Search

The scientific community has expressed interest in the potential of phased array radars (PARs) to observe the atmosphere with finer spatial and temporal scales. Although convergence has occurred between the meteorological and engineering communities, the need exists to increase access of PAR to meteorologists. Here, we facilitate these interdisciplinary efforts in the field of ground-based PARs for atmospheric studies. We cover high-level technical concepts and terminology for PARs as applied to studies of the atmosphere. A historical perspective is provided as context along with an overview of PAR system architectures, technical challenges, and opportunities. Envisioned scan strategies are summarized because they are distinct from traditional mechanically scanned radars and are the most advantageous for high-resolution studies of the atmosphere. Open access to PAR data is emphasized as a mechanism to educate the future generation of atmospheric scientists. Finally, a vision for the future of operational networks, research facilities, and expansion into complementary radar wavelengths is provided. [ABSTRACT FROM AUTHOR]

Practical and accurate estimation of 3-D wind fields is an ongoing challenge in radar meteorology. Multistatic (single transmitter/multiple receivers) radar architectures offer a cost-effective solution for obtaining the multiple Doppler measurements necessary to achieve such estimates. Existing multistatic weather radars, while less costly than comparable monostatic networks, have been constrained by the need for specialized equipment and software to perform frequency and pulse timing synchronization with the transmitting radar. This article describes the implementation of a passive radar network that performs pulse timing and carrier frequency synchronization through measurements of the sidelobe radiation of the transmitting radar. This makes it possible for the receiver modules to be constructed with minimal size and cost, and it allows for their use in coordination with any in-band transmitter capable of recording time-stamped pointing angle information. A prototype network consisting of two passive receivers has been constructed in the Oklahoma City, OK, USA. Weather observations collected using the radiation from a WSR-88D have been used to validate the accuracy of velocity measurements obtained through this technique. [ABSTRACT FROM AUTHOR]

With an incredible increase in the number of wireless devices and an ever-growing demand for high data rates, 5G needs to provide a solution to satisfy the demand for the next decade. Multiple-input multiple-output (MIMO) systems are seen as one of the primary solutions—allowing for spatial multiplexing and the use of millimeter-wave (mmWave) frequencies, which can provide much larger bandwidths and, thus, data rates. MIMO is very closely related to phased arrays, which have been used for radar for the past few decades and requires many antennas and transceivers—on the order of hundreds or thousands for massive MIMO. To make such systems affordable, low-cost, low-power, and low-complexity is required—inherently compromising other system characteristics, such as linearity. The main focus of this paper will be in summarizing the challenges, recent advances, and potential future breakthroughs concerning MIMO/digital array sensitivity to interferers and nonlinear distortion. Specifically, this paper gives an overview of MIMO/digital array architectures and different techniques currently researched for the characterization and mitigation of spatial and spectral interferers and nonlinearities, which can be used to extend the effective dynamic range of low-cost MIMO/digital array systems. [ABSTRACT FROM AUTHOR]

This contribution presents the results of a dual-polarized radiating element designed to achieve low cross-polarization (lower than −40 dB measured for the E-and H-plane, at least −30 dB in the D-plane based on simulations) and large fractional bandwidth (18%) over wide scanning angles (±60°). The proposed design includes multiple features that enable high isolation between ports, reduction of spurious radiation, highly symmetrical radiated fields, and suppression of diffracted fields between contiguous subarray gaps. To verify the polarimetric requirements for a weather radar, simulated and measured results, including electronic scanning of the array and embedded element patterns of the antenna, are shown. [ABSTRACT FROM AUTHOR]

Spectral regrowth and waveform distortion caused by wideband signals input into active phased array antenna systems is the problem this paper addresses. The paper's unique contribution is the development of the impedance-dependent memory polynomial model, capable of solving nonlinear predistortion model parameters for a solid-state high power amplifier with varying load impedance resulting from active electronic beamsteering. Wideband load impedance mismatched tests demonstrate the effectiveness of this technique on a 2.7 GHz, 8 W amplifier. [ABSTRACT FROM PUBLISHER]

This paper addresses spectral regrowth caused by wideband signals input into solid-state amplifiers. Unique contributions are a weighted least-squares method for solving predistorter nonlinear model parameters, and a Bayesian method for tracking model parameters in slowly changing systems. Next-generation active phased array radars are the primary application. Past predistortion research has been primarily aimed at narrowband communications, while radar wideband applications have been relatively unexplored. Laboratory measurements confirm our methods. [ABSTRACT FROM AUTHOR]

The mitigation of third-order intermodulation distortion produced by a nonlinear tunable bandpass filter (BPF) in a digital receiver channel is demonstrated. An iterative solution is proposed, in the use of the least-mean-square algorithm, as an effective way to allow the correction coefficients to adapt to the changes in the system characteristics when the center frequency is changed. Results are shown using a two-pole, varactor-loaded BPF, and an Analog Devices AD9371 transceiver. [ABSTRACT FROM AUTHOR]

Digital beamforming (DBF) has long been heralded as the next frontier in phased array technology, and not without reason. The digitization of transmit and receive signals at the element level opens the door to new processing and beamforming schemes and promises to deliver maximum flexibility and unprecedented dynamic range in large systems. However, it is not without inherent technological risks and practical challenges associated with the amount of data to process and the use of less sophisticated transceivers. This paper provides broad overviews of several interrelated aspects of the resulting DBF trade spaces for these systems. In particular, emerging concepts are highlighted for the roles and interconnection of distributed beamforming/processing for fixed and adaptive beamforming. These are then related to digital array calibration mechanisms that can potentially reduce the need for data- and processing-intensive beamforming algorithms. [ABSTRACT FROM PUBLISHER]

As active electronically steerable arrays become more prominent, a new paradigm of assigning bits to a set of digital phase shifters, necessary for analog and digital beamforming, is proposed. It is well known that a modern day digital phase shifter which is associated with each transmit/receive module typically relies on three to seven bits. Each of these phase shifters provide a desired resolution of 45^\circ to 2.8125^\circ, respectively. When an array is steered with a fixed precision set of phase shifters, there are some angles where results are significantly better than others. For example, six bit phase shifters can provide exact 11.25^\circdifferential phases in a linear array, but not 15^\circ, and subsequent quantization errors lead to reduced pointing accuracy and increased sidelobe levels. However, these errors can be minimized if the set of shifters operate collectively instead of independently with “blind” quantization. In particular this study seeks the solution for the following problem: for a set of N phase shifters, each defined by B bits, determine the optimal way to distribute the N\times B bits so that the array performance is maximized. [ABSTRACT FROM PUBLISHER]