Polarization Purity Research Articles

A Triple-Band Dual-Polarized Indoor Base Station Antenna for 2G, 3G, 4G and Sub-6 GHz 5G Applications

This paper proposes a new design of a triple-band dual-polarized indoor base station antenna for mobile communication systems serving the 2G, 3G, 4G, and the new sub-6 GHz 5G applications. The design consists of two orthogonal dipole antennas to provide dual polarization. Each dipole consists of three different radiator types—elliptical dipole, bowtie dipole, and cat-ear shaped arms for different bands. The proposed antenna offers three broad bands with the fractional bandwidths of 31.3% (0.7–0.96 GHz), 55.3% (1.7–3 GHz), and 14% (3.3–3.8 GHz) which can be controlled independently. The design also offers stable radiation patterns within the desired frequency bands, high polarization purity and, a simple feeding structure with a compact size and low profile which make this new design an ideal candidate for indoor mobile base stations serving the 2G, 3G, 4G, and the new sub-6GHz 5G applications.

Bioaerosols Polarization Measurement and Identification by Multi-wavelength Near-Distance Lidar

A near-distance polarizatio100n lidar system for real-time standoff detection of bioaerosols was designed developed and developed based on the polarization characteristics of non-spherical particle. Two laser light sources and depolarization components were engaged. The linear polarization purity of laser beam is 97%. The polarization and elastic scattering signal are collected with a Cassegrain telescope of 200mm aperture. In a semi-enclosed bioaerosol chamber, 10 kinds of biological aerosols were mixed and interrogated for linear polarization analysis following the sequence of 355nm, 532nm and 1064nm. It can be concluded that: 1) the depolarization ratios are wavelength-dependent; 2) the identification of bioaerosols can be achieved by through the application of Euclidian correlation degree and Mhalanobis distance.

A Dual-Broadband Dual-Polarized Fylfot-Shaped Antenna for Mobile Base Stations Using MIMO Over-Lapped Antenna Subarrays

This paper proposes a novel design of a dual-broadband dual-polarized antenna for mobile communication base stations. The proposed antenna is Fylfot-shaped and covers 0.7–0.96 and 1.7–2.7 GHz simultaneously (with S11 ≤ −10 dB), which are the two common frequency bands for mobile communication systems. Three resonant frequencies are produced in the proposed design where two of them are independently controlled to achieve the dual-broadband performance. A prototype of the proposed antenna has been developed and tested. The results demonstrate that the antenna has high isolation between its ports, high polarization purity, and stable radiation patterns across both the frequency bands. A new linear array is proposed and implemented. Unlike reported dual-band base station antenna arrays, the proposed array uses a novel technique of two MIMO overlapped subarrays with shared radiating antenna elements. The overlapped subarrays have excellent frequency diversity performance with low envelope correlation coefficients. The array has been found to have the same performance as a standard conventional base station antenna but with 25% less number of antenna elements, which leads to a smaller size and lower cost. The simple antenna structure and the novel smart MIMO overlapped antenna subarrays technique give the design the privilege to be an ideal candidate for a low-cost directive base station antenna.

Ball Grid Array Module With Integrated Shaped Lens for 5G Backhaul/Fronthaul Communications in F-Band

In this paper, we propose a ball grid array (BGA) module with an integrated 3-D-printed plastic lens antenna for application in a dedicated 130 GHz OOK transceiver that targets the area of 5G backhaul/fronthaul systems. The main design goal was the full integration of a small footprint antenna with an energy-efficient transceiver. The antenna system must be compact and cost effective while delivering an approximately 30 dBi gain in the working band, defined as 120 to 140 GHz. Accordingly, a $2 \times 2$ array of aperture-coupled patch antennas was designed in the $7 \times 7 \times 0.362$ mm3 BGA module as the feed antenna of the lens. This achieved a 7.8 dBi realized gain, broadside polarization purity above 20 dB, and over 55% total efficiency from 110 to 140 GHz (20% bandwidth). A plastic elliptical lens 40 mm in diameter and 42.3 mm in height was placed on top of the BGA module. The antenna achieved a return loss better than −10 dB and a 28 dBi realized gain from 114 to 140 GHz. Finally, active measurements demonstrated a >12 Gbps Tx/Rx link at 5 m with bit error rate (BER) < 10−6 at 1.6 pJ/b/m. These results pave the way for future cost-effective, energy-efficient, high-data rate backhaul/fronthaul systems for 5G communications.

Lasing by driven atoms-cavity system in collective strong coupling regime

The interaction of laser cooled atoms with resonant light is determined by the natural linewidth of the excited state. An optical cavity is another optically resonant system where the loss from the cavity determines the resonant optical response of the system. The near resonant combination of an optical Fabry-Pérot cavity with laser cooled and trapped atoms couples two distinct optical resonators via light and has great potential for precision measurements and the creation of versatile quantum optics systems. Here we show how driven magneto-optically trapped atoms in collective strong coupling regime with the cavity leads to lasing at a frequency red detuned from the atomic transition. Lasing is demonstrated experimentally by the observation of a lasing threshold accompanied by polarization and spatial mode purity, and line-narrowing in the outcoupled light. Spontaneous emission into the cavity mode by the driven atoms stimulates lasing action, which is capable of operating as a continuous wave laser in steady state, without a seed laser. The system is modeled theoretically, and qualitative agreement with experimentally observed lasing is seen. Our result opens up a range of new measurement possibilities with this system.

Creation of a multi-segmented optical needle with prescribed length and spacing using the radiation pattern from a sectional-uniform line source

This paper presents a method to generate a multi-segmented optical needle with a strong longitudinally polarized field, uniform intensity along the optical axis, and a transverse size (~0.36λ). The length of each segment in the optical needle and the spacing between adjacent segments are controllable by reversing and focusing the radiation pattern from a sectional-uniform line source antenna to the focal volume of a 4Pi focusing system. By solving the inverse problem, we can obtain the required incident field distribution at the pupil plane to create the multi-segmented optical needle. Numerical examples demonstrate that a multi-segmented optical needle with variable focal depth, adjustable interval, narrow lateral width, homogeneous intensity, and high longitudinal polarization purity can be formed using the proposed approach. The length of each needle segment is approximately equal to the length of the corresponding sectional uniform line source. The multi-segmented optical needle may be employed in applications such as multi-particle acceleration, multi-particle trapping and manipulation, laser machining, and laser material processing.

Amplification of a radially polarised beam in an Yb:YAG thin-slab

The use of an Yb:YAG thin-slab architecture for amplification of a radially polarised beam at 1030 nm is investigated and shown to be a promising route for power scaling. The detrimental impact of the Gouy phase shift on radial polarisation purity is considered and a simple scheme for effective phase shift management to restore polarisation purity is presented. Preliminary experiments based on a double-pass amplifier configuration yielded an output beam with a high radial polarisation extinction ratio of 15 dB and no degradation in polarisation purity despite the non- axial symmetry of amplifier gain medium. At 50 W of launched pump power a small-signal gain of 7.5 dB was obtained for a 25 mW input, whilst 4.4 dB gain was obtained for a 1.45 W input. The prospects for further power scaling are discussed.

Cross-spectral purity of Stokes parameters, purity of partial polarization and statistical similarity

In this paper, we discuss the concept of cross-spectral purity of Stokes parameters, purity of general partial polarization and implications of statistical similarity of an optical field. The conditions of cross-spectral purity of Stokes parameters and purity of partial polarization are obtained. Then, by utilizing statistical similarity, the relationships between the two purity and spatial coherence are explored. At last, a special situation that gives a relation of these two kinds of purity is briefly discussed.

Inductive loaded compact monopole antenna for ultra‐wideband applications

An effective method to design an ultra-wideband antenna using a vertical narrow strip element is described. The proposed low profile antenna has good radiation characteristics such as polarisation purity, omnidirectional radiation pattern and good efficiency over the entire band of operation, which are the most desirable characteristics required for a wireless system to operate in the present high interference environment. The designed antenna has a measured return loss of below −10 dB and low cross polarised uniform omnidirectional pattern measured in anechoic chamber for the frequency range of 2.85 to 10.6 GHz.

Wideband omni‐directional antenna with novel feeding structure for improving radiation patterns

A wideband vertically polarised omni-directional antenna, which is characterised with a height of 0.1 λ L ( λ L: the wavelength at low frequency), a relative operating bandwidth of 48% (1.25-2.04 GHz), stable gains and improved cross-polarisation, is presented. A pair of λ /4 resonators is introduced to broaden the bandwidth; a symmetrical hook-shaped probe is employed to improve the cross-polarisation; the shorting pins between the patch radiator and ground plane are used to reduce the dimension of the antenna. To clarify the improved cross-polarisation, a comparison between the radiation patterns in asymmetrically and novel symmetrically feeding antennas is shown. Measured and simulated results agree well with each other, indicating good performance of wide bandwidth, low profile, stable radiation patterns and gains. Moreover, the polarisation purity of the proposed antenna has been significantly improved compared with that of the asymmetrically feeding antenna.

Precise and diffraction-limited waveguide-to-free-space focusing gratings

We present the design and characterization of waveguide grating devices that couple visible-wavelength light at λ = 674 nm from single-mode, high index-contrast dielectric waveguides to free-space beams forming micron-scale diffraction-limited spots a designed distance and angle from the grating. With a view to application in spatially-selective optical addressing, and in contrast to previous work on similar devices, deviations from the main Gaussian lobe up to 25 microns from the focus and down to the 5 × 10−6 level in relative intensity are characterized as well; we show that along one dimension the intensity of these weak sidelobes approaches the limit imposed by diffraction from the finite field extent in the grating region. Additionally, we characterize the polarization purity in the focal region, observing at the center of the focus a low impurity <3 × 10−4 in relative intensity. Our approach allows quick, intuitive design of devices with such performance, which may be applied in trapped-ion quantum information processing and generally in any systems requiring optical routing to or from objects 10 s–100 s of microns from a chip surface, but benefitting from the parallelism and density of planar-fabricated dielectric integrated optics.

Dual circularly polarized multilayer MIMO antenna array with an enhanced SR-feeding network for C-band application

Wide-band circularly polarized multi-input multi-output (MIMO) antenna array with a 2 × 4 feed network was proposed for C-band application. Different unique techniques were utilized in the proposed array to enhance the antenna characteristics, such as gain, 3 dB axial ratio bandwidth (ARBW), impedance tuning, and ruinous mutual coupling effects. A miniaturized dual-feed Tai chi-shaped antenna element with a pair of feeding points and a pair of eyebrow-shaped strips was presented for enhancing circular polarization (CP) purity and impedance matching. For a better improvement of CP features, a 2*4 MIMO sequentially rotated (MIMO-SR) feed network was used to achieve broader 3 dB ARBW. Besides, the MIMO feature of the feed network could control the left- and right-handed CP, respectively. Ultimately, specific forms of slot and slit structures were applied onto the top layer of MIMO feed network that provided a high isolation between the radiating elements and array network. Furthermore, the diversity gain (DG) was studied. The extracted measured results illustrated an impedance bandwidth of 3.5–8.2 GHz at port 1 and 3.5–8.3 GHz at port 2 for VWSR &lt; 2 and 3 dB ARBW of 4.6–7.6 GHz at port 1 and 4.6–7.5 GHz at port 2. The peak gain of 9.9 dBi was at 6 GHz.

Radially and azimuthally polarized nanosecond Yb-doped fiber MOPA system incorporating temporal shaping.

We report an Yb-doped fiber master-oscillator power-amplifier (MOPA) system with the capability of selectively generating doughnut-shaped radially and azimuthally polarized beams with user-defined temporal pulse shapes. The desired output polarization was generated with the aid of a nanograting spatially variant half-waveplate (S-waveplate). The latter was used to convert the linearly polarized fundamental (LP01) mode output from the preamplification stages to a doughnut-shaped radially polarized beam prior to the power amplifier stage. A maximum output pulse energy of ∼860 μJ was achieved for ∼100 ns pulses at 25 kHz with user-defined pulse shape for both radial and azimuthal polarization states. The polarization purity and beam propagation factor (M2) were measured to be >12 dB and 2.2, respectively.

High-power single-stage single-crystal Yb:YAG fiber amplifier for radially polarized ultrashort laser pulses

We report on a single-stage high-power amplification of a radially polarized mode-locked laser beam in a single-crystal fiber (SCF) amplifier. The seed beam was amplified by a factor of 5.0 to an average output power of 66.3 W. The pulse duration of the amplified pulses was measured to be 909 fs at a repetition rate of 40.7 MHz, corresponding to a pulse energy of 1.63 $$\upmu$$ J and a resulting pulse peak power of 1.58 MW. The output beam showed a very high quality of the doughnut-shaped intensity distribution and furthermore a high radial polarization purity.

A five elements sequential rotation array arranged in a single‐layer pentagonal substrate

ABSTRACTA pentagonal circular polarized subarray composed of five elements is proposed for operation at 2.45 GHz. The array is based on the sequential rotation architecture (SRA), implemented with a sequential phase distribution network. Despite a more complex design in comparison to the canonical 4‐elements SRA, a pentagonal subarray is more suited to be packed in a Bucky‐ball or icosahedral arrangement, ideal for smart antennas with wide angle spatial coverage. A single‐layer via‐less prototype is fabricated on a common FR4 substrate. Measurements show a realized gain of 6.15 dBi with a polarization purity exceeding 20 dB at 2.45 GHz. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1077–1081, 2017

Cross type defected ground structure integrated microstrip antenna: a novel perspective for broad banding and augmenting polarization purity

A simple cross type defected ground structure (CDGS) integrated rectangular microstrip antenna (RMA) has been proposed to achieve broad bandwidth along with augmented (improved) co-polarized to cross-polarized radiation (CP-XP) isolation over principal and diagonal planes. In this design, a crucial emphasis is given for concurrent improvement of both bandwidth and polarization purity of microstrip antenna without hampering dominant mode fields. Around 25–28 dB CP-XP isolation is achieved over wide elevation angle with the proposed structure with 25% impedance bandwidth. The simulated and measured results show a close resemblance with each other. The proposed geometry is very simple, easy to fabricate and therefore helps in effortlessness manufacturing process. Therefore, the present structure appears to be ideal in numerous applications where polarization purity is the key issue over the wide bandwidth.

Ultra-broadband and high-efficiency reflective linear polarization convertor based on planar anisotropic metamaterial in microwave region

A simple design of an ultra-broadband and high-efficiency reflective linear polarization convertor with 90° rotation is presented in the microwave region. This convertor is formed from the planar anisotropic metamaterial (MM) using cut-wire (CW) structure. Three resonance modes are generated by electric and magnetic fields of incident wave, which lead to bandwidth expansion extremely of cross-polarization reflection. The simulation result shows that a linearly polarized wave can be converted into its orthogonal polarization after reflection, the polarization conversion ratio is above 90% in the frequency range of 5.1–12.1GHz and the relative bandwidth is up to 78.6%, which agree well with the experimental results. Both simulation and experiment results demonstrate the capability of linear polarization conversion by 90° with high polarization purity after reflection in the above frequency range, which can be confirmed by ellipticity η and the polarization rotation azimuth angle θ. The designed structure that utilized to build the thin MM slab is about λ0/8.72 evaluated at operating center frequency. It has application values in polarization control with high performances.

Engineering of cylindrical vector fields with a twisted nematic spatial light modulator

We demonstrate a technique for the generation of vectorial optical fields based on a single pass of light onto a reflective twisted nematic spatial light modulator (TN-SLM). Using a beam splitter and a quarter-wave plate, a polarization rotator is implemented. A curve of the behavior of this polarization rotator with the twisted nematic modulator in use proves a modulation up to 177 deg, making this setup suitable for engineering of cylindrical vector fields. A mathematical justification and an experimental demonstration of the generation of these beams and their quality are presented. The experimental results show that despite the presence of a small component of elliptical polarization, a twisted nematic modulator can be used to achieve local polarization control. A series of vector fields with variations of the parameters of topological charge, phase offset, and quadratic phase are engineered, analyzed with a linear polarizer, and captured. The proposed setup represents a simple approach for polarization manipulation using a TN-SLM and few optical elements, achieving polarization purity greater than 94%.

A Compact Circularly Polarized Antenna for 5.8-GHz Intelligent Transportation System

A compact circularly polarized antenna suitable for applications of an intelligent transportation system (ITS) is presented. The antenna consists of a disc patch operating in modal degeneration, which is gap-coupled with multiple annular sectors. The use of parasitic resonators coupled to the degenerated modes of the patch enhances the realized gain and the polarization purity, at the cost of only a modest increase in the area. Despite the small size of $35\times 35$ mm $^2$ (0.46 $\lambda _0^2$ at the central frequency of 5.8 GHz), the experimental validation of the best prototype confirms a hemispherical coverage with a half-beam power of 80°, a maximum left-hand gain of 7.16 dB, a cross-polarization discrimination of 21 dB, and a 10-dB return-loss bandwidth exceeding 900 MHz, a performance suitable for ultracompact tag reader realized in cost-effective single-layer technology.

Low-Profile Radially Corrugated Horn Antenna

This letter proposes a low-profile horn antenna with radial corrugations. The depth and width of the corrugations are suitably chosen to excite the mode HE $_{11}$ in the corrugated section. This mode spreads uniformly across the whole aperture, thereby maximizing the radiating area and the aperture efficiency. The good polarization purity of mode HE $_{11}$ provides a good cross-polar level and a low sidelobe level. The structure is fed by a circular waveguide with two matching elements on the feeding plane that minimize the return loss level. A prototype has been fabricated and measured to operate in the Ku-band. The prototype, with a height of just 6.9 mm, i.e., 0.3 $\lambda_{0}$ , provides a maximum gain above 12.2 dBi and an aperture efficiency better than 72% within the operating frequency band.