Designing RF Combining Systems for Shared Radio Sites

This book explores Radio Access Networks (RANs) within LMR systems, comprising base stations, mobile radios, and hand portable radios. These components facilitate communication among end users via a network of fixed base stations, antennas, and combining systems strategically placed across radio repeater sites throughout the coverage area. This resource also delves into the consequences of interference, highlighting the painstaking efforts required to diagnose and rectify interference issues through field testing and redesign. The central focus being on the design intricacies of base station antennas and combining systems at densely populated shared radio repeater sites. The book underscores how to identify potential sources of interference from co-located transmitters and receivers, effectively surveying sites to anticipate high-level interfering signals. This critical information forms the foundation for crafting base station antenna and combining systems that curtail interference, subsequently optimizing coverage and minimizing costs. Throughout its pages, the book lays out a detailed roadmap for designing LMR systems resilient to interference. By outlining essential principles and methodologies, the book guides practitioners in creating LMR networks that flawlessly align with end users'communication requirements. The resulting systems not only meet expectations but surpass them, offering the coverage area and communication quality demanded by public safety and utility organizations during critical operations. Ultimately, the book serves as an indispensable resource for engineers, designers, and professionals engaged in crafting LMR systems capable of delivering impeccable performance and reliability. Designing RF Combining Systems for Shared Radio Sites Contents Preface Introduction 1 Repeater Site RF Systems Overview 1.1 Single-Channel Duplexed System 1.2 Multichannel System 2Surveying the Sites 2.1 Site Survey 2.2 Tower Mapping 2.3 RF Surveys 2.3.1 Spectrum Monitoring 2.3.2 Noise Monitoring 2.4 Tower Structural Survey 3Essential Background 3.1 Noise in RF Systems 3.1.1 The Behavior of Noise in RF Systems 3.1.2 Noise Figure 3.2 IM 3.2.1 Third-Order IM and Third-Order Intercept Point 3.2.2 Third-Order IM with Unequal Input Signals 3.2.3 Third-Order IM with Three Input Signals 3.2.4 Fifth-Order IM and Fifth-Order IP 3.2.5 Fifth-Order IM with Unequal Input Signals 3.2.6 Fifth-Order IM with Three Input Signals 4Sources of Interference at Shared Radio Sites 4.1 Transmitter Harmonics 4.2 Transmitter Sideband Noise 4.3 Transmitter IM 4.4 Receiver Blocking 4.5 Receiver IM 4.6 Minimizing Site Interference by Antenna Placement and Frequency Planning 5Antennas and Site Antenna Systems 5.1 The Isotropic Radiator 5.2 Antenna Specifications 5.2.1 Directivity 5.2.2 Gain 5.2.3 Beamwidth 5.2.4 Reciprocity 5.2.5 E-Plane 5.2.6 H-Plane 5.2.7 Azimuth 5.3 Omnidirectional Antennas 5.3.1 Half-Wave Dipole 5.3.2 Half-Wave Folded Dipole 5.3.3 Quarter-Wave Monopole 5.3.4 Dipole Arrays 5.3.5 Binary Dipole Array 5.3.6 Elliptical Dipole Array 5.3.7 Offset Dipole Array 5.3.8 Colinear Antennas 5.3.9 Dual Antennas 5.4 Directional Antennas 5.4.1 Yagi-Uda 5.4.2 Panel Antennas 5.5 Down-Tilt 5.6 Calculating the Isolation Between Antennas on a Radio Tower 5.6.1 Isolation Between Horizontally Separated Antennas 5.6.2 Isolation Between Vertically Separated Antennas 5.6.3 Isolation Between Slant Separated Antennas 5.7 Antenna System Topology 5.8 Site Antenna System Design Rules Selected Bibliography 6Calculating the Interference Threshold 6.1 Calculating the Initial Receiver Sensitivity 6.2 Adding the Effect of Site Noise 6.3 Calculating the 1-dB Interference Threshold 6.4 Accounting for Multiple Interference Mechanisms 6.5 Recalculating the Final Receiver Sensitivity 6.6 Summary Reference 7Duplexers 7.1 Types of Duplexers 7.2 Specifying Duplexer Design Requirements 7.2.1 Transmit to Antenna Filter 7.2.2 Antenna to Receiver Filter 7.2.3 Final Duplexer Frequency Response 7.3 Duplexers and Passive IM Selected Bibliography 8Transmitter Combining Systems 8.1 Isolators 8.2 Cavity Filters 8.3 Types of Transmitter Combiners 8.3.1 T-Pass Transmitter Combiners 8.3.2 Star Combiners 8.3.3 Hybrid Combiners 8.3.4 Combinations of Different Types 8.4 Specifying Transmitter Combiner Design Requirements 8.5 Differences for Duplexed Multichannel Systems 8.6 Site Transmitter Combiner Design Rules Selected Bibliography 9Receiver Multicoupling Systems 9.1 Receiver Sensitivity 9.2 Types of Receiver Multicouplers 9.2.1 Standard Multicoupler 9.2.2 Channelized Multicoupler 9.2.3 Use of Crystal Filters in Channelized Multicouplers 9.3 Use of Tower Top Amplifiers in Receiver Multicouplers 9.4 Correctly Setting the Gain of Receiver Multicoupling Systems 9.5 Calculating Receiver Filter Requirements 9.6 Differences for Duplexed Multichannel Systems 9.7 Site Receiver Multicoupler Design Rules Selected Bibliography 10Power and Antenna System Monitors 10.1 Power Monitors 10.2 Antenna System Monitors References 11Transmission Line Systems 11.1 Transmission Line Systems for Multichannel Site RF System Designs 11.2 Transmission Line Systems for Single-Channel Duplexed RF System Designs 11.3 RF Surge Suppression Devices 11.4 Transmission Line Grounding Devices Selected Bibliography 12Design Example 12.1 Information Gathering 12.1.1 Site Survey 12.1.2 Tower Mapping 12.1.3 RF Survey 12.2 Antenna System Design 12.3 Calculating the Interference Threshold 12.4 Transmitter Combiner Design 12.5 Receiver Multicoupler Design 12.5.1 Gain Setting 12.5.2 Calculating the Receiver Filter Requirements 12.6 Antenna System Monitor 12.7 Transmission Line System 12.7.1 RF Surge Suppression Devices 12.7.2 Transmission Line Grounding Devices 12.8 The Finished Design 12.9 Concluding Remarks Selected Bibliography About the Author Index