Tutorial on High-Power Balanced & Doherty Microwave Amplifiers

In this episode Shahriar demonstrates the architecture and design considerations for high-power microwave amplifiers. Two architectures are presented, the balanced and Doherty microwave amplifiers. The block diagram, circuit properties and the pros/cons of each architecture are presented. Two available high-power amplifiers modules for cellular applications are also examined. The PCBs show an implementation instance of each amplifier type capable of delivering 100W of RF power. The datasheet of various components as well as an overall system structure are also presented.

Teardown & Repair of an Agilent 54845A 1.5GHz 8GS/s Infinium Oscilloscope

In this episode Shahriar repairs an Agilent 54845A oscilloscope with an intermittent failure. The instrument occasionally fails self-calibration and the displayed waveform shows undesired spurious activities. The teardown of the instrument reveals customized front-end section coupled into a ceramic-substrate ADC ASIC designed by Agilent. The packaged ADCs are placed in sockets. The ICs are removed and the ceramic carrier is cleaned; this resolves the intermittent problem with the channels. The architecture of the scope is also presented. The functionality of the scope is verified through self-calibration, self-test and measurement of various waveform.

Teardown, Repair & Experiments of an Agilent E7495B 2.7GHz Base Station Test Set

In this episode Shahriar repairs an Agilent E7495B 2.7GHz base-station test set capable of VSWR measurements as well as spectrum analysis. This particular unit is well equipped with many options however does not power on. A full teardown of the instrument reveals a faulty DC power conditioning module. The input filtering capacitor has failed. After component replacement, the unit is re-assembled. The functionality of the instrument is verified as well as a few quick experiments demonstrating various options.

Fluke PM6680B Frequency Counter 10MHz OCXO Reference Upgrade Module

In this short episode Shahriar upgrades the recently repaired Fluke PM6680B with a new OCXO design by Dan Watson. The design of the module is examined as well various considerations for providing ultra clean 10MHz reference for instrumentation.  After module installation the unit functionality is verified. More information about the module is available here and here.

LCD Screen Backlight CCFL to LED Replacement

In this short episode Shahriar demonstrated how to convert a CCFL backlight to an LED backlight on an Anritsu Network Analyzer. The construction of the existing LCD screen along with the new LED driver board are presented. The LED board provides an analog pin for brightness control. The final result is very impressive!

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