Introduction

Designers and manufacturers of active devices often need to control the power level at the test port1 of their power-sensitive devices, but find dif- ficulty in overcoming insertion losses. The insertion losses occur as a result of connecting components in the measurement path between the source and the DUT. The Agilent Technologies 8510C is a microwave network analyzer2 capable of setting and controlling the power level at the test port. This product note reviews the implementation and operational considerations of the 8510C’s test port power flatness-correction feature.

The 8510C performs a flatness-correction cali- bration by measuring the test port power level using an Agilent power meter and creates a table of power corrections versus frequency. The power meter then stores the table into an Agilent 8360 series synthesized sweeper.3 When the test port flatness correction is enabled, the source will adjust its output power to compensate for path losses at each measurement point in the frequency span.

Power flatness correction is useful for characteriz- ing active devices by allowing measurements of absolute power, gain versus input power, and swept-frequency gain compression. Swept-power gain compression measurements are possible in the power domain with the flatness correction enabled.

The 8510XF measurement system is capable of lev- eling and controlling the test port power between 45 MHz and 110 GHz without requiring a power calibration for each measurement. When power lev- eling is enabled, the test port power variation is typically less than ±1 dB over the full frequency sweep, with 20 dB of adjustable power. For more information regarding power leveling in the Agilent 8510XF, refer to product note 8510XF-1, literature number 5968-5270E.

1.In this document, “test port” will refer to the point in the system where the test device is connected. This may be port 1 or port 2 of any 8510 coaxial-based test set or the end of a cable or adapter that is attached to the DUT.

2.8510B network analyzers with revision B.06 or later may also be used to achieve constant test port power levels. To obtain the latest firmware revision order the 11575F upgrade kit.

3.Any 8360 synthesized sweeper with firmware revision of September 25, 1990 or earlier must be upgraded. To upgrade your 8360 to the latest firmware revision, order part number 08360-60167.