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Glossary

Page history last edited by David-Taylor 10 years, 8 months ago Saved with comment

Glossary

 

ADC
 Analogue to Digital Converter. Usually a single chip that converts a signal from an analogue form to a numeric one, in equally time-spaced samples, and quantized in amplitude with a number of bits depending on the specific chip (usually from 8 to 24).
CIC Cascaded Integrator Comb. Also implemented inside the FPGA. An interesting algorithm described about 25 years ago by Hogenauer, that implements the low pass filtering needed before the downsampling stage. Loved by FPGA programmers, as it can be implemented without using multipliers, a scarce resource in an FPGA.
DAC Digital to Analogue Converter.  The opposite of an ADC.  A piece of hardware that takes as its input a series of numbers that represent the signal to be generated, and that outputs the analogue signal described by those numbers.  Needs to be followed by an anti-alias filter.
DDC
Digital Down Converter.  Usually one of the functions programmed into an FPGA.  A DDC implements the functions of downconversion and downsampling as described in my previous message.
DUC Digital Up Converter.  Basically the opposite a a DDC.  An algorithm that up-samples and up-converts a baseband signal to the final output frequency.  Normally followed by a DAC.
FFT
Fast Fourier Transform.  The king (or the queen ?) of the algorithms used in the SDR field.  Described for the first time in the early sixties of last century by Cooley and Tukey, two respected mathematicians of the time.  The FFT transforms the time representation of a signal into its frequency representation (and vice-versa).  Quite useful to perform filtering, to compute spectrum, waterfall and a lot of other functions.
FIR
Finite Impulse Response filter.  A kind of filter that can be used to implement low pass, high pass, band pass & all pass functions.  A somewhat related kind of filters are the IIR, Infinite Response Filter.  It would take too much space to describe here the differences, the pros and cons.
FPGA
Field Programmable Gate Array.  A chip containing hundreds of thousands of uncommitted logic circuits, that can be dynamically reconfigured to perform the specific function(s) needed for the specific application.
NCO
Numerically Controlled Oscillator.  An algorithm that behaves as a hardware oscillator, but whose output is a series of numbers that are the samples of the signal that is generated (usually a sine wave).
SDR
Software Defined Radio, a technology where the working of the radio is mostly defined by a software program, and to a lesser extent by hardware.

 

Some recommended reading

 

Alberto I2PHD, says: I could suggest the following books, the first of which is also available as a chapter-by-chapter free download in PDF format.

 

 

  • Digital Signal Processing in Communications Systems - http://tinyurl.com/mqy8537
    Also a classic. A bit dated, but the algorithms aren't. The only pity are the many typographic errors, especially in mathematical formulas.

 

Also:

 

 

 

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