Shuttle orbiter Ku-band radar/communications system design evaluation. Deliverable test equipment evaluation

The Ku-band test equipment, known as the Deliverable System Test equipment (DSTE), is reviewed and evaluated. The DSTE is semiautomated and computer programs were generated for 14 communication mode tests and 17 radar mode tests. The 31 test modules provide a good cross section of tests with which to exercise the Ku-band system; however, it is very limited when being used to verify Ku-band system performance. More detailed test descriptions are needed, and a major area of concern is the DSTE sell-off procedure which is inadequate

Evaluation of coding scheme for MIMO radar

Multiple Input Multiple Output (MIMO) antenna systems have shown a great potential for wireless communication. These systems support high capacity, increased diversity and interference suppression. Recently it has been proposed MIMO constellations for Radar. MIMO Radar is not only a new research field, but also a very promising approach in terms of overcoming Radar Cross Section (RCS) fluctuations with diversity. This thesis explores the potential of coding schemes for MIMO Radar. The ambiguity functions measures related to MIMO Radar are used to evaluate how much diversity gain can be coherently achieved with certain coding schemes. The results of this analysis show that the cross correlation between the signals from different transmitters hinders achieving the full diversity gain. The code length of the used Gold codes is an important factor for this effect. However, in this thesis a coding scheme related to the Alamouti scheme in Communication is presented, this scheme under some constraints is capable of maintaining orthogonality between the signals from different transmitters and therefore cancels the mutual interference among those signals. In general, MIMO radar is a novel and ingenious approach to improve radar performance which needs to be analyzed and developed. This thesis is the first work exploring the coding schemes and the related aspects for MIMO Radar

Scattering from two-dimensional objects of varying shape combining the method of moments with the stochastic Galerkin method

In this communication, the combined field integral equation for perfect electrically conducting scatterers is combined with the stochastic Galerkin method (SGM) to model the impact of stochastic variations of the shape of the scatterer on the radar cross-section and on the induced current distribution. The SGM is compared to the stochastic collocation method (SCM) and it is shown that for a modest number of random variables the SGM is a good alternative to the SCM

Radar Cross Section of Chipless RFID tags and BER Performance

The performance of different chipless RFID tag topologies are analysed in terms of Radar Cross Section (RCS) and Bit Error Rate (BER). It is shown that the BER is mainly determined by the tag Radar Cross Section (RCS) once that a standard reading scenario is considered and a fixed size of the tag is chosen. It is shown that the arrangement of the resonators in the chipless tag plays a crucial role in determining the cross-polar RCS of the tag. The RCS of the tag is computed theoretically by using array theory where each resonator is treated as a separate scatterer completely characterized by a specific reflection coefficient. Several resonators arrangements (periodic and non-periodic) are compared, keeping the physical area of the tag fixed. Theoretical and experimental analysis demonstrate that the periodic configuration guarantees the maximum achievable RCS thus providing a global lower BER of the chipless RFID communication system. We believe that the BER is the more meaningful and fair figure of merit for comparing the performance of different tags than bt/cm2 or bt/Hz since the increase of encoded information of the tag is useful only if it can be correctly decoded

Space-Based Tethered Array Radar (STAR) - A Distributed Small Satellite Network

The Space-Based Tethered Array Radar (STAR) concept evolved from the DoD need for an affordable, launchable, survivable, and expandable Space-Based Radar for wide-area surveillance of airborne targets and for ballistic missile defense applications. Because low-observable threats can undermine conventional large monolithic Space-Based Radar satellite designs by forcing power-aperture products (inversely proportional to target radar cross-section) so high that the resulting heavy and expensive satellite could not be built or launched, innovative solutions are needed. One such solution is the use of a tether concept which derives strength and stability by tension rather than stiffness and bulk. The tether concept avoids rigid structures by embracing the premise of a Distributed Sparse Array Radar (DSAR) which coherently nets small satellite subarrays which are not physically interconnected. The STAR concept is a network of distributed small satellite subarrays each of which is a tethered set of elements or a string . Each string is a vertical linear array orbiting independently and made up of dipole array elements each with its own transmit/receive module and power source. In order to operate as a Distributed Sparse Array Radar, the relative locations of individual small satellite subarrays must be known to small fractions of a wavelength. In this paper after a brief discussion of SBR architecture, selected methods for cohering the Sparse Array, and for signal distribution, and signal combination are presented. Finally, an example design of a space based DSAR using tethers is described along with a communication scenario

Cooperative Radar and Communications Signaling: The Estimation and Information Theory Odd Couple

We investigate cooperative radar and communications signaling. While each system typically considers the other system a source of interference, by considering the radar and communications operations to be a single joint system, the performance of both systems can, under certain conditions, be improved by the existence of the other. As an initial demonstration, we focus on the radar as relay scenario and present an approach denoted multiuser detection radar (MUDR). A novel joint estimation and information theoretic bound formulation is constructed for a receiver that observes communications and radar return in the same frequency allocation. The joint performance bound is presented in terms of the communication rate and the estimation rate of the system.Comment: 6 pages, 2 figures, to be presented at 2014 IEEE Radar Conferenc

Towards Dual-functional Radar-Communication Systems: Optimal Waveform Design

We focus on a dual-functional multi-input-multi-output (MIMO) radar-communication (RadCom) system, where a single transmitter communicates with downlink cellular users and detects radar targets simultaneously. Several design criteria are considered for minimizing the downlink multi-user interference. First, we consider both the omnidirectional and directional beampattern design problems, where the closed-form globally optimal solutions are obtained. Based on these waveforms, we further consider a weighted optimization to enable a flexible trade-off between radar and communications performance and introduce a low-complexity algorithm. The computational costs of the above three designs are shown to be similar to the conventional zero-forcing (ZF) precoding. Moreover, to address the more practical constant modulus waveform design problem, we propose a branch-and-bound algorithm that obtains a globally optimal solution and derive its worst-case complexity as a function of the maximum iteration number. Finally, we assess the effectiveness of the proposed waveform design approaches by numerical results.Comment: 13 pages, 10 figures. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Coexistence Analysis between Radar and Cellular System in LoS Channel

Sharing spectrum with incumbents such as radar systems is an attractive solution for cellular operators in order to meet the ever growing bandwidth requirements and ease the spectrum crunch problem. In order to realize efficient spectrum sharing, interference mitigation techniques are required. In this letter we address techniques to mitigate MIMO radar interference at MIMO cellular base stations (BSs). We specifically look at the amount of power received at BSs when radar uses null space projection (NSP)-based interference mitigation method. NSP reduces the amount of projected power at targets that are in-close vicinity to BSs. We study this issue and show that this can be avoided if radar employs a larger transmit array. In addition, we compute the coherence time of channel between radar and BSs and show that the coherence time of channel is much larger than the pulse repetition interval of radars. Therefore, NSP-based interference mitigation techniques which depends on accurate channel state information (CSI) can be effective as the problem of CSI being outdated does not occur for most practical scenarios.Comment: Corrected some typos and reference