[hpsdr] HPSDR Block Diagram

[Phil Harman]

Hi Alex,

Thanks for the clarifications.

One additional suggestion.   If you use the FPGA ( or is this a CPLD?) to 
distribute the I/Q PWM signals, then remove the PI5V331 and replace the 6x 
AD8132's with AF LPFs. I don't see why you need such high speed AD8132s 
anyway.

I'll post my paper on ideas for the Horton LO at the weekend.

73's Phil....


----- Original Message ----- 
From: "Alex" <harvilchuck at yahoo.com>
To: <pvharman at arach.net.au>
Cc: "Philip Covington" <p.covington at gmail.com>; <hpsdr at hpsdr.org>
Sent: Friday, July 07, 2006 8:31 PM
Subject: Re: [hpsdr] HPSDR Block Diagram


> Phil,
>
> Thanks! My comments are in-line.
>
> ----- Original Message ----
> From: pvharman at arach.net.au
> To: Alex <harvilchuck at yahoo.com>
> Cc: Philip Covington <p.covington at gmail.com>; hpsdr at hpsdr.org
> Sent: Thursday, July 6, 2006 11:38:46 PM
> Subject: Re: [hpsdr] HPSDR Block Diagram
>
> Hi Alex,
>
> There are a number of things that I don't understand in relation to your
> CASMIR design.
>
> 1. The I/Q inputs to the mixers appear to come from the Atlas bus. Are you
> proposing the use the I and Q PWM signals and low pass filter them on your
> board. Is this what the AD8132s are for? In which case what are the 
> amplifiers
> between the FPGA and PI5V331 for?
>
>
> This portion of the circuit is directly lifted from JANUS. CASMIR is going 
> to handle the I/Q PWM exactly the same was JANUS is (plus I was going to 
> reuse your VHDL). The amplifiers just after the FPGA are the NE5532D's 
> from JANUS. I left them in for now.
>
>
> 2. The AD8345 seems to cover 140MHz at the low end - will it work at 
> 50MHz?
>
>
> Regretably not. 140MHz is at the bottom end of it's capabilities.
>
>
> 3. I assume the PI5V331 is being used at a QSE - at 10nS switching time 
> are
> they fast enough?
>
>
> The second PI5V331 is being used as the QSE. It only has to do up to 75MHz 
> to support the 4m band.
> It can either be the FST3253 or the PI5V331, both are used in numerous 
> designs from Gerald's QEX articles to WB6DHW's circuit (and many other 
> designs on the internet)
>
>
> 4. Will the outputs of the AD9512 drive the AD8349 without additional
> interface chips?
>
>
> I did not finish the LO distribution portion of the design since it's 
> still up in the air where the LO is coming from. The AD9512 has 5 outputs.
>
>
> 5. The current LO ideas are for either a DDS or dividing down a 2.4GHz
> oscillator. Since the LO inputs to the AD9512 are all ready in I/Q format 
> how
> does this divider scheme work?
>
>
> We need a decision on the LO generation. Some comments say it's going to 
> be centrally generated, some comments say each board needs to generate 
> their own LO.
> This is why I halted work on the LO distribution and just put the design 
> out for comments.
>
>
> 6. What output power levels are you expecting from the board?  Should a 
> MIMC
> be added to each output so that the filters are buffered from any load
> variations?
>
> Yes, a MIMC needs to be added for each of the outputs. Higher power levels 
> need to be generated in an external circuit. I'll add it to the CASMIR 
> issues list.
>
>
> 7. Why use bandpass filters for the HF outputs, won't the sprogs from the 
> QSE
> be harmonics so LPFs could be used?
>
>
> I'm going with the "standard design" here. All examples I have 
> investigated on the internet have been using BPFs (CDG2000, T03DSP, 
> SDR-1000, etc.). It might be worth doing a little experimentation.
>
>
> 8. Will the PI3B3251 switches handle the signal levels we expect?
>
>
> They should, but I've got a call in with Pericom to discuss
>
>
> 9. May need to allow different LO inputs for HF and above.
>
>
> I have an issue I created against the design that I need to add a LO port 
> for tower mounted microwave amplifiers and upconverters
>
>
> 10. Why not run 50MHz out of the QSE?
>
> 50MHz and 70MHz are coming out of the QSE already. I'm rerouting the 
> outputs to the VHF and up output connector
>
> More questions to follow. I think that a white paper explaining your 
> concepts
> would really help the review process.
>
>
> I updated the Wiki yesterday with a narrative of the design.
>
>
>
>
> 73's Phil...VK6APH
>
>
>
>
>
>
>
>
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> 



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