Several linearly-polarized and circularly-polarized transmit-arrays are designed and demonstrated in the 60-GHz band. These arrays have a fairly simple structure with three metal layers and are fabricated with a standard printed-circuit board technology. The simulation method is based on an electromagnetic model of the focal source and the unit-cells, associated to an analytical modeling of the full structure. A theoretical analysis is presented for the optimization of the power budget with respect to the F/D ratio. Several prototypes are designed and characterized in V-band. The experimental results are in very good agreement with the simulations and demonstrate very satisfactory characteristics. Power efficiencies of 50-61% are reached with a 1-dB gain bandwidth up to 7%, and low cross-polarization level.

Wideband Low-Loss Linear and Circular Polarization Transmit-Arrays in V-Band

An electronically reconfigurable unit cell with 1-bit phase quantization (0°/180°) is proposed for X-band linear polarization transmit arrays. It consists of two rectangular patch antennas loaded by U- and O-slots and connected by a metallized via-hole. The transmission phase is controlled using two p-i-n diode switches integrated in the O-slot. An equivalent lumped-element circuit model is implemented and compared successfully to full-wave simulations. The numerical results are validated experimentally using an ad-hoc waveguide simulator. The prototype exhibits low insertion loss (1.8 dB) with the same level for both phase states, a broad 3-dB transmission bandwidth (14.7%), a 1-dB compression point of 13-15 dBm, and a gain of 5 dBi at 9.75 GHz. The performance and simplicity of the proposed unit cell make it attractive to build electronically steerable transmit arrays in X-band.

1-Bit Reconfigurable Unit Cell Based on PIN Diodes for Transmit-Array Applications in $X$ -Band

A planar array of passive lens elements can be phased to approximate the effect of a curved dielectric lens. The rotational orientation of each element can provide the required phase shift for circular polarization. The array elements must be designed so that the hand of circular polarization changes as the electromagnetic wave passes through the lens. An element is presented that is based on an aperture-coupled microstrip patch antenna, and two lenses are designed. Each lens has a diameter of 254 mm and contains 349 elements. The elements have identical dimensions but the rotational orientation of each element is selected to provide a specific lens function. The first lens is designed to collimate radiation from a feed horn into a beam pointing 20° from broadside. At 12.9 GHz the aperture efficiency is 48%. The second lens acts as a Wollaston-type prism. It splits an incident wave according to its circular polarization components.

Lenses for Circular Polarization Using Planar Arrays of Rotated Passive Elements

The mutual coupling effects between a finite phased array of dipoles and its feed network are analyzed. The feed network is typically a corporate feed consisting of split-tee power dividers cascading to form a certain power distribution over the aperture. A simple iterative approach is used to solve the interaction between elements and feed. The radiation of a finite dipole array are first found for a given voltage excitation. These radiation impedances are then used as loads for the feed network, and the n+1 port network problem is analyzed. Due to the interaction between the feed network and dipoles, the antenna parameters such as mismatch, antenna pattern, and gain are all affected. These effects can be determined from the analysis of the network representation. Numerical results for a typical phased array with a corporate feed show that the resultant VSWR of the feed pattern degradation is due to the mutual coupling effects. >

Analysis of mutual coupling between a finite phased array of dipoles and its feed network

We designed a reconfigurable dual-band reflection amplifier with operation frequency bands over 18 GHz and/or 24 GHz This one-port amplifier boosts the reflected signal over either of these two frequency bands or both as a dual-band reflection amplifier The amplifier circuit consists of an FET transistor and two p-i-n diodes, which act as switches to form a reconfigurable system The measured reflection gains at single 18 GHz and 24 GHz frequency bands are 176 dB and 1675 dB, respectively The dual-band operation frequency shows 112 dB and 15 dB gain at 18 GHz and 24 GHz, respectively Then, we realized a bidirectional amplifier using a dual-band −3 dB 90° branch line coupler integrated with two of the proposed reconfigurable reflection amplifiers This bidirectional amplifier is a two-port bilateral amplifier The measured reflection gains show at least 10 dB transmission gains ( ${S} _{21}$ and ${S} _{12}$ ) at operation frequency bands The proposed reconfigurable bidirectional amplifier is then used in a dual-band Van Atta array The proposed active retrodirective system outperformed passive Van Atta array by 5 dB gain with only half the number of antenna elements Each component is investigated analytically and analyzed by advanced design system Fabricated circuits are measured and show good agreement with simulations

Reconfigurable Dual-Band Bidirectional Reflection Amplifier With Applications in Van Atta Array

An equivalent network representation of a feedthrough lens array, which takes into account mutual coupling between the array elements, is presented. The model is employed to predict performance characteristics, which include element mismatch, peak voltage loading of the phase shifters, element currents, and transmitted power. Both analog and digital phase shifters are treated in the analysis. It is shown that, irrespective of the type of phase shifter, the mismatch from element to element at a fixed scan angle is not identical. This variation is explained in terms of the multiple reflections that take place between the two surfaces of the lens. Further, as a function of scan angle, the element mismatch for a digitally phased array lens does not vary in a smooth manner but exhibits a decided ripple.

Analysis of phased array lenses

A retrodirective satellite antenna for a broad bandwidth, satellite-to-ground data transmission link, is described. An information-collecting satellite which transmits its data in the direction of the ground receiver upon command, is considered. The satellite antenna described for this system is an active retrodirective antenna which utilizes the beam-forming characteristics of a phasing matrix. A signal from the ground station is received on a particular beam port of the matrix which corresponds to a particular beam-pointing direction. Control circuitry in the satellite activates a switching matrix and a transmitter so that the data-carrying signal is transmitted in the same direction from which the satellite is interrogated. Other retrodirective techniques in addition to the phasing-matrix antenna are evaluated in terms of their relative merit. The systems considered include the active Van Atta array, the automatic three-dimensional electronic scanning, antenna (ATHESA), the Luneberg lens and various other antenna array techniques.

L. Schwartzman

Papers

Analysis of phased array lenses

A satellite data transmission antenna

Maximum efficiency for cylindrically disposed multiple-beam antenna arrays