Communication Subsystems for Emerging Wireless Technologies

The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels

Neural Networks for improved signal source enumeration and localization with unsteered antenna arrays

Direction of Arrival estimation using unsteered antenna arrays, unlike mechanically scanned or phased arrays, requires complex algorithms which perform poorly with small aperture arrays or without a large number of observations, or snapshots. In general, these algorithms compute a sample covriance matrix to obtain the direction of arrival and some require a prior estimate of the number of signal sources. Herein, artificial neural network architectures are proposed which demonstrate improved estimation of the number of signal sources, the true signal covariance matrix, and the direction of arrival. The proposed number of source estimation network demonstrates robust performance in the case of coherent signals where conventional methods fail. For covariance matrix estimation, four different network architectures are assessed and the best performing architecture achieves a 20 times improvement in performance over the sample covariance matrix. Additionally, this network can achieve comparable performance to the sample covariance matrix with 1/8-th the amount of snapshots. For direction of arrival estimation, preliminary results are provided comparing six architectures which all demonstrate high levels of accuracy and demonstrate the benefits of progressively training artificial neural networks by training on a sequence of sub- problems and extending to the network to encapsulate the entire process

Synthetic aperture radar/LANDSAT MSS image registration

Algorithms and procedures necessary to merge aircraft synthetic aperture radar (SAR) and LANDSAT multispectral scanner (MSS) imagery were determined. The design of a SAR/LANDSAT data merging system was developed. Aircraft SAR images were registered to the corresponding LANDSAT MSS scenes and were the subject of experimental investigations. Results indicate that the registration of SAR imagery with LANDSAT MSS imagery is feasible from a technical viewpoint, and useful from an information-content viewpoint

Rationale for and design of a generic tiled hierarchical phased array beamforming architecture

The purpose of the phased array beamforming project is to develop a generic flexible efficient phased array receiver platform, using a mixed signal hardware/software-codesign approach. The results will be applicable to any radio (RF) system, but we will focus on satellite receiver (DVB-S) and radar applications. We will present a preliminary mapping of beamforming processing on a tiled architecture and determine its scalability.\ud \ud The functionality, size and cost constraints imply an integrated mixed signal CMOS solution. For a generic flexible multi-standard solution, a software defined radio approach is taken. Because a scalable and dependable solution is needed, a tiled hierarchical architecture is proposed with reconfigurable hardware to regain flexibility. A mapping is provided of beamforming on the proposed architecture. The advantages and disadvantages of each solution are discussed with respect to applicability and scalability.\ud \ud Different beamforming processing solutions can be mapped on the same proposed tiled hierarchical architecture. This provides a flexible, scalable and reconfigurable solution for a wide application domain. Beamforming is a data-driven streaming process which lends itself well for a regular scalable architecture. Beamsteering on the other hand is much more control-oriented and future work will focus on how to support beamsteering on the proposed architecture as well

Massive MIMO is a Reality -- What is Next? Five Promising Research Directions for Antenna Arrays

Massive MIMO (multiple-input multiple-output) is no longer a "wild" or "promising" concept for future cellular networks - in 2018 it became a reality. Base stations (BSs) with 64 fully digital transceiver chains were commercially deployed in several countries, the key ingredients of Massive MIMO have made it into the 5G standard, the signal processing methods required to achieve unprecedented spectral efficiency have been developed, and the limitation due to pilot contamination has been resolved. Even the development of fully digital Massive MIMO arrays for mmWave frequencies - once viewed prohibitively complicated and costly - is well underway. In a few years, Massive MIMO with fully digital transceivers will be a mainstream feature at both sub-6 GHz and mmWave frequencies. In this paper, we explain how the first chapter of the Massive MIMO research saga has come to an end, while the story has just begun. The coming wide-scale deployment of BSs with massive antenna arrays opens the door to a brand new world where spatial processing capabilities are omnipresent. In addition to mobile broadband services, the antennas can be used for other communication applications, such as low-power machine-type or ultra-reliable communications, as well as non-communication applications such as radar, sensing and positioning. We outline five new Massive MIMO related research directions: Extremely large aperture arrays, Holographic Massive MIMO, Six-dimensional positioning, Large-scale MIMO radar, and Intelligent Massive MIMO.Comment: 20 pages, 9 figures, submitted to Digital Signal Processin

3-D GPR survey with a modular system: reducing positioning inaccuracies and linear noise

Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna elements in a fixed configuration has become more common. The investment needed for these systems is significant. Although gradually expandable modular systems, consisting of antennas which can be used independently, do not match the fast acquisition of detailed datasets by means of multi-channel arrays, they can help finding a compromise between increased acquisition speed and (limited) resources. In modular systems, the separation between transmitter-receiver pairs is often larger than the sampling distance prescribed by the Nyquist theorem. As a consequence, additional profiles have to be recorded in between, which requires a high positioning precision. As a completely identical response for the different antennas in an array is difficult to achieve, stripes can occur in the horizontal slices, especially when ringing occurs. This complicates the interpretation of features in the direction of the survey lines. In this paper, a three-dimensional frequency-wavenumber filter is proposed, consisting in a combination of a circular filter and a fan filter. The application of this filter to GPR data collected at the Roman town Mariana (Corsica, France) showed a reduction of the stripe patterns, allowing a more reliable characterization of subtle archaeological structures

Publications of the Jet Propulsion Laboratory 1987

A bibliography is presented which describes and indexes by author the externally distributed technical reporting, released during the calender year 1987, that resulted from scientific and engineering work performed, or managed, by the Jet Propulsion Lab. Three classes of publications are included: (1) JPL publications in which the information is complete for a specific accomplishment; (2) Articles from the quarterly Telecommunications and Data Acquisition Progress Report; and (3) Articles published in the open literature