Re: programming an rf synthesizer?

Duncan,

Thank you for your rapid response.

ADMtek makes the ADM8211. It is a Tulip-like MAC with an integrated BBP,
the RFMD RF3000.

The radio is probably based on an RFMD reference design, so maybe I can
find out likely values from RFMD.

Suppose that either I cannot find the reference design or I want to
verify it with the radio: Do you think I can find out the capacitor and
resistor values by following the traces and measuring with a multimeter?

I would not have guessed that I could not tune the channel center! Thanks
for bringing the superheterodyne-ness to my attention.

This project is looking like more fun all the time. =)

Dave

On Mon, Feb 03, 2003 at 11:11:58PM -0000, Duncan Barclay wrote:
> 
> On 03-Feb-2003 David Young wrote:
> > Seems like there are a few of you on the list who are programming wireless
> > drivers, so I ask: has anybody had to program an RF synthesizer yet,
> > especially the Si4126?
> 
> Programming a synth isn't that hard. As you say below you need to bit
> bang a serial interface. Getting the numbers to programme it is harder!
> I assume that you have no other documentation on this radio?
>  
> > Seems the ADM8211 does not provide a register for selecting the channel,
> > but it does have registers for you to use to bang bits at the RF
> > synthesizer over a serial bus.  Makes sense.  These ADM8211-based radios
> > contain the Si4126 RF synthesizer. Also, I see a 44MHz crystal. Am I
> > way off-base, or does the Si4126 divide the 44MHz crystal to produce
> > carriers in the 2.4GHz band?
> 
> This is really nasty of them. I can't find the data sheet for a Si4126, but
> there is an Si4136 (www.silabs.com). The really nasty thing is that this
> contains three oscillators - only one of which will be used to change
> channel. As there are two candidates on the Si4136 I cannot really guestimate
> which one is to be used. Do you have docs on the ADM8211 (who makes it?)?
> I would be able to figure it out from that.
> 
> Just download the Si4136 data sheet and it covers the Si4126 too. Ahh, Si4126
> only has one RF synth on it. Okay. We need to programme RF2. Looking at the
> datasheet there is a lot that needs setting up that cannot be guessed at.
> do you have an initial programming set for any of the registers? To change
> channel we only need to programme register 4, but to set the IC up we
> need to programme registers 1, 2, 5, 7, 8. I can guess at some bits, but
> I need a schematic (circuit diagram with component values)
> of the radio itself to guess at some other values. This might not be too
> easy to get...
> 
> As to how the PLL works - it will take the 44MHz, and divide it to 500kHz
> (probably) using the R dividers. This 500kHz signal is used as the input
> to a block of circuits that contain a 2.3GHz oscillator and some feedback
> circuits. The circuits can be thought of as an amplifier that amplifes
> frequency (it is actually a phase locked loop), and it's "gain" is
> set by programming the N divider registers - to get an output of 2.342GHz
> N would be set to 4684. You may ask why it isn't 2.4GHz, but something a
> bit lower - it's all to do with how you design a superhetrodyne radio
> (try google).
> 
> Duncan
> 
> -- 
> ________________________________________________________________________
> Duncan Barclay  | 
> [email protected]   | 
> [email protected]| 

-- 
David Young             OJC Technologies
[email protected]      Engineering from the Right Brain
                        Urbana, IL * (217) 278-3933
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