Wireless Test Solutions.qxp

Application Note 1313 2 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: • A detailed troubleshooting procedure (Appendix A). • A table of instrument capabilities (Appendix B). • A glossary of terms. • A list of reference literature.