This document discusses the design and simulation of microwave resonators using split ring resonators (SRRs) and defected ground structures. It examines individual and coupled SRRs of different orientations and numbers of gaps. Simulation results using HFSS show that adjusting the SRR gap width and orientation can control the cutoff frequency and stop-band attenuation. Coupling SRRs together splits the single resonance into multiple resonances. The design achieves sharp transition bands and high stop-band attenuation, making it suitable for compact low-pass filters.

1. MICROWAVE RESONATOR
TITLE
Design of resonator with split ring resonator and defected ground
structure with sharp transition band
AJEET KUMAR

2. TABLE OF CONTENTS
S no.
TOPIC
Page no.
1.
Abstract
4
2.
Introduction
5
3.
Split ring resonators
6
4.
Design Model Specifications
7
5.
Design steps in HFSS
8
6.
Simulated s-parameter output Graph
9
7.
Coupled split Ring Resonator Structure
13
8.
Advantage of SRR structure
17
9.
Conclusion
19
10.
References
20

3. ABSTRACT
We present a systematic simulated study of individual and coupled
split ring resonators (SRRs) of rectangular ring with one and two gaps. The
behavior of the magnetic field, the magnetic resonance frequency and the
currents in the SRRs from a single SRR to strongly interacting SRR pairs in
different orientations. The coupling of SRRs along the E direction (y) results
to shift of the magnetic resonance frequency to lower or higher values,
depending on the capacitive or inductive nature of the coupling. The strong
SRR coupling along propagation direction (x) results in splitting of the single
SRR resonance into two distinct resonances associated with field and current
distributions. For the design and simulation, HFSS 3D simulation tool is
used. On comparison it is observed that the SRR filter provides improved
performance over the conventional type filter designed using insertion loss
or stepped impedance methods. Our aim is to design a deep sharp cutoff and
compact low-pass filter.

4. INTRODUCTION
In modern wireless communication, compact size and high
performance filters are required to reduce the cost and enhance system
performances.
The defected ground structure (DGS) for microstrip lines or
coplanar waveguide (CPW) such as various photonic band gap (PBG)
structures have become interesting areas of research due to their
extensive applicability and use in microwave circuits.
DGS, i.e. etching off a defected pattern from the backside
metallic Ground-plane has periodic structures provide rejection of
certain frequency band, like band gap effects.
The resonant elements allow larger attenuation in the stopband
and higher harmonic suppressions to be obtained with less number of
periodic structures as compared to the conventional DGS. Also, by
using the proposed equivalent SRR model, a compact LPF has been
optimally designed with very high attenuation at the cut-off frequency.

5. SPLIT RING RESONATORS

6. Design Model
Individual SRRs
• Single gap
• Two gaps
• Four gaps

7. Design in HFSS

8. Graph for 0.2mm gap in Square SRR
XY Plot 1
OneGapSRRDGS
0.00
ANSOFT
Curve Info
dB(S(1,1))
Setup1 : Sw eep
dB(S(2,1))
Setup1 : Sw eep
-10.00
Y1
-20.00
-30.00
Single gap Plot
-40.00
-50.00
-56dB at 4.2GHz
-60.00
0.00
1.00
2.00
3.00
4.00
Freq [GHz]
5.00
6.00
7.00
8.00

9. Graph for 1.2 times scaled dimension of each objects in the design
XY Plot 1
OneGapSRRwith1.2timesscale
0.00
ANSOFT
Curve Info
dB(S(2,1))
Setup1 : Sw eep
dB(S(1,1))
Setup1 : Sw eep
-5.00
Y1
-10.00
-15.00
At 3.5GHz -16dB, w hich is no so much significant
-20.00
-25.00
1.00
2.00
3.00
4.00
5.00
6.00
Freq [GHz]
7.00
8.00
9.00
10.00

10. Graph for 0.4mm gap in the Square SRR
XY Plot 1
OneGapSRRWith.4mmgap
0.00
ANSOFT
Curve Info
dB(S(1,1))
Setup1 : Sw eep
dB(S(2,1))
Setup1 : Sw eep
-5.00
-10.00
Y1
-15.00
-20.00
-25.00
-30.00
-35.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
Freq [GHz]
It gives very sharp transition band as well as the stopband
attenuation (deep) is -31dB which is acceptable for practical
purposes.
9.00
10.00

11. Graph with one gap SRR coupling for the given orientiation
XY Plot 1
0.00
Name
X
Y
m1
ANSOFT
Curve Info
3.9000 -2.4307
m3
-5.00
m3
4.1000 -11.6820
m2
m2
HFSSDesign1
4.6000 -2.4335
dB(S(P1,P1))
Setup1 : Sw eep
dB(S(P2,P1))
Setup1 : Sw eep
-10.00
m1
At 4.1GHz
the attenuation is -11.682dB
-15.00
Y1
-20.00
-25.00
-30.00
-35.00
-40.00
-45.00
1.00
2.00
3.00
4.00
5.00
6.00
Freq [GHz]
7.00
8.00
9.00
10.00

12. COUPLED SPIT RING RESONATOR STRUCTURES
 Coupling of the SRRs along the E direction results to shift of the magnetic
resonance frequency to lower or higher values, depending on the
capacitive or inductive nature of the coupling respectively.
 Capacitive or inductive coupling is determined by the relative orientation of
the interacting SRRs. If orientation is associated with strong magnetic field
(and negligible electric field) in the area between the SRRs, it indicates
strong inductive coupling while if orientation is associated with strong
electric field (and negligible magnetic field), it indicates strong capacitive
coupling.

13. Different orientations and coupling of SRRs

15. Different orientations and coupling of SRRs
with four gaps
Note: Our aim is to simulate all the orientations and coupling off SRRs in HFSS
and to observe the resultant resonant frequency

16. ADVANTAGES OF DGS(SRR) STRUCTURE
 It is simple to implement and analyze
 Practical results are in agreement with simulation
 It offers a wide range of frequency, since by changing orientation, number
of gaps or the gap width, we can decrease or increase the resonant
frequency or possibly the filter response as per the requirement.
 Design is robust and is based on easy principle of inductive and capacitive
coupling

18. CONCLUSION
From the above design and simulated results, we come to
conclusion that any type of filters can be designed just by varying the
orientation of coupling of SRRs or by varying the gap width of SRR or
by increasing the number of gaps in the SRR.
The observed results are as follows:
Specification
Cut-off frequency
Stop-Band Attenuation
Gap 0.2mm
4.1 GHz
-58 dB
Gap 0.4mm
5.0 GHz
-37 dB
Designed parameters
scaled to 1.2 times
3.5 GHz
-16 dB
Coupling with
Gap 0.2mm, d=1mm
4.1 GHz
-11.68 dB
We also see that the transition band is much more sharp and the stopband attenuation is also very high.
The practical implementation of these filters are also easy and the give
results approximate to the simulated result.

19. REFERENCES
 [1] Microwave Engineering by David M Pozar, 3rd edition
 [2] Multi-gap individual and coupled split-ring resonating structures by R.
S. Penciu, K. Aydin, M. Kafesaki,Th. Koschny, E. Ozbay, E. N. Economou,
C. M. Soukoulis
 [3] Effects of a Lumped Element on DGS with Islands by Jonguk Kim, JongSik Lim, Kwangsoo Kim, and Dal Ahn