I am trying to simulate a radar-transmitted signal with a 4.5 Hz clock frequency and 1.8 GHz carrier frequency. I generated the carrier signal and a rectangle shape pulse signal, then multiplied in time. My pulse-width is 444ps. I have two questions about my results.

First of all, the result of the carrier signal seems true. But does the sidelobe behavior of the rectangle pulse should be weakened by at each n/pulse width, n=integer.

Second, I am not sure if the modulation output is true or not. Do I need to see two peaks at -1.8GHz and 1.8GHz? What am I missing? Any idea?

Results are given using the following order as SpectrumCarrier, SpectrumPulse and SpectrumModulatedSignal.

UPDATE: By increasing the clock rate, I got the results which I wanted. The results are given in below.

Here is the code:

ClockFreq=20e9;        %Hz
tsampling=1/ClockFreq;   % seconds
PRI=6.65e-9;            % Pulse Repetition Interval, seconds
PRF=1/PRI;              % Pulse Repetition Frequency, Hz.
tlocal=0:tsampling:PRI;
NumberofSamplesLocal=length(tlocal);
ffres=ClockFreq/NumberofSamplesLocal;

NumberUnambiguousRangeProfile=17;
timewindow=NumberUnambiguousRangeProfile*(PRI);     %seconds
CarrierFreq=12*ffres;    %Hz
CarrierAmplitude=1
PulseAmplitude=1;

% Transmitted Signal

CarrierSignal=CarrierAmplitude*cos(2*pi*CarrierFreq.*tlocal);
PulseWidth=ones(1,10);
ListeningTime=zeros(1, NumberofSamplesLocal-length(PulseWidth));
PulseSignal=PulseAmplitude.*[PulseWidth ListeningTime];

% Modulation of the Signal
FourierSampleNumber=10000;
ff=-ClockFreq/2: ClockFreq/FourierSampleNumber:ClockFreq/2-
ClockFreq/FourierSampleNumber;
SpectrumCarrier=fftshift(fft(CarrierSignal,FourierSampleNumber));
SpectrumPulse=fftshift(fft(PulseSignal,FourierSampleNumber));
ModulatedSignal=CarrierSignal.*PulseSignal;
SpectrumModulatedSignal=fftshift(fft(ModulatedSignal, 
FourierSampleNumber));