This paper provide a review of the active integrated antenna (AIA) technologies. After a brief introduction on the definition and some historical remarks, the paper concentrates on the research effort on the past decades or so. The AlAs are reviewed in its various functions. First, an oscillator-type AIA is presented, followed by very interesting aspects of coupled oscillator arrays for phase control. Use of an AIA concept for efficient RF front ends is described with examples on high-power amplifier AlAs. Next, a phase-conjugation-based retrodirective array is reviewed. Finally, AIA systems for receiving, transmitting, and duplexing are reviewed.

Active integrated antennas

An FET source has been integrated with a microstrip patch antenna to form an active radiating module. The patch antenna serves both as a radiating element and a resonator in the feedback loop for the FET oscillator. Power output of 17mW was achieved at 5.7 GHz.

Active radiating element using FET source integrated with microstrip patch antenna

A novel miniaturized cavity-backed composite slot loop antenna (CBCSLA) with low profile and omnidirectional radiation similar to a short dipole is presented. The antenna displays vertical polarization while having less than lambda/100 dimension in height. The geometry of the antenna is inspired from a small magnetic loop which is realized using a slot configuration on metallic ground. Since a small slot loop antenna cannot be impedance matched, a composite geometry is devised that acts like as a small slot loop and can easily be impedance matched using this configuration. The diameter of the CBCSLA can be made as small as lambda/10 or smaller. The feeding mechanism is designed in a manner to create a circumferentially-constant current distribution around the composite loop while effectively matching to a 50 Omega coaxial feed from the antenna center. Additional methods are discussed to further enhance the bandwidth and achieve a dual-band response. The antennas are designed, fabricated, and measured. It is shown that despite their small lateral dimension and extremely small height, the miniaturized cavity-backed slot loop features extremely well input impedance match, uniform radiation pattern, low cross-polarization levels and expected gain.

Low Profile Miniaturized Planar Antenna With Omnidirectional Vertically Polarized Radiation

A slot-excited hemispherical dielectric resonator antenna backed by a rectangular cavity is studied theoretically and experimentally. The magnetic-type dyadic Green's function for the rectangular cavity is derived using the mode-matching method. An integral equation for the equivalent magnetic current is obtained by enforcing the boundary condition across the slot. The moment method with the Galerkin's procedure is then used to find the magnetic current in the slot and, hence, the input impedance of the antenna. Measurements were carried out to verify the theory and good agreement is obtained. The effects of the slot inclination angle, of the slot offset, and of the cavity size on the input impedance are discussed.

Theory and experiment of the cavity-backed slot-excited dielectric resonator antenna

The hemispherical cavity-backed slot antenna is studied theoretically and experimentally. The exact magnetic field Green's function of the cavity is derived rigorously and expressed in a form convenient for numerical computation. The moment method is used to find the equivalent magnetic current in the slot and, hence, the input impedance of the antenna configuration. The effects of the cavity size, of the slot length, and of the slot offset on the input impedance are studied and very good agreement between theory and experiment is obtained. The variation of the magnetic current around the slot and cavity resonances are discussed. Comparisons between the rigorous solution and the single-mode theory are given and the limitation of the single-mode theory is discussed.

Theory and experiment of the hemispherical cavity-backed slot antenna

Active antenna elements have been fabricated using Gunn diodes and microstrip patch antennas. The power outputs from two of these elements have been successfully combined in space. Frequency coherency was achieved by injection locking using either the spatial locking technique or the mutual coupling locking technique.

Spatial power combining using active microstrip patch antennas

The authors study the input impedance of a cylindrical cavity-backed slot antenna based on mode matching and the complex Poynting theorem. Two cavity-backed slot antennas were fabricated to verify the theory. The numerical results agree very well with measurements. Two resonant frequencies were found from the input impedance. One resonant frequency is attributed to the rectangular slot and the other is due to the cavity. The slot length controls the first resonant frequency and has a much stronger effect on the input impedance at the antenna operating frequency as compared with the cavity length. >

Theoretical and experimental study of the input impedance of the cylindrical cavity-backed rectangular slot antennas

Circuits of rectangular waveguides coupled to a cylindrical cavity have been studied. Two types of circuits were developed: a high-power four-way power divider/combiner with less than 0.5 dB insertion loss over a 20 percent bandwidth and a high-power four-port cross-over circuit with less than 0.7 dB insertion loss and 20 dB isolation at X-band. To demonstrate the feasibility of the first circuit, a power combiner was built by connecting four Gunn oscillators to the four rectangular waveguide ports of the radial waveguide. A power combining efficiency of over 70 percent was achieved at X-band. The second circuit was used to feed a dual-polarization cross-slot antenna backed by a cylindrical cavity.

Applications of a high power four-way power divider and combiner and a cross-over circuit

The input impedance of a cylindrical cavity-backed slot antenna has been derived based on the mode matching method and the complex Poynting theorem. Two cavity-backed slot antennas were fabricated to verify the theory. Numerical results agree very well with measurements. It is pointed out that the results should have many applications in conformal antennas and arrays. >

Input impedance of the slot antennas backed by cylindrical cavity

Integrated circuit active arrays and spatial power combiners using aperture coupled patch antennas have been developed. Results from a prototype element and a two-element combiner are very encouraging. Methods for achieving phase coherency have been developed.

Kenneth A. Hummer

Papers

Spatial power combining using active microstrip patch antennas

Theoretical and experimental study of the input impedance of the cylindrical cavity-backed rectangular slot antennas

Applications of a high power four-way power divider and combiner and a cross-over circuit

Input impedance of the slot antennas backed by cylindrical cavity

Integrated Circuit Active Arrays And Spatial Power Combiners Using Aperture Coupled Patch Antennas