[hpsdr] new DDS

[Robert McGwier]

Yes, more careful reading reveals several issues.  20% of the oscillator 
is everything below 100 MHz!!

It is highly dependent on frequency and in fact, it is clear they intend 
this to be a fix for spurs when dialed up on a fixed or small collection 
of fixed frequencies and then "hand optimized".

This will be a real pain to use.

Bob



KD5NWA wrote:
> Some serious limitations on the technology;
>
> 1. The output frequency must not be any lower than 20% of the 
> reference oscillator.
> 2. The compensation required is dependent on the chip, it varies from 
> unit to unit so much that the values of one chip can not be used on 
> another chip.
>
> Sounds like it will be of limited use in a environment where the 
> frequency varies all over creation.
>
>
> At 02:03 PM 5/27/2006, Robert McGwier wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> Leon Heller wrote:
>> > ***** High Performance Software Defined Radio Discussion List *****
>> >
>> > http://www.analog.com/UploadedFiles/Data_Sheets/610141489AD9911_0.pdf
>> >
>> > Interesting feature is 'SpurKiller'technology.
>> >
>> > 73, Leon
>> >
>> This is bloody brilliant.  Many of us have proposed blind deconvolution
>> and of course, this is insanity compared to this.  The location of these
>> spurs has a mathematical, closed form description.  Given the phase in
>> the accumulator and the frequency,  you can mathematically compute the
>> frequency, phase, and amplitude of these spurs to high accuracy.  They
>> have chosen to take N of them (it looks like up to 3), invert them and
>> add them to the output effectively suppressing the 3 worst (if I read
>> this correctly).  To capture that in the hardware itself is a very nice
>> piece of work.   I have not taken the time to see if this part can be
>> sync'd or if they are introducing a I/Q version.
>>
>> Bob
>>


-- 
AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,
NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman
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