High Efficiency Ferrite Antenna System

• US 20070222695A1
• Filed: 01/26/2007
• Published: 09/27/2007
• Est. Priority Date: 01/31/2006
• Status: Active Grant

• Current Assignee: Irvine Company LLC
• Original Assignee: Power Technologies Limited (Altron Ltd.)
• Inventors: Davis, Steven
• Granted Patent: US 7,642,983 B2
• Time in Patent Office: Days
• US Class Current: 343/788
• CPC Class Codes: H01Q 7/005 with variable reactance for tuning the antenna
• CPC Class Codes: H01Q 7/08 Ferrite rod or like elongated core

Abstract

An automatic tuning procedure can be used to allow a small, high efficiency ferrite antenna assembly to be used in various FM frequency based devices. The ferrite antenna can take the form of a rod or flat disk, for example, which can use a pick-up coil and tuning coil to provide sufficient signal strength using a small FM antenna. A balanced amplifier can be used to provide differential input in order to further reduce noise. A microcontroller can determine the strength of the FM signal at various frequencies and can automatically tune the operating frequency to optimize system performance.

Claims

1. An antenna assembly for use with an FM frequency device, comprising:

a ferrite rod;

a single turn tuning coil wound about a first portion of the ferrite rod, the single turn tuning coil operable to receive a tuning frequency and adjust the resonant frequency of the ferrite rod in response thereto; and

a multi-turn pick-up coil wound about a second portion of the ferrite rod, the multi-turn pick-up coil capable of having a voltage induced thereon by a received FM signal at the adjusted resonant frequency, the multi-turn pick-up coil being further configured to provide the received FM signal as output.

2. An antenna assembly according to claim 1, wherein:

the at least one of the tuning and pick-up coils is formed of a copper tape.

3. An antenna assembly according to claim 1, wherein:

the ferrite rod is about 1 inch in length.

4. An antenna assembly according to claim 1, wherein:

the multi-turn pick-up coil further includes a tap allowing the output to be applied to a pair of differential amplifiers.

9. An antenna assembly according to claim 1, wherein:

the ferrite disk is about 40 mm in length and about 40 mm in width.

5. An antenna assembly for use with an FM frequency device, comprising:

a substantially flat ferrite disk; and

a pick-up coil placed around a periphery of the ferrite disk, the pick-up coil capable of having a voltage induced thereon by a received FM signal at a resonant frequency of the ferrite disk, the pick-up coil being further configured to provide the received FM signal as output.

6. An antenna assembly according to claim 5, further comprising:

a tuning coil positioned about the periphery of the ferrite disk, the tuning coil operable to receive a tuning frequency and adjust the resonant frequency of the ferrite disk in response thereto.

7. An antenna assembly according to claim 6, wherein:

the pick-up coil is formed of a copper tape.

8. An antenna assembly according to claim 6, wherein:

the pick-up coil is formed of a metal frame.

10. An antenna system for use with an FM frequency device, comprising:

a ferrite antenna including a tuning coil and a pick-up coil;

an amplifier device operable to receive an FM signal induced on the pick-up coil and provide the FM signal as an amplified FM signal;

an FM receiver operable to receive the amplified FM signal; and

a microcontroller in communication with the FM receiver and operable to determine a strength of the amplified FM signal, the microcontroller being further operable to output a tuning frequency to the tuning coil in order to adjust a resonant frequency of the ferrite antenna.

11. An antenna system according to claim 10, wherein:

the microcontroller is further operable to send a control signal to the FM receiver to adjust an operating frequency of the FM receiver to the adjusted resonant frequency.

12. An antenna system according to claim 10, further comprising:

a single varactor diode operable to receive the tuning coil from the microcontroller and adjust the resonant frequency of the ferrite antenna.

13. An antenna system according to claim 10, wherein:

the amplifier device includes a balanced differential amplifier.

14. An antenna system according to claim 10, wherein:

the at least one of the tuning and pick-up coils is formed of a copper tape.

15. A method of tuning a ferrite antenna over the FM frequency band, comprising the steps of:

receiving an induced voltage on a pick-up coil of the ferrite antenna and generating a frequency signal in response thereto;

amplifying the frequency signal and providing the amplified frequency signal to an FM receiver device;

determining a strength of the amplified frequency signal received by the FM receiver device; and

generating a tuning signal and applying the tuning signal to a tuning coil of the ferrite antenna, the tuning signal adjusting the resonant frequency of the ferrite antenna.

16. A method according to claim 15, further comprising:

adjusting an operating frequency of the FM receiver device to the adjusted resonant frequency.