AnsweredAssumed Answered

GFSK modulation in ADF7012

Question asked by BTR on Nov 2, 2010
Latest reply on Feb 9, 2015 by rbrennan

I have a few questions regarding ADF7012:

-What is the processing delay of the Gaussian filter for GFSK?

-Is it possible to change GFSK BT value to less than 0.5?

-What methods can be used for variable-modulation-index (continous) transmission?

In my case I need to have modulation indecies which are not multiple of power-of-2 which means I need to change other parameters (such as divide factor, Fpfd) in order to keep baud rate constant while changing modulation index. I was thinking of updating N, R, and Mod registers at max speed before next bit goes through TxDATA, but then that would create a glitch on CP output, wouldn't?.

-Is there a way to load multiple registers at once such that glitch happens fast and not spread over writing of 3 registers?

-I was also thinking of tri-stating CP internally or externally (not sure which one gives better glitch performance) during register update. Is this a viable solution?

-Is there simlar devices which have mudulation idex multiplier (not power of 2)?

-What happens to TxCLK during register changes (N,R, Fpfd changes, but baud rate is the same)?

 

Updating 3 registers (88bits) at max speed: 4.5us. Bit duration on TxDATA: 1/9.6K=104us.

 

my specs are:

Fout: around 160 MHz (VCO divider of 4)

channel spacing: 50 KHz

Fout freq accuracy: 400 Hz

XTAL freq: 14,745,600 Hz (seems to be best for accuracy for various modulation indecies, and divisible by 9.6K)

baud rate: 9.6 Kbps

Modulation indecies: 0.5 and 3.65 (with 8% accuracy)

Modulation: binary GFSK

 

-Thanks

Outcomes