Abstract
In this paper, a broadband circularly polarized (CP) microstrip antenna array using simplified composite right/left-handed transmission lines (SCRLH-TLs) based sequential rotation (SR) feed network is presented. The characteristics of a SCRLH-TL are investigated initially. Then, a broadband low insertion loss 45o phase shifter is designed using the SCRLH-TL and the phase shifter is em- ployed in constructing a SR feed network for CP antenna array. To validate the design method of the SR feed net- work, a 2×2 antenna array comprising sequentially rotated coupled stacked CP antenna elements is designed, fabri- cated and measured. Both the simulated and measured results indicate that the performances of the antenna ele- ment are further enhanced when the SR network is used. The antenna array exhibits the VSWR less than 1.8 from 4 GHz to 7 GHz and the axial ratio (AR) less than 3 dB from 4.4 GHz to 6.8 GHz. Also, high peak gain of 13.7 dBic is obtained. Besides, the normalized radiation patterns at the operating frequencies are symmetrical and the sidelobe levels are low at φ = 0o and φ = 90o.
Highlights
Due to their low profile, easy fabrication and flexibility in orientation angle between transmitter and receiver antennas, circularly polarized (CP) microstrip antenna arrays have become an excellent choice for applications in communication systems such as satellite, mobile, radar tracking and the remote control and telemetry [1,2,3]
Simulated results of sequential rotation (SR) feed network. (a) S-parameters for SR feed network based on the SCRLH-TLs. (b) Phase difference for SR feed network based on the SCRLH-TLs. (c) S-parameters for SR feed network based on the normal TLs. (d) Phase difference for SR feed network based on the normal TLs
All of the results indicate that the proposed SR feed network has a good potential in designing a broadband CP antenna array
Summary
Due to their low profile, easy fabrication and flexibility in orientation angle between transmitter and receiver antennas, circularly polarized (CP) microstrip antenna arrays have become an excellent choice for applications in communication systems such as satellite, mobile, radar tracking and the remote control and telemetry [1,2,3]. Many disadvantages, such as narrow bandwidth and relatively high-fed line losses, are often along with the merits. Sequential rotation (SR) feed technique has been proved an effective way to design CP antenna arrays with broadband, high polarization purity and symmetric radiation patterns. The easy fabrication of the antenna array makes it very useful in broadband systems
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