Loop antenna with reduced electrical field sensitivity

• US 5,826,178 A
• Filed: 01/29/1996
• Issued: 10/20/1998
• Est. Priority Date: 01/29/1996
• Status: Expired due to Term

• Current Assignee: Cufer Asset Ltd LLC (Intellectual Ventures LLC)
• Original Assignee: Seiko Communication Systems, Inc.
• Inventors: Owen, Jeffrey R.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Armstrong, Darnell R.
• Application Number:
  US08/592,908
• Time in Patent Office: 995 Days
• Field of Search: 455/129, 455/193.1, 455/121, 455/122, 455/123, 455/562, 455/575, 343/742, 343/741, 343/744
• US Class Current: 455/193.1
• CPC Class Codes: H01Q 7/005 with variable reactance for tuning the antenna
• CPC Class Codes: H04B 1/18 Input circuits, e.g. for coupling to an antenna or a transmission line coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H

Abstract

A small, high Q loop antenna configured on a printed circuit board as a planar structure receives a radio signal and shields its interior planar area against interfering electric field energy while concentrating therein radio signal magnetic flux. A magnetic pickup loop, coplanar to the antenna loop and magnetically coupled thereto, receives the radio signal power by virtue of its magnetic coupling to the loop antenna. The magnetic pickup loop couples to a receiving device and delivers the radio signal thereto. Illustrated embodiments include loop antennas tunable to a desired resonant frequency.

Claims

1. A radio signal receiving device for receiving radio signals of a particular frequency comprising:

a planar antenna loop structure;

a magnetic pickup device coplanar to said antenna loop structure, located within said antenna loop structure, and offset from the center of said loop structure, said magnetic pickup being electrically isolated at said particular frequency; and

a radio signal receiving device coupled to said magnetic pickup device;

wherein the location of said magnetic pickup device relative to said antenna loop is selected to minimize capacitive coupling between said magnetic pickup device and said antenna loop.

2. A radio signal receiving device for receiving radio signals of a particular frequency comprising:

a planar antenna loop structure;

a magnetic pickup device coplanar to said antenna loop structure and located within said antenna loop structure said magnetic pickup being electrically isolated at said particular frequency;

radio signal receiving device coupled to said magnetic pickup device; and

two series capacitors placed at two symmetrically opposite locations along said loop structure.