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.
In this episode Shahriar presents 5 interesting things from around the lab! The topics range from optics to microwave components. The video is organized at follows:
00:38 - Pasternak 12GHz-14GHz continuously tuneable 20dB attenuator. How does it work?
11:02 - Ultra-high efficiency triple jacket glass distillation dewar.
14:59 - AWG PLC 8-way WDM splitter on 50GHz channels.
24:15 - PCB embedded D-Band waveguide with Vivaldi launch end-points.
28:45 - Hidden security features of the Canadian currency.
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https://www.youtube.com/watch?v=cWkgWCxhJJk
In this episode Shahriar repairs an Agilent 8163A Lightwave Multimeter. The instrument shows a flickering screen and does not boot. The teardown of the unit is presented along with a general instrument architecture. The power supply is verified for functionality and the instrument simply comes back to life on its own! It most likely has had a poor internal connection which is resolved after reassembly.
Two modules are also presented, a dual-input InGaAs power sensor module as well as a dual Fabry-Perrot laser module. The teardown and analysis of both are presented along with wavelength and spectrum measurements.
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https://www.youtube.com/watch?v=ZLeZcbf_E0A
In this episode Shahriar examines a failed Agilent 1169A 12GHz Smart Active Probe. The probe does not get recognized by the oscilloscope and therefore cannot be calibrated. The instrument uses an I2C interface to the probe to download the probe's specifications and characteristics.
The probe teardown reveals a simple I2C EEPROM IC. After removing the IC it becomes clear that the chip is damaged and must be replaced. A duplicate probe is used to copy the EEPROM data onto a new IC which revives the probe. With the help of the community, the CRC checksum code is discovered and the probe is assigned a new serial number.
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https://www.youtube.com/watch?v=KKItbyz6564
In this episode (Part 1/3) Shahriar explores the principle operation of a camera flash circuit. The flash circuit is analyzed at the schematic level and through measurements. He then moves on to power a nixie tube using this circuit and calculates the efficiency of the DC-DC converter for this type of application. There is also a little quiz in this episode! Whoever solves the quiz will chose the topic of the next video.
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https://www.youtube.com/watch?v=8YuDlhMMIaw
In this Episode Shahriar attempts to answer a fundamental scientific question, within the budget of The Signal Path. In this case, the question that has boggles scientists since the invention of LEDs: How many LEDs can you light up using a hot dog?!
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In this episode Shahriar reviews the Rohde & Schwarz 4.0GHz Spectrum Rider FPH. The new design of the FPH series is aimed for ease of use in outdoor situations as well as offering several software features for data collection, analysis and debugging of standard wireless communication protocols. The review is organized as follows:
1:10 – Model comparison of R&S portable spectrum analyzers.
5:44 – Instrument hardware overview and GUI characteristics.
22:24 – Using the FPH Spectrum Rider to analyze unknown wireless signals including a multi-tone, QPSK modulated signal, AM/FM demodulation analysis and frequency hopping.
46:46 – FPH teardown and analysis.
55:33 – Overview of the Instrument View remote connection software.
57:42 – Concluding remarks.
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In this episode Shahriar investigates an Agilent E4981A high-speed capacitance meter which fails self-test during startup. The instrument reports a series of errors associated with the CPU board. The teardown reveals a multi-board construction where the main analog assembly employs an FPGA for control and interface to the main CPU board. The unit has a disconnected ribbon cable between the analog board and the main CPU assembly. After correcting the problem the instrument completes self-test without errors.
After the repair the unit is used to measure several known capacitors for functionality verification. Finally the instrument is used to measure a hand-made parallel plate capacitor. The capacitor can accept various types of dielectric material whose impact is studied.
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https://www.youtube.com/watch?v=xbVYgyoIrRk
In this episode Shahriar takes a close look at the Signal Hound Real-Time Spectrum Analyzer (BB60C) and Tracking Generator (USB-TG124A). In order to evaluate the performance of these units a few experiments have been setup. The performance of the Signal Hound unit is compared with the Tektronix RSA306.
A set of FHSS 900MHz long-range radios are used in the first experiment. The frequency hopping behavior, channelization, bandwidth and transmit powers are all captured using the BB60C. Furthermore, the recording capability and zero-span modes are used for frequency demodulation. The tracking generator (USB-124A) is then used to measure the performance of a band-pass microwave filter as well as a high-gain amplifier (40dB) gain. The free-space performance of the TekBox EMC Probe Set is also measured using the tracking generator.
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In this episode Shahriar attempts a difficult repair of a Tektronix RSA real-time spectrum analyzer. This well-equipped instrument reports several error messages during startup POST including LO Unlock as well as Signal Path failures. The service manual of the instrument does not provide any detailed block diagram and no schematics. Most failures require the instrument to be serviced by the Tektronix factory. The equipment has various advanced options including 110MHz analysis bandwidth, digital modulation analysis, wide-band IF output and deep memory.
The teardown of the instrument reveals a multi-board, multi-module design. The top of the instrument contains all digital blocks and boards while the bottom of the instrument houses the RF deck assembly. The RF deck is broken into various stages such as attenuator, RF switches, first converter, second converter, IF block, reference synthesizer and LO generator. For the purposes of addressing the YIG problems the LO board is examined. The problem is traced to two components, both dividers in the complex PLL system of the LO subsystem. The LO board is fully analyzed and described and the defective components re replaced.
The repaired instrument is tested for various functionality including DPX, de-modulation and measurement beyond 8GHz CW tones. The instrument passes all self-tests, alignments and detailed diagnostics.
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https://www.youtube.com/watch?v=30VxmTnhvfQ