Construct flat Doppler spectrum object
dop = doppler.flat
dop = doppler.flat creates a flat Doppler spectrum object that is to be used for the DopplerSpectrum property of a channel object (created with either the rayleighchan or the ricianchan function). The maximum Doppler shift of the flat Doppler spectrum object is specified by the MaxDopplerShift property of the channel object.
The flat Doppler spectrum object contains only one property, SpectrumType, which is read-only and has a fixed value of 'Flat'.
In a 3-D isotropic scattering environment, where the angles of arrival are uniformly distributed in the azimuth and elevation planes, the Doppler spectrum is found theoretically to be flat . A flat Doppler spectrum is also specified in some cases of the ANSI J-STD-008 reference channel models for PCS, for both outdoor (pedestrian) and indoor (commercial)  applications.
The normalized flat Doppler power spectrum is given analytically by:
where is the maximum Doppler frequency.
This example shows how to create a Rayleigh channel object with a flat Doppler spectrum.
Set the sample time and maximum Doppler shift.
ts = 1e-6; % sec fd = 50; % Hz
Create the Rayleigh channel object.
chan = rayleighchan(ts,fd);
Observe that the default Doppler spectrum property, SpectrumType, is 'Jakes' .
ans = SpectrumType: 'Jakes'
Change the Doppler spectrum property of the channel by using doppler.flat.
chan.DopplerSpectrum = doppler.flat
chan = ChannelType: 'Rayleigh' InputSamplePeriod: 1.0000e-06 DopplerSpectrum: [1x1 doppler.flat] MaxDopplerShift: 50 PathDelays: 0 AvgPathGaindB: 0 NormalizePathGains: 1 StoreHistory: 0 StorePathGains: 0 PathGains: -0.6760 + 0.6319i ChannelFilterDelay: 0 ResetBeforeFiltering: 1 NumSamplesProcessed: 0
 ANSI J-STD-008, Personal Station-Base Station Compatibility Requirements for 1.8 to 2.0 GHz Code Division Multiple Access (CDMA) Personal Communications Systems, March 1995.
 Clarke, R. H., and Khoo, W. L., "3-D Mobile Radio Channel Statistics", IEEE Trans. Veh. Technol., Vol. 46, No. 3, pp. 798–799, August 1997.