Ka Band Research Articles

Study on the scattering characteristics of Ka millimeter wave by dust storms

As to study the scattering characteristics of millimeter wave by sand particles, the integrated detection on dust storms over the Taklimakan Desert was the first time to conduct with the Ka band millimeter wave radar, the Grimm 180, the Laser Particle Size Analyzer and the visibility meter. The complex permittivity of sand particle (εm), the probability distribution function of sand particles, the number of sand particles, the attenuation coefficient and the reflectivity factors were calculated by the observations of these instruments; moreover, the power spectrums of the dust storm, sunny day and precipitation were comparatively analyzed. The results showed that: the εm of 35 GHz millimeter wave by sand particles is 3.0078-j0.0987. The probability distribution of sand particles conforms to lognormal distribution, with the mean of -2.352 and the standard deviation of 0.422. Furthermore, when the visibility drops from 3000 to 0 m, the number of sand particles rises from 2 × 105 to 1 × 106 in L · min−1 and the attenuation coefficient increases from 1 to 8 dB · km−1. The peak and the average values of power spectrums in dust storm are lower than those in precipitation, which indicates that the scattering ability of sand particles is less than that of precipitation particles. During the dust storms, the reflectivity factors range between -40 and 20 dBZ. These findings provide theoretical basis for the further study of the scattering properties of sand particles in the future.

Comparison of microwave absorption characteristics of Co-Zr substituted Ni-Zn ferrites and Mg-Zr substituted Ni-Zn ferrites in Ka band (26.5 – 40 GHz)

In the present work, microwave absorption characteristics of cobalt-zirconium (Co-Zr) doped and magnesium-zirconium (Mg-Zr) doped nickel zinc (Ni-Zn) ferrites in Ka band, have been compared. The samples with chemical composition, Ni0.6Zn0.4(CoZr)xFe2-2xO4 (x = 0.05, 0.10, 0.15, 0.20 and 0.25) and Ni0.6Zn0.4(MgZr)xFe2-2xO4 (x = 0.05, 0.10, 0.15 and 0.20) have been prepared by sol–gel citrate precursor route and then, sintered at 1000 °C. The absorption characterization has been done by using vector network analyser (VNA) for both the series. Enhancement of dielectric and magnetic properties is observed with the addition of Co-Zr & Mg-Zr in simple Ni-Zn spinel ferrites, which make these ferrites suitable to work as microwave absorber materials (MAMs) in high frequency shielding applications. The minimum values of reflection loss (RL) obtained in both the series have been compared and it has been found that Mg-Zr substituted Ni-Zn ferrites (with lowest RL equal to −53.19 dB) perform better in terms of absorption than their counterpart Co-Zr doped Ni-Zn ferrites (with lowest RL equal to –33.06 dB). The prepared compositions of both the series, can be effectively used as high-performance microwave absorbers.

Enhancing the resonance characteristics of circular patch antenna for SHF applications

Microstrip patch antenna is attractive for various applications due to its easy fabrication, low cost and small size. It simply comprises of a radiating patch and ground plane that are separated by a dielectric substrate. However, the resonance bandwidth of the microstrip antenna is still an issue that needs to be considered in research. This paper aims to enhance the bandwidth of a microstrip antenna or introduce more resonant frequencies within the Super High Frequency (SHF) band. The paper demonstrates empirical results for circular-shaped patch antenna using the High Frequency Structure Simulator (HFSS). It begins by investigating different patch sizes and substrate materials, so that an optimal preliminary design is introduced. Then, different slot shapes are inserted into the patch for significant enhancement of the resonance characteristics. As a result, new ultra-wideband (UWB) antenna designs are presented with bandwidth results reaching 15.5 GHz within the C, X, Ku and K bands. Also, new multiband antenna designs are presented with improved reflection valleys in the Ku, K and Ka bands.

Source/Load-Pull Noise Measurements at Ka Band

This paper is focused on the extraction of the noise parameters of a linear active device by exploiting both forward and reverse noise power measurements associated with different terminations. In order for load-pull measurements to yield a significant marginal improvement (as compared to forward measurements only) it is expected that the device under test should appreciably deviate from unidirectionality. For this reason, the source/load-pull technique is applied to frequencies at which the considered devices are still usable but their reverse noise factor exhibits a measurable dependence on the output terminations. Details on the test bench set up to the purpose, covering the 20–40 GHz frequency range, are provided. A characterization campaign on a 60 nm gate length, 4×35 µm GaN-on-Si HEMT fabricated by OMMIC is illustrated.

Opportunistic Rain Rate Estimation from Measurements of Satellite Downlink Attenuation: A Survey.

Recent years have witnessed a growing interest in techniques and systems for rainfall surveillance on regional scale, with increasingly stringent requirements in terms of the following: (i) accuracy of rainfall rate measurements, (ii) adequate density of sensors over the territory, (iii) space-time continuity and completeness of data and (iv) capability to elaborate rainfall maps in near real time. The devices deployed to monitor the precipitation fields are traditionally networks of rain gauges distributed throughout the territory, along with weather radars and satellite remote sensors operating in the optical or infrared band, none of which, however, are suitable for full compliance to all of the requirements cited above. More recently, a different approach to rain rate estimation techniques has been proposed and investigated, based on the measurement of the attenuation induced by rain on signals of pre-existing radio networks either in terrestrial links, e.g., the backhaul connections in cellular networks, or in satellite-to-earth links and, among the latter, notably those between geostationary broadcast satellites and domestic subscriber terminals in the Ku and Ka bands. Knowledge of the above rain-induced attenuation permits the retrieval of the corresponding rain intensity provided that a number of meteorological and geometric parameters are known and ultimately permits estimating the rain rate locally at the receiver site. In this survey paper, we specifically focus on such a type of “opportunistic” systems for rain field monitoring, which appear very promising in view of the wide diffusion over the territory of low-cost domestic terminals for the reception of satellite signals, prospectively allowing for a considerable geographical capillarity in the distribution of sensors, at least in more densely populated areas. The purpose of the paper is to present a broad albeit synthetic overview of the numerous issues inherent in the above rain monitoring approach, along with a number of solutions and algorithms proposed in the literature in recent years, and ultimately to provide an exhaustive account of the current state of the art. Initially, the main relevant aspects of the satellite link are reviewed, including those related to satellite dynamics, frequency bands, signal formats, propagation channel and radio link geometry, all of which have a role in rainfall rate estimation algorithms. We discuss the impact of all these factors on rain estimation accuracy while also highlighting the substantial differences inherent in this approach in comparison with traditional rain monitoring techniques. We also review the basic formulas relating rain rate intensity to a variation of the received signal level or of the signal-to-noise ratio. Furthermore, we present a comprehensive literature survey of the main research issues for the aforementioned scenario and provide a brief outline of the algorithms proposed for their solution, highlighting their points of strength and weakness. The paper includes an extensive list of bibliographic references from which the material presented herein was taken.

Optimization of Scattering Parameters Through Numerical Investigation of One-Bit RF MEMS Switch Over Ku, K and Ka Band

Aim: Computation of loss factors for one-bit RF MEMS switch over Ku, K and Ka-band for two different insulating substrates. Objective: Numerical investigation of return loss, insertion loss, isolation loss are computed under both actuated and unactuated states for two different insulating substrates of the 1-bit RF MEMS switch, and corresponding up and down-capacitances are obtained. Methods: The unique characteristics of a 1-bit RF MEMS switch of providing higher return loss under both actuated and unactuated states and also of isolation loss with negligible insertion loss makes it as a prime candidate for phase shifter application. This is presented in this manuscript with a keen focus on improvement capability by changing transmission line width, and also of overlap area; where dielectric constant of the substrate also plays a vital role. Results: The present work exhibits very low down-capacitance over the spectrum whereas considerable amount of up-capacitance. Also when overall performance in terms of all loss parameters are considered, switch provides very low insertion loss, good return loss under actuated state and standard isolation loss. Conclusion: Reduction of transmission line width of about 33% improved the performance of the switch by increasing isolation loss. Isolation loss of -40 dB is obtained at actuated condition in higher microwave spectra for SiO2 at higher overlap area. Down capacitance of ~ 1dB is obtained which is novel as compared with other published literature. Moreover, a better combination of both return loss, isolation loss and insertion loss are reported in this present work compared with all other published data so far.

Ultra-wideband polarization- and angle-insensitive metamaterial absorber based on multilayer resistive ink

An ultra-wideband metamaterial absorber (MA) consisting of three layers of resistive ink separated by two layers of polymethacrylimide is proposed. The results of full-wave simulation show that the absorptivity is high up to 95% with a bandwidth ratio of 1:9.73 over the wide frequency range from 4.20 to 40.87 GHz, covering the whole C, X, Ku, K, and Ka bands. Moreover, the MA is insensitive to polarization and exhibits wide-angle stability, which is investigated by the full-wave simulation results as well as the analysis of multi-reflection interference theory. The fabricated prototype with a single unit cell of 0.081 g is tested using free-space measurement in an anechoic chamber, and the measured results are in good agreement with the simulation results, which prove the robustness of the design and indicates a practical application prospect of the proposed ultra-wideband MA with lightweight, simple, and compact structure.

Mechanical Design and Manufacturing of Signal Interception Antenna in Composite Material for Naval Application

This work shows the mechanical design and the FE analyses performed for an innovative naval Antenna Unit for signal interception application: more than twenty electromagnetic sensors operating from HF up to Ka band and microwave modules are integrated in a unique structure designed for a top mast installation (i.e. for naval platform). The number of constraints in terms of weight and electromagnetic transparency calls for the employment of composite materials such as glass, aramidic and carbon epoxy prepregs. Primary structures was modelled by using FE codes: both orthotropic and isotropic models have been implemented as well as non-linear contacts and bolted joints. The mast-mounted installation requires high mechanical stiffness and strength but the exposure to saline environment needs many manufacturing issues to be respected. In particular, the selection process of suitable materials and the sealing manufacturing procedures to protect them from the external agents was reported. Another key feature of the presented design concerns the electromagnetic compatibility requirement: to avoid electromagnetic emissions (EMC) generated by antenna’s internal units and to protect antenna sensors by external platform’s emitters, an appropriate stacking sequence was chosen for composite laminates with a prepreg copper mesh.

Radar altimeter waveform simulations in Antarctica with the Snow Microwave Radiative Transfer Model (SMRT)

Radar altimeters are important tools to monitor the volume of the ice sheets. The penetration of radar waves in the snowpack is a major source of uncertainty to retrieve surface elevation. To correct this effect, a better understanding of the sensitivity of the radar waveforms to snow properties is needed. Here, we present an extension of the Snow Model Radiative Transfer (SMRT) to compute radar waveforms and conduct a series of simulations on the Antarctic ice sheet. SMRT is driven by snow and surface roughness properties measured over a large latitudinal range during two field campaigns on the Antarctic Plateau. These measurements show that the snowpack is rougher, denser, less stratified, warmer, and has smaller snow grains near the coast than on the central Plateau. These simulations are compared to satellite observations in the Ka, Ku, and S bands. SMRT reproduces the observed waveforms well. For all sites and all sensors, the main contribution comes from the surface echo. The echo from snow grains (volume scattering) represents up to 40% of the amplitude of the total waveform power in the Ka band, and less at the lower frequencies. The highest amplitude is observed on the central Plateau due to the combination of higher reflection from the surface, higher scattering by snow grains in the Ka and Ku bands, and higher inter-layer reflections in the S band. In the Ka band, the wave penetrates in the snowpack less deeply on the central Plateau than near the coast because of the strong scattering caused by the larger snow grains. The opposite is observed in the S band, the wave penetrates deeper on the central Plateau because of the lower absorption due to the lower snow temperatures. The elevation bias caused by wave penetration into the snowpack show a constant bias of 10 cm for all sites in the Ka band, and a bias of 11 cm, and 21 cm in the Ku band for sites close to the coast and the central Plateau, respectively. Now that SMRT is performing waveform simulations, further work will address how the snowpack properties affect the parameters retrieved by more advanced retracking algorithms such as ICE-2 for different snow cover surfaces.

Esign of a 24GHz Rectangular Microstrip Patch Antenna for Wireless Application

The microstrip antenna required for higher frequency application is to be light in weight, easy to fabricate and small in size. As the applications in S-band and Ku-band are increasing with the increase in technology the requirement for higher data rate so the proposed work is to design a 24GHz (ka band) rectangular microstrip antenna with stripline feeding, return loss to be less than -20dB and VSWR less than 0.5. The substrate is chosen to be RT/duroid 5880 with relative permeability 2.2. it is capable of covering satellite application, telemetry. HFSS software tool is used to design the antenna.

Metamaterial‐inspired tri‐band antenna for 5G‐C and Ka band applications

AbstractThis article presents a novel tri‐band antenna design inspired by metamaterials for 5G‐C and Ka bands. The design employs an inverted U‐structured patch, a rectangular patch with E‐shape slot and a circular monopole loaded with complementary split ring resonator to achieve three operating bands with reduced overall antenna dimensions. It operates at 4.7 GHz (n79 band) in C‐band with maximum measured gain of 2.5 dB and two‐mm wave Ka bands at 28 GHz (n260 band) and 39 GHz (n261 band) with corresponding gain of 7.06 and 6.76 dB. The overall dimension of the proposed tri‐band antenna is 30 × 22 × 0.543 mm3 and the bandwidths measured are 9.04%, 14.14%, and 2.46% at 4.7 GHz, 28 GHz, and 39 GHz, respectively. The experimented results are close to simulated ones.

Ramalan Pelemahan Hujan di Malaysia Menggunakan Data TRMM

Rainfall is observed as a main contributing factor in the degradation of electromagnetic signal for frequency above 10GHz through absorption and scattering, resulting a weak or fading signal. Broadcasting satellite service operates in Ku band (12GHz to 18GHz) is widely used has caused congestion, therefore Ka band is exploited to meet the customer demand. However, the rain attenuation effects on Ka band are higher than Ku band. In this study, the rain attenuation effects of Ka band downlink signal of the Measat-5 satellite are analysed to assess the rain fade properties using TRMM 3B42 data for eleven (11) years from January 2009 until December 2019 for fourteen study areas. All data are processed to obtain 1-minute integration data using Segal Model and the prediction of rain attenuation are implemented using ITU-R P.618-13 model. This study summarizes, there are three, (3) main factors that influence the impact of rain attenuation, namely the value of specific attenuation, receiver station altitude and elevation angle of the satellite signal receiver antenna. The signal availability impact on rain attenuation shows, eight (8) study areas could receive 99.90% of service readiness, while the rest at 99.00% to comply with the ITU unavailability requirements. Overall, the value of rain attenuation on the West Coast of Peninsular Malaysia is smaller than the East Coast of Peninsular Malaysia and the value of rain attenuation in the East Coast of Peninsular Malaysia is closer to the value of rain attenuation in Sabah and Sarawak.

A Study on Measurement Accuracy and Required Time based on SCPI of Power Meter in Ka Band

A Study on Measurement Accuracy and Required Time based on SCPI of Power Meter in Ka Band

Mobile Ka-Band Polarimetric Doppler Radar Observations of Wildfire Smoke Plumes

ABSTRACTRemote sensing techniques have been used to study and track wildfire smoke plume structure and evolution; however, knowledge gaps remain because of the limited availability of observational datasets aimed at understanding fine-scale fire–atmosphere interactions and plume microphysics. Meteorological radars have been used to investigate the evolution of plume rise in time and space, but highly resolved plume observations are limited. In this study, we present a new mobile millimeter-wave (Ka band) Doppler radar system acquired to sample the fine-scale kinematics and microphysical properties of active wildfire smoke plumes from both wildfires and large prescribed fires. Four field deployments were conducted in autumn of 2019 during two wildfires in California and one prescribed burn in Utah. Radar parameters investigated in this study include reflectivity, radial velocity, Doppler spectrum width, differential reflectivity ZDR, and copolarized correlation coefficient ρHV. Observed radar reflectivity ranged between −15 and 20 dBZ in plume, and radial velocity ranged from 0 to 16 m s−1. Dual-polarimetric observations revealed that scattering sources within wildfire plumes are primarily nonspherical and oblate-shaped targets as indicated by ZDR values measuring above 0 and ρHV values below 0.8 within the plume. Doppler spectrum width maxima were located near the updraft core region and were associated with radar reflectivity maxima.

Performance analysis for the forward link of multiuser satellite communication systems

SummaryBroad‐band satellite communication is an indispensable method to provide seamless connectivity for people especially in remote areas. This paper analyzes the performance of the forward link of a multiuser satellite system operating in Ka band, where a gateway delivers signal to a satellite that forwards the amplified signal to multiple users on the ground. By assuming that satellite links experience double lognormal fading due to rain attenuation and taking the effects of antenna pattern and path loss into account, we first exploit the opportunistic user scheduling (OUS) scheme to obtain the maximal output signal‐to‐noise ratio (SNR) expression of the satellite system. Then, the analytical expressions for both outage probability (OP) and ergodic capacity (EC) of the considered satellite system are derived. Finally, simulation results demonstrate the validity of the theoretical analysis and the superiority of the OUS scheme in comparison with round‐robin scheme.

Lightweight PVDF/γ-Fe2O3/PANI foam for efficient broadband microwave absorption in the K and Ka bands

Lightweight magnetic polyvinylidene fluoride/ferric oxide/polyaniline nanofiber (PVDF/γ-Fe2O3/PANI) foams with excellent microwave absorption performance in the K (18–26.5 GHz) and Ka (26.5–40 GHz) bands were successfully fabricated using heat shaping and a sacrificial templating method. By varying the diameter of the PANI nanofibers (50, 100 or 500 nm), the electromagnetic microwave absorption (EMWA) properties of the composite foams could be precisely tuned. PVDF/γ-Fe2O3/PANI-50 foams with a PANI nanofiber diameter ~50 nm delivered the best all-round EMWA performance, demonstrated by minimum reflection loss (RLmin) values of −38.7 dB at 26.33 GHz and −38.4 dB at 28.9 GHz at an absorber thickness of 2.5 mm. Further, the effective absorption bandwidth (EAB) of the composite could be adjusted to cover the entire 18–40 GHz frequency region simply by changing the absorber thickness (from 1.5 to 3.5 mm). This work introduces a simple low cost strategy for designing high performance microwave absorbers.

Broadband Reflective Polarization Rotator Built on Single Substrate

A broadband polarization rotator built on single substrate is presented in this work. The device is designed for operation in the K and Ka bands. A slant array is used to achieve polarization rotation by 90° in a reflective manner. Broadband has been obtained, with the operation frequency range covering 15–45 GHz for 3 dB criteria, which is almost 100% fractional bandwidth. In addition, the insertion loss is less than 0.3 dB over a moderate broad incident angle from 0°–20°. Furthermore, the polarization conversion ratio can be as high as 0.95. By using a bi-static method, the fabricated prototype is measured, and the measured results demonstrate satisfactory agreement with the simulation ones. In comparison with other reflective designs in the literature, this design provides good bandwidth as well as polarization conversion ratio. Miniaturization can be investigated to increase the angular stability.

Wideband hyperbolic flat lens in the Ka-band based on 3D-printing and transformation optics

A flat wideband lens antenna operating in the Ka band is presented. The design corresponds to the transformation of a hyperbolic lens via quasi-optic transformation into a flat lens. The implementation of the lens is made using 3D printing technology as it allows cheap and precise manufacturing of the complicated shapes obtained with the transformation. The required refractive indices are calculated and implemented with varying infill percentages of the used filaments in each transformed layer. The experimental results show excellent agreement with the simulations, including low losses. The presented design is a low-cost antenna with the measured gain above 23 dBi in the whole Ka band (26.5–40 GHz).

Multiband isolator based on a coplanar metaline

This study presents for the first time the feasibility of a coplanar isolator using YIG material for applications in the Ku, K and Ka bands. The proposed structure is an asymmetric coplanar waveguide with a transverse array of unopened slots etched on a ground plane. Such structures are characterized by several cut-off frequencies on the transmission parameters. With a low dc magnetic field of 72 kAm−1 applied along with the slots, significant nonreciprocal effects greater than 20, 19 and 29 dB are obtained at 13.95, 23.39 and 39.61 GHz, respectively. The proposed structure can be used as a multiband isolator for microwave applications. The low biasing field of this multiband isolator and its compactness (88 mm2) are its main advantages, which makes this structure particularly suitable for integration.

Design of a Dual Band SNG Metamaterial Based Antenna for LTE 46/WLAN and Ka-Band Applications

The non-existing properties of the metamaterial surfaces can be utilized to improve the antenna radiation characteristics. In this article, a design and performance analysis of a Single Negative (SNG) metamaterial based antenna is imparted for LTE 46/WLAN and Ka-band (like in satellite communication for the receiving side) applications. The unit cell of the metamaterial surface exhibits negative permittivity and positive permeability; yielding a high magnitude positive refractive index, is used to improve and analyze the performance of the proposed monopole antenna element. The proposed SNG based antenna covers a -10 dB bandwidth from 5.35-5.69 GHz (LTE 46/WLAN) and 17.81-20.67 GHz (Ka-band). The total size of the proposed antenna element is 20.2×28.4 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> while a 2×3 SNG metamaterial surface is used at the back of the antenna element which improves the gain from 4.52 dB to 9.13 dB for the desired Ka band and 1.17 to 5.04 dB for the LTE 46/WLAN band. Furthermore, for the LTE 46/WLAN frequency band, the impedance matching also gets better, resulting in the return loss improvement from -11 dB to -32.4 dB. Moreover, the radiation efficiency is also improved by more than 10 % for the Ka band after employing the SNG metamaterial surface. The measured results fall in good agreement with the simulated one and make the proposed SNG metamaterial based antenna design competent for the LTE 46/WLAN and Ka-band (like in satellite communication for the receiving side) applications.