RF field generator and detector

• US 4,725,780 A
• Filed: 10/18/1985
• Issued: 02/16/1988
• Est. Priority Date: 10/19/1984
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Fujimura, Satoshi, Yoda, Kiyoshi
• Primary Examiner(s): Levy, Stewart J.
• Assistant Examiner(s): Oldham, Scott M.
• Application Number:
  US06/789,040
• Time in Patent Office: 851 Days
• Field of Search: 324/307, 324/309, 324/318, 324/319, 324/320, 324/322, 335/299, 128/653, 333/219, 343/744, 343/859, 343/860
• US Class Current: 324/318
• CPC Class Codes: G01R 33/3628 Tuning/matching of the transmit/receive coil

Abstract

An RF field generator and detector comprising an RF coil having an inductance and at least one conductor which includes at least first and second separated parts arranged to form stray capacitance between them, capacitors for impedance matching which are connected to the RF coil, and a balanced-to-unbalanced transformer by which a balanced load composed of the RF coil and the capacitors is coupled to an unbalanced RF transmitter and receiver, the stray capacitance being adjusted thereby to equivalently reduce the inductance of the RF coil.

Claims

1. An RF field generator and detector comprising:

an RF coil having an inductance and at least one conductor including at least first and second separated parts arranged to form stray capacitance therebetween;

capacitors for impedance matching which are connected to said RF coil; and

a balanced-to-unbalanced transformer by which a balanced load comprising said RF coil and said capacitors is coupled to an unbalanced RF transmitter and receiver, the stray capacitance being adjusted to equivalently reduce the inductance of said RF coil.

2. An RF field generator and detector according to claim 1 wherein said RF coil comprises a saddle-shaped coil.

3. An RF field generator and detector according to claim 1 further comprising:

an electric insulator member positioned between said first and second separated parts, and

wherein said at least first and second separated parts comprise metal members.

4. An RF field generator and detector according to claim 1 wherein said balanced-to-unbalanced transformer comprises a transmission line which has an electrical length of 1/2 wavelength.

5. An RF field generator and detector according to claim 4 wherein said transmission line comprises a coaxial cable.

6. An RF field generator and detector according to claim 1 wherein said capacitors for impedance matching are arranged in a balanced form.

7. An RF field generator and detector comprising:

an RF coil having an inductance and at least one conductor including at least first and second separated parts arranged to form stray capacitance therebetween;

capacitors for impedance matching;

an impedance transformer which couples said RF coil and said capacitors; and

a balanced-to-unbalanced transformer by which a balanced load comprising said RF coil, said capacitors, and said impedance transformer is coupled to an unbalanced RF transmitter and receiver, the stray capacitance being adjusted to equivalently render an impedance of said RF coil capacitive.

8. An RF field generator and detector according to claim 7 wherein said impedance transformer comprises a transmission line which has an electrical length being at least 1/4 wavelength and less than 1/2 wavelength.

9. An RF field generator and detector comprising an RF coil having an inductance and at least one conductor including at least first and second separated parts arranged to form stray capacitance therebetween;

capacitors for impedance matching which are connected to said RF coil;

a balanced-to-unbalanced transformer by which a balanced load comprising said RF coil and said capacitors is coupled to an unbalanced RF transmitter and receiver; and

an impedance transformer which is interposed between said balanced-to-unbalanced transformer and connection terminals for the RF transmitter and receiver, the stray capacitance being adjusted to equivalently reduce the inductance of said RF coil.

10. An RF field generator and detector according to claim 9 wherein said RF coil comprises a saddle-shaped coil.

11. An RF field generator and detector according to claim 9 further comprising:

an electric insulator member positioned between said first and second separated parts, and wherein said at least first and second separated parts comprise metal members.

12. An RF field generator and detector according to claim 9 wherein said impedance transformer comprises a coaxial cable which has an electrical length substantially equal to 1/4 wavelength.

13. An RF field generator and detector according to claim 9 wherein said impedance transformer comprises a plurality of serially connected coaxial cables which have an electrical length substantially equal to 1/4 wavelength.

14. An RF field generator and detector according to claim 9 wherein said capacitors for impedance matching are arranged in a balanced form.

15. An RF field generator and detector according to claim 9 wherein said balanced-to-unbalanced transformer comprises a transmission line which has an electrical length of 1/2 wavelength.

16. An RF field generator and detector according to claim 15 wherein said transmission line comprises a coaxial cable.

17. An RF field generator and detector according to claim 9 wherein said balanced-to-unbalanced transformer comprises a Sperrtopf (wave trap) type transformer which has an electrical length of 1/4 wavelength.

18. An RF field generator and detector according to claim 9 wherein said balanced-to-unbalanced transformer comprises a branch conductor type transformer which has an electrical length of 1/4 wavelength.

19. An RF field generator and detector comprising:

an RF coil having an inductance and at least one conductor including at least first and second separated parts arranged to form stray capacitance therebetween;

capacitors for impedance matching;

a first impedance transformer which couples said RF coil and said capacitors;

a balanced-to-unbalanced transformer by which a balanced load comprising said RF coil, said capacitors, and said first impedance transformer is coupled to an unbalance RF transmitter and receiver;

and a second impedance transformer which is interposed between said balanced-to-unbalanced transformer and connection terminals for the RF transmitter and receiver, the stray capacitance being adjusted to equivalently render an impedance of said RF coil capacitive.

20. An RF field generator and detector according to claim 19 wherein said first impedance transformer comprises a transmission line which has an electrical length being at least 1/4 wavelength and less than 1/2 wavelength.

21. An RF field generator and detector according to claim 19 wherein said second impedance transformer comprises a coaxial cable which has an electrical length substantially equal to 1/4 wavelength.

22. An RF field generator and detector according to claim 19 wherein said second impedance transformer comprises a plurality of serially connected coaxial cables which have an electrical length substantially equal to 1/4 wavelength.

23. An RF field generator and detector according to claim 19 further comprising:

an electric insulator member positioned between said first and second separated parts, and

wherein said at least first and second separated parts comprise metal members.