P12311 RF Anechoic Chamber

P12311 RF Anechoic Chamber Instruction Manual Sheldon Palmer Danielle Walters

The anechoic chamber is a shielded enclosure that is used to measure the radiation pattern of any antenna under test. The measurement involves the distribution of radiated energy in space about a receiving antenna, plotting the received power or antenna pattern and finding its associated gain. The Chamber was characterized using two 2.4 GHz reflector antenna and the measurements were stored in a calibration file that is used by the radiation program to calculate the test antenna gain.

The inside of the chamber contain special RF absorption foam; which is use to attenuate any electromagnetic signals that may bounce of the wall or any metal structure in the chamber. The specular region of the chamber was calculated, and the absorber was aligned so as to attenuate any signals that maybe directed at the test antenna that bounce off the walls of the chamber. This reduces the noise around the test antenna, thus increasing the signal to noise ratio.

The chamber was calibrated using two 2.4 GHz 15 dBi Mini-Reflector Grid Wi-Fi antennas. The process uses the manufacturers’ gain data sheet and the measured receive power to calculate the losses in the cables, the free space losses inside the chamber and the gain of the test antenna. An offset number that is generated is added to the receive power of the test antenna; so as to accurately calculate the test antenna gain.

Calibration Program:

The program is located in the Start> All Program>Anechoic Chamber.

The Calibration process was done using a 2.4 GHz 15 dBi Mini-Reflector Grid Wi-Fi antenna and the frequency generator was set at 15 dBm and a frequency range between 2.35 and 2.45 GHz was used to characterize the chamber. The Gui for the calibration program is shown below; with the program being fully automated the user will need only to follow the instruction prompted by the pop up dialogue boxes. The antenna’s gain data in entered in the label column on the Gui and the frequency is calculated after the increment, start and stop frequencies are entered. The test antenna will need to be mounted at a height of 4 feet making sure the center of its effective aperture is in line with the center of the transmitting antenna. The program will generate the frequency, power measured and the offset; which is the losses due to the transmission cable and free space losses between the two antennas. These values are be stored the listed tables on the Gui and are used by the radiation program to calculate the gain of the test antenna.

 Note: The motor power box, the frequency generator and the spectrum analyzer need to be turn on before the lab-view Gui is launched. Both the Calibration and the Radiation programs are located on the same Gui and the default program is the Radiation; so if the calibration program is needed just click the such named button.

 Start the program by clicking the arrow icon shown below

 The next sequence of dialogue boxes will prompt the user through the remainder of the process.

 Next

Click the Begin Measurement button

located at the bottom of the Gui  Enter the below listed data/values

 Note: The program frequency default is GHz, so the user only needs to enter the interger value of the frequency

 The below dialogue box is a check by the program to see if the user has finished entering the data.

 Click the RF button

 The proram will then run, after which, each column on the Gui will be filled and save the data to a pre-existing calibration file.

The Radiation Measurment:  Note: The program is located in the Start> All Program>Anechoic Chamber.

 Start the program by clicking the arrow icon shown below

 The next sequence of dialogue boxes will prompt the user through the remainder of the process

 Next

Click the Begin Measurement button

located at the bottom of the Gui  Choose from the listed parameters below

 Set the signal generator frequency

 Click the RF button

 Once the program has completed the radiation plot the user will be prompted to look at the acquired data using the graph append option  Click Done Measurement button to exit the program