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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
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| 3. |
- Fan, Jin, et al.
(författare)
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Design of Novel Flat Bend Crossed Dipole for Wideband Phased Array Feed Applications
- 2019
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Ingår i: 2019 International Symposium on Antennas and Propagation, ISAP 2019 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- This paper presents a novel Phased Array Feed (PAF) element based on flat bend crossed dipole fed by 50-Ohm coaxial line. The PAF element is dual-polarized and made from all-metal to minimize Ohmic losses and simplify cryogenic integration. It is optimized for 4- 8 GHz band aiming to possible later integration in the SKA pathfinder PHAROS2. The proposed design can also be a good element candidate of PAF for the Five hundred meter Aperture Spherical Telescope (FAST) and Qi Tai Telescope (QTT) as well as other large radio telescopes.
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| 4. |
- Fan, Jin, et al.
(författare)
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Investigation of ultra-wideband Bowtie antennas for phased array feed application
- 2020
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Ingår i: International Journal of RF and Microwave Computer-Aided Engineering. - : Hindawi Limited. - 1096-4290 .- 1099-047X. ; 30:11
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Tidskriftsartikel (refereegranskat)abstract
- In this article, two new ultra-wideband (UWB) dual-polarized Bowtie antennas are investigated as the elements for a phased array feed for reflectors. In addition to its UWB impedance matching characteristic, the Bowtie antennas have stable large beam-width and a low cross-polar level over a wide frequency band with a compact size, which is an essence for phased array applications. The simulated and measured results state a low ohmic loss, good impedance matching (S11 below −15 dB) and good radiation performance, with a simple structure for easy manufacturing. The proposed antennas can be good candidates for phased array feed (PAF) in FAST and the SKA (square kilometer array) pathfinder PHAROS2 projects, and massive MIMO antennas in wireless communication systems.
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| 5. |
- Liao, Wan-Chun, 1985, et al.
(författare)
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A Directly Matched PA-Integrated K-band Antenna for Efficient mm-Wave High-Power Generation
- 2019
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 18:11, s. 2389-2393
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Liao, Wan-Chun, 1985, et al.
(författare)
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A Ka-Band Active Integrated Antenna for 5G Applications: Initial Design Flow
- 2018
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Ingår i: 2018 2nd URSI Atlantic Radio Science Meeting (AT-RASC).
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Konferensbidrag (refereegranskat)abstract
- Initial technology and design decisions are presented as part of a design flow to realize an active integrated antenna (array) element for 5G applications at Ka-band. The objective is to synthesize an antenna impedance that directly matches the amplifier optimal load impedance in order to maximize the overall efficiency of the integrated antenna-amplifier system while attaining an output power in the range of 15–25 dBm. A strategy to subsequently co-optimize this combined system is also discussed. Direct matching overcomes the insertion losses and bandwidth limitations of impedance-transforming networks, obviates the use of a standard 50-Ohm reference impedance, and potentially results in more cost-effective, more compact, and better performing active antenna designs in general.
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| 7. |
- Liao, Wan-Chun, 1985, et al.
(författare)
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Analysis of the strut and feed blockage effects in radio telescopes with compact UWB feeds
- 2012
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Ingår i: 6th European Conference on Antennas and Propagation, EuCAP 2012; Prague; Czech Republic; 26 March 2012 through 30 March 2012. - 9781457709180 ; , s. 611-615
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Konferensbidrag (refereegranskat)abstract
- The international radio astronomy community is currently pursuing the development of a giant radio telescope known as the Square Kilometre Array (SKA). The SKA reference design consists of several wideband antenna technologies, including reflector antennas fed with novel multi-beam Phased Array Feeds (PAF) and/or wide band Single Pixel Feeds (SPFs) that can operate at frequencies from 1 to 10 GHz [1], [2]. The baseline of this design represents an array of several hundred to a few thousand reflector antennas of 15-m diameter and that will realize sensitivity of 10,000 m 2/K. During the past years, several different reflector and feed concepts have been proposed and examined, but only a small number of these design options (that have a sufficient level of maturity) will be built and tested in a set-up that is closely resembling the final SKA system [3]. These tests are aimed to evaluate the overall system performance as well as construction and operational costs. The final choices for the dish and feed evaluation tests might include: (i) off-set Gregorian and axi-symmetric reflector antennas and; (ii) an optimized octave corrugated horn and the single-pixel wideband feeds such as quad-ridged horn and Eleven antenna [2], [4].
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| 8. |
- Liao, Wan-Chun, 1985, et al.
(författare)
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Antenna Mutual Coupling Effects in Highly Integrated Transmitter Arrays
- 2020
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Ingår i: 14th European Conference on Antennas and Propagation, EuCAP 2020.
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Konferensbidrag (refereegranskat)abstract
- A scattering parameter re-normalization procedure is proposed to obtain a new set of parameter that directly quantifies the actual coupling and reflection coefficients of power waves in highly integrated array antenna systems employing unequal port terminations. We examine both the intra-element coupling between the radiator and the active circuitry along with the inter-element coupling between the elements of an antenna array and discuss the important differences from the more customary 50-Ohm S-parameters.
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| 9. |
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| 10. |
- Liao, Wan-Chun, 1985
(författare)
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Millimeter-Wave Active Array Antennas Integrating Power Amplifier MMICs through Contactless Interconnects
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Next-generation mobile wireless technologies demand higher data capacity than the modern sub-6 GHz technologies can provide. With abundantly available bandwidth, millimeter waves (e.g., Ka/K bands) can offer data rates of around 10 Gbit/s; however, this shift to higher frequency bands also leads to at least 20 dB more free-space path loss. Active integrated antennas have drawn much attention to compensate for this increased power loss with high-power, energy- efficient, highly integrated array transmitters. Traditionally, amplifiers and antennas are designed separately and interconnected with 50 Ohm intermediate impedance matching networks. The design process typically de-emphasizes the correlation between antenna mutual coupling effects and amplifier nonlinearity, rendering high power consumption and poor linearity. This research aims to overcome the technical challenges of millimeter-wave active integrated array antennas on delivering high power (15–25 dBm) and high energy efficiency (≥25%) with above 10% bandwidth. A co-design methodology was proposed to maximize the output power, power efficiency, bandwidth, and linearity with defined optimal interface impedances. Contrary to conventional approaches, this methodology accounts for the correlation between mutual coupling effects and nonlinearity. A metallic cavity-backed bowtie slot antenna, with sufficient degrees of freedom in synthesizing a non 50 Ohm complex-valued optimal impedance, was adopted for high radiation efficiency and enhanced bandwidth. To overcome interconnection’s bandwidth and power loss limitations, an on-chip E-plane probe contactless transition be- tween the antenna and amplifier was proposed. An array of such antennas be- comes connected bowtie slots, allowing for wideband and wide-scan array performance. An infinite array active integrated unit cell approach was introduced for large-scale (aperture area ≈100 λ2) active array designs. The proposed co-design flow is applied in designing a Ka-band wideband, wide scan angle (±55°/±40°) active array antenna, consisting of the connected bowtie slot radiator fed through the on-chip probe integrated onto the output of a class AB GaAs pHEMT MMIC PA. The infinite array performance of such elements is experimentally verified, presenting a 11.3% bandwidth with a peak 40% power efficiency, 28 dBm EIRP, and 22 dBm saturated power.
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