search: 343/788,846,872,873,895
• US Class Current: 343/788
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 9/27 Spiral antennas

Abstract

A near field antenna is formed of a coil printed on an insulating board mounted in parallel fixed spaced relationship to its own ground plane. The coil is capacitively shunt tuned and capacitively coupled serially to a coaxial line. A planar ferrite sheet may be incorporated to enhance the sensitivity of the antenna. The printed coil is provided with means for adjustably fixing its length.

Claims

1. A near field antenna comprising:

an insulated printed circut board having at least first and second terminals thereon;

a planar spiral conductor on said board, one end of said spiral conductor being connected to said first terminal;

a length of additional conductor;

means for connecting selected portions of said additional conductor between the other end of said spiral conductor and said second terminal;

capacity shunt tuning means connected across said spiral conductor and said additional conductor;

an output circuit;

capacity coupling means between said spiral conductor and said output circuit; and

a metal sheet mounted under said printed circuit in parallel fixed spaced relationship to the plane of said spiral conductor.

2. The invention as defined in claim 1 wherein a plurality of taps each are connected to a respective point along the length of said additional conductor, one end of said additional conductor being connected to said second terminal;

and means for connecting the other end of said spiral conductor to a selected tap.

3. The invention as defined in claim 2 wherein said means for connecting said other end of said spiral conductor to a selected tap comprises a second additional conductor.

4. The invention as defined in claim 3 wherein said second additional conductor is pivotally connected to said other end of said spiral conductor, the other end of said additional conductor being connectable to a selected tap.

5. The invention as defined in claim 3 wherein said means for connecting the other end of said spiral conductor to a selected tap comprises a bare wire electrically connected between said other end and a selected one of said taps.

6. The invention as defined in claim 1, and an insulated rectangular housing, said printed circuit board being seated on one end of said housing, said metal sheet being seated on the opposing end of said housing, whereby said planar sheet and said printed circuit board are maintained in parallel fixed spaced relationship.

7. The invention as defined in claim 1 wherein said metal sheet is maintained in parallel fixed spaced relationship to the plane of said spiral conductor by means of a plurality of spacer pins, the space between said printed circuit board and said metal sheet being filled wiTh an insulating potting material.

8. The invention as defined in claim 1 wherein a ferrite sheet is positioned between said insulated printed circuit board and said metal sheet.

9. A near field antenna comprising:

an insulated printed circuit board having at least first and second terminals thereon;

a planar spiral conductor on said board, one end of said spiral conductor being connected to said first terminal;

a length of additional wire conductor connected between the other end of said spiral conductor and said second terminal;

said wire conductor being movably arranged to change the area enclosed by the inner turn of said spiral conductor;

capacity shunt tuning means connected across said spiral conductor and said additional conductor;

an output circuit;

capacity coupling means between said spiral conductor and said output circuit; and

a metal sheet mounted under said printed circuit in parallel fixed spaced relationship to the plane of said spiral conductor.