Method for automatically matching a radio frequency transmitter to an antenna

• US 4,201,960 A
• Filed: 05/24/1978
• Issued: 05/06/1980
• Est. Priority Date: 05/24/1978
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Tice, Lee D., Skutta, Frank R.
• Primary Examiner(s): Gensler, Paul L.
• Application Number:
  US05/909,155
• Time in Patent Office: 713 Days
• Field of Search: 333/17 M, 325/174, 325/177
• US Class Current: 333/17.3
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance
• CPC Class Codes: H03J 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H

Abstract

A plurality of series inductors and shunt capacitors are provided between a radio transmitter and an antenna. The inductors and capacitors are arranged in binary increments and are inserted in, or withdrawn from the circuit via provided reed relays. A microprocessor activates the relays in one of several modes until the required degree of match is provided. The status of the relays is stored in provided memory such that upon tuning of the transmitter to the same channel a proper match condition can be established without resort to the matching program.

Claims

1. A method for matching the nominal real impedance of a transmitter to an antenna comprising the steps of:

(a) providing a first terminal adapted for connection to said transmitter;

(b) providing a second terminal adapted for connection to said antenna;

(c) providing a variable series inductance coupled between said first and second terminals;

(d) providing a variable shunt capacitance coupled to a predetermined one of said first and second terminals;

(e) predeterminedly controlling said inductance and capacitance in a first mode such that the impedance at said first terminal is substantially real having a value less than said nominal real impedance; and

(f) predeterminedly varying said inductance and capacitance in a second mode to increase the real part of the impedance at said first terminal until it is within a predetermined range from said nominal impedance.

2. The method of claim 1 wherein step (c) further comprises the steps of:

(i) providing a plurality of predetermined value, series coupled inductors coupled between said first and second terminals; and

(ii) providing a means to selectively shunt said inductors.

3. The method of claim 1 wherein step (d) further comprises the steps of:

(i) providing a plurality of predetermined value capacitors;

(ii) providing a means to selectively couple said capacitors between a predetermined one of said first and second terminals and a reference potential.

4. The method of claim 1 wherein step (e) further comprises the steps of:

(i) providing a phase meter means;

(ii) coupling said phase meter means to said first terminal; and

(iii) utilizing said phase meter to determine that inductance/capacitance condition at which the impedance at said first terminal is substantially real.

5. The method of claim 1 wherein step (f) further comprises the steps of:

(i) providing a standing wave ratio meter means;

(ii) coupling said standing wave ratio meter to said first terminal; and

(iii) utilizing said standing wave ratio meter to determine that inductance/capacitance condition at which the impedance at said first terminal is within a predetermined range from said nominal impedance.

6. The method of claim 4 wherein step (f) further comprises the steps of:

(i) providing a standing wave ratio meter means;

(ii) coupling said standing wave ratio meter to said first terminal; and

(iii) utilizing said standing wave ratio meter to determine that inductance/capacitance condition at which the real part of the impedance at said first terminal is within a predetermined range from said nominal impedance.

7. The method of claim 1 wherein the antenna is inductive and wherein step (e) further comprises the steps of:

(i) coupling sufficient shunt capacitance to said second terminal such that the impedance at the first terminal has a real part less than said nominal impedance and a capacitive reactance;

(ii) predeterminedly increasing said series inductance until the impedance at the first terminal becomes inductive with a real part being less than the real part of said nominal impedance.

8. The method of claim 7 wherein step (e) further comprises the step of:

(iii) predeterminedly decreasing said series inductance by relatively small amounts until the impedance at said first terminal is capacitive.

9. The method of claim 7 wherein step (e) further comprising the steps of:

(iii) predeterminedly decreasing said series inductance by relatively small amounts until the impedance at said first terminal is capacitive; and

(iv) predeterminedly increasing said series inductance by smaller yet amounts until the impedance at said first terminal is inductive.

10. The method of claim 8 wherein step (f) further comprises the steps of:

(i) predeterminedly increasing the series inductance until the impedance at the first terminal is inductive;

(ii) predeterminedly decreasing the shunt capacitance at said second terminal until the impedance at the first terminal is capacitive; and

(iii) repeating steps (i) and (ii) above until the impedance at the first terminal is within said predetermined range.

11. The method of claim 9 wherein step (f) further comprises the steps of:

(i) predeterminedly increasing the series inductance until the impedance at the first terminal is inductive;

(ii) predeterminedly decreasing the shunt capacitance at said second terminal until the impedance at the first terminal is capacitive; and

(iii) repeating steps (i) and (ii) above until the impedance at the first terminal is within said predetermined range.

12. The method of claim 7 wherein step (c) further comprises the steps of:

(i) providing a plurality of N predetermined value, series coupled inductors coupled between said first and second terminals, said N inductors having values increasing in binary increments, L₁ to L_N ; and

(ii) providing a means to selectively shunt said inductors.

13. The method of claim 12 wherein step (e) part (ii) further comprises the step of:

increasing said series inductance according to the following sequence;

L₁, L₂, L₁ +L₂, L₃, L₃ +L₂, L₃ +L₂ +L₁, L₄, . . . until the impedance at the first terminal becomes inductive with a real part being less than the real part of said nominal impedance.

14. The method of claim 8 wherein step (e) part (ii) further comprises the step of:

increasing said series inductance according to the following sequence;

L₁, L₂, L₁ +L₂, L₃, L₃ +L₂, L₃ +L₂ +L₁, L₄, . . . until the impedance at the first real part being less than the real part of said nominal impedance.

15. The method of claim 14 wherein step (e) part (iii) further comprises the step of:

decreasing said series inductance from its value established in step (e), part (ii) by shunting out that inductor L_k whose value made the impedance at the first terminal inductive and successively activating those inductors of decreasing incremental binary value, L_k-1, L_k-2 . . . , until the impedance at said first terminal is capacitive.

16. The method of claim 10 wherein step (c) further comprises the step of:

(i) providing a plurality of N predetermined value, series coupled inductors coupled between said first and second terminals, said N inductors having values increasing in binary increments, L₁ to L_N ;

(ii) providing a means to selectively shunt said inductors.

17. The method of claim 16 wherein step (d) further comprises the steps of:

(i) providing a plurality of M predetermined value capacitors, said capacitors having increasing values C₁ to C_M, in binary increments;

(ii) providing a means to selectively couple said capacitors between said output terminal and a reference potential.

18. The method of claim 17 wherein step (f) part (i) comprises incrementing said inductors according to a binary sequence and wherein step f part (ii) comprises decrementing the shunt capacitor according to a binary sequence.

19. The method of claim 18 wherein step (e) further comprises the steps of:

(iv) providing a phase meter means;

(v) coupling said phase meter means to said first terminal; and

(vi) utilizing said phase meter to determine that inductance/capacitance condition at which the impedance at said first terminal is substantially real.

20. The method of claim 18 wherein step (f) further comprises the steps of:

(iv) providing a standing wave ratio meter means;

(v) coupling said standing wave ratio meter to said first terminal; and

(vi) utilizing said standing wave ratio meter to determine that inductance/capacitance condition at which the real part of the impedance at said first terminal is within a predetermined range from said nominal impedance.

21. The method of claim 19 wherein step (f) further comprises the steps of:

(iv) providing a standing wave ratio meter means;

(v) coupling said standing wave ratio meter to said first terminal; and

(vi) utilizing said standing wave ratio meter to determine that inductance/capacitance condition at which the real part of the impedance at said first terminal is within a predetermined range from said nominal impedance.

22. The method of claim 1 wherein the antenna is capacitive and wherein step (e) comprises the steps of:

(i) predeterminedly increasing the series inductance until the impedance at the first terminal is inductive having a real part less than said nominal impedance;

(ii) predeterminedly increasing the shunt capacitance coupled to said first terminal until the impedance thereat is slightly capacitive.

23. The method of claim 22 wherein step (f) further comprises the steps of:

(i) providing a plurality of capacitors of predetermined values for forming said variable shunt capacitance;

(ii) decoupling all shunt capacitors from said first terminal;

(iii) predeterminedly incrementing the series inductance;

(iv) predeterminedly increasing the shunt capacitance coupled to said first terminal until the impedance thereat is slightly capacitive;

(v) repeating steps (i), (ii) and (iii) until the real part of the impedance at said first terminal is within said predetermined range from said nominal impedance.

24. The method of claim 22 wherein step (c) further comprises the steps of:

(i) providing a plurality of N predetermined value, series coupled inductors coupled between said first and second terminals, said inductors having increasing values, L₁ to L_N, in binary increments; and

(ii) providing a means to selectively shunt said inductors.

25. The method of claim 24 wherein step (e) part (i) further comprises the step of:

increasing said series inductance according to the following sequence;

L₁, L₂, L₁ +L₂, L₃, L₃ +L₂, L₃ +L₂ +L₁, L₄ . . . until the impedance at the first terminal becomes inductive.

26. The method of claim 25 wherein step (e) part (i) further comprises the step of:

decreasing said series inductance from the value established in step (e) part (i) by shunting out that inductor L_k whose value made the impedance at the first terminal inductive and successively activating those inductors of decreasing incremental binary value, L_k-1, L_k-2, . . . , until the impedance at said first terminal is capacitive.

27. The method of claim 25 wherein step (d) further comprises the steps of:

(i) providing a plurality of M predetermined value capacitors, said capacitors having increasing values, C₁ to C_M, in binary increments; and

(ii) providing a means to selectively couple said capacitors between said input terminal and a reference potential.

28. The method of claim 27 wherein step (e) part (ii) further comprises the step of:

sequentially activating increasing value shunt capacitors until the impedance at said first terminal is capacitive and then alternately decreasing and increasing said shunt capacitance by incrementally smaller amounts until the impedance at said first terminal has a relatively small capacitive reactance.

29. The method of claim 28 wherein step (f) further comprises the steps of:

(i) decoupling all shunt capacitors from said first terminal;

(ii) predeterminedly incrementing the series inductance by one binary count;

(iii) predeterminedly incrementing the shunt capacitance coupled to the first terminal in accordance with step (e) part (ii);

(iv) repeating steps (i), (ii) and (iii) until the real part of the impedance at said first terminal is within a predetermined range from said nominal value.

30. The method of claim 29 wherein step (e) further comprises the steps of:

(i) providing a phase meter means;

(ii) coupling said phase meter means to said first terminal; and

(iii) utilizng said phase meter to determine that inductance/capacitance condition at which the impedance at said first terminal is substantially real.

31. The method of claim 29 wherein step (f) further comprises the steps of:

(iv) providing a standing wave ratio meter means;

(v) coupling said standing wave ratio meter to said first terminal; and

(vi) utilizing said standing wave ratio meter to determine that inductance/capacitance condition at which the real part of the impedance at said first terminal is within a predetermined range from said nominal impedance.

32. The method of claim 29 wherein step (f) further comprises the steps of:

(iv) providing a standing wave ratio meter means;

(v) coupling said standing wave ratio meter to said first terminal; and

(vi) utilizing said standing wave ratio meter to determine that inductance/capacitance condition at which the real part of the impedance at said first terminal is within a predetermined range from said nominal impedance.

33. The method of claim 18 wherein said transmitter is operable on a plurality of channels with at least two channels requiring different matching characteristics comprising the further steps of:

(i) storing in memory the series inductance/shunt capacitance settings which optimize antenna matching for a given channel; and

(ii) recalling from memory those stored settings and re-establishing said optimized antenna matching corresponding to the transmitter being operated on said channel.

34. The method of claim 29 wherein said transmitter is operable on a plurality of channels with at least two channels requiring different matching characteristics comprising the further steps of:

(i) storing in memory the series inductance/shunt capacitance settings which optimize antenna matching for a given channel; and

(ii) recalling from memory those stored settings and re-establishing said optimized antenna matching corresponding to the transmitter being operated on said channel.