1. Field of the Invention
The present invention relates to variable inductors, and more particularly, to a variable inductor suitable for various high frequency or microwave circuits.
2. Description of Related Art
In the family of electronic devices, the existence of variable inductors makes the fabrication of electronic circuits more flexible and convenient. Variable inductors have been widely used in electronic circuits having operating frequencies below hundreds of megahertz (MHz), such as the matching circuit, the tuning circuit, and so on. However, conventional variable inductors are incapable of acting as inductors at high operating frequencies, their frequency characteristics are awful, and the value of the quality factor Q is extremely low. Therefore, conventional variable inductors cannot be used for electronic circuits having high operating frequencies.
The present invention arose in the context of the above problems, and it is one object of the present invention to provide a variable inductor suitable for various high frequency or microwave circuits.
To achieve the above objective, in accordance with one aspect of the present invention, there is provided a variable inductor suitable for various high frequency or microwave circuits comprising a substrate, a fixed inductor, and signal terminals made of metal micro strip line on the substrate, wherein said variable inductor also comprises a conductive sheet disposed on the substrate for changing the geometry of the metal micro strip line corresponding to the effective inductance portion of the fixed inductor, and an insulator for changing the contact area between the conductive sheet and the metal micro strip line of the fixed inductor, the insulator being adjacent to the conductive sheet.
As a result, the variable inductor of the present invention is realized by disposing a conductive sheet on the existing fixed inductor. With the assistance of an insulator, the conductive sheet is capable of changing the geometry of the metal micro strip line corresponding to the effective inductance portion of the fixed inductor, and thereby, the inductance of a variable inductor being varied continuously is realized.
The variable inductor of the present invention provides the following advantages:
Preferred embodiments of the present invention will hereinafter be described in more detail with reference to the accompanying drawings.
With reference to FIGS. 1 though 4, a variable inductor in accordance with a first embodiment of the present invention comprises a substrate 14, a fixed inductor 12 and signal terminals 15 made of metal micro strip line disposed on the substrate, a conductive sheet 11 for changing the length of the metal micro strip line of the effective inductance portion of the fixed inductor, and an insulator 13 for changing the position of the conductive sheet 11.
In the present embodiment, the conductive sheet 11 is disposed on the top surface of the substrate 14, the bottom surface of the conductive sheet 11 is contacted with the substrate 14, while the top surface is connected to the insulator 13. Changing the position of the insulator 13 along the direction of force, as illustrated in
The fixed inductor 12 is a continuous parallel metal micro strip line, and the geometry and size of the conductive sheet 11 is capable of short-circuiting the metal micro strip line of the fixed inductor 12.
In order to ensure that the length of the metal micro strip line of the effective inductance portion of the fixed inductor 12 can be effectively changed, fixed blocks or splints (not shown) are installed at the both ends of the conductive sheet 11 so that the conductive sheet can be moved on a desired pathway. The insulator 13 can be fixed to the conductive sheet 11 by a gluing or a mechanical process in order to ensure the performance of repeatable movements.
In addition, the insulator 13 can also be disposed at the side of the conductive sheet 11.
With reference to
In order to ensure that the length of the metal micro strip line of the effective inductance portion of the fixed inductor 22 can be changed effectively, the insulator 23 can be extracted by rollers (not shown). One end of the insulator 23 is connected to one roller and the other end is connected to another roller by two insulating wires. By rotating one roller, the insulator 23 can be extracted gradually. When the roller at one end is being rotated, the insulator 23 is extracted, when the roller at the other end is being rotated in an opposite direction, the insulator 23 is drawn back in-between. Both the length and width of the insulator 23 can be greater than those of the conductive sheet 21, respectively. The gap between the two insulating wires can be greater than the width of the conductive sheet 21 to ensure that the conductive sheet 21 will not touch the insulating wires, and that the insulating wires clear at both ends the conductive sheet 21.
The top end of the conductive sheet 21 at the extracted end of the insulator 23 can be arranged at a small tilting angle so as to ensure that the insulator 23 can be drawn back conveniently.
Furthermore, an additional insulating layer can be disposed above the top surface of the conductive sheet 21, and a spring can be affixed to the top surface of the insulating layer the other end of the spring being affixed to an outer shell. Applying force onto the conductive sheet 21 through the spring ensures that the conductive sheet 21 is contacted effectively with the fixed inductor 22 when the insulator 23 is being extracted, and that the position of the conductive sheet 21 is kept unchanged. The conductive sheet 21, the insulating layer, and the spring can be combined through gluing or through a mechanical process.
In the variable inductor in accordance with the first and second embodiment of the present invention, the insulator is adjacent to the conductive sheet. With the assistance of the insulator, the contact area between the conductive sheet and the metal micro strip line of the fixed inductor can be changed. Therefore, the metal micro strip line of the fixed inductor is short circuited electrically, and thus the length of the metal micro strip line corresponding to effective inductance portion of the fixed inductor is shortened. In this way, the effective inductance of the fixed inductor is variably decreased so as to achieve the inductance of a variable inductor being varied continuously.
Furthermore, the impedances of the signal input and output terminals on the substrate can be designed to have a value such as 50 Ohm or 75 Ohm, as required. The width of the conductive sheet can be designed to be the same or similar to the width of the signal metal micro strip line.
With reference to
The substrate of the fixed inductor made of circular spiral metal micro strip line is configured with two layer substrate or multilayer substrates, wherein the connection between the central portion of the metal micro strip line of the fixed inductor and the signal output terminal is realized through the metal micro strip line of the middle layer substrate.
In the present embodiment, the conductive sheet 31 is disposed on the top surface of the substrate 34 and the top surface of the conductive sheet 31 is connected to the insulating forcing plate 33. By pressing the insulating forcing plate 33 along the direction of the force, as illustrated in
With reference to
With reference to
With reference to
With reference to
Furthermore, the insulator can be also disposed at the side of the conductive sheet 71.
With reference to
Supposing that the inductance of the fixed inductor made of single metal micro strip line on the substrate is L, when the insulating forcing plate disposed at the top or side of the conductive sheet is being forced, the metal micro strip line of the fixed inductor will come into contact with the conductive sheet so as to shorten the length of the metal micro strip line corresponding to the effective inductance portion of the fixed inductor, and thereby to decrease the inductance of the inductor. When the force is increased to a certain extent so as to contact the conductive sheet with the metal micro strip line of the fixed inductor completely, the metal micro strip line of the fixed inductor is nearly changed into a single metal micro strip line and its characteristics as an inductor are totally lost, thus decreasing the inductance to zero.
The basic principle of a variable inductor in accordance with the third through the eighth embodiments of the present invention is that a conductive sheet is disposed on a fixed inductor made of metal micro strip line on a substrate. One side (or one end) of the conductive sheet can be contacted with the metal micro strip line of the fixed inductor, and the other side (or the other end) is fixed to an insulating forcing plate. It is preferable that the fabrication of the geometry and the setting of the position of the conductive sheet keep the conductive sheet contacted with the fixed inductor along the direction of the length of the metal micro strip line of the fixed inductor, and enable to change the length of the metal micro strip line corresponding to the effective inductance portion of the fixed inductor.
By placing a force on the insulating forcing plate above or at the side of the conductive sheet so as to realize the geometrical change of the conductive sheet along the direction of the length of the metal micro strip line of the fixed inductor and to increase the contact area between the conductive sheet and the metal micro strip line, and to widen the width of the contact portion of the metal micro strip line, the inductance of the metal micro strip line in the contact area can be decreased. With the increase of the force on the insulating forcing plate, the relatively widened portion of the metal micro strip line of the fixed inductor will be increased. In this way, the inductance of the fixed inductor will be decreased accordingly, and the inductance of the inductor being varied continuously is realized.
For the variable inductor in accordance with the embodiments of the present invention, the variable range of the inductance is ΔL=L˜0, where the L is the inductance of the fixed inductor formed on the substrate.
With reference to
The insulator 103 is disposed between the metal micro strip line of the fixed inductor 102 and the conductive sheet 101, the position and geometry of the conductive sheet 101 is applicable to widen the width of metal micro strip line corresponding to the effective inductance portion of the fixed inductor 102 when the fixed inductor 102 is insulated from the conductive sheet 101. By extracting the insulator 103, the metal micro strip line of the fixed inductor 102 can be contacted with the conductive sheet 101 so that the effective width of metal micro strip line of the fixed inductor 102 is widened. In this way, the effective inductance of the fixed inductor 102 is decreased, and effectively a continuously-variable inductor is realized.
The force applied on the insulator of the present invention can be a mechanical force; a manual force; an external force produced by an automatic control process; a mechanical force; an electromagnetic force; a force produced by heat or temperature variations; a force produced by flowing or expanding or contracting of a liquid; or a force initiated by an optoelectronic excitation process.
The variable inductor in accordance with the present invention is suitable for variable frequency resonance loops, load change, matching and impedance change loops, and various control loops of high frequency or microwave circuits.
Number | Date | Country | Kind |
---|---|---|---|
200410027166.9 | May 2004 | CN | national |
This is a National Stage Application of International Patent Application No. PCT/CN 2005/000197 with an international filing date of Feb. 17, 2005, which is based on Chinese Patent Application No. 200410027166.9, filed May 10, 2004. The contents of both of these specifications are incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/CN05/00197 | 2/17/2005 | WO | 11/7/2006 |