On 8/14/2013 7:59 PM, josephrot wrote:
Oh, sorry... I had given for granted that those acronyms were more or less known as they
are used very often in the SDR field, but maybe I was wrong.
So, here it comes an attempt to a short explanation. A longer and more complete one can
of course be found using Wikipedia,
SDRï¿½ - Need this to be explained ?ï¿½ Software Defined Radio, a technology where the working
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ of the radio is mostly defined by a software program, and in a lesser extent by hardware.
ADCï¿½ - Analog to Digital Converter. Usually a single chip that converts a signal from an analog
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ form to a numeric one, in equally time-spaced samples, and quantized in amplitude
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ with a number of bits depending on the specific chip (usually from 8 to 24).
FPGA - Field Programmable Array. A chip containing hundreds of thousands of uncommitted
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ logic circuits, that can be dynamically reconfigured to perform the specific function(s)
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ needed for the specific application,
DDCï¿½ - Digital Down Converter. Usually one of the functions programmed into an FPGA. A DDC
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ implements the functions of downconversion and downsampling as described in my previous
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ ï¿½ message.
NCO -ï¿½ Numerically Controlled Oscillator. An algorithm that behaves as a hardware oscillator,
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ but whose output is a series of numbers that are the samples of the signal that
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ is generated (usually a sine wave).
CICï¿½ - Cascaded Integrator Comb. Also implemented inside the FPGA. An interesting algorithm
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ described about 25 years ago by Hogenauer, that implements the low pass filtering
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ needed before the downsampling stage. Loved by FPGA programmers, as it can be
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ implemented without using multiplicators, a scarce resource in an FPGA.
FIRï¿½ - Finite Impulse Response filter.ï¿½ A kind of filter that can be used to implement low pass, high
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ pass, band pass, all pass functions. A somewhat related kind of filters are the IIR, Infinite
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Response Filter. It would take too much space to describe here the differences, the pros and cons.
FFT - Fast Fourier Transform. The king (or the queen ?) of the algorithms used in the SDR field.
ï¿½ ï¿½ ï¿½ ï¿½ï¿½ Described for the first time in the early sixties of last century by Cooley and Tukey, two
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ respected mathematicians of the time. The FFT transforms the time representation of
ï¿½ ï¿½ ï¿½ ï¿½ï¿½ a signal into its frequency representation (and viceversa). Quite useful to perform
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ filtering, to compute spectrum, waterfall and a lot of other functions.
DUC - Digital Up Converter. Basically the opposite a a DDC. An algorithm that upsamples and
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ upconverts a baseband signal to the final output frequency. Normally followed by a DAC.
DAC - Digital to Analog Converter. The opposite of an ADC. A piece of hardware that takes as its
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ input a series of numbers that represent the signal to be generated, and that outputs
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ the analog signal described by those numbers. Needs to be followed by an anti-alias filter.
Hope to not have forgotten some acronyms...
73 Alberto I2PHD