Gregory explains how Phase Noise below the measurement setup noise-floor is measured, using two separated analyzers and cross-correlations in the frequency domain.
Some methods of Phase Noise measurement are limited by the analyzer own phase noise profile, as its own noise adds to the measured signal, corrupting its profile.
Using two separated analyzers, with uncorrelated noise profiles, it is possible to perform cross-correlation that uncouple the measured noise from the setup added phase noise.
Project update on the BPSK Radio Transceiver we are designing here in the channel.
In this video, we are going to take a look at some bad design decisions and ways to improve it.
This transceiver was design to operate at the 80m band, using a Class E 25W PA.
The frequency planning was not done correctly, and the implications are discussed.
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https://www.youtube.com/watch?v=IEZgAEy3pTo
Gregory explains the transformer model and how the magnetization inductance behaves in the circuit.
Circuits using transformer are sometimes hard to understand because of the complex behavior of the magnetization inductance and the leakage inductance.
A trick for measuring the magnetization current in LTSpice is given, demonstrating in depth how the waveforms relate to the transformer behavior in an oscillator circuit.
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https://www.youtube.com/watch?v=KtEfu3Oumo0
Gregory explains the principles of clock recovery and clock synchronization. A digital PLL is designed as a full clock recovery system that is demonstrated on the bench.
In digital communication, where data messages are transmitted encoded in bitstreams, the receiver end is always presented with the challenge of clock recovery.
Clock recovery is the art of reestablishing the time slices of the encoded bits, that were generated in the transmitter side. This timing information, for NRZ signals, is not transmitted, because it would occupy bandwidth without payload information.
Read the full article here:
https://gusbertianalog.com/clock-recovery-with-digital-pll/
00:24 - Introduction
01:18 - NRZ bitstream signal
02:25 - Why Clock Recovery and Synchronization
05:40 - Edge detection on the data bitstream
08:12 - Digital PLL
13:35 - Designed system
15:30 - Data frame sync
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References:
http://s53mv.s56g.net/dmostovi.pdf
https://en.wikipedia.org/wiki/Clock_recovery
https://download.tek.com/document/65W_26023_0_Letter.pdf
https://web.stanford.edu/class/archive/ee/ee371/ee371.1066/lectures/Old/Older/lect_17_CDR_2up.pdf
https://www.skylaneoptics.com/en/articles/clock-data-recovery-cdr/
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https://www.youtube.com/watch?v=HcYFFlsSLrg
Learn the basics about impedance match and how impedance matching networks works.
Impedance matching is an important topic in RF and Microwave electronics. In this video, Gregory shows how an LC impedance match network was design to match a 150ohm load to a 50ohm system.
The designed network is demonstrated using time domain signals and measurements of S11 with a directional coupler.
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https://www.youtube.com/watch?v=XCiBvhleDIM
In this video Gregory presents the concept behind the 1db Compression Point of an RF amplifier.
The measure is performed using a Signal Generator and a Spectrum Analyzer.
The relation with large-signal behavior is explained and the non-linear distortion the occurs after the 1db compression point is show in the time domain with an oscilloscope. On the scope, FFT is used to show the increase in harmonic power when the input/output power approach compression.
Part 1 of this video series:
https://www.youtube.com/watch?v=rJmt5si8Y0M
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https://www.youtube.com/watch?v=42NBCLixsY0
Gregory explains the basics of Impedance Matching using the Smith Chart and the usage of a Genetic Algorithm optimizer to fine tune the network, achieving the goals of Q factor, fundamental and harmonic termination.
Impedance Matching over a broader range of harmonics is key for RF PA design. Different classes of operation requires different reactive terminations.
The task of designing proper impedance matching networks, that also de-embed devices parasitics, quickly become unpractical using analytical tools or geometrical analysis over the Smith Chart.
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Learn the basics of impedance matching
https://youtu.be/XCiBvhleDIM
00:15 - Introduction
03:05 - Smith Chart Impedance Matching
04:45 - Q factor
06:18 - Genetic Algorithm
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https://www.youtube.com/watch?v=g4v612_5eRU
Gregory explains what is THD - Total Harmonic Distortion, using the circuit from the last video.
THD is a measurement of distortion, used as the main figure of merit in audio applications, where the non-linear behavior is characterized using the power at the harmonics of the fundamental signal.
Watch my video about Nonlinearity and Distortion
https://youtu.be/acWZLW5EE3U
Watch my explanation about the Wien Bridge Oscillator
https://youtu.be/e1JnmsuaMgs
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00:18 - Oscillator prototype
01:12 - Circuit behavior
02:12 - Total harmonic distortion
07:10 - THD measurement
07:56 - Measuring distortion with oscilloscope
11:18 - Final circuit details
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https://www.youtube.com/watch?v=LU8pOYLmtxo
In this video Gregory will demonstrate the distortion that occurs when a signal with a fast edge, like in a mixed digital-analog domain, is passed thru an amplifier working in class B mode.
The fast signal is generated by amplification a RF signal from a generator, using a CMOS inverter working as a linear amplifier.
The fast edge generated by the inverter gates are used as input of the push-pull stage developed in the last video https://www.youtube.com/watch?v=S7jrirsfkNw
The bias is adjusted to show that in class AB or class A the distortion is greatly reduced.
00:31 - Circuit diagram explanation
01:42 - Circuit overview
02:15 - Analyzis of the signal
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https://www.youtube.com/watch?v=WbAsnTYUWEI
Can a BJT transistor be used as an RF switch?
In this video we are going to take a look at the usage of a BJT transistor as a Diode RF Switch. The base-emitter and base-collector junctions are used in the place of diodes in a standard RF switch topology.
The isolation and insertion loss of the device is measured and characterized.
You can read the results here:
https://gusbertianalog.com/rf-switch-using-bjt-transistor/
Download the PIN Diode Handbook here:
https://www.ieee.li/pdf/essay/pin_diode_handbook.pdf
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https://www.youtube.com/watch?v=RlPoE2WjBus