Sanghamitro Das

In this paper, a novel wideband, circular polarized, broadside passive array antenna (PAA) with a single feeding network is proposed covering X/Ku-band satellite communication (SATCOM) frequency bands. The radiating element includes a stacked microstrip patch configuration and has a ∼42% impedance bandwidth that covers both the downlink (10.7-12.7 GHz) and uplink (14-14.5 GHz) bands. An air gap was introduced between the driven and the parasitic patch layers, along with stubs on both the patches for wide bandwidth (BW) operation. The 4×4 fixed beam array is formed using a sequential rotation (SR) technique that enables a wide axial ratio (AR) bandwidth. The gain is fairly stable across the operating bandwidth with a peak simulated gain of 11.8 dBic at 11.7 GHz. The gain variation is 2.9 dB at 10.7-14.5 GHz. Moreover, a 3-dB AR bandwidth of ∼43.7% is achieved. A prototype array antenna demonstrates good agreement between simulated and measured performances. The proposed single circularly polarized (CP) arrays feature a planar structure, a wide operational bandwidth, and high polarization purity. These attributes make the antenna an excellent candidate for LEO (low earth orbit) satellite communications.

A highly miniaturised electrically small square loop antenna has been designed for operation at 2.5 GHz. The antenna is loaded using a simple series combination of two lumped inductors and two interdigitated capacitors in order to realise inherent impedance matching at a given miniaturisation level with respect to a specified source impedance, without using any external matching network. The designed antenna has an overall size of 0.061 λ ₀ × 0.061 λ ₀ , which is approximately 75.6% miniaturised in terms of total loop length and 94% miniaturised in terms of overall footprint. The designed antenna is fabricated and the corresponding impedance matching and radiation patterns are measured, which are found to be in reasonable agreement with their simulated counterparts. Moreover, an investigation with two closely spaced electrically small SLAs, one for transmitting and the other for receiving, is carried out in this work in pursuit of maximising the isolation, which plays a crucial role in the Tx/Rx systems.

A broadband balanced antipodal Vivaldi antenna (BAVA) has been reported along with a novel 3D-printed shaped dielectric lens (SDL) for aiding in gain enhancement, largely towards the higher frequencies. The complete BAVA with SDL (BAVA-SDL) structure exhibits a broad simulated bandwidth of 3.8 GHz to over 60 GHz ( $\mathbf { > }15.8$ :1). The 3D SDL enables an ever-increasing gain profile by compensating for the large phase errors that occur particularly at higher frequencies over a wide range of 45–60 GHz. The maximum simulated broadside gain reaches 24 dBi at 54 GHz. A Digital Light Processing (DLP) based 3D printing technique has been used to fabricate the SDL, where periodic unit lattice cells with air inclusions have been implemented for manipulating the corresponding relative permittivity. Measurements could be carried out until 45 GHz due to limitations from the fabrication process. Nevertheless, the measured results were found to be in very good agreement with their simulated counterparts.

Phased arrays in the last decade have made tremendous progress, mostly as a result of the maturity of silicon beamforming chipsets. With 5G communication links on the horizon, silicon beamformers have been front and center and commercial development has been accelerated, and as a result price economies have scaled [1] . System-level considerations are now being made, specifically regarding the level of integration [2] , [3] , [4] , [5] , [6] , [7] . There have been many papers in the literature which document various high-performance phased arrays. Some notable published papers on this topic include [8] , which presents a dual-band multistandard 5G millimeter-wave phased array; [9] , an area-efficient 5G millimeter-wave transceiver front end; [10] , a K-band hybrid packaged phased-array receiver with integrated antenna array; [11] , a 33.5–37.5 GHz beamforming transceiver with hybrid architecture phase shifters; [12] , a wide-band transmit and receive phased array which operates from 16 to 52 GHz; [13] , which presents a silicon beamforming chip which can support C -, X -, Ku -, and Ka -bands; [14] , a dual-polarized transmit phased array for a common data link; [15] , a 1024-element satellite communication receive-only phased array; [16] and [17] , which present a wafer-scaled phased array that operates in the G -band; and finally, [18] , which presents a D -band submillimeter wave beamforming transceiver in silicon germanium (SiGe). Much of the focus of these papers has been on radio-frequency integrated circuit (RFIC) development, where silicon and SiGe afford the ability to support multiple channels and therefore tighter integration, as well as nuanced design and integration of the beamformer with a printed circuit board (PCB) antenna array. However, only a few papers describe the necessary steps, as well as the equipment needed, to do a line-of-sight (LOS), over-the-air (OTA) microwave link using digitally modulated signals. This is, after all, the final use case for these types of electronically scanned antenna arrays, the ability to close LOS microwave links.

A novel flat-panel 8×8 wideband dual circularly polarized electronically-scanned phased array antenna is proposed, which covers the satellite communications bands of 22.55–23.55 GHz and 25.5–27.5 GHz. A circularly polarized stacked microstrip patch antenna is used as the element radiator with a structural modification on the parasitic patch to minimize gain variation. Since the axial ratio (AR) bandwidth of the element radiator is inherently narrow, sequential rotation is employed to yield a wide AR bandwidth while forming the 2×2 subarray, which is then used as a building block to construct the larger 8×8 phased array. The phased array has a simulated scan range of ±51°, ±46° and ±36° at 23 GHz, 24 GHz and 26.5 GHz, respectively, assuming ≤3-dB scan loss and AR. A beamforming network (BFN) is integrated within the stackup of the phased array that comprises a commercially available silicon beamforming chip. This facilitates beam steering through the independent control of the input amplitudes and phases of the individual element radiators. The practical effects of the BFN on the scanning performance of the 8×8 phased array is studied, which is found to slightly degrade the scan ranges. Finally, experiments were performed on the fabricated prototype, and the measured scan data showed good correspondence with their simulated counterparts with >41° and 35° scan ranges (in +θ direction) at 24 GHz and 26.5 GHz, respectively. The corresponding EIRp and G/T of the 8×8 phased array are also estimated through measurements.

In this paper, a wideband (22-28 GHz), polarization reconfigurable, flat panel, 8x8 transmit (Tx)/receive (Rx) phased array antenna (PAA) is proposed. The array offers a realized gain of 22-23 dBi/dBic in the broadside direction and scans to approximately ±50° while maintaining 3dB gain drop/scan loss, low cross-polarized fields, and axial ratio (AR) below 3dB (in case of circular polarization (CP)) over the entire bandwidth within the given scan range. By utilizing the amplitude and phase control mechanism of the Radio Frequency Integrated Circuits (RFICs) employed for the beamforming network (BFN), each single radiating element of the array can work in four polarization cases such as horizontal (X-), vertical (Y-), left-hand circular and right-hand circular polarizations. The single element is a novel stacked patch configuration with L-shaped stubs at the two opposite corners of the driven patch and stubs on radiating edges of both the driven and parasitic patches. The radiator offers a wideband performance in addition to resolving the poor isolation between the two ports, thereby improving the cross-polarized fields and AR over the entire bandwidth. The radiating elements are arranged in a unique way in the array such that the benefit of element mirroring is achieved during the dual linear cases, whereas the benefit of sequential rotation of elements is achieved in dual CP cases, which further improves cross-polarized fields and AR. The simulated results are validated through the measurement results for a fabricated PAA prototype for the scanned radiation patterns for all four polarizations in receive mode, antenna gain-to-noise temperature (G/T) in receive mode, and effective isotropic radiated power (EIRP) in transmit mode.

A highly miniaturized 3-D spherical folded dipole antenna has been reported, for which inherent impedance matching is achieved with respect to a practical source impedance by employing a simple series– $LC$ loading combination, thereby engineering its input impedance. In order to maximize its bandwidth, the miniaturized antenna employs a spherical helix structure as the folded arm that occupies the full volume of the corresponding Chu sphere. A bifilar (two folded arms) and a quadrifilar (four folded arms) helix loaded folded dipole antenna are designed, and full-wave simulations show that both the resulting antennas demonstrate excellent impedance matching when miniaturized by 85% in comparison to a resonant dipole operating at the same frequency. Despite the high degree of miniaturization, the resulting radiation efficiencies for the bifilar and quadrifilar antennas are found to be 87.1% and 90.6%, respectively. Furthermore, various quality-factor definitions are explored for the quadrifilar antenna, and it is observed that the resulting quality factor is around 1.83 (1.22) times that predicted by the Chu (Thal) lower bound.

A highly miniaturized three-dimensional spherical folded dipole antenna has been reported, for which inherent impedance matching is achieved with respect to a practical source impedance by employing a simple series-LC loading combination, thereby engineering its input impedance. In order to maximize its bandwidth, the miniaturized antenna employs a spherical helix structure as the folded arm that occupies the full volume of the corresponding Chu sphere. A bifilar (two folded arms) and a quadrifilar (four folded arms) helix loaded folded dipole antenna are designed, and full-wave simulations show that both the resulting antennas demonstrate excellent impedance matching when miniaturized by 85% in comparison to a resonant dipole operating at the same frequency. Despite the high degree of miniaturization, the resulting radiation efficiencies for the bifilar and quadrifilar antennas are found to be 87.1% and 90.6%, respectively. Furthermore, various quality-factor definitions are explored for the quadrifilar antenna, and it is observed that the resulting quality factor is around 1.83 (1.22) times that predicted by the Chu (Thal) lower bound.

A novel miniaturized printed folded dipole antenna has been designed for narrowband sensing applications. It is shown that the antenna may be systematically engineered to achieve matching to a practical source impedance at frequencies well below its half-wavelength resonance using series-LC loading and asymmetrical arm widths. This approach is used to design an inherently well-matched antenna that does not require an external matching network and demonstrates approximately 75% miniaturization, excellent co- to cross-polarization separation, over 24 dB higher realized gain, and strongly improved radiation efficiency relative to an unloaded folded dipole of the same electrically small size. Experimental validation of a fabricated prototype demonstrates excellent agreement with simulations.

A novel miniaturized printed folded dipole antenna has been designed and its usefulness as an RFID tag has been demonstrated. It has been shown that the input impedance of the antenna can be engineered to achieve the required complex impedance by employing series-LC loading and unequal arm widths. The end result is a conjugately well-matched 75%-miniaturized folded dipole antenna that does not require an external matching network and exhibits a useful 30:93% radiation efficiency and 8:09 m simulated read range. Experimental validation of a fabricated prototype demonstrates excellent agreement with simulations.