Real-Time Spectrum Analysis For WLAN And Combo Devices

This application note focuses on key measurement issues for WLAN and combo devices, how the RTSA addresses those issues, and why traditional signal analyzers are not adequate. We begin with a brief overview of the key concepts of real-time spectrum analysis, including the ability to flexibly trigger on RF signals, seamlessly capture them in memory, and perform time-correlated multi-domain analysis based on a variety of wireless standards. Next, the WLAN measurement analysis software available for the RSA3408A Real-Time Spectrum Analyzer is reviewed. Finally, we explore some of the real-world problems encountered with wireless combo devices that can be solved using the RSA3408A. Issues like packet collisions between Bluetooth and WLAN devices, internal interference caused by poor filtering and poor shielding in a GSM/WLAN device, and the unwanted interactions between RF packets and high-speed digital logic circuits are explored.

Introduction
Wireless combo devices that incorporate multiple RF communications protocols such as Wireless Local Area Network (WLAN), Bluetooth and 3G cellular standards are becoming increasingly popular, enhancing connectivity and performance in the wireless marketplace. Combo devices present a challenging set of signal measurement issues for the wireless engineer, whether validating a reference design or working on the next generation modulation format. Packet signal transients, asynchronous packet collisions and a variety of self-interference modes can be difficult or impossible to diagnose with traditional signal analyzers. The Tektronix Real-Time Spectrum Analyzer (RTSA) offers a unique and practical solution to many of these difficult signal measurement problems.