Assume The E-field transmitted can be written as below The returned E-field at some time later is Time it took to travel to and from the object(target) is Substituting The received frequency can be calculated by taking time derivative of the quantity in red above and dividing by 2pi Here, The blue coloured quantity above is nothing but he Doppler shift frequency. Here the sign essentially indicates the target moving direction If the doppler shift is negative then the target is moving away from the radar and vice versa And thus the velocity can be written as
Below is simple MATLAB code for 2.4GHz dipole antenna. Normally the length of this dipole is λ/2 λ=c/f c is speed of light i.e. 300000000 m/s And f here is 2.4GHz And we found λ/2 to be 0.0625 We used length here to be 0.0600 since for this length we get good VSWR or we can say reflection is low. Code: d = dipole( 'Width' ,0.000525, 'Length' ,0.060) %This shows the length and width of the dipole %You can calculate the length as per lambda/2 and then optimize according to VSWR/Reflection coefficient you get show(d) freq = linspace(2e9,2.7e9,51); %This is frequency sweep figure; pattern(d,2.4e9) figure; vswr(d,freq,50) Below are the output figures Radiation Pattern of the antenna is almost Omni-directional and it's like a donut shape. In the figure below, you can see VSWR is below 2 and this is good value
FMCW is a Radar which measures both speed and distance of the target object. In CW Radar only speed is measured while in FMCW both speed and distance is measured. This distance measurement is achieved by frequency modulated wave. There are different frequency modulation waveforms are used such as sawtooth, triangular, square, sine, and stepped modulation. Amongst these Sawtooth and Traingular are most widely used to change the frequency of EM wave. How does it work??? updating...
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