| 11. |
- Jonsson, B. Lars G., et al.
(författare)
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Array Antenna Limitations
- 2013
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 12, s. 1539-1542
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Tidskriftsartikel (refereegranskat)abstract
- This letter defines a physical-bound-based array figure of merit for both single and multiband array antennas. It provides a measure to compare their performance with respect to return loss, bandwidth(s), thickness of the array over the ground plane, and scan range. The result is based on a sum-rule result of Rozanov-type for linear polarization. For single-band antennas, it extends an existing limit for a given fixed scan-angle to include the whole scan range of the array, as well as the unit-cell structure in the bound. The letter ends with an investigation of the array figure of merit for some wideband and/or wide-scan antennas with linear polarization. We find arrays with a figure of merit >0.6 that empirically defines high-performance antennas with respect to this measure.
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| 12. |
- Karandikar, Yogesh, 1982
(författare)
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Pattern studies of two parallel dipoles above ground plane in eleven configuration as feed for reflector antenna
- 2010
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 9, s. 558-561
-
Tidskriftsartikel (refereegranskat)abstract
- The patterns of dual dipoles above a ground plane in the so-called "Eleven" configuration are presented. It is shown that these patterns can be shaped to get different beamwidths to better fit reflectors with different F/D ratios while maintaining beam symmetry. Linear as well as curved dipoles are considered. The effect of finite ground plane is also discussed.
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| 13. |
- Karlsson, Kristian, 1973, et al.
(författare)
-
Doppler Spread in Reverberation Chamber Predicted From Measurements During Step-Wise Stationary Stirring
- 2010
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 9, s. 497 - 500
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Tidskriftsartikel (refereegranskat)abstract
- We propose a simple method to accurately predict Doppler spread in a reverberation chamber (RC) by using frequency domain S-parameters measured with a vector network analyzer (VNA) at many fixed stirrer positions (step-wise stationary mode). Thus, the measurements are done under repeatable stationary conditions, so no Doppler shift is present during the actual measurements. Still, this letter shows that the measured S-parameters in step-wise stationary mode can be used to determine Doppler spread appearing during continuous movement of the stirrers. This can be done by computation for any stirrer speed by assuming that the fixed stirrer position steps are the time steps of a continuous movement of the stirrers, and by adding a virtual stirrer speed between the positions corresponding to the desired continuous movement of the stirrers. The computed Doppler spreads are validated over a large frequency band by measuring the time-varying S-parameters for a given stirrer speed.
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| 14. |
- Karlsson, Kristian, et al.
(författare)
-
On OTA test in the presence of doppler spreads in a reverberation chamber
- 2013
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 12, s. 886-889
-
Tidskriftsartikel (refereegranskat)abstract
- In this letter, over-the-air (OTA) tests of the performance of the IEEE 802.11p radio system are performed in a reverberation chamber (RC) that is equipped with a fast rotating mode stirrer. By varying the speed of the mode stirrer, different levels of Doppler spreads are created, and the 802.11p radio system is tested accordingly. As expected, the Doppler spread affects the package error rate (PER) of the radio system adversely. In addition to measurements, a simple PER model is presented, which sheds some light into the OTA tests.
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| 15. |
- Kildal, Per-Simon, 1951, et al.
(författare)
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Threshold Receiver Model for Throughput of Wireless Devices with MIMO and Frequency Diversity Measured in Reverberation Chamber
- 2011
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 10, s. 1201-1204
-
Tidskriftsartikel (refereegranskat)abstract
- We present a simple theoretical model for the throughput data rate of a wireless LTE device including the improvements of data rate due to diversity in frequency (OFDM) and spatial domains (MIMO) under frequency selective fading. The model is based on defining an ideal threshold receiver for the line-of-sight (LOS) case, corresponding to reception with advanced error-correcting codes. The theoretical throughput model is in agreement with measurements in a reverberation chamber of a commercial LTE device for the 1 x 2 SIMO case, both regarding diversity and MIMO array gains, and it can therefore be used to complement measured results in evaluation of performance of LTE devices.
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| 16. |
- Liu, Qi, et al.
(författare)
-
Capacitively Loaded, Inductively Coupled Fed Loop Antenna With an Omnidirectional Radiation Pattern for UHF RFID Tags
- 2013
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1225 .- 1548-5757. ; 12, s. 1161-1164
-
Tidskriftsartikel (refereegranskat)abstract
- A capacitively loaded, inductively coupled fed loop antenna with an omnidirectional radiation pattern for UHF radio frequency identification (RFID) tags is proposed. The inductively coupled feed structure is beneficial for conjugate impedance matching. The loaded capacitors in the radiating and feeding loops allow for easy control of the resonant frequency and the antenna reactance, respectively. The omnidirectional radiation pattern on the horizontal plane makes the proposed tag insensitive to be mounted on different target objects. With a small size of 43 x 43 mm(2), the measured maximum reading range of the prototype is 9.5 m with a total transmitted power of 4.0 W effective isotropic radiated power (EIRP).
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| 17. |
- Moteasselian, Alireza, et al.
(författare)
-
A Helix Excited Circularly Polarized Hollow Cylindrical Dielectric Resonator Antenna
- 2013
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 12, s. 535-538
-
Tidskriftsartikel (refereegranskat)abstract
- In this letter, we use a helix to excite two orthogonal HE11 delta modes in phase quadrature in a hollow cylindrical dielectric resonator antenna to generate circular polarization. As compared to our previous work, it is shown that replacing the cylindrical dielectric resonator antenna with a hollow cylindrical-shaped one leads to a significant enhancement in the 3-dB axial-ratio bandwidth. A design guideline is provided, and three design cases are presented. A prototype for one of the designs is fabricated and measured. Measured and simulated data are presented and discussed. It is shown that the 3-dB axial-ratio bandwidth increases as the wall thickness of the hollow cylindrical dielectric resonator decreases. Furthermore, a reduction in the wall thickness requires a longer helix exciter for similar performance.
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| 18. |
- Oloumi, Daniel, et al.
(författare)
-
Miniaturized Reflectarray Unit Cell Using Fractal-Shaped Patch-Slot Configuration
- 2012
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - : IEEE. - 1536-1225 .- 1548-5757. ; 11, s. 10-13
-
Tidskriftsartikel (refereegranskat)abstract
- This letter introduces a new class of miniaturized reflectarray unit cells with increased phase swing employing Minkowski fractal-shaped patch-slot elements. Square, 1st Minkowski, and 2nd Minkowski fractal patches are designed as a reflectarray unit cell. A slot with variable lengths of mm is used in the ground plane to perform the phase variation function. The resonant frequency corresponding to the maximum phase swing is reduced from 10.6 GHz for the square patch down to 8.8 and 8.3 GHz for the first-and second-order Minkowski fractal patches, respectively, which is equivalent to 17% and 22% size reduction. Unit cells with different patch type and slot length are fabricated, and close agreement is observed between the measured and simulated results. As it has been proven for conventional phased array antennas, this size reduction can lead to a decrease in mutual coupling in reflectarray antennas. Alternatively, it allows for smaller distance between reflectarray antenna elements, which renders a wider beam-scanning range.
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| 19. |
- Pan, Te, et al.
(författare)
-
Compact RFID tag antenna with circular polarization and embedded feed network for metallic objects
- 2014
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 13, s. 1271-1274
-
Tidskriftsartikel (refereegranskat)abstract
- A low-profile radio frequency identification (RFID) tag antenna is proposed with a compact size of 45 × 45~mm2 and circular polarization (CP) for metallic surfaces. A star-shaped slot is etched onto the antenna for the CP and antenna size reduction. A terminal-grounded L-shaped feedline is embedded in the etched slot to efficiently excite the wideband CP mode, complexly match the tag-antenna impedance, and further reduce the antenna size. The embedded feed structure also helps achieve a relatively higher gain, resulting in a longer reading range. The proposed antenna can cover the impedance bandwidth of 60 MHz (from 880 to 940 MHz) as well as the 3-dB CP bandwidth of 12 MHz (from 905 to 917 MHz). Further results demonstrate that the proposed tag antenna provides a stable reading range when mounted on metal plates of various sizes.
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| 20. |
- Pucci, Elena, 1982, et al.
(författare)
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Enhancing the efficiency of compact patch antennas composed of split ring resonators by using lumped capacitors
- 2012
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 11, s. 1362-1365
-
Tidskriftsartikel (refereegranskat)abstract
- A new type of small patch antenna with low profile and enhanced radiation efficiency is proposed in this letter. The antenna is realized with a double layer of low-permittivity material (polypropylene, εr = 2.2). The lower layer is used for the feeding of the antenna, and split ring resonators (SRRs) are printed on top of the upper layer acting as radiating elements. The compactness is provided by shorting the rings to the ground plane with two metal pins. Although this antenna presented initially a dual band of operation, it has been demonstrated how the use of a lumped capacitor in the inner ring can increase the total radiation efficiency of the antenna performing a single-band response. Therefore, when the two original operation frequency bands coincide, a manufactured prototype of the antenna demonstrated a measured radiation efficiency of 73% that can be provided at the operation frequency of 1.29 GHz.
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