A multilayer tunable ferroelectric antenna assembly that includes two superimposed substrate layers. A first substrate layer consists of a low dielectric material carrying on one face an electrically ground plane, and on its opposite face an electrically conductive patch serving as an active feeder-resonator. A second substrate includes a ferroelectric material having one face positioned on top of the feeder-resonator and carrying on the opposite face an electrically conductive patch acting as a director. The upper director patch is fed through capacitve coupling of energy from the feeder-resonator. Application of bias voltage between the director and the feeder-resonator changes the permittivity of the ferroelectric substrate, thereby causing a shift in resonance frequency. A radiation null, corresponding to energy absorption, could be tuned into the resonance frequency at which the antenna is previously exhibiting a radiation characteristic. This provides the antenna a means to behave either as a radiator or an absorber at particular frequency.

Tunable dual-band ferroelectric antenna

A family of FE dielectric-tuned antennas and a method for frequency tuning a wireless communications antenna are provided. The method comprises: forming a radiator; forming a dielectric with ferroelectric material proximate to the radiator; applying a voltage to the ferroelectric material; in response to applying the voltage, generating a dielectric constant; and, in response to the dielectric constant, communicating electromagnetic fields at a resonant frequency. Some aspects of the method further comprise: varying the applied voltage; and, modifying the resonant frequency in response to changes in the applied voltage. Modifying the resonant frequency includes forming an antenna with a variable operating frequency responsive to the applied voltage. Alternately stated, forming an antenna with a variable operating frequency includes forming an antenna with a predetermined fixed characteristic impedance, independent of the resonant frequency.

Tunable horn antenna

A new concept for phased arrays is proposed using a voltage-controlled ferroelectric lens. The ferroelectric lens concept uniquely incorporates bulk phase shifting-the array does not contain individual phase shifters-using ferroelectric material. This will reduce the number of phase shifters from (n/spl times/m) to (n+m), where n is the number of columns and m is the number of rows in a phased array. The number of phase shifter drivers and phase shifter controls is also significantly reduced by using row-column beam steering. Thus, the ferroelectric lens concept can potentially lead to low-cost phased arrays. This paper presents the ferroelectric lens concept, theoretical analysis and design, and experimental results. The results indicate that the ferroelectric lens concept is viable and sound. Various phased-array configurations using ferroelectric lens are included. A discussion on ferroelectric materials is included along with information on a US Department of Defense program to improve ferroelectric materials.

Voltage-controlled ferroelectric lens phased arrays

A tunable frequency selective surface (FSS) with beam steering capability is presented. The FSS is used as a transmitarray with a bandpass characteristic in Ku-band. The periodic sub-wavelength (λ0/25) unit-cells are composed of capacitive and inductive structures creating a bandpass for an incident wave. By patterning the capacitive elements on a screen-printed barium-strontium-titanate (BST) thick-film ceramic, the resonant frequency of the FSS can be tuned. This technology offers a simple and cost effective way for integrating varactors into the FSS and is particularly attractive for microwave circuits with a high varactor density. A prototype is fabricated including two capacitive layers with an overall size of 40 mm × 40 mm. Each layer includes a total of 1600 integrated BST varactors that are fabricated by using a patterning and metallization process. A transmitted wave passing through the FSS will experience a phase shift, which can be tuned by tuning the passband. This allows steering the transmitted wave to a certain direction by applying a phase gradient along the FSS interface. A phase shift range of 360° can be covered by cascading several FSS panels. The prototyped tunable FSS demonstrates the feasibility of the proposed technology and its potential for beam steering.

Beam Steering Transmitarray Using Tunable Frequency Selective Surface With Integrated Ferroelectric Varactors

In this communication, a novel filtering antenna is proposed by utilizing active frequency selective surface (FSS), which can simultaneously achieve filtering and beam steering function. The FSS unit is composed of a metallic rectangular ring and a patch, with a pair of microwave varactor diodes inserted in between along incident electric field polarization direction. Transmission phase of the emitted wave can be tuned by changing the bias voltage applied to the varactor diodes. Through different configurations of the bias voltages, we can obtain the gradient phase distribution of the emitted wave along E- and H-plane. This active FSS is then fabricated and utilized as a radome above a conventional horn antenna to demonstrate its ability of steering the beam radiated from the horn. The experimental results agree well with the simulated ones, which show that the horn antenna with the active FSS can realize beam steering in both E- and H-plane in a range of ±30° at 5.3 GHz with a bandwidth of 180 MHz.

A Beam Steering Horn Antenna Using Active Frequency Selective Surface

Phased array antennas can steer transmitted and received signals without mechanically rotating the antenna. Each radiating element of a phased array is normally connected to a phase shifter, which determines the phase of the signal at each element to form a beam at the desired angle. The most commonly used phase shifters are ferrite and diode phase shifters. Phase shifters using ferroelectric materials have been proposed previously. A typical phased array may have several thousand elements and is very expensive. Therefore, reducing the cost and complexity of the phase shifters and the phase shifter controls is an important consideration in the design of phased arrays. The phased array described uniquely incorporates bulk phase shifting, the array does not contain individual phase shifting, using a ferroelectric material along with simpler phase shift control. Bulk phase shifting using diodes has been proposed and developed in the Radant lens. The lens described uses a voltage controlled ferroelectric, which introduces an analog phase shift rather than a digital phase shift as in the Radant lens. The ferroelectric lens has further advantages of smaller lens thickness, higher power handling, simpler beam steering controls, and it uses less power to control the phase shift compared to the Radant lens. Thus, it can potentially lead to low cost phased arrays.

D.P. Patel

Papers

Voltage controlled ferroelectric lens phased arrays