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Agilent Technologies
Wireless Test Solutions
Application Note 1313
I
Q
Testing and Troubleshooting
Digital RF Communications
Transmitter Designs
Introduction The demand for ubiquitous wireless communications is challenging the physical
constraints placed upon current wireless communications systems. In addition,
wireless customers expect wireline quality from their service providers. Service
providers have invested a lot in a very limited slice of the radio spectrum.
Consequently, network equipment manufacturers must produce wireless systems
that can be quickly deployed and provide bandwidth-efficient communications.
At early stages of equipment design, rigorous testing is performed to ensure
system interoperability. The increasingly complex nature of digital modulation is
placing additional pressure on design teams, already faced with tight project
deadlines. Not only must the designer test to conformance; he must also quickly
infer possible problem causes from measurement results.
The objective of this application note is to help you understand why the
different transmitter tests are important and how they identify the most common
impairments in transmitter designs.
The application note focuses on cellular communications transmitters, although
some of the measurements and problems described may also apply to other
digital communications systems.
This application note covers the following topics:
1. How digital communications transmitters work.
2. How to test transmitters and what test equipment characteristics
are important.
3. The common impairments of a transmitter and how to
troubleshoot them.
The following information is also included as reference material: