RF Concepts

These blog entries discuss RF/wireless concepts.

dBm to Milliwatts Conversion Tutorial with Python

Submitted by rfrobenius on

I was recently updating one of the online workbooks for the RF Technology Certification program and decided to try and re-write one of the calculators using Python. The topic is teaching how to convert from dBm values to milliwatts without using a calculator, so the calculator does not just calculate the conversion, rather it tries to demonstrate the process of approximation in your head. In the end, I decided to keep the original Javascript calculator with some updates rather than replacing it with the Python version.

Transmission Line Elements on Smith Chart Web App

Submitted by rfrobenius on

I've successfully added transmission line elements to the Smith Chart matching web app here on RFMentor.com. These include series, shorted shunt section, and open shunt section. There's a trick you can use to have these transmission line elements use an arbitrary characteristic impedance. The elements adopt the same characteristic impedance as the chart normalization impedance (default is 50 Ohms).

Analytical Impedance Match with Python

Submitted by rfrobenius on

I created a quick Python function to calculate the component values for an impedance match between two real (resistive) terminations using the technique taught in the Introduction to Impedance Matching course. Here is what the code ends up looking like, and it shows how useful Python can be for working as a "quick programmable calculator." In the old days, I might have been tempted to program my old HP48 calculator to crank out the same values. It only took a few minutes to put the code together, which is the beauty of working with Python.

Smith Chart Matching HTML 5 Version

Submitted by rfrobenius on

An early version of the Smith Chart web app is now available to try out. There are a couple of issues that I will be working on initially, such as the frequency entry dialog box appears to be transparent for some reason. I'll also be working on the layout to try and make the various parts of the app fit better on the page. At the moment, the app is only optimized for mouse input and does not respond to touch-based dragging events (to move elements around on the chart).

Self-study Guide: RF Small-Signal Amplifiers (LNA)

Submitted by rfrobenius on

Back in the mid-1990's, Les Besser and I wrote a series of articles on RF amplifier design for Applied Microwaves and Wireless magazine (unfortunately this magazine is no longer in circulation). Since that time, Les Besser and Rowan Gilmore have written a two-volume textbook on RF circuit design that covers this topic as well as a great deal of background knowledge on working with RF circuits.

Evolving Satellite Market

Submitted by rfrobenius on

The successful landings of Space-X's first stage rockets (and Blue Origin's success as well) signals a major breakthrough in the future reduction of the cost of space access. It seems to reason that this will result in a dramatic increase in the entrepreneurial interest in using satellite-based infrastructure to provide new services to a global audience. For example, companies like Google could deploy wireless internet access using small "cube" satellites that cost much less to build and launch than current systems.

LC Resonance Plotter

Submitted by rfrobenius on

Another application of using Python to demonstrate RF concepts comes in the form of a calculator to plot L-C series reactance. This plot shows two useful concepts: resonance and the effect of parasitic capacitance or inductance. For a capacitor, the magnitude of the series reactance decreases with increasing frequency, while the opposite is true for an inductor. For a capacitor with parasitic inductance, there will come a point where the two reactances are equal in magnitude and cancel each other out. This point is the resonant frequency of the combined circuit.

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