[time-nuts] WWVB BPSK Receiver Project? (fwd)

gary lists at lazygranch.com
Sat Mar 17 13:48:08 UTC 2012


Yes, in order to equalize group delay, you need to know what to 
equalize. But with an educated guess as to the system response, he could 
get close.

All this said, in 2012, I would rather the amplifier be simple gain, the 
inductor not loaded with capacitance and the filtering done past the 
amplifier. We aren't living in the era of 3 transistor circuits.

When delta-sigma converters came on the scene. I wisely found new design 
skills. [They replaced much analog filtering.] So better just to do the 
filtering in DSP IF there is no critical power budget.


On 3/17/2012 6:25 AM, Attila Kinali wrote:
> On Sat, 17 Mar 2012 06:13:28 -0700
> gary<lists at lazygranch.com>  wrote:
>
>> On 3/17/2012 5:44 AM, Attila Kinali wrote:
>>> On Sat, 17 Mar 2012 10:15:17 +0000
>>> "Poul-Henning Kamp"<phk at phk.freebsd.dk>   wrote:
>>>
>>>> Either you need to characterize the exact behaviour of your filter
>>>> and build the necessary compensation for its phase/frequency behaviour
>>>> into your receiver, or you need a very flat filter (both freq+phase)
>>>> in order to reliably recognize the proper zero-crossing to track.
>>>
>>> BTW: how do you compensate for the filter characteristics of your
>>> magnetic loop antenna?
>
>> Any filter's group delay can be equalized by all pass filters.
>>
>> Delay builds up at the filter corner. Since everything in the real world
>> is causal, you add delay outside that corner frequency but in the
>> passband to equalize it. This is to say, you can't remove delay, but
>> just add it to flatten out the group delay.
>
> Sorry, i asked in a misleading way. I didnt mean to ask what technique
> to use to flaten the phase delay, but rather how does phk know how the
> compensating filter should look like? For this, one needs to exactly
> characterize the antenna-amplifier chain...AFAIK
>
> 			Attila Kinali
>




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