About RF (Radio Frequency)
Is RF (radio frequency) black magic or art?
Some people think so, but others do not agree at all, depending on how you approach RF, how much time you have spent on it, and how much you have accomplished.
I don’t think RF is Black Magic, after working over 40 years in this field.
However, there is not a shortcut to learn and get familiar with RF in a very short time.
Unlike digital circuit that has only high or low (true or false) outputs, RF circuit is linear and does not have absolutely right or wrong answers.
The amount of answers for each RF circuit can be as high as infinite.
Then what is the best result you can get with an RF circuit?
That all depends on your experience, how you approach the testing process, how much time you are willing to spend on this particular circuit, and how tight the specifications are defined.
The people who could not get the result as what they had expected to see would say RF is “art” or “Black Magic”.
Because they can’t correctly predict what result they will get, and things are always out of their control.
Sometimes the best data were those you’ve collected in the very beginning and you wished you had not wasted those extra hours for nothing.
But fortunately those hours were not wasted, because…
How do you know which data are the best if you don’t have a lot of them to compare with?
You collect more data from those extra so called “wasted hours” and then you have enough information to determine which are the best.
It’s those extra hours you’ve spent that get you out of the Black Magic maze and would save you tremendous time managing RF projects down the road.
As long as you spend enough time in the lab and put your hands on those PC board, you will soon know how to face a new project without fear and hesitation.
Simulation tools: you may think why can’t you just buy a simulation tool, let the tool do everything for you, and get things done in a very short time?
I am not a fan of using simulation tools. But I don’t ignore their power or object using them, as long as you don’t over-rely on them.
After all, who don’t like to sit in front of the computer, click the mouse and get things done quickly and easily?
Who like to sit in front of the work bench, hold a pair of soldering irons and stare at those test equipments for long hours to fight for the best data?
Yes, a good simulation tools can handily help you design your RF circuits and shorten your designing time. But it can also get you addicted into a situation that you will not be able to get out easily.
You will over-rely on those tools and will be paralyzed when you encounter a problem that is out of your expectation.
Because you will not have idea how to correct the discrepancy between the expected value calculated by the tool and the collected data from the circuit you’ve tested.
And, worse yet, based on my experience, this discrepancy always happens.
The higher the frequency is, the greater the discrepancy can be. Once the frequency is over 2 GHz, then things will get harder to control.
And you need to fight hard to take care of those uncertain parameters that affect the circuitry output.
Some good and expensive simulation tools take these uncertain parameters into consideration and will get you very closed to the final real output data.
And they will save you tremendous time.
However, those good tools are very expensive, $100k or higher, and are something only very few people can afford.
Cheap tools can only provide very limited information and help, and always leave you more confusion than help.
Hands-on bench experience: The practical way to become a good RF engineer, technician, or amateur hobbyist, is to spend as much time as you can in the lab to get loads of hands-on experience.
You will know how to resolve those unavoidable problems quickly and instinctively.
As time goes by, you’ll accumulate a high level of experience and build up strong confidence, and will be able to approach and finish any projects quickly without hesitation.
R, C, L: You need to thoroughly know these 3 basic passive components, R (resistor), C (capacitor), L (inductor), and can properly use them in your RF circuits.
Because these humble little components are the most important parts in an RF circuit.
Otherwise, you will have a very hard time to deal with RF circuits, especially at a frequency of 1 GHz or higher.
A lot of RF people think they are simple components and do not bother to learn and know them well.
What type and value of capacitors should you use in that particular circuit and frequency? Ceramic, tantalum, or high Q chip? 10 uF, 1 uF, 1000 pF, 1 pF, or even less?
What location should you insert them as well as how many of them should you use?
How about inductors and resistors?
There are not firm answers for these questions, but you will know how to use them properly if you become a highly hands-on RF guy.
And all of this information will become your instinct as your breath.
Because of this, you should be very good at using solder iron so you can do basic soldering job yourself.
Soldering skill: You won’t become a good RF people if you are not a handy solder iron user and always need to rely on other people to do soldering job for you.
A lot of RF engineers think they don’t need to be good at this very useful skill at all and they need to rely on other people to solder even a 2- lead passive component.
You would be able to replace this simple component within 1 or 2 minutes if you are good at the basic soldering skill.
But you need to wait 10 minutes, 1 hour, or even over a day for your assistant to replace that simple component if you can’t do that yourself.
And you can only collect very few sets of data within a fixed timeframe.
Then how soon can you complete the whole testing cycle and get the final result even if you won’t run out of your patience waiting for help?
I would say you can finish the project 50% to 80% sooner if you are able to do the simple soldering yourself, instead of waiting for the help from other people.
Of course, you may need to ask for a professional help if the soldering job involves sophisticate skills and tools.
Summary: You should get involved with hands-on bench test as much as you can if you really want to get the RF technology under your control.
Then you will know how to complete a project from scratch to meet the specifications of performance, size, cost, power consumption, and the product will be usable and salable.
It’s time and practice that will take you to the point you would like to reach and you will be able to approach any new RF projects without hesitation.
Once you have 10 or more years of robust hands-on RF experience, then you won’t think RF is Black Magic anymore.
What you will learn here:
- Basic and practical RF theories.
- Basic and practical RF laboratory testing skills based on over 40 years of hard-earned hands-on bench work experience so you will avoid those mistakes a lot of RF people have made.
You will go straight to the right direction with your circuit test and will acquire correct data in a short time.
- How to approach and test a board level project.
- How to verify your final product is optimally designed.
- What to know and how to test these components/circuits:
LNA (receiver low noise amplifier), PA (power amplifier), mixer, modulator/demodulator, IF amplifier, RF filter, active/passive filter, A/D & D/A converter, AC to DC and DC to AC converter, detector, transformer, combiner/splitter, power divider, isolator/coupler/circulator, diplexer/duplexer, power supply, oscillator, VCO, phase-locked loop, connector, attenuator, RF switch/relay, balun, R/L/C, diode, sensor, op amp (operational amplifier), multiplexer, and a lot more.
- Technical things you need to know:
dB/dBm/dBc, input/output impedance matching, harmonics, Rx/Tx spurious response, shielding, noise figure, receiver sensitivity, gain and frequency response, smith chart, insertion loss, printed circuit board (PCB) layout, transmission line/stripline, surface mounted device (SMD), transceiver, soldering skill, and a lot more.
- How to properly use basic RF test equipment:
spectrum analyzer, network analyzer, RF signal generator, RF power meter, oscilloscope, multimeter, and a lot more.
- Provide advanced learning resources:
Simulation tools, PCB layout tools, advanced circuit design references, component/equipment procurement, and a lot more.
What you will not learn here, but we will provide adequate resources if applicable:
- Advanced RF theories.
- Sophisticate RF circuit/product design.
- Bluetooth, wireless LAN, Ultra-wideband radio design and application.
- Cellular/wireless phone design, antenna design, advanced digital circuit design.
- Amateur, marine, ham, walkie talkie, and radio operation etc..
- FCC policies.
About Charlie Hu
Educational Background :
- Bachelor degree: Electrical Engineering, National Taiwan University, Taiwan, 1972.
- Master degree: Electrical Engineering, Northwestern University, Evanston, Illinois, 1975.
- PhD candidate: UCLA, Los Angeles, California, 1976.
Starting in 1976 as a Junior RF Engineer, I worked in the RF field for over 40 years and retired in 2017.
In these many years, I’ve held positions of Junior RF Engineer, RF Engineer, Senior RF Engineer, Staff RF Engineer, Principal RF Engineer, Chief Engineer, RF Manager, VP Engineering, and Senior VP Engineering.
In addition to working for a few companies, I also started up 2 small businesses in 1990’s.
Job Scope: product description & design, block diagrams & detailed schematics creation, PCB layout & fabrication, components procurement, parts inventory control, prototype PCB loading, prototype board test and verification, production flow supervision, FCC compliance management, product field trial, marketing event attendance, customer support.
I have basically by myself completed over 300 projects including small prototypes and finished sellable products, pricing range from less than $100 to well over $10,000.
I also worked with a few teams to complete several complicate products, with sale price between a few thousand dollars and well over $1M.
And they are all RF products.
Products I’ve Accomplished: Semi-military frequency synthesized man-pack radio (1 MHz to 30 MHz), Broadcast Radios (10 MHz to 1 GHz), Industrial Data Transmission Radios (200 MHz to 1GHz), Fiber Optical Cable Modem (10 MHz to 1 GHz), Wireless Keyboard and Mouse (400 MHz to 2 GHz), Defense Equipments (up to 10 GHz), Broadband Wireless (up to 6 GHz), Point to Point Data Transmission Radios (2 GHz to 42 GHz), Point to Multipoint Data Transmission Radios (2 GHz to 6 GHz)
Basically, I have worked on any frequencies from DC to over 40 GHz, and I have almost touched any RF components and circuits.
I worked long hours every day and I spent over 80% of the working hours in the lab and I think this is the only way you can get your RF projects done quickly and effectively.
I can start any kind of RF project, small or large, right on the track within few hours based on the HAND-ON experience I’ve acquired in that many long years.
Why Am I Creating This RF Blog: Have been working with a handful of RF engineers and technicians, I know the hardest part to become a good RF people is to enjoy working in the lab.
Very few RF guys are really willing to spend a lot of time to put their hands on the bench and acquire practical experience.
Most of them would like to sit in front of their computers and hope the simulation tools will help them resolve their problems.
Unfortunately, all software tools are created by people and they can only be as good as their creators.
I would like to record whatever I’ve learned in the last 40 years, step-by-step, in this blog and hopefully you are able to learn something from it.
If you follow this blog you’ll have the knowledge that I’ve spent over 40 years to accumulate, so you’ll soon be able to complete any RF projects in a very short time.