Low-loss beam synthesizing network based on Epsilon-near-zero(ENZ)medium for on-chip antenna array

Beam synthesizing antenna arrays are essentially demanded for on-chip millimeter wave and terahertz systems.In order to achieve a par-ticular radiation beam,specific amplitude and phase distributions are required for all the array elements,which is conventionally realized through a properly designed feeding network.In the current work,a low-loss feeding network design approach based on epsilon-near-zero(ENZ)medium was proposed for large-scale antenna arrays with different beam requirements.Due to the infinite wavelength within the ENZ medium,a newly-discovered stair-like resonant mode was adopted for assigning a uniform phase distribution to each element,while the amplitudes and positions of these elements were optimized for generating particular beams.To implement the design philosophy in a low-loss manner,a hollow air-filled waveguide near cutoff fre-quency was employed to emulate the ENZ medium,and the bulk sil-icon microelectromechanical systems(MEMS)micromachining tech-nology was utilized for chip-scale integration.As a specific example,a low-sidelobe antenna array at 60.0 GHz was designed,which realized an impedance bandwidth of 2.57%,a gain of 13.6 dBi and a sidelobe level as low as-20.0 dB within the size of 0.5×3.4λ_(0)(2).This method is also compatible with a variety of applications,such as the high-directivity antenna array,non-diffractive Bessel beam antenna array,and so on.Based on this innovative concept of applying ENZ medium to the on-chip antenna array,it shows the advantages of simple struc-ture and low loss for on-chip beam synthesis without complex lossy feeding networks.