However, this technique exhibits several disadvantages, such as the necessity to sweep a rather large bandwidth, leading to complicated hardware design, and possible interference within the operating bandwidth due to the overly-congested microwave spectrum. The radiation of random, complex modes varying as a function of frequency can be performed by mode-mixing cavities, e.g. In this method, the characteristics of the aperture radiated fields are governed by a frequency sweep, with the aperture radiating a distinct radiation pattern at each frequency, which is ideally, orthogonal to the radiated field patterns at other discrete frequencies. In 26, 27, the authors proved that frequency-diverse apertures can be used to retrieve the DoA information of incoming far-field sources. Recently, DoA estimation using single-pixel-based frequency-diverse or dynamically modulated metasurface apertures has gained significant attention 26, 27, 28, 29. A significant advantage of this technique is that the received data from the source is compressed into a single channel, circumventing the necessity to have array-based multiple channels to retrieve the DoA information. As an enabling technology, the compressed sensing paradigm with a single-pixel-based metasurface aperture can substantially simplify the physical layer hardware for DoA estimation. With a higher number of antenna elements in a dense array, the associated radio frequency (RF)-chains are bound to increase, putting a significant pressure on the hardware requirement and deployment cost. This can result in a rather complex system architecture at the receiver unit, especially at millimeter-wave and submillimeter-wave frequencies where radio hardware is expensive and lossy. The drawback of the multi-pixel approach is that, as the operating frequency increases, the number of antennas (and hence the number of data acquisition channels) also increases, and for maximum accuracy, matched channel calibration is required. multi-pixel architecture) and process them using sophisticated DoA estimation algorithms to retrieve the DoA information of incoming far-field sources. This traditional array-based approach makes it necessary to collect the received radar signals from multiple channels (i.e. Typically, the antenna array is synthesized at the Nyquist spatial sampling of half of the operational wavelength. Conventional DoA estimation schemes are based on beamforming techniques, or numerical methods such as MUSIC 21, 22 and ESPRIT 23, 24, 25, with the hardware layer relying on a dense array-based system architecture as a receiving unit. In addition, polarization was shown to be incorporated in antenna arrays in radar systems in order to improve the signal parameter estimation, including direction of arrival (DoA) 15, 16.ДoA estimation is a fundamental problem in array signal processing and plays a vital role in automotive radar 17, sonar 18, channel sounding 19, and wireless communications 20. In near-field imaging, polarimetric imaging can be employed to obtain additional information from the target 12, 13, 14. For example, target polarization properties were analyzed in remote sensing and synthetic aperture radar (SAR) applications in 8, 9, while polarimetric airborne and spaceborne radar platforms were discussed in 10, 11. Moreover, polarization-diversity has been leveraged in a variety of other applications in the literature. Because of the reduced multipath and antenna orientation constraints, dual-polarization and circular polarization are often suitable selections in wireless communication applications 1, 2, 3, 4, 5, 6, 7. Polarization is an important property of wavefronts with a great potential in various application scenarios such as wireless communication 1, 2, 3, 4, 5, 6, 7, radar 8, 9, 10, 11, and imaging 12, 13, 14. It is shown that by encoding and compressing the source generated far-field incident waves into a single channel, we can retrieve high fidelity polarimetric DoA information from compressed measurements. A dynamically reconfigurable wave-chaotic metasurface, which possesses a structured sparsity of dual-polarized coded metamaterial elements, is proposed for the proof of concept. We show that the polarimetric single-pixel DoA concept can be realized by encoding the polarization information of the incoming waves at the physical layer level within the antenna. The polarimetric nature of the wave-chaotic coded metasurface ensures that the DOA estimation is sensitive to the polarization state of the incoming waves. The single-pixel DoA retrieval technique relies on a dynamically modulated waveform diversity, enabling spatially incoherent radiation masks to encode the incoming plane waves on the radar aperture using a single channel. This paper presents a single-pixel polarimetric compressive sensing (CS)-based direction of arrival (DoA) estimation technique using a cavity backed programmable coding metasurface aperture.

Cst microwave studio award