Electro-optic microwave-lightwave converters utilising quasi-phase-matching array of patch antennas with gap

Abstract

Proposed is a new electro-optic microwave-lightwave converter using an optical waveguide and a quasi-phase-matching (QPM) array of patch antennas embedded with a gap. A wireless microwave signal can be received and directly converted to a lightwave signal with low microwave distortion through optical modulation by use of the proposed device. Furthermore, by adopting the QPM structures, the transit-time effect is compensated for and conversion efficiency can be improved. In the experiment using a fabricated device, the conversion efficiency was improved by 10 dB.Introduction: Electro-optic (EO) microwave-lightwave converters are key devices in radio-over-fibre (ROF) systems [1]. EO microwave-lightwave converters can convert wireless microwave signals to lightwave signals through optical modulation adopting microwave antenna technology. Several EO microwave-lightwave converters using antenna-integrated electrodes have been reported [2,3]. The reported devices were composed of an antenna for wireless microwave receiving, an electrode for optical modulation, and their connection line. In these devices, the antenna and the electrode should be tuned precisely to obtain good resonance and impedance matching conditions at the designed frequency. However, some microwave distortion might be still induced through the coupling of them.We have proposed EO microwave-lightwave converters using patch antennas with a gap [4]. The devices are composed of patch antennas only and there is no other planar element on the substrate. They have a simple compact structure and were operated with no precise tuning and no external power supply. The microwave-lightwave conversion with extremely low distortion was demonstrated. However, the conversion efficiency was low owing to the limitation by the lightwave transit-time effect [5].In this Letter, we propose a new EO microwave-lightwave converter utilising an optical waveguide and a quasi-phase-matching (QPM) array of rectangular patch antennas with a narrow gap. The QPM array can compensate for the degradation of conversion efficiency by the transit-time effect. In the experiment, the conversion efficiency of the fabricated device was increased by 10 dB.

Optical Modulator Using Channel Optical Waveguides and Planar Patch-Antennas with Gaps

“…Based on the device configuration, it can be applied for intensity modulator using a Mach-Zehnder structure. The proposed device in an array structure can be used for the wireless Space-Division-Multiplexed (SDM) signal receiver by utilizing polarization-reversed structures [4], [5].…”

“…Electro-optic (EO) microwave-lightwave converters using antennas and EO modulators are promising devices. Several EO microwave-lightwave converters for wireless applications were reported using integrated structures [3] - [5]. These integrated EO converters are composed of planar antennas, planar modulation electrodes, and their connection lines.…”

Microstrip patch antennas feed to optical waveguides in electro-optic modulator for millimeter-wave radar system

“…A standing-wave millimeter-wave current is induced on surface of the microstrip patches. Displacement current is induced across the narrow-gaps due to current flow continuity along the microstrip patches [4,8].…”

Electro-optic wireless millimeter-wave-lightwave signal converters using planar Yagi-Uda array antennas coupled to resonant electrodes

“…We have proposed EO microwave-lightwave converters using an array of patch antennas embedded with a narrow gap [3]. These devices are potentially for converting from wireless signals to lightwave signals.…”