Dear Alberto,
On Wed, 23 Feb 2005, Alberto di Bene wrote:
>
Do really exist A/D converters capable of 24-bit resolution at 30 MHz
bandwidth ?
Why one need 24-bit? Though 16 bit is adequate for most SW,MW,LW recievers.
16 bit yelds abt 90 dB dynamic range (every bit exept sign bit yelds 6dB).
But this is dynamic range if there is no filtering. When you make banwidth
narrow by DSP then dynamic range will be improved because noise decreases.
If frontend sampling rate is, say 100 MHz (there is such an ADC) and
bandwidth of DSP filter is about, say 10 kHz this yelds 40 dB of noise
decreasing. Thus RX dynamic range to be about 90+40=130 dB! Realy DD is
not 130 dB of cose. But it much less due to analog (!) effects in ADC
absolutely similary as in conventional analog RX. This is not digital
effect!
Because 3G celular systems require such chips (ADC, DDC having sampling
rate abt 100 - 200 MHz) this chips are avaliabale now. Seems
radioingeneer speciality now change to programer speciality. To build
say RX now you need very few standard chips (ADC,DDC and CPU) connected
in standard way and lot of programing! Nothing more, forgot about
soldering iron, learn C++. Present days are days of digital radio. Analog
radio died.
73 de RA9MB/Alex
http://www.qsl.net/ra9mb
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