Digital Transmitter Implementation

PosterWinter 2011-2012

Barak Shaashua Barak StraussmanSupervisor: Idan Shmuel

Project GoalsImplementation of a transmitter with

Labview on FPGA.

Project modulation types: 4 DQAM 8 DPSK

Hardware Connection

250MS/s

1.5MB/s

2.1GS/s16MB memory

Tabor – wx2182 as DACNI FlexRio FPGA

7965R as TX

NI 5761 Digitizer + NI FlexRio

FPGA 7965R as RX

System ProblemsThe bottleneck of the system is the speed of the DAC (Tabor

wx2182) connection through the GPIB cable. Therefore, the system complexity was reduced by simulating The TX

on the HOST. (Even though the TX works on the FPGA).

Streaming is not supported by the DAC through the GPIB. Transmission is done in packets as big as the memory of the DAC.

The DAC doesn’t transmit both channels synchronically (without trigger). As a result, the two channels are combined on the HOST and

delivered to the DAC as one channel.

Data RatesTransmitter boundary: DAC max sample rate:

2.1GS/sec. In this rate carrier wave frequency: 1.05GHz.

Receiver boundary: The ADC (NI5761) - max sample rate: 250MS/sec --> BW = 125MHz.

Data boundary: Limited by the DAC memory size - 16M samples.

I

Q

 Serial /

Parallel 

Constellation Mapping

DAC

ISIFilte

r

Up Convert

er

Channel Coder

Source Coder

CombinerSin(wt)

+π/2

I

Q

Transmitter Block Diagram

DAC

Symbol Decision

Constellation

Mapping

Channel Decoder

RF

Parallel /

Serial

Receiver Block-Diagram

ADCSin(wt)

+π/2I

Q

I

Q +(

Source)

Timing &

Carrier Recover

yLPF

LPF

Implementation example - Transmitter Symbol Mapping

***

Implementation example - Acquisition FPGA

Transmission ParametersWe worked with Carrier frequency: 50MHz + 10

samples per period --> DAC operates in 500MS/sec.

Symbol = 1 period of the carrier.Data rate: DQPSK - 2 bit/symbol - 100Mbit/sec.

D8PSK - 3 bit/symbol - 150Mbit/sec.With 16M DAC memory - Data transition per

transmission: 400KB (DQPSK) / 600KB (D8PSK).

Results25MHz transmission --> BER=0(One symbol error at the edge, not dependent on transmission length)

50MHz transmission --> BER=0

80MHz transmission --> BER=1/3No alignment between samples and carried

periods.Over sampling too low.

SummeryIn this project we acquired a lot of knowledge about

communication and modulation.

The project involved the integration of variety of systems and work environments.

Future improvements:

Labview - We found it hard to debug FPGA VI.

Tabor - In our project setting, wx2182 wasn’t suitable.