To implement our design, we decided to design two major components, the Data Buffer and Antenna. The Data Buffer is used to send commands and receive tag information the RFID reader and read the ultra sonic sensors analog output. The data buffer packages the sensor data and sends it to the Raspberry Pi. We also designed a UHF RFID antenna to read our tags at the range of approximently 1 meter. We decided to use an off the shelf RFID reader due to time constraints and budget concerns.
Team Designed Data Buffer PCB
We decided to create the databuffer for two reasons. The first is so all the sensor data could be brought into one device then packetized before transfer.The second reason why we implemented this we hoped to be able to run the Raspberry Pi at a low clock cycle to reduse power use.
Team Designed UHF Antenna
We wanted to design an antenna to read our RFID tags. After researching our options we determined that a circularly polarized patch antenna operating in the Ultra High Frequency (UHF) band would work best for our medium range specifications. The reason for circular polarization is to allow the user's RFID tag to be oriented in almost any position while still being read by the antenna. We decided on a center frequency of 915 Mhz. We were looking to achieve a return loss of at most -20dB at the 915MHz center frequency. In our design we achieved -27dB return loss which is better than we were hoping for. This allowed us to focus the antenna to recieve the backskattered signal from the RFID tag while preventing noise at the surrounding frequencies from being received.