[time-nuts] 10 MHz Oscillator comparison part II

EWKehren at aol.com EWKehren at aol.com
Thu Jan 13 05:17:04 EST 2011


List
A while back I proposed the Austron 2110 circuit. No response. This is a  
straight forward circuit with the only critical component the 5.0005 MHz 
Xtal. I  am sure there is in this group enough expertise to find a source and if 
enough  sign up a one time buy could bring the total assembly cost below $ 
50 PC board  included. With its 100 Hz output it may also turn into a simple 
tool to  measure Allan Variance.
Bert Kehren
 
 
In a message dated 1/13/2011 3:54:38 A.M. Eastern Standard Time,  
luciano.paramithiotti at hp.com writes:

^Well,  some time back I proposed a DMTD style front-end which mixes two 
unequal  frequencies with a common oscillator into a common frequency. In a 
second  ^stage it is mixed down by a second LO in more traditional DMTD  style.

^LO1 = (f1 + f2)/2
^IF1 = abs(f1 - LO1) = abs(f2 - LO2) =  abs(f1 - f2)/2
^LO2 = IF1 - IF2

^The IF1 filtering needs to filter  out the difference frequency and 
supress the sum frequency. However, since  both sides of the chain will have same 
^frequencies after first mixer,  correlation between the sides will create 
smaller response differences unless  built very different. 
^The mixer oscillator contribution for LO1 and LO2  will correlate between 
the channels.

Magnus, can you write down a block  diagram?

Luciano
IZ5JHJ

Luciano P. S.  Paramithiotti



-----Original Message-----
From:  time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On 
Behalf Of  Magnus Danielson
Sent: giovedì 13 gennaio 2011 5.34
To:  time-nuts at febo.com
Subject: Re: [time-nuts] 10 MHz Oscillator comparison  part II

On 12/01/11 19:24, Bob Camp wrote:
> Hi
>
>  If you have a random frequency like 7.352 MHz that neither divides or 
>  multiplies to 10 MHz harmonic or sub harmonic, you can indeed mix the 
>  signal to 10 MHz.
>
> If you do so, you will need to filter the  outputs, since the mixing 
> spurs will mess up the input to the  multiplier.
>
> If the generator you use for the mixing has more  noise or jitter than 
> the sources, that noise is likely to  de-correlate unless the chains 
> are absolutely identical. Since they  multiply to two different 
> frequencies, they really can't be  identical. Net result is your 
> measurement is messed up by the noise  of the generator.

Well, some time back I proposed a DMTD style  front-end which mixes two 
unequal frequencies with a common oscillator into a  common frequency. In a 
second stage it is mixed down by a second LO in more  traditional DMTD style.

LO1 = (f1 + f2)/2
IF1 = abs(f1 - LO1) =  abs(f2 - LO2) = abs(f1 - f2)/2
LO2 = IF1 - IF2

The IF1 filtering  needs to filter out the difference frequency and supress 
the sum frequency.  However, since both sides of the chain will have same 
frequencies after first  mixer, correlation between the sides will create 
smaller response differences  unless built very different. 
The mixer oscillator contribution for LO1 and  LO2 will correlate between 
the  channels.

Cheers,
Magnus

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