In this episode Shahriar investigates a faulty Agilent E8257D analog signal generator. These high-performance synthesizers are in wide use & high demand. The instrument fails self test procedure. The error code "704 Filter Test" generally points to the Frac-N module which also houses the modulus divider circuits. This portion is responsible for generating frequencies below 3.2GHz and uses an integer divider, filter bank and variable gain amplifiers.

Using a 12GHz active probe, the signal path (pun intended) is verified step by step from the input to the suspect sub-system all the way to the output of the Frac-N board. The fault is ultimately traces to a custom MMIC module with an Agilent GaAs FET amplifier circuit. A new replacement IC is sourced from eBay which clears the fault. The phase noise performance of the unit is also verified at 2GHz using an Agilent E5052B signal source analyzer.

Lastly, the faulty MMIC module is de-capped and the die is analyzed under a high power microscope with various imaging techniques.

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