Dual band electrically small tunable antenna

• US 8,629,811 B2
• Filed: 09/15/2011
• Issued: 01/14/2014
• Est. Priority Date: 09/15/2011
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Grandfield, John E., Abban, Michael P., Gaynor, Brad D.
• Primary Examiner(s): LE, HOANGANH T
• Application Number:
  US13/233,411
• Publication Number:
  US 20130069838A1
• Time in Patent Office: 852 Days
• Field of Search: 343/700.MS, 343/895, 343/729, 343/725
• US Class Current: 343/729
• 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 5/40 Imbricated or interleaved structures; Combined or electromagnetically coupled arrangements, e.g. comprising two or more non-connected fed radiating elements
• CPC Class Codes: H01Q 7/005 with variable reactance for tuning the antenna
• CPC Class Codes: H01Q 9/0421 with a shorting wall or a shorting pin at one end of the element H01Q9/0414 takes precedence
• CPC Class Codes: H01Q 9/0442 with particular tuning means

Abstract

An electrically small dual-band planar tunable UHF/L-Band antenna. In one example, the dual-band antenna includes a combination of a semi-spiral antenna for the UHF frequencies and a microstrip patch antenna for the L-band frequencies.

Claims

1. A tunable dual-band antenna comprising:

a substrate;

a semi-spiral antenna disposed on a first surface of the substrate;

a microstrip patch antenna disposed on the first surface of the substrate within a circumference of the semi-spiral antenna;

a ground plane disposed on a second opposing surface of the substrate; and

a variable capacitor coupled to the semi-spiral antenna, the variable capacitor being configured to adjust an electrical length of the semi-spiral antenna to tune a resonant frequency of the semi-spiral antenna.

2. The tunable dual-band antenna of claim 1, wherein the semi-spiral antenna is an ultra high frequency (UHF) antenna, and the patch antenna is an L-band antenna.

3. The tunable dual-band antenna of claim 2, wherein the tunable dual-band antenna has a length of approximately 1.5 inches and a width of approximately 1.5 inches.

4. A method of tuning a dual-band antenna including a semi-spiral antenna configured to ultrahigh frequency (UHF) operation and a patch antenna configured for L-band operation, the method comprising:

feeding a UHF pilot tone to the patch antenna, a frequency of the UHF pilot tone corresponding to a selected resonant frequency of the semi-spiral antenna;

coupling the pilot tone to the semi-spiral antenna;

monitoring a gain of the semi-spiral antenna at the frequency of the UHF pilot tone; and

adjusting an electrical length of the semi-spiral antenna responsive to the gain of the semi-spiral antenna to tune the semi-spiral antenna to the selected resonant frequency.

5. The method of claim 4, wherein adjusting the electrical length of the semi-spiral antenna includes controlling a capacitance of a variable capacitor coupled to the semi-spiral antenna.

6. The method of claim 5, wherein controlling the capacitance of the variable capacitor includes adjusting a DC bias voltage applied to the variable capacitor.

7. The method of claim 4, wherein monitoring the gain of the semi-spiral antenna includes determining whether the gain is below an expected maximum gain of the semi-spiral antenna at the frequency of the UHF pilot tone;

and

wherein adjusting the electrical length of semi-spiral antenna includes adjusting the electrical length responsive to determining that the gain of semi-spiral antenna is below the expected maximum gain.

8. The method of claim 4, further comprising:

feeding an L-band pilot tone to the semi-spiral antenna, a frequency of the L-band pilot tone corresponding to a selected L-band resonant frequency of the patch antenna;

coupling the L-band pilot tone to the patch antenna;

monitoring a gain of the patch antenna at the frequency of the L-band pilot tone; and

tuning the patch antenna responsive to the gain of the patch antenna being below an expected maximum gain at the frequency of the L-band pilot tone.

9. The method of claim 8, wherein tuning the patch antenna includes adjusting an electrical length of the patch antenna to tune the patch antenna to the selected resonant L-band frequency.

10. A tunable dual-band antenna system comprising:

a tunable dual-band antenna including a semi-spiral ultra high frequency (UHF) antenna disposed on a first surface of a substrate, and an L-band patch antenna disposed on the first surface of the substrate within a circumference of the semi-spiral UHF antenna and electromagnetically coupled to the semi-spiral UHF antenna;

a variable capacitor coupled to the semi-spiral UHF antenna; and

a controller coupled to the variable capacitor and configured to control a capacitance of the variable capacitor to adjust an electrical length of the semi-spiral UHF antenna to tune the semi-spiral UHF antenna to a selected UHF resonant frequency.

11. The tunable dual-band antenna system of claim 10, wherein the controller is further configured to:

direct a pilot tone having the selected UHF frequency to be fed to the L-band patch antenna;

monitor a gain of the semi-spiral UHF antenna at the selected UHF frequency; and

control the capacitance of the variable capacitor responsive to determining that the gain of the semi-spiral UHF antenna is below an expected maximum gain.

12. The tunable dual-band antenna system of claim 11, wherein the variable capacitor is a varactor.

13. The tunable dual-band antenna system of claim 12, wherein the controller includes a DC bias circuit coupled to the varactor.

14. The tunable dual-band antenna system of claim 11, further comprising a fixed capacitor disposed on the substrate and coupled to the semi-spiral UHF antenna, wherein the variable capacitor is coupled to the semi-spiral UHF antenna via the fixed capacitor.