RF Receiver Overload Test: Maximum Tolerable Power

This document outlines the basics of RF receiver overload measurement, focusing on the test setup used to verify and test a receiver’s maximum tolerable power. This specification is often expressed in Device Under Test (DUT) test requirements as:

• “The receiver should be capable of decoding a maximum on-channel signal of -30dBm.”
• “The receiver should tolerate a maximum signal of 0dBm without damage.”

This test aims to verify the RF receiver’s ability to withstand the maximum input power without affecting its normal functioning within the system.

Test Setup for Receiver Maximum Power Measurement

The following image illustrates the test setup:

Figure 1: Test setup used to determine the maximum tolerable signal of the DUT.

The equipment required for this measurement includes:

• RF Signal Generator or Sweep Oscillator
• VSA (Vector Signal Analyzer) or RF Power Meter
• Directional Coupler
• Variable RF Attenuator

Test Procedure

The following procedure is followed for the measurement:

1. Setup: Assemble the test setup as shown in Figure 1.
2. Initial Settings: Set the nominal RF frequency and power output in the RF signal generator or sweep oscillator.
3. DUT Verification: Verify that the Device Under Test (DUT) is functioning correctly under normal operating conditions before beginning the high-power test.
4. Power Increase: Gradually increase the power level of the signal generator or decrease the attenuation setting in the variable RF attenuator. Do this slowly until you reach the maximum limit specified in the relevant specification/standard.
5. Maximum Limit Check: After reaching the maximum limit (e.g., 0 dBm), thoroughly verify the normal functioning of the DUT.
6. Pass/Fail Determination: If the DUT continues to operate correctly at this maximum power level, the test is considered passed.

Special Considerations

In some DUTs, verifying normal operation can be tricky. This is especially true when the DUT requires an initial handshake or synchronization process to be completed. Examples include:

• Mobile subscribers in GSM or WiMAX networks
• Stations (clients) in WLAN networks

In these scenarios:

• GSM/WiMAX: The subscriber needs to synchronize with the respective base station to verify proper system operation.
• WLAN: The client station needs to synchronize with the Access Point (AP) before it can be confirmed that it is working correctly.

To facilitate this type of testing, a Base Station Emulator or Access Point is used in place of the standard signal generator/sweep oscillator. This allows the DUT to properly synchronize and establish a connection, enabling a more realistic assessment of its performance under high-power conditions.