Robust DTV receiver for vehicles

Source – Village Island Co, Ltd.

We have built an RF capture and playback device based on DekTec technology, with a diversity antenna, the RF capture board DTA-2131 and RF modulation board DTA-2111, all housed in a small PC enclosure. This diversity receiver has been used with two or four antennas simulating a digital terrestrial receiver system for vehicles. It proved very stable even at high speed if the RF signal can be received properly from at least one antenna.

DTA-2131 – Click for specifications sheet

The RF signal was captured precisely by the DTA-2131, as shown in the diagram below, thanks to the use of two parallel inputs, 256Mbps with 20usec delay time difference (RF bandwidth 7MHz at 8Msps). It was then recorded in a large-capacity, high-speed SSD of 256GB as IQ signals. When IQ recordings were played back as an RF signal, the modulation board DTA-2111 would read the IQ files from the SSD and perform the same parallel operation with the same 20usec delay time. This enables full simultaneous recording and playback because the delay time difference is offset when recording + reproducing signals from the two antennas.

Further to that, in a system with 2 PCs having each 2 RF captures and modulation boards, we synchronised two PCs with UDP commands on Ethernet in order to receive the signal from four antennas in a synchronised way.

In the case of realizing the capture device in one PC, in another example, we used a single PC with a capacity of 6 PCIe boards and with a motherboard having a Thunderbolt port. The Thunderbolt port was used with a Thunderbolt extension case able to house the last 2 PCIe board. Even using such extension case, the system was able operate the 4 parallel recording and playback operations with only 20usec delay time difference.

DekTec has already released its top-of-the-range modulator DTA-2115 capable to receive GPS 1pps / 10MHz input for SFN correspondence. This will make possible to record at +/- 30nsec time alignment and dramatically increase the accuracy. Therefore, according to your application it is possible to build a more accurate capture device.

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