A Polarization Rotation AMC-based PolarizationReconfigurable Dipole Antenna Wanchen Yang, Wenquan Che, Huayan Jin, Wenjie Feng Department of Communication Engineering, Nanjing University of Science and Technology, Nanjing, China
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Abstract—Based on polarization rotation artificial magnetic conductor (PRAMC) structure, a novel multi-polarized dipole antenna with left-handed, right-handed circular polarizations and linear polarizations is proposed. In addition, a switchable network is designed using RFIC switches. Combing the multipolarized antenna with the network, a novel polarizationreconfigurable method is achieved. Compared with the reported metamaterial-based polarization-reconfigurable antennas, this work has the simplest and most easy-operated reconfiguration mechanism, as well as high performance.
II. POLARIZATION RECONFIGURABLE DIPOLE ANTENNA A. PRAMC-based Multi-polarized Dipole Antenna
Keywords—artificial magnetic conductor (AMC); axial ratio; metamaterial; polarization reconfigurable antenna
I. INTRODUCTION With the development of multifunction requirements in wireless communication systems, reconfigurable antennas are required to fulfill these demands with multiple frequencies, radiation patterns or polarizations. Due to the advantage of avoiding fading loss caused by multipath effects, polarizationreconfigurable antennas has been widely investigated [1]. As we know, metamaterial [2] has wide applications and one of which is on the design of planar antennas with improved performances. Recently, metamaterial, as a novel method, is applied in the design of the polarizationreconfigurable antenna [3] [4]. In [3], a slot antenna using 2D metasurface can be reconfigured to operate in left-handed CP (LHCP), right-handed CP (RHCP) and linear polarization (LP) by mechanically rotating the metasurface. Compared to electrical reconfigurations such as switches, this mechanical reconfiguration requires movable parts, and has a high risk of mechanical failure. In [4], a novel active electromagnetic band gap (EBG) structure was employed as the ground plane of a wideband monopole antenna for broadband frequency tunable RHCP and LHCP property. But the antenna requires a large amount of varactors, which would cause large complexity and high cost of the antenna installation. Fortunately, a novel polarization rotation artificial magnetic conductor (PRAMC) structure was proposed in [5], and was used as the ground plane of a dipole antenna to not only convert polarization from LP to CP, but also achieve good achieve circular performance with large 3-dB AR bandwidth and beamwidth. In this paper, based on this PRAMC structure, a novel multi-polarized antenna is proposed. By a switchable network, a polarizationreconfigurable antenna is achieved. In contrast, the new reconfigurable mechanism is simpler and easier to be operated than other metamaterial-based reconfigurable antennas[3] [4].
Fig. 1. The topology of the proposed antenna using the PRAMC structure, (a) 3D view, and (b) top view of dipole antenna (d= 3mm, dw= 1.5mm, dl= 12mm, dh= 0.5mm, gl= 2mm, sw= 0.3mm, sg= 0.1mm, sl= 2mm).
Here, the PRAMC structure [5] is chosen to design a differentially-driven multi-polarized dipole antenna. The antenna is formed by a pair of linearly polarized horizontal dipole antennas placed crosswise. The PRAMC structure is used as the ground plane, as shown in Fig. 1. The crossed dipole antenna is etched on a dielectric slab of Rogers Duroid 5880 (h1 = 0.5 mm). Two small stubs are loaded at the end of each arm of the crossed dipole. On the back of the antenna, there is a circular metal plate with four strips. The antenna substrate is placed above PRAMC plane with a small distance dh. In addition, four probes are inserted from the bottom of the PRAMC substrate into the metal plate on the back of the antenna for feeding the antenna. The crossed dipole antenna is driven by two pairs of differential signals. According to different input signal, the proposed antenna can achieve three polarization states, as shown in Table I. Applying differential signals on differential port 1 will excite the arms of the cross dipole along y-direction, which would radiate a RHCP wave; similarly, differential port 2 will excite the arms along xdirection for a LHCP wave. Moreover, when the two differential ports are simultaneously excited, two orthogonal polarizations would be superposed to a +45° LP mode.
This work was supported by the 2012 Distinguished Young Scientist Project of NSFC (61225001).
c 978-1-4799-8897-6/15/$31.00 2015 IEEE
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TABLE I. Section Mode 1 Mode 2 Mode 3
DIFFERENT POLARIZATION STATES OF THE ANTENNA Differential Port 1 Port 1 Port 2 On, 0° On, 180° Off Off On, 0° On, 180°
Differential Port 2 Polarization states Port 3 Port 4 RHCP Off Off On, 0° On, 180° LHCP On, 0° On, 180° +45° LP
B. Switch-based Reconfigurable Network A switchable network for achieving three kinds differential signal is designed, as shown in Fig. 2. It consists of one singlepole three-throw (SP3T) RF switch (S1), two single-pole dualthrow (SPDT) RF switches (S2, S3), two 180° hybrid rings and a impedance transformation. The SP3T switch provides three channels which correspond to three polarization states. The two SPDT switches are used to isolate selected channel from other channels. The SP3T and SPDT switches have 12 and 6 pins, respectively. The RFC is the common port, while the J1, J2 and J3 are output ports of the SP3T switch, and RF1, RF2 are those of the SPDT switch. The VDD is DC power supply, and the V1 or V2 are the DC control voltage for selecting the switch states. In addition, the SPDT switch requires shunt capacitors of 100pF at the DC pins of VDD and V1.
reduction. These results indicate that the proposed antenna exhibits good polarization reconfigurability property.
Fig. 3. Photographs of the fabricated polarization reconfigurable antenna: (a) the front, and (b) the bottom.
(a)
Fig. 2. The layout of the switch-based reconfigurable circuit.
C. Simulated and Measured Results Integrated with the switchable network, the proposed multi-polarized antenna can achieve the polarization switching of RHCP, LHCP and +45° LP. For demonstration, it was fabricated with photos shown in Fig. 3. The simulated and measured results for the cases of the three polarization states are shown in Fig. 4. As the RFIC switches can't be simulated, the simulated results of the antenna without network are used here for comparison. As shown in Fig. 4(a), the measured impedance bandwidths for three cases are about 19.6 % from 4.6 to 5.6 GHz, which are much similar to the simulated data. As shown in Fig. 4(b), the measured 3-dB AR bandwidth for RHCP state can reach 15.3%, covering the band from 4.8 to 5.6GHz, which is a little narrower than the simulated data. In addition, the gain curve is stable, and the measured peak value is found to be 4.25 dBi (at 5.2 GHz). It has a decrease of 2.5 dB compared with the simulated result of the antenna without network. The degradation is caused by the 1.8-dB loss of the switches, the 0.2-dB insertion loss of the hybrid ring and the 0.2-dB transition loss of the SMA connector, probably as well as loss of the connecting cable in the measurement setup. So the measured gain is reasonable. As the proposed antenna is 90° rotationally symmetrical, the LHCP mode has a similar performance (see Fig. 4(c)). In addition, for LP state, Fig. 4(d) shows that the peak gain can reach 4.1dBi with a 2.53-dB
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(b)
(c) (d) Fig. 4. Simulated and measured results of the proposed antenna: (a) S paramenter for three states; ARs and gains on (b)RHCP, (c)LHCP and (d)LP.
III.
CONCLUSION
In this paper, a novel PRAMC-based polarizationreconfigurable dipole antenna using a switchable network is proposed. Results show that a simple and easy-operated polarization-reconfigurable mechanism is achieved. REFERENCES [1]
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2015 IEEE 4th Asia-Pacific Conference on Antennas and Propagation (APCAP)
