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Testing and Troubleshooting
Digital RF Communications
Receiver Designs
Application Note 1314




I


Q




Wireless Test Solutions
Table of Contents


Page Page

1 Introduction 15 3. Troubleshooting Receiver Designs
2 1. Digital Radio Communications Systems 15 3.1 Troubleshooting Steps
3 1.1 Digital Radio Transmitter 15 3.2 Signal Impairments and Ways to Detect Them
3 1.2 Digital Radio Receiver 16 3.2.1 I/Q Impairments
3 1.2.1 I/Q Demodulator Receiver 17 3.2.2 Interfering Tone or Spur
4 1.2.2 Sampled IF Receiver 17 3.2.3 Incorrect Symbol Rate
4 1.2.3 Automatic Gain Control (AGC) 18 3.2.4 Baseband Filtering Problems
5 1.3 Filtering in Digital RF Communications Systems 19 3.2.5 IF Filter Tilt or Ripple
19 3.3 Table of Impairments Versus Parameters Affected
6 2. Receiver Performance Verification
Measurements 20 4. Summary
6 2.1 General Approach to Making Measurements
7 2.2 Measuring Bit Error Rate (BER) 20 5. Appendix: From Bit Error Rate (BER) to
Error Vector Magnitude (EVM)
8 2.3 In-Channel Testing
8 2.3.1 Measuring Sensitivity at a Specified BER 22 6. Symbols and Acronyms
9 2.3.2 Verifying Co-Channel Rejection
9 2.4 Out-of-Channel Testing
23 7. References
9 2.4.1 Verifying Spurious Immunity
10 2.4.2 Verifying Intermodulation Immunity
11 2.4.3 Measuring Adjacent and Alternate Channel
Selectivity
14 2.5 Fading Tests
14 2.6 Best Practices in Conducting Receiver Performance
Tests
Introduction


This application note presents the The digital radio receiver must
fundamental measurement principles extract highly variable RF signals
involved in testing and troubleshooting in the presence of interference and
digital RF communications receivers-- transform these signals into close
particularly those used in digital RF facsimiles of the original baseband
cellular systems. Measurement information. Several tests verify
setups are explained for the various receiver performance in the presence
receiver tests, and troubleshooting of interfering signals. These
tips are given. performance verification tests are
categorized as either in-channel or
The demand for ubiquitous wireless out-of-channel measurements.
communications is challenging the
physical limitations of current wire- This application note includes:
less communications systems.
Wireless systems must operate in a