KR20090089014A - Ebg structure having open stub for suppressing simultaneous switching noise in power plane - Google Patents

Abstract

An EBG(Electromagnetic Band Gap) structure is provided to maintain signal integrity by securing an SSN(Simultaneous Switching Noise) suppressing characteristic. Two patches(110a,110b) face each other. A bridge unit(10) electrically connects the two patches. The bridge unit includes a central line(11), a first extension line(12), and a second extension line(13). The central line is arranged in parallel to the patch. The first extension line is connected to one of two patches from one end of the central line. The second extension line is connected to the other of the two patches from the other end of the central line. A first open stub is formed between the central line and the first extension line. The first open stub is extended in parallel to the patch from the first extension line. The second open stub is formed between the central line and the second extension line. The second open stub is extended in parallel to the patch from the second extension line.

Description

EB structure with open stub {EBG STRUCTURE HAVING OPEN STUB FOR SUPPRESSING SIMULTANEOUS SWITCHING NOISE IN POWER PLANE}

The present invention relates to a technique for suppressing the noise (SSN: Simultaneous Switching Noise) that may occur when power is supplied to the driver IC and the like through a power plane in a high-speed digital system.

The increasing trend in digital systems is increasing the clock frequencies used with faster edge rates, and the bandwidth is getting wider for more data transfers. Accordingly, noises generated from on / off chips, packages, or multilayer PCB structures, such as the aforementioned 'SSN' and 'Ground Bounce Noise', have emerged as important technical challenges.

As is known, SSN and GBN are caused by rapidly varying time varying currents in high speed digital circuits. In particular, the SSN not only affects the transmission characteristics of the signal flowing through the surrounding vias, but the generated radio waves propagate throughout the PCB through the resonance mode of the parallel conductor plate and radiate at the edge of the PCB. . The radio waves thus radiated are the cause of Electromagnetic Interference (EMI).

A representative method for suppressing the SSN is to employ a decoupling capacitor of appropriate capacity between the power plane and the ground plane. However, this method is ineffective in the frequency band above 600MHz because of the parasitic inductance component of the decoupling capacitor [1] [2].

On the other hand, as part of the method for suppressing the SSN in the GHz band, a lot of research has recently been conducted on the power supply and ground design using the EBG (Electromagnetic BandGap) or PBG (Photonic BandGap) structure. The 'EBG structure' suppresses the flow of surface current in a specific frequency band due to the characteristics of perfect magnetic conductor and high impedance in a specific frequency range [3].

A representative EBG structure is a so-called mushroom structure consisting of square or hexagonal conductor plates connected to ground planes via vias. However, because such a structure is implemented in multiple layers, the manufacturing process is complicated and the cost increases accordingly [4] [5].

In order to solve the above problems, a method of applying a periodic EBG structure to the power supply surface while leaving the existing ground plane has been proposed [6] [7] [8] [9] [10]. Figure 1 illustrates the L-bridge EBG structure previously proposed for the power supply design, Figure 2 illustrates a basic square EBG structure. Reference numerals P1 and P2 in the drawing mean ports related to power input / output. The conventional EBG structure exemplified as above achieves rather good SSN suppression characteristics, but a peak occurs at a specific frequency within a stop band. The peaks generated in this way may lead to unexpected resonances that reduce signal integrity (SI), or may radiate and interfere with external signals.

[ references ]

[1] V. Ricchiuti, "Power-Supply Decoupling on Fully Populated High-Speed Digital PCBs", IEEE Trans. EMC, vol. 43, pp. 671-676, Nov. 2001.

[2] S. Radu, RE DuBroff, JL Drewniak, TH Hubing, and TP Van Doren, "Designing Power Bus Decoupling for CMOS Devices", in Proc. IEEE Int. Symp. EMC, Denver, CO , vol. 1, pp. 375-380, Aug. 1998.

[3] DF Sievenpiper, "High-Impedance Electromagnetic Surface", Ph. D. dissertation, Dept. Elect. Eng., Univ. California, Los Angeles, CA , 1999.

[4] S. Shahparnia and OM Ramahi, "Electromagnetic Interference (EMI) Reduction from Printed Circuit Boards (PCB) using Electromagnetic Bandgap Structures," IEEE Trans. Electromagn. Compat. , vol. 46, pp. 580-587, Nov. 2004.

[5] T. Kamgaing and OM Ramahi, "A Novel Power Plane With Integrated Simultaneous Switching Noise Mitigaion Capability Using High Impedance Surface", IEEE Microwave Wireless Comp. Lett., Vol. 13, pp. 21-23, Jan. 2003.

[6] TL Wu., YH Lin., And ST Chen., "A Novel Power Planes with Low Radiation and Broadband Suppression of Ground Bounce Noise using Photonic Bandgap Structures", IEEE Microwave Wireless Comp. Lett. , vol. 14, pp. 337-339, July 2004.

[7] T.-L. Wu, C.-C. Wang, T.-H. Lin, T.-K. Wang, and G. Chang, "A Novel Power Plane with Super-Wideband Elimination of Ground Bounce Noise on High Speed Circuits," IEEE Microwave Wireless Comp. Lett. , vol. 15, no. 3, pp. 174-176, March 2005.

[8] DY Kim, SH Joo, and HY Lee. "A Power Plane Using the Hybrid-Cell EBG Structure for the Suppression of GBN / SSN", The Journal of Korea Electromagnetic Engineering Society , vol. 18., no. 2, pp. 206-212, Feb. 2007.

[9] J. Qin and OM Ramahi, "Ultra-Wideband Mitigation of Simultaneous Swetching Noise Using Novel Planar Electromagnetic Bandgap Structures", IEEE Microwave Wireless Comp . Lett . , vol. 16, No. 9, pp. 487-489, Sep. 2006.

[10] TL Wu and TK Wang "Embedded Power Plane with Ultra-Wideband Stop-band for Simultaneously Switching Noise on High-Speed Circuits", Electronics Letters , vol. 42, no. 4, pp. 213-214, Feb. 2006.

The present invention has been made in view of the above problems, and proposes an EBG structure that can suppress peak generation in a stop band while exhibiting good SSN suppression characteristics.

The present invention proposes an open stub configured in the bridge means of the conventional EBG structure as a means for solving the problem. Looking at it by embodiment, it is as follows.

First, the first embodiment is an EBG structure in which the rectangular patches are arranged on the power plane of the PCB with a spaced space, and two adjacent patches are electrically connected by bridge means provided in the spaced space. A central line disposed parallel to the patch, a first extension line extending vertically from one end of the central line to one of the two neighboring patches, and a patch of the other one of the two neighboring patches from the other end of the central line It consists of a second extension line extending vertically.

According to a feature of the first embodiment, a first open stub is formed between the center line and the first extension line extending in parallel with the patch from the first extension line, and between the center line and the second extension line. A second open stub is formed extending from the extension line in parallel with the patch.

On the other hand, in the second embodiment, the square patches having grooves formed in the centers of the top, bottom, left, and right sides are arranged with a spaced space on the power supply surface of the PCB, and the bottoms of the opposite grooves of the two adjacent patches are arranged through the bridge means. Connected.

Further, according to a feature of the second embodiment, a first open stub is formed in the separation space between the two neighboring patches, which extends in parallel with the patch from the left side of the bridge means, and extends in parallel with the patch from the right side of the bridge means. A second opening stub is constructed.

According to the present invention, it is possible to reduce the peak in the stop band while ensuring good SSN suppression characteristics. Therefore, the signal integrity (SI) can be maintained, as well as the interference of external signaling due to radiation can be reduced.

First, in the conventional EBG structure, the rectangular patches mainly form a spaced space to form an N × N array, and the adjacent square patches have a structure in which the 'bridge means' are shared and electrically connected to each other within the spaced spaces. . Of course, conventional rectangular patch and bridge means can take various forms. The main technical construction of the present invention is an 'open stub' added to the bridge means. Therefore, hereinafter, specific features and advantages of the present invention will be described in detail with respect to the exemplary EBG structures.

[First Embodiment]

The EBG structure 100 with an open stub according to the first embodiment of the present invention is based on an L-bridge EBG structure. Referring to FIG. 3, as described above, the rectangular patches 110 form a spaced space to form an N × N array. In the present embodiment, the size of the array is set to 3x3 as shown in the drawing, but the present invention is not limited to the size of the array.

Referring to FIG. 4, a bridge means 10 for electrically connecting the patches is provided in the spaced space where the two neighboring patches 110a and 110b face each other. Specifically, the bridge means 10, the center line 11 is arranged in parallel to the patch (110a, 110b) in the separation space, and one patch (110a) of one of the two adjacent patches from one end of the center line ) And a first extension line 12 extending vertically from the other end and a second extension line 13 extending vertically from the other end of the center line to the other patch 110b.

According to a feature of the present embodiment, a first open stub 20a extending in parallel with the patch from the first extension line 12 is provided between the center line 11 and the first extension line 12. Between the line 11 and the second extension line 13 is provided a second open stub 20b extending in parallel with the patch from the second extension line 13.

In the present embodiment, the open stubs 20a and 20b are open stubs set to λ / 4, and have a function of suppressing a noise signal passing between the square patches of the EBG unit by making an electrical short at a predetermined frequency. do.

The EBG structure 100 of the first embodiment described above is formed through a power plane (PP) etching of a printed circuit board (PCB) and is part of the power plane and is electrically connected to the power plane. .

Experimental Example According to the First Embodiment

FIG. 5 is a graph showing simulation and measurement results for the conventional L-bridge EBG structure and the EBG structure according to the first embodiment illustrated in FIG. 1.

First, the PCB substrate (including the power supply surface) used in the experiment has a size of 90 mm x 90 mm, a dielectric constant of 4.1 and a thickness of 0.4 mm. In addition, the thickness of the L-bridge (center line, extension line) is 0.2 mm.

In the EBG structure 100 according to the first embodiment, the thickness of the open stubs 20a and 20b is 0.2 mm, similar to the L-bridge, and the length thereof is made using ADS LineCalc [Advanced Design System 2006, Agilent EEsof EDA]. And 18.86 mm and 15.82 mm at 2.4 GHz and 2.86 GHz, respectively. The simulation was performed using CST's Microwave Studio (http://www.cst.com), a 3D electromagnetic field numerical analysis tool.

Looking at Figure 5, in the case of the conventional EBG structure, it can be seen that the peak occurs at about 2.4GHz and 2.86GHz. The simulation results show that the peak at -23 GHz at 2.4 GHz was reduced to -52 GHz, and from -31 GHz to -54 GHz at 2.86 GHz. That is, the SSN suppression effect of about 20-30 dB or more was observed at the corresponding frequency at which the peak was generated through the λ / 4 open stubs 20a and 20b, and the overall S-parameter property was less than -40 dB.

Second Embodiment

6 is an exemplary view showing an EBG structure 200 according to the second embodiment of the present invention. The second embodiment is based on the basic rectangular EBG structure discussed in FIG. 2, and the reference numerals for the bridge means and the open stub will follow that of the first embodiment.

Specifically, as illustrated in FIG. 6, the rectangular patch 210 having the recesses 211 formed in the centers of the top, bottom, left, and right forms a predetermined spaced space to form an N × N array. Referring to FIG. 7, the bottoms of opposing grooves 211a and 211b of two neighboring patches 210a and 210b are connected by bridge means 10. The bridge means 10 are shared by two neighboring patches 210a and 210b.

In addition, according to the feature of the second embodiment, in the separation space 1 where the two adjacent patches 210a and 210b face each other, the first opening stub 20a is formed from the left side of the bridge means 10. And a second open stub 20b extends in parallel with the patch from the right side of the bridge means 10.

[Experimental Example According to Second Embodiment]

FIG. 8 is a graph showing simulation and measurement results for the conventional basic rectangular EBG structure illustrated in FIG. 2 and the EBG structure according to the second embodiment.

The thickness of the open stubs 20a and 20b of 2nd Embodiment was set to 0.5 mm, and length was 9.91 mm, and the same resources (ADS LineCalc, Microwave Studio) similar to the experiment example of 1st Embodiment were used.

Referring to FIG. 8, it can be seen that the conventional basic EBG structure has a peak at 4.4 GHz. However, in the second embodiment, the peak generated at 4.4 GHz was reduced to about -60 Hz or less. That is, it can be seen that the open stubs 20a and 20b, which are the features of the second embodiment, reduce the peaks generated at the edge portions of the stop band of the conventional EBG structure, and as a result, increase the overall SSN stop band than the conventional one.

While described and illustrated with respect to some embodiments for illustrating the technical idea of the present invention, the present invention is not limited to the configuration and operation as shown and described as such, it departs from the scope of the technical idea It will be apparent to those skilled in the art that many modifications and variations can be made to the present invention without this. Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

1 is an exemplary view showing a conventional L-bridge EBG structure,

2 is an exemplary view showing a conventional basic square EBG structure,

3 is an exemplary view showing an EBG structure according to the first embodiment;

4 is a detailed illustration showing an EBG structure according to the first embodiment;

5 is a graph showing the characteristics of the conventional L-bridge EBG structure and EBG structure according to the first embodiment,

6 is an exemplary view showing an EBG structure according to the second embodiment;

7 is a detailed illustration of the EBG structure according to the second embodiment;

8 is a graph showing the characteristics of the conventional basic square EBG structure and EBG structure according to the second embodiment.

** Description of symbols for the main parts of the drawing **

100: EBG structure with open stub according to the first embodiment

200: EBG structure with open stub according to the first embodiment

10 bridge means 20a first opening stub

20b: second opening stub

Claims (3)

A square patch is arranged on the power plane of the PCB with a spaced space, and in the spaced space where two adjacent patches face each other, an EBG structure including a bridge means for electrically connecting the two patches, The bridge means in the separation space EBG structure having an open stub, characterized in that the open stub is configured in parallel with the rectangular patch. In the EBG structure in which square patches are arranged on the power plane of the PCB with a spaced space, and two adjacent patches are electrically connected by bridge means provided in the spaced space. The bridge means may include a center line disposed parallel to the patch, a first extension line vertically extending from one end of the center line to one of the two neighboring patches, and the neighbor from the other end of the center line. A second extension line extending vertically to the other of the one or two patches, Between the center line and the first extension line, a first open stub extending in parallel with the patch from the first extension line, and between the center line and the second extension line and the patch from the second extension line An EBG structure with an open stub, characterized in that a second open stub is formed which extends in parallel. In an EBG structure in which square patches having grooves in the centers of upper, lower, left, and right sides are arranged with a spaced space on the power supply surface of the PCB, and the bottoms of the opposite grooves of two adjacent patches are connected through a bridge means. In the space between the two neighboring patches, a first open stub extending in parallel with the patch from the left side of the bridge means, and a second open stub extending in parallel with the patch from the right side of the bridge means EBG structure having an open stub, characterized in that the configuration.

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