[hpsdr] [CASMIR] Design v0.3

[Eric Ellison]

Lyle!

After reading 1 - 15.. I really like #0! Paint the target around wherever
the arrow hit's something.

Could that be a design goal?

(smile, long hot evening in my garden.. 'tick' 'tick')
Talley Ho!
Good Ideas!

Eric


-----Original Message-----
From: hpsdr-bounces at hpsdr.org [mailto:hpsdr-bounces at hpsdr.org] On Behalf Of
Lyle Johnson
Sent: Tuesday, June 06, 2006 9:13 PM
To: Alex
Cc: Christopher T. Day; hpsdr at hpsdr.org
Subject: Re: [hpsdr] [CASMIR] Design v0.3

***** High Performance Software Defined Radio Discussion List *****

> This leads to my query to everyone on LO and I/Q generation. I need some
solid arguments not some "I used DDSes in the past and they suck.", but some
good technical discussions. So ... here are three directions the design can
go:
> 
> (1) Use the AD9958 and generate the LO and the DDS reference clock from
the FPGA
> (2) Use a AD9959 and don't let the FPGA generate the LO, just the
reference clock for the DDS
> (3) eliminate the DDS and let the FPGA do all the work 

When I was a kid, I remember seeing a comic strip (isn't that where many 
of us got our early education?) that showed a person shooting arrows 
into a fence.

After he shot the arrows, he walked to the fence and began painting 
targets around them so all of his arrows hit bull's eyes.

So, my short list of initial questions (to establish the targets first!) 
are:

1) what is the desired frequency coverage?

2) what is the desired frequency stability?

3) what is the desired phase stability?

4) what is the desired amplitude stability?

5) what is the desired power output range?

6) what is the expected load impedance?

7) what sort of mismatch to that impedance needs to be tolerated?

8) what sort of signal to noise ratio is wanted?

9) what amplitude level of spurs are acceptable?

10) what lock-up time is necessary?

11) will the transmitter be required to be tunable (e.g., adjust the 
center frequency of the output) while transmitting?

12) what information bandwidth is desired to be impressed (modulated) 
onto the transmitter "carrier"?

13) how fast must the transmitter respond to a "transmit on" command and 
a "transmit off" command (e.g., envelope rise and fall times)?

14) what is the budget limit for bill of materials at quantity one?

15) are semiconductor devices limited to packages with leads, or are 
ball grid array and chip scale packages acceptable?

There may be other essential questions, too.

We can then figure out suitable approaches for frequency synthesis, be 
they DDS, PLL or a combination.  And power amplification.  And how to 
create modulation waveforms. And...

Or, it may be that you just want to see what you can do with a given set 
of parts.  A sort of SDR equivalent to the QRP "What sort of radio can 
you make using only 2N2222 transistors for the active devices?"

And, as in most engineering endeavors, there is no correct answer.

Enjoy!

73,

Lyle KK7P

_______________________________________________
HPSDR Discussion List
To post msg: hpsdr at hpsdr.org
Subscription help: http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org
HPSDR web page: http://hpsdr.org
Archives: http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/


 1149643286.0