Improve the Accuracy of Power Level Measurements for Manufacturers

Manufacturer Reduces Risk and Improves Product Quality

Accuracy of power level measurements reduce false pass conditions and lower cost 

Company

An industry-leading military radar receiver manufacturer needed to deliver radar receivers that met tough new customer specifications. To ensure a quality product, the manufacturer reviewed many aspects of its test strategy, focused on ensuring its radar receivers could meet the new specifications. Radar receiver sensitivity is critical for electronic warfare (EW) applications. A radar receiver that is outside specifications will fail to decipher signals properly from long distances. This is not an option in military applications.

Company:

• Industry-leading military radar receiver manufacturer

Key Issues:

• Meet strict safety requirements for receiver performance
• Reduce false pass risk during radar receiver testing

Solutions:

• Demonstrated measurement uncertainty (MU) could be reduced from ±2.5 dB to ±0.12 dB
• Quantified risk and cost avoidance from reduced MU and improved power level accuracy

Results:

• Decreased false passes from 0.05% to <0.001%
• Reduced costs by an estimated $865,000 USD annually

Key Issues:

Risk of false passes

The aerospace and defense manufacturer needed to improve receiver sensitivity and the accuracy of its power level measurements in order to meet its design specifications and cost goals.

Receiver sensitivity is defined as the minimum signal level that is intelligible to the receiver or that can be demodulated effectively by the receiver. Sensitivity measurement accuracy relates directly to the power level accuracy of the low-level signal. An RF signal generator connected to the radar receiver antenna input generates the source signal used to determine receiver sensitivity. An RF signal generator with poor power level accuracy at very low power levels will cause inaccurate receiver sensitivity measurements. 

If the signal generator is out-of-specification, one of two measurement errors can occur. If the signal generator delivers a higher power level than indicated, the test may result in a false pass. The false pass results in the manufacturer shipping a product it believes meets customer receiver sensitivity requirements, when in fact, the actual sensitivity is several dB higher. Correspondingly, if the signal generator delivers an under-powered signal, a false fail occurs, and a “good unit” is re-worked, resulting in waste and increased cost. False pass results put this aerospace and defense company at great risk. 

Solution

Calibration ensures that test equipment performs to warranted specifications. Measurement uncertainty is a key contributor to false pass and false fail conditions. Reducing uncertainty starts with reviewing calibration data. Keysight evaluated the customer’s most recent signal generator calibration report and discovered that the third-party calibration service provider only verified the power level accuracy of the signal generator at 0 dBm. The calibration did not meet the requirements for the customer’s specific application, because the third party did not verify the lower power levels required for radar receiver testing. The much higher MU, as shown in Figure 3, meant the company was at significant risk of out-of-specification products passing quality assurance.

Keysight demonstrated a realistic level of drift for an uncalibrated power level parameter using a statistical model for random walk and known failure rates of the E8257D PSG signal generator. Figure 3 shows that the instrument drift for the power level accuracy of an E8257D, starting from the warranted specification of ±1.0 dBm, shifted to ±2.5 dB after five years.