P11342 RF Test Chamber Assembly Plan Jason Blackman & Dan Pulito https://edge.rit.edu/content/P11342/public/Home Reference Material.zip (located on the above web page) contains documents referenced throughout this assembly plan Required Materials (more detailed info about parts can be found on the BOM)

• 37”x27”x9” Aluminum Box (as per ‘Shielded Test Fixture.pdf’ pages 18,19) • 37”x27” Aluminum Cover (as per ‘Shielded Test Fixture.pdf’ page 23) • Six 24.25”x24.25”x3/4” Pieces of Eccosorb LS-30 Absorbent Foam • Five feet of 1” thick Double-sided Adhesive Velcro • Sixteen 4-40 ½” screws • Sixteen 4-40 nuts • Thirty-two 4-40 washers • Four corner braces • Lumber (3/4” thick) • Aluminum (1 ¼” wide by ¼” thick) • DC Motor & encoder • Motor controller board • Microprocessor board • DAQ board (w/ USB to USB type B cable) • Atheros Wi-Fi USB Module • USB 6’ Extender cable • USB 1.5’ Shielded Cable • SMA female to female Bulkhead connector • Two Coax SMA male to male cables, ~2’ • 6V power supply (>500mA) • Wires • Serial Cable (DB9) • Motor bracket • Two Mounting hubs • Five 2-56 screws and nuts

Required Tools

• Screwdriver • Exact-o knife • Power drill • Crescent Wrench • Ban saw • End mill • Lathe • Belt Sander • Drill press

Step 1: Creating the Box and Lid If starting from scratch, first figure out what holes will be needed before machining the box. The drawing can be found on pages 18 and 19 of ‘Shielded Test Fixture.pdf in the reference material section of the P11342 web site. The only holes that were used in this project were the rectangular hole on the bottom left of the longer side, and one of the small circular holes on the shorter side. The box had already been made to the specifications found in that document, however, and this assembly plan deals with some of the necessary modifications to make the box more shielded. If you are machining the box from scratch, do not put any holes in it that you won’t be using. This will only add ways for RF to leak in or out of the chamber. The lid can be made exactly to the specifications on page 23 of the same document mentioned earlier. Step 2: Creating Aluminum Covers For this project, four covers were made to block holes in the box. One of them is being used to let a USB cable go through, but the other three are blanks. These won’t need to be machined if the box was built to the desired specifications. The drawings for these covers can be found in the reference material on the web site, listed as ‘P11342 covers 1-3’ and ‘P11342 cover 4’. Using a ban saw, cut the aluminum slab into rectangles of the desired lengths. Drill four holes in each plate where screws will secure the cover to the box. Use an end mill to create a hole that will fit the cable/connector that needs to go through the box. A USB cable is used in this project, and the cover with the hole in the center on drawing ‘P11342 covers1-3’ is for that. Once those are made, place them on the outside of the box, covering the four rectangular holes on the longer side of the box. Insert the 4-40 screws in each of the holes from the inside of the box, so they are sticking out on the outside. Place a washer on either side of the screw, and secure them in place with a nut. This can be seen below.

Step 3: Creating Collars for the Platform Shaft Approximately 9 inches from the end wall and centered between the side walls, a ¼” hole needs to be drilled in the box for the platform shaft. This can be seen below.

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There will be two collars (mounting hubs) around this hole to provide support for the platform shaft. The mounting hubs purchased need to be modified to be able to fit the ¼” shaft through them. Using a lathe, increase the size of the hole on top of the hub (shown below) to 0.252”. This will allow the shaft to rotate without too much friction.

Place one of the newly created collars on the inside of the box, around the hole with the large side flat against the bottom of the chamber. Using a power drill, create 5 holes in the bottom of the chamber using the collar as a guide. These will secure the collars in place. Once the holes are drilled, place the other collar on the outside of the box directly below the first one, turned upside down. Place 2-56 screws in each of the holes from the top, and secure them in place with nuts. An image showing the orientation described can be seen below.

Step 4: Making the Platform Shaft Take the threaded rod and cut it to size using a ban saw. For this project, a length of 6” was required. Use a belt sander to smooth any sharp edges. On one of the ends, use an end mill to create a flat surface for a set screw. This surface needs to be about 1” long, starting at the end of the rod. This is shown below.

Top View of End of Threaded Rod

Step 5: Building a Table In order to keep the motor for the platform on the outside of the chamber, the box needs to be elevated. A plank of wood 39” x 24” x ¾” is used for the surface of the table. This is long enough to that a 27” x 1”x ¾” can be attached (using wood screws) to the surface on either side of the chamber to hold it in place. This can be seen below.

Since the width of the table is shorter than the chamber, L-brackets have to be used to secure the chamber in the other direction. Four brackets are used, two on each side, to ensure that the box doesn’t move relative to the table. One of the brackets can be seen below.

The legs of the table are somewhat arbitrary, as long as they provide enough support for the chamber. The height of the legs was chosen to be 7”, but this could be changed depending on the motor used. A platform to house the motor and its associated circuitry is built. The dimensions of this are 6” x 6” x 4” and the same 3/4 “ wood is used from the

rest of the table. It is better to use metal for this, since wood warps and creates an uneven surface for the motor to attach to. The general setup of this can be seen below.

Attach the bracket to the motor and screw it into the platform that was built. This can be seen below.

Drill a ½” thick hole in the surface of the table that perfectly aligns with the hole in the bottom of the box. The table then can be placed on top of the box with the collar inserted into this hole.

Insert the threaded rod into the hole in the bottom of the box, with the end with the flat surface pointing downward. Line the motor up with the rod with a coupler and secure the platform in place once the motor is perfectly aligned, allowing the rod to spin with minimal friction. The “tunnel” created by the two collars might need to be sanded out using a file for this to work. Step 6: Lining the Chamber with Foam Cutting the sheets of RF absorbent foam to the correct size is very important. The material is fragile so be sure to avoid tearing it. A large paper cutter was used to make clean cuts, but if that isn’t available then an Exact-o knife will work fine. The sizes and quantities, along with reference designators, of pieces are listed below. 24.25”x24.25” 2 A 13 7/17” x 6 5/16” 4 B 24.25”x5 3/8” 2 C 24.25”x1 5/16” 2 D 24.25” x 7.5” 4 E 7.5”x6 5/16” 2 F 24.25x3/4” 1 G 5 3/8”x3/4” 2 H 7.5” x 1 3/8” 2 I Start with the bottom of the chamber. A hole needs to be cut for the collar to go through. An Exact-o knife can be used for this. The floor plan for the bottom of the chamber can be seen below.

Start by placing the center piece and then the surrounding ones. They should fit snugly, and are held in place by friction. The two longer sides are lined next, and the floor plan for these can be seen below.

In order to wedge this in place, use long strips of 11/16” foam in between the top of the foam pieces shown and the lip of the chamber. Any hole for connectors that are used can be cut out using an Exact-o knife, as done previously. The two ends are lined as shown below.

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The top side is a little trickier, since friction won’t hold the foam in place. Also, there is a 1” gap for the lip of the chamber, so the placement has to be precise. Adhesive Velcro is used to hold the pieces in place. The floor plan can be seen below.

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Step 7: Setting up the Motor System A 6V DC power adapter can be attached directly to the Vs input terminal on the Bot Board II. Make sure the jumper is in place that says Vs-Vl. Solder a wire from P15 on the Bot Board to S1 on the Motor controller board. Solder two wires from the middle and end pins in the same row as P7 to the B+ and B- inputs on the motor controller. Make sure the jumper for this I/O bank is set to be Vs and not 5V, as the motor controller needs at least 6V. Connect the yellow and green wires from the motor encoder to P0 and P1 (green in P0). The red and black wires should be connected anywhere on the board that has 5V and ground next to each other. Connect a wire from any of the ground pins to pin 32 on the USB-6009 DAQ board. Also connect P4 on the bot board to P19 on the DAQ, P5 on the bot board to P17 on the DAQ, and P9 on the bot board to P18 on the DAQ. Then connect the DAQ to the PC using a USB cable. Connect an RS-232 cable to the bot board to program it. Basic Micro Studio is used to program it. The motor code is available on the web site. Program it onto the microprocessor. The switches on the motor controller board should be in the position 101001 from left to right. This corresponds to 38400 baud rate. Download the Tektronix drivers from the web site and place them in the Labview drivers folder. Also download the Labview VI on the web site. This will take the automated measurements of radiation pattern. Step 8: Obtaining a Radiation Pattern Attach a patch antenna (or any microstrip antenna) to the rotating platform. With the power off, rotate the platform so that it is facing the wall to its right, where the opposite end would be facing forward. Use USB cables to connect up an Atheros Wi-Fi module and place it 21” in the center of the chamber. Run the atheros.bat file found on the web site, and at the main menu press ‘C’ and then at the next menu press ‘S’. Cover the chamber. Select the parameters in the Labview VI such as frequency and range. Apply power to the microprocessor board and start the Labview VI. When it is finished taking measurements, it will prompt for a file location to save the output. Import that into matlab and run the script found on the web site to plot the radiation pattern.