Figure 10 shows simulated and measured antenna gain for the proposed array with P2 excited. The simulated gain with decoupling is slightly larger than without. The resonant frequency and gain curve is also shifted higher in frequency due to the parasitic effects of the decoupling structures. The measured peak gain is 1.2 dBic, which is slightly lower than simulated. This difference is attributed to fabricated tolerances and additional loss from the SMA connectors.

Figure 10

Figure 10 Measured and simulated RHCP peak gain of the three-element closely-spaced CP array with P2 excited.

Figure 11a shows simulated and measured radiation patterns in the YoZ plane with P2 excited. There is good agreement between simulation and measurement. Due to the effects caused by the mechanical turntable (see Figure 8b), the measured radiation beam pattern is only slightly distorted. Laboratory limitations precluded measurements in the XoZ plane, but simulated 3D patterns (see Figure 11b) show that well-behaved radiation characteristics in all directions can be expected.

Figure 11a

 

Figure 11b

Figure 11 Measured and simulated RHCP radiation patterns in the YoZ Plane of the three-element closely-spaced CP array with P2 excited at 1.26 GHz (a) and simulated 3D radiation pattern (b).

COMPARISON WITH THE PREVIOUS WORK

Table I compares his work with previously published results. Gao et al.2 proposed a DGS-loaded high isolation patch antenna, but the element spacing is large. Zhang and Pedersen7 and Li et al.11 realized decoupling by using neutralization lines and an EBG surface, respectively; however, their inter-element isolations were not as good. A slot-type antenna based on a decoupling network was proposed by Y. and K. M. Cheng,14 but it also has a large element spacing. Compared with previous work, the closely-spaced CP array described here not only realizes a miniaturized design (compact array spacing) but also obtains high isolation by using a novel hybrid decoupling method.

Table 1

CONCLUSION

In this work, a novel hybrid CP decoupling method is proposed for closely-spaced array applications. The hybrid decoupling design can be divided into two parts: compact coupling lines (coupling cancelation) and miniaturized meta-resonator structure (coupling suppression). To verify the decoupling principle, a closely-spaced three-element CP array is designed for the Beidou B3 band (1.25 to 1.28 GHz). Based on the hybrid decoupling structure, minimum isolation between elements of the CP array is increased from 15 dB to 23 dB. The array is compact in size and exhibits good CP radiation performance. Although this work has demonstrated the application of this decoupling method for a linear array, the principle can be applied to planar arrays as well.

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