A plurality of antenna elements on a dielectric substrate are adapted to launch or receive electromagnetic waves in or from a direction substantially away from either a convex or concave edge of the dielectric substrate, wherein at least two of the antenna elements operate in different directions. Slotlines of tapered-slot endfire antennas in a first conductive layer of a first side of the dielectric substrate are coupled to microstrip lines of a second conductive layer on the second side of the dielectric substrate. A bi-conical reflector, conformal cylindrical dielectric lens, or discrete lens array improves the H-plane radiation pattern. Dipole or Yagi-Uda antenna elements on the conductive layer of the dielectric substrate can be used in cooperation with associated reflective elements, either alone or in combination with a corner-reflector of conductive plates attached to the conductive layers proximate to the endfire antenna elements.

Multi-beam antenna

An electronically reconfigurable transmitarray device at 12 GHz is presented in this work. This paper highlights the functioning of this kind of device and thoroughly examines the proposed reconfigurable transmitarray. The architecture is discussed along with the design and selection of all the constituting elements and the prototypes for all of them. In order to add reconfigurability to the transmitarray structure, 360° reflective phase shifters were designed, prototyped and validated for direct application. Eventually, a demonstrative prototype for an active transmitarray with phase shifters was assembled, and radiation pattern measurements were taken in an anechoic chamber to demonstrate the capabilities of this structure.

/pdf/electronically-reconfigurable-transmitarray-at-ku-band-for-57o6jdr1z4.pdf

Electronically Reconfigurable Transmitarray at Ku Band for Microwave Applications

A method is introduced for designing bandpass frequency-selective surfaces (FSSs) using arrays of antenna-filter-antenna (AFA) modules. An AFA module is a filter with radiation ports, which is obtained by integrating two antennas and a nonradiating resonant structure in between. AFA modules are designed based on circuit models and microwave filter design techniques. Three types of these AFA modules are designed using microstrip antennas and coplanar-waveguide resonators, and are used to form FSSs with three- and four-pole shaped bandpass response at 35 GHz. FSS structures are formed by arraying these modules in a periodic grid with an optimal cell size. The proposed concept and the design method are validated using numerical simulation (finite-element method), as well as experimental results.

Antenna-filter-antenna arrays as a class of bandpass frequency-selective surfaces

This paper presents a study on reconfigurable transmit-array (TA) antennas based on multilayer tunable elements. The proposed configuration can be referred to as a multilayer antenna-filter antenna (MAFA) and it can be viewed as an extension of the antenna-filter antenna concept. It consists of multiple antenna layers cascaded to form a spatially distributed bandpass filter. Phase agility is achieved by tuning the resonant frequency of each layer. The main objective of this paper is to introduce a new design technique for MAFA TA antennas. As will be shown, the key feature of the proposed approach is that it allows to simultaneously take into account three key design parameters: the phase tuning range, the maximum acceptable losses per unit cell, and the operating bandwidth. Simulations and experimental results for MAFAs based on varactor-loaded slot antennas will be illustrated to prove the validity of the proposed method. In particular, numerical results will demonstrate that MAFA cells can be designed to provide full phase agility over operating bandwidths of up to 10% with maximum insertion losses of 3 dB. Furthermore, a specific example will show how introducing an inter-layer medium with a higher dielectric permittivity it is possible to reduce the array longitudinal size. Finally, experimental results obtained using a waveguide simulator will be presented for a 1 × 3 five-layer MAFA cell.

Multilayer Antenna-Filter Antenna for Beam-Steering Transmit-Array Applications

A 10-GHz discrete cylindrical lens array with multiple beams is designed and characterized as a receiving angle-diversity array for wireless communications in a multipath environment. The array also has dual-orthogonal polarization and therefore built-in polarization diversity. The array is designed for wide-angle scanning between -45/spl deg/ and 45/spl deg/ and measured scanning patterns are presented. The polarization isolation between the two channels is about 30 dB at boresite and about 10 dB for a 30/spl deg/ scan angle. The addition of the lens array at the very front end of a link shows significant reduction of multipath fading peak-to-null ratio.

http://ecee.colorado.edu/microwave/docs/publications/2002/DPzp_TransAP02.pdf

Multibeam antennas with polarization and angle diversity

This paper presents an X band smart antenna array in which adaptive processing of the received signals is performed by dynamic holographic optical circuitry. The optical circuitry adaptively extracts the principal component of the received signal space, that is the strongest first-order independent temporal component of the ensemble of received signals. The adaptive receiver system can be used, for example, to mitigate multipath interference effects and can separate one received signal from another even though their power spectra may entirely overlap. A prototype two-channel system is designed to fit in a standard-size briefcase and consume less than 50 W of power. The input to the system are modulated waves with a carrier in X band and the output is an electronic demodulated signal. Three major components of this system are described in detail: (1) the quasi-optical lens antenna array front end with angle-of-arrival preprocessing and downconversion, (2) the two-channel electrooptic modulation and optical carrier suppression stage, and (3) the smart optical processor (auto-tuning filter). Component and end-to-end system measurements give quantitative indicators for the usefulness of optical processing in wireless communications.

A lens antenna array with adaptive optical processing

This paper presents a multi-beam antenna array with amplitude-controlled continuous beam steering of each beam. The principle is demonstrated on a Ka-band full-duplex dual-polarized array with an uplink frequency of 24.7GHz and a down-link frequency of 26.7GHz. The array is designed as a discrete lens, and the antenna elements are dual-frequency patches integrated in a 5-layer structure with delay lines that enable multiple beams. The array is spatially fed with a feed corresponding to each beam. Amplitude control at the feed results in continuous beam steering. Theoretical and experimental results for the multi-beam patterns and the beam steering are presented.

http://ieeexplore.ieee.org/iel5/8599/27239/01210459.pdf

Multi-beam discrete lens arrays with amplitude-controlled steering

Suppression of an optical carrier from an RF modulated laser beam of wavelength 532 nm is performed using two-beam coupling in photorefractive barium titanate A theoretical analysis reveals that perfect suppression can be achieved at a specific modulation strength, which depends on the gain and intensity ratio between the two beams The experiments achieve a maximum of -729±24 dB carrier suppression at the theoretically ideal modulation strength, and -610±24 dB for small modulation strengths

http://ecee.colorado.edu/microwave/docs/publications/2001/JAPB_DAvdDPsrAS_01.pdf

-70 dB optical carrier suppression by two-beam coupling in photorefractive media

A prototype X-band active antenna array with adaptive optical processing is presented. The optical processor, referred to as an auto-tuning filter, is able to extract the strongest principal component in a two-signal space with up to 30 dB enhancement with respect to the other signals. The processor is compact (8 cm by 4 cm) and scalable to a large number of antenna elements and incident RF waves (sources). Three major components of this system are described in detail: (1) the lens antenna array front end with angle-of-arrival pre-processing; (2) the electrooptic modulation and optical carrier suppression stage; and (3) the smart optical processor (auto-tuning filter).

Optically smart active antenna arrays

: This paper presents discrete lens antenna array antennas developed for multi-beam communication applications. The lens arrays consist of two back-to-back arrays of antenna element pairs, connected by variable-length transmission lines, which allow the lens to perform a discrete Fourier transform. The array feed is a spatial one, allowing easy and affordable extensions to multiple beams, and straightforward beam reconfigurability. Two prototype arrays at X and K band are discussed. The 10-GHz lens array is designed to have multiple beams up to +/-45 degrees off broadside and dual polarization. The array is characterized in a multipath fading channel as an angle-diversity array. The K-band array is a full-duplex array operating around 25 and 27GHz with the two frequencies at two polarizations. The applications for this array are formation-flying satellites, and S-beam performance will be presented. Continuous steering of half of a beamwidth using amplitude-only control is demonstrated.

/pdf/multibeam-spatially-fed-antenna-arrays-with-amplitude-1ga799ydl0.pdf

S. Romisch

Papers

A lens antenna array with adaptive optical processing

Multi-beam discrete lens arrays with amplitude-controlled steering

-70 dB optical carrier suppression by two-beam coupling in photorefractive media

Optically smart active antenna arrays

Multibeam Spatially-Fed Antenna Arrays with Amplitude-Controlled Beam Steering