Electronic Beam Steering Capability Research Articles

On new two-dimensional UHF radar observations of equatorial spread F at the Jicamarca Radio Observatory

We describe a mode for two-dimensional UHF (445 MHz) radar observations of F-region irregularities using the 14-panel version of the advanced modular incoherent scatter radar (AMISR-14). We also present and discuss examples of observations made by this mode. AMISR-14 is installed at the Jicamarca Radio Observatory (JRO, 11.95°S, 76.87°W, ~ 0.5° dip latitude) in Peru and, therefore, allows studies of ionospheric irregularities at the magnetic equator. The new mode takes advantage of the electronic beam-steering capability of the system to scan the equatorial F-region in the east–west direction. Therefore, it produces two-dimensional views of the spatial distribution of sub-meter field-aligned density irregularities in the magnetic equatorial plane. The scans have a temporal resolution of 20 s and allow observations over a zonal distance of approximately 400 km at main F-region heights. While the system has a lower angular and range resolution than interferometric in-beam VHF radar imaging observations available at Jicamarca, it allows a wider field-of-view than that allowed with the VHF system. Here, we describe the mode, and present and discuss examples of observations made with the system. We also discuss implications of these observations for studies of ESF at the JRO.Graphical abstract

Wideband, Beam-Steerable Reflectarray Antennas Exploiting Electronically Reconfigurable Polarization-Rotating Phase Shifters

We present a wideband reflectarray antenna with electronic beam-steering capability. The beam-steerable reflectarray uses an electronically reconfigurable polarization-rotating unit cell (PRUC) that acts as a wideband 1 bit phase shifter. The unit cell consists of four metallic single-headed arrows placed above a ground plane. The four arrows are connected to the unit cell’s bottom surface, which contains two p-i-n diodes for switching and three lumped inductors for RF–DC isolation. Changing the bias states of the two antiparallel p-i-n diodes reconfigures the unit cell between two operating states that provide a +90° and −90° polarization rotation (PR). Simulation results for the unit cell show a wide frequency range of 8.5–11.5 GHz over which the reconfigurable unit cell provides dominant reflection coefficients of >−2 dB and relative phase shifts of 0° and 180° for the two operating states. The proposed unit cell was used to construct a 256-element, fully electronically reconfigurable reflectarray prototype with aperture dimensions of 192 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times192$ </tex-math></inline-formula> mm to demonstrate the design concept. The digital control circuitry needed to individually control the unit cells was also designed and fabricated. Experimental characterization of the reconfigurable reflectarray demonstrated the 2-D beam scanning capability within the scan range of ±60° over a 30% bandwidth.

A Low Cost, Low in-Band RCS Microstrip Phased-Array Antenna With Integrated 2-bit Phase Shifter

In this article, we present a low-cost microstrip phased-array antenna, which is composed of electronically reconfigurable elements. The p-i-n diodes' integrated elements have various functions, such as tunable polarization characteristics and adjustable radiation phases. The high sidelobe level (SLL) due to the 2-bit phase shifter can be reduced by a randomly rotated (RR) array element. It is shown that the array can realize electronic beam-steering capabilities and keep -10 to -14 dB sidelobes without tapering. To verify the above theory, an eight-element linear array prototype working at 3 GHz was designed, fabricated, and tested. Numerical simulations and experimental results show that, by controlling the “ON” and “OFF” states of p-i-n diodes, the radiation beam can be controlled to steer in a circular polarization (CP) mode, wherein the scanning angle is up to ±45°. Furthermore, the principle of suppressing the vector scattering field by the opposite phasing cancellation method can achieve in-band radar cross section (RCS) reduction. Simulation results show that approximately 15 dB in-band RCS reduction can be realized for both bistatic and monostatic RCS reduction with an 8×8 array.

Reconfigurable SIW-Based Leaky-Wave Antenna Composed of Longitudinal Cells

A novel fixed frequency beam-steering leaky-wave antenna (LWA) is presented in this manuscript. Radiation occurs through thin offset longitudinal slots etched on a substrate integrated waveguide (SIW). The beam-steering is achieved by implementing GaAs varactor diodes on the backside of the antenna. Sweeping the bias voltage from 1V to 15V causes the phase constant variation, leading to the 25° beam-steering at 28.5 GHz. The key novelties of the proposed reconfigurable antenna are the low-profile and electronic beam-steering capability using a single varactor diode per cell located on the antenna's backside. Moreover, placing the components on the backside reduces the unwanted blockage effects on the radiation. The antenna's thickness, length, and width are 0.32 mm, 95 mm, 24 mm, respectively. The measured peak realized gain of the proposed antenna at 28.5 GHz is 9 ± 0.8 dBi. Low-profile, small gain variation, ease of fabrication, and electronic beam-steering capability make the proposed LWA suitable for the 5G beam-steering applications. A detailed sensitivity analysis along with the experimental validations were performed to prove the validity of the proposed novel design.

Unit cell for 1-bit reconfigurable transmitarray with circular polarization

The unit cell structure for a transmitarray with circular polarization is presented. The unit cell operates at 5.8 GHz. The dependence of the phase shift on the unit cell parameters is investigated. The realization of the reconfigurable unit cell providing two out-of-phase states is under consideration. The proposed unit cell can be promising for a design of the transmitarray with electronic beamsteering capability.

Ferroelectric beam‐steering antenna

A miniaturised antenna array on a ferroelectric substrate with extraordinary beam-steering capabilities at low applied voltages has been developed by researchers in Romania and Ireland. Phased antenna arrays have a radiation pattern that is the combination of the electromagnetic emissions from individual array elements in different excitation phases. This technology is largely exploited in radar and communication systems due to its electronic beam-steering capabilities. When this technology is integrated into low-power wireless applications or integrated circuits, the phase shifters require low applied voltages to allow reconfiguration of the radiation patterns. In this respect, there is a need for low-voltage controlled phased antenna arrays to be commercialised on a large-scale for 5G communications. RF/biasing measurement setup of the HfZrO-based phased antenna array that was characterised at IMT Detail of the bias circuit for the phase shifters in the HfZrO-based phased antenna array When designing miniaturised antenna arrays for low power wireless communication devices, several issues need to be considered. These include the fact that planar antennas need to be deposited onto very thin substrates with medium/high permittivity values to reduce the device dimensions, and a high radiation efficiency/gain must be achieved by the final device. HfZrO-based ferroelectrics have demonstrated outstanding capabilities for these low power devices as they have high CMOS compatibility, thin deposited layers (5–10 nm), good stability with time and under mechanical/thermal stress and functional ferroelectric properties at low applied voltages. In this Issue of Electronics Letters, Martino Aldrigo and colleagues from IMT Bucharest and Tyndall National Institute, University College Cork, present the full experimental characterisation of a miniaturised antenna phased array that operates in the S frequency band and is suitable for low-power wireless devices. The phase array consists of two gold patch antennas, phase shifters and additional circuitry; all integrated on a wafer of HfxZr1−xO2/high-resistivity silicon. The radiation beam at 2.55 GHz is steered 25° when the 7 nm-thick ferroelectric is biased at low applied DC voltages. This result was obtained while preserving a good gain value (5.36 dBi), in spite of the losses introduced by the ferroelectric material, with an extraordinary figure of merit; FOM = 26.88°/V at 2.55 GHz. Several major challenges had to be overcome in this work, including optimising the growth of HfZrO ferroelectric material, designing a two-element patch antenna array to fit into a four inch HR Si wafer, designing two autonomously-biased phase shifters for the two antennas and optimising the measurement setup to characterise the phased array. The authors believe this work introduces the first prototype of a compact, CMOS-compatible phased antenna array with integrated phase shifters on a ferroelectric HfZrO thin film that offers interesting beam-steering capabilities at low applied voltages. “This is an unprecedented result in the domain of ferroelectric-based microwave devices”. “This work will arouse a growing interest in ferroelectric materials for microwave applications, in view of the increasing demand of performing low-voltage (and low-cost) electronics for 5G-based IoT devices” states Aldrigo. The most important longer-term developments may come from enhancements of the ferroelectric-based phase shifters and from new antenna layouts. Since reporting the work in their Letter, Aldrigo and colleagues have been working on new layouts of ferroelectric-based phase shifters in order to embed them with different antenna layouts. Aldrigo explains “we hope to achieve better performance at even higher frequencies. In this respect, it is our firm intention to further develop the work reported in our Letter.” There are a few major limitations and unexplored avenues associated with this work and research field in general according to the IMT/Tyndall team. New compositions of novel ferroelectric materials could be explored and the thickness of ferroelectric material that guarantees the best magnetic and electronic properties could be further optimised. Additionally, phase shifter layouts that offer the largest phase shift (at the desired frequency) with low insertion loss (i.e. less than 2 dB) and at low bias voltages could also be investigated. Finally, the “smart” integration of ferroelectric-based phase shifters in phased antenna arrays with steering capabilities of ± 90° remains a goal in this research field.

Circularly-Polarized Reconfigurable Transmitarray in Ka-Band With Beam Scanning and Polarization Switching Capabilities

The design, realization, and experimental characterization of a 400-element electronically reconfigurable transmitarray operating in the Ka-band is presented. It is based on linearly polarized unit-cells with 180° phase-shifting capability. Several sequential rotation schemes have been compared numerically to generate a circularly polarized beam over a broad frequency band, and a random distribution has been selected to mitigate spurious cross-polarized side-lobes when scanning the main beam. The 2-D electronic beam-steering capabilities of ±60° have been verified experimentally. The prototype, illuminated by a horn antenna as a focal source, exhibits a broadside gain of 20.8 dBi at 29.0 GHz and a 3-dB bandwidth of 14.6% with radiation efficiency of 58%. The axial ratio remains below 2 dB within this bandwidth. Next, a planar substrate integrated waveguide focal source array was designed in order to reduce the focal distance by about 50% and thereby significantly improve the antenna compactness, and similar radiation performance is demonstrated numerically and experimentally. © 1963-2012 IEEE.

AMISR‐14: Observations of equatorial spread F

AbstractA new, 14‐panel Advanced Modular Incoherent Scatter Radar (AMISR‐14) system was recently deployed at the Jicamarca Radio Observatory. We present results of the first coherent backscatter radar observations of equatorial spread F(ESF) irregularities made with the system. Colocation with the 50 MHz Jicamarca Unattended Long‐term studies of the Ionosphere and Atmosphere (JULIA) radar allowed unique simultaneous observations of meter and submeter irregularities. Observations from both systems produced similar Range‐Time‐Intensity maps during bottom‐type and bottomside ESF events. We were also able to use the electronic beam steering capability of AMISR‐14 to “image” scattering structures in the magnetic equatorial plane and track their appearance, evolution, and decay with a much larger field of view than previously possible at Jicamarca. The results suggest zonal variations in the instability conditions leading to irregularities and demonstrate the dynamic behavior of F region scattering structures as they evolve and drift across the radar beams.

NON LINEAR OPTIMIZATION TECHNIQUE FOR THE REDUCTION OF THE FREQUENCY SCANNING EFFECT IN A PHASED ARRAY BASED ON BROADBAND INJECTION-LOCKED THIRD HARMONIC SELF-OSCILLATING MIXERS

In this work, an electronically tunable large range phase shifter based on a broadband Injection-Locked Third Harmonic Self- Oscillating Mixer (IL3HSOM) is designed and analyzed. This multi- functional circuit generates a down-converted Intermediate Frequency (IF) signal and provides a theoretical 540 - continuous phase shift range. The conversion gain and the bandwidth of the circuit are optimized through bifurcation control techniques. The IL3HSOM will be used as the core of a broadband phased antenna array with electronic beam-steering capabilities. The use of a multi-harmonic load based on an arbitrarily width modulated transmission line allows the nonlinear optimization of the circuit phase shift frequency response to compensate the frequency scanning efiect, which negatively in∞uences the performance of broadband antenna arrays.

Decay of 3‐m‐scale ionospheric irregularities associated with a plasma bubble observed with the Equatorial Atmosphere Radar

We investigated the decay processes of 3‐m‐scale ionospheric irregularities associated with plasma bubbles by multi‐instrument observations. The observations were made using the Equatorial Atmosphere Radar (EAR), a 630‐nm airglow imager, and ionosondes. The EAR's electronic beam steering capability allowed us to see the temporal evolution of 3‐m‐scale irregularities associated with plasma bubbles in two‐dimensional views. Around midnight on 28 and 31 March 2006, the EAR detected plasma bubbles that drifted into its field of view. When their eastward drift motion slowed and they finally stopped moving eastward, the 3‐m‐scale irregularities decayed. These results suggest that instability driven by the eastward neutral wind kept the 3‐m‐scale irregularities in matured plasma bubbles, which are in the well‐developed stage, active for several hours after sunset. The stagnated plasma bubbles drifted downward with the ambient westward electric field. This drift resulted in the backscatter echo patterns seen in the range‐time‐intensity (RTI) plots which look like those associated with mid‐latitude plumes.

An Integrated Phased Array Antenna Design Using Ferroelectric Materials and the Continuous Transverse Stub Technology

In this paper, a new integrated phased array antenna system employing the ferroelectric materials technology for electronic beam steering capabilities is described. The design integrates a ferroelectric coplanar waveguide phase shifter with the continuous transverse stub (CTS) array. The phase shifter employs a multi-dielectric substrate and includes a thin layer of silicon dioxide between the signal conductors and the ferroelectric material to reduce the insertion losses and produce good impedance matching. The coplanar waveguide-based multi-dielectric layer design demonstrated an effective ferroelectric biasing architecture and exhibited an increase in figure of merit by up to 8deg/dB from that of the direct metallization approach. An integrated two elements phased array antenna is developed and demonstrates linearly polarized radiation with +/-20deg of beam scanning between the unbiased and biased states of the ferroelectric phase shifter

Array feed synthesis for correction of reflector distortion and vernier beamsteering

An algorithmic procedure is described for the synthesis of a planar-array for paraboloidal reflectors to provide simultaneously electronic correction of systematic reflector surface distortions as well as a vernier electronic beamsteering capability. Several f/D ratios and distortion models were examined that are typical of large paraboloidal reflectors. Numerical results are presented showing that, for the range of distortion models considered, significant on-axis gain restoration can be achieved with a one-ring (seven-element) array. However, with seven elements, the array parameters that maximize system gain, do not provide uniform beam-steering (+or-1 BW) and an additional ring (19 elements) is required. For arrays either 7 or 19 elements, the results indicate that the use of high-aperture-efficiency elements in the array yields higher system gain than can be obtained with elements having lower aperture efficiency. Contour plots of the focal-plane fields are also presented for various distortion and beam-scan-angle cases, showing the dynamic nature of the problem.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>