Hi, I want to build a Tayloe detector for my next project but I have limited understanding of demodulation theory that maybe someone can help clarify for me. Mainly, I'm interested in an FM signal near 80MHz, my PLL chip only goes up to 150MHz, but it has multiple separately configurable outputs. My first question is... can I mix the incoming 80MHz with say 70MHz, then bandpass the 10MHz, and feed that into my IQ circuit running at 40MHz?? I don't imagine I'll loose any modulation data that way... yet as I haven't come across any circuit designed that way there must be a reason why it is not done?
Sorry if I'm glossing over details as I say I'm not strong in this area not sure what info is the right amount of info, so please if u need details just ask. e.g. I can provide part numbers for the PLL chip and mixer chip I'm wanting to use if needed. Thought I'm just enquiring about the validity of the concept rather than a particular implementation of it.

Cheers

 

(Some text removed for clarity)
My first question is... can I mix the incoming 80MHz with say 70MHz, then bandpass the 10MHz, and feed that into my IQ circuit running at 40MHz??

Yes you can, but Tayloe demodulators are not, as far as I know, useful as FM demodulation.

 

The Tayloe is a I/Q demodulator/modulator. It has some really neat characteristics.

The bad part is that it slices the signal frequency into 4 parts. So a local oscillator of four times the signal frequency is required.

So if you have a local vfo with a 160 MHz output, the maximum receiving signal frequency is 40 MHz.

So the TS needs a down converter (a first receiver converter).........80 down to 10-20 MHz or so.

Search google for down converter circuits.

The Tayloe is a I/Q converter............and with DSP.......I/Q signals can be mod/demod......anyway you want.

With these new DSP processors.........one might mod/demod an antenna coil across a couple of port input/output pins.

 

Hi,
If all you're after is an FM receiver for WBFM at 80 MHz, then have a look at TDA7000 (and its homologues eg TDA7021 etc). These ICs are very old but are still available, and will allow you to knock-up a WBFM receiver pretty quickly, with the barest minimum of test gear. They have also been pressed into service for NBFM (here's a webpage from the famous Harry Lythall, on this topic: http://sm0vpo.altervista.org/rx/tda7k-rx2.htm ), and here's an app note from Philips:
http://www.qsl.net/yo5ofh/data_sheets/tda7000_for_narrowband_fm_reception.pdf

 

That's exactly it, I'll down convert and I/Q that, thanks for feedback . I do like the TDA7000 solution, but as you said, I'm not just after the receiver, this is more about the trip than the destination.

 

There's no need to downconvert. You can use the TDA7000 on its own (tuned to 80 MHz). If its really "more about the trip than the destination", then you can go the scenic route and use your PLL as a local oscillator, with a NE602 mixer followed by a 10.7MHz ceramic filter (Wideband or Narrowband) and then an FM demodulator ic like the old but venerable CA3189 (still available on Ebay). You will need a 10.7 MHz quadrature coil for the CA3189. The quadrature coil would be hard to come by nowadays, but have a look here: http://www.ebay.co.uk/sch/i.html?_o...TRC0.H0.X10.7+MHz.TRS0&_nkw=10.7+MHz&_sacat=0 .

If you do want to downconvert and use the TDA7000 for demodulation (which will avoid the quadrature coil), then again use the NE602 as mixer, your PLL as local oscillator , pass the mixer output through the 10.7 MHz ceramic filter and the output of that to the TDA7000 (which must be tuned to 10.7 MHz).

The main problem you face is that FM receivers are now so cheaply mass produced in the Far East, that essential parts for hobbiest constructors to build receivers, like Toko Quadrature coils and demodulator chips like the CA3189 etc are obsolete/unavailable.

 

Not sure of what the final goal is............but one of the neat characteristics of the Tayloe.........is the wide bandwidth.

With an op amp buffer........one can feed the output of a Tayloe into a sound card. And with SDR software......can see many signals both up and down from carrier. The sound card sets the bandwidth....if it as an open front end.

So the TS will need to keep this in mind........whatever he uses.

You can see commercial fm signals on a 20 dollar sdr dongle. But those are probably high speed adcs, not Tayloes.