Interesting Questions, Facts, and Information
Electronics and Circuits
|The FFT, a mathematical process, is used extensively in digital signal processing (DSP). For what word does the second "F" in FFT stand?||Electronics and the Letter "F"
Fourier. FFT stands for Fast Fourier Transform, so the second 'F' stands for "Fourier".
Joseph Fourier's (1768-1830) theorem states that any periodic signal with a frequency "f" can be expressed as a (weighted) sum of the sinusoids of frequency "f" and f's harmonics.
Yes, even a square wave can be described accurately by a sum of sine waves - if you have enough of them. Square waves can be constructed by summing a sinusoid at the fundamental frequency, f, plus sinusoids at all of f's odd harmonics - 3f, 5f, etc.
0xFFFF. Hexadecimal numbers use the characters 0-9 and A-F, where A = ten, B = eleven and so on. Each column is a power of 16 greater than the column to its right, with the rightmost column the one's column.
The 0x at the start of the number indicates the number is in hexadecimal. This may seem obvious when the number has letters in it (such 0xFFFF) but a number like 32 decimal is represented as 20 hexadecimal so 0x20 is proper.
|Selectivity in a radio is important for allowing stations to operate on adjacent channels/frequencies without interfering with one another. When determining how suitable a filter is for a design, one might look at its "Shape..."?||Electronics and the Letter "F"
Factor. Shape factor is a unitless number and the lower the number the better performance. A perfect, so-called "brick wall", filter would have a shape factor of one.
Why is selectivity important? How bad would it be if your favorite FM station was being obliterated by one on a neighboring channel? Poor selectivity in your radio might be the culprit. Selectivity is often determined by the characteristics of the radio's filters.
|When measuring the characteristics of a small-signal amplifier, say for a radio receiver, one might be concerned with its "Noise..."?||Electronics and the Letter "F"
Figure. "Noise figure" is one critical parameter for determining the "quality" of a low-noise, small-signal, amplifier, and perhaps more importantly, the sensitivity of the overall receiver system. It is especially important for VHF (very high frequency) - and higher frequency - designs where most of the undesired "noise" (noise that masks or overpowers the desired signals) is generated internal to the electronics itself. In HF (high frequency) applications, atmospheric noise plays a much larger role in determining overall useful sensitivity, so a circuit's "noise figure" is less important.
Force. The term EMF, or Electromotive Force, its use now in decline, is attributed to Italian physicist Alessandro Volta (1745-1827). Today we generally use the term "voltage" - can you guess why we call it that?
Farad. The unit is named after Michael Faraday (1791-1867), a British scientist famous for his work in electromagnetism. A farad is a rather large value for ordinary use and quite often capacitors are much smaller and measured in micro- (one millionth) or pico- (one millionth of one millionth) farads.