| 1. |
- Fan, Wei, et al.
(författare)
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Guest Editorial: Metrology for 5G Technologies
- 2019
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Ingår i: IET Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 13:15, s. 2581-2583
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Ivanchenko, Igor, et al.
(författare)
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Combined L–S-bands antenna module
- 2019
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Ingår i: IET Microwaves, Antennas & Propagation. - : IET. - 1751-8725 .- 1751-8733. ; 13:5, s. 541-545
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Tidskriftsartikel (refereegranskat)abstract
- A combined L-S-band antenna module consists of four rectangular patch antennas, two of which operate at the frequencies of the first harmonics (L-band), and two others at the frequencies of the second harmonics (S-band). The module is intended for use in super heterodyne signal reception circuits, for example in studying the various non-linear phenomena. The results of this study are presented in terms of improving the performance of each antenna and minimising their mutual influence. The resonance frequencies of the L-band antenna differ by 50MHz. All the antennas radiate close to the zenith and their beamwidths in two principal planes are virtually the same. At the resonance frequencies, the reflection coefficient is S-11<-30dB for the transmitting antenna, and S-11<-20dB for the receiving antenna. The minimum allowable distance between the antennas is determined, at which their mutual influence can be neglected (S-12<-50dB).
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| 3. |
- Jamaly, Nima, 1979, et al.
(författare)
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Effects of coupling and overspeeding on performance of predictor antenna systems in wireless moving relays
- 2019
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Ingår i: IET Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 13:3, s. 367-372
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Tidskriftsartikel (refereegranskat)abstract
- Using predictor antenna systems for modern wireless moving relays and base stations on top of vehicles such as buses, trains etc. proves to be a reliable approach for collecting channel state information to such fast moving nodes. Recently, it has been shown that coupling between different ports of a multiport antenna system used as a part of a predictor system can reduce the prediction performance. In this study, by integrating position and velocity vectors in the channel covariance matrix as seen at the antenna ports in a rich multipath environment, the authors quantify the impact of antenna coupling on prediction performance. Moreover, practically these predictor systems are designed for a certain target velocity. They further quantify the adverse effect of velocities, different from the target velocity, on prediction performance. In case open-circuit decoupling is necessary, the sensitivity of the predictor antenna system performance with respect to the accuracy of the input network parameters is disclosed.
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| 4. |
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| 5. |
- Karttunen, Aki, et al.
(författare)
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Path loss models with distance-dependent weighted fitting and estimation of censored path loss data
- 2016
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Ingår i: IET Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 10:14, s. 1467-1474
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Tidskriftsartikel (refereegranskat)abstract
- Path loss models are the most fundamental part of wireless propagation channel models. Path loss is typically modelled as a (single-slope or multi-slope) power-law dependency on distance plus a log-normally distributed shadowing attenuation. Determination of the parameters of this model is usually done by fitting the model to results from measurements or ray tracing. The authors show that the typical least-square fitting to those data points is inherently biased to give the best fitting to the link distances that happen to have more evaluation points. A weighted fitting method is developed that emphasises the accuracy at the distance range that is consciously chosen by the user as most important for a system simulation. As a further important point that is typically not taken into account for path loss parameter extraction, the authors show that typically measurement data (but also ray tracing) is censored, i.e. path loss values above a certain threshold cannot be measured. The authors present examples of weighted fitting models, and models with and without the censored data, for 28 GHz channels in urban macrocells, and show that these effects have a significant impact on the extracted parameters and that the fitting accuracy can be improved with the presented methods.
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| 6. |
- Li, JunLong, et al.
(författare)
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Compact broadband circularly-polarised antenna with a backed cavity for UHF RFID applications
- 2019
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Ingår i: IET Microwaves, Antennas & Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 13:6, s. 789-795
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Tidskriftsartikel (refereegranskat)abstract
- A compact broadband circularly-polarised (CP) antenna is designed with a novel method for universal ultra-high-frequency (UHF) radio-frequency identification (RFID) readers. It is composed of a compact ring-shaped patch which aims to decrease the size of the antenna. A quadrature 3 dB coupler placed below the ground plane creates 90 degrees phase differences to generate the CP radiation of the antenna. To improve the performance of the proposed antenna and minimise its size, the authors use a coupling feeding method, an FR4 dielectric slab, and a metal cavity. The coupled feeding is implemented to eliminate the mismatching between the long probe and the ring-shaped patch, and to improve the gain over the operating band. The introduction of an FR4 dielectric slab and a cavity can reduce the antenna size and improve the impedance matching and axial-ratio (AR) bandwidth. The antenna with a backed cavity can increase the front-to-back ratio remarkably and improve the CP performance further. The measured results show that the antenna with a low profile (0.45 lambda(0) x 0.45 lambda(0) x 0.06 lambda(0) at 915 MHz) has the impedance bandwidth of 30.2% (730-990 MHz) and 3 dB AR bandwidth of 24.2% (760-970 MHz). Both the impedance and the AR bandwidth cover the worldwide UHF RFID band.
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| 7. |
- Liu, Qi, et al.
(författare)
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Compact printed two dipole array antenna with a high front-back ratio for ultra-high-frequency radio-frequency identification handheld reader applications
- 2015
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Ingår i: IET Microwaves, Antennas & Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 9:1, s. 73-78
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Tidskriftsartikel (refereegranskat)abstract
- A printed two-dipole array antenna with a high front-back ratio is proposed for ultra-high-frequency (UHF) radio-frequency identification handheld readers. The proposed antenna is a parasitic dual-element array with the ends of both elements folded back towards each other for additional coupling. The antenna features a compact size of 89 mm x 87 mm and works properly with satisfactory gain and total efficiency in the wide UHF band of 860-960 MHz. Furthermore, the front-to-back ratio of 15-26.8 dB, the peak gain of 3.7-4.4 dBi and the total efficiency of more than 80% in the Federal Communication Commission (FCC) band make the proposed antenna attain high performance in the FCC band.
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| 8. |
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| 9. |
- Rezaee, M., et al.
(författare)
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Realisation of carved and iris groove gap waveguide filter and E-plane diplexer for V-band radio link application
- 2017
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Ingår i: IET Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 11:15, s. 2109-2115
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Tidskriftsartikel (refereegranskat)abstract
- The gap waveguide technology is a promising candidate as a cost-effective and low-loss platform for realizing microwave devices particularly at frequencies higher than 40GHz. In this study, two types of groove gap waveguide filters and also a diplexer are presented. Coupling mechanism of these filters is based on carving on the pin plate and iris between adjacent cavities. Two fifth-order Chebyshev filters are realised at 62.5GHz. The proposed diplexer consists of RX and TX iris groove gap waveguide filters at the centre frequency of 59.5 and 62.5GHz and an E-plane groove gap waveguide T-junction. The required transition of the groove gap waveguide to WR-15 is designed and used as an input port of the filters. Moreover, E-plane groove gap waveguide T-junction is designed as the connecting part of the groove gap waveguide filters to the WR-15 antenna port. Finally all parts are integrated. The proposed diplexer is manufactured in aluminium by sawing and milling and then silver plating is done. The RX and TX passbands of the diplexer is around 1.7 and 2.4% with the measured return loss better than 13.6dB and minimum insertion loss of 0.9 and 0.8dB, respectively.
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| 10. |
- Wang, Lu, et al.
(författare)
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High-performance tight coupling microstrip directional coupler with fragment-type compensated structure
- 2017
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Ingår i: IET Microwaves, Antennas & Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 11:7, s. 1057-1063
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a design scheme for high-performance tight coupling microstrip coupler is proposed by adding a fragment-type compensated structure between two loosely coupled lines. Owing to its flexibility and adaptability, the fragment-type compensated structure can not only provide a quarter-wavelength phase shift for coupling enhancement, but also compensate the difference in the phase velocities of the even- and odd-modes for high directivity. Design of the fragment-type compensated structure can be implemented by multi-objective optimisation searching with several design objectives characterising tight coupling couplers. A high-efficiency optimisation searching strategy by using two-dimensional median filtering operator is employed to improve the efficiency of multi-objective optimisation. For demonstration, a high-performance 3-dB tight coupling directional coupler operating at 2 GHz is designed. The measurement data demonstrates a maximum directivity of 47 dB, above 25 dB directivity in a 21.5% bandwidth, a maximum variation of 0.3 dB in the coupling level and a maximum power division ratio of 0.6 dB, which indicate the overall performance better than the previously reported 3-dB couplers. In addition, a simplified theoretical analysis of the proposed coupler and full-wave simulated results are provided for better understanding of the fragment-type compensated structure.
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| 11. |
- Zeng, Xuezhi, 1980, et al.
(författare)
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Investigation of stimulus signals for a time domain microwave imaging system
- 2017
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Ingår i: IET Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 11:11, s. 1636 - 1643
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Tidskriftsartikel (refereegranskat)abstract
- Two different types of time domain signals, pulse and pseudo random noise (PN) sequence, were investigated for a time domain microwave imaging system in order to study the effect of stimulus signals on the system performance. The system's measurement accuracy was investigated when the two different stimulus signals were used, respectively. An imaging test was performed in order to show the effect of transmitted waveforms on the imaging quality. The results suggest that the PN sequence in general gives higher measurement accuracy than the pulse. Better imaging results, although not significant, were also obtained when the pseudo random sequence was employed.
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| 12. |
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