Recover symbol timing phase using early-late gate method
Note: Early-Late Gate Timing Recovery will be removed in a future release. Use the Symbol Synchronizer block instead. |
Timing Phase Recovery sublibrary of Synchronization
The Early-Late Gate Timing Recovery block recovers the symbol timing phase of the input signal using the early-late gate method. This block implements a non-data-aided feedback method.
By default, the block has one input port. Typically, the input signal is the output of a receive filter that is matched to the transmitting pulse shape.
This block accepts a scalar-valued or column vector input signal. The input uses N samples to represent each symbol, where N > 1 is the Samples per symbol parameter.
For a column vector input signal, the block operates in single-rate processing mode. In this mode, the output signal inherits its sample rate from the input signal. The input length must be a multiple of N.
For a scalar input signal, the block operates in multirate processing mode. In this mode, the input and output signals have different sample rates. The output sample rate equals N multiplied by the input sample rate.
This block accepts input signals of type Double or Single
If you set the Reset parameter to On
nonzero input via port
, then the block has a second
input port, labeled Rst
. The Rst
input
determines when the timing estimation process restarts, and must be
a scalar.
If the input signal is a scalar value, the sample
time of the Rst
input equals the symbol period
If the input signal is a column vector, the sample
time of the Rst
input equals the input port sample
time
This block accepts reset signals of type Double or Boolean
The block has two output ports, labeled Sym
and Ph
:
The Sym
output is the result of
applying the estimated phase correction to the input signal. This
output is the signal value for each symbol, which can be used for
decision purposes. The values in the Sym
output
occur at the symbol rate:
For a column vector input signal of length N*R,
the Sym
output is a column vector of length R having
the same sample rate as the input signal.
For a scalar input signal, the sample rate of the Sym
output
equals N multiplied by the input sample rate.
The Ph
output gives the phase estimate
for each symbol in the input.
The Ph
output contains nonnegative real numbers
less than N. Noninteger values for the phase estimate
correspond to interpolated values that lie between two values of the
input signal. The sample time of the Ph
output
is the same as that of the Sym
output.
Note
If the |
The output signal inherits its data type from the input signal.
When the input signal is a vector, this block incurs a delay of two symbols. When the input signal is a scalar, this block incurs a delay of three symbols.
The number of samples, N, that represent each symbol in the input signal. This must be greater than 1.
A positive real number representing the step size that the block uses for updating successive phase estimates. Typically, this number is less than 1/N, which corresponds to a slowly varying phase.
This parameter is tunable in normal mode, Accelerator mode and Rapid Accelerator mode. If you use the Simulink^{®} Coder™ rapid simulation (RSIM) target to build an RSIM executable, then you can tune the parameter without recompiling the model. For more information, see Tunable Parameters (Simulink) in the Simulink User's Guide.
Determines whether and under what circumstances the block restarts
the phase estimation process. Choices are None
, Every
frame
, and On nonzero input via port
.
The last option causes the block to have a second input port, labeled
Rst.
This block uses a timing error detector whose result for the kth symbol is e(k), given by
$$\begin{array}{c}e(k)={a}_{I}(k)+{a}_{Q}(k)\\ {a}_{I}(k)={y}_{I}(kT+{d}_{k})\left\{{y}_{I}(kT+T/2+{d}_{k})-{y}_{I}(kT-T/2+{d}_{k-1})\right\}\\ {a}_{Q}(k)={y}_{Q}(kT+{d}_{k})\left\{{y}_{Q}(kT+T/2+{d}_{k})-{y}_{Q}(kT-T/2+{d}_{k-1})\right\}\end{array}$$
where
y_{I} and y_{Q} are the in-phase and quadrature components, respectively, of the block's input signal
T is the symbol period
d_{k} is the phase estimate for the kth symbol
[1] Mengali, Umberto and Aldo N. D'Andrea, Synchronization Techniques for Digital Receivers, New York, Plenum Press, 1997.
[2] Sklar, Bernard. Digital Communications: Fundamentals and Applications. Englewood Cliffs, N.J., Prentice-Hall, 1988.