Naslov
Transmitting phased arrays of phase locked self-oscillating patch antennas

Autori
Bartolić, Juraj

Izvornik
Airforce Research Lab, AFB Hanscom, USA; Program: Window on Science

Vrsta, podvrsta
Ostale vrste radova, ostalo

Godina
1998

Ključne riječi
quasi-optical power combining; active arrays; active antenna; microwave oscillator; beam scanning

Sažetak
The quasi-optical power combining techniques allow power combining of a large number of solid state microwave oscillators in free-space. The advantages that the quasi-optical techniques offer in the microwave and millimeter wave fields has influenced the development of integrated antennas. Such transmitting antennas are usually built by integrating active elements such as Gunn and IMPATT, bipolar transistors, FETs or MMIC with a microstrip patch antenna. This technique we used in active self-oscillating antennas for communication and radar applications. In conventional active patch antennas the active one-port is integrated directly in the radiating element (rectangular or circular patch). In that case the patch serves both as a resonator and as a radiating element matched to the free-space characteristic impedance. Therefore, in the same time this structure represents an oscillator and antenna. Although this structure offers manufacturing simplicity, it is usually difficult to match packaged active devices with the patch structure. Also, the packaged active one-port introduces disturbance in current distribution on the patch and higher modes can be excited contributing to higher cross polarization levels. In order to overcome these problems, two modifications of the conventional rectangular patch antenna have been proposed in [1] and [2] have been used. Owning to the modifications of the rectangular patch, two types of linear arrays in E and H planes and planar arrays have been developed to demonstrate power combining and electronic beam scanning capabilities in X-band (9.5 GHz). By changing the oscillating frequency of individual oscillating patches, the phases of the signal radiated by those elements are changed. Changing the phase of the signal radiated by the elements of an antenna array changes its radiation pattern. In such arrays the oscillators have to be mutually injection locked to assure power generation at the same frequency. Two self-oscillating Gunn-patch antennas were coupled in E plane and placed 0.63 wavelength apart. By changing the dc bias voltage of one of the active patches a symmetrical beam scanning of +-20 degrees around broadside has been achieved. High combining efficiency has been obtained. The inter-element spacing for the H plane array was three quarters of wavelength in free-space. With the increased spacing the radiation coupling became weaker. To obtain stronger coupling a dielectric slab was placed in front of the array. By changing the dc bias of one of the patches a scanning from -18 to +12 degrees has been achieved. As in the case of E-plane array high combining efficiency has been obtained. Both active arrays showed VCO capabilities of electronic tuning or FM applications. Tuning range of about 300 MHz was achieved. The radiation patterns of the active arrays have been calculated by using the simple Green's function model and the IE3D electromagnetic simulator from Zeland Software, Inc. The simplicity of building such array antennas make them manufacturable and affordable, especially for microwave and millimeter-wave applications. References: [1] J. Bartolic, Z. Sipus, D. Bonefacic, E. Zentner, "Modified Rectangular Patch Radiator for Microstrip Active Antennas", Proceedings of the 24th European Microwave Conference, Volume 2, Cannes, France, September 5-8, 1994, pp. 1779-1784. [2] J. Bartolic, J. Sanford, Z. Sipus, D. Bonefacic, "Voltage Controlled Self-Oscillating Microstrip Patch Antenna", Proceedings of the 25th European Microwave Conference, Volume 1, Bologna, Italy, September 4-7, 1995, pp. 316-319.

Izvorni jezik
Engleski

Znanstvena područja
Elektrotehnika

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