X-band Antenna Research Articles

X-Band Phased Array Antenna Using Ferroelectric (Ba,Sr)TiO3 Coplanar Waveguide Phase Shifter

A phased array antenna was fabricated using fourelement ferroelectric phase shifters with a coplanar waveguide (CPW) transmission line structure based on a Ba0.6Sr0.4TiO3(BST)/MgO structure. Epitaxial BST films were deposited on MgO (001) substrates by pulsed laser deposition. To attain the large differential phase shift and small losses for a ferroelectric CPW phase shifter, an impedance-matching-part adding technique between the effective transmission line and connecting cable was used. The return loss and insertion loss for this techniqueadapted BST CPW device were improved with respect to those for a normal BST CPW device. For an X-band phased array antenna system consisting of ferroelectric BST CPW phase shifters, power divider, dc block, patch antenna, and programmed dc power, the steering beam could be tilted by 15 ° in either direction.

Integrated Electro-Absorption Modulation DFB Laser Based Optical True Time-Delay Feeder for X-Band Phased Array Antennas

A 4-bit optical true-time-delay feeder incorporating an integrated electro-absorption modulation distributed feedback (DFB) laser for X-band phased array antennas is demonstrated. The integrated electro-absorption modulation DFB laser is an attractive device that provides a very compact, low-cost solution for optical true-time-delay systems. The variable delay line is constructed by cascaded magneto-optic switches, which have fast switching speed. The integrated electro-absorption modulation DFB laser system shows high signal-to-noise ratio up to 58dB, and the transmission performance of the system is relatively good and accredited.

Accuracy assessment of interferometric digital elevation models derived from the Shuttle Radar Topography Mission X- and C-band data in a test area with rolling topography and moderate forest cover

In February 2000, the Shuttle Radar Topography Mission (SRTM) mapped large areas of the global landmass using two radar systems operating simultaneously in X and C band. The radar mapping instrument consisted of modified versions of the SIR-C C-band and X-band radars flown on the shuttle in 1994. Modifications included a 60-m retractable boom, with C-band and X-band receive-only antennas attached to the boom's end. High-accuracy metrology systems were added to measure position and attitude of the shuttle and the positions of the boom antennas. The dual apertures at each band form radar interferometers suitable for making high-accuracy topographic maps of the Earth. The C-band data set is being processed by JPL for the archives of the National Imagery and Mapping Agency and the National Aeronautics and Space Administration. The X-band data set is processed and distributed at DLR, Germany. This paper deals with the accuracy assessments of the interferometric DEMs derived from the X- and C-band synthetic aperture radar systems over a testfield with rolling topography and moderate forest cover using the reference DEM digitized from the topographic maps of 1:25,000 scale. Obtained results for the two interferometric DEMs are similar and lie in the range of 10–11 m. The accuracy of SRTM X- and C-band DEMs was also checked against ground control points measured by differential GPS, and the rms height errors were found to be about 9 m, which confirms the results based on the reference DEM.

History of the mera antenna

Texas Instruments began development of the molecular electronics for radar applications (MERA) solid-state X-band phased-array antenna for the U.S. Air Force Avionics Laboratory in 1964. Its development is very briefly mentioned.

MEMS 2-Bit Phase-Shifter Failure Mode and Reliability Considerations for Large>tex<$X$>/tex<-Band Arrays

RF microelectromechanical systems (MEMS) switch technology used in the fabrication of phase-shifter circuits is examined from the perspective of failure mode and reliability implications on the performance of large X-band array antennas. Amplitude and phase-state failure probability density functions (pdfs) conditioned on switch probability of failure are formulated for both the hybrid-T (switched line) and coupled-line phase-shifter circuit topologies. The pdfs are used to assess the phase-shifter failure impact on overall array level performance in terms of gain loss and the increase in RMS sidelobe level. Reliability and lifetime implications are addressed through considering a probability of switch failure that increases with cycling. The phase-shifter lifetime switching considerations are related to radar system lifetime beam switching requirements consistent with plausible radar system applications. The key findings are that RF MEMS switch mean time to failure /spl sim/125000 h or longer, consistent with /spl sim/100-125 phase-shifter state switches per second (/spl sim/10/sup 11/ switch operations), are reasonable expectations for RF MEMS phase-shifter technology to meet in order to be considered viable for a broad range of array antenna applications.

Continuously delay-time tunable-waveguide hologram module for X-band phased-array antenna

Tunable optical true time-delay modules based on a dispersive waveguide hologram are presented to provide continuous radio-frequency beam scanning for an X-band (8-12 GHz) phased-array antenna system. The true time-delay modules operating in the 1550-nm region were fabricated with continuously tunable time delays from 5 to 64 ps. The far-field radiation patterns were measured with different delay combinations and the continuity of the scanning angles from 35/spl deg/ to 55/spl deg/ was experimentally confirmed at X-band frequencies.

Efficient large-domain MoM solutions to electrically large practical EM problems

A numerical method is presented for the analysis and design of a wide variety of electromagnetic (EM) structures consisting of dielectric and conducting parts of arbitrary shapes. The method is based on the integral-equation formulation in frequency domain, and represents a large domain (high-order expansion) Galerkin-type version of the method of moments (MoM). The method is formulated in two versions concerning the type of the equivalence (volume and surface) utilized in the treatment of the dielectric parts of the structure. The generality, versatility, accuracy, and practicality of the method and code are demonstrated on four very diverse, electrically large, and complex EM problems. The examples are: an X-band reflector antenna modeled after a bat's ear, which is about 11/spl lambda//sup 3/ large at X-band; a broad-band (0.5-4.5 GHz) nested array of crossed loaded dipoles; an EM system consisting of a dipole antenna and a human body, and a broad-band (1-5 GHz) microstrip-fed Vivaldi antenna with a high-permittivity dielectric substrate. The central processing unit times with a modest personal computer are on the order of several minutes for a single-frequency application.

Wavelength-selective true time delay for optical control of phased-array antenna

Performance of an optically controlled phased-array antenna system employing novel single-chip optical wavelength selective true time-delay devices is reported. High-resolution time-delays are demonstrated using integrated delay lines. Extension to two-dimensional (2-D) antenna arrays with independent control of azimuth and elevation by using mid-stage optical wavelength conversion is proposed and demonstrated. An optical true-time-delay steered two-element X-band antenna was assembled to verify the wide instantaneous bandwidth operation.

X-band antenna mixers based on striped patch antennas excited by folded slots

This letter presents integrated antenna mixers using simple and striped patches excited by folded slots. Two Schottky-barrier diodes are inserted in the excitation slot of the antenna to achieve the mixing function. This monolithic system acts simultaneously as an antenna, where the RF is coupled quasioptically through the patch, and as a mixer where the LO frequency pumps the diodes via a coplanar waveguide (CPW) slot line balun. An X-band realization (RF=8.7 GHz, LO=7.3 GHz) has given a single-sideband (SSB) conversion loss of 3.5 dB with high levels of LO-to-IF and RF-to-LO isolation. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 333–336, 1999.

X-band brick wall antenna fed by CPW

A brick wall antenna fed by a coplanar waveguide is introduced. This antenna can be considered as an eleven element array of reduced size. Analysis is carried out both theoretically and experimentally. The proposed antenna is designed to work in the X-band /spl sim/9.5 GHz. The return loss, radiation pattern, and antenna gain of the proposed antenna are presented and briefly discussed. The antenna has several advantages, such as ease of fabrication, good control of input impedance, small cross polarisation level, and high directivity.

Wide-band multiport antenna characterization by polarimetric RCS measurements

A theoretical description of the scattering of multiport antennas is derived in accordance with the polarimetric radar target characterization. For two-port antennas with dual linear orthogonal polarization, a procedure for the determination of the antenna mode scattering parameters and the structural scattering parameters of the complete polarimetric antenna scattering matrix [S] is given. A measurement setup and experimental results of wide-band polarimetric radar cross section (RCS) antenna measurements are presented. For two-port antennas, in total, 24 unknowns have to be determined. The load variation method is used. The polarimetric RCS antenna measurement is especially advantageous over a wide bandwidth; for example 2-40 GHz with only one single calibration. From the antenna scattering matrix [S], the antenna parameters like polarimetric gain, optimum gain, gain bandwidth, wave admittance, structural scattering, etc., are derived. Results are shown for an X-band horn antenna and a 2-18-GHz dual linearly polarized horn. The measurement technique and evaluation gives the most complete and very accurate information about antenna radiation, antenna characteristics, and scattering obtainable with one single measurement setup. Some quantities determined here, like the maximum available gain and the polarization characteristics, are difficult to access with standard transmission measurements. No cable from the antenna to the receiver is necessary. This helps avoid some difficulties usually experienced at low signal levels.

An X-band self-mixing oscillator antenna for transceiver and spatial power-combining applications

The general theory for oscillator and mixer design is applied to develop an X-band self-mixing oscillator antenna. The antenna uses a Gunn diode as the active device that provides the oscillations and self-mixing operations. The circuit uses a slotline ring resonator for frequency stabilization and can be modified to include a varactor diode for wide-band frequency tuning. The circuit performance is compared with theoretical results derived from simple transmission-line models. The radiation patterns of the self-mixing oscillator antenna are also compared with those measured from a similarly configured passive antenna. Since the radiated power also serves as the local oscillator (LO) frequency for the self-mixing operation, the circuit is useful as a half-duplex transceiver. When the self-mixing operation is not required, a single oscillator antenna can be used as a transmitter and several units can be assembled in a planar array for spatial powercombining applications.

Oscillator-type active-integrated antenna: the leaky-mode approach

This paper describes basic research carried out to design a microwave source module employing the concept of an active-integrated leaky-mode antenna. The novel active-antenna source module utilizes a microstrip as the radiating element while adopting uniplanar technology for the active circuit design. The microstrip is operated in the first higher order odd mode, which is a leaky mode, and excited by a proximity-coupled center-fed slotline on the same surface of the uniplanar microwave-integrated circuit. The measured performance of an X-band transmission-type injection-locked active-integrated antenna source module demonstrated that such a design approach was suitable for linear array integration for quasi-optical power combining. The harmonic-balance (HB) analysis of the proposed active-integrated antenna agrees with the measurements in both free-running frequency and power level. The measured radiation patterns of the active-integrated antenna also agree well with the theoretical predictions.

Beam-steerable active array antenna

An integrated beam-steerable antenna configuration is presented in which an active resonant patch provides a simple and compact source of surface waves that radiate from a periodic surface along a dielectric waveguide. An X-band antenna has been developed and measurements carried out to determine its performance. A simple passive leaky-wave antenna model has also been developed. Comparisons between the measurements and the model indicate that the main lobe of the far-field pattern remains robust over the 0.6 GHz tuning bandwidth of the active source.

Waveguide-fed parallel plate slot array antenna

A novel planar antenna in which radiating slots are arrayed on one side of a square parallel plate waveguide and coupling slots occupy the other side is proposed. The antenna is excited via the coupling slots by a rectangular waveguide. In order to suppress unwanted reflections and to assure the purity of the transverse electromagnetic traveling-wave mode in the parallel plate waveguide, all the slots are arrayed in pairs. An X-band model antenna was fabricated, and uniform aperture illumination was demonstrated with 48% antenna efficiency. These results demonstrate the feasibility of antennas of this type.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A new method for obtaining antenna gain from backscatter measurements

A method is presented for determining the gain of an antenna from analysis of backscatter data of the antenna. This approach is different from those which have been presented in the past because it accounts for the presence of resonances which can occur in the antenna during a backscatter measurement. In particular, this type of resonance appears in the backscatter measurement of symmetric reflector antennas. This technique is applied to determine the gain of a Ka-band Cassegrain antenna and an X-band prime focus-fed antenna.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Experimental Simulation of a Warm-Plasma Medium

A warm-plasma medium is simulated using two rodded media. The E- and H-plane radiation patterns of an X-band horn antenna in the presence of such a medium are studied experimentally at 9.5 GHz and are compared with the theoretical patterns.

Short-backfire antenna with circular waveguide feed element

Abstract An X-band short-backfire antenna has been constructed and tested to optimize its radiation characteristics. The antenna comprises a backfire structure illuminated by an open-ended circular waveguide. The antenna has a high directivity, and symmetrical radiation pattern. The optimized parameters of the antenna have been measured and compared with that of a cup antenna of similar structure.

A Dual-Channel Rotary Joint for High Average Power Operation

A new type of dual-channel rotary joint combining the TM/sub 01/ mode and the circularly polarixed TE/sub 11/ modes in circular waveguide has been developed for an X-band antenna employed in a satellite communications link. Low losses are obtained in the high average power transmit channel (12.5 kW, CW) to avoid excessive temperature rise and in the receive channel to reduce the noise temperature of the system. High isolation between channels is achieved with the compact multimode exciters.

Antenna for rapid scan decorrelation radar

The mechanical design of an X-band antenna suitable for rotational speeds up to 1400 rev/min is described. The microwave design and performance are briefly outlined.