Microwave Radio Transmission Design Guide
A practical guide for engineers planning or building a microwave-based transmission system, with a special eye toward international standards.
TABLE OF CONTENTS Microwave Radio Transmission Design Guide
Section 7.2: Causes of Interference
7.2 Causes of Interference
The cause of interference can be divided into two categories: internal and external.
7.2.1 Internal Causes
Internal causes are those causes that relate to the equipment at the site itself. This includes radio equipment parameters such as the transmit and receive local oscillators (LOs) and filter selectivities. It also includes internal aspectsof the system design such as reflections from the antenna/feeder system, the transmit/receive (T/R) spacing, the F/B ratio of the antennas at a repeater station, and cochannel and adjacent channel interference from the system itself. These factors are all basically under the system designer's control. Good equipment with stable oscillators and steep filter responses is required. In addition, international channel plans should be chosen that incorporate stringent interference limitations. Finally, the antennas must be chosen to meet the interference requirements.
7.2.2 External Causes
External causes result from sources that are seldom under the designers control. These include interference from other systems that are already installed and interference from other services such as satellites. It also includes interference from a distant site that forms part of the same route this aspect can be controlled by the system designer.
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