The Future of The Signal Path, Patreon & Q/A


Since the creation of The Signal Path video blog in May of 2011 I have focused on producing the type content which is either difficult to find or difficult to learn. Despite being the foundation of human communication, RF and microwave electronics often seem like magic and my goal has been to demystify these concepts. The Signal Path blog provides a rich depth and breadth of electrical engineering topics and experiments. Equipment reviews and repairs are always accompanied with research and industry relevant experiments and tutorials. The aim of The Signal Path is to provide free education to everyone across the world, possibly the greatest gift from a human to another.

Any support you offer to The Signal Path will be put back into lab maintenance, improving the quality and frequency of video production and acquiring components to further diversify content production. As of August 2016, The Signal Path has produced over 66 hour of original material.

On behalf of all viewers from around the world I want to thank you for supporting The Signal Path.

Shahriar Shahramian, Ph.D. Owner & Host
The Signal Path

Teardown & Analysis of an Agilent 86109B Optical/Electrical DCA-X Oscilloscope Module


In this episode Shahriar presents the inner workings of an Agilent 86109B optical/electrical DCA-X oscilloscope module. This particular model offers up to 50GHz of electrical bandwidth and an optical input capable of receiving up to 40Gb/s data rates. The differences between a real-time and sub-sampling oscilloscopes are presented with focus on ADC resolution, signal periodicity requirements and input bandwidth. The block diagram of the module as well as a sub-sampling oscilloscope is also presented.

The teardown of the module shows various components such as samplers, O/E conversion block, impulse generator as well as a step-recovery diode driver. I/O interfaces as well as various analog blocks are also shown. Several modules are further disassembled to observe the inner semiconductor designs under the microscope.

Tutorial on High-Power Balanced & Doherty Microwave Amplifiers

Balanced Amplifier

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.

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