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From: gobruins on 22 Mar 2010 14:20
I was wondering how to do carrier synchronization for CPFSK signals?

I want to decode the CPFSK signal by computing the phase difference. The
shape of the phase difference is similar to the following plot
|---| |---| fc+fd/2
- - -|- -| - | - | - - - fc
---| |---| |--- fc-fd/2

where fc is the carrier, fd is the peak frequency deviation.

Before send this demodulated data into the soft slicer, I have to build the
sample clock and recover the carrier frequency.

I plan to use the Gardner (or similar) detector to do the timing
synchronization. The input to the TED is just the phase difference as shown
above.

But　Ｉ　ａｍ　ｎｏｔ　ｓｕｒｅ　ｈｏｗ　ｔｏ　ｄｏ　ｔｈｅ　ｃａｒｒｉｅｒ　ｓｙｎｃｈｒｏｎｉｃａｔｉｏｎ．　Can
anyone point me a method how to do this?

Thanks a lot!
From: Darol Klawetter on 22 Mar 2010 16:01
On Mar 22, 1:20 pm, "gobruins" <chunmei.kang(a)n_o_s_p_a_m.gmail.com>
wrote:
> I was wondering how to do carrier synchronization for CPFSK signals?
>
> I want to decode the CPFSK signal by computing the phase difference. The
> shape of the phase difference is similar to the following plot
>       |---|   |---|       fc+fd/2
>  - - -|- -| - | - | - - - fc
>    ---|   |---|   |---    fc-fd/2
>
> where fc is the carrier, fd is the peak frequency deviation.
>
> Before send this demodulated data into the soft slicer, I have to build the
> sample clock and recover the carrier frequency.
>
> I plan to use the Gardner (or similar) detector to do the timing
> synchronization. The input to the TED is just the phase difference as shown
> above.
>
> But　Ｉ　ａｍ　ｎｏｔ　ｓｕｒｅ　ｈｏｗ　ｔｏ　ｄｏ　ｔｈｅ　ｃａｒｒｉｅｒ　ｓｙｎｃｈｒｏｎｉｃａｔｉｏｎ．　Can
> anyone point me a method how to do this?
>
> Thanks a lot!

Search for "costas loop" if you must do coherent demodulation. If non-
coherent (i.e., no carrier recovery needed) demodulation is adequate,
search for "differential detector."
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