On 1/5/2016 12:07 PM, Bruce Griffiths wrote:
The noise of such Gilbert cell based analog multipliers far exceeds that of the traditional mixer. Bruce
Read Gilbert's paper or Gray and Meyers analog IC textbook and you will see that the whole theory of operation of these depends on keeping the signal levels in them very small, especially if linearity (actually translinearity) is important. They always have current sources in the emitters that contribute a lot of noise. So you have small signals and large noise. The IC's that are designed to be DC coupled have even more sources of extra noise. IMHO, they only make sense in low performance applications where the lack of transformers is important or in DC coupled applications. The only time I have used an analog multiplier IC was in Costas loop to demodulate QPSK from weather satellite. It needed to be DC coupled. Rick Karlquist N6RK
On Wednesday, 6 January 2016 9:01 AM, Poul-Henning Kamp <p...@phk.freebsd.dk> wrote: My little HP5065 project is continually running into the jitter of my HP5370B counter which is annoying me, so I'm looking int DMTD. Everybody seems to be using traditional diode-mixers for DMTD, and to be honest I fail to see the attraction. Why wouldn't a analog multiplier like AD835 be better idea ? What am I overlooking ?
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