| 1. |
- Amani, Navid, 1985, et al.
(author)
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Per-Antenna Power Distribution of a Zero-Forcing Beamformed ULA in pure LOS MU-MIMO
- 2018
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In: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 22:12, s. 2515-2518
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Journal article (peer-reviewed)abstract
- An analytical model is presented to determine the per-antenna power distribution of a beamformed M-element uniform linear array (ULA) as a base station antenna (BSA). The analysis assumes a single sector cell serving two user equipments (UEs) in a downlink multiuser multiple-input multiple-output (MU-MIMO) system employing zeroforcing (ZF) transmission. Determinative design parameters of the BSA configuration are identified. Afterwards, their effects on the power spread across the array are investigated when the positions of the users are random and they are uniformly distributed over the cell. It is shown that the power distribution across the ULA antenna aperture is a periodic function whose characteristics mainly depend on the angular separation of two UEs and the number of BSA elements. A significant variation between ULA input powers is seen to occur if the number of elements in the ULA is smaller than one period of this power distribution function. In order to mitigate the dynamic range of the power variation across the array, an upper bound for the inter-element spacing, depending on the field-of-view (FoV) of the BSA, is defined. It is shown that, in a 20-element ULA, increasing the inter-element spacing from 0.5-wavelength to 1.4-wavelength reduces the power variation from 19 dB to 10 dB for differentiating two close-by UEs with 1 degree angular separation.
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| 2. |
- Bencivenni, Carlo, 1986, et al.
(author)
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Aperiodic Isophoric Slotted Waveguide Antenna for Point-to-Point Communications at Ka-band
- 2017
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In: 2017 INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (ISAP 2017). - 9781538604656
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Conference paper (peer-reviewed)abstract
- We report the intermediate results on a novel slotted waveguide antenna for point-to-point communications at Ka band. The antenna adopts an aperiodic layout with uniformly excited elements capable of meeting the ETSI class II radiation pattern envelop in all planes with high aperture efficiency. A total of 16 regular waveguide subarrays with an aperiodic inter-column spacing along the E-plane are fed by a corporate feed network located underneath. The prototype was milled in three layers of aluminum and bonded by vacuum brazing. Measurements confirm a 15% impedance bandwidth. The simulated patterns satisfy the radiation pattern envelop and have a gain above 28.5 dBi over 29-31 GHz, corresponding to an efficiency better than 80%.
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| 3. |
- Iupikov, Oleg, 1983, et al.
(author)
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Indoor Received Power Prediction Based on Physical Optics (PO): Simulations and Experimental Validation in Industrial Environment
- 2019
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In: 13th European Conference on Antennas and Propagation, EuCAP 2019.
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Conference paper (peer-reviewed)abstract
- This study presents an approach based on Physical Optics computations to predict the receive signal power in an indoor environment. The application in focus pertains the development of highly reliable manufacturing industry processes where wireless communications plays a key role. Our proposed numerical method shows a good agreement with measurement data. It is therefore suggested that Electromagnetic modelling based on computationally efficient Physical Optics algorithms can be used as a complement, an alternative or even a replacement for empirical models requiring time consuming measurement campaigns.
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| 4. |
- Iupikov, Oleg, 1983, et al.
(author)
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Multibeam Focal Plane Arrays with Digital Beamforming for High Precision Space-Borne Ocean Remote Sensing
- 2018
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In: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 66:2, s. 737-748
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Journal article (peer-reviewed)abstract
- The present-day ocean remote sensing instruments that operate at low microwave frequencies are limited in spatial resolution and do not allow for monitoring of the coastal waters. This is due to the difficulties of employing a large reflector antenna on a satellite platform, and generating high-quality pencil beams at multiple frequencies. Recent advances in digital beamforming focal-plane arrays (FPAs) have been exploited in this paper to overcome the above problems. A holistic design procedure for such novel multibeam radiometers has been developed, where: 1) the antenna system specifications are derived directly from the requirements to oceanographic surveys for future satellite missions and 2) the numbers of FPA elements/receivers are determined through a dedicated optimum beamforming procedure minimizing the distance to coast. This approach has been applied to synthesize FPAs for two alternative radiometer systems: a conical scanner with an offset parabolic reflector and a stationary wide-scan torus reflector system, each operating at C -, X-, and Ku-bands. Numerical results predict excellent beam performance for both systems with as low as 0.14% total received power over the land.
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| 5. |
- Ivashina, Marianna, 1975
(author)
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Joint Design and Co-integration of Antenna-IC Systems
- 2019
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In: 13th European Conference on Antennas and Propagation, EuCAP 2019.
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Conference paper (peer-reviewed)abstract
- An overview of design challenges for beamforming active antenna arrays, which are needed to meet high-performance demands of future emerging applications, is presented. The critical role of antenna element mutual coupling on the receiving system sensitivity of array receivers, and effective radiated power of MIMO-type array transmitters is discussed. Trade-offs, common misconceptions, and practical examples are shown and discussed. Techniques towards strong integration between antennas and LNAs/PAs that blurs the geometrical boundaries between them are presented. This will cover mm-wave antenna design examples, where direct matching of active devices to their optimal source/load impedances eliminates the losses of 50-Ohm impedance matching networks. An antenna-integrated high-efficiency (Doherty) PA, operating at the sub-6 GHz band and utilizing active load modulation, will be taken as an on-antenna power combining example, including optimization aspects and over-the-air characterization.
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| 6. |
- Liao, Wan-Chun, 1985, et al.
(author)
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A Directly Matched PA-Integrated K-band Antenna for Efficient mm-Wave High-Power Generation
- 2019
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In: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 18:11, s. 2389-2393
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Journal article (peer-reviewed)abstract
- A K-band slot antenna element with integrated GaN (Gallium nitride) power amplifier (PA) is presented. It has been optimized through a circuit-EM co-design methodology to directly match the transistor drain output to its optimal load impedance ( Zopt=17+j46Ω ) while accounting for the over-the-air coupling effects in the vicinity of the transition between the PA and antenna. This obviates the need for using a potentially lossy and bandwidth-limiting output impedance matching network. The measured PA-integrated antenna gain of 15 dBi with a 40% total efficiency at 28 dBm output power agrees well with the theoretically achievable performance targets. The proposed element is compact ( 0.6×0.5×0.3 λ3 ), and thus well-suited to meet the high-performance demands of future emerging beamforming active antenna array applications.
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| 7. |
- Prinsloo, D.S., et al.
(author)
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Characterization and Performance of an Ultra-Wideband Wide-Coverage Multimode MIMO Antenna
- 2019
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In: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 67:9, s. 5812-5823
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Journal article (peer-reviewed)abstract
- A new ultra-wideband multimode (MM) antenna design that enables the detection/transmission of two orthogonal field components over a nearly hemispherical coverage area is presented in this paper. It integrates and colocates two perpendicularly oriented bow-tie dipole elements, a short convex monopole and four horizontally oriented tapered slot antenna (TSA) elements (formed by the dipoles) in order to produce four decoupled and complementary gain patterns. The antenna feeding structure includes four single-ended transmission lines supporting the desired set of individual excitation modes. Experimental verification confirms the predicted negligible coupling between the antenna operating modes and orthogonality of the corresponding radiated field patterns. These unique features can be exploited in applications where pattern and polarization diversity are of importance. In this study, we have evaluated the proposed antenna as a MIMO base station antenna and characterized it in two different propagation scenarios. For this example, it has been shown that the utilization of the additional monopole and TSA modes plays an important role in maximizing MIMO efficiency in line-of-sight (LOS) scenarios and at the same time provides additional independent data streams in rich scattering scenarios. In both considered scenarios, the antenna is shown to have a MIMO frequency bandwidth of 85%.
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| 8. |
- Skou, N., et al.
(author)
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Ultra-High-Performance C-and L-Band Radiometer System for Future Spaceborne Ocean Missions
- 2019
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In: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. - 2151-1535 .- 1939-1404. ; 12:6, s. 1670-1678
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Journal article (peer-reviewed)abstract
- A next-generation real-Aperture spaceborne radiometer system for high-quality ocean measurements is discussed. Instead of illuminating the antenna reflector by a classical feed array of horn antennas in a one-feed-per-beam configuration, a multi-feed-per-beam configuration is chosen. Each antenna beam is thus created by adding the outputs from many small antenna elements in the feed array, thus providing an antenna beam of unsurpassed quality. This solves the classical polarization purity and land/sea contamination issues. The concept requires many microwave receivers and fast analog-To-digital converters as well as fast digital signal processing onboard the satellite. This is discussed, and resource budgets, especially concerning power, are provided.
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| 9. |
- Skou, N., et al.
(author)
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Ultra-high performance C L-band radiometer system for future spaceborne ocean missions
- 2018
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In: 15th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment, MicroRad 2018 - Proceedings. ; , s. 42-47
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Conference paper (peer-reviewed)abstract
- A next generation spaceborne radiometer system for hi-quality ocean measurements is discussed. Instead of a classical horn, a focal plane array is used as antenna feed. The antenna beam is created by adding the outputs from many small antenna elements, thus providing an antenna beam of unsurpassed quality. This solves the classical polarization purity and land/sea contamination issues. The concept requires many microwave receivers and fast analog-to-digital converters as well as fast digital signal processing on-board the satellite. This is discussed, and resource budgets, especially concerning power, are provided.
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| 10. |
- Villiers, Dirk I. L. de, et al.
(author)
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Effects of diffraction and feed pattern variation in shaped offset gregorian reflectors
- 2018
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In: IEICE Transactions on Communications. - 1745-1345 .- 0916-8516. ; E101B:2, s. 316-323
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Journal article (peer-reviewed)abstract
- Designing shaped offset Gregorian reflector systems to operate with several interchangeable feed horns, over frequency bandwidths of more than a decade, with multiple, often conflicting, performance figures of merit such as aperture efficiency, receiving sensitivity, sidelobe levels, and cross polarization isolation is a difficult optimization problem. An additional complication may be that the radiation patterns of all the feeds to be used in the system are not known at the time of the dish designs, as upgrades to the feeds may happen throughout the lifetime of large reflector systems. This paper presents a systematic parametric study to quantify the effects of the main causes of performance degradation in such a system, i.e. reflector diffraction and feed pattern variations. First, ideal Gaussian feed patterns are used in order to isolate the diffraction effects, and then the ideal patterns are varied to model the effect of using wideband feeds exhibiting radiation pattern variations over frequency. It is shown that the peak position in the shaping parameter space of the receiving sensitivity is not strongly influenced by diffraction - although the peak value is, as expected, reduced at lower frequencies. This allows similar feed patterns to be used in different frequency bands to still produce systems operating near the maximum sensitivity. When using non-ideal feed patterns it is shown that, for most performance metrics, diffraction effects dominate the feed variation performance degradation in smaller dishes. This allows possibly relaxed requirements on the radiation patterns of feeds used to illuminate electrically small reflector systems.
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