[time-nuts] WWVB BPSK Receiver Project?

Jim Lux jimlux at earthlink.net
Thu Mar 15 13:26:43 UTC 2012


On 3/14/12 9:14 PM, J. Forster wrote:
>> On 3/14/12 8:07 PM, J. Forster wrote:
>>>> John
>>>> Like your thought. I seem to remember costas loops work like that to
>>>> recover the carrier.
>>>
>>> Paul,
>>>
>>> It recovers a bipolar signal to steer the local VCO as well as the
>>> data..
>>> It also needs a quadratue hybrid at the VCO frequency (although it might
>>> be fairly easy to make a quadrature oscillator vat 60 kHz.)
>>
>> One easy scheme is to make your VCO run at a multiple and divide down to
>> generate the two quadrature square waves.
>
> Doesn't look like that works with the HP 117A. I don't know about other
> receivers.
>
>>>> Had seen it in amsat many years ago. So perhaps an approach is to limit
>>>> if possible the incoming signal.
>>>
>>> I'm not sure if it works properly with clipped (digital) dignals, off
>>> hand.
>>
>> Yes it will.
>
> Not w/o a quadrature drive to the mixer/multiplier. A square wave,
> multiplied by itself, has the same output as input.

Oh... I was assuming you had the two quadrature square waves (which are 
just like the saturated LO for the mixer in RF land)



>
>>>> Though further simple dumb thought. A NE602 or SA602 or also teh 612
>>>> series. All the same mixer circuit (Or multiplier)will double the
>>>> incoming
>>>> frequency if you delay the incoming by 90 degrees I think.
>>>
>>> Sine and Cosine are orthogonal. You need to do (Sine)*(Sine)
>>>
>>> sin^2 (wt) = 1/2(1 - cos (2wt)
>>>
>>
>> This is like the classic squaring technique to receive PN coded signals
>> without knowing the code.  (it's used in some "codeless" GPS receivers..
>> you can retrieve frequency and phase)
>
> A Costas Loop recovers the bit stream and the carrier frequency (from the
> local VCO) from a BPSK. It is self syncronizing.


Yes.. but if you don't care about the bitstream, and you want simpler 
hardware, squaring works. (especially if the modulator doesn't have good 
carrier suppression)




More information about the Time-nuts_lists.febo.com mailing list