KR20110112491A - Wide band planar monopole antenna with the parabolic edges - Google Patents

Abstract

The present invention relates to a wideband planar monopole antenna in the form of a parabolic edge.
According to the present invention, the edges of the ground conductor and the monopole conductor are formed on the upper or lower surface of the dielectric substrate so that the edges of the ground conductor and the monopole conductor have a parabolic curvature, thereby providing broadband characteristics and miniaturizing the size of the parabolic curvature.

Description

WIDE BAND PLANAR MONOPOLE ANTENNA WITH THE PARABOLIC EDGES}

The present invention relates to a planar monopole antenna, and more particularly, to a wideband planar monopole antenna in the form of a miniaturized parabolic edge with wideband characteristics.

Recently, with the development of communication technology, there is increasing interest in ultra wide band (UWB) wireless technology that can share frequencies without mutual interference with narrowband and wideband systems such as mobile communication, satellite communication, and broadcast communication.

Ultra-wideband (UWB) technology is emerging as a new wireless technology that can be used without permission because of its relatively low spectral power density distribution over a much wider bandwidth compared to conventional wireless systems.

Ultra-wideband (UWB) also uses very short pulses, so even if the path reach of the direct and reflected waves is different, the two signals can be distinguished. It is possible to realize the precision of the unit of cm, and excellent in permeation characteristics of the obstacle due to the broadband characteristics, it is possible to apply to ground penetration radar (GPR) and position tracking system.

Such antennas to be used in various communication systems must satisfy the performance of broadband and group delay characteristics required by ultra wideband (UWB) systems, and in order to transmit and receive signals that must travel millions of miles, There is a need for an antenna with excellent sensitivity.

Therefore, although a logarithmic periodic antenna or a bow tie slot antenna is used as a method of improving indoor reception sensitivity of the antenna, the antennas are disadvantageous in that they are large in size and occupy space.

Therefore, the monopole antenna has a wideband characteristic and is small in size and occupies a small space. However, the monopole antenna has a linear conductor placed vertically on a wide conductor plate placed horizontally, and a narrow gap between the linear conductor and the horizontal conductor is provided. It is an antenna configured in a power feeding manner.

Therefore, the monopole antenna has a limitation in miniaturization or integration since the wide conductive plate placed horizontally becomes the ground plane of the antenna and the monopole antenna has a three-dimensional structure.

Therefore, to change the monopole antenna of the three-dimensional structure into a two-dimensional structure, when the ground plane of the monopole antenna is folded down with a straight line passing through the feed point as a folding line, the ground plane and the linear conductor are included in the same plane so that the two-dimensional structure This structure is called a planar monopole antenna.

The planar monopole antenna has an advantage of miniaturization because the substrate can be manufactured in large quantities with photolithographic (PHOTOLITHOGRAPHIC) technology.

However, the planar monopole antenna has attempted to improve the broadband characteristics by structural changes such as a circle, an ellipse, and a triangular shape of the monopole conductor. However, the planar monopole antenna has a problem that is somewhat insufficient to improve the broadband characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide a miniaturized planar monopole antenna having broadband characteristics and self-compensation characteristics with parabolic edges of a planar monopole conductor and an edge of a ground conductor.

In order to realize the above object, the present invention,

Dielectric substrates;

A ground conductor having a parabolic edge on the top surface of the dielectric substrate;

A monopole conductor having a parabolic edge on the same plane as the ground conductor;

And feeding a monopole conductor on the upper surface of the dielectric substrate with a coplaner waveguide (CPW).

Instead of the CPW, power is supplied to various transmission lines including a coaxial line, a strip line, and a microstrip line.

The monopole conductor is formed on the bottom surface of the dielectric substrate, that is, on the surface opposite to the surface on which the ground conductor is formed.

Therefore, according to the present invention, the planar monopole antenna is formed on the upper or lower surface of the dielectric substrate to have parabolic curvatures at the edges of the ground conductor and the monopole conductor, thereby providing broadband characteristics and providing an effect of miniaturizing the size. .

1 is a perspective view of a planar monopole antenna in the form of a parabolic edge of the present invention.
2 is a plan view of a planar monopole antenna in the form of a parabolic edge of the present invention.
3 is a ground conductor of a planar monopole antenna in the form of a parabolic edge of the present invention.
Return loss graph with parabolic curvature of the edges.
4 is a reflection loss graph according to the parabolic curvature change of the edge of the monopole conductor of the planar monopole antenna of the present invention parabolic edge.
5 is a graph of return loss according to the change in the gap gap between the ground conductor and the monopole conductor of the planar monopole antenna of the present invention.
6 is a reflection loss graph of the feed line length change of the planar monopole antenna of the present invention parabolic edge;
7 is a reflection loss graph comparing a simulation result and a measurement result of the planar monopole antenna of the present invention with a parabolic edge.
Figure 8 is a radiation pattern (XY plane pattern) for each frequency of the planar monopole antenna of the present invention parabolic edge shape.
Figure 9 is a radiation pattern (YZ horizontal pattern) for each frequency of the planar monopole antenna of the present invention parabolic edge shape.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 and 2, the planar monopole antenna 100 in the form of a parabolic edge has a dielectric substrate 10, a ground conductor 20, a monopole conductor 30, a feed line 40, and a gap g. It is composed.

The dielectric substrate 10 has a rectangular shape having a length of 200 mm, a width of 40 mm, and a thickness of 1,6 mm, and includes a FR4 substrate having a dielectric constant of 4.4.

The ground conductor 20 is formed on the upper surface of the dielectric substrate 10 by separating a predetermined distance T from the center of the width, and the separated ground conductor 20 is formed in a diagonal direction from the edge of the dielectric substrate 10. Is formed by the parabolic curvature ground edge 21 having a parabolic equation such that Y _A = a _A X ² + l.

Here, a _A is a quadratic coefficient and can change the electrical characteristics of the antenna as a parameter for changing the curvature of the parabola. 1 is the distance between the vertex of parabola Y _{A on} the ground conductor 20 surface and the ground bottom surface, and is the length of the feed line.

Said monopole conductor (30) is a dielectric, but formed to extend on the upper surface in the longitudinal direction of the substrate (10), said monopole conductor (30) of the same shape in correspondence with the ground edge 21 of the ground conductor (20), Y _B = a To form a parabolic curvature monopole edge 31 having a parabolic equation equal to _B × ² + l + g.

Where a _B is a quadratic coefficient that changes the curvature of the parabola and can change the electrical characteristics of the antenna. g means the space between the ground edge 21 of the ground conductor 20 and the monopole edge 31 of the monopole conductor 30.

The feed line 40 is provided at a gap T provided at the center of the ground conductor 20 to feed the monopole edge 31 of the monopole 30 with a coplanar waveguide (CPW), and the feed line 40 denotes an interval s ₁ between the feed line 40 and the ground conductor 20 so that the characteristic impedance is 50Ω, and the width w ₁ is 1 mm.

The length l of the feed line 40 is not limited, but is variably set according to the characteristics of the antenna.

The gap g is a space provided between the ground edge 21 of the ground conductor 20 and the monopole edge 31 of the monopole conductor 30, and the gap g is the ground edge 21 and the monopole. Along the edge 31 is a slot of parabolic curvature shape. The slot is not limited, but is variably set according to the characteristics of the antenna.

In the present invention configured as described above, in all cases where the return loss value is 10 dB or more, and the bandwidth can be taken for the first four parameters in consideration of the factors that most influence the initial design parameters, that is, the performance of the antenna, for digitization. Select at regular intervals for.

And the part with small quadratic coefficient of parabolic equation selects the parameter value at narrow intervals, and the part with large quadratic coefficient selects parameter value at wide intervals so that the characteristics can be sensitive to the change of antenna structure.

     Antenna parameters variable Contents size a _A Coefficient of parabolic equation of ground edge  0.05 to 0.2 (step 0.05) a _B Parabolic coefficients of monopole edges 0.5 to 2.0 (step 0.5) g Spacing change from monopole edge to ground edge 1 to 15 mm (step 5 mm) l Change in length of coplanar or waveguide feeder 5 to 30 mm (step 5 mm)

a _A is a quadratic coefficient of the ground edge parabolic equation that varies the curvature in four steps from 0.05 to 0.2 at 0.05 intervals. a _B is the quadratic coefficient of the monopole edge parabolic equation that varies the curvature in four steps from 0.5 to 2.0 at 0.5 intervals.

Change the length of the feeder line from 5 mm to 30 mm, change it in 6 steps at 5 mm intervals, and observe the change in the characteristics of the antenna by changing the gap g between the monopole edge and the ground edge in 4 steps at 5 mm intervals from 1 mm to 15 mm. do.

3 to 6 are graphs in which the characteristic change of each parameter is distinct when three parameters are fixed.

3 is an observation of the change in ground curvature for the case where three parameters are a _B = 1, g = 5 mm, and l = 30 mm. As the curvature of the ground edge 21 of the ground conductor 20 increases, it exhibits a double resonance characteristic, and in the largest case, a single resonance characteristic appears.

When the curvature a _A of the ground edge 21 of the ground conductor 20 is 0.15, double resonance appears around 530 MHz and 800 MHz, and the 10 dB bandwidth is widened.

At 0.2, the bandwidth is rather narrow, the lower frequencies are up about 20 MHz, and the higher frequencies are down about 50 MHz.

4 is an observation of the curvature change of the monopole edge 31 of the monopole conductor 30 for the case where a _A = 0.15, g = 10 mm, l = 30 mm.

As the curvature of the monopole edge 31 of the monopole conductor 30 increases, the bandwidth may be widened. In addition, the return loss characteristic is also improved.

When the curvature a _B of the monopole edge 31 is 0.5, it exhibits good reflection loss characteristics in the frequency range of 470 to 920 MHz. However, when the curvature a is 1, the monopole edge 31 has a double resonance characteristic and the overall bandwidth is increased by about 60 MHz. All.

It can be seen that the lower frequency is lowered by about 10 MHz and the higher frequency is increased by about 50 MHz. The wider the curvature, the smaller the return loss in the middle.

5 shows the curvature of the monopole edge 31 of the monopole conductor 30 and the ground edge 21 of the ground conductor 20 for the case where three parameters are l = 30 mm, a _A = 0.15, a _B = 0.5. This is an observation of the change in gap (g) between curvatures.

The wider the g, g, is the form of double resonance, and the 10 dB bandwidth is wider. When the gap g change is 1 mm, a single resonance characteristic is shown. Since the gap g is 5 mm, double resonance is shown, and the overall bandwidth is widened. A gap of 15 mm satisfies the 10 dB bandwidth in the frequency range 460 to 920 MHz.

FIG. 6 is an observation of the change of the length l of the feed line 40 for the case where three parameters are g = 10 mm, a _A = 0.15, and a _B = 0.5. It can be seen that the longer the length (l), the lower the frequency.

Also, the frequency shows double resonance in the 550 MHz and 800 MHz parts. In the case where the length l is 5 mm, the main resonance occurs in the front part, but as the length l becomes longer, the resonance point moves to the rear part. When the length (l) of the feed line 40 is 25 mm or more, it can be seen that about 30 MHz is lowered compared to 5 mm, and the volume frequency bandwidth is also widened.

Subsequently, the optimization range for each parameter is again selected based on the antenna parameters shown in Table 1 above. In other words, a _A is 0.12 to 0.16 (4 pieces), a _B is 0.4 to 0.6 (5 pieces), g is 9 to 14 mm (6 pieces), and l is 22 to 28 mm (7 pieces). Run the simulation again.

Curvature of the ground edge (a _A )  Low to High Frequency (Mhz) Bandwidth (Mhz) 0.12 480 to 960 480 0.13 480-930 450 0.14 490 to 900 410 0.15 490 to 880 390 0.16 490 to 850 360

Table 2 shows the bandwidth of the curvature change of the ground edge 21, and the reflection loss characteristics are optimized when a _B = 0.4, g = 11 mm, and l = 25 mm in the simulation results for all cases. As a result of changing the curvature a _A of the ground edge 21 from 0.12 to 0.16, it is possible to confirm the double resonance in the first half and the second half as a whole.

When the curvature a _A of the ground edge 21 increases, the resonance point of the first half tends to move to a low frequency, and the reflection loss tends to decrease at the second resonance point. I am satisfied.

When the curvature a _A of the ground edge 21 is 0.16, the 10 dB bandwidth is secured, but the lower limit frequency tends to increase.

When the curvature a _A of the ground edge 21 is 0.12, the overall bandwidth appears the widest. When the curvature a _A is 0.16, the lower limit frequency is increased by about 10 MHz and the overall bandwidth is narrowed.

In the change of curvature a _A of the ground edge 21, the change of the upper limit frequency is shown rather than the lower limit frequency, and the change of the 10 dB bandwidth with respect to the change of each ground curvature a _A is shown.

Monopole edge (a _B )  Low to High Frequency (Mhz) Bandwidth (Mhz) 0.40 470-910 440 0.45 470-910 440 0.50 470-920 450 0.55 470-920 450 0.60 470-920 450

Table 3 shows the bandwidth of the change in curvature of the monopole edge 31, a curvature (a _A) of the ground edge 21 with respect to the curvature (a _B) changes in the monopole edge 31 is 0.14, g = 11 mm, Return loss is optimized when l = 25 mm.

At this time, the curvature a _B of the monopole edge 31 is increased to 0.4, 0.45, 0.5, 0.55, and 0.6 and the reflection loss characteristic is observed. In general, two resonances appear in the digital television band, and the change in reflection loss is well represented as the curvature changes.

Looking at each change, as the curvature a _B of the monopole edge 31 increases to 0.6, the resonant frequency of the second half increases, the resonant frequency of the upper half decreases, and the reflection loss of the middle half decreases from about 15 dB to 11 dB. You can check it.

In the change of the curvature a _B of the monopole edge 31, the reference was given to the reflection loss in selecting the reflection loss and the lowest frequency, and it is assumed that the reflection loss of 15 dB is obtained.

As a result of observing the ground edge 21 of the ground conductor 20 and the monopole edge 31 of the monopole conductor 30 as a whole, it shows the structure of double resonance as a whole, and both curvatures are affected in the frequency shift of the upper half. At the resonance point of the lower half, the reflection loss characteristic is changed by the change of curvature of the ground, and the change of 10 dB bandwidth is shown for each monopole curvature.

Gap (mm) Low-High Frequency (Mhz) Bandwidth (Mhz) 9 490 to 900 410 10 490-910 420 11 480 to 900 420 12 480-910 430 13 470 to 930 460 14 480 to 920 440

Table 4 shows the 10dB bandwidth according to the change of the gap g, the curvature a _A = 0.14 of the monopole edge 31 of the monopole conductor 30, the curvature a _B = 0.4 of the ground conductor edge, the length of the CPW feed line l = 25 For the mm case, the gap g between the two conductors is observed in 1 mm increments from 9 to 14 mm. Again, the shape of the double resonance appears as a whole, and when divided into three parts and looking at the change, it can be seen that the resonance point of the lower half decreases as the gap (g) becomes longer, and the resonance point of the upper half is upward. You can see that. This widens the bandwidth as the gap g increases. It can be seen that the longer the length, the lower the lower limit frequency. The frequency bandwidth of about 10 MHz moves to the lower limit frequency. Table 4 shows the change in the 10 dB bandwidth for two conductor spacings.

Feed line length (l) (mm) Low-High Frequency (Mhz) Bandwidth (Mhz) 22 470-910 440 23 470-910 440 24 470-920 450 25 470-920 450 26 470-920 450 27 470-920 450

Table 5 shows the results of observing the return loss characteristics by varying the length from the connector to the ground edge 21 in FIG. l is the length of the coplanar waveguide (CPW) feeder. When the ground curvature a _A of the ground edge 21 is 0.14, the monopole curvature a _B of the monopole edge 31 is 0.4, and the gap g is 14 mm. The change in the length of the feeder line (l) is examined.

Changes in length (l) were observed in 1 mm increments from 22 to 28 mm. According to the change in the length l, there was no significant difference in the frequency bandwidth and the return loss, whereas the longer the length l was increased by about 10 MHz.

Optimization parameter value Ground curvature (a _A ) 0.14 Monopole curvature (a _B ) 0.4 Gap (g) 14 mm Feed line length (l) 25 mm

Table 6 shows the values of the optimized antenna parameters based on the simulated data so far.

7 is a reflection loss graph comparing the simulation results and measurement results of the parabolic edge type planar monopole antenna of the present invention. The reflection loss characteristics of the planar monopole antenna were measured using an HP8753D network analyzer. Comparing the two results, 10 dB is satisfied over the entire digital television reception frequency band.

Simulation results show a 10 dB bandwidth above 68% with a frequency range of 470 to 900 MHz and a 66.7% bandwidth between 470 and 890 MHz. However, the large difference in return loss (S11) between the simulated value and the measured value is 640 MHz.

This is due to the unbalanced coupling between the measuring equipment and the antenna, resulting in a reflected wave between the antenna end and the network analyzer, resulting in unwanted signal distortion in the return loss (S11) characteristics. In the future, this problem will be solved by combining the balun between the antenna and the network analyzer.

8 is a radiation pattern (XY plane pattern) diagram for each frequency of the planar monopole antenna of the present invention parabolic edge form, and FIG. 9 is a radiation pattern (YZ horizontal pattern) diagram for each frequency of the planar monopole antenna of the present invention parabolic edge form. The radiation patterns for the E and H planes of planar monopole antennas are shown.

E-flat Frequency (Mhz) Simulated values Measures 470 -0.81 dB -1.18 dBi 600 0.33 dB  1.86 dBi 810 1.70 dB  1.73 dBi

H-flat Frequency (Mhz) Simulated values Measures 470 -2.03 dB 0.46 dBi 600 0.33 dB  3.86 dBi 810 1.71 dB  2.28 dBi

Table 7 and Table 8 show the radiation gains for the E plane and the H plane of the parabolic edge-type planar monopole antenna, and the simulation values for the frequencies 470 (Mhz), 600, (Mhz) and 810 (Mhz). And measured value.

In addition, as a result of the measurement, the average gain in the E plane is about 0.7 dBi, and the average gain in the H plane is about 2.2 dBi. Although the two data are somewhat different, the E plane radiation pattern is null at 90 degrees and 270, while the H plane shows a uniform omnidirectional radiation pattern in all directions.

Therefore, the planar monopole antenna of the parabolic edge type for digital television reception has the ground conductor 20 and the monopole conductor 30 in the same plane, and the ground conductor 20 and the monopole conductor 30 with parabolic edges of the conductors. With the change of the parabolic edge curvature of), the two curvatures between the two conductors are important factors in determining the resonant frequency and bandwidth, and the gap between the two conductors is also a major factor in the bandwidth.

And the length of the coplanar waveguide feed line is related to the length of the entire antenna, and if the length is shortened, the overall length of the antenna is reduced and the frequency is increased. The optimally designed antenna of the dielectric substrate has an impedance bandwidth of 460 to 900 MHz, an omni-directional edge H-plane radiation pattern, and gains of 0.46 dBi, 3.86 dBi and 2.28 dBi at 470 MHz, 600 MHz, and 810 MHz, respectively. The antenna can be applied to other applications.

100; Flat monopole antenna 10; Dielectric board
20; Ground conductor 21; Ground edge
30; Monopole conductor 31; Monopole edge
40; Feeder g; gap
T; Spacing in the center of the ground conductor
s ₁ ; Gap between feeder and ground conductor
w1; Width of feeder

Claims (3)

Dielectric substrates;
A ground conductor having a parabolic edge on the top surface of the dielectric substrate;
A monopole conductor having a parabolic edge on the same plane as the ground conductor;
A broadband planar monopole antenna having a parabolic edge type that feeds a monopole conductor on a top surface of the dielectric substrate with a coplaner waveguide (CPW). The method of claim 1,
The CPW is a broadband planar monopole antenna in the form of a parabolic edge that feeds a variety of feed lines including coaxial lines, strip lines, and micro strip lines. The method of claim 1,
And a parabolic edge formed on the lower surface of the dielectric substrate, that is, the surface opposite to the surface on which the ground conductor is formed.

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