# Front-end Gain calibration Procedure

<h1 id="bkmrk-objective">Objective</h1>
<p id="bkmrk-measure-the-total-sy">Measure the total system gain at the output of the RSSI and equalize it.</p>
<h1 id="bkmrk-steps-to-follow">Steps to follow</h1>
<ul id="bkmrk-turn-on-equipment-sp">
<li>
<p>Turn on equipment</p>
<ul>
<li>Spectrum analizer</li>
<li>Power supply</li>
</ul>
</li>
<li>
<p>Configure to desired parameters</p>
<ul>
<li>Spectrum analizer
<ul>
<li>Set center frequency in the middle of VCO output band (6250MHz)</li>
<li>Set span to match the VCO output band (1400MHz)</li>
<li>Set RBW and VBW to an adecuate level</li>
</ul>
</li>
<li>Power supply
<ul>
<li>Set Voltage to 3.3V</li>
<li>Set current limit to 0.3A</li>
</ul>
</li>
</ul>
</li>
<li>
<p>Set up nucleo board and PC</p>
<ul>
<li>Make sure the proper code is loaded into the nucleo board</li>
</ul>
</li>
<li>
<ul>
<li>Connect the power supply to the payload:
<ul>
<li>Vcc to PoL (RED)</li>
<li>GND to GND (BLACK)</li>
</ul>
</li>
<li>Connect the DAC output to the DAC_In (GREEN)</li>
<li>Connect the ADC input to the ADC_Out</li>
<li>Load the IF Input with a 50 Ohm perfectly matched load.</li>
<li>Connect the spectrum analizer to the switched measuring pin (PURPLE)
<p>Make connections</p>
</li>
</ul>
<p><a href="https://wiki.nanosatlab.space/uploads/images/gallery/2023-04/top-k-band-testing-connections.PNG" target="_blank" rel="noopener"><img src="https://wiki.nanosatlab.space/uploads/images/gallery/2023-04/scaled-1680-/top-k-band-testing-connections.PNG" alt="Top_K-Band_Testing_Connections.PNG"></a><br></p>
<ul>
<li>Connect PC to ground (plug in the charger)</li>
<li>Connect necleo board to computer by USB</li>
</ul>
</li>
<li>
<p>Power on power supply</p>
</li>
<li>
<p>Begin the measurements procedure</p>
<ul>
<li>Run the flashed program in Debug mode</li>
<li>Once the program stops at the breakpoint, collect the calculated mean and plot it in a data processing software like Matlab.</li>
</ul>
</li>
<li>
<p>Realize the calibration</p>
<ul>
<li>Calculate the mean of the collected data and substract it from each frequency bin mean. This will be the deviation.</li>
<li>Extract the trend line from the deviation.</li>
<li>Subtract trend line function from the received RSSI value. This will be the calibrated measurement.</li>
</ul>
</li>
<li>
<p>Reboot the program and check if the equalization is now correct. If it&rsquo;s not correct repeat the previous step</p>
</li>
</ul>