A Practical Design of Lumped, Semi-lumped & Microwave Cavity Filters (eBook)

Dhanasekharan Natarajan, Electronics Engineer from College of Engineering, Guindy, Chennai in 1970, obtained his post-graduate in Engineering Production from the University of Birmingham, UK in 1984.  He retired as Asst. Professor in RV College of Engineering, Bangalore.  His earlier professional achievements at Bharat Electronics and Radiall Protectron include Application of modern Q&R techniques for defence equipments, Designing and implementing computerized Quality Management System, Designing software for Optical interferometer and Design/manufacturing of lumped, semi-lumped and microwave cavity filters using self-developed software. 

Preface 6
Acknowledgments 9
Contents 10
1 Introduction to RF Filters 15
Abstract 15
1.1…Need for Filters 15
1.2…Filtering Circuits 16
1.3…Types of Filters 17
1.3.1 Low Pass FiltersLow Pass Filter 17
1.3.2 High Pass FiltersHigh Pass Filter 18
1.3.3 Band Pass FiltersBand Pass Filter 18
1.3.4 Band Reject FiltersBand Reject Filter 19
1.4…Application of RF Filters 20
References 20
2 RF Filter Terms 21
Abstract 21
2.1…Introduction 21
2.2…Impedance 22
2.2.1 Definition 22
2.2.2 Load Resistor at Radio Frequency 22
2.2.3 Standard Terminations 24
2.3…RF Transmission Line 24
2.3.1 Definition 24
2.3.2 Types of Transmission Lines 25
2.4…Coaxial Transmission Lines 25
2.4.1 Construction and Characteristics 25
2.4.2 Standard CoaxialRF transmission linecoaxial Air Lines 26
2.5…Microstrip/Stripline Transmission Lines 27
2.6…Characteristic Impedance 27
2.7…VSWRVSWR 28
2.7.1 Maximum Power Transfer 28
2.7.2 Practical Significance of VSWRVSWR 29
2.8…VSWRVSWR: Open Circuited Load 29
2.8.1 Relationship Between Incident and Reflected Voltages 30
2.8.2 Instantaneous Voltages of Incident, Reflected and Resultant Waves 30
2.8.3 Standing Voltage Wave in Slotted Line 33
2.9…VSWRVSWR: Short Circuited Load 34
2.9.1 Relationship Between Incident and Reflected Voltages 34
2.9.2 Instantaneous Voltages of Incident, Reflected and Resultant Waves 34
2.10…VSWRVSWR: Matched 50 Omega Load 36
2.11…VSWRVSWR: Infinitely Long 50 Omega Cable as Load 37
2.12…VSWRVSWR: Partially Matched Load 38
References 39
3 Requirements of RF Filter 40
Abstract 40
3.1…Sub-Contracting Process 40
3.2…Sample Electrical Specifications of Filters 40
3.3…Pass Band 42
3.4…Pass Band Ripple 42
3.5…Insertion Loss 43
3.6…Return Loss 44
3.7…Cut-Off Frequency 45
3.8…Rejection 46
3.9…Graphical Representations 46
3.10…Mechanical Specifications 47
3.10.1 Dimensions (Outline) and Weight 48
3.10.2 Input/Output Connections 49
3.10.3 Finish 49
3.11…Environmental Specifications 49
3.12…Additional Specifications 50
4 RF Filter Design Technologies 51
Abstract 51
4.1…Technologies 51
4.2…Lumped RF Filters 52
4.2.1 Low Pass and High PassFilters, TypesHigh Pass Filters 52
4.2.2 Band Pass and Band RejectFilters, TypesBand Reject Filters 53
4.3…Semi-Lumped RF Filters 54
4.3.1 Distributed Capacitance 55
4.3.2 Concept of Semi-Lumped RF Filter 55
4.4…Microwave Cavity Filters 56
4.4.1 Resonance in Microwave CoaxialRF transmission LineCoaxial Cavity 56
4.4.2 Combline and Iris-Coupled Cavity Filters 57
4.4.3 Power Handling Capacity 58
4.5…Combline Band Pass Filters 58
4.5.1 Structure 58
4.5.2 Equivalent Circuit 59
4.5.3 Insertion Loss 60
4.6…Iris-Coupled Band Pass Filters 60
4.7…Cavity Filters with Dielectric Resonators 61
4.8…Microstrip and Stripline Filters 62
4.8.1 Materials 62
4.8.2 Basic Microstrip 62
4.8.3 Basic Stripline 63
4.8.4 Computer Aids for Filter Design 63
References 64
5 Planning the Design of RF Filters 66
Abstract 66
5.1…Need for Planning Design 66
5.1.1 BenefitsBenefits of Value Added Functional DesignDesign Approach, RF FiltersValue Added Functional Design 67
5.2…Planning Design Phase 68
5.3…Understanding Customer Requirements 69
5.4…Setting Internal Specifications 69
5.4.1 Need for Internal Specifications 69
5.4.2 Statistical Method of Setting Internal SpecificationsDesign Process ActivitiesSetting Internal Specifications 70
5.4.3 Recommended Internal Specification Limits 72
5.5…Computations of Filter Parameters 73
5.6…Design Drawings and Their Review 74
5.6.1 Sources of Data for Review 74
5.6.1.1 Failure Data on Similar RF Filters 74
5.6.1.2 Suggestion Awards 75
5.6.1.3 Informal Discussions 75
5.6.1.4 Manufacturing Drawings 76
5.6.1.5 Formal Review of Design Drawings 76
5.7…Internal Testing and Validation 76
Reference 77
6 Design of Lumped and Semi-Lumped RF Filters 78
Abstract 78
6.1…Introduction 78
6.2…Lumped RF Filters 79
6.2.1 Selection of Filter Parts 79
6.3…Illustrated Design of Lumped RF Filter 80
6.3.1 Computational Steps for Filter Design Parameters 80
6.3.2 Number of Filter Elements 81
6.3.2.1 Calculate /varvec{/omega}^{/prime} //varvec{/omega} _{1} ^{/prime } 81
6.3.2.2 Calculate epsilon 81
6.3.2.3 Calculate the Number of Filter Elements, n 81
6.3.3 Values of Filter Elementsvalues of filter elements 81
6.3.3.1 Compute g-Values 81
6.3.3.2 Compute the Normalized Values of Filter Elementsvalues of filter elements 82
6.3.3.3 Compute the Actual Values of Filter Elementsvalues of filter elements 82
6.3.4 Layout Design for Filter Elements layout design, filter elements 83
6.3.5 End CouplingEnd coupling 84
6.3.6 Tuningtuning of Lumped RF Filter 85
6.4…Illustrated Design of Tubular Filter 85
6.4.1 Number of Filter Elements 86
6.4.2 Values of Tubular Filter Elements 87
6.4.3 Realisation of Tubular Filter 87
6.4.4 Tuningtuning of Tubular Filter 89
6.5…Design of CoilsDesign Of Coils 90
References 90
7 Design of Microwave Cavity Filters 91
Abstract 91
7.1…Introduction 91
7.2…Combline Band Pass FilterBand Pass Filter 92
7.2.1 Cavity Block 92
7.2.2 Resonators 92
7.2.3 Cover Plate 93
7.2.4 Other Piece Parts 93
7.2.5 Materials and Finish of Parts 94
7.3…Illustrated Design of Combline Filter 94
7.3.1 Computational Steps for Combline Filter 95
7.3.2 Number of Filter Sections 96
7.3.2.1 Calculate omega 96
7.3.2.2 Calculate omega vprime/ omega 1vprime 96
7.3.2.3 Calculate epsilon 96
7.3.2.4 Calculate the Number of Filter Sections, n 96
7.3.3 Resonator Length 97
7.3.4 Width and Thickness of Rectangular Resonators 97
7.3.4.1 Compute (bj/YA) for j = 1 to n 97
7.3.4.2 Compute g-values 97
7.3.4.3 Compute GT/YA and Jj,j+1/YA 98
7.3.4.4 Normalized Capacitance/Unit Length (Line and Ground) 99
7.3.4.5 Normalised Capacitance/Unit Length (Adjacent Resonators) 100
7.3.4.6 Obtain (s/b) and ( {/hbox{C}}_{/rm{fe}}^{/prime } //varepsilon ) From Graphs 101
7.3.4.7 Obtaining (s0, 1/b) from (C0, 1/ epsilon ) 102
7.3.4.8 Obtain [(Cvprimefe)j,j+1/ epsilon )] From (s0,1/b) 102
7.3.4.9 Computerization of the Graphs 104
7.3.4.10 Polynomials for the Graph, [( Delta C)j,j+1/ epsilon ] i.e. Cj,j+1/ epsilon Vs sj,j+1/b 104
7.3.4.11 Polynomials for the Graph, sj,j+1/b Vs [(Cprimefe)j,j+1/ epsilon ] 105
7.3.4.12 Calculate Normalized Width of Rectangular Resonators 106
7.3.4.13 Decide the Width of Cavity 107
7.3.4.14 Calculate the Thickness and Width of Rectangular Resonators 107
7.3.5 Rectangular to Cylindrical Resonators 107
7.3.6 Spacing Between ResonatorsSpacing Between Resonators 108
7.3.7 Length of Cavity 109
7.3.8 Capacitance for tuningMicrowave cavity filters, designtuningTuning Resonators 109
7.3.9 Height of Cavity 110
7.4…Iris-Coupled Band Pass FilterBand Pass Filters 112
7.4.1 Structure and Parts 112
7.5…Illustrated Design of Iris-Coupled Filters 112
7.5.1 Computational Steps for Filter Design Parameters 113
7.5.2 Number of Filter Sections 114
7.5.3 Diameter and Height of Cavity and Resonators 114
7.5.4 Width, Height and Thickness of Irises 115
7.5.4.1 Calculate g-Values 115
7.5.4.2 Calculate Coupling Reactance, (Xj,j+1)m 116
7.5.4.3 Calculate Initial Magnetic Polarizabilities of the Irises, (Mj,j+1) 116
7.5.4.4 Initial Width and Length of Irises From Graph 117
7.5.4.5 Calculate Compensated Magnetic Polarizabilities of the Irises, (Mj,j+1)comp 119
7.5.4.6 Final Width and Length of Irises From Graph 119
7.6…End Coupling in Cavity Band Pass Filters 121
7.6.1 Probe Coupling 121
7.6.2 Tag Coupling 122
7.7…Tuning of Cavity Band Pass Filterband pass filters 122
7.7.1 Adjustment Available for TuningtuningMicrowave cavity filters, designtuning 122
7.7.2 Tuning Procedure 123
7.7.3 TuningTuning of Filters in Frequency and Time Domains 124
References 124
8 Practical Expertise for Filter Design 125
Abstract 125
8.1…Opportunities for Learning 125
8.2…Visual Examination of Assembled PCBs 126
8.3…Preservation of Silver Plated Parts 126
8.4…Precautions for Chip Ceramic Capacitors 126
8.5…Centre Contact Retention in Coaxial Connectors 127
8.6…Mechanical Designs 128
8.7…TuningTuning of Filters 128
8.8…‘Cut and Try’ Method 129
8.9…Cross Coupling for Steep Roll Down Filters 129
8.10…Air Gap Between Resonator and TuningTuning Screw 130
8.11…Duplexers 131
8.12…Developing Filter Design Software 131
References 133
Appendix AModes of Propagation 134
TEM Mode 134
TM Mode 134
TE Mode 135
Appendix BStatistical Analysis on RF Filter Characteristics 137
Normal Distribution For Return Loss 137
Setting Internal Specification For Return Loss 139
Appendix CCoaxial Connectors for RF Filters 141
Coaxial Plugs and Sockets, Panel Mountable 141
Feed Through Terminals 142
Cabling Type Plugs and Sockets 142
In-Series and Between Series Coaxial Adapters 143
About the Author 144
Index 145