Performance analysis of the mutual coupling effect on Phased Array Feeds

A phased array feed(PAF)is a type of receiving array that places phased array antennas on the focal plane of a radio telescope to expand its field of view and improve observation efficiency.Owing to the mutual coupling effect between elements caused by a tightly arranged feed array,which changes the performance of a PAF,this paper presents a 7×7 rectangular feed array model for a 25 m reflector telescope.By adjusting the element spacings,the performance of a PAF with different spacings is comprehensively analyzed with respect to the mutual coupling effect via performance statistics and comparison.This research aims to provide a reference for the preliminary design of a related PAF.

Photon-photon interactions with inner coupled double-cavity

This paper describes the interaction between two spatial modes of the optical fields with a single atom trapped inner coupled double-cavity. Theoretical derivation and numerical simulation with the experimental available parameters show that photon-photon switching and π phase shift of single photons may be achieved with current experimental technology. As the probe and control fields are in different spatial modes, the system is superior for implementing cavity QED-based photonic quantum networks.

Design of a hexagonal air-coupled capacitive micromachined ultrasonic transducer for air parametric array

An air parametric array can generate a highly directional beam of audible sound in air,which has a wide range of applications in targeted audio delivery.Capacitive micromachined ultrasonic transducer(CMUTs)have great potential for air-coupled applications,mainly because of their low acoustic impedance.In this study,an air-coupled CMUT array is designed as an air parametric array.A hexagonal array is proposed to improve the directivity of the sound generated.A finite element model of the CMUT is established in COMSOL software to facilitate the choice of appropriate structural parameters of the CMUT cell.The CMUT array is then fabricated by a wafer bonding process with high consistency.The performances of the CMUT are tested to verify the accuracy of the finite element analysis.By optimizing the component parameters of the bias-T circuit used for driving the CMUT,DC and AC voltages can be effectively applied to the top and bottom electrodes of the CMUT to provide efficient ultrasound transmission.Finally,the prepared hexagonal array is successfully used to conduct preliminary experiments on its application as an air parametric array.

Nonreciprocal coupling induced entanglement enhancement in a double-cavity optomechanical system

We investigate the quantum entanglement in a double-cavity optomechanical system consisting of an optomechanical cavity and an auxiliary cavity,where the optomechanical cavity mode couples with the mechanical mode via radiation-pressure interaction,and simultaneously couples with the auxiliary cavity mode via nonreciprocal coupling.We study the entanglement between the mechanical oscillator and the cavity modes when the two cavities are reciprocally or non-reciprocally coupled.The logarithmic negativity E_(n)^((1))(E_(n)^((2)))is adopted to describe the entanglement degree between the mechanical mode and the optomechanical cavity mode(the auxiliary cavity mode).We find that both E_(n)^((1))and E_(n)^((2))have maximum values in the case of reciprocal coupling.By using nonreciprocal coupling,E_(n)^((1))and E_(n)^((2))can exceed those maximum values,and a wider detuning region where the entanglement exists can be obtained.Moreover,the entanglement robustness with respect to the environment temperature is also effectively enhanced.

Quantum Information Processing in An Array of Fiber Coupled Cavities

We consider a fiber coupled cavity array. Each cavity is doped with a single two-level atom. By treating the atom-cavity systems as combined polaritonie qubits, we can transform it into a polaritonic qubit-qubit array in the dispersive regime. We show that the four fiber coupled cavity open chain and ring can both generate the four qubit W state and cluster state, and can both transfer one and two qubit arbitrary states. We also discuss the dynamical behaviors of the four fiber coupled cavity array with unequal couplings.

Mutual coupling suppression of aperture coupled microstrip antenna array

A mutual coupling suppression method is proposed for microstrip antenna array by cutting four small semi-circle annular apertures on the metal plate. The structure of antenna array is composed of 2 × 2 four elements. The antenna consists of double layer dielectric, and it realizes circular polarization characteristics by cutting rectangular slot on circular patch in the direction of 45°, by using aperture coupling feeding and reverse feeding principle. There is 90＊ phase difference between adjacent antenna elements. Thus, it cuts off the coupling current field between the elements, suppresses the surface wave and reduces the mutual coupling by cutting four semi-circle annular apertures symmetrically on the metal plate. The simulation results show that after cutting four semi-circle annular apertures, the antenna array coupling coefficients decrease significantly, and the side and back lobe levels are suppressed effectively with the gain of antenna improved. So the proposed method is effective to suppress microstrip antenna array mutual coupling.

A New Dual Polarized Aperture-Coupled Printed Array for SAR Applications

This paper presents a new design of dual polarized aperture coupled printed antenna array. The finite difference time domain (FDTD) analysis of an aperture coupled microstrip element is performed, and the effects of antenna parameters on its characteristics are obtained to guide the design of the printed array. Then an 8×2 dual polarized array design in X band is introduced with configuration plots. In order to improve its isolation and cross polarization, an outphase displacement feeding technique is adopted in the feed network. Also, the round bends are used instead of conventional right angle bends so as to achieve better VSWR performance. Experimental results are presented, indicating the validity of the design. This dual polarized array can be applied as a sub array of spaceborne SAR systems.

Quantum Information Processing in a Coupled Cavity Array

We consider a one-dimensional array of L identical coupled cavities,and each cavity is doped with atwo-level qubit.Experimentally,it has been developed in several varieties by the newest technology.We find that theone-qubit quantum state can be perfectly transferred through the cavity array,and the entanglement between the firsttwo qubits can also be transferred to the last two qubits.In addition,we successfully realized the entangling gate andswap gate in the coupled cavity array.

An Array Consisting of 10 High-Speed Side-Illuminated Evanescently Coupled Waveguide Photodetectors Each with a Bandwidth of 20 GHz

We design and fabricate a parallel system with 10 high speed side-illuminated evanescently coupled waveguide photodetectors （ECPDs）. The 10 ECPDs exhibit a uniform 3dB bandwidth of 20 GHz and low dark current of about i nA at 2 V reverse bias. The 10 ECPDs also exhibit uniform photo-responsivity of about 0.23A/W with an active region of 5 × 25μmS. The photodetector array has a total bandwidth of more than 200 GHz and can be integrated with other optoelectronic devices.

Factors Affecting the Top Stripping of GaAs Microwire Array Fabricated by Inductively Coupled Plasma Etching

The effects of different masks and patterns on the top stripping of GaAs microwire arrays fabricated by inductively coupled plasma etching for 20min and 40min are investigated. The results show that the mask layer is the main affect of the top stripping of the GaAs microwires in 40min. Increasing the mask layers and reducing the photoresist layers can prevent top stripping and result in a suitable GaAs microwire array.

Fiber Coupling of Laser Diode Bar to M ultimode Fiber Array

A piece of multimode optical fiber with a low num er ical aperture (NA) is used as an inexpensive microlens to collimate the output r adiation of a laser diode bar in the high numerical aperture (NA) direction.The emissions of the laser diode bar are coupled into multimode fiber array.The radi ation from individual ones of emitter regions is optically coupled into individu al ones of fiber array.Total coupling efficiency and fiber output power are 75% and 15W,respectively.

Decoupling technique of patch antenna arrays with shared substrate by suppressing near-field magnetic coupling using magnetic metamaterials

In this paper,we propose the decoupling technique of patch antenna array by suppressing near-field magnetic coupling（NFMC） using magnetic metamaterials.To this end,a highly-integrated magnetic metamaterials,the substrate-integrated split-ring resonator（SI-SRR）,is firstly proposed to achieve negative permeability at the antenna operating frequency.By integrating SI-SRR in between two closely spaced antennas,magnetic fields are blocked in the shared substrate due to negative permeability of SI-SRR,reducing NFMC between the two antennas.To verify the technique,a prototype was fabricated and measured.The measured results demonstrated that the isolation can be enhanced by more than 17 dB even when the gap between the two patch antennas is only about 0.067 A.Due to high integration,this technique provides an effective alternative to high-isolation antenna array.

A Novel Beam Design Method for mm Wave Multi-Antenna Arrays with Mutual Coupling Reduction

To overcome the mutual coupling (MC) of multiple antennas in millimeter wave (mmWave) communication systems, a novel beam design method with low complexity is proposed in this paper. Firstly, an equivalent channel model incorporating the effect of MC is analyzed and established, and then an optimal precoding / combiner vector for beamforming is derived. On this basis, by using greedy geometric (GG) algorithm, a novel hybrid beam design method is proposed. Finally, the performance of proposed method is analyzed and compared with other traditional ones. The simulation results show that the proposed method has better suppression of the MC effect as well as lower complexity.

Estimation of Mutual Coupling Coefficient of the Array by Simulated Annealing Algorithm

We propose a method for estimating the mutual coupling coefficient among antennas in this paper which is based on the principle of signal subspace and the simulated annealing （SA） algorithm. The computer simulation has been conducted to illustrate the＇ excellent performance of this method and to demonstrate that it is statistically efficient. The benefit of this new method is that calibration signals and unknown signals can be received simultaneously, during the course of calibration.

Sensor array calibration for uniform rectangular array in presence of mutual coupling and sensor gain-and-phase errors

The sensor array calibration methods tailored to uniform rectangular array(URA)in the presence of mutual coupling and sensor gain-and-phase errors were addressed.First,the mutual coupling model of the URA was studied,and then a set of steering vectors corresponding to distinct locations were numerically computed with the help of several time-disjoint auxiliary sources with known directions.Then,the optimization modeling with respect to the array error matrix(defined by the product of mutual coupling matrix and sensor gain-and-phase errors matrix)was constructed.Two preferable algorithms(called algorithm I and algorithm II)were developed to minimize the cost function.In algorithm I,the array error matrix was regarded as a whole parameter to be estimated,and the exact solution was available.Compared to some existing algorithms with the similar computation framework,algorithm I can make full use of the potentially linear characteristics of URA's error matrix,thus,the calibration precision was obviously enhanced.In algorithm II,the array error matrix was decomposed into two matrix parameters to be optimized.Compared to algorithm I,it can further decrease the number of unknowns and,thereby,yield better estimation accuracy.However,algorithm II was incapable of producing the closed-form solution and the iteration operation was unavoidable.Simulation results validate the excellent performances of the two novel algorithms compared to some existing calibration algorithms.

Electromagnetic coupling reduction in dual-band microstrip antenna array using ultra-compact single-negative electric metamaterials for MIMO application

In this paper, an ultra-compact single negative（SNG） electric waveguided metamaterial（WG-MTM） is first investigated and used to reduce the mutual coupling in E ＆ H planes of a dual-band microstrip antenna array. The proposed SNG electric WG-MTM unit cell is designed by etching two different symmetrical spiral lines on the ground, and has two stopbands operating at 1.86 GHz and 2.40 GHz. The circuit size is very compact, which is only λ_0/33.6 ×λ_0/15.1（where λ_0 is the wavelength at 1.86 GHz in free space）. Taking advantage of the dual-stopband property of the proposed SNG electric WG-MTM, a dual-band microstrip antenna array operating at 1.86 GHz and 2.40 GHz with very low mutual coupling is designed by embedding a cross shaped array of the proposed SNG electric WG-MTM. The measured and simulated results of the designed dual-band antenna array are in good agreement with each other, indicating that the mutual coupling of the fabricated dual-band antenna array realizes 9.8/11.1 d B reductions in the H plane, 8.5/7.9 d B reductions in the E plane at1.86 GHz and 2.40 GHz, respectively. Besides, the distance of the antenna elements in the array is only 0.35 λ_0（where λ_0 is the wavelength at 1.86 GHz in free space）. The proposed strategy is used for the first time to reduce the mutual coupling in E ＆ H planes of the dual-band microstrip antenna array by using ultra-compact SNG electric WG-MTM.

Differential Quasi-Yagi Antenna and Array

A novel differential quasi-Yagi antenna is first presented and compared with a normal single-ended counterpart.The simulated and measured results show that the differential quasi-Yagi antenna outperforms the conventional single-ended one.The differential quasi-Yagi antenna is then used as an element for linear arrays.A study of the coupling mechanism between the two differential and the two singleended quasi-Yagi antennas is conducted,which reveals that the TE0 mode is the dominant mode,and the driver is the decisive part to account for the mutual coupling.Next,the effects of four decoupling structures are respectively evaluated between the two differential quasi-Yagi antennas.Finally,the arrays with simple but effective decoupling structures are fabricated and measured.The measured results demonstrate that the simple slit or air-hole decoupling structure can reduce the coupling level from−18 dB to−25 dB and meanwhile maintain the impedance matching and radiation patterns of the array over the broad bandwidth.The differential quasi-Yagi antenna should be a promising antenna candidate for many applications.

Stable stripe and vortex solitons in two-dimensional spin-orbit coupled Bose-Einstein condensates

We present a flexible manipulation and control of solitons via Bose-Einstein condensates.In the presence of Rashba spin-orbit coupling and repulsive interactions within a harmonic potential,our investigation reveals the numerical local solutions within the system.By manipulating the strength of repulsive interactions and adjusting spin-orbit coupling while maintaining a zero-frequency rotation,diverse soliton structures emerge within the system.These include plane-wave solitons,two distinct types of stripe solitons,and odd petal solitons with both single and double layers.The stability of these solitons is intricately dependent on the varying strength of spin-orbit coupling.Specifically,stripe solitons can maintain a stable existence within regions characterized by enhanced spin-orbit coupling while petal solitons are unable to sustain a stable existence under similar conditions.When rotational frequency is introduced to the system,solitons undergo a transition from stripe solitons to a vortex array characterized by a sustained rotation.The rotational directions of clockwise and counterclockwise are non-equivalent owing to spin-orbit coupling.As a result,the properties of vortex solitons exhibit significant variation and are capable of maintaining a stable existence in the presence of repulsive interactions.

32×32 NbN SNSPD array based on thermally coupled row-column multiplexing architecture

We report a superconducting nanowire single‐photon detector(SNSPD)array aiming for a near‐infrared 1550‐nm wavelength that consists of 32×32 nanowire pixels and an area of 0.96 mm×0.96 mm.Unlike most reported large‐scale SNSPD arrays with amorphous films,NbN superconducting nanowires are employed in our array,which allows the detector operation at 2.3 K provided by a compact two‐stage Gifford–McMahon cryocooler.Thermally coupled row–column multiplexing is employed in our arrays to avoid current redistribution and loss of electrical signal occurring in the electrically coupled row–column architecture.The fabricated detector array shows a pixel yield of 94%and maximal intrinsic efficiencies of 77%and 96%at 1550 nm and 405 nm,respectively.The timing jitter and the thermal coupling probability are also investigated.

High-order extended coprime array design for direction of arrival estimation

Nonuniform linear arrays,such as coprime array and nested array,have received great attentions because of the increased degrees of freedom(DOFs)and weakened mutual coupling.In this paper,inspired by the existing coprime array,we propose a high-order extended coprime array(HoECA)for improved direction of arrival(DOA)estimation.We first derive the closed-form expressions for the range of consecutive lags.Then,by changing the inter-element spacing of a uniform linear array(ULA),three cases are proposed and discussed.It is indicated that the HoECA can obtain the largest number of consecutive lags when the spacing takes the maximum value.Finally,by comparing it with the other sparse arrays,the optimized HoECA enjoys a larger number of consecutive lags with mitigating mutual coupling.Simulation results are shown to evaluate the superiority of HoECA over the others in terms of DOF,mutual coupling leakage and estimation accuracy.