Archive for General

Teardown and Repair of an Agilent E4433B ESG-D Synthesized Signal Generator


In this episode Shahriar repairs an Agilent E4433B ESG-D Synthesized Signal Generator. This 4GHz unit shows the “UNLEVEL” error for all frequencies and at all output power levels. After a close look at the system block diagram the fault is traced to the main Output RF board.

The Output RF board is equipped with various amplifiers, electronic attenuators, I/Q mixers, heterodyne paths and final PA. By using soldered SMA cables to various points in the signal path, the fault is traced to an internal amplifier chain which is likely made of a MESFET or JFET transistor. Since this part is obsolete, an RFMD GaAs hybrid amplifier is used in its place. The biasing network and matching networks need to be modified to accommodate this change. The repaired unit is then verified for functionality and performance by measuring a QAM constellation output signal.

Agilent 53131A Universal Counter Upgrade OPT-030 Analysis and Experiments


In this episode, Shahriar upgrades an Agilent 53131A Universal Counter with the OPT-030 which extends its frequency range from 225MHz to 3GHz. The upgrade kit is a replica PCB intended to emulate the behavior of the original Agilent branded option.

The PCB is examined carefully with attention to microwave layout techniques along the signal path. The datasheet of all the parts are reviewed and the reverse-engineered block diagram of the PCB is presented. The expected behavior of the PCB is then measured in both small-signal and large-signal operation using an active 3GHz probe. The PCB is then installed inside the unit and the functionality of the instrument is verified within its specifications. All the documents presented in the video can be found here.

Tutorial on Microwave and mm-Wave Components and Modules


In this episode Shahriar demos various microwave and mm-wave connectors, components and modules. The purpose of this video is to help new engineers become familiarized with microwave components and help reduce the chance of component damage and failure.

This video demonstrates microwave connectors (BNC, SMA, 3.5mm, 2.92mm (K), 2.4mm, 1.85mm (V), 1.0mm), interfacing instructions, attenuators, power splitters (both resistive and reactive), phase shifters, mm-wave cables, AC coupling caps, Bias-Ts and their principle of operation, mixers, tuning stubs, couplers, switched attenuators, microwave filters, multipliers, amplifiers, coaxial to waveguide converters, waveguide components including horn antennas, and directional couplers. The video also demonstrates Cascade GSG probes and GGB custom composite RF probes. The documents for this video can be downloaded from here.


Teardown and Repair of an Agilent E4421A Synthesized Signal Generator


In this episode Shahriar repairs an Agilent E4421A synthesized signal generator purchased from eBay. The unit displays the error messages “UNLOCK” and “UNLEVEL”. The cause of failure is investigated and traced. Alongside the repair efforts, the internal construction and components of the synthesizer are also presented. A short tutorial on the advantages and disadvantages of using a Darlington transistor is also presented as well as the schematic of a simple Darlington based voltage regulator. The documents for this tutorial can be found here.


Tutorial and Experiments on Magnetic Levitation


In this episode Shahriar demonstrates one of the simplest magnetic levitation circuits. First, the basic concept of magnetic levitation is examined. Two different methods of detecting the location of the levitating object is presented and the Hall effect sensor method is chosen. A semi-digital overall system is implemented where a PWM control IC is employed to control the magnetic field strength. The block diagram and functionality of this IC is presented. Finally, the schematic of a dual-Hall effect sensor solution is presented. The circuit is built and tested in both open-loop and close-loop configuration. Magnetic levitation is demonstrated with the capability of adjusting the levitation location. The schematic of circuit can be downloaded here and the electromagnet can be purchased from here.