A Dual-Linearly-Polarized MEMS-Reconfigurable Antenna for Narrowband MIMO Communication Systems

The design and characterization is described of a compact dual-linearly-polarized reconfigurable 2-port antenna. The antenna can operate in two different selectable linear polarization bases, thus being capable of reconfiguring/rotating its polarization base from vertical/horizontal $(0^{circ}/90^{circ})$, to slant $pm 45^{circ}$. The antenna has been implemented on a Quartz substrate, and uses monolithically integrated micro-electromechanical (MEM) switches to select between the two aforementioned polarization bases. The antenna operates at 3.8 GHz and presents a fractional bandwidth of 1.7%. The interest of the proposed antenna is two-fold. First, in LOS scenarios, the antenna enables polarization tracking in polarization-sensitive communication schemes. Second, there are the gains of using it in a multiple-input multiple-output (MIMO) communication system employing orthogonal space-time block codes (OSTBC) to improve the diversity order/gain of the system in NLOS conditions. These benefits were verified through channel measurements conducted in LOS and NLOS propagation scenarios. Despite the simplicity of the antenna, the achievable polarization matching gains (in LOS scenarios) and diversity gains (in NLOS scenarios) are remarkable. These gains come at no expenses of introducing additional receive ports to the system (increasing the number of Radio-Frequency (RF) transceivers), rather as a result of the reconfigurable capabilities of the proposed antenna.      

Nonreciprocal Polarization Converter Consisting of Asymmetric Waveguide With Magnetooptic Cladding: Theory and Simulation

A nonreciprocal polarization converter compatible with InP-based photonic integrated circuits is proposed. The device consists of an asymmetric InGaAsP waveguide combined with a ferrimagnetic cerium-substituted yttrium iron garnet layer. It makes use of the nonreciprocal conversion of the polarization state in the waveguide. A nonreciprocal TE–TM conversion efficiency of 93% at 1.55 $mu{hbox {m}}$ wavelength can be obtained with a device length of 0.27 mm.      

Design of a Compact Photonic-Crystal-Based Polarization Channel Drop Filter

We design a compact photonic-crystal-based polarization channel drop filter (PhC-PCDF) using the triangular lattice air holes PhC, which would be an essential device in future integrated polarization and wavelength-division-multiplexed (PWDM) system. The PhC-PCDF contains two line waveguides and a resonating system between them. In the line waveguide, the transverse-electric (TE) polarization and the transverse-magnetic (TM) are guided by photonic bandgap effect and total internal reflection effect, respectively. By resonating the system, a narrow bandwidth TE polarization is dropped from one waveguide to the other, leaving other components of the PWDM signal without any disturbance. The transmission efficiency for TM polarization and TE polarization are both over 95%. The quality factor of the TE PCDF is about 1800. The whole size of the designed PhC-PCDF can be $20atimes 12a$.      

Cost Effective Silica‐Based 100 G DP‐QPSK Coherent Receiver

We present a cost‐effective dual polarization quadrature phase‐shift coherent receiver module using a silica planar lightwave circuit (PLC) hybrid assembly. Two polarization beam splitters and two 90° optical hybrids are monolithically integrated in one silica PLC chip with an index contrast of 2%‐Δ. Two four‐channel spot‐size converter integrated waveguide‐photodetector (PD) arrays are bonded on PD carriers for transverse‐electric/transverse‐magnetic polarization, and butt‐coupled to a polished facet of the PLC using a simple chip‐to‐chip bonding method. Instead of a ceramic sub‐mount, a low‐cost printed circuit board is applied in the module. A stepped CuW block is used to dissipate the heat generated from trans‐impedance amplifiers and to vertically align RF transmission lines. The fabricated coherent receiver shows a 3‐dB bandwidth of 26 GHz and a common mode rejection ratio of 16 dB at 22 GHz for a local oscillator optical input. A bit error rate of is achieved at a 112‐Gbps back‐to‐back transmission with off‐line digital signal processing.     

Compact $$3\times 3$$ wavelength routing for photonic integrated circuits

Photonic integrated circuits are the future of optical communication networks. The demand for high bandwidth has added a remarkable increase in the capacity of transmission and routing techniques for optical networks. With massive growth in photonic integrated circuits, communication within them (PIC) is an area that needs to be explored and addressed. The signal path between different components in the circuit has to be established for an optimal path with high transmission efficiency. This could be achieved using routers. With this being the intention, this paper proceeds with a design of two \(3\,\times \,3\) optical passive wavelength routers using photonic crystal ring resonators. The designed router connects three transmitters to three receivers with desired characteristics such as low crosstalk, less propagation delay, low insertion loss and can be easily fabricated because of its less complex design. The routers are designed to operate in third transmission window wavelength with basic building blocks of \(1\,\times \,2\) routers. The designed layout of routers exhibits good performance which can be used for all optical communication networks and has a good technological compatibility for chip level integration in PIC. The layout is simulated using finite difference time domain and plane wave expansion methods.     

Compact Polarization Mode Converter Monolithically Integrated Within a Semiconductor Laser

The design and realization of a short, passive, single-section waveguide polarization converter monolithically integrated within a Fabry–Perot ridge waveguide laser is reported. The device is fabricated on an unstrained GaAs-AlGaAs double quantum well heterostructure. A predominantly transverse magnetic polarized optical output from the converter facet of greater than 80% is demonstrated for a converter length of 20 $mu$m at an operating wavelength of 867 nm.      

Diplexer With Integrated Filters and Photodetector in Ge–Si Using $Gamma-{X}$ and $Gamma-{M}$ Directions in a Grating Coupler

We demonstrate a central-office-type diplexer in which the filter and photodetector are monolithically integrated on a silicon-on-insulator substrate. The photonic integrated circuit receives a 1577-nm signal from an external laser and sends it to the fiber link using a two-dimensional grating coupler. The same grating coupler receives a 1270-nm signal from the fiber link and sends it to a monolithically integrated germanium photodetector using a polarization-diversity scheme to achieve polarization independence. The grating coupler is novel in that both the $Gamma-{X}$ and $Gamma-{M}$ directions are employed. This allows the grating coupler to couple both the 1577- and 1270-nm wavelengths with a small fiber tilt angle and hence have low polarization-dependent loss.      

Fast Adaptive Polarization and PDL Tracking in a Real-Time FPGA-Based Coherent PolDM-QPSK Receiver

Fast polarization changes of 40 krad/s and 6-dB polarization-dependent loss (PDL) are tracked in a 2.8-Gb/s real-time coherent quadrature phase-shift keying receiver. The tolerance against fast polarization changes and PDL is measured for different polarization control time constants. The sensitivity penalty of the receiver at a polarization change speed of 40 krad/s is 0.7 dB at bit-error rate (BER) of $1times 10^{-3}$, with a BER floor of $6.1times 10^{-7}$. With an additional PDL of 6 dB, these figures become 1.7 dB and $9.6times 10^{-6}$, respectively.      

Study of the Polarization Strategy for Electron Cyclotron Heating Systems on HL-2M

As important components integrated in transmission lines of electron cyclotron heating systems, polarizers are mainly used to obtain the desired polarization for highly efficient coupling between electron cyclotron waves and plasma. The polarization strategy for 105-GHz electron cyclotron heating systems of HL-2M tokamak is studied in this paper. Considering the polarizers need high efficiency, stability, and low loss to realize any polarization states, two sinusoidal-grooved polarizers, which include a linear polarizer and an elliptical polarizer, are designed with the coordinate transformation method. The parameters, the period p and the depth d, of two sinusoidal-grooved polarizers are optimized by a phase difference analysis method to achieve an almost arbitrary polarization. Finally, the optimized polarizers are manufactured and their polarization characteristics are tested with a low-power test platform. The experimental results agree well with the numerical calculations, indicating that the designed polarizers can meet the polarization requirements of the electron cyclotron heating systems of HL-2M tokamak.     

Ultrashort Polarization Splitter Using Two-Mode Interference in Silicon Photonic Wires

An ultrashort polarization splitter based on the zero-gap directional coupler is proposed and realized. Its interference section is 8.8 $mu$m long. It is also shown that the length of the interference section can be reduced to about 2.1 $mu$m. The crosstalk for both transverse-electric (TE) and transverse-magnetic (TM) polarizations is 16 dB at a wavelength of 1.55 $mu$m. The extinction ratios of TE and TM polarizations are 18.2 and 13.7 dB, respectively. The device has 3-dB bandwidth of 43 nm in TE polarization and 50 nm in TM polarization with the center wavelength at 1.55 $mu$ m.      

Vertical-Cavity Surface-Emitting Lasers With Integrated Excitation of Surface Plasmon Polariton Modes

We report the excitation of surface plasmon polaritons (SPPs) on a thin Au layer integrated on top of the mirror of a vertical-cavity surface-emitting laser (VCSEL) along with their subsequent extraction to air. Gratings etched into the Au layer are used to couple the light in to and out of the metal film. The polarization properties of the optical emission from out-coupling gratings placed 5 $mu$ m away from the central optical aperture are used to confirm the coupling of the VCSEL light into and out of the SPP modes. The result paves the way to compact integrated plasmonic devices.      

38-krad/s 3.8-Grad Broadband Endless Optical Polarization Tracking Using LiNbO$_{3}$ Device

We demonstrate automatic endless optical polarization tracking over 3.8 Grad at up to 38-krad/s control speed with mean/maximum polarization errors of 0.068/0.185 rad. Without polarization fluctuations, mean/maximum polarization errors are 0.05/0.1 rad. Small-signal control time constant is about 2 $mu$s. Function is maintained over the wavelength range 1505–1570 nm.      

A New Linear Group-Wise Parallel Interference Cancellation Detector

In this paper, a new linear group-wise parallel interference cancellation (LGPIC) detector is proposed. Four different group-detection schemes are derived, namely, the linear group matched filter PIC (LGMF-PIC) detector, the linear group decorrelator PIC (LGDEC-PIC) detector, the linear group minimum mean square error PIC (LGMMSE-PIC) detector and the linear group parallel interference cancellation weighted PIC (LGPIC-PIC) detector. The convergence behavior of the proposed detector is analyzed and conditions of convergence are derived. Finally, extensive simulations regarding the convergence behavior and the effect of the grouping on the convergence behavior of the proposed LGPIC detector are conducted.

Dual Polarization Interleaved Spiral Antenna Phased Array With an Octave Bandwidth

A technique to design dual polarization spiral antenna phased arrays using mono polarization spirals is presented. The proposed technique consists of two interleaved subarrays, one for each polarization. The position of every spiral antenna is optimized through a genetic algorithm so that each array is nearly the size of the platform while having low sidelobes. Both resulting arrays have the same properties and are steerable. This method also helps to increase the bandwidth. An 80-element spiral array (spiral of width 0.25 m) with dual polarization is demonstrated, its beam can be steered ${pm 30}^{circ}$, over almost one octave (1.97:1). The physical rejection of the sidelobes (i.e., without weighting) is about ${- 10}~{rm dB}$.      

Theoretical Investigation for Reducing Polarization Sensitivity in Si-Nanowire-Based Arrayed-Waveguide Grating (de)Multiplexer With Polarization-Beam-Splitters and Reflectors

A novel design for reducing polarization sensitivity in silicon-on-insulator-based arrayed-waveguide grating (AWG) (de)multiplexer is presented. Each arrayed waveguide has two sections separated by a polarization beam splitter (PBS). These two sections have different core widths and length differences. With these PBSs, one polarization is reflected and the other one goes through. The through polarization enters the second section and is then reflected by a reflector at the end of the second section of the arrayed waveguide. The theoretical simulation shows that one can diminish greatly the polarization sensitivity of both the central channel wavelength and the channel spacing by optimizing the core width and length difference of the second section. The design procedure and formulas are given and an appropriate diffraction order is chosen to obtain a good fabrication tolerance. As an example, an ultrasmall $(82.2times 85.1 mu{hbox {m}}^{2})$ AWG (de)multiplexer with eight channels and a channel spacing of 4 nm is designed to have minimized polarization sensitivity and Bragg-grating PBSs and photonic crystal reflectors are used.      

Balanced operation of a GaInAs/GaInAsP multiple-quantum-wellintegrated heterodyne receiver

The balanced operation of a multiple-quantum-well balanced heterodyne receiver photonic integrated circuit (PIC) is described. Using only SMA-connected 50 Ω commercial electronics, a free-space beam sensitivity of -42.3 dBm at 108 Mb/s and -39.7 dBm at 200 Mb/s for NRZ FSK (frequency-shift keying) reception has been achieved. This represents a 14 dB improvement over any previous heterodyne receiver PIC sensitivity. In addition to providing the multichannel benefits of heterodyne reception, this is also the highest sensitivity yet reported for any OEIC (optoelectronic integrated circuit) receiver     

94 GHz Folded Fresnel Reflector Using C-Patch Elements

A 94 GHz folded Fresnel reflector (FFR) for helicopter collision avoidance Radar is presented. The antenna system consists of a primary source illuminating a semi-reflecting grid that reflects the primary source polarization toward the main reflector opposite the grid. The main reflector has two functions. It focuses the field in the desired direction and rotates the incident polarization by 90$^{circ}$ to enable it to pass through the grid and radiate. Specific patch elements having a C-shape have been designed for this purpose. In order to increase overall efficiency, the reflector combines 8 correcting zones in its center and 4 at the periphery. The reflector is manufactured using standard photolithographic techniques. The primary source consists of a metal waveguide covered with a small frequency selective surface (FSS) for matching purposes. The maximum measured gain is 36.5 dBi at 94 GHz. The maximum side lobe level is ${-}18$ dB. The return loss value does not exceed ${-}25$ dB. The frequency bandwidth ${-}3$ dB in gain and return loss is 10%. In-flight measurements were conducted demonstrating the ability to detect power lines at distances up to 680 m.      

Experimental Demonstration of Multi-Bit Optical Buffer Memory Using 1.55-$mu{hbox {m}}$ Polarization Bistable Vertical-Cavity Surface-Emitting Lasers

We demonstrate a novel all-optical buffer memory using 1.55-$mu{hbox {m}}$ polarization bistable vertical-cavity surface-emitting lasers (VCSELs). A one-bit data is stored as one of two orthogonal polarization states of a VCSEL in this memory. The polarization state is transferred from the VCSEL to another VCSEL which is optically connected in cascade as a shift register. A 4-bit optical buffer memory is constructed using two sets of the shift-register memory connected in parallel. These results show the technical feasibility of multi-bit optical buffer memory.      

Power efficiency evaluation in Dickson and voltage doubler charge pump topologies

This paper presents a theoretical and experimental comparison between two charge pump architectures commonly used in CMOS integrated circuits, namely the Dickson scheme and the cascade of voltage doublers. The comparison is carried out considering power efficiency as the main feature of interest. To compare the two topologies, two charge pumps were integrated in 0.18-μm triple-well CMOS technology. The two charge pumps were designed with the same operating clock frequency, the same storage capacitance per stage, and the same number of stages (and, thus, approximately the same area). The theoretical and the experimental comparison showed that the power efficiency of the voltage doubler scheme is higher (by about 13% at ), mainly thanks to the lower parasitic capacitance associated to the boosted nodes.     

A Low-Power, High-Suppression V-band Frequency Doubler in 0.13 $mu$ m CMOS

A V-band frequency doubler monolithic microwave integrated circuit with a current re-use buffer amplifier is presented. The circuit is designed and fabricated using 0.13 $mu$m CMOS technology. The buffer amplifier uses a current re-use topology, which adopts series connection of two common source amplifiers for low dc power consumption. The suppression of the fundamental frequency is obtained by shunting the input frequency at the output node of the doubler and the drain nodes of two common-source stages of the buffer amplifier. The fabricated frequency doubler exhibits an output power of ${-}$4.45 dBm and a conversion gain of ${-}$ 0.45 dB at input frequency of 27.1 GHz with an input power of ${-}$4 dBm. The suppression of the fundamental signal is 49.2 dB. The total dc power dissipation is 9 mW while the buffer amplifier consumes 5 mW. The integrated circuit size including pads is 1.24 mm$, times ,$0.75 mm. To our knowledge, this is the highest suppression with low-power dissipation among V-band frequency doublers.