Sharif Digital Repository

Applying the recently emerged technique, MIMO (Multiple Input Multiple Output) to PCL (Passive Coherent Location) is expected to improve performance of localization schemes. In this paper, we explore the application of MIMO technology to PCL schemes and see how it improves the spatial diversity of such systems. Specifically, we use the DVB-T stations as the illuminators of opportunity in the simulations, mainly because of their unique features which make them quite suitable for both MIMO and PCL application as will be demonstrated in this paper. In addition, we address the key problem of finding optimum locations for placement of receive antennas  

MIMO (Mulitple Input Multiple Output) localization has attracted much attention recently. In such schemes, using multiple antennas at transmitter and receiver sides provides spatial diversity. On the other hand, Passive Coherent Location (PCL) by using the illuminators of opportunity (such as FM, GSM, DVB transmitters) has shown a number of advantages. In this paper, we explore the possibility of achieving diversity gain by using multiple non-cooperative transmitters. In earlier works on MIMO localization, cooperative transmitters were assumed, so that orthogonality between transmitted waveforms could be granted. However, such orthogonality condition is not assumed in the case of PCL... 

Efficient combination of MIMO (multiple-input multiple-output) and PCL (passive coherent location) ideas is expected to improve performance of localization schemes. While, in general, adding the number of transmit and receive antennas provides spatial diversity, it is possible to obtain similar effects by using multiple transmitters that are already transmitting standard signals (such as digital TV (DTV) transmission) in the environment (also known as illuminators of opportunity). However, in the case of passive schemes, it is not always possible to ensure that signals of different transmitters are orthogonal to each other. In such cases in which nonorthogonal transmitter signals are to be... 

Passive localization using MIMO techniques has attracted much attention recently. In such schemes, using multiple antennas at transmitter and receiver sides provides spatial diversity without need for identifiable transmitters. On the other hand, one of the problems facing such approach arises when transmitters of a single frequency network (SFN) are used as non-cooperative transmitters and resolving the signals of multiple transmitters reflected from multiple targets is not trivial at receiver side. Therefore, in order to obtain the diversity gain of MIMO localization schemes, it is necessary to develop a technique to assign each echo arriving at the receiver to a given transmitter. In this... 

The present study aims to evaluate the important issue of elimination of direct path interference and clutter in ambiguity function and detection of passive radars with adaptive filters. The efficiency and performance of each of them were investigated. Finally, by simulation and their learning curve, the best algorithm was proposed for these radars  

One of non-cooperative illuminators recently considered for passive radar applications is the DVB-T (Digital Video Broadcasting - Terrestrial) station. The thumbtack ambiguity function of the DVB-T signal in addition to being stationary makes such signal a good candidate for such applications. However, certain ambiguities in its ambiguity function necessitates certain issues to be carefully considered when DVB-T signals are to be utilized. In this paper, after studying the origins of these ambiguities, we propose special processing schemes to resolve them  

One of the attractive opportunistic signals for passive radar applications is the DVB-T (Digital Video Broadcasting- Terrestrial) signal. The thumbtack ambiguity function of the DVB-T signal in addition to being stationary makes such signal a good candidate for such applications. In this paper we want to consider its feasibility for this application in more details. So we first examin this signal for the main parts of the the passive radar: Resolving ambiguities before evaluating CAF and direct path intereference rejection, and then consider its processing gain in detecting targets  

Ideally the processing gain in passive radar is PG=BT. Where B is the bandwidth and T is the integration time. So by increasing T the target detectability will also increase. But practically, when we deal with moving targets, increasing T will result in a problem: target migration from its range cell that in turn results in decreased processing gain. In this paper we have suggested a method, by which we can compensate target's migration, while keeping the computational load low  

One non-cooperative illuminator recently considered for passive radar applications is the DVB-T (Digital Video Broadcasting-Terrestrial) signal. The thumbtack ambiguity function of the DVB-T signal, in addition to being stationary over time, makes such a signal a good candidate for such applications. However, certain ambiguities in its ambiguity function necessitates certain issues to be carefully considered when the DVB-T signal is to be utilized in these scenarios. Methods have been already proposed to resolve them. In this paper, after studying the origins of these ambiguities, we propose special processing schemes to reduce the complexity of the parts associated with resolving these... 

The Ionic polymer-metal composites (IPMCs) form an important category of electroactive polymers which generate large deformation under a low driving voltage. In this paper an empirical model of IPMC is developed by measuring the step response of a 23 mmx3.6 mmx0.16 mm IPMC strip in a cantilever configuration. Moreover, a model-based precision position control of an IPMC base on the fuzzy logic is presented. Open-loop position responses of an IPMC are not repeatable, and hence closed-loop precision control is of critical importance to ensure proper functioning, repeatability and reliability. A CCD camera was used to observe the closed loop response of the IPMC strip in order to control this... 

It is a well known fact that using multiple antennas at transmit and receive sides improves the detection performance. However, in such multiple-input multiple-output (MIMO) configuration, proper positioning of transmitters and receivers is a big challenge that can have significant influence on the performance of the overall system. In addition, determining the power of each transmitter under a total power constraint is a problem that should be solved in order to enhance the performance and coverage of such a system. In this paper, we design the Neyman-Pearson detector under the Rayleigh scatter model and use it to introduce a criterion for the antenna placement at both transmit and receive... 

There has been much interest, recently, towards exploiting the Multiple-Input Multiple-Output (MIMO) technique in radar. It is shown that using multiple antennas at transmit and receive sides can improve the performance of the system. However, in order to analyze the system's performance, its ambiguity function, i.e. the ambiguity function of a MIMO radar, is needed to be defined. In this paper, beginning from the information theoretic definitions, we derive such function, specifically for a MIMO radar with widely separated antennas  

By combining the two ideas of MIMO (Multiple Input Multiple Output) and PCL (Passive Coherent Location) in radar, one can achieve the advantages of both recently developed techniques simultaneously. While using multiple antennas at the receive side provides a spatial diversity of the object to be detected, using multiple illuminators of opportunity, most importantly, makes the radar covert to the interceptors. One obstacle in such MIMO configuration is choosing the positions of the receive antennas. In this paper, after analyzing the Neyman-Pearson detector for the DVB-T based PCL, we introduce the probability of missed detection as a criterion to place the receive antenna. Here, we only... 

Efficient combination of multiple input multiple output (MIMO) and passive coherent location (PCL) ideas is expected to improve performance of localisation schemes. While using multiple antennas at transmit and receive sides provides spatial diversity, it is possible to obtain similar performance by using multiple transmitters, already transmitting standard signals (such as digital TV) in the environment (also known as illuminators of opportunity). However, in this case, it is not always possible to ensure that signals of different transmitters are orthogonal to each other. In such cases, resolving signals of multiple transmitters reflected from multiple objects is not a trivial problem. One... 

Using multiple antennas at the transmit and receive sides of a passive radar brings both the benefits of MIMO radar and passive radar. However one of the obstacles arisen in such configuration is the receive antennas placement in proper positions so that the radar performance is improved. Here we just consider the case of positioning one receiver among multiple illuminators of opportunity. Indeed it is a start for the solution of optimizing the geometry of the multiple receivers in a passive radar  

Passive localization using MIMO techniques has attracted much attention recently. In such schemes, using multiple antennas at transmitter and receiver sides provides spatial diversity without need for identifiable transmitters. On the other hand, one of the problems facing such approach arises when transmitters of a single frequency network (SFN) are used as non-cooperative transmitters and resolving the signals of multiple transmitters reflected from multiple targets is not trivial at receiver side. Therefore, in order to obtain the diversity gain of MIMO localization schemes, it is necessary to develop a technique to assign each echo arriving at the receiver to a given transmitter. In this... 

In this paper we present a feasibility study on using satellite signal for passive radar application. Our focus is on utilizing GEO (geostationary Earth orbit) satellite signal with suitable properties. The feasibility of using such satellite signal for passive radar application is evaluated. In particular, a space shuttle as the target of interest is considered. In addition to being covert, it will be shown that using such passive radar system, we can benefit the forward scatter enhancement, which enables us to detect such high-altitude target that is totally undetectable to conventional radar systems  

It has been shown that using multiple antennas in a radar system improves the performance considerably, since multiple target echoes are received from different aspect angles of the target. In this way, the target detection is improved. However, when using multiple antennas, some problems, such as designing the transmit signals, synchronization, etc. emerge that should be solved. One of such problems is the receiver placement. Receiver placement deals with choosing a proper position for the receive antenna in order to optimize the whole system's performance. In this paper, a receiver placement procedure based on improving the radar ambiguity function is proposed for the case of a multisite...