A two-dimensional coupled oscillator beam-steering array without phase-shifters is presented for several design considerations. The 20 GHz 4/spl times/4 array has a triple-layer tile architecture. Mutually coupled oscillators on the bottom layer generate steered phase by edge-element tuning, which drives a 4/spl times/4 microstrip patch antenna array located on the top layer. The circuit measures 1.2 inch long and 1.2 inch wide. Near-field and far-field measurement results show that the main beam of the antenna array can be steered off broadside from -26/spl deg/ to +30/spl deg/ in azimuth and from -24/spl deg/ to +30/spl deg/ in elevation. A frequency multiplication technique is employed to increase the array beam-steering range.

A design for a two-dimensional coupled oscillator beam-steering antenna array

Design, fabrication, and test of a 25-element planar coupled oscillator based phased array is described. The array operates at S-band and is shown to produce an agile beam which is steerable via adjustment of the perimeter oscillator tuning biases only. A phase diagnostic system is described which displays the aperture phase distribution during the far field measurements of the radiated beam. Measured results are presented both with and without the diagnostic system present. Without the diagnostic system, the beam pointing was achieved by setting the perimeter oscillator biases to be values previously used in the measurements with the diagnostic system present. The far field was then measured without the benefit of a knowledge of the aperture phase distribution. Finally, the results of far field measurements are described in which the beam position was incremented from a position previously measured with the diagnostic system in place to a new position by incrementing the perimeter oscillator biases by a fixed amount.

A 5-by-5 element coupled oscillator-based phased array

Arrays of voltage-controlled oscillators can be coupled by means of a network so as to be mutually injection locked and thus oscillate as an ensemble. This ensemble may be used to excite the elements of a phased array antenna in such a manner as to radiate an agile beam. Design of the coupling network requires attention to three key parameters: the inter-oscillator coupling strength, the network bandwidth, and the oscillator loading. These parameters can be related to the network admittance matrix elements, which, in turn, are related to the lumped element values. This provides convenient formulas for use in designing networks, which provide the necessary values of the above three key design parameters.

On the design of coupling networks for coupled oscillator arrays

Phased arrays have been proposed in which a two-dimensional array of voltage-controlled oscillators coupled to nearest neighbors provides excitations for the radiating elements which are properly phased to result in a steerable radiated beam. These arrays have been arranged on a rectangular lattice and the beam is steered by tuning the oscillators along the four edges of the array. Proposed here are similar arrays in which the oscillators are coupled on a triangular lattice or a hexagonal lattice and provide excitations for radiating elements similarly disposed in a planar triangular array. Beam steering is accomplished by tuning the oscillators along the three edges of the array. The dynamic behavior of the arrays is studied via a continuum model and the results compared with those of a full nonlinear discrete analysis and a linearized discrete model.

Phased arrays based on oscillators coupled on triangular and hexagonal lattices

In this paper, a two-dimensional mutually coupled oscillator array is studied for the application of a beam-scanning and polarization-agile antenna array. In the design of antenna array, a two-dimensional oscillator array is implemented in x-y plane, the polarization agility is provided by one dimension (or y-direction) and the other dimension (or x-direction) is for beam scanning. By properly tuning the free-running frequencies of these oscillators, the array radiation direction can be scanned at the selected polarization states including linearly polarized, left-hand and right-hand circularly polarized states. The maximal phase difference of /spl plusmn/180/spl deg/ between coupled oscillating signals is acquired by utilizing their second-harmonic signals. This then gives well-defined phase differences among oscillators for beam scanning in addition to the required quadrature phase difference for circular polarization. The performances of polarization agility and beam scanning for a four-element antenna array are verified experimentally and shown to have the potential for adaptive antenna array applications.

Shigeji Nogi

Papers

Transmission-Line Coupling of Active Microstrip Antennas for One- and Two-Dimensional Phased Arrays