1. WIRELESS MODEM for 950 MHz DIGITAL COMMUNICATION Nerdev Sharma 19991028

2. Continuing the presentation How the Wireless Modem works? What is the user Overview? How to use the Wireless Modem?

3. Starting the Wireless Modem Make all the connections. Set the transmitting and receiving frequencies. Send 24 bit A B C D words sequence through parallel port to chip. Start Data Transmission

4. Example DDS word sent to the chip DDS WORDS

5. C and D Words Control the Different Components on Chip

6. Transmit / Receive Modes A modem should be in either of the modes at a time i.e. either transmitting or receiving. To change the mode send a signal to the MODE pin of the chip.

7. TRANSMITTER Transmit data at a fixed data rate 19.2kbps here. Sends bit sequence 10101010101……. to train the receiver. After training start sending NRZ data.

8. RECEIVER Two Modes Learn Mode Hold Mode In learn Mode an external capacitor is charged to a dc voltage that is proportional to the average demodulation dc level for the known learning sequence i.e. 101010…. In Hold Mode chip correctly detects NRZ encoded data so now need to worry about long sequences of 0’s and 1’s.

9. User Interface for the Device

10. Computer Interface Data transmission to and from computer is done through serial port of the computer. The Chip is programmed through Parallel Port

11. Software Implementation First click on Send Words to set the chip frequencies. Then set the mode and train the receiver chip by learn sequence. Use the File transfer and Half-duplex chat. Third Part software may also be used e.g. HyperTerminal.

12. Programming Details For programming the serial port following Windows API’s were used: CreateFile ReadFile WriteFile GetCommState SetCommState