Critical Design Review

1. Critical Design Review Team E – Shrey Bhatnagar, Ben Buyanovsky, Tamara Gaynes, Tim Reeb

2. Objective • Build a cell phone signal booster • This will be used in the WellCar • Plan is to power via USB for versatility • Will place focus on Sprint’s bands but also work for universal applicability • Want to increase signal power whilst in remote areas of Kansas

3. System Block Diagram

4. Power Analysis

5. Key Technologies • Will use SMA female connectors on our PCBs • Need N-type male to SMA male adapters • Connect PCBs to splitters • Need short N-type male coaxial cables • Three way splitters to the two way splitters • Need 5 foot N-type male coaxial cables • Connect antennas to 3-way splitters

6. System Implementation • We have three stages of implementation: • Transmit/Receive • Splitting/Combining • Amplification/Filtering

7. Transmit/Receive • Consists of two antennas • One inside vehicle • One outside vehicle • Outside antenna will be used to receive signal power from cell phone towers and send information to them • Inside antenna will be used to transmit the signal to the cellular devices and receive data from the cell phones to send back out • Both directional antennas

8. Splitting/Combining • Used to split the incoming signal into the three necessary bands • 824-894 MHz • 1850-1990 MHz • 2500-2690 MHz • Each will be further split into the uplink and downlink channels • N-type female connectors

9. Amplification/Filtering • 5 VDC will be provided to the amplifiers through the use of a USB interface • 12 surface mount amplifiers with approximately 20 dB of gain each • Since we found that there is about -50 dB of shielding between the antennas • Found 6 filters that perfectly match our need for the necessary channels • All of these components will be surface mounted and custom PCBs will be ordered

10. Products Using • Amplifiers • Splitters

11. Products Using • Filters • Antennas

12. Products Using • PCB fabrication • We will need 3 PCB boards fabricated for the project • Cost about $360 • Connectors

13. Test Results • First test was primarily to ensure the antennas had been shipped and received without damage. The test proved successful. • Second test was for mutual coupling between the antennas, and our results found -50 dBm of isolation between them. The test proved successful, as it showed mutual coupling should be a minimal issue. • Third test was to gauge the output power of the tower while in close proximity to it, and the results were favorable, showing an output power of -35 dBm.

14. Schedule

15. Status • Completed isolation testing for the antennas • Have also ordered the majority of our parts • Been working on figuring out surface mount soldering • We are going to start laying out the PCB design this week and get that finished so we can get it ordered • We will also put in orders for the parts we do not have yet.

16. Product Assembly • Once we have out working parts together and the product as a whole assembled, we will work on packaging • Want to attach our parts to a sheet of metal and encase it that way but we are also open to suggestions • Since we were unable to find all surface mount parts for power reasons, it will be a bit bigger and heavier than previously planned • Now aiming for a more flat design to be mounted on the inside of the roof of the vehicle such that it takes up minimal head room

17. Challenges • Two antennas in close proximity • Consider the isolation before we consider the gain • If the system has too much gain, we will have coupling and the antennas will oscillate • Finding parts that can handle high power was also challenging • There is a possibility that there will be decent cell phone service in different places • To account for that, our components need to be able to handle high power and we could not find splitters that were surface mounted to accomplish this

18. Questions? Credit to Sunstone Circuits for discounting PCBs for students.