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This paper presents an analysis of antenna performance degradation due to the panel misalignment in a solid surface deployable antenna. The misalignment of the panel causes a phase error at the aperture plane due to path length differences. The radiated field is rapidly calculated using the aperture phase error method with analytic integrations in the case of uniform panel misalignment and quarter-zone uniform misalignment. The effects of the panel misalignment on the co-polarization characteristics of gain and side-lobe level (SLL) are calculated. Beam tilting is observed when the panel misalignment occurs uniformly in the half-zone of the whole panel area.

Large spaceborne antennas should be lightweight, a factor related to the development costs of launch vehicles. In order to overcome this drawback, a feasibility study of a new carbon fiber reinforced polymer (CFRP) named M55J/RS3 is carried out for a synthetic aperture radar (SAR) reflector antenna. In particular, the high resolution of detected images is taken into consideration. To validate the electrical performance, a test of the CFRP specimen is fabricated, and the transmission/reflection coefficients are measured using a standard Xband waveguide. Finally, the effective complex permittivity and effective electrical conductivity are derived from the obtained measured data. By applying the derived conductivity to the simulation of the radiation pattern, antenna gain, and beamwidth-instead of relying on the assumption of a perfect electric conductor-variations in electrical performance are also investigated and discussed.

This paper presents a theoretical approach for a modified turnstile antenna suitable for satellite communication in order to investigate the current distributions of radiators and radiation characteristics with equivalent model analysis. The proposed equivalent model is composed of an ideally horizontal dipole antenna and vertically loaded top-hat radiating elements. The required isoflux pattern with wide beamwidth has been achieved by attaching top-hat elements to the main radiators. In addition to illustrating radiation patterns, electrical performances like current distributions have been analyzed by mathematically manipulating the equations derived from the equivalent horizontal and vertical dipole model.

A structural modification of S-band turnstile antenna with cylindrical parasitic elements around a main radiator is introduced and investigated with respect to its gain, axial-ratio (AR) beamwidth, and radiation pattern. The overall structure is composed of a main radiator of two crossed bowtie-shaped dipole antennas and a feeding network using a Wilkinson power divider with phase differences between two parts. A final optimization of the parameter values for the enhancement of AR beamwidth is carried out from the parametric studies. The proposed antenna has not only a broad 5-dB AR bandwidth of 12.3% ranging from 2025 to 2290 MHz, but also a stable peak gain of 7.6 dBic with circular polarization (CP) characteristic.

A procedure for antenna parameter selections is proposed that considers the relationships between synthetic aperture radar performance and the antenna parameters of a parabola-type reflector antenna with a central flat dish. The effects of a central dish designed for weight reduction on the antenna beam pattern are also quantitatively analyzed using commercially available software based on the physical optics algorithm. The results of the theoretical analysis and simulation predict that a larger size of the central dish results in an increase in the sidelobe level, which is the reason for the increase in two important ambiguities, such as range ambiguity ratio (RAR) and azimuth ambiguity ratio (AAR). The dependence of RAR and AAR on Pulse repetition frequency is also analyzed and discussed.

A modified isoflux pattern antenna suitable for S-band satellite communication is introduced and investigated with respect to its beam pattern and axial ratios. For uniform coverage over the Earth's surface, an isoflux pattern antenna is required because of its uniform power density over a wide coverage area. A final optimization for the parameter values is carried out from the parametric studies of the antenna, and a simple analysis of the combination of horizontal dipoles and vertically attached top-hat elements is also carried out. The electrical performances of the proposed antenna are verified in terms of the reflection coefficients, radiation pattern, and axial ratios according to a wide beamwidth rather than at a fixed observation angle such as a 0° main beam direction.

This paper describes the turnstile junction-based OMT(Ortho-mode Transducer). It is usually well-known that turnstile junctions have symmetry structure of waveguide so the higher order modes, which occur inside the waveguide, can be easily cancelled. Because of this structure, the turnstile junction-based OMTs have high isolation and low return loss characteristics in broadband and are good for easy realization of dual polarization. The designed OMT has the application of radar seeker and operates in W-band(94GHz). The OMT design and electrical verification are performed through commercially available full-EM software.

Two circular-polarized circular patch antennas which have novel feeding structures such as a substrate integrated waveguide (SIW), a cavity-backed resonator and two different feeding transitions, are proposed and experimentally investigated in terms of electrical performances, including reflection coefficients, optimized parameter values, circular polarized antenna gain, axial ratios and radiation patterns. By inserting asymmetrical inductive via arrays into the interface region between the circular patch and SIW feeding structure, it is found that an enhancement of input impedance bandwidth has been achieved. In addition, in order to check the effects of feeding transition types on the electrical performances of the main radiator, two different feeding transitions, namely microstrip-to-SIW and coax-to-SIW, have been studied by considering reflection coefficients, gain, axial ratios and radiation patterns. As a result, it is experimentally proved that a broadband impedance bandwidth of 17.32% and 14.42% under the criteria of less than VSWR 2:1 and 1.5:1, respectively, have been obtained and an RHCP axial ratio of 2.34% with a maximum gain of 7.79 dBic has been accomplished by using the proposed antenna with coax-to-SIW transition operating at the X-band of 10 GHz center frequency.

This article deals with a design of compact six-band internal antenna using two identically stacked periodic-grooved patches and shorting plates and covering the frequency bands com- posed of cellular (824 - 894 MHz), GSM (880 -960 MHz), DCS (1710 -1880 MHz), PCS (1850 -1990 MHz), UMTS (1920 -2170 MHz), and ISM (2400 -2480 MHz) under the criteria 7.3 dB for the first five bands and 6 dB for the last band, respectively. To accom- plish this goal, the planar inverted-F antenna (PIFA) with periodic grooves is suggested, analyzed, and verified by using two commer- cially available softwares, CST MWS and HFSS based on the FDTD and FEM algorithms, respectively, and carrying out the measure- ments in terms of return loss, radiation patterns, and gains. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2718 -2722, 2008; Published online in Wiley InterScience (www.interscience.wiley. com). DOI 10.1002/mop.23776

A concurrent dual-band class-E power amplifier using composite right/left-handed transmission lines (CRLH TLs) is proposed. Dual-mode operation is achieved by using the frequency offset and nonlinear phase slope of CRLH TLs for the matching network of power amplifiers. The frequency ratio of two operating frequencies is not necessarily an integer. Two operating frequencies are chosen as 836 MHz and 1.95 GHz for simulation. Three methods for designing a CRLH TL power amplifier are proposed. The measured results based on one method show that output powers of 22.4 and 22.2 dBm were obtained at 800 MHz and 1.70 GHz, respectively. In terms of maximum power-added efficiency, we obtained 42.5% and 42.6% at 800 MHz and 1.70 GHz, respectively.

In this paper, we describe a fixed-beam broadband pla- nar antenna array at millimeter-wave frequencies. The antenna is fed by waveguide-feed and microstrip-feed networks. In order to ensure fixed beams and a broad bandwidth, a subarray concept is introduced. For efficient coupling, a novel waveguide-to-slot transition consisting of a slot pair and a narrow conductive bar is proposed. Simulated and mea- sured bandwidth is found to be more than 7.1% from 40.5- 43.5 GHz. The main beam directions are broadside over all frequencies. The maxi- mum measured antenna gain is 30.2 dBi at 42.0 GHz. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 283-287, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20279

Electromagnetic TM wave radiation from an obliquely flanged parallel-plate waveguide is studied. The Fourier-transform/series and Green's formula is used to represent the scattered wave and the simultaneous equations for the modal coefficients are formulated. Residue calculus is utilized to obtain a fast-convergent series solution. Numerical evaluation shows the behaviors of transmission, reflection, and radiation in terms of junction geometry and operating frequency.

In this paper, a design scheme for secant pattern radiator is presented. By combining a CP (Circular Polarization) generating adapter and a secant pattern radiator, a secant pattern antenna is designed. A secant pattern antenna is suitable for the data transmission in LEO satellite requiring wide angle coverage of the earth for the longer time visibility. In addition, secant pattern antenna is smaller and lighter compared to the ISOFLUX pattern antenna used in larger satellite. It is shown that the desired electrical performances including radiation pattern mask and return loss are satisfied through properly optimized parameters.

The problem of TE-wave scattering and radiation from a finite number of thick slits in a parallel-plate waveguide is solved. The Fourier transform is used to express the scattered field in the spectral domain. The boundary conditions are enforced to obtain a series solution which is amenable to numerical computation. The numerical computations are performed to illustrate the behaviors of scattering, transmission, and reflection in terms of incident angle, slit size and operating frequency. The solution presented is computationally very efficient so that it is useful for slotted-waveguide leaky-wave antenna applications.

A stubbed right-angle H-plane waveguide bend is proposed and its solution is obtained in analytic series form. The Fourier sine transform is used in the spectral domain to obtain the transmission and reflection coefficients in fast convergent series forms. The stubbed right-angle H-plane waveguide bend is shown to have better transmission characteristics (wider bandwidth) than the conventional bend without a stub. © 1995 John Wiley & Sons, Inc.

Electromagnetic scattering from multiple slits in a thick, perfectly conducting plane is investigated. The Fourier transform and mode matching are used to obtain the simultaneous equations. The simultaneous equations are solved to obtain a series solution which reduces to a closed form in the high-frequency limit. The transmission coefficients are represented in fast convergent series which are efficient for numerical computations. Numerical computations are performed to illustrate their scattering behaviors in terms of frequency, slit size, and slit number.

This paper presents an ISOFLUX pattern antenna with a novel matching transition suitable for X-band satellite data transmission. A novel waveguide transition with inset structure for reducing the reflection and length of waveguide are proposed and investigated. In addition to the development of a septum polarizer, waveguide transition and choke-ring radiator, it will be shown that the desired electrical performances like a radiation pattern mask and return loss are satisfied through properly optimized parameters of inset in waveguide transition.

An analytic solution for transverse electric mode scattering from a parallelplate waveguide with periodic grooves is obtained. The Fourier transform is used to express the scattered field in the spectral domain as superposition of the parallel-plate waveguide modes. The simultaneous equations are solved to represent the transmitted field in series form which is very efficient for numerical computation. When we use the residue calculus, the reflection and transmission coefficients are obtained, and their bandstop filter characteristics are studied in terms of frequency and groove sizes.

An analytic series solution for TE-mode scattering from two junctions in the H-plane waveguide is obtained. A Fourier-transform technique is applied to express the scattered field in the spectral domain in terms of parallel-plate waveguide modes. The boundary conditions are enforced to obtain simultaneous equations for the transmitted field. The simultaneous equations are solved to obtain the transmission and reflection coefficients in simple series forms. Comparisons between our solution and other existing results show excellent agreements. The behaviors of scattering from two junctions are studied in terms of frequency and junction geometry. The obtained analytic solutions are simple series so that they are very efficient for numerical computation. >

In this paper, modified triangular-shaped waveguide-typed septum polarizer has been suggested and verified by using commercially available software and carrying out the comparison with the conventional rectangular waveguide-typed polarizer. It is expected that the proposed structure shows the better electrical performances than the conventional one in terms of the smooth energy-transfer of TE 10 and TE 01 -modes. The simulated result shows that the proposed structure accomplished axial ratio of less than 0.32dB, return losses of lower than −32dB, and isolation characteristics between −24dB and −35dB at the target frequency ranging from 8 to 8.4GHz.

Radially-guided low-profile equal and unequal power division functions are accomplished by using Substrate Integrated Waveguide (SIW) technology with center feeding structures and additional power/phase-control vias. The controlled positions of guiding posts provides the unequal division ratios and phase variations at each port. At this time, the width of the SIW has been kept the same in spite of the shifted position of guiding posts. The electrical performances including return loss, transmission characteristics and phase variations are discussed through simulation and measured data.

We report a millimeter wave super lens based on the left-handed metamaterial using split-ring resonator (SRR) and complementary SRR (CSRR). The millimeter wave cannot propagate far away due to short wavelength. Therefore, the system for THz or millimeter wave band demands the lens to obtain strong focused signal from weak waves caused by scattering in atmospheric environment. The proposed left-handed metamaterial (LHM) lens based on SRR and CSRR can be designed by scanning the focal point of flat LHM lens in the region under detection and screening directly the field intensity distribution of backscattered millimeter wave refocused by the flat LHM lens. The simulation results confirm that this lens exhibits a focus with strong E-field distribution.

A dual-band radial stub antenna with tapered radial slot on backside was proposed. Conducting radial stub and tapered radial slot used for realizing dual band operation are realized, and make impedance matching possible over dual band. Operating frequencies are chosen at 2.4 GHz and 5.2 GHz on simulation, and measurement results are in good agreement with the simulation result. Measurement result of return loss for the proposed antenna is -20.7 dB and -39.8 dB at 2.4 GHz and 5.2 GHz. In addition, measured gain for the proposed antenna is 4.210 dBi and 4.246 dBi at 2.4 GHz and 5.2 GHz, and radiation pattern of the proposed antenna has the same characteristic that the general dipole antenna shows.

A novel push-push oscillator using H-slot DGS resonator and CRLH-TL is presented. This triple-fold frequency push-push oscillator is composed of two active sub-circuits built on top side of double transmission lines and an H-slot built on the bottom side. Nonlinear phase slope of CRLH-TL provides that the fundamental oscillation is suppressed by -60dBc. The proposed push-push oscillator shows the output power of 11.5 dBm at 6.13 GHz and the phase noise of-128dBc/Hz at 1MHz offset.

The application of the multiple folded structure to a compact tri-band PlFA (planar inverted-F antenna) composed of three resonant frequencies, GSM (880-960 MHz) / DCS1800 (1710-1880 MHz) / Satellite DMB (2605-2655 MHz), are treated with the optimized parameter values. The proposed antenna has been designed and analyzed by using commercially available software, CST MWS based on the FDTD algorithm and a simple resonant equation, respectively. In addition, the return loss has been measured and compared between measured and simulated data under the criterion of VSWR less than 3.

TM-wave scattering from slits in thick parallel conducting screens is analyzed using the Fourier transform. The simultaneous equations for the modal coefficients are formed in terms of convergent series. Numerical computations are performed to illustrate the behavior of transmission and scattering from the slits. High-frequency solutions for scattering and transmission are obtained in approximate closed forms.

Ring resonators have been widely used for various applications. In this paper, double half ring resonators working at 2.5GHz are proposed for bandpass filter applications. These resonators suppress multiple harmonics (2/sup nd/ and 3/sup rd/ harmonics) and provide size compactness with employing various physical configurations. Conventional circular ring resonators are modified to be transformed to new forms holding double half ring configurations. A closed loop split ring resonator and open loop double half ring resonators are compared to decrease the resonant frequency. Continuously, the open double half ring resonator adds open microstrip lines to additionally reduce the resonant frequency. Open loop structure provides flexible design and lower resonant frequency, in other words, reduction of real estate. 4 different simulated resonators are fabricated and measured. They show very high quality factor and suppression of multiple harmonics.

We analyze the radiation and coupling problem from a single microstrip transmission line and two signal traces. In this paper, it is shown that the reduction of the radiated emission from the signal traces can be accomplished by using the novel patterns on the ground planes. The radiation mechanism from the transmission line on a novel ground plane is predicted and measured by using the commercially available software and experiment, respectively.

In this paper, mode transitions inside the waveguides with step discontinuities are studied. These transitions are applied to design the corrugated horn antenna directly connected with band pass filter (BPF) in millimeter wave regime. The used rectangular waveguide at the input port is a WR-22 standard waveguide for the frequencies from 40.5 GHz to 43.5 GHz. The RF system used for transmitter and receiver requires wide beam width and wide bandwidth characteristics for coverage and return loss, respectively. Also the antenna needs the high front-to-ratio in radiation pattern.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this paper, a plate antenna with elliptical cross section and ellipticity ratio is studied. The return loss of the proposed antenna and conventional antennas is investigated using the simulation package CST MW Studio ver. 3.2 and fabricated antennas. The effects of ellipticity ratio on the radiation pattern and reflection coefficients are described. The given structure can handle the average power of several hundreds of watts. The simulated results of this antenna are obtained for various values of the ellipticity ratio of elliptical cross section loaded at the input port

In this paper, a broadband sleeve-conical antenna with arbitrary sleeve shape is studied. The frequency range of the antenna is aimed at 300 MHz to 3 GHz. The reflection coefficients, obtained by using conventional equations, are compared with simulated data obtained by using the CST MW Studio. The validity of the software has been confirmed by analysing many canonical structures. The given structure subsumes the scattering problem that is considered in the existing literature dealing with special cases. The simulated results of this antenna system are obtained for various values of the length and the radius of the sleeve, through which the effect of these parameters on the radiation field behavior is studied.

This article describes the radiation characteristics from multiple rectangular grooves in a dielectric-covered ground plane. The theoretical far-zone radiation pattern is compared with the measured data at 10 and 11 GHz using a wavenumber conversion procedure.

Flanged parallel-plate radiation of a TM-wave into a dielectric slab is investigated. The Fourier transform is used to represent the radiation field in the spectral domain and the boundary conditions are enforced to obtain the reflection coefficient in rapidly converging series form. Numerical computations are performed to illustrate the radiation behaviour in terms of aperture size, frequency, and slab geometry. It is found that a single-mode approximate solution predicts well the radiation behaviour when a flanged rectangular waveguide is excited in the TE/sub 10/ mode.