[time-nuts] WWVB BPSK Receiver Project?
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:
>>>> Like your thought. I seem to remember costas loops work like that to
>>>> recover the carrier.
>>> It recovers a bipolar signal to steer the local VCO as well as the
>>> 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
>>>> 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
>> 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
>>>> 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
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