Abstract
A miniaturized planar microstrip circularly polarized ultrawideband (UWB) antenna loaded by annular-ring slot is proposed and implemented in the paper. With the annular-ring slot loaded in the radiating patch of the antenna, the side of the radiating patch is connected by the asymmetric inverted L-shaped microstrip. At the same time, a quarter of a circle is cut off from the radiating patch. The above designed structure shows improvements on the operating frequency band and realization of the circular polarization radiation. A tapered microstrip is placed between the feed line and the radiating patch to achieve the slow-changing impedance transformation. The results of simulation and measurement demonstrate that the 3 dB axial ratio (AR) fractional bandwidth of the antenna structure achieves 21.25%. The peak gain within the 3 dB axial ratio bandwidth fluctuates between 3.74 and 4.59 dBi. The antenna shows good impedance matching in the ultrawideband range. With the compact structure of the UWB antenna, it has potential application in various wireless communication devices.
Highlights
In recent years, the rapid developments of the radio frequency and microwave integrated circuit technology drive the continuous increment in various wireless communication systems such as satellite communications, mobile communications, and wireless sensor networks
Experiment Results e circular polarization (CP) UWB antenna is fabricated on the FR4 substrate. e photograph is shown in Figure 9. e CP antenna is characterized in the anechoic chamber
Its reflection coefficient is shown in Figure 10. e dashed line in Figure 10 is the measured result of the reflection coefficient. e frequency is from 4.25 GHz to 8.16 GHz with the reflection coefficient less than -10 dB. e impedance bandwidth achieves 3.91 GHz, which is slightly larger than the simulation result
Summary
The rapid developments of the radio frequency and microwave integrated circuit technology drive the continuous increment in various wireless communication systems such as satellite communications, mobile communications, and wireless sensor networks. E antenna can simultaneously transmit and receive two orthogonal CP waves to achieve duplex Both of the two structures show good CP radiation performance [9, 10], wide AR bandwidth, and high gain. To improve the impedance bandwidth, the microstrip patches are integrated in the UWB antenna by reducing the quality factor. E slots can be loaded on the radiation patch to reduce the area of the antenna and to increase the circumference of the antenna. Reference [15] proposes a C-shaped grounded microstrip dual-frequency coplanar waveguide-fed annular slot antenna, which achieves CP through two diagonally loading slots. A tapered microstrip is used to connect the radiating patch with the feed line as the impedance matching slowly transition structure. Detailed information on the proposed structure is reported in the following
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