KR20110041618A - Impedance matching circuit - Google Patents

Abstract

PURPOSE: An impedance matching circuit is provided to perform a selective operation in an inductance area and a capacitance area according to the switching states of switches, thereby matching impedance. CONSTITUTION: One terminal of a capacitor(C) and an inductor(L) is commonly connected to a first terminal. A first switch(SW1) is connected between the other terminal of the capacitor and the ground. A second switch(SW2) is connected to the other terminal of the capacitor and a second terminal. A third switch(SW3) is connected between the other terminal of the inductor and the ground. A fourth switch(SW4) is connected between the other terminal of the inductor and the second terminal. First to fourth switches are made of an MEMS(Micro Electro Mechanical Systems) switch or an RF(Radio Frequency) switch.

Description

Impedance matching circuit

The present invention relates to an impedance matching circuit.

In general, when two circuits are connected, such as between RF (Radio Frequency) circuits performing a predetermined operation, or between a diplexer and an antenna, return losses are generated by matching impedances between the two circuits. An impedance matching circuit is provided so as not to be prevented.

Various impedance matching circuits are known. However, the matching circuits are fixed to match impedance in the inductance region or the capacitance region.

Therefore, when connecting two circuits, a specific impedance matching circuit was newly developed and the two circuits were connected.

Therefore, an object of the present invention is to provide an impedance matching circuit for selectively matching impedance by operating in an inductance region and a capacitance region.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above may be clearly understood by those skilled in the art to which the present invention pertains. There will be.

An embodiment of the impedance matching circuit of the present invention includes a capacitor and an inductor having one terminal connected to the first terminal in common, a first switch connected between the other terminal of the capacitor and the ground, and the other terminal of the capacitor. A second switch connected between second terminals, a third switch connected between the other terminal of the inductor and ground, and a fourth switch connected between the other terminal of the inductor and the second terminal; do.

The first to fourth switches are MEMS (Micro Electro Mechanical Systems) switches or RF (Radio Frequency) switches.

In addition, the first to fourth switches are RF (Radio Frequency) switches.

The second and third switches are opened when the first and fourth switches are connected, and the second and third switches are connected when the first and fourth switches are opened.

According to another embodiment of the impedance matching circuit of the present invention, a capacitor and an inductor having one terminal commonly connected to the first terminal, a movable terminal connected to the other terminal of the capacitor, and one fixed terminal connected to the ground, and the other fixed terminal And an eleventh switch connected to a second terminal, and a twelfth switch having a movable terminal connected to the other terminal of the inductor, one fixed terminal connected to ground, and the other fixed terminal connected to the second terminal.

The eleventh and twelfth switches are MEMS (Micro Electro Mechanical Systems) switches or RF (Radio Frequency) switches.

In addition, the eleventh switch and the twelfth switch are RF (Radio Frequency) switches.

When the movable terminal of the eleventh switch is connected to one fixed terminal, the twelfth switch has the movable terminal connected to the other fixed terminal and the movable terminal of the eleventh switch is connected to the other fixed terminal. 12 The switch has a movable terminal connected to one fixed terminal.

According to the impedance matching circuit of the present invention, a capacitor is connected between the first terminal and the ground according to the switching state of the plurality of switches, and an inductor is connected between the first terminal and the second terminal to operate in the inductance region, or An inductor is connected between the first terminal and ground, and a capacitor is connected between the first terminal and the second terminal to operate in the capacitance region.

Therefore, the present invention can selectively operate in the inductance region or the capacitance region to match the impedance.

The following detailed description is only illustrative, and merely illustrates embodiments of the present invention. In addition, the principles and concepts of the present invention are provided for the purpose of explanation and most useful.

Accordingly, various forms that can be implemented by those of ordinary skill in the art, as well as not intended to provide a detailed structure beyond the basic understanding of the present invention through the drawings.

1 is a view showing the configuration of an embodiment of an impedance matching circuit of the present invention.

Here, reference numeral 100 denotes a first terminal, and reference numeral 110 denotes a second terminal.

For example, when two circuits are connected, an output terminal of the first circuit may be connected to the first terminal 100, and an input terminal of a second circuit may be connected to the second terminal 110. In addition, an output terminal of a second circuit may be connected to the first terminal 100, and an input terminal of a first circuit may be connected to the second terminal 110.

One terminal of the capacitor C and the inductor L is commonly connected to the first terminal 100.

The other terminals of the capacitor C and the inductor L are connected to the ground through a first RF switch SW1 and a third RF switch SW3, respectively.

In addition, the other terminals of the capacitor C and the inductor L are connected to the second terminal 110 through the second RF switch SW2 and the fourth RF switch SW4, respectively.

According to the present invention configured as described above, when the first and fourth RF switches SW1 and SW4 are connected, the second and third RF switches SW2 and SW3 are opened, and the first and fourth RF switches SW1 and SW4. Is open, the second and third RF switch (SW2, SW3) is connected so that one of the capacitor (C) and inductor (L) is connected between the first terminal 100 and the ground, The other element is connected between the first terminal 100 and the second terminal 110.

For example, when the first RF switch SW1 and the fourth RF switch SW4 are connected, and the second RF switch SW2 and the third RF switch SW3 are opened, the second RF switch SW1 and the fourth RF switch SW4 are opened as shown in FIG. 2A. The capacitor C is connected between the first terminal 100 and the ground, and the inductor L is connected in series between the first terminal 100 and the second terminal 110.

Then, the impedance matching circuit of the present invention operates in the upper hemisphere of the Smith chart, that is, the region of inductance, as shown in FIG. 3A, to match the impedances of the two circuits connected to the first terminal 100 and the second terminal 110. Done.

When the first RF switch SW1 and the fourth RF switch SW4 are opened, and the second RF switch SW2 and the third RF switch SW3 are connected to each other, as shown in FIG. An inductor L is connected between 100 and a ground, and a capacitor C is connected in series between the first terminal 100 and the second terminal 110.

Then, the impedance matching circuit of the present invention operates in the lower hemisphere of the Smith chart, that is, in the region of capacitance as shown in FIG. 3B to match the impedances of the two circuits connected to the first terminal 100 and the second terminal 110. Done.

3A and 3B illustrate impedance characteristics by taking a case where a capacitor C having a capacity of 5pF and an inductor L having an inductance of 10mH are used as an example.

The present invention is a variable type that operates in the inductance region or the capacitance region according to the operation of the first to fourth RF switches SW1 to SW4. Therefore, compared with the fixed impedance matching circuit, it is possible to greatly expand the section in which impedance matching is possible from any impedance.

4 is a diagram showing the configuration of another embodiment of the impedance matching circuit of the present invention. Referring to FIG. 4, another embodiment of the present invention uses two RF switches SW11 and SW12 having one movable terminal and two fixed terminals.

That is, according to another embodiment of the present invention, the movable terminal of the eleventh RF switch SW11 is connected to the other terminal of the capacitor C, and the fixed terminal a11 of the eleventh RF switch SW11 is connected to ground. The other fixed terminal b11 of the eleventh RF switch SW11 is connected to the second terminal 110.

A movable terminal of the twelfth RF switch SW12 is connected to the other terminal of the inductor L, one fixed terminal a12 of the twelfth RF switch SW12 is connected to ground, and a twelfth RF switch SW12. The other fixed terminal of b12 is connected to the second terminal 110.

According to another embodiment of the present invention configured as described above, the movable terminal of the eleventh RF switch SW11 is connected to one fixed terminal a11, and the movable terminal of the twelfth RF switch SW12 is connected to the other fixed terminal b12. In this case, the capacitor C is connected to the ground through the eleventh RF switch SW11, and the inductor L is connected to the second terminal 110 through the twelfth RF switch SW12.

Then, the impedance matching circuit of the present invention operates in the inductance region to match the impedances of the two circuits connected to the first terminal 100 and the second terminal 110.

When the movable terminal of the eleventh RF switch SW11 is connected to the other fixed terminal b11 and the movable terminal of the twelfth RF switch SW12 is connected to the fixed terminal a12 on one side, the capacitor C 11 is connected to the second terminal 110 through the RF switch (SW11), the inductor (L) is connected to the ground through the twelfth RF switch (SW12).

Then, the impedance matching circuit of the present invention operates in the capacitance region to match the impedances of the two circuits connected to the first terminal 100 and the second terminal 110.

In the present invention, the above-mentioned RF switches, that is, the first to fourth RF switches SW1 to SW4 and the eleventh and twelfth RF switches SW11 and SW12 have high Q values and low insertion loss. Micro Electro Mechanical Systems (MEMS) switches can be used.

When using the MEMS switch it is possible to minimize the parasitic components generated in the switch itself.

The present invention has been described in detail with reference to exemplary embodiments, but those skilled in the art to which the present invention pertains can make various modifications without departing from the scope of the present invention. Will understand.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

The present invention relates to an impedance matching circuit provided between two circuits such that reflection loss does not occur, and selectively operates in an inductance region or a capacitance region according to a switching state of a plurality of switches to match impedance.

1 is a view showing the configuration of an embodiment of an impedance matching circuit of the present invention;

2a and 2b are views for explaining the operation of the impedance matching circuit of the present invention;

3A and 3B are views for explaining an impedance matching section of the impedance matching circuit of the present invention; and

4 is a diagram showing the configuration of another embodiment of the impedance matching circuit of the present invention.

Claims (8)

A capacitor and an inductor having one terminal connected to the first terminal in common; A first switch connected between the other terminal of the capacitor and a ground; A second switch connected between the other terminal of the capacitor and the second terminal; A third switch connected between the other terminal of the inductor and a ground; And And a fourth switch connected between the other terminal of the inductor and the second terminal. The method of claim 1, wherein the first to fourth switches; Impedance matching circuit that is a MEMS (Micro Electro Mechanical Systems) switch or an RF (Radio Frequency) switch. The method of claim 1, wherein the first to fourth switches; Impedance matching circuit, an RF (Radio Frequency) switch. The method of claim 1, And the second and third switches are opened when the first and fourth switches are connected, and the second and third switches are connected when the first and fourth switches are opened. A capacitor and an inductor having one terminal connected to the first terminal in common; An eleventh switch to which a movable terminal is connected to the other terminal of the capacitor, one fixed terminal is connected to the ground, and the other fixed terminal is connected to the second terminal; And And a twelfth switch having a movable terminal connected to the other terminal of the inductor, one fixed terminal connected to ground, and the other fixed terminal connected to the second terminal. The apparatus of claim 5, wherein the eleventh switch and the twelfth switch; Impedance matching circuit that is a MEMS (Micro Electro Mechanical Systems) switch or an RF (Radio Frequency) switch. The apparatus of claim 5, wherein the eleventh switch and the twelfth switch; Impedance matching circuit, an RF (Radio Frequency) switch. The method of claim 5, When the movable terminal of the eleventh switch is connected to one fixed terminal, the twelfth switch is the twelfth switch when the movable terminal is connected to the other fixed terminal and the movable terminal of the eleventh switch is connected to the other fixed terminal. A switch is an impedance matching circuit in which a movable terminal is connected to one fixed terminal.

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