[b,a] = cheby1(n,Rp,Wp,ftype) designs a lowpass, highpass, bandpass, or bandstop Chebyshev Type I filter, depending on the value of ftype and the number of elements of Wp. The resulting bandpass and bandstop designs are of order 2 n.

Interference Removal Using Sidelobe Canceller A common requirement when synthesizing beam patterns is pointing a null towards a given arrival direction. This helps suppress interference from that direction and improves the signal-to-interference ratio.

The interference is not always malicious- an airport radar system may need to suppress interference from a nearby radio station. In this case, the position of the radio station is known and a sidelobe cancellation algorithm can be used to remove the interference. Sidelobe cancellation is useful for suppressing interference that enters through the array's sidelobes. In this case, because the interference direction is known, the algorithm is simple. Form a beam that points towards the interference direction, then scale the beam weights and subtract scaled weights from the weights for the beam patterns that point towards any other look direction.

This process always places a strong null in the interference direction. The following example shows how to design the weights of the radar so that it scans between -30 and 30 degrees yet always keeps a null at 40 degrees. Assume that the radar uses a 10-element ULA that is parallel to the ground and that the known radio interference arrives from 40 degrees azimuth. Skachatj karti dlya batelfild 2 dlya odinochnoj igri torrentom pc. The 3D radiation patterns exhibits some symmetries in both azimuth and elevation cuts. Therefore, the pattern may be best obtained using a uniform rectangular array (URA). It is also clear from the plot that there is no energy radiated toward back of the array. Next, determine the size of the array.

To avoid grating lobes, the element spacing is set to half wavelength. For a URA, the sizes along the azimuth and elevation directions can be derived from the required beamwidths along azimuth and elevation directions, respectively. In the case of half wavelength spacing, the number of elements along a certain direction can be approximated. The figure shows that the synthesized array exceeds the beamwidth requirement of the desired pattern. However, the sidelobes are much larger than the desired pattern.

You can reduce the sidelobes by applying a windowing operation to the array. Because the URA can be considered to be the combination of two separable uniform linear arrays (ULA), the window can be designed independently along both the azimuth and elevation directions using familiar filter design methods. The code below shows how to obtain the windows for azimuth and elevation directions. AzSidelobe = 20; Ap = 0.1;% Passband ripples AzWeights = designfilt( 'lowpassfir', 'FilterOrder',N_col-1. 'CutoffFrequency',azco(2)/90, 'PassbandRipple',0.1.

'StopBandAttenuation',AzSidelobe); azw = AzWeights.Coefficients; ElSidelobe = 30; ElWeights = designfilt( 'lowpassfir', 'FilterOrder',N_row-1. 'CutoffFrequency',elco(2)/90, 'PassbandRipple',0.1. 'StopBandAttenuation',ElSidelobe); elw = ElWeights.Coefficients;% Assign the weights to the array ura.Taper = elw(:)*azw(:).' ;% Compare the pattern helperArraySynthesisComparison(ura,mysteryAntenna,fc,c). N_row = N_row+2;% trial and error N_col = N_col-3;% trial and error AzSidelobe = 26; ElSidelobe = 35; AzWeights = designfilt( 'lowpassfir', 'FilterOrder',N_col-1. 'CutoffFrequency',azco(2)/90, 'PassbandRipple',0.1. 'StopBandAttenuation',AzSidelobe); azw = AzWeights.Coefficients; ElWeights = designfilt( 'lowpassfir', 'FilterOrder',N_row-1.

'CutoffFrequency',elco(2)/90, 'PassbandRipple',0.1. 'StopBandAttenuation',ElSidelobe); elw = ElWeights.Coefficients; ura = phased.URA([N_row N_col],[lambda/2 lambda/2]); ura.Element.BackBaffled = true; ura.Taper = elw(:)*azw(:).' ; helperArraySynthesisComparison(ura,mysteryAntenna,fc,c).