[eagle] Re: Eagle Microwave Antenna Arrays-- mechanical concepts

[John B. Stephensen]

The big current spike is during start up and the static current afterwards 
is low enough so that you can manage power dissiation. I wouldn't use DCMs 
for the reciver as it must deal with multiple narrow-bandwidth signals. The 
downlink will be about 2 Mbaud BPSK so phase noise isn't a big issue in 
generating low-frequency signals to be upconverted.

73

John
KD6OZH

----- Original Message ----- 
From: "Matt Ettus" <matt at ettus.com>
To: "AMSAT Eagle" <Eagle at amsat.org>
Sent: Sunday, March 25, 2007 21:40 UTC
Subject: [eagle] Re: Eagle Microwave Antenna Arrays-- mechanical concepts


> John B. Stephensen wrote:
>>  The amount of power required by the FPGA depends on the number of
>>  logic elements used and the speed of operation. Anything that isn't
>>  clocked in the FPGA consumes almost no power so the thermal
>>  dissipation is controlled by the logic designer.
>
> This is not true anymore.  Small geometry devices (< 90nm) can consume a
> lot of static power.
>
>>  DCMs require a lot
>>  less power than an external DDS and an FPGA would be a good place to
>>  put other logic.
>
> DCMs have horrible phase noise.  You wouldn't want to use them for
> generating clocks for ADCs, DACs, LOs, or PLLs.
>
>
> Matt
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