RF Testing in Embedded Systems

Overview

RF testing requires devices to support a dedicated test mode that allows controlled configuration of radio parameters.

Typical capabilities include:

  • Fixed channel selection
  • TX power configuration
  • Bandwidth and modulation selection
  • RX-only mode (disable transmission)
  • Continuous transmission mode

These capabilities are required for both wireless interfaces when multiple radios are integrated.

Test Mode Implementation

RF test mode is typically implemented based on vendor documentation.

In this case, the implementation follows:

  • AN14114 – WiFi/Bluetooth RF Test Mode Application Note (NXP)

This document describes:

  • Required commands
  • Configuration parameters
  • Execution sequences for both WiFi and Bluetooth

Implementation may require:

  • Driver updates or extensions
  • Low-level configuration interfaces
  • Command-based control (e.g., scripts)

Scripts and Automation

To simplify testing:

  • Scripts are used to configure test parameters
  • Same scripts can often be reused across platforms using identical hardware
  • Automation ensures repeatability and reduces human error

Test Scope Considerations

To optimize testing:

  • Limit frequency bands where possible
  • Avoid unnecessary test complexity
  • Focus on realistic usage scenarios

Example decisions:

  • Use only commonly used frequency bands
  • Select one wireless mode if multiple exist

Test Setup

RF testing can often be performed with minimal system setup:

  • Device powered standalone or via host system
  • No full system integration required
  • Focus is on radio performance

Example Configuration Areas

WiFi

  • Bandwidth (e.g., 20 MHz default)
  • TX power (e.g., maximum allowed)
  • Data rates and modulation
  • Channel selection

Bluetooth

  • Mode selection (e.g., Classic or Low Energy)
  • TX power
  • Packet type and payload
  • Channel configuration

RF Receiver Blocking Test

Concept

The RF Receiver Blocking test verifies that the device can maintain communication under interference.

Typical procedure:

  1. Device operates in normal client mode
  2. Connects to a measurement access point
  3. Interfering signals are introduced
  4. Packet Error Rate (PER) is measured

Notes

  • This test evaluates real communication performance
  • It differs from controlled RF test mode
  • Requires specialized test equipment

Summary

  • RF test mode is essential for compliance and validation
  • Vendor application notes (e.g., AN14114) are key references
  • Automation and scripting improve efficiency
  • Blocking tests evaluate real-world robustness under interference