How to use gr_clock_recovery_mm_cc

GNU Radio
1

Hi All,

In the gmsk.py, the gr.clock_recovery_mm_ff is used.

I want to use gr.clock_recovery_mm_cc (float omega, float gain_omega,
float
mu, float gain_mu) (which implements Mueller and Mller (M&M) based clock
recovery block with complex input, complex output) to replace the
gr.clock_recovery_mm_ff

I have done these in two steps:

  1. use the same parameters (used to init gr.clock_recovery_mm_ff) to
    init
    gr.clock_recovery_mm_cc.
    omege=2.000000, gain_omega=0.000625, mu=0.050000, gain_mu=0.050000,
    omega_relative_limit=0.005000

  2. move the clock recovery block forward before demod block
    self.connect(self, self.clock_recovery, self.fmdemod, self.slicer,
    self)

Before modification, if I run the benchmark program using gmsk, receive
rate
is almost 100%, but after my modification, receive rate drops to 0%.

Does my method have problem, any help is appreciated!

2

On Tue, Jun 7, 2011 at 9:13 AM, Shen W. [email protected]
wrote:

  1. use the same parameters (used to init gr.clock_recovery_mm_ff) to init
    Does my method have problem, any help is appreciated!

–
Wenbo

You HAVE to use the clock recovery after the demod. Pre demodulation,
you
don’t have the right type of signal to lock against.

Tom