reconfigurable electromagnetic · is studied using cst microwave studio software which shows pass...
TRANSCRIPT
RECONFIGURABLE ELECTROMAGNETIC
BANDGAP STRUCTURES
LALITHENDRA KURRA
CENTRE FOR APPLIED RESEARCH IN ELECTRONICS
INDIAN INSTITUTE OF TECHNOLOGY DELHI
OCTOBER 2015
RECONFIGURABLE ELECTROMAGNETIC
BANDGAP STRUCTURES
by
LALITHENDRA KURRA
Centre for Applied Research in Electronics
Submitted
in fulfillment of the requirements of the degree of
Doctor of Philosophy
to the
INDIAN INSTITUTE OF TECHNOLOGY DELHI
OCTOBER 2015
i
CERTIFICATE
This is to certify that the thesis entitled, “RECONFIGURABLE ELECTROMAGNETIC
BANDGAP STRUCTURES”, being submitted by Mr. Lalithendra Kurra for the award of
the degree of Doctor of Philosophy to the Centre for Applied Research in Electronics,
Indian Institute of Technology Delhi, New Delhi, is a record of bonafide research work
carried out by him under our guidance and supervision.
Mr. Lalithendra Kurra has fulfilled the requirements for the submission of this thesis,
which to our knowledge has reached the requisite standard. The results contained in this
thesis have not been submitted in part or in full to any other university or institute for the
award of any degree or diploma.
(Dr. Shiban. K. Koul)
Professor
Centre for Applied Research in
Electronics
Indian Institute of Technology Delhi
Hauz Khas, New Delhi-110016, India
(Dr. Mahesh P. Abegaonkar)
Associate Professor
Centre for Applied Research in
Electronics
Indian Institute of Technology Delhi
Hauz Khas, New Delhi-110016, India
iii
ACKNOWLEDGEMENTS
I would like to take this opportunity to thank all those who have assisted me during my
research work in terms of technical support, moral support and friendship.
First, I am deeply indebted to Prof. Shiban. K. Koul and Dr. Mahesh P. Abegaonkar
for giving me an opportunity to work in this esteemed institution and agreeing to advise
me in the area of electromagnetic bandgap structures.
I would like to express my sincere gratitude to Prof. Shiban. K. Koul for his motivation
and support given to me throughout my research work. I also want to thank him for his
inspirational words related not only to the academics but also to philosophy of life.
I want to sincerely thank Dr. Mahesh P. Abegaonkar for his continuous encouragement,
discussions, support, suggestions and critical evaluation of the work at every stage of my
research work. Without his guidance, this thesis would not have taken this shape. His
vision laid a roadmap for my research work.
I want to give special thanks to Prof. Ananjan Basu for his support, inspiration and
critical advice given during my research work. I also thank Dr. Karun Rawat for his
advice and motivation towards my research goals. I thank Prof. Devi Chadda and Prof.
Sudhir Chandra, members of my research committee, for giving time and suggestions.
Their profound knowledge, professional ethics and generous attitude will surely benefit
rest of my career and my personal life.
I would like to thank Department of Science and Technology (DST) and National
Programme on Smart Materials and Systems (NPMASS) for providing some financial
support during my stay at IIT Delhi as a research scholar.
I would also like to thank my colleagues Mithlesh Kumar, Manoj Singh Parihar, Sandeep
Chaturvedi, Madhur Deo Upadhyay, Ritabrata Bhattacharya, Sukomal Dey, Sanjeev
Kumar, Srujana Kagita, Saurabh Pegwal, Ankita Katyal, Pooja Prakash, Rajesh Kumar
iv
Singh, Robin Kalyan, Deepika Sipal, Anushruti Jaiswal and Ayushi Barthwal for their
suggestions, moral support and friendly company. I also thank colleagues from other
laboratories, Monika, Lalat Indu Giri, Pradeep Rathod, and other research scholars of
CARE and M.Tech students of microwave group for their company during my research
work. Mr. Phaneendra Babu Bobba and Satish Babu Bhogineni, Ph. D. students from
electrical department also deserve thanks for their suggestion and company during my
stay in IIT Delhi. I would like to thank Mr. S. P. Chakraborty for his support and help
rendered during my research work. I would also like to thank Ashok Pramanik and
Pradeep Saxena for sharing their experience that helped me in my research work.
I would like to thank all the faculty and staff members of CARE who helped me in
various ways during my research work in CARE.
I thank IIT Delhi for providing accommodation for me and my family at IIT Delhi
campus. I would like to thank Phaneendra Babu's family for their support and
companionship to my family during their stay in IIT Delhi campus.
I would like to thank my parents, in-laws and other relatives for their continuous
encouragement, support and unconditional love. I am grateful to my father,
Satyanarayana, for his motivation which brought me to this level. I am also grateful to
my wife, Mrs. Harika for her patience, support, understanding, responsibilities she has
taken and for the sacrifices she has made during my course of research are priceless. I
would also like to value the presence of my 5 year son, Revanth Kumar, whose smiles
made me happy and the time I spend with him helped me in relaxation.
Finally, I thank Lord Venkateswara, for his blessings which has given me opportunity,
provided me strength, intellect and help through all the above mentioned persons that led
to successful completion of the thesis.
Lalithendra Kurra
v
ABSTRACT
The research work in this thesis is focussed on planar electromagnetic band gap
(EBG) structures, their characterization, applications and re-configurability. A planar
EBG structure is proposed using meander line inductors and interdigital capacitors. The
computed band gap of the proposed EBG structure is from 5.48-7.9 GHz, whereas the
band gap of the conventional EBG structure is from 9.41 to 12.41 GHz. Nearly 38%
reduction in the band gap centre frequency is achieved. Surface wave measurements
performed on 7 × 7 array of proposed EBG unit cells also confirms the band gap from
5.74-8 GHz band.
One dimensional array (1 × 7) of proposed EBG structure when loaded on either
side of a transmission line resulted in band stop/notch filter. The measured 3-dB
bandwidth of the band stop filter is from 4.95-5.37 GHz. The notch filter utilizing the
proposed EBG structure is cascaded to multiple-mode resonator (MMR) ultra-wideband
(UWB) filter to achieve a band-notched UWB filter. Single band-notched UWB filter
with notch centred around 5.16 GHz and dual band-notched UWB filter with notches
centred around 5.16 GHz and 8.24 GHz are achieved. Along with the filter, a band-
notched UWB antenna is also developed. Equivalent circuit of unit cell coupled to a
transmission line is developed and it is observed that the circuit simulated results
matched well with EM simulated results.
Re-configurability is achieved by connecting an additional section made of
interdigital lines (capacitor) to the unit cell using switches, which changes the effective
capacitance and hence the resonance frequency. Switchable filter is developed with 16
PIN diodes (MA4SPS402) connected in parallel and biased at 160 mA of total current in
the ON-state. In the ON-state, the measured 10-dB notch bandwidth is 0.344 GHz
centred around 5.095 GHz, and in the OFF-state, it is 0.316 GHz centred around 5.545
vi
GHz. A 450 MHz shift in frequency is observed by switching the diodes. By using
MA46H120 varactor diodes in the same circuit instead of PIN diodes, tunable notch filter
is achieved with notch band centre frequency tuned from 5.09 GHz to 5.43 GHz.
Equivalent circuit is developed for reconfigurable cell in the ON- and OFF-state.
Bandwidth reconfigurable band stop filter is developed using another
configuration of the unit EBG cell with a single meander line in parallel with a
interdigital capacitor. Using PIN diodes (MA4SPS402), the bandwidth of the notch is
varied. In the OFF-state, the 10-dB stop band is from 6.84 GHz to 7.47 GHz and in the
ON-state it is from 6.41 GHz to 7.33 GHz. 290 MHz increase in the bandwidth is seen in
the ON-state compared to the OFF-state.
By coupling EBG structure in broadside to the transmission line, a better band
stop filter is designed compared to the earlier edge coupled case. A multi-layered band-
pass filter (BPF) with suppressed harmonics is developed by broadside coupling three
unit cells in transverse direction to two open ended microstrip lines. The measured centre
frequency of the BPF is 2.56 GHz with 3-dB bandwidth of 0.38 GHz and harmonics are
below 20 dB up to 11 GHz. Diplexer is developed using the proposed BPF to mix 2.5
GHz signal from port 2 and 3.7 GHz signal from port 3 into port 1. The measured
isolation is better than 18 dB in the first pass band and in the second pass band it is better
than 26 dB. The harmonics are suppressed well below 10 dB up to 10 GHz.
Frequency selective surface property of the proposed structure (3.51 × 3.51 mm2)
is studied using CST Microwave Studio software which shows pass band characteristics
at 10.8 GHz. FSS screen formed by printing 13 × 13 array of unit is used as a superstrate
to a patch antenna operating at 10.8 GHz. The gain of the antenna is improved by 7 dB
with the FSS superstrate.
vii
TABLE OF CONTENTS
CERTIFICATE .................................................................................................................. i
ACKNOWLEDGEMENTs ............................................................................................ iii
ABSTRACT ....................................................................................................................... v
TABLE OF CONTENTS ................................................................................................ vii
LIST OF FIGURES ......................................................................................................... xi
LIST OF TABLES ......................................................................................................... xxi
1. INTRODUCTION ......................................................................................................... 1
1.1. Scope and Objective of the Work ............................................................................ 1
1.2. Organization of the Thesis ...................................................................................... 2
1.3. Electromagnetic Bandgap Structures ...................................................................... 4
1.3.1. Mushroom EBG Structure ............................................................................. 5
1.3.2. Uni-planar EBG Structure ............................................................................. 6
1.3.3. Properties of EBG Structures ........................................................................ 7
1.3.4. Compact EBG Structures .............................................................................. 8
1.3.5. Application of EBG Structures .................................................................... 12
1.3.6. Characterization of EBG Structures ............................................................ 19
1.3.6.1. Dispersion Diagram ..................................................................... 19
1.3.6.2. Surface Wave Measurement ........................................................ 22
1.3.6.3. Suspended Microstrip Method ..................................................... 24
1.3.6.4. Truncated Microstrip Line ........................................................... 24
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1.3.6.5. Reflection Phase Characteristics .................................................. 25
1.3.6.6. EBG Coupled Microstrip Line ..................................................... 26
1.3.7. Reconfigurable EBG Structures .................................................................. 27
1.3.8. Resonant-like EBG Structures .................................................................... 30
2. PROPOSED PLANAR EBG STRUCTURE ............................................................. 33
2.1. Introduction ........................................................................................................... 33
2.2. Proposed EBG Structure ....................................................................................... 33
2.3. Dispersion Diagram .............................................................................................. 35
2.4. Measurement Technique for Characterizing EBG Structure ................................ 37
2.5. EBG Loaded Transmission Line ........................................................................... 39
2.6. Equivalent Circuit Model ...................................................................................... 44
2.7. Conclusion ............................................................................................................ 61
3. APPLICATION OF EBG BAND STOP FILTER ................................................... 63
3.1. Introduction ........................................................................................................... 63
3.2. MMR UWB Filter ................................................................................................. 64
3.3. Band-Notched UWB Filter ................................................................................... 66
3.3.1. Single Band-Notched UWB Filter .............................................................. 66
3.3.2. Dual Band-Notched UWB Filter ................................................................. 72
3.4. Band-Notched UWB Antenna .............................................................................. 74
3.5. Conclusion ............................................................................................................ 80
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4. RECONFIGURABLE AND TUNABLE EBG STRUCTURES ............................. 81
4.1. Introduction ........................................................................................................... 81
4.2. Switchable Band-Notched UWB Filter ................................................................. 82
4.3. Tunable Notch Filter ............................................................................................. 89
4.4. Equivalent Circuit of Frequency Reconfigurable Unit Cell .................................. 91
4.5. Bandwidth Reconfigurable Band Stop Filter ........................................................ 93
4.6. Conclusion ............................................................................................................. 98
5. BAND PASS FILTER AND DIPLEXER ................................................................. 99
5.1. Introduction ........................................................................................................... 99
5.2. Band Stop Filter with Broadside Coupled EBG Cell ............................................ 99
5.3. Band Pass Filter (BPF) ........................................................................................ 105
5.4. Diplexer ............................................................................................................... 110
5.5. Conclusion ........................................................................................................... 116
6. FREQUENCY SELECTIVE SURFACE (FSS) APPLICATION ........................ 117
6.1. Introduction ......................................................................................................... 117
6.2. FSS Properties of the Proposed EBG Structure .................................................. 117
6.3. Application of FSS for Directivity Enhancement of the Patch Antenna ............. 121
6.3.1. Inset Feed Patch Antenna .......................................................................... 121
6.3.2. Patch Antenna with FSS as a Superstrate .................................................. 125
6.4. Conclusion ........................................................................................................... 134
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7. CONCLUSION AND FUTURE SCOPE ................................................................ 135
7.1. Summary of the Thesis........................................................................................ 135
7.2. Future Scope of the Work ................................................................................... 137
REFERENCES .............................................................................................................. 139
APPENDIX - A .............................................................................................................. 155
APPENDIX - B .............................................................................................................. 163
PUBLICATIONS .......................................................................................................... 167
BRIEF BIO-DATA OF THE AUTHOR ..................................................................... 169
xi
LIST OF FIGURES
Fig. 1.1. Mushroom EBG structure (a) array and (b) cross-sectional view (origin of
capacitancce and inductance) [11], [12]. ..................................................................... 6
Fig. 1.2. 3×3 array of UC-PBG unit cells. .......................................................................... 7
Fig. 1.3. Spiral mushroom EBG structure [23]. ................................................................. 8
Fig. 1.4. Polar mushroom EBG structure [25]. ................................................................... 8
Fig. 1.5. Stacked mushroom EBG structure [12]. ............................................................... 9
Fig. 1.6. Mushroom EBG structure with intedigital lines [26]. .......................................... 9
Fig. 1.7. Fork-like EBG structure [27]. ............................................................................... 9
Fig. 1.8. Compact mushroom EBG structure with CSRR etched on the top metal plate
[29]. ........................................................................................................................... 10
Fig. 1.9. Compact planar EBG unit cell formed by distorting conventinal UC-EBG [30].
................................................................................................................................... 11
Fig. 1.10. Compact planar EBG cell with triangular plates and peripheral traces [31]. ... 11
Fig. 1.11. Schematic of two unit cells of compact planar EBG structure [32]. ................ 11
Fig. 1.12. Compact EBG unit cell [33]. ............................................................................ 11
Fig. 1.13. EBG unit cell with meander lines and inter-digital capacitors [34].................. 12
Fig. 1.14. Spiral capacitor and meander inductor (SC-ML) planar EBG structure [35]. .. 12
Fig. 1.15. Rabbet spiral dual-band EBG structure [40]. .................................................... 12
Fig. 1.16. Cross-sectional view of patch antenna surrounded by mushroom EBG structure
[11]. ........................................................................................................................... 13
Fig. 1.17. Top view of patch antenna surrounded by conventional UC-EBG structure
[14]. ........................................................................................................................... 13
Fig. 1.18. Array antenna with mushroom EBG for mutual coupling reduction [43]. ....... 14
Fig. 1.19. Array antenna with UC-EBG for mutual coupling reduction[45]. ................... 14
xii
Fig. 1.20. TEM-waveguide with UC-PBG structure [50]. ................................................ 15
Fig. 1.21. LPF on UC-PBG ground plane. (a) Schematic diagram. (b) Results [51]. ...... 15
Fig. 1.22. Parallel coupled microstrip BPF with UC-PBG ground plane. (a) Schematic
diagram. (b) Results compared with the conventional BPF [13]. ............................. 16
Fig. 1.23. Comparison of transmission in CB-CPW, CB-CPW with PBG ground plane
and CPW [54]. .......................................................................................................... 16
Fig. 1.24. Horizontal wire antenna over (a) conducting flat metal plate, (b) high
impedance ground plane (c) and return loss versus frequency characteristics [11]. 17
Fig. 1.25. Schematic diagram of slot antenna backed with UC-PBG [57], [58]. ............. 18
Fig. 1.26. Unit cell of UC-EBG structure showing irreducible Brillouin zone [14]......... 20
Fig. 1.27. Simulation set up for dispersion diagram. ........................................................ 20
Fig. 1.28. Dispersion diagram of UC-PBG structure with 25 mil substrate. (a) Computed.
(b) Reported [14]....................................................................................................... 22
Fig. 1.29. Dispersion diagram of UC-PBG structure with 50 mil substrate. (a) Computed
(b) Reported [14]....................................................................................................... 22
Fig. 1.30. TM surface wave measurement set up [12]. ..................................................... 23
Fig. 1.31. TE surface wave measurement set up [12]. ...................................................... 23
Fig. 1.32. Method of suspended microstrip [27]. .............................................................. 24
Fig. 1.33. Transmission through UC-PBG lattice by truncated microstrip line. (a) Top
view. (b) Transmission characteristics. [14]. ............................................................ 24
Fig. 1.34. Reflection phase measurement set up [11], [12]. ............................................. 25
Fig. 1.35. Reflection phase of a two-layer high-impedance surface [11], [12]. ............... 25
Fig. 1.36. Mushroom EBG structure coupled to microstrip transmsision line [69].......... 26
Fig. 1.37. Band-notched UWB filter using IDCLLR structure [77]. ................................ 26
Fig. 1.38. Reconfigurable fork-like EBG unit cell [27]. ................................................... 28
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Fig. 1.39. Short-circuited hairpin resonator. (a) Schematic diagram of unit cell. (b) Cells
loaded to a transmission line. (c) Result of reconfiguraable filter [88], [89]. ........... 29
Fig. 1.40. UWB filter with tunable notch based on folded SIR [75]. ............................... 30
Fig. 1.41. Reconfigurable frequency band-notched ultra-wideband (UWB) antenna using
SRR [90]. ................................................................................................................... 30
Fig. 1.42. Anisotropic UC-PBG etched on ground plane of microstrip line [93]. ............ 32
Fig. 2.1. Proposed planar EBG unit cell. ........................................................................... 34
Fig. 2.2. Conventional planar EBG unit cell. .................................................................... 34
Fig. 2.3. Dispersion diagram of the proposed EBG structure. .......................................... 35
Fig. 2.4. Dispersion diagram of the conventional planar EBG structure. ......................... 36
Fig. 2.5. Dispersion diagram of the proposed EBG strcucture along Γ-X-M-Y-Γ
irreducible brillouin square. ...................................................................................... 36
Fig. 2.6. Dispersion diagram of the proposed EBG structure drawn for the entire
structure. .................................................................................................................... 37
Fig. 2.7. Photogragh of fabricated array of 77 proposed EBG cells. .............................. 38
Fig. 2.8. Measured results of TE and TM surface waves in the proposed EBG structure.
................................................................................................................................... 39
Fig. 2.9. EBG structure coupled to a microstrip line. (a) Schematic diagram. (b)
Photograph of fabricated circuit. (c) Simulated and measured results. ..................... 40
Fig. 2.10. Surface current plot of EBG loaded transmission line (a) at 6.1 GHz in
passband and (b) at 5.25 GHz in stopband. ............................................................... 41
Fig. 2.11. Unit cell of structure 'B'. (All dimensions are in mm.) ..................................... 42
Fig. 2.12. Simulated results of various proposed structures loading a transmsion line. ... 42
Fig. 2.13. Simulated results of the proposed EBG structure loading a tranmision line for
various values of d. ................................................................................................... 43
xiv
Fig. 2.14. Simulated results comparing the proposed structure (Fig. 2.1) and conventional
structure (Fig. 2.2) loading a transmission line......................................................... 44
Fig. 2.15. Single unit cell coupled to a microstrip transmission line. ............................... 45
Fig. 2.16. Meander line inductor. (a) Metal pattern. (b) Equivalent circuit model. .......... 46
Fig. 2.17. Magnetic flux lines. (a) Positive mutual inductance. (b) Negative mutual
inductance. ................................................................................................................ 47
Fig. 2.18. Parallel strips with complete overlap................................................................ 47
Fig. 2.19. Parallel strips overlapped with unequal strip lengths. ...................................... 48
Fig. 2.20. Parallel strips partially overlapped with unequal strip lengths. ........................ 48
Fig. 2.21. Parallel strips without overlap. ......................................................................... 49
Fig. 2.22. Symmetrical coupled microstrip lines. (a) Odd-mode capacitance. (b) Even
mode capacitance. ..................................................................................................... 50
Fig. 2.23. Intedigital capacitor. (a) Metal pattern. (b) Equivalent circuit. ........................ 54
Fig. 2.24. Asymmetric coupled microstrip transmission line. ......................................... 55
Fig. 2.25. Coupling capacitance between transmission line and the unit cell. ................. 58
Fig. 2.26. Equivalent circuit of a single unit cell coupled to a transmission line. ............ 58
Fig. 2.27. Comparison of circuit and EM simulated results of a single cell coupled to a
transmission line. ...................................................................................................... 59
Fig. 2.28. Band stop filter. (a) Equivalent circuit. (b) Comparison of circuit and EM
simulated results........................................................................................................ 60
Fig. 3.1. MMR weakly coupled to 50 Ω transmission lines. (All dimensions are in mm.)
................................................................................................................................... 64
Fig. 3.2. Resonant frequencies of MMR. .......................................................................... 64
Fig. 3.3. MMR UWB filter. (a) Schematic diagram. (b) Photograph. (c) Measured and
simulated results........................................................................................................ 66
xv
Fig. 3.4. Band-notched UWB filter with EBG coupled to output line (Filter A). (a)
Photograph. (b) Measured results. (c) Comparison of measured and simulated
results. ....................................................................................................................... 68
Fig. 3.5. Simulated results of band-notched UWB filter with electric and open add space
boundary conditions. ................................................................................................. 69
Fig. 3.6. Band-notched UWB filter with EBG structure coupled to input and output lines
(Filter B). (a) Photograph. (b) Measured and simulated results. ............................... 70
Fig. 3.7. Band-notched UWB filter with EBG structure coupled to input line, output line
and low impedance line of the filter (Filter C). (a) Photograph. (b) Measured and
simulated results. ....................................................................................................... 71
Fig. 3.8. Unit cell sized to 3.65 mm × 3.65 mm................................................................ 72
Fig. 3.9. Dual band-notched UWB filter (Filter D). (a) Photograph. (b) Measured results.
................................................................................................................................... 73
Fig. 3.10. Schematic diagram of the band-notched UWB antenna. (a) Front View. (b)
Back View. (a=44.45, b=20.55, s=0.1, d=1, g=0.06, L=4.95, r=7.86 and all
dimensions are in mm). ............................................................................................. 75
Fig. 3.11. Photograph of the band-notched UWB antenna. (a) Front view. (b) Back view.
................................................................................................................................... 75
Fig. 3.12. Measured and simulated |S11| of the band-notched UWB antenna. .................. 76
Fig. 3.13. E-plane pattern (y-z plane - φ=90) of the band-notched UWB antenna. (a)
Simulated. (b) Measured. .......................................................................................... 77
Fig. 3.14. H-plane pattern (x-z plane - φ=0) of the band-notched UWB antenna. (a)
Simulated. (b) Measured. .......................................................................................... 78
Fig. 3.15. Gain of the UWB antenna and the band-notched UWB antenna. .................... 79
xvi
Fig. 3.16. Surface current in the band-notched UWB antenna at (a) 5.2 GHz and (b) 8
GHz. .......................................................................................................................... 80
Fig. 4.1. Schematic diagram of metal pattern of the reconfigurable EBG. (All dimensions
in mm.) ...................................................................................................................... 82
Fig. 4.2. Switchable band-notched UWB filter implemented with diodes. (a) Photograph.
(b) Zoomed view showing band stop filter with various elements. .......................... 83
Fig. 4.3. Photograph of the switchable band-notched UWB filter. (a) Ideal ON-state. (b)
Ideal OFF-state.......................................................................................................... 84
Fig. 4.4. Simulated and measured results of the switchable band-notched UWB filter. (a)
Ideal ON-state. (b) Ideal OFF-state. ......................................................................... 86
Fig. 4.5. Simulated results with over-etching, without over-etching and measured results
of the switchable band-notched UWB filter in the ideal ON-state. .......................... 86
Fig. 4.6. Simulated results of switchable band-notched UWB filter in CST and ADS. (a)
ON-state. (b) OFF-state. ........................................................................................... 88
Fig. 4.7. Measured results of the switchable band-notched UWB filter with diodes in the
ON-state and OFF-states. .......................................................................................... 89
Fig. 4.8. Comparison of measured and ADS simulated results of the switchable band-
notched UWB filter implemented with diodes. ........................................................ 89
Fig. 4.9. Measured results of the tunable notch filter with varactor diode in reverse bias.
................................................................................................................................... 90
Fig. 4.10. Variation of frequency and bandwidth of the tunable filter with bias voltage of
varactor diode............................................................................................................ 90
Fig. 4.11. Reconfigurable EBG unit cell coupled to a transmission line. ......................... 91
Fig. 4.12. Equivalent circuit of the reconfigurable EBG unit cell coupled to a
transmission line. ...................................................................................................... 92
xvii
Fig. 4.13. Comparison of circuit simulated and EM simulated results of the
reconfigurable unit cell coupled to a transmission line. ............................................ 93
Fig. 4.14. Two unit cells connected by a switch ............................................................... 94
Fig. 4.15. Photograph of the fabricated bandwidth reconfigurable band stop filter and its
zoomed view showing various elements. .................................................................. 95
Fig. 4.16. Photograph of the ground plane of the bandwidth reconfigurable band stop
filter (Fig. 4.15). ........................................................................................................ 95
Fig. 4.17. ADS simulated results of the bandwidth reconfigurable filter with diode in the
ON- and OFF-states. ................................................................................................. 96
Fig. 4.18. Measured results of the bandwidth reconfigurable filter with diode in the ON-
state, diode OFF-states and simple microstrip line. .................................................. 97
Fig. 5.1. Electric field diagram of a microstrip transmission line. .................................. 100
Fig. 5.2. Electric field diagram of a broadside and edge coupling of the EBG to a
microstrip transmission line. ................................................................................... 100
Fig. 5.3. Cross-sectional view of multilayer broadside coupled EBG band stop filter. .. 101
Fig. 5.4. Broadside coupled EBG band stop filter with 3 EBG cells placed longitudinally.
................................................................................................................................. 101
Fig. 5.5. Simulated results of the broadside coupled EBG band stop filter with variations
in number of cells in the longitudinal direction. ..................................................... 102
Fig. 5.6. Broadside coupled EBG band stop filter with 3 EBG cells placed transverse to
the line. .................................................................................................................... 103
Fig. 5.7. Simulated results of the broadside coupled EBG band stop filter with variations
in number of cells in the transverse direction. ........................................................ 103
Fig. 5.8. Surface current plots of a broadside-coupled EBG bandstop filter with 3-EBG
cells in transverse-direction at (a) 2.832 GHz (b) 4.94 GHz and (c) 5.76 GHz. ..... 104
xviii
Fig. 5.9. Comparision of edge coupled and broadside coupled EBG band stop filter. ... 105
Fig. 5.10. (a) Cross sectional view of the BPF. (b) Photograph of fabricated top and
middle layer of the BPF, printed on either sides of 0.127 mm thick substrate. (All
dimensions are in mm.) ........................................................................................... 106
Fig. 5.11. Transmission characteristics of the BPF with variations in J values. ............ 107
Fig. 5.12. Simulated S11 of the BPF with J=11 mm. ...................................................... 108
Fig. 5.13. Measured and simulated results of the proposed BPF and the reference filter.
................................................................................................................................. 109
Fig. 5.14. BPF with five cells. (a) Photograph of top and middle layers. (b) Measured and
simuated results. ...................................................................................................... 110
Fig. 5.15. Photograph of fabricated top layer and middle layer of the diplexer, printed on
either sides of 0.127 mm substrate. (All dimensions are in mm.) .......................... 111
Fig. 5.16. Surface current in diplexer at (a) 2.5 GHz and (b) 3.7 GHz. .......................... 113
Fig. 5.17. Measured and simulated results of the diplexer. ............................................ 113
Fig. 5.18. Diplexer measurement setup. ......................................................................... 114
Fig. 5.19. Measured results of the diplexer on spectrum analyzer. (a) Insertion loss. (b)
Isolation................................................................................................................... 115
Fig. 6.1. Unit cell (structure 'A'). (All dimensions are in mm.) ...................................... 118
Fig. 6.2. Simulation set up using CST Microwave Studio.............................................. 118
Fig. 6.3. Simulated results of unit cell (Fig. 6.1) with the simulation setup of Fig. 6.2. 119
Fig. 6.4 FSS measured results. ........................................................................................ 119
Fig. 6.5. Unit cell. (a) Structure 'B'. (b) Structure 'C'. (All dimensions are in mm.) ...... 120
Fig. 6.6. FSS characteristics of different unit cells. ........................................................ 121
Fig. 6.7. Schematic diagram of patch antenna. ............................................................... 124
Fig. 6.8. Simulated and measured |S11| of the patch antenna. ......................................... 124
xix
Fig. 6.9. Simulated and measured radiation pattern at 10.8 GHz of the patch antenna. (a)
E-plane (y-z plane - φ=90). (b) H-plane (x-z plane - φ=0). ................................. 125
Fig. 6.10. Patch antenna with FSS screen as superstrate. ............................................... 126
Fig. 6.11. Reflection coefficient of the patch antenna with and without FSS superstrate.
................................................................................................................................. 127
Fig. 6.12. Simulated radiation pattern at 10.8 GHz of the patch antenna with FSS
superstrate with variations in d. (a) E-plane pattern (y-z plane - φ=90). (b) H-plane
pattern (x-z plane - φ=0). ....................................................................................... 128
Fig. 6.13. Measured and simulated radiation pattern at 10.8 GHz of the patch antenna
with FSS superstrate. (a) E-plane pattern (y-z plane - φ=90). (b) H-plane pattern (x-z
plane - φ=0). .......................................................................................................... 129
Fig. 6.14. Measured radiation pattern at 10.8 GHz of the patch antenna with and without
FSS superstrate. (a) E-plane pattern (y-z plane - φ=90). (b) H-plane pattern (x-z
plane - φ=0). .......................................................................................................... 130
Fig. 6.15. Simulated radiation pattern of the patch antenna, patch antenna with dielctric
superstrate and patch antenna with FSS superstrate operating at 10.8 GHz. (a) E-
plane pattern (y-z plane - φ=90). (b) H-plane pattern (x-z plane - φ=0).............. 131
Fig. 6.16. Power flow top view of (a) patch antenna (b) patch antenna with dielectric
superstrae and (c) patch antenna with FSS superstrate. .......................................... 132
Fig. 6.17. Measured radiation pattern of the patch antenna, with and without FSS
superstrate operating at 6.7 GHz. (a) E-plane pattern (y-z plane - φ=90). (b) H-
plane pattern (x-z plane - φ=0). ............................................................................. 133
xxi
LIST OF TABLES
Table 2.1. Summary of results of various proposed structures loading a transmsion line.
................................................................................................................................... 43
Table 3.1. Summary of characteristics of band-notched UWB filters. ............................. 74
Table 6.1. Comparison table of FSS showing improvement in the antenna directivity. . 134