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The Study of Periodic/non-periodic Ground

Structure in Microstrip Circuit

Yan Zhou

Shool of Electronic Information EngineeringBeijing University of Aeronautics & Astronautics

Email: zhy2004bj@ee.buaa.edu.cn 

Donglin Su

Shool of Electronic Information EngineeringBeijing University of Aeronautics & Astronautics

Email: sdl@buaa.edu.cn 

 Abstract  —The non-intact ground structure have been discussed in

this paper. Using the unique transmit response of periodic PBG

and non-periodic DGS structure, to weaken the effect of high rank

harmonious wave and improve the frequent characteristic, and to

realize effectual optimization and amelioration of passive circuit in

microwave system especially at microstrip circuit .The simulation

and test prove the validity and practicability of the periodic/non-

periodic ground structure in microstrip circuit .

I. I NTRODUCTION

Periodic/non-periodic circuit ground structure have been

researched deeply in recent years. Non-periodic defect ground

system structure(DGS) and periodic photonic band gap

structure(PBG) have been more and more used at modern

transmit of light wave and microwave. DGS structure root in the

application and extend of PBG in plane- microstrip circuit, a

uique case of PBG.

The concept of PBG come from the research for Photonic

Crystal. Photonic crystal have characteristic of band gap at

different direction and could weaken light wave at specifical

frequency. At frequency of microwave and mm-wave , this phenomena have very much more application in recent time. We

could get band stop transmit characteristic at 1-D, 2-Dor 3-D

direction by using period PBG material or structure. DGS

structure have similar effect but design is more agility. In plane

microstrip circuit, period PBG and non-period DGS structure

could be designed to realize wide-band filter. At field of antenna

design, restraining surface wave and weakening cross

interference is these structure’s unique advantage. In modern

 photon communication, PBG structure could improve the

efficiency of LED, or reduce off band waste by way of

frequency selection surface being incumbent on radiator.

This paper based the fruit of PBG & DGS by previous people,

fix the important on the transmission effect of period/non-period

microstrip ground structure. And using HFSS to simulation a

kind of UC-PBG band pass filter.

This paper presents both basic characteristics and applications

of period PBG and non-period DGS stricture. The characteristic

of PBG and UC-PBG structure is introduced in Section II. The

characteristic of DGS structure is introduced in Section III. And

Section IV presents the the design method and the simulation by

HFSS about UC-PBG band pass filter. All above followed by

conclusions in Section V.

II. THE CHARACTERISTIC OF PERIODIC PBG STRUCTURE IN

MICROSTRIP CIRCUIT

Photonic band gap (PBG) engineering has been observed

widely in field of microwave and millimeter wave circuit.

Applications of PBG materials or structure include microstrip

filter, microstrip antennas, sesonant cavities, and so on. The still

of plane PBG structure is very diversiform, such as fig.1, andcould been realized in many ways, such as eroding some period

units in medium layer, but these units does not penetrate ground.

Another usual structure is UC-PBG (Unipalar Compact Photonic

Bandgap), this PBG structure is realized with metal pads etched

in the ground plane connected by narrow lines to form a

distributed RLC network, such as fig. 2. Vias holes or multilayer

substrates are not required in this novel PBG structure. A

distinctive stopband over a wide range of frequency is observed

and the measurement results agree with FEM simulation. This

characteristic of UC-PBG could be used at filter design to

optimize the frequency performance. Another unique feature of

this PBG structure is the realization of a slow-wave microstrip

line with low insertion loss. Slow-wave-mode propagation is of

great interest for its use in reducing the dimension of distributed

components in integrated circuits.

The characteristic of PBG structure is defined by several

elements such as the number of period units, the geometry

structure of each period unit, the arrange still and dielectric

coefficient, and so on. In antenna design, the PBG structure

could weaken the surface wave loss radiating at dielectric layer

and improve the efficiency of antenna and optimize its

 performance accordingly. And at the same time, this

PBG/antenna structure could be seen a kind of slow-wave

structure,

In other application fields, the UC-PBG reflector put up a

 phenomena of PMC at the stopband frequency where the

 periodic loading changes the surface impedance to an open-circuit condition. The surface impedance of the proposed

structure is frequency-sensitive since the PBG structure actually

forms a distributed RLC network with specific resonant

frequencies, such as fig.2.

By way of most popular PBG circuit still, the UC-PBG

structure could be formed easily with common eroding process.

And UC-PBG could be integrated in MMIC, the compatibility

of UC-PBG is better than other PBG plane still. The total

microstrip with UC-PBG ground have better slow-wave effect

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than common microstrip, up to 2.4 times. This characteristic is

very useful in microwave circuit application. But the primary

useful characteristic of the UC-PBG is its band stop response in

microstrip circuit. Such as fig.3, the simulation of microstrip

with UC-PBG ground modeled in HFSS have demonstrated the

distinct frequency band stop without other components.

III. THE CHARACTERISTIC OF NON-PERIODIC DGS MICROSTRIP

STRUCTUREThe non-periodic DGS structure come from the research of

PBG. The DGS is abbreviation of defected ground state. Various

research results have dealt with DGS for the purpose of applying

to an active device as well as a passive circuit. It has been

applied to several active devices such as power amplifers and

oscillators, with improvements of their performance.

The structure of DGS such as fig.3, could be equivalented

to a LC resonance circuit, the etched lattice shape is non-

 periodic structure and have different manner of a PBG. The

equivalent inductances and capacitances could vary with the

change of gap and connection of unit. The major use of single

unit DGS is low pass or high pass filter, could control its loss

extra point by the way we want to without adding othercomponents. The dual-dipole DGS structure could be designed

to resolve the unique problem, its equivalent circuit such as fig.3.

IV. THE SIMULATION AND TEST OF UCPBG BANDPASS FILTER  

For the purpose of improve one of the C-band filter used in

satellite communications. We design the UC-PBG band pass

filter. The use of UC-PBG is mainly to overcome the effect of

spurious passbands at harmonic frequencies, which tend to

degrade the performance of the overall RF system. The

advantages of the UC-PBG can be applied to construct a

compact microstrip BPF with intrinsic spurious rejection. The

well-matched microstip on the UC-PBG structure is appropriate

for the use as a low loss transmission line, and the wide and

deep stopband of this structure can be designed to suppress the

spurious passbands at higher harmonics.

Fig .4 shows the microstrip line with UC-PBG and its stop

 band response, we can clearly see its stop band with -40dB. We

can use its performance to estimate the unit period of PBG we

needed in UC-PBG band pass filter.

The design of the parallel coupled band pass filter follows

the standard procedures. The BPF is designed with seven

sections, a 0.2 dB equal-ripple response, and a center frequency

of 5.33GHz.and band wide 850MHz, all parameters of this

design is defined by AWR software, and the dielectricr 

ε  =9.6.

Such as fig. 5, we make the UC-PBG’s unit period a=105mil.

 by the result of test and its compare to non-PBG structure filter,we can see that. The the effect of UC-PBG is very obvious since

9.5 GHz with the spurious passbands at second harmonics begin

at 10GHz. And the UC-PBG band pass filter weaken about 10

dB at second harmonics wave than the non-PBG structure filter.

V. CONCLUSION 

This paper discuss and study the transmit characteristic of

microstrip with period PBG and non-period DGS structure, and

they behave at microwave circuit system, especially at

microstrip line and microstrip filter design. By simulation test on

ADS and other software and a experiment of C band band-pass

half wavelength side couple PBG ground filter, we prove its

effective. The period and non-period ground structure could

great the capacitance and inductance response by changing thestructure of ground without adding extra circuit components,

and improve the frequency performance of microstrip circuit

By the electromagnetic simulation software such as HFSS and

so on, we can analyse its performance and characteristic. The

UC-PBG band pass test prove its validity.

ACKNOWLEDGMENT

Give my best acknowledgment to my mentor, Professor

Donglin Su, and those people who support me when I was getin

trouble on my research .

Fig.1 several unit stills of PBG plane structure

Fig.2 equivalent circuit of PBG unit

Fig.3 the DGS& dual-dipole DGS unit and

equivalent circuit

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Fig.4 microstrip with UC-PBG and its 21S  simulation

Fig.5 the circuit board and assemble sample

Fig.6 the test result of UCPBG band pass filter

(curve1: non PBG strucute ; curve2: with PBG structure)

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