KR100541078B1 - Strip-line for increasing impeadance without thickness increasing - Google Patents

Abstract

The present invention is to provide a stripline that is easy to adjust impedance that can satisfy the impedance characteristics required by the circuit by simply increasing the characteristic impedance without increasing the size.

The stripline according to the present invention includes a dielectric having a thickness B formed of a material having a dielectric constant of ε _r , a signal line pattern having a length of λ / 4 for a predetermined wavelength formed inside the dielectric, and a top surface of the dielectric. A part of the first ground pattern or the second ground pattern at a position opposite to the signal line pattern on the first ground pattern formed, the second ground pattern formed on the lower surface of the dielectric, and the upper or lower surface of the dielectric; It consists of a ground removing region formed by removing the, it is possible to easily adjust the characteristic impedance of the strip line by adjusting only the area of the ground removing region.

Stripline, Antenna Switch, LTCC, Stacked, Dielectric, Ground Pattern

Description

STRIP-LINE FOR INCREASING IMPEADANCE WITHOUT THICKNESS INCREASING}             

1 is a circuit diagram illustrating a basic circuit of a general antenna switch.

2 is an exploded perspective view showing a laminated structure of an antenna switch.

3 is a perspective view showing the structure of a conventional λ / 4 stripline.

4 is a perspective view showing the structure of the λ / 4 stripline according to the present invention.

FIG. 5A is a side cross-sectional view of the λ / 4 stripline according to the present invention, and FIG. 5B is a top view of the λ / 4 stripline according to the present invention.

6 is an equivalent view of the λ / 4 stripline according to the present invention.

7 is a graph showing a change relationship between the length of the ground removing region and the characteristic impedance in the lambda / 4 stripline according to the present invention.

Explanation of symbols on the main parts of the drawings

40: stripline

41: dielectric

42: signal line pattern

43,44: 1st, 2nd ground pattern

45: ground removal area

The present invention relates to a λ / 4 stripline used as a transmission line in an electric circuit, and more particularly, impedance control to satisfy the impedance characteristic required by the circuit can be easily achieved by increasing the characteristic impedance without increasing the size. To an easy stripline.

Transmission line is a conductive system consisting of conductors and utilizing the propagation of waves due to the electrical parameters (resistance, inductance, conductance, capacitance per unit length) distributed between the conductor itself and each other. Often used in circuits, their characteristics are represented by characteristic impedances and propagation constants.

As a typical transmission line, a pair of spiral wires and two copper wires, which are constructed in the air using insulators of hard copper wires or iron wires, are used as lead or plastic. Coated flat pair cable, coaxial cable made of inner conductor made of coaxial with outer conductor, waveguide made of copper and propagating through the inside. There is a microstrip formed by printing signal lines on a substrate, and in a stacked device, there is a stripline having a structure in which a ground layer is formed above and below the signal line.

Since the microstrip is grounded only below the signal line, the microstrip cannot be transmitted in the full TEM mode and the signal is fringed into the air, causing unnecessary coupling problems and loss problems. Since the stripline has the same ground plane above and below the signal line, the field is vertically distributed exactly above and below, minimizing the fringing field and transmitting in near-perfect TEM mode. In addition, since the stripline has a ground plate above and below the signal line, the stripline is shielded from the outside by itself, which is a great advantage.

Thus, striplines are often used when you want to implement a full TEM mode or when you want to handle large power signals rather than microstrips.

In general, the microstrip may be simply expressed as a strip or stripline for convenience of terminology, but the following stripline refers to a structure in which a ground plate is formed above and below the signal line.

FIG. 1 is an example of an electric circuit constructed using a transmission line, and illustrates an antenna switch for selectively connecting an antenna to a transmission circuit and a reception circuit. In the antenna switch, the transmission line L is a wavelength of a received signal. It has a length of λ / 4 with respect to λ, and connects the antenna terminal ANT and the receiving terminal RX, and transmits the received signal to the receiving terminal RX while transmitting the received signal to the receiving terminal RX. Performs a function of preventing transmission to the receiving end (RX).

In addition, according to the trend of miniaturization and weight reduction, such an antenna switch is formed in a laminated structure as shown in FIG. 2.

In the stacked structure diagram of FIG. 2, the portion corresponding to the transmission line L is a strip line 20, the strip line 20 is a signal line 22a having a length of λ / 4, and the signal line 22a is printed. Dielectric layer 22 and ground patterns 21 and 23 formed above and below the signal line 22a. Here, the stripline 20 of the antenna switch is required to have an electrical length of 90 ° and a characteristic impedance of 50 Ω at an operating frequency.

3 is an enlarged perspective view of only the strip line 20, wherein the width of the signal line 22a is W and the length is L, and the distance between the first and second ground patterns 21 and 23, that is, the dielectric 22. When the thickness of) is B and the permittivity is ε _r , the characteristic impedance Z ₀ of the stripline is expressed by Equation 1 below.

이다.In Equation 1,

to be.

That is, the characteristic impedance of the stripline 20 is inversely proportional to the dielectric constant ε _r of the dielectric 22 and the width W of the signal line 22a and is proportional to the thickness B of the dielectric 22.

Therefore, in order to increase the characteristic impedance of the stripline 20, it is necessary to increase the layer thickness of the dielectric 22, reduce the line width of the signal line 22a, or reduce the dielectric constant of the dielectric 22.

By the way, in the case of a device implemented with a stacked circuit board as shown in FIG. 2, components, for example, a diode, a saw filter, and a MLCC, are stacked on a substrate formed by stacking a plurality of sheets printed with a pattern according to the stacking order. The back is mounted and the case is completed.

In addition, according to the recent miniaturization and weight reduction trend, the overall size of components is decreasing. For example, in the case of the front end module connected to the antenna stage including the antenna switch as described above, the overall thickness of the final assembly is increased. Usually it should be within 2.0mm. Therefore, in consideration of the size of the component mounted on the laminated substrate, only the thickness of the laminated substrate should be within 0.85 mm. Within this limited thickness, the thickness B of the strip line 20 is determined by comprehensively considering the number and interlayer spacing of other patterns such as inductors and capacitors. Due to the thickness limitation of the entire substrate as described above, there is a limit to increasing the dielectric layer thickness B of the stripline 20.

In addition, in the case of the line width of the signal line 22a of the strip line 20, when the line width is reduced to 0.1 mm or less, defects such as a broken line or a constant line width are generated, which is a limit in reducing the line width. There is.

In addition, the change in permittivity of the dielectric layer 22 is a design and process problem, and in order to obtain a capacitor of the same capacity while reducing the permittivity of the entire stacked substrate including the stripline, a larger electrode area is required than when the permittivity is large. As a result, decreasing the permittivity makes it impossible to miniaturize. In addition, if only the dielectric layer 22 of the stripline 20 uses a dielectric constant having a small dielectric constant to increase the measurement impedance, it is difficult to change the dielectric constant because warpage occurs in the substrate itself due to a difference in shrinkage between the different layers.

Therefore, in the case of the antenna switching element, the dielectric constant ε _r of the substrate is typically 7, the layer thickness B of the strip line is about 0.24 mm, and the line width of the signal line 22a is 0.1 mm or more, and according to these conditions, the strip line The characteristic impedance of is up to 30 ~ 35Ω, which is less than the required 50Ω. In addition, the reduction of the characteristic impedance of the stripline results in the deterioration of the product.

This problem will be exacerbated as parts become thinner, more complex and more versatile.

The present invention has been proposed to solve the above-mentioned conventional problems, and its object is to provide a stripline that is easy to adjust the impedance which can easily increase the characteristic impedance without increasing the size to satisfy the impedance characteristic required by the circuit. To provide.

The present invention provides a structural means for achieving the above object, a dielectric layer consisting of a thickness of B with a dielectric constant of ε _r ; A signal line having a length of λ / 4 for a predetermined wavelength formed in the dielectric layer; A first ground pattern formed on an upper surface of the dielectric layer; A second ground pattern formed on the bottom surface of the dielectric layer; And a ground removing region formed by removing a portion of the first ground pattern or the second ground pattern at a position opposite to the signal line pattern on the top surface or the bottom surface of the dielectric layer, and comparing the ground to the total length of the signal line pattern. Characteristic impedance is adjusted by adjusting the area of the ground removing region so that the ratio of the pattern length of the portion facing the removing region is 1/2 or less.

In addition, the stripline according to the present invention can increase the characteristic impedance by adjusting the ratio of the signal line length of the portion facing the ground removing region to the total length of the signal line pattern.

Hereinafter, the configuration and operation of the stripline according to the present invention with reference to the accompanying drawings.

4 is a perspective view showing the structure of the stripline according to the present invention, wherein the stripline 40 is formed of a dielectric material 41 having a thickness B of a dielectric constant ε _r and formed inside the dielectric 41 and in operation signals. A signal line pattern 42 having a length of λ / 4 with respect to a wavelength of?, A first ground pattern 43 formed on an upper surface of the dielectric 41 parallel to the signal line pattern 42, and a thickness of the dielectric 41 The second ground pattern 44 formed on the lower surface of the first ground pattern 43 to face the first line pattern 43 and the electrode at a position opposite to the signal line pattern 42 are removed by a predetermined area. Consisting of a ground removal area 45.

FIG. 5A is a cross-sectional view taken along the line AA ′ of the strip line shown in FIG. 4, wherein the signal line pattern 42 is positioned between the first ground pattern 43 and the second ground pattern 44. The ground removing region 45 is positioned on the first ground pattern 43 at the vertical position of 42.

The ground removing region 45 faces a portion of the signal line pattern 42 having a length L, as shown in the stripline top projection view of FIG.

Let's look at the characteristic impedance of the stripline of the above structure.

As described above in Equation 1, the characteristic impedance of the stripline is proportional to the distance B between the upper and lower ground patterns, and is inversely proportional to the signal line width W and the dielectric constant ε _r .

By the way, in the case of the signal line pattern 42, the conditions of the signal line width W and the dielectric constant epsilon _r are constant, but the value of the distance B changes due to the ground removing region 45.

Since the ground pattern is removed from the pattern portion of the signal line pattern 42 located in the vertical direction in the ground removing region 45 and is not shielded, the distance B becomes large in the signal pattern region of the portion. For example, as shown in (a) of FIG. 5, if the dielectric layer having a thickness T is positioned on the first ground pattern 43 of the stripline 40 having the same structure as the present invention, the ground removing region ( At 45), the signal line pattern 42 has a distance of "B + T". At this time, the remaining portion of the signal line pattern 42 has a condition of the distance "B". Therefore, the characteristic impedance of the portion of the signal line pattern 42 opposite to the portion of the ground removing region 45 becomes larger than that of other portions of the signal line pattern 42.

As a result, the stripline 40 shown in FIG. 4 becomes a line showing a stepwise characteristic impedance as shown in FIG.

이 되어, 특성임피던스 Z₀₁보다 크고, 특성임피던스 Z₀₂ 보다 작게 된다.The characteristic impedance Z ₀₂ is greater than the characteristic impedance Z ₀₁ when the characteristic impedance of the portion facing the ground removing region 45 is Z ₀₂ and the characteristic impedance of the remaining portion is Z ₀₁ . In addition, the total characteristic impedance Z ₀ of the stripline 40 is

This becomes larger than the characteristic impedance Z ₀₁ and becomes smaller than the characteristic impedance Z ₀₂ .

From this result, it can be seen that it is possible to increase the overall characteristic impedance of the stripline by increasing the area of the signal line pattern facing the ground removing region 45.

Next, in the stripline of the structure according to the present invention, the relationship between the area of the ground removing region 45 and the characteristic impedance of the stripline 40 will be described with reference to the experimental example.

In FIG. 5B, the width of the ground removing region 45 is referred to as W _S , and the length is referred to as L _S.

In the present experiment, the ground removing region 45 is fixed while the distance B between the first and second ground patterns 43 and 44, the dielectric constant ε _r of the dielectric 41, and the line width W of the signal line pattern 42 are fixed. The change in characteristic impedance was examined by changing the area S of). At this time, the change of the area S of the ground removing region 45 is made constant by the width W _s parallel to the line width of the signal line pattern 42, and by changing the length L _S in the same direction as the length direction of the signal line pattern 42. Is done.

The dimensions of each part of the stripline used in this experiment are shown in Table 1 below.

B T W L W _S S 0.24 mm 0.5mm 0.1mm 28 mm 0.2mm Ws × L _S

The characteristic impedance was measured while changing the length L _S of the ground removing region in the stripline of the present invention having the conditions as described above and Table 1, and the results shown in Table 2 were measured.

L _S [mm] 0 1.42 4.26 7.1 9.94 12.78 15.62 18.46 S [mm ² ] 0 0.28 0.84 1.4 1.96 2.52 3.08 3.64 L _S / L 0 0.05 (= 1/20) 0.15 (= 3/20) 0.25 (= 5/20) 0.35 (= 7/20) 0.45 (= 9/20) 0.55 (= 11/20) 0.65 (= 13/20) _ Characteristic impedance [Ω] 35.3 36.5 37 39.8 42.8 43.8 44.0 44.5

From the measurement results shown in Table 2, the strip line 40 increases as the length L _S of the ground removing region 45 increases, that is, as the area of the signal line pattern 42 facing the ground removing region 45 increases. It can be seen that the characteristic impedance of is increased.

At this time, the length L _S , that is, L _s / L of the ground removing region 45 with respect to the entire length L of the signal line pattern 42 is set to an impedance of 0.5 or less.

Because, as shown in the results shown in Table 2, the impedance increase reaches a limit from the point where L _s / L is close to 0.5, and the signal line pattern 42 by the ground removing region 45 When considering the interference between different patterns, the effect of the interference may be greater than the impedance increase effect.

7 is a graph showing the above-described measurement results, and it can be easily seen that the characteristic impedance increases in proportion to the area of the ground removing region 45 when the graph is viewed.

Therefore, by increasing the area of the ground removing region 45 and further increasing the area of the portion facing the ground removing region 45 in the entire length of the signal line pattern 42, the antenna switch circuit described above is required. The characteristic impedance of 50Ω can also be met without increasing the size.

In general, a circuit in which a λ / 4 stripline is inserted, such as an antenna switching module (ASM) or a front end module (FEM), is implemented as a multilayer circuit, and the occupancy height of the number of implementation elements for each part of the circuit is determined. The ratio of λ / 4 stripline is the highest, whereas the overall height of the laminated board is limited by the light weight and miniaturization of components. Therefore, when all necessary elements are implemented in a pattern inside the board, the characteristic impedance of the line is increased. It was difficult to implement sufficiently.

In this case, as described above, by appropriately removing a part of the ground pattern disposed above and below the signal line pattern, the characteristic impedance of the stripline can be increased without easily changing the design of the other part, thereby easily implementing the desired characteristic impedance.

In addition, using it in reverse, it is possible to realize a thinner thickness of the stripline of the same characteristic impedance. As a result, it is possible to reduce the overall thickness of the laminated substrate or to implement more patterns in the laminated substrate of the same thickness, thereby improving design freedom and integration.

As described above, the present invention can adjust the characteristic impedance by removing a part of the ground pattern of the stripline, and as a result, increase the characteristic impedance to a desired value without increasing the size, or increase the stripline of the same characteristic impedance to a smaller height. It can be implemented as, has an excellent effect of improving the design freedom and integration degree of the stacked device including a λ / 4 stripline.

Claims (3)

a dielectric of thickness B formed from a material having a dielectric constant of ε _r ; A signal line pattern formed in the dielectric and having a length of? / 4 for a predetermined wavelength; A first ground pattern formed on an upper surface of the dielectric; A second ground pattern formed on the bottom surface of the dielectric; And A ground removing region formed by removing a portion of the first ground pattern or the second ground pattern at a position opposite to the signal line pattern on the upper surface or the lower surface of the dielectric material; Characteristic impedance is easily adjusted by adjusting the area of the ground removing region so that the ratio of the pattern length of the portion facing the ground removing region to the total length of the signal line pattern is 1/2 or less. λ / 4 stripline. The method of claim 1, Characteristic impedance is easily increased by adjusting the area of the ground removing region so that the ratio of the pattern length of the portion facing the ground removing region to the total length of the signal line pattern is increased. line. delete

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