DESIGN FOR THE CASE OF ASYMMETRIC REFLECTION

For reflection that is not normal (i.e., an offset feed to reduce feed antenna blockage), a modified phase distribution is required (see Figure 8a). The angle of reflection is set to θ = 15 degrees from normal incidence and the required phase distribution is remapped (see Figure 8b). The number of cells remains the same as for normal reflection.

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Results of the simulation (see Figure 8c) show that the reflectarray creates a far-field beam inclined to θ = 15 degrees as expected. Simulated azimuthal radiation patterns are plotted in Figure 8d over frequency and they share similar characteristics.

Figure 8a

 

Figure 8b

 

Figure 8c

 

Figure 8d

Figure 8 The 1-bit reflectarray for asymmetric reflection: required phase distribution (a), top view (b), simulated 3D radiation pattern (c) and simulated far-field azimuth radiation patterns over frequency (d).

Assembly and Measurement

Figure 9a shows the reflectarray designed for a 15-degree offset feed. |S11| at the input of the horn is shown in Figure 9b as measured in an anechoic chamber (see Figure 9c). Differences between measured and simulated |S11| are attributed to imperfect mechanical alignment and mounting.

In Figure 9d the beam is tilted to the desired angle of reflection, but there is a drop in antenna gain of up to 2.5 dB and deterioration in sidelobe level of about 3 dB. This is attributed to the measurement setup and instrumentation as well as simplifications in the design to limit the number of bits in the phase distribution.

Figure 9a

 

Figure 9b

 

Figure 9c

 

Figure 9d

Figure 9 Prototype of the 1-bit reflectarray with an offset feed: reflecting surface (a), measured versus simulated |S11| (b), test setup (c) and measured far-field azimuth radiation patterns over frequency (d).

CONCLUSIONS

A single-layered Q-Band reflectarray antenna is designed with a 1-bit phase distribution for the metallization pattern on a conventional dielectric substrate. Using inexpensive fabrication methods, a discrete phase distribution for normal and asymmetric reflection is realized in the design of the reflecting surface. The less than 10 × 10 cm reflectarray demonstrates greater than 20 dBi gain. Measured EM characteristics agree well with the simulation. The design is believed to be well-suited for use in mmWave airborne wireless communication and sensing systems. 

ACKNOWLEDGMENT

This work was supported by the Technology Innovation Program (Project Code: 20016463) funded By the Ministry of Trade, Industry & Energy (MOTIE, Korea).

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