CAVITY BACKED DIPOLE-SLOT ANTENNA FOR CIRCULAR POLARIZATION

• US 3,813,674 A
• Filed: 01/04/1973
• Issued: 05/28/1974
• Est. Priority Date: 01/05/1972
• Status: Expired due to Term

• Current Assignee: Michael John Sidford
• Original Assignee: Michael John Sidford
• Inventors: Sidford, Michael John
• Primary Examiner(s): Lieberman, Eli
• Application Number:
  US05/321,083
• Time in Patent Office: 509 Days
• Field of Search: 343/727,767,769,789,803,854 333/84M
• US Class Current: 343/730
• CPC Class Codes: H01Q 13/18 the slot being backed by, or formed in boundary wall of, a resonant cavity longitudinally slotted cylinder H01Q13/12 ; Open cavity antennas
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 9/065 Microstrip dipole antennas patch antenna H01Q9/0407

Abstract

Aerial for receiving or transmitting circularly polarized electromagnetic radiation includes a dipole mounted substantially within the aperture of a slot and means for coupling the slot to the dipole asymmetrically. It may also include an electromagnetic cavity adjacent the coupled dipole and slot. In one embodiment the dipole is formed on one side of an insulating substrate and a narrow conductor is formed on the other side substantially opposite the dipole, with part of the dipole, the substrate, and the conductor together forming a stripline feed which may have a matching network formed by a further part of the dipole, the substrate, and the conductor.

Claims

1. An aerial for receiving or transmitting circularly polarized electromagnetic radiation comprising an insulating substrate on one side of which is formed a dipole, said dipole being mounted substantially within the aperture of a slot antenna, means for coupling the slot antenna to the dipole asymmetrically with respect to a line of symmetry of the dipole, an electromagnetic cavity adjacent the coupled dipole and slot antenna, and a narrow conductor formed on the other side of said substrate substantially opposite the dipole and disposed such that part of the dipole, the substrate, and the conductor together form a stripline feed, said means for coupling the slot antenna to the dipole asymmetrically comprising another conductor formed on the same side of the substrate as the narrow conductor but insulatedly separated from it and positioned over the dipole and the slot antenna so as to couple them together capacitively.

2. An aerial for receiving or transmitting circularly polarized electromagnetic radiation including a dipole mounted substantially within the aperture of a slot antenna, an electromagnetic cavity adjacent the coupled dipole and slot and having a depth of less than lambda /10, where lambda is the wavelength of the radiation, means for coupling the slot antenna to the dipole asymmetrically with respect to a line of symmetry of the dipole for determining the relative phase and amplitude of the responses of the slot antenna and the dipole to the radiation, and means connected to the dipole for feeding alternating electrical signals at the frequency of the radiation to the dipole and thus via the coupling means to excite the slot antenna.

3. An aerial as claimed in claim 2, and wherein the dipole is a folded dipole.

4. An aerial as claimed in claim 2 and further including an insulating substrate on one side of which is formed the dipole, and a narrow conductor formed on the other side of said substrate substantially opposite the dipole, disposed such that part of the dipole the substrate and the conductor together form a stripline feed.

5. An aerial as claimed in claim 2 wherein the means for coupling the slot to the dipole asymmetrically with respect to a line of symmetry of the dipole is another conductor formed on the same side of the substrate as the narrow conductor but insulatedly separated from it and positioned over the dipole and the slot so as to couple them together capacitively.

6. An aerial as claimed in claim 2 wherein the means for coupling includes an electronic switch device for controlling the phase between the responses of the slot and the dipole to the radiation afforded by said means for coupling.