[time-nuts] DMTD using Active Mixers

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Nov 11 22:07:18 UTC 2009


Magnus Danielson wrote:
> Bruce Griffiths wrote:
>> Active mixers almost invariably have a higher noise floor than 
>> passive mixers, particularly in the flicker noise region.
>> Consequently a DMTD system using active mixers will have a higher 
>> system noise floor than one using active mixers.
>
> ... than one using passive mixers.
>
> You still need driving amplifiers.
>
> Cheers,
> Magnus
>
Its much easier to ensure that the flicker phase noise of a buffer 
amplifier is low than it is to achieve a low flicker phase noise for an 
mixer using nonlinear active devices.
Even passive FET mixers have higher flicker noise than passive mixers 
using schottky diodes.

Bruce




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