Feasibility and systems definition study for Microwave Multi-Application Payload (MMAP)

Work completed on three Shuttle/Spacelab experiments is examined: the Adaptive Multibeam Phased Array Antenna (AMPA) Experiment, Electromagnetic Environment Experiment (EEE) and Millimeter Wave Communications Experiment (MWCE). Results included the definition of operating modes, sequence of operation, radii of operation about several ground stations, signal format, foot prints of typical orbits and preliminary definition of ground and user terminals. Conceptual hardware designs, Spacelab interfaces, data handling methods, experiment testing and verification studies were included. The MWCE-MOD I was defined conceptually for a steerable high gain antenna

Dual-mode linear phased array antennas for monopulse radars

Phased array antennas are widely used around the world. Much research is focused on extending capabilities of modern wireless systems and radars. Dual-mode elements are researched for use in beamforming, monopulse radar and multi-frequency applications. Beamforming in itself is an extensively researched topic, aimed at canceling interference and/or finding signal angle-of-arrivals. The goals of this thesis are two-fold. Firstly, to take the monopulse capabilities of a dual-mode antenna element to allow for a linear phased array antenna to generate the sum, delta-azimuth, and delta-elevation channels whereas normal linear phased array antennas can only generate a single difference channel. Secondly, to exploit the signal separating abilities of eigen-space methods to improve the performance of monopulse in a scenario where there is a closely correlated target corrupting the data. Future work should investigate array designs using multi-mode elements and further studies of any extra capabilities such an element brings to adaptive processing

Track-Initiated Beam Spoiling for Improved Tracking with Digital Phased-Array Radars

Radar systems have become highly dynamic with the advancements in all-digital radar architectures. All-digital radar architectures introduce the potential for dynamic beamforming. This thesis will detail the fundamentals that are the foundation of radar signal processing (RSP) and modeling a digital phased array radar. This thesis will detail the techniques used for digital beamspoiling. The intentional beamspoiling is intended to improve the trackers’ ability to track a target continuously. When a high-speed target falls out of a beam due to a maneuver, the radar will spoil the transmit beam illuminating a wider scene. The wider illuminated scene allows for a higher likelihood of accurately detecting the target, allowing the tracker to track the target continuously. This thesis will discuss the theory and application of the trackers used in the simulation. With the beamspoiling and trackers, this thesis will analyze the ability of an all-digital phased array to track a target utilizing dynamic beamforming to improve the tracking performance. Finally, it will detail the improvement of the trackers’ ability to track when utilizing beamspoiling for specific situations, allowing the radar to track targets for a more extended time. The results varied based on the amount a transmit beam was spoiled due to the loss in SNR that naturally occurs from the decrease in power density

3D conformal antennas for radar applications

Embedded below the radome of a missile, existing RF-seekers use a mechanical rotating antenna to steer the radiating beam in the direction of a target. Latest research is looking at replacing the mechanical antenna components of the RF seeker with a novel 3D conformal antenna array that can steer the beam electronically. 3D antennas may oer signicant advantages, such as faster beamsteering and better coverage but, at the same time, introduce new challenges resulting from a much more complex radiation pattern than that of 2D antennas. Thanks to the mechanical system removal, the new RF-seeker has a wider available space for the design of a new 3D conformal antenna. To take best benets of this space, dierent array shapes are studied, hence the impact of the position, orientation and conformation of the elements is assessed on the antenna performance in terms of directivity, ellipticity and polarisation. To facilitate this study of 3D conformal arrays, a Matlab program has been developed to compute the polarisation pattern of a given array in all directions. One of the task of the RF-seeker consists in estimating the position of a given target to correct the missile trajectory accordingly. Thus, the impact of the array shape on the error between the measured direction of arrival of the target echo and its true value is addressed. The Cramer-Rao lower bound is used to evaluate the theoretical minimum error. The model assumes that each element receives independently and allows therefore to analyse the potential of active 3D conformal arrays. Finally, the phase monopulse estimator is studied for 3D conformal arrays whose quadrants do not have the same characteristics. A new estimator more adapted to non-identical quadrants is also proposed

Advanced deep space communication systems study Final report

Deep space communication system requirements for period 1970 to 198

Clutter Mitigation using Auxiliary Elements for the NWRT Phased Array Radar

Abstract-The National Weather Radar Testbed (NWRT) has a 10-cm phased array radar that is used primarily for monitoring the weather. It is attractive compared to the current parabolic dish Weather Surveillance Radar-88 Doppler (WSR-88D) because of its capability to electronically steer. When combined with the recently developed beam multiplexing technique that uses a small number of contiguous samples and clever spatial sampling, this radar can obtain very rapid update scans and is extremely advantageous in monitoring severe weather. However, the small number of contiguous samples makes filtering of the clutter signal problematic in the temporal/spectral domain and can limit the performance of this radar in clutter dominated conditions. By exploiting the spatial correlation of the auxiliary channel signals, the effect of clutter contamination can be reduced to overcome this problem. In this work, two spatial filtering techniques that use low-gain auxiliary receive channels are presented, and the effect of clutter mitigation is investigated using numerical simulations for a tornadic thunderstorm dominated by clutter return. Parameters under investigation include signal-to-noise ratio, clutter-to-signal ratio, number of time series samples, varying clutter spectral widths, and maximum weight constraints

Tracking and control in multi-function radar

The phased array multi-function radar is an effective solution to the requirement for simultaneous surveillance and multiple target tracking. However, since it is performing the jobs usually undertaken by several dedicated radars its radar time and energy resources are limited. For this reason, and also due to the large cost of active phased array antennas, it is important for the strategies adopted in the control of the radar to be efficient. This thesis investigates and develops efficient strategies for multi-function radar control and tracking. Particularly the research has focused on the use of rotating array antennas and simultaneous multiple receive beam processing. The findings of the research challenge the traditional view that three or four fixed (static) array faces is the best antenna configuration for a multi-function radar system. By developing novel methods for the comparison of systems utilising different antenna configurations it is shown that a rotating array multi-function radar performs the surveillance function with a greater efficiency in its use of radar time than a static array system. Also, a rotating array system benefits from the ability to distribute the radar resources over the angular coverage in a way that is impossible with a static array system. A novel strategy is presented to achieve this, which allows the rotating array system to better support the realistic situation of a high concentration of radar tasks in a narrow angular sector. It is shown that the use of broadened transmit beams coupled with simultaneous multiple narrow receive beams can eliminate the compromise on radar beamwidth between the surveillance and tracking functions that is associated with multi-function radars. This technique would allow construction of multi-function radar systems with narrow beamwidths, giving improved tracking performance, without extending search frame times excessively. Efficient tracking strategies for both static array and rotating array multi-function radars are developed. They are applied through computer simulation to demonstrate tracking of highly manoeuvrable targets with a narrow beam multi-function radar. Track robustness is attained through the use of multiple beam track updating strategies at little cost in terms of radar time

3-D Beamspace ML Based Bearing Estimator Incorporating Frequency Diversity and Interference Cancellation

The problem of low-angle radar tracking utilizing an array of antennas is considered. In the low-angle environment, echoes return from a low flying target via a specular path as well as a direct path. The problem is compounded by the fact that the two signals arrive within a beamwidth of each other and are usually fully correlated, or coherent. In addition, the SNR at each antenna element is typically low and only a small number of data samples, or snapshots, is available for processing due to the rapid movement of the target. Theoretical studies indicates that the Maximum Likelihood (ML) method is the only reliable estimation procedure in this type of scenario. However, the classical ML estimator involves a multi-dimensional search over a multi-modal surface and is consequently computationally burdensome. In order to facilitate real time processing, we here propose the idea of beamspace domain processing in which the element space snapshot vectors are first operated on by a reduced Butler matrix composed of three orthogonal beamforming weight vectors facilitating a simple, closed-form Beamspace Domain ML (BDML) estimator for the direct and specular path angles. The computational simplicity of the method arises from the fact that the respective beams associated with the three columns of the reduced Butler matrix have all but three nulls in common. The performance of the BDML estimator is enhanced by incorporating the estimation of the complex reflection coefficient and the bisector angle, respectively, for the symmetric and nonsymmetric multipath cases. To minimize the probability of track breaking, the use of frequency diversity is incorporated. The concept of coherent signal subspace processing is invoked as a means for retaining the computational simplicity of single frequency operation. With proper selection of the auxiliary frequencies, it is shown that perfect focusing may be achieved without iterating. In order to combat the effects of strong interfering sources, a novel scheme is presented for adaptively forming the three beams which retains the feature of common nulls

Shuttle orbiter Ku-band radar/communications system design evaluation

Tasks performed in an examination and critique of a Ku-band radar communications system for the shuttle orbiter are reported. Topics cover: (1) Ku-band high gain antenna/widebeam horn design evaluation; (2) evaluation of the Ku-band SPA and EA-1 LRU software; (3) system test evaluation; (4) critical design review and development test evaluation; (5) Ku-band bent pipe channel performance evaluation; (6) Ku-band LRU interchangeability analysis; and (7) deliverable test equipment evaluation. Where discrepancies were found, modifications and improvements to the Ku-band system and the associated test procedures are suggested