Towards Holographic Antenna Systems for MIMO Radar and Communication Applications

Abstract

A novel synthesis method using an incident angle dependent impedance mapping for holographic multi-feed antennas is presented. Since the unit cells of the holographic antenna are shared with all feeds, it is necessary to merge all of the sub-holograms to a common physical geometry. In the proposed multi-beam synthesis, a individual merged impedance hologram for each feeding point is determined, which has the lowest impedance error to the corresponding analytical holograms. Subsequently, a non pixel-based genetic optimization is used to account for global error minimization across all feeds. The antenna is going to be realized on glass due its lower loss and dispersive properties compared to Teflon-based materials at mm-wave frequencies. In addition to the incident angle dependent hologram synthesis method, an appropriate sub-wavelength pixel has been design and optimized with enhanced anisotropic properties. The implemented holographic multi-feed antenna design has an antenna gain of 23.3 dBi and 23.0 dBi, a polarization purity of 20.3 dB and 23.0 dB and a side-lobe level of −18.5 dB and −19.0 dB with 2 feeds at 77 GHz.

Angle-Dependent Synthesis Method for Holographic Multi-Feed Antennas

“…The constant space independent field amplitudes are described by E 0 . The objective field from (2) corresponds to the electric field distribution of the radiating (−1, −1) LW mode whose spectrum is completely concentrated inside the visible region [30], [31]. The result of the synthesis is an impedance tensor hologram depending on the predefined objective field distribution from (2) and the transverse magnetic field of the SW.…”

“…Since each sub-hologram is realized by a discrete set of UCs, representing the impedance tensor ← → Z sub,n , the arithmetic averaging of all sub-holograms results in an impedance error for each UC on the shared antenna aperture [30]:…”

“…The amplitudes of Z xy,n and Z yx,n do not allow for an assignment of the anisotropic degree to an unambiguous pixel orientation within a 2π-period, since the amplitude curve has two intersections with the same value. Only the phase distribution of the anisotropic tensor components ϕ xy or ϕ yx offers an unambiguous assignment of the pixel orientation and the anisotropic degree [30] (16) where ϕ xy = ϕ yx , β SW is the SW phase constant, and k x , k y are the wavenumbers along the x-and y-direction, respectively. As a result, every UC of each n-th sub-hologram has a pixel orientation φ pxl,n due to its anisotropic tensor components.…”

“…Subsequently, the shared pixel width, which yields the lowest impedance error, is calculated by the incident angle-dependent hologram superposition algorithm (see 3 in Fig. 3) [30]. The shared geometry parameters determine the impedance tensor as function of the incident angle φ inc,n (see 4 in Fig.…”

Electronically Steerable Antennas for Future Heterogeneous Communication Networks: Review and Perspectives

“…Section IV-A), a viable solution to the last-mentioned restriction is also provided by leaky-wave antennas that are based on the holographic principle [263]. They have recently become subject of considerable attention in academia and industry as the surface impedancebased amplitude and phase synthesis of the aperture field distribution allows a low-complexity and highly flexible beam control [264], [265], [266].…”