tailieunhanh - Mobile and wireless communications physical layer development and implementation Part 15

Tham khảo tài liệu 'mobile and wireless communications physical layer development and implementation part 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Towards Performance Enhancement of Short Range Wireless Communications in Reliability - and Delay-Critical Applications 271 compatibility with the old server. It s connected directly to DECT and Linx modules. In the near future only Ethernet interface will be used to communicate with the server and therefore in the testing board we use two XPort devices. One is connected directly to communication modules. The other one is connected to microcontroller to be able to set and control communication parameters like RSSI values and communication channel number for monitoring and data logging to be used for further analysis. Linx HP3 Series transmitter and receiver are high-performance RF modules Linx 2007a Linx 2007b commonly used in wireless data transfer and industrial automation. They use popular 902-928 MHz frequency band. On the PCB we have possibility for serial channel selection of 100 channels by using microcontroller s I O ports. Anyway in case of problems with microcontroller s operation during the competition we have provided also parallel selection of 8 channels using octal rotary DIP switches. For digital data transmission Linx uses FSK modulation to ensure reliable performance. Equation 1 shows the FSK modulation formula. In FSK the modulating signal shifts the output frequency between two discrete values so called mark and space frequencies 5 Í Ac cos 2fÍ m nT b s 1 1 Ac cos 2fÍ m nTb - 1 Therefore comparing to On-Off Keying modulation FSK has increased noise immunity and ability to capture in the presence of multiple signals which is really helpful especially in such crowded band. Using those SIP style Linx modules we don t need any additional RF components except of the antenna of course . Receiver has an exceptional sensitivity of -100 dBm typical. The critical requirement for both modules performance was big ground plane on lower layer of PCB. To minimize losses we had to stick to the rules of designing microstrip as shown in Figure 1 the trace running