Discrete GPRS

Jun 18, 2009 22 Replies
L

The "too hard" part of the exercise would probably be building the necessary discrete receiver - everything these days is a "somewhat" software-defined radio with no analog signal path - RF in, digital out, and generally little opportunity to open it into a wideband mode. A lecturer of mine last semester (?earlier?) was genuinely shocked when I talked about an ASK transmitter based on discrete transistors - "everything is in a chip now, and people just build the application note" :)

Ah, you're assuming that the PA [if any] input terminal is the only route for signal to get out of the box? I do wish I could design equipment to your assumptions :) Ferrite and mu-metal futures are looking good...

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C

There are plenty of sufficiently wideband digital down/up converter solutions out there.

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P

Assuming 0 dBm into the PA and something like +30 dBm out of it, the critical path is keeping the PA input clean.

Filtering at 1 mW or even 1 W does not cost so much, but doing any filtering at 10-100 W is costly, either because of the filter is bulky or the power lost is quite expensive above 1000 MHz.

The spurious radiation from power supply and control lines should not be an issue.

In the 1990's I have used cylindrical Murata ferrite cores with 6 holes on all control and power supply lines and with modern low inductance chip capacitors, filtering would be much easier.

With modern materials, this could be done much more cost effectively.

Paul

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