[linux-dvb] Re: [RFC] USB DVB design

[Holger Waechtler <holger@convergence.de>]

Sven Karlsson wrote:
> Hi Holger,
> 
> 
>>the low costs for the PCBs (about 10-20EUR at quantities of 10-20pcs.)
>>won't justify the higher effort of a 'universal' PCB design.
> 
> 
> I would like to disagree. I have some experience in running electronics
> projects (have run more than 20 major projects both as a hobby and
> professionally).
> 
> I have learnt the hard way that generalism is a good thing indeed and it
> really pays of in these kinds of small projects.
> 
> In my experience, the major problem here is to make things actually work
> properly since we are dealing with (microwave) radio electronics. Tuners
> tend to be very picky with noise in the ground and power supplies. In most
> cases, if not all, you will have to use proper ground and power planes
> (possibly multiple ground/power planes) and very good voltage regulation.
> This applies even to monolithitic tuners/front-ends, at least the ones I've
> seen.
>
> From your schematics it looks like you are going to use switchregulators to
> generate all voltages. I would suggest to make sure that the front-end
> _really_ can handle the noise on the power input. You might need to use
> linear regulators on some of the more sensitive power rails.

yes, they are sensitive. On the other hand switching up- and 
downconverting DC/DC converters are common in this area, so we should be 
able to solve these problems.

In the MAX??? datasheets you'll find the noise curves - IIRC they are 
about an order of magnitude smaller than the noise level acceptable at 
the tuner supply inputs.


> And by the way, what front-ends are you going to use?

The Microtune 7072DTF, just for the reason that we can get them easier 
than other ones.

Holger



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