Showing papers on "Ka band published in 2011"

Development of a $Ka$ -Band Wideband Circularly Polarized 64-Element Microstrip Antenna Array With Double Application of the Sequential Rotation Feeding Technique

Abstract: A novel -band wideband circularly polarized 64-element microstrip antenna array is presented in this letter. It is developed with double application of the sequential rotation feeding technique. The array employs corner-truncated microstrip patches as the basic element, and then a four-element array as the subarray. By applying the sequential rotation technique twice to design the feed networks, a full 64-element array with good performance is obtained. A prototype of the full array was constructed and tested. The measurement results show that both the reflection coefficient of less than 10 dB and axial ratio of less than 3 dB have been achieved over a frequency band of 27-31 GHz; this corresponds to a wide bandwidth of 13.8%. Due to its planar configuration, the proposed array can find good applications in aerospace, radar, and communication systems.

A triple-frequency approach to retrieve microphysical snowfall parameters

Abstract: [1] Backscattering and extinction properties of various snow particle models are studied for three typical cloud radar frequency ranges, namely Ku band, Ka band, and W band, both in terms of their individual scattering properties as well as averaged over size distributions. Models studied include soft spheres, randomly oriented pristine nonspherical particles and complex aggregates, as well as horizontally aligned spheroids. It is shown that the concurrent use of Ku/Ka band and Ka/W band dual wavelength ratios (DWR) allows for a separation of different snow particle habits. It is further shown that triple-frequency approaches constrain the slope parameter of exponential size distributions more tightly than conventional single DWR approaches can. Uncertainties introduced by unknown mass-size relations for different snow particle habits remain a challenge when mass-related quantities are to be derived. Attenuation by snow, especially at W band, is found to potentially alter these results, albeit moderately, without affecting the general conclusions. Sensitivity studies performed with respect to cutoffs in the simulated size distribution highlight potential benefits of including larger particles in future scattering databases.

Dynamic Power Allocation for Broadband Multi-Beam Satellite Communication Networks

Abstract: Broadband satellite communication networks, operating at Ka band and above, play a significant role to worldwide telecommunication infrastructure, providing backhaul and direct-to-user satellite services Rain attenuation at these frequencies is the most dominant impairment factor that degrades the performance of the system The dynamic reconfiguration of multi-beam satellite antennas has recently been proposed as a fading mitigation technique In this paper, the problem of finding the power allocation among the beams of such an antenna, aiming that the number of subscribers not receiving the desired quality of service is minimized is addressed for a satellite communications system with a GEO satellite serving fixed earth terminals An algorithm for the dynamic power allocation using a physical-mathematical model for rain attenuation prediction is proposed Extended simulation results highlight the improvement of the dynamic scheme over the static allocation based on long term rain attenuation characteristics

Broadband phase shifter using air holes in Substrate Integrated Waveguide

Abstract: This paper presents a novel configuration of broadband phase shifter designed with Substrate Integrated Waveguide (SIW) technique. The phase shift mechanism is based on the synthesis of a low dielectric slab in the middle of the SIW using an array of air holes. A simple design technique is proposed where unit cells are simply cascaded, which leads to the summation of their phase shift. The number of holes, their diameter and their spacing can be adjusted in order to obtain the required phase shift, thus giving a very flexible structure. Two different phase shifters, both giving a phase shift of 30° are designed and simulated. Finally, an experimental validation in the Ka band (26.5 to 40 GHz) is presented for both circuits.

Design and Experimental Study of a Ka-band Gyro-TWT With Periodic Dielectric Loaded Circuits

Abstract: The design and experimental study of a Ka-band gyrotron traveling-wave tube (gyro-TWT) amplifier operating in the circular TE01 mode at the fundamental cyclotron harmonic are presented. A periodic dielectric loaded structure is adopted in the interaction circuit of the gyro-TWT to suppress spurious modes TE11 and TE21. A saturated peak power of 156 kW is obtained with a saturated gain of 44 dB, an efficiency of 23.3% in an operating voltage of 67 kV, an electron beam current of 10 A, and a -3-dB bandwidth of 1.8 GHz (~5.2%). The gyro-TWT is found to be zero-drive stable at these operating points and to be characteristic of the excellent purity of the signal frequency spectrum in the operating frequency range.

Experimental investigation of a Ka band high power millimeter wave generator operated at low guiding magnetic field

Abstract: An overmoded slow wave type Ka band generator is investigated experimentally to produce high power millimeter waves in this paper. The experiments were carried out at the TORCH-01 accelerator. The produced microwave frequency was measured by dispersive line method, and the power was estimated by integrating over the radiation pattern at far field. With relatively low guiding magnetic field of 0.8 T and diode voltage and beam current of 590 kV and 5.2 kA, respectively, a 33.56 GHz millimeter wave with an output power of 320 MW was generated, and the microwave mode was quasi-TM01 mode.

Liquid water content estimates using simultaneous S and Ka band radar measurements

Abstract: [1] A technique for the estimation of total liquid water content (LWC; the sum of cloud water and rainwater contents) using simultaneous S and Ka band scanning radar observations is proposed and tested using the National Center for Atmospheric Research simultaneous S band and Ka band dual-polarimetric (S-PolKa) radar system. The sources of error for this wavelength pair are evaluated, and the methods to mitigate them are discussed. The results are LWC estimates at each radar volume that are equivalent to specifying a reflectivity (Z) – LWC relation constrained by the measured attenuation over 2 km radar ray segments. Because the radars are scanning, the LWC can be mapped out over the spatial volume and temporal evolution of the clouds. The method produces reasonable results that qualitatively compare well to in situ aircraft observations.

Propagation in the Ka Band: Experimental Characterization for Satellite Applications

Abstract: The use of the Ka band (30/20 GHz) in satellite-communication systems is expected to grow in the next few years, with the launches and planned launches of more than 10 satellites in 2010 and 2011 that include some Ka-band capacity. New technical standards, such as DVB-S2 and OVB-RCS, can be used in this band. A better knowledge of the channel characteristics is required, as well as experimental time series of attenuation. A propagation experiment is being carried out in Madrid, Spain, with the objective of characterizing the propagation channel in the downlink subband. Propagation results are related to meteorological data obtained from co-located instruments. Results obtained after two years of the experiment are presented in this paper. Rain attenuation is the main propagation impairment in this band. That is why rain-propagation effects are analyzed in more detail, although other propagation effects are also considered, as well as their relative importance.

Inductive Tri-Band Double Element FSS for Space Applications

Abstract: In this contribution we propose the design of an inductive Frequency Selective Surface (FSS) with double resonant elements aimed at the achievement of a simple well-performing, dielectric-free, space fllter screen able to separate the Ku band from the Ka band. The FSS performance is compared to that of a typical double ring FSS which major drawback is the use of a dielectric substrate that leads to unavoidable additional transmission losses and makes the dichroic mirror more complex with respect to a simple single perforated screen. For all applications in which the FSS is asked to be as simple as possible and the transmission losses speciflcations are severe, the Inductive FSS Double Resonant Elements here proposed turns out to be an interesting alternative to typical Double Ring FSS.

W-band frequency synthesis using a Ka-band PLL and two different frequency triplers

Abstract: Two chips for 96GHz frequency generation incorporating the same Ka-band PLL and (1) an injection-locked frequency tripler (ILFT); (2) a harmonic-based frequency tripler (HBFT) in 0.18µm SiGe BiCMOS are presented. The ILFT and HBFT preceded by the same Kaband PLL achieve measured closed-loop phase noise of −93dBc/Hz and −92dBc/Hz at 1MHz offset, respectively, from a reference frequency of 125MHz. The measured reference spurs are <−52dBc for both prototypes. Both chips have the same power consumption of 140mW from 1.8V/2.5V supplies. To the authors' best knowledge, this work presents the first implementation of an injection-locked-based frequency multiplier in SiGe BiCMOS process and performs a comparative study between two different triplers.

A dual circular combined K/Ka-band RF sensing feed chain for multi beam satellite antennas

Abstract: This paper presents the design process as well as the performance and test results achieved for a novel combined transmit (Tx)/receive (Rx) feed chain with RF sensing (RFS) capabilities This modular feed chain is useable for multiple spot beam satellite antennas with overlapping beams in Ka-band. We describe an efficient EM-field/circuit co-optimization technique, which uses the advantages of both, EM-field solvers and circuit simulators. With this approach a fast and accurate design of complex feed chain systems, comprised of a high number of different and interacting waveguide components, as part of a multi-beam satellite antenna is possible. The feed chain was manufactured using conventional techniques. The measurement results are in a very good agreement with the simulation results.

Future developments trend for Ku and Ka antenna for satcom on the move

Abstract: This document presents the state-of-the-art of TeS Ku band antennas for mobile satellite communications on board high speed trains and ground vehicles, and his evolution in terms of Ku band antenna performances improvement and upgrade to Ka band terminals.

Ka band active phased array antenna system for satellite communication on the move terminal

Abstract: In the recent years SELEX Communications has grown his experience in Phased Array Antennas, developing an X-Band steerable Array in circular polarization. Based on this consolidated experience, Selex is developing a Ka-band system, able to electronic beam steering in elevation, and mechanical rotation in azimuth.

Demonstration of multi-Gbps data rates at Ka-band using software-defined modem and broadband high power amplifier for space communications

Abstract: The paper presents the first ever research and experimental results regarding the combination of a software-defined multi-Gbps modem and a broadband high power space amplifier when tested with an extended form of the industry standard DVB-S2 and LDPC rate 9/10 FEC codec. The modem supports waveforms including QPSK, 8-PSK, 16-APSK, 32-APSK, 64-APSK, and 128-QAM. The broadband high power amplifier is a space qualified traveling-wave tube (TWT), which has a passband greater than 3 GHz at 33 GHz, output power of 200 watts and efficiency greater than 60%. The modem and the TWTA together enabled an unprecedented data rate at 20 Gbps with low BER of 10−9. The presented results include a plot of the received waveform constellation, BER vs. E b /N 0 and implementation loss for each of the modulation types tested. The above results when included in an RF link budget analysis show that NASA's payload data rate can be increased by an order of magnitude (>10X) over current state-of-practice, limited only by the spacecraft EIRP, ground receiver G/T, range, and available spectrum or bandwidth.

Multi-Band Digital-RF Receiver

Abstract: A software radio receiver that can be programmed to operate in multiple wide frequency bands is required for many communication and intelligence applications. We have designed a variety of multi-band receivers, comprising a set of band-specific analog-to-digital converters (ADCs) for direct digitization of RF bands and a digital switch matrix for band selection, in two flavors: as a single superconductor integrated circuit chip and also as a multi-chip module. In addition to the ADCs and the switch, these include a 1:16 deserializer and output drivers to facilitate transport of the digitized RF data to room temperature electronics for further processing and analysis. In the single IC flavor, up to four bandpass delta-sigma ADCs minimizing quantization noise in their respective bands were integrated on the same chip and operated at clock rates up to 20 GHz. In the multi-chip module (MCM) implementation, a 1-cm × 1-cm universal active carrier was designed to accommodate any two 2.5-mm × 2.5-mm flipped chips, each containing a single ADC front-end. This standardized approach facilitates customization of two-band ADCs by selecting from a growing library of ADC front-ends, which currently cover bands ranging from HF (0-30 MHz) to Ka-band (20-21 GHz). These Multi-band MCMs and single chip ADC's were fabricated, assembled and tested.

Compact Shaped Dual-Reflector System For Military Ka-band SATCOM on the move

Abstract: A compact, on the move, SATCOM terminal for the military Ka-band has been successfully designed, implemented and tested. It allows two-way communications at Ka-band while the vehicle is in motion over rough terrains. A compact, complex, tracking system ensures that the antenna keeps pointing at the satellite while the vehicle is on the move.

A Ka-band MMIC Doherty Power Amplifier using GaAs pHEMT technology

Abstract: A fully integrated Ka-band Monolithic microwave integrated circuit (MMIC) Doherty Power Amplifier (PA) is designed and demonstrated in this paper. The proposed Doherty PA maily consists of a Lange coupler, carrier amplifier branch, peaking amplifier branch and impedance transformer network. offset lines are introduced in each branch to overcome the inherent defects of conventional Doherty PA. Electromagnetic (EM) simulated results show the proposed Doherty PA obtains a small signal gain over 5.5dB from 31GHz to 35GHz with a compact die size of 2mm×1.7mm. Power added efficiency (PAE) is over 19.8% at 6dB back-off with saturated output power over 26dBm.

A tool for synthesizing rain attenuation time series in LEO Earth observation satellite downlinks at Ka band

Abstract: Rapidly increasing requirements for Earth Observation (EO) data via Low Earth Orbit (LEO) satellites push operation of the corresponding systems to higher frequency bands and particularly the Ka band, where more spectrum is available but atmospheric effects combined with the motion of the LEO satellite form a new propagation environment. Unfortunately, due to the lack of available experimental data, it seems difficult to characterize this new propagation environment. Therefore, similar to recent modeling efforts, in this work we rely on mature ideas coming from fixed geostationary (GEO) satellite channels operating in the same band making reasonable assumptions and modifications along the course. Specifically, the purpose of this contribution is to provide a tool for synthesizing rain attenuation time series in LEO EO satellite downlinks at Ka band.

Design of a Dual-Band Rotary Joint Operating in $X$ - and $Ka$ -Bands

Abstract: This paper illustrates the design guidelines and main features of a dual-channel rotary joint, operating in X- and Ka-bands. The core of the proposed solution is the double transducer between X and Ka rectangular waveguides and a nested coaxial waveguide, which shows very good performance in both bands.

Rain rate and rain attenuation estimation for Ku band satellite communications over Sri Lanka

Abstract: Rain attenuation is the dominant propagation impairment at microwave frequencies, which varies for different countries/regions and essential to quantify correctly for satellite systems design. There was a consistent need to estimate and compare the practical rain fade margin with existing model estimations for Sri Lanka. This paper presents the rain rate and rain attenuation estimation for Ku band satellite signals by using established models as well as actual propagation measurements. Rainfall data over three years period is considered to estimate the highest rain rate distribution. Two satellite downlinks from Intelsat-12 & INSAT-4B are used for practical measurements and three rain attenuation models (ITU-R, DAH and Karasawa) are used to calculate the respective model estimations. It is found that the rain rate which exceeded 0.01% of cumulative time for an average year (R 0.01 ) as 105mm/h and resulted specific rain attenuation (γ 0.01 ) is 2.8dB/km. Ka band rain attenuation for the same links is predicted using ITU-R frequency scaling method. Among the empirical models considered, DAH model gives overestimated results for the local context while the Karasawa model gives best-fit compliance with the measured path attenuation data.

In-Line Pure ${\rm E}$ -Plane Waveguide Band-Stop Filter With Wide Spurious-Free Response

Abstract: A new compact pure E-plane waveguide structure is proposed for coupling band-rejection cavities to the main rectangular waveguide in bandstop in-line filters. This coupling structure reduces drastically the unwanted resonances in filters with a very large pass band requirement. Moreover, it has some additional advantages. First, unlike typical inductive irises, large coupling coefficients can be implemented. Second, a pure E-plane configuration is achieved, which simplifies the manufacturing and also reduces significantly the computational effort. Third, in the design, by means of distributed model circuits, the rejection cavities are individually designed and connected by phase shifters maintaining the E-plane layout. Experimental validation is demonstrated by a pseudoelliptic fifth-order bandstop filter centered at 28 GHz and 2% fractional stop band. It is free of spurious resonances in the full Ka-band.

Multiple Feed per Beam networks for Ka-band satellite communication systems in LTCC technology

Abstract: Modern communication satellites need to cover very large service areas with local variations in required transmission capacity. To allow for efficient frequency re-use and bandwidth to local beam allocation a Multiple Feed per Beam (MFB) concept with a four color topology may be used to illuminate the reflector antenna. However, in current systems the size of the feed network requires the usage of one reflector antenna for each color. In this paper a scalable and size-efficient LTCC power divider network is presented, that will form the basis of a MFB network, which enables the use of a single reflector antenna for all four colors. Thus, the payload of the satellite is significantly reduced.

Ka-band I/Q modulator Multi-Chip Module for high data rate communications

Abstract: This paper describes the development and test results of a flight qualified, hermetic I/Q modulator Multi-Chip Module (MCM) with X-band input and Ka-band output for either Tracking and Data Relay Satellite System (TDRSS) or Deep Space Network (DSN) high data rate communications applications. The module is 0.9″ wide by 1.7″ long without the attachable coaxial connector. It draws <500 mW of DC power. A Ka-band modulator MMIC previously developed by the Johns Hopkins University Applied Physics Laboratory (JHU/APL) provides the direct I/Q modulating function in the module. A Commercial Off The Shelf (COTS) MMIC frequency multiplier provides either a multiply-by-three or a multiply-by-four function for the upconversion of the X-band carrier to one of the Ka-band output frequencies of choice. The multi-chip module is configurable for the desired frequency band during fabrication by installing the corresponding band-pass filter. This filter, along with the biasing of the multiplier MMIC, passes the upconverted carrier to the I/Q modulator. A COTS MMIC broadband amplifier is used following the modulator to boost the output signal level to approximately +10dBm range, suitable for driving an external SSPA or TWTA. Chip attenuators are located between each function block for level setting as well as temperature compensation. An innovative package was designed to house the circuits described. Both the TDRSS and DSN versions of this upconverting direct modulation module have been fully tested and successfully implemented in the Ka-band Exciter of both the S/Ka-band and X/Ka-band Frontier Radio developed by JHU/APL for NASA. A data rate of up to 200 Mbps has been demonstrated during radio test, with current efforts targeting beyond 300 Mbps. 1 2

High-efficiency Ka band microwave monolithic integrated circuit frequency tripler using lumped-element balun

Abstract: This work describes a lumped-element balun for use in a miniature, coplanar waveguide frequency tripler pseudomorphic high electron mobility transistor microwave monolithic integrated circuit. The measurement results of the balun show a 1-dB gain balance and a 10 degrees phase balance from 11.6 to 13 GHz. It was used in the design of a 36-GHz monolithic tripler at the input port. A resonant inductor and capacitor (LC) filter was used to eliminate the fundamental frequency and a phase delay line was employed to enhance the third harmonic in the tripler. At 36 GHz, the tripler achieved as minimum conversion loss of 6.7 dB at an input power of 13 dBm; the suppressions of the fundamental and second harmonic frequencies were 24 and 27 dB, respectively.

Ka-band rectangular waveguide power dividers

Abstract: Waveguide T-junction and directional couplers are widely used in microwave/millimeter wave systems, because its circuit is simply and easily to be designed and fabricated. In this paper, a ka-band E-plane rectangular waveguide power divider is proposed and optimized. The first level of the network is the T-junction, which can halve the power for the first time, and the second level are two 3dB directional couplers, which are designed accordingly to the couple of electromagnetic field between seven waveguide slots. It is developed with excellent isolation between output ports. The good transmission characteristic can be obtained at ka band.

Design and Optimization of Spherical Lens Antennas Including Practical Feed Models

Abstract: A novel approach for the design and optimization of spherical lens antennas (SLAs) including practical feed model (PFM) is proposed. The vector spherical wave function expansions (VSWE) combined with difierential evolution (DE) algorithm is adopted for the optimal design of SLAs. Moreover, the near-fleld aperture distributions of a Ku band dielectric loaded horn feed and a Ka band corrugated horn feed were obtained using the full wave simulation and were then taken into account in the DE optimization. The performances of the optimized 2-layer design are compared with previous works, higher directivity is obtained. Additionally, the radiation characteristics of an optimized SLA are presented, and numerical results of a 650mm diameter 2-layer hemispherical lens antenna (HLA) with ground plane are compared to the experimental results, and good agreements are obtained. An investigation of the in∞uence of the various lens-to-feed distances as well as aperture sizes of SLA on the aperture e-ciency for a 2-layer design is also proposed.

Design of a Ka-Band LNA for SoC space-based millimeter-wave radiometers

Abstract: This paper presents the design of a Ka-band two-stage LNA for System-on-Chip (SoC) space-based radiometers. The circuit features proper self-adaptive compensation to achieve robustness against temperature variations. The technology selected is a 250nm SiGe BiCMOS technology from IHP foundry. This selection is motivated by the space qualification of the above process, which is under development at IHP. An automatic design procedure for inductors has been developed on purpose. Preliminary simulations of the designed LNA show a conversion gain of 24 dB at 31.4 GHz with a noise figure of 3.5 dB. The obtained sensitivity is very promising for total power radiometric applications.

Multimode monopulse tracking feed with dual-band potential for land-mobile satellite communications in Ka-band

Abstract: The growing interest in bi-directional mobile satellite communications in Ka-band necessitates the development of dedicated antenna systems and feeds. In this paper we describe an operational feeding structure for a Cassegrain satellite reflector antenna which facilitates a multimode monopulse tracking system for circular polarisation at the satellite downlink frequency of 20 GHz. The basic principle can be extended to dual-band functionality, to cover the uplink at 30 GHz as well. This work contributes to the development of a satellite terminal for mobile communications in disaster scenarios [1], [2].

Ka-band self-biased monolithic gaas pHEMT low noise amplifier

Abstract: A 32 −40 GHz monolithic low noise three stage amplifier has been developed using an GaAs/InGaAs/AlGaAs pseudomorphic HEMT with a gate length of 0.15um. In order to reduce the chip size and circuit's complexity, self-Biased technology has been applied. The chip only needs two DC Pads. Resistive matching technologies have been used to enhance the electrical specifications like return loss and gain flatness. The simulated data shows better than 2.5 dB of noise figure with an associated gain of more than 20dB over the frequency band of 32–40 GHz. Additionaly, the input/output return losses is better than 14.8 dB and the P1dBm more than 9.8dBm. The layout size is 2.1 × 0.8 mm.