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.
Chapter 1 – Repeater Site RF Systems Overview
1.1 Single Channel Duplexed System
1.2 Multi-Channel System
Chapter 2 – Surveying the Sites
2.1 Site Survey
2.2 Tower Mapping
2.3 RF Surveys
2.4 Tower Structural Survey
Chapter 3 – Essential Background
3.1 Noise in RF Systems
3.1.1 The Behaviour of Noise in RF Systems
3.2 Intermodulation
Chapter 4 – Sources of Interference at Shared Radio Sites
4.1 Transmitter Harmonics
4.2 Transmitter Sideband Noise
4.3 Transmitter Intermodulation
4.4 Receiver Blocking
4.5 Receiver Intermodulation
4.6 Minimising Site Interference by Antenna Placement and Frequency Planning
Chapter 5 – Antennas and Site Antenna Systems
5.1 The Isotropic Radiator
5.2 Antenna Specifications
5.3 Omni Directional Antennas
5.4 Directional Antennas
5.5 Down Tilt
5.6 Calculating the Isolation between Antennas on a Radio Tower:
5.7 Antenna System Topology
5.8 Site Antenna System Design Rules
Chapter 6 – Calculating the Interference Threshold
6.1 Calculating the Initial Receiver Sensitivity
6.2 Adding the Effect of Site Noise
6.3 Calculating the 1dB Interference Threshold
6.4 Accounting for Multiple Interference Mechanisms
6.5 Re-Calculating the Final Receiver Sensitivity
6.6 Summary
Chapter 7 – Duplexers
7.1 Types of Duplexers
7.2 Specifying Duplexer Design Requirements
7.3 Duplexers and Passive Intermodulation
Chapter 8 – Transmitter Combining Systems
8.1 Isolators
8.2 Cavity Filters
8.3 Types of Transmitter Combiner
8.4 Specifying Transmitter Combiner Design Requirements
8.5 Differences for Duplexed Multi-Channel Systems
8.6 Site Transmitter Combiner Design Rules
Chapter 9 – Receiver Multicoupling Systems
9.1 Receiver Sensitivity
9.2 Types of Receiver Multicoupler
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 Multi-Channel Systems
9.7 Site Receiver Multicoupler Design Rules
Chapter 10 – Power and Antenna System Monitors
10.1 Power Monitors
10.2 Antenna System Monitors
Chapter 11 – Transmission Line Systems
11.1 Transmission Line Systems for Multi-Channel 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
Chapter 12 – Design Example
12.1 Information Gathering
12.2 Antenna System Design
12.3 Calculating the Interference Threshold
12.4 Transmitter Combiner Design
12.5 Receiver Multicoupler Design
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