cell phone radio

My guess that there's no classic radio.

I haven't heard of this before. Do you subscribe to something from your cell phone provider to receive FM?

If so I'd guess the provider simply sends the selected signal via the normal cell phone digital stream.

...Jim Thompson

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| James E.Thompson, P.E.                           |    mens     |
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Hi, It's a Nokia 3500, the most basic phone you can get these days. Its only flaw is its tiny lo-res screen. But it plays MP3s, MP4s, has the usual suite of calendar/calculator tools, it can be used as a USB drive without Nokia software, it has Bluetooth, etc and a regular FM radio.

The phone works without a SIM card. The FM radio works like a regular radio, it scans the air and memorizes stations. I was just trying to get info on the radio. 88-108MHz is a low frequency these days for a ADC.

I was curious. I know nothing of how these SDRs work, there has to be some kind of analog front end, I was wondering what it looked like. I mean I don't need to know if my phone is like that to find out, but it's more fun if you have an actual implementation in front of you.

It very possibly is, although AM or FM demodulation is simple enough that it might be a bit of a stretch to call it a "software defined radio." Your phone probably uses a chip just as these:

, and while they do label a block "DSP - Filter, Demod, multiplex," I suspect that "DSP" is a handful of multipliers are set up in a fixed arrangement with relatively few parameters that can be changed -- not at all like a general-purpose SDR where the demodulation algorithm is very much expected to change over time. I.e., it's kinda like a ROM-based SDR. :-)

Note that single-chip FM radios ICs that use traditional analog techniques have been around forever -- long before SDR was a viable option: Something like the TDA7000 here --

|pp=[t=pip,i=TDA7000_CNV_2] -- has been around for around a couple of decades, and undoubtedly they've sold many, many millions of them.

---Joel

I used to have a Nokia '8320 with FM radio built in, and it would produce a horrible high-pitched hum (200 Hz-ish perhaps) whenever the strength of the FM signal fell below 'quieting' - probably through self-interference from the 'phone's digital circuitry. The FM radio part may be similar to what is contained in the cheapest FM radios (e.g.

nowadays, and this may be a conventional superhet (like However, there are other ways when the same PCB contains a GSM receiver - just a shame they didn't get a really-useful degree of sensitivity in the 'phone I had.

Chris

these:

|pp=[t=pip,i=TDA7000_CNV_2] --

Ah, I see. This monkey has a built-in LNA. But I need to register to see the datasheet. I'm gonna go have lunch instead I think. It's merguez sausage day today.

Highly doubtful. That would be a huge waste of cellular system capacity.

-mpm

Not yet. Just some shared circuits.

Actually there are some new digital streams distributed with the newish HD radio. The money flows get weird though.