Compensate for carrier frequency offset for PAM, PSK, or QAM
Synchronization
The Coarse Frequency Compensator block compensates for a carrier frequency offset for BPSK, QPSK, OQPSK, 8PSK, PAM, and QAM modulation schemes. The block accepts a single input signal. To obtain an estimate of the frequency offset in Hz, select the Estimated frequency offset output port check box. The block accepts a sample or framebased complex input signal and returns a complex output signal and a real frequency offset estimate. The output signal has the same dimensions as the input signal. The frequency offset estimate is a scalar.
Specify the modulation type as BPSK
,
QPSK
, OQPSK
,
8PSK
, PAM
, or
QAM
.
The default setting is QAM
.
Specify the frequency offset estimation algorithm as
FFTbased
or
Correlationbased
. This parameter appears
when Modulation type of input signal is
BPSK
, QPSK
,
8PSK
, or
PAM
.
The table shows the allowable combinations of the modulation type and the estimation algorithm.
Modulation  FFTBased Algorithm  CorrelationBased Algorithm 

BPSK , QPSK ,
8PSK , PAM  ✓  ✓ 
OQPSK , QAM  ✓ 
Specify the frequency resolution in Hz as a positive real scalar. This
option is available when the FFTbased
algorithm
is used. The default setting is 0.001
Hz.
Specify the number of samples per symbol as a positive integer scalar greater than or equal to 4. The default setting is 4.
Specify the maximum frequency offset in Hz as a positive real scalar. This
option is appears when you set Estimation algorithm to
Correlationbased
. The default setting is
0.05
Hz.
Select this check box to provide the estimated frequency offset to an output port. The default for this parameter is selected.
Select the simulation mode.
Code generation
On the first model run, simulate and generate code for the block using only MATLAB^{®} functions supported for code generation. If the structure of the block does not change, subsequent model runs do not regenerate the code.
If the simulation mode is Code
generation
, System objects accept a maximum of
nine inputs.
Interpreted execution
Simulate your model using all supported MATLAB functions. Choosing this option can slow simulation performance.
The default setting is Code generation
.
This block implements the algorithm, inputs, and outputs described on the comm.CoarseFrequencyCompensator
reference page. The object properties
correspond to the block parameters.
Correct for a frequency offset imposed on a noisy 8PSK channel by using the Coarse Frequency Compensator block.
Open the doc_coarsefreqcomp model.
Open the dialog boxes to verify these parameter values:
Random Integer Generator —
Sample time is 1e4
, which is
equivalent to a 10 ksym/sec symbol rate.
Raised Cosine Transmit Filter
— Output samples per symbol is
4
.
AWGN Channel —
Mode is Signal to noise ratio
(SNR)
and SNR (dB) is
20
.
Phase/Frequency Offset —
Frequency offset (Hz) is
2000
.
Coarse Frequency Compensator
— Estimation algorithm is
FFTbased
and Frequency resolution
(Hz) is 1
.
Run the model. The Spectrum Analyzer block shows both the frequency offset signal and the compensated signal. In addition, the Display block shows the estimate of the frequency offset. Observe that the spectrum plot shows that the Coarse Frequency Compensator correctly centers the signal around 0 Hz. Additionally, the display shows that the estimated frequency offset is 2000 Hz.
Adjust the parameters in the Phase/Frequency Offset and Coarse Frequency Compensator blocks and see their effect on frequency compensation performance.
Port  Supported Data Types 

Signal Input 

Signal Output 

Frequency Estimate 

[1] Luise, M. and R. Regiannini. “Carrier recovery in alldigital modems for burstmode transmissions.” IEEE^{®} Transactions on Communications.Vol. 43, No. 2, 3, 4, Feb/Mar/April, 1995, pp. 1169–1178.
[2] Wang, Y., K. Shi, and E. Serpedi. “NonDataAided Feedforward Carrier Frequency Offset Estimators for QAM Constellations: A Nonlinear LeastSquares Approach.” EURASIP Journal on Applied Signal Processing. 2004:13, pp. 1993–2001.
[3] Nakagawa, T., M. Matsui, T. Kobayashi, K. Ishihara, R. Kudo, M. Mizoguchi, and Y. Miyamoto. “NonDataAided WideRange Frequency Offset Estimator for QAM Optical Coherent Receivers.” Optical Fiber Communication Conference and Exposition (OFC/NFOEC), 2011 and the National Fiber Optic Engineers Conference. March 2011, pp. 1–3.