Nm Netsanet Tessema

Cyclic additional optical true time delay for microwave beam steering with spectral filtering

Optical true time delay (OTTD) is an attractive way to realize microwave beam steering (MBS) due to its inherent features of broadband, low-loss, and compactness. In this Letter, we propose a novel OTTD approach named cyclic additional optical true time delay (CAO-TTD). It applies additional integer delays of the microwave carrier frequency to achieve spectral filtering but without disturbing the spatial filtering (beam steering). Based on such concept, a broadband MBS scheme for high-capacity wireless communication is proposed, which allows the tuning of both spectral filtering and spatial filtering. The experimental results match well with the theoretical analysis.

Integrated remotely tunable optical delay line for millimeter-wave beam steering fabricated in an InP generic foundry

A compact and fabrication-tolerant integrated remotely tunable optical delay line is proposed for millimeter-wave beam steering and is fabricated in an InP generic foundry. The proposed delay line is based on a spectrally cyclic-arrayed waveguide grating feedback loop. Its major features include the tolerant architecture with reduced chip size, and bi-directional operation with simplified remote tuning. Moreover, its cyclic feature guarantees further cascaded operations either for 2D radio beam steering or for high-resolution delay generation. The experimental results show less than 6.5-dB insertion loss of the integrated delay line. Five different delays from 0 to 71.6 ps are generated with less than 0.67-ps delay errors.

Optical wireless data transfer enabled by a cascaded acceptance optical receiver fabricated in an InP membrane platform

Utilizing an InP membrane based cascaded acceptance optical receiver (CAO-Rx), we demonstrate 17.4Gbps optical wireless transmission in C-band. By separating light collection and opto-electrical conversion, CAO-Rx provides better optical efficiency and electrical bandwidth simultaneously.

A Tunable Si3N4 Integrated True Time Delay Circuit for Optically-Controlled K-Band Radio Beamformer in Satellite Communication

In this paper we present the design, realization, and experimental characterization of a photonic integrated true time delay circuit on a CMOS-compatible Si3N4 platform. The true time delay circuit consists of an optical side band filter for single side band modulation and an optical ring resonator for broadband time delay. Two methods of optical delay tuning are investigated: 1) optical wavelength and 2) thermo-optic delay tuning. The wavelength controlled tuning enables a large delay tuning range and can be done remotely from a distant location. The close to a linear phase measurements can be used for full beam-scanning of radio signals with frequencies in the 20 GHz band. The thermal control results in a 5 GHz RF delay bandwidth. A proof-of-concept 2 × 1 beamforming is demonstrated in the 20 GHz band. The design presented here can be employed to realize multi-beams for multi-users serviced by multiple satellites.

38-GHz millimeter wave beam steered fiber wireless systems for 5G indoor coverage: architectures, devices, and links

Millimeter wave (mm-wave) beam steering is a key technique for the next generation (5G) wireless communication. The 28 and 38-GHz bands are widely considered as the candidates for 5G. In the context of indoor coverage, fiber-wireless systems with multiple simplified remote antenna sites are attractive to avoid the indoor coverage problem caused by the high wall penetration loss of mm-wave signals. To allow enough antenna gain at the mm-wave bands, radio beam steering (and beamforming) is desired. Combining fiber-wireless system with remotely controlled photonic mm-wave beam steering can bring significant advances in terms of energy efficiency and cost. In this paper, we explore two kinds of indoor fiber-wireless network architectures for such mm-wave beam steering. Then, we discuss and investigate the key enabling device, which is an arrayed waveguide grating feedback loop (AWG-loop). Based on the AWG-loop, we further design two fiber-wireless links to accommodate the two network architectures. Both links with bit rates from 50 Mb/s to 8 Gb/s per spatial channel are experimentally demonstrated with a 38-GHz carrier frequency. The advanced reversely modulated optical transmitter and half-cycled 16 quadrature amplitude modulation (QAM-16) are employed to realize a simplified mm-wave beam steered fiber-wireless link with the record-breaking 16-b/s/Hz (4 spatial channels

A Si3N4 PIC for optically controlled 2D radio beamforming in satellite communications

\times 4

A photonics-assisted beamformer for K-band RF antenna arrays

bits/s/Hz) spatial-spectral efficiency in its kind.

Radio beam-steering via tunable Si3N4 optical delays for multi-Gbps K-band satellite communication

We designed and fabricated a Silicon Nitride (Si3N4) photonic integrated circuit targeting wideband two-dimensional radio beamforming from 20-40 GHz for satellite communications. Continuous true time delay tunability is achieved by using thermo-optic phase shifters in a 2-port optical ring resonator. Scanning angles up to 20° and true time delay bandwidth up to 14 GHz are realized while tuning into the anti-resonance response of the ring resonator. An optical side-band filter using a double-ring loaded Mach-Zehnder interferometer with an FSR of 0.48 nm is designed for a single side band operation. The fabricated photonic integrated circuit is a 4-input / 4-output beamformer for a 2-by-2 focal plane antenna array. It is the first PIC beamformer circuit on Si3N4 designed for operation in the 20-40 GHz band.

Beam steered millimeter-wave fiber-wireless system for 5G indoor coverage

We present an experimental demonstration of radio beamforming using an optical chip for application in K-band satellite communication. Via coherent combination of four RF channels, close to 12 dB beamforming gain is obtained. As a result, the transmission capacity is enhanced from 8-QAM, 5.81 Gbps to 32-QAM, 9.68 Gbps of multi-carrier data. For 4 channel beamforming, error-free performance (BER<1E-12) is obtained with 8-QAM data. The tuning of the optical beamforming chip is done electronically via a software interface by a computer.

Compact and tunable AWG-based true-time delays for multi-Gbps radio beamformer

We realized a compact Silicon Nitride chip for optically reconfigurable time delays for K-band (17-22 GHz) radio satellite terminals beam-steering. Using 16-QAM 64-OFDM subcarriers we achieved 10 Gbps transmission capacity.