Double-through equalization technique an efficient strategy for processing of teletext signals

Abstract

In urban areas teletext signals are easily corrupted by multipath propagation which is produced as a result of reflection of the signal on the surrounding buildings. In this paper, an efficient strategy for processing of teletext signals under multipath propagation is presented. A distinct feature of the teletext transmission which makes it different from the conventional data transmission systems is that the data is transmitted in the form of packet during each Vertical Blanking Interval (VBI) of the TV signal. This means that there is an ample time during each TV frame for processing the teletext signal that has been received in the last VBI. Noting this, we propose a semi- off-line processing scheme, called double-through equalization, as an efficient mean of processing the teletext signals. Practical results are presented which shows that using the double-through equalization scheme the bit error rate can be reduced by 20-30 dB compared to the case where no equalizer is used.