Millimeter-wave receivers for wireless communications
Date
2016
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Publisher
University of Delaware
Abstract
The modern communications environment is becoming an increasingly crowded place, resulting in rapidly increasing demands on current technology. Military and civilian operations require the ability to locate and decode all communication signals in the environment. However, developments in RADAR (RAdio Detection And Ranging) and communications technology are making it harder to effectively identify and maintain bandwidth usage for everyone. Millimeter waves—waves measured between one millimeter to one centimeter in wavelength—have only recently been explored as a new technology to replace the augment receiver architectures. These small wavelengths introduce many engineering challenges, such as: large atmospheric losses, poor sensitivity, and expensive electronic equipment. With growing developments in Microwave Photonics, low-noise RF amplifiers and high-speed modulators have demonstrated the ability to design RF communication links in the millimeter wave regime to counter such problems. However, despite these developments, toward a cost-effective, spatial division multiplexing (SDM) receiver concept has not proved capable of being implemented as part of the next generation 5G wireless network infrastructure.
To this end, we present a novel receiver architecture utilizing an optically addressed phased-array millimeter wave receiver based on optical-upconversion and signal recovery. This receiver is capable of geolocation and spatial multiplexing of multiple Tunable Optically Paired Source (TOPS) communication signals in its scene. Operating at 35 GHz, the receiver up-converts the received RF onto an optical sideband, which, to our advantage, contains all of the frequency, amplitude, and phase information of the received signals. Subsequent optical processing allows routing of the sideband to a free space detector port. Photomixing a coherent optical local oscillator (LO) with the optical sideband performs heterodyne down-conversion to an Intermediate Frequency (IF) where we are able to spatially resolve each signal individually to recover complex modulated formats transmitted by our TOPS generators.
In this thesis, we describe the unique advantages of our receiver concept to allow for frequency re-use as well as cell sectoring methods to increase the overall data capacity bandwidth. Primarily, the use of a distrusted aperture array enables high resolution imaging, limited only by the diffraction efficiency set at the antenna array. Thus, angle-of-arrival (AoA) capabilities help deduce the position of each signal and the data it contains. Unlike IR or visible wavelengths, millimeter waves have the unique ability to penetrate dust, smoke, cloud coverage, and thin fabrics such as clothing. As such, millimeter wave receivers have the capability of achieving high signal-to-noise ratios (SNR) in obscured environments compared to their counterparts.
This optically addressed communication receiver offers vast advantages over current communication receiver architectures in place today. This approach has the potential to operate as the next generation communication receiver for 5G wireless. In addition, this receiver concept appeals to many security and defense applications requiring secure communications and unwanted signal avoidance.