Overlapped subarray is an attractive structure to achieve low-cost multiple receive beams. However, satisfactory weights of overlapped subarray is hard to design, especially considering the transmit beam pattern. In this paper, a method to optimize the receive excitation of overlapped subarrays on the basis of a given transmit pattern is proposed. The relationship between the two-level weights and the two kinds of sidelobes is analyzed at first. Then, a squential convex programming strategy is adapted to optimize the element-level and subarray-level weights jointly to match the pre-defined transmit beam pattern. The required multi-beam coverage region and minimal sidelobe level could be obtained after these steps. Numerical experiments are presented to verify the effectiveness of this method.
This paper proposes a converged-aperture architecture to enable dynamic reconfiguration of spectral access between platform mission functions. Based on phased-array apertures, intra-platform data throughputs required to support the envisioned architecture are discussed, and integrated photonic transceivers are put forward as a critical enabling technology.
The space industry has shifted its focus to the development of low-cost satellites and large satellite constellations. Notably, most nano-satellites in low Earth orbit operate at UHF (P-band) frequencies to leverage the use of low-cost commercial off-the-shelf electronics. Such constellations would benefit from the rapid steering of multiple beams offered by a phased array antenna (PAA) ground station (GS). The cost of such systems, however, is not conducive to the low-cost philosophy of the satellites. While several universities have identified the need for a low-cost UHF PAA GS, no feasible design or prototype has yet been developed that is suitable for low-cost applications involving PAAs with a large number of elements. This paper proposes and demonstrates a subarray-digital architecture with a novel two-stage analog beamforming segment to optimize resource usage within the PAA, by allowing for the dynamic reconfiguration of the number of required digital ports. It further leverages several cost reduction techniques to design a modular and scalable transmit/receive module and ancillary geodesic dome PAA. An operational prototype is constructed and used to validate and characterize the implemented design. This successfully reduces the costs of a PAA GS while retaining the associated performance benefits.
This paper presents the recent activities carried out at ONERA in the field of antenna arrays using PCB technologies. These activities cover principally wideband applications with strong integration constraints, which require very low profile antennas. Two examples of antenna array developed at ONERA are presented in the paper.
This paper examines how cross-polarization can be effectively reduced in two-dimensional array apertures of linearly-polarized Vivaldi antennas. In previous work it was demonstrated how metallic cross walls, positioned orthogonal to the linear Vivaldi antenna elements in a two-dimensional array, reduce cross-polarization significantly - e.g., -15dB levels for 45° diagonal plane scans. This cross-polarization mitigation technique is expanded upon by showing that slices in the metallic cross walls can further reduce cross-polarization, e.g. -25dB levels for 45° diagonal plane scans. For demonstration, an 8×8 single-pol. Vivaldi array comprising 8 rows of 8-element sub-arrays arranged onto a uniform grid with slots between elements is presented. Cross-polarization measurements are compared to infinite array simulations with and without ‘sliced’ metallic cards inserted (orthogonally) into the slots between radiating elements.
This paper presents a novel hybrid-fed, low profile, dual polarized antenna element for phased array applications. Proposed antenna element supports a wide scan range of ±45°, ±60° and ±75° on its E-, H- and D-planes, respectively, over a wide frequency band of 8.8-11.5 GHz with an active VSWR below 2.5:1 for each polarization channel. The antenna features a low complexity, comprising four RO3003 layers and a set of vias which serves to mitigate higher order mode propagation for the feeds. Utilized hybrid feeding method helps to increase the isolation between the ports, which is higher than 13 dB at broadside. Dual feed lines of the first port and an internal matching network at the second port improve the impedance bandwidth at 50 Ω coaxial connector interfaces of the antenna. Low profile of the developed antenna element enables conformal phased array applications.
A planar dual-polarized ultra-wideband array that covers both K and V bands is presented. The architecture relies on tightly coupled dipoles arranged in an egg-crate configuration and a novel capacitive via arrangement that pushes both, the common mode resonance and, the detrimental loop mode resonance, out of the band. To improve the impedance bandwidth and scanning ability, a Marchand balun feed network and a dielectric-based superstrate are respectively used. Infinite array simulations of our array demonstrate a bandwidth of 2.5:1 (24GHz to 60GHz) with VSWR<3 for a maximum scan-angle of ± 45° for both E-and H-planes.
Frequency-modulated continuous wave (FMCW) radar has seen a significant increase in use due to its ability to operate in low-power and mobile environments suited for low peak power solid state transmitters. Though there are many current applications for the FMCW technique, the majority are focused on measuring “hard” targets (e.g., cars, humans, etc.) and it is not heavily used in the measurement of volume targets such as precipitation. Moreover, current FMCW radars used for volumetric measurements are generally focused on very specific use cases such as vertical profiling. This work presents DARMA, a low-power, dual-polarized, FMCW radar with a phased array antenna capable of being deployed on unmanned aircraft systems (UAS). It will be used to test the feasibility of measuring and classifying complex weather events on a mobile platform which will provide different perspectives at the lowest kilometer of precipitation volumes.
This paper presents a 256-element Ku-band dual- polarized transmit phased-array with wide operation frequency range. The array is based on 64 commercial beamformer chips in SiGe technology with 2x2 configuration. T he c hip h as 6-bit of phase control and 25 dB gain tuning range. The 256-element phased-array operates at 13.75-17.2 GHz and has a measured EIRP of 40 dBW at Psat in circular polarized (CP) mode. The phased-array scans to +/-60° in both azimuth and elevation planes with low sidelobes, and it achieves <-25 dB cross polarization levels at all scan angles after calibration. The array also achieves a radiated coherent EIRP noise of -101.4 dBm/Hz, which together with 70 dBm of radiated EIRP, result in 111 dB of dynamic range per MHz of bandwidth. The 256-element array can also be configured a s d ual-beam m ode i n w hich e ach 128-element sub-array can be operated independently. To our knowledge, this presents the first s tate-of-art wide b andwidth K u-band transmit phased-array with applications areas in Ku-band communication and radar systems.
A 4x2 dual beam, wideband, dual linear polarized phased array antenna, consisting of innovatively shaped all metallic radiators with an overall cross-section of λ/2 × λ/2 and height nearly equal to λ/2 corresponding to the center frequency (9.50 GHz), working also as heat sink is presented for X-band (8.5-11.5 GHz) applications. The peak broadside gain is varying between 14–11 dBi over the bandwidth. Peak gain varies from 12.8-12.5 dBi at 9.50 GHz as beam scans till ±45° in φ=00plane and ±30° in φ=90° plane. The 4x2 antenna aperture is 3D metal printed, and the beamforming network, comprised of Anokiwave RFICs, is integrated with the antenna aperture. The temperature reduction of 60°C is obtained using this heat sink antenna structure, which is validated with an infrared (IR) camera. The Anokiwave RFIC (AWS-0101) used here has the capability to excite both polarizations simultaneously, thereby is creating dual beam in two different directions simultaneously in receive mode.
The output 3 rd -order intercept point (OIP3) is a figure of merit to evaluate the linearity of an amplifier or a system of amplifier blocks. Also, the OIP3 is a useful term to estimate the 3 rd -order intermodulation (IM3) components and the adjacent channel power ratio (ACPR) of a transmitter for complex modulation measurements. A phased array operating in a transmit mode combines the output of several power amplifiers in free space, and the far-field contains an average and a scaled version of the linear and nonlinear components of the individual power amplifiers. In this paper, a method to determine the OIP3 of phased-array amplifiers using a far-field measurement is derived and verified by experiment. The far-field OIP3 is then measured using a 5G 28 GHz 32-element phased array employing 2x2 beamformer chips, and the far-field derived OIP3 agrees well with measurements done on a single amplifier. This technique therefore allows the user to determine the (average) OIP3 of the power amplifiers used in an array even if they do not have access to the individual beamformer chip. An additional benefit is the ability of characterizing the PCB bias network resonances in a phased-array environment.
Magnetoelectric (ME) antennas have recently been demonstrated as a promising solution for very low frequency (VLF) communications, for their 2–3 orders of smaller dimensions and better immunity to electrical interferences than conventional electric antennas. Antenna arrays are widely used as an effective approach to enhance radiation field intensity. In this work, a new type of ME antenna with high quality factor resonator is proposed to enhance the radiation field strength and efficiency for antenna arrays. By tunning all the driving signal for each antenna unit at the same frequency and in phase, the radiation field has been linearly increased with the number of antenna arrays. A total radiation field of 200 nT at 1m has been achieved using 12 antenna arrays, which is one order of magnitude enhancement than a single antenna unit. Furthermore, the estimation of antenna efficiency based on the theory of magnetic dipole indicates that ME antennas can potentially enhance the efficiency by a square law of the number of arrays. The demonstrated results and analysis provide the potential for taking advantage of large number of ME antenna arrays for far distance transmission in VLF communications.
Phased Array Radar (PAR) technology can provide tailored, high-quality meteorological observations and is rapidly rising as a candidate for future weather radars. To conduct precise measurements of polarimetric weather variables, it is desired that the radar transmits and receives linearly polarized horizontal (H) and vertical (V) fields through beams well matched in gain and shape at every scanning direction. These characteristics are difficult to achieve because the radiation patterns of phased array antennas inherently depend on polarization, beam shape, and gain in the intended pointing direction. Polarimetric array calibration is critical to produce symmetric and matched co-polar antenna patterns at the two polarizations. In this paper, we present a new polarimetric antenna calibration procedure for the all-digital Horus radar based on holographic back projection of electric fields. Near-field Horus measurements are back-projected onto the plane of the array to derive the co-polar magnitude and phase of the H/V fields radiated by each antenna element. Digital calibration parameters are derived from back-projected fields to compensate for excitation differences and produce uniform radiation at the plane of the array. Preliminary results show that through digital calibration based on back-projected fields, co-polar H and V beam matching can be considerably improved. This naturally improves polarimetric measurement accuracy of the Horus radar by mitigating antenna-induced biases in meteorological estimates.
Phased array antennas are becoming more and more ubiquitous largely in part because of the provision within the 5G protocol for millimeter-wave beamforming. As silicon phased array beamforming core chips become widely available, this opens cost effective solutions for highly agile line of sight (LOS) communications links which utilize classical phased array antennas. This paper describes the development and demonstration of a 0.4 km RF link which operates in the Ku-Band (13.8 GHz), which supports up to 30 Mbps data rates. The developed system is demonstrated utilizing laboratory instruments as well as with a small form factor radio. The developed phased array antenna is able to maintain link at 0.4 km at scan angles up to ±60°, utilizing a digitally modulated signal (32-QAM) at a symbol rate of 5 Msym/s while maintaining an RMS EVM of less than 6%.
We report the first ultra-wide band (UWB) arrays on a doubly curved surface for wide angle electronic scanning. Two different prototypes are developed employing Vivaldi antennas and balanced antipodal Vivaldi antennas (BAVAs) distributed over the surface of a hemisphere. The arrays employ 52 dual-polarized elements. Unit cell simulations demonstrate a good impedance match from 2–12 GHz, and finite array simulations have a realized gain that is within 1 dB of theory. The antennas are metal 3D printed from titanium. Measurements of the arrays will be reported at the conference.
The Millimeter-Wave Scalable Unconstrained Broadband Array (MMW SCUBA) system leverages cutting edge chip integration, additive manufacturing, and packaging technology to realize an 18–50 GHz, dual-polarized, scalable phased array antenna with element-level digital beamforming. We report on the demonstration and test of a 16 element free-space-to-RF prototype, as well as progress on the development of a larger 64 element array prototype build which extends integration from free-space to digits.
Compact antenna test ranges (CATR) are favorable for over-the-air (OTA) measurements of millimeter-wave phased arrays because they use a feed and parabolic reflector to emulate the plane wave condition of far field ranges within a significantly-reduced volume, which reduces OTA path loss and compensates for the limited dynamic range of test instruments such as vector network analyzers (VNA). Error vector magnitude (EVM) is a measure of digitally-modulated signal quality that is increasingly used to benchmark the beamforming performance of millimeter-wave phased arrays, since it includes the effects of each element's radiated power and RF integrated circuit (RFIC) linearity across the signal bandwidth. This paper highlights EVM measurements of independent phased array elements in a CATR using spectrum analysis on a VNA receiver, performed at Keysight in Santa Rosa, CA, USA.
The growth within the satellite communication market continues to expand rapidly with advances in technology. However, the barrier to entry is driven predominately by cost and risk. The cost for research and development, thousands of manhours required from a multidisciplinary team, and the development cost to build and validate a proof of concept can be overwhelming. Especially for those who would like to explore the application space for the first time the cost and the risk may be prohibitive. To help ease the barrier to entry into the phased array technology space for satellite communication, the Aerospace and Defense organization within Analog Devices has developed a Ka band evaluation platform. Coupled with the development platform is a collaboration with Keysight Technologies on array calibration. Phased array antenna calibration has typically been time consuming and expensive. A compact antenna range coupled with commercial test equipment provides an economical and fast solution for calibrating these antennas
A geostationary orbit (GEO)-based radar scatterometer concept is presented here that offers the capability to monitor sea state over surveillance sectors with extended persistence and over a very wide area. Despite the long ranges from GEO, the resolution on the ocean surface can be preserved by employing a configuration of spread-out small satellites (smallsats) using microwave transmitters at moderate power levels. The physical smallsats are kept to a practical number by the use of multiple-input multiple-output (MIMO) beamforming that forms a virtual aperture. As illustrated herein, practical configurations appear to be realizable. Unlike traditional spaceborne radar scatterometers, the concept permits extended and uninterrupted surveillance of selected ocean sectors.
Ice dynamics are a maj or factor in sea level rise and future sea-level rise projections [1]. The vertical velocity profile of the ice is one major knowledge gap in both observations and model experiments. We propose to apply multipass differential interferometric synthetic aperture radar (DInSAR) techniques to data from the Multichannel Coherent Radar Depth Sounder (MCoRDS) to measure the vertical displacement of englacial layers. Estimation of englacial layer vertical displacement requires compensating for the spatial baseline between interferometric antenna pairs using radar trajectory information and estimates of the cross-track layer slope from direction of arrival (DOA) analysis, but airborne systems suffer from unknown spatial baseline errors. The current DInSAR algorithm assumes zero error in the array position information when inferring displacement and the direction of arrival for subsurface scatterers, which means that unincorporated baseline errors map into errors in cross-track slope and vertical velocities. Here we demonstrate a maximum likelihood estimator that jointly estimates the vertical velocity, the cross-track internal layer slope, and the unknown baseline error due to GPS and Inertial Navigation System (INS) errors.
