Active Integrated Filters for RF-Photonic Channelizers

Amr El Nagdi,Duncan L Macfarlane,Marc P Christensen,Ke Liu,Tim P Lafave,Viswanath Ramakrishna,Mieczyslaw Dabkowski,Louis R Hunt

doi:10.3390/s110201297

Abstract

A theoretical study of RF-photonic channelizers using four architectures formed by active integrated filters with tunable gains is presented. The integrated filters are enabled by two- and four-port nano-photonic couplers (NPCs). Lossless and three individual manufacturing cases with high transmission, high reflection, and symmetric couplers are assumed in the work. NPCs behavior is dependent upon the phenomenon of frustrated total internal reflection. Experimentally, photonic channelizers are fabricated in one single semiconductor chip on multi-quantum well epitaxial InP wafers using conventional microelectronics processing techniques. A state space modeling approach is used to derive the transfer functions and analyze the stability of these filters. The ability of adapting using the gains is demonstrated. Our simulation results indicate that the characteristic bandpass and notch filter responses of each structure are the basis of channelizer architectures, and optical gain may be used to adjust filter parameters to obtain a desired frequency magnitude response, especially in the range of 1–5 GHz for the chip with a coupler separation of ∼9 mm. Preliminarily, the measurement of spectral response shows enhancement of quality factor by using higher optical gains. The present compact active filters on an InP-based integrated photonic circuit hold the potential for a variety of channelizer applications. Compared to a pure RF channelizer, photonic channelizers may perform both channelization and down-conversion in an optical domain.

Highlights

RF photonics technology extending from coaxial cable replacement in RF communication links to signal processing in an optical domain, has recently led to higher efficiency, less complexity, and lower cost than conventional electronic systems, especially at high microwave and millimeter wave frequencies [1,2]
The experiments shown here are for a photonic channelizer configured with the coupler separation of ~500 m
The four proposed architectures vary in the structural layout and internal nano-photonic coupler formations

Summary

Introduction

RF photonics technology extending from coaxial cable replacement in RF communication links to signal processing in an optical domain, has recently led to higher efficiency, less complexity, and lower cost than conventional electronic systems, especially at high microwave and millimeter wave frequencies [1,2]. Channelization is a useful technique for simultaneously resolving multiple narrow frequency bands from a wideband RF spectrum used for communication and radar systems. Photonic channelization offers many advantages in processing ultra-wideband RF signals compared to pure electronic solutions, for example, large instantaneous bandwidth offered by photonics technology and cost saving of post-processing electronics as the channelization of broadband signals translating into intermediate frequencies [3]. The integral down-conversion technique using photonic channelizers occurs partly in the optical and partly in the electronic domain

Methods

Results

Conclusion