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United States Patent 
[li] 4,095,198  June 13,1978
 IMPEDANCE-MATCHING NETWORK
 Inventor: Thomas J. Kirby, Hillsboro, N.H.
 Assignee: GTE Sylvania Incorporated, Stamford, Conn.
 Appl. No.: 763,820
 Filed: Jan. 31,1977
 Int.Cl.2 H03H7/38
 U.S. CI 333/32; 323/76;
 Field of Search 323/74, 76, 80;
333/17 M, 32; 334/47, 65; 343/860, 861
 References Cited
U.S. PATENT DOCUMENTS
3,509,500 4/1970 McNair et al 333/17 M
3,794,941 2/1974 Templin 333/17 M
3,906,405 9/1975 Kommrusch 333/32 X
3,995,237 11/1976 Brunner 333/32 X
Neumann & Port, "Programmable Antenna-Tuning Unit & its Use with Shortwave Transmitter sk 1/39",
News from Rohde & Schwarz, No. 46, vol. 11,1971, pp. 21-24.
Primary Examiner—A. D. Pellinen
Attorney, Agent, or Firm—Peter Xiarhos
An impedance-matching network for impedancematching a generator to a load over a wide range of frequencies and impedances. The network includes a first pair of busses across which a plurality of capacitors may be selectively connected to achieve an overall desired value of capacitance for the network, and a second pair of busses across which a plurality of inductors may be selectively connected to achieve an overall desired value of inductance for the network. The network may be controlled so that the capacitance and inductance elements may be arranged with respect to each other and the generator and load in any one of four possible L-type configurations or topologies.
13 Claims, 9 Drawing Figures
Mi i w11 m m w w w i i w www m mm
BACKGROUND OF THE INVENTION 5
The present invention relates to an impedance-matching network and, more particularly, to an impedancematching network which can be rapidly, electronically controlled to any one of several possible L-type configurations for impedance-matching a generator to a load 1° over a wide range of frequencies.
Impedance-matching networks for impedancematching sources to loads are generally well known to those skilled in the art. One well-known type of impedance-matching network includes a plurality of discrete 15 circuits corresponding to a like plurality of frequencies and impedances to which a generator source impedance is to be matched. While this type of impedance-matching network is generally useful, it is limited to load matching transformations over a relatively narrow 20 matched bandwidth. Thus, as the possible operational range of the included frequencies or terminating loads increases, the required number of discrete circuits rises rapidly to a prohibitively large number. ^
Another well-known type of impedance-matching arrangement includes a rotary or tapped coil which is coupled with a continuously variable capacitor to allow a mechanical adjustment of the reactive elements for permitting the matching of a generator source impe- 3Q dance to a range of terminating impedances. The above type of arrangement has the disadvantage in that the adjustment thereof, being manual and mechanical in nature, is quite slow due the inherent mechanical time constants of the arrangement. A very rapid reconfigura- j5 tion of the arrangement so as to be used with different load impedances is not achievable since the mechanical components must vary through an initial setting to other settings. This limitation restricts the use of such an arrangement to quasistationary environments where, 40 after an initial adjustment, the terminating impedance and operating frequency remains fixed for a relatively long period of time.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention an impedance-matching network is provided which overcomes the types of prior art problems and difficulties as mentioned hereinabove. The impedance-matching network in accordance with the invention is employed to impe- 50 dance match a source, such as a generator, to a load and includes a first plurality of reactive elements, for example, capacitors, and a second plurality of reactive elements, for example, inductors. A first control means is provided which operates selectively to connect one or 55 more of the first plurality of reactive elements across a first pair of busses, thereby to achieve an effective first reactance across the first pair of busses, and also to selectively connect one or more of the second plurality of reactance elements across the second pair of busses, 60 thereby to achieve an effective second reactance across the second pair of busses. The impedance-matching network further includes a second control means which is operative to interconnect a source to be impedancematched with a load with the first and second pairs of 65 busses having the effective reactances thereacross in any one of a plurality of different possible circuit configurations or topologies.
BRIEF DESCRIPTION OF THE DRAWING
Various objects, features and advantages of an impedance-matching network in accordance with the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing in which:
FIG. 1 is a schematic diagram of an impedancematching network in accordance with the invention;
FIGS. 2-5 are schematic representations illustrating four possible L-type configurations or topologies for the impedance-matching network of FIG. 1; and
FIGS. 6-9 are schematic representations corresponding to FIGS. 5-8, respectively, and illustrating conditions of elements of the impedance-matching network for the four L-type configurations as shown in FIGS. 5-8.
DETAILED DESCRIPTION OF THE
Referring now to FIG. 1, there is shown an impedance-matching network 1 in accordance with the present invention. The impedance-matching network 1 is connected between an input terminal 3 and an output terminal 5 and is adapted to impedance match a source such as a generator (not shown) connected to the input terminal 3 with a load (also not shown) connected to the output terminal 5. As will be described hereinafter, the impedance-matching network 1 may be controlled, specifically, by means of voltages established at a plurality of control terminals J1-J20, so as to have any one of four possible "L" configurations, as shown in FIGS. 5-8, and to have any one of several possible selected capacitive and inductive reactance values.
The impedance-matching network 1 as shown in FIG. 1 generally comprises a plurality of relays KR1-KR20 connected to the above-mentioned control terminals J1-J20, a plurality of capacitors C1-C8, and a plurality of inductors L1-L8. As will be explained more fully hereinafter, the particular relays KR1-KR8 are employed to establish a particular capacitive reactance for the network 1, the relays K13-K20 are employed to establish a particular inductive reactance for the network 1, and the relays KR9-KR12 are employed to establish the particular topology or configuration for the network 1, that is, to establish a particular one of the four possible L-type configurations as shown in FIGS. 2-5.
Each of the relays KR1-KR20, which may be of the vacuum type, includes a winding 7 which, when energized, causes a corresponding one of a plurality of movable contacts krl-krlQ to move from a first, "open" position to a second, "closed" position. Diodes 9 are connected across the windings 7 for damping transients during energization of the windings 7. When one of the contacts krl-krS is operated to its "closed" position in accordance with the invention, by virtue of the energization of the relay winding 7 of the corresponding one of the relays KR1-KR8, a corresponding one of the capacitors C1-C8 in series with the contact is caused to be connected across a first pair of busses BUI and BU2. Similarly, when one of the contacts krl3-krl9 is operated to its "closed" position by virtue of the energization of the relay winding 7 of the corresponding one of the relays KR13-KR20, a corresponding one of the inductors L1-L8 in series with the contact is caused to be connected across a second pair of busses BU3 and BU4. Thus, by the selective energization of the wind