Letter
Method of Calculating Desynchronization of DVB-T
Transmitters Working in SFN for PCL Applications
Karol Klincewicz * and Piotr Samczy ´nski
Institute of Electronic Systems, Warsaw University of Technology, 00-665 Warsaw, Poland;
psamczyn@elka.pw.edu.pl
* Correspondence: k.klincewicz@elka.pw.edu.pl
Received: 8 September 2020; Accepted: 7 October 2020; Published: 12 October 2020
Abstract:
This paper presents a novel method of calculating desynchronization between transmitters
working in a single frequency digital video broadcasting-terrestrial (DVB-T) network. The described
method can be a useful tool for enhancing passive radar operations and improving passive coherent
location (PCL) sensors to correct their measurements of target localization. The paper presents the
problem of localizing DVB-T transmitters utilized by passive radars, and proposes a novel method
based on Time Difference of Arrival (TDoA) techniques to solve the problem. The proposed technique
has been validated using real signals collected by a PCL sensor receiver. The details of the experiment
and extensive result analysis are also contained in this article.
Keywords: passive radar; TDoA; SFN; DVB-T
1. Introduction
The idea of using non-cooperative transmitters as an illuminator of opportunity (IO) for a passive
radar receiver is not a new one. The history of passive radar goes back to the 1930s, when Robert
Watson-Watt made the first demonstration of this technology utilizing a BBC radio transmitter as an
illuminator of opportunity [
1
]. The technology was further developed during World War II, when the
Germans built a passive radar named Klein Heidelberg which used Chain Home British radars as
illuminators of opportunity [
1
]. After the Second World War, passive radar had no major research
interest until the 1990s due to the limited computing power available.
Nowadays, after nearly three decades, passive radar technology is in a stage of maturity. It provides
many applications, from air surveillance [
2
–
4
] to target imaging [
5
,
6
], where different kinds of IOs are
used, from commercial transmitters (e.g., FM radio, DAB, DVB-T, GSM, among others) [
7
] to utilize
other radars as IOs [
8
]. Recently, DVB-T transmitters of opportunity became one of the most frequently
used as IOs for passive coherent localization (PCL) systems [
7
,
9
–
11
], as they are characterized by
relatively wide bandwidth (8 MHz) and relatively high power transmitters, which allows for medium
range operation up to 100km with a bistatic range resolution of ca. 36 m [
7
]. DVB-T can operate
in multi-frequency network (MFN) or single frequency network (SFN) configurations. One of the
problems of an SFN in passive radars is ghost targets. This phenomenon is a result of the number of
signal copies acquired by a single receiver.
There are several scientific works in the literature that focus on problems of passive localization
systems utilizing SFNs [
9
,
12
,
13
]. A common assumption in most of these works is that SFN transmitters
are time-synchronized. In reality, this condition is almost never fulfilled. Most commercial SFN
transmitters experience a time shift between each other by design [
14
]. This fact seems unexplored by
passive radar studies, therefore no attempts to cope with it were made. This is unfortunate because
SFN desynchronization may introduce major errors in passive radar target localization. The authors of
this article recognize a gap in passive radar signal processing studies, and propose a novel method of
Sensors 2020, 20, 5776; doi:10.3390/s20205776 www.mdpi.com/journal/sensors
