Quote:
Originally Posted by brightsparkey
...the coupled resonators have low coupling coefficient - i guess I wasn't expecting as little as 10%...
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Quote:
Originally Posted by ms660
The 10% mentioned suggests over coupled or low Q if critical.
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Two opposing opinions!
Lawrence is nearer, obviously he has a feel for the figures - coupling between the circuits is actually really low for critical response. I gave 10% only as an order-of-magnitude, and yes, typical 470kHz IFT's are often much less (though 10.7MHz ones, where Q's are lower, may approach 10%. But I've not yet designed one).
With a high Q to the circuits, at resonance the second circuit puts quite a heavy load on the first, so killing its own peak rather effectively. You can think that if the first circuit has really high Q, it only takes a smidgen of resistance to clobber the peak. So equivalently, only a tiny bit of energy sucked out by the second, makes a massive difference.