Recently, the desired very high throughput of 5G wireless networks drives millimeter-wave (mm-wave) communication into practical applications. A phased array technique is required to increase the effective antenna aperture at mm-wave frequency. Integrated solutions of beamforming/beam steering are extremely attractive for practical implementations. After a discussion on the basic principles of radio beam steering, we review and explore the recent advanced integration techniques of silicon-based electronic integrated circuits (EICs), photonic integrated circuits (PICs), and antenna-on-chip (AoC). For EIC, the latest advanced designs of on-chip true time delay (TTD) are explored. Even with such advances, the fundamental loss of a silicon-based EIC still exists, which can be solved by advanced PIC solutions with ultra-broad bandwidth and low loss. Advanced PIC designs for mm-wave beam steering are then reviewed with emphasis on an optical TTD. Different from the mature silicon-based EIC, the photonic integration technology for PIC is still under development. In this paper, we review and explore the potential photonic integration platforms and discuss how a monolithic integration based on photonic membranes fits the photonic mm-wave beam steering application, especially for the ease of EIC and PIC integration on a single chip. To combine EIC, for its accurate and mature fabrication techniques, with PIC, for its ultra-broad bandwidth and low loss, a hierarchical mm-wave beam steering chip with large-array Manuscript delays realized in PIC and sub-array delays realized in EIC can be a future-proof solution. Moreover, the antenna units can be further integrated on such a chip using AoC techniques. Among the mentioned techniques, the integration trends on device and system levels are discussed extensively.Index Terms-5G, millimeter-wave, beam steering, true-timedelay, phase shifter, antenna-on-chip, photonic radio beam steering, broadband beamforming, phase control units.
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We report a novel optical wireless communication (OWC) system solution that supports multi-Gbps (Gigabit-per-second) capacity for indoors. Narrow beams, termed as pencil beams, are directed to wireless users using a tunable laser and a passive diffractive optical element. This enables a wide coverage of ultra-high-capacity communication links to serve multiple network users simultaneously. Experimental results demonstrating data rates of up to 10 Gbps, with on-off keying modulation format, over a distance of more than 2.5 m, are reported. Error-free links beam-steered over a total wavelength range of 130 nm, with steering angle of 17.16°, have been achieved. This system is proposed for short-range OWC and is promising for seamless integration in in-building optical networks.
The spatial filtering in an orthogonal frequency division multiplexing (OFDM) radio-over-fiber network is proposed to boost its capacity using broadband optical true time delay enabled microwave beam steering. The observed suppression ratio of the spatial filtering is 19.4 dB. The optical delivery and directional wireless transmission of 3.975 Gb/s OFDM data on a 19-GHz microwave carrier is studied. The observed beam directing-induced bit error ratio improvement is more than four orders of magnitude.Index Terms-Spatial filtering, optical true time delay, microwave beam steering, radio over fiber.
A hybrid fiber-wireless in-home network is proposed to support high-speed multiple input and multiple output (MIMO) orthogonal frequency division multiplexing systems operating at millimeter wave (mm-wave) band by employing optical heterodyne (OH) and polarization multiplexing (PolMux). OH enables the optical generation of mm-wave signals without the intrinsic frequency limitation of electrical local oscillators. Moreover, the frequency agility can be provided by tuning the optical wavelength in an OH system. PolMux explores two orthogonal polarizations at the same optical wavelength to satisfy the wireless MIMO service with low additional cost. Enabled by these techniques, the fiber transmission (1 km) and wireless delivery (1 m) of 61.3-Gbps data at 40-GHz mm-wave are successfully demonstrated. To the best of our knowledge, a record spectral efficiency of 6.82 bit/s/Hz is achieved in such kind of systems.Index Terms-Hybrid fiber-wireless networks, in-home networks, millimeter wave, multiple input and multiple output orthogonal frequency division multiplexing (MIMO-OFDM), optical heterodyne, polarization multiplexing (PolMux).
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