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Microwave Symposium Digest, 2004 IEEE MTT-S International

Date 6-11 June 2004

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Displaying Results 1 - 25 of 237
  • Extended theory of FDTD S- and P-eigenmodes in lossy media and its application to the analysis of coupled problems

    Page(s): 1713 - 1716 Vol.3
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    FDTD solutions in lossy media are shown to comprise two orthogonal families of S- and P-eigenmodes. The S-modes are counterparts of physical waves, retaining their fundamental properties such as current continuity. Contrary to the lossless case, they are subject to bilateral dispersion, although the numerical anisotropy of the FDTD mesh is actually reduced. The P-modes do not propagate and decay exponentially in time. This makes Maxwell FDTD suitable for coupling with other physical solvers, which may change the electromagnetic media properties and boundaries in time. Any thus generated numerical changes are included in and dissipated by the P-modes. View full abstract»

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  • Initial observation and analysis of dielectric-charging effects on RF MEMS capacitive switches

    Page(s): 1943 - 1946 Vol.3
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    Capacitance voltage and RF-output characteristics of electrostatically actuated MEMS switches were measured under different control and stress voltages. It was found that positive voltage stress caused negative charging of the dielectric whereas negative voltage stress caused positive charging of the dielectric. This is consistent with the amphoteric nature of traps in the silicon oxynitride dielectric used for the switches. A hypothesis of charge injection in minutes and charge migration in milliseconds was proposed to explain real-time and nonsymmetrical drift of pull-down and hold-down voltages of the switches. View full abstract»

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  • Adaptively preserving power amplifier linearity under antenna mismatch

    Page(s): 1515 - 1518 Vol.3
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    An adaptive method is proposed to preserve power amplifier linearity under severe antenna mismatch condition, as an alternative to an isolator. At high output power and mismatch conditions voltage clipping, due to collector voltage saturation of the bipolar power transistor, is demonstrated to be the main cause of distortion. Linearity degradation can be properly monitored by minimum voltage detection, which is used adaptively to control the gain of a pre-amplifier in order to prevent collector voltage clipping. Measurement results demonstrate a significant linearity improvement under severe mismatch conditions. For an EDGE power amplifier an EVM improvement of 5% and an ACPR improvement of 10dB have been obtained at 28.5 dBm output power and a VSWR of 4:1. View full abstract»

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  • Non-contact probing of integrated circuits and packages

    Page(s): 1805 - 1808 Vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (713 KB) |  | HTML iconHTML  

    We report a non-contact probing technique capable of internal vector-voltage measurement of mm-wave ICs and package interconnects. Using a micro-fabricated probe, localized voltage amplitude and phase measurements can be made with a micrometer spatial resolution and without depassivation of the DUT test points. A probe with a bandwidth >30GHz, <10mV amplitude and <2° phase resolution, and with <10fF loading is demonstrated. View full abstract»

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  • Channel temperature model for microwave AlGaN/GaN power HEMTs on SiC and sapphire

    Page(s): 2031 - 2034 Vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (454 KB) |  | HTML iconHTML  

    A key parameter in the design trade-offs made during AlGaN/GaN HEMTs development for microwave amplifiers is the channel temperature. An accurate determination can generally only be found using detailed software; however, a quick estimate is always helpful, as it speeds up the design cycle. This paper gives a simple technique to estimate the channel temperature of a generic AlGaN/GaN HEMT on SiC or sapphire, while incorporating the temperature dependence of the thermal conductivity. The procedure is validated by comparing its predictions with the experimentally measured temperatures in microwave devices presented in three recently published articles. The model predicts the temperature to within 5 to 10 percent of the true average channel temperature. View full abstract»

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  • A gradient-based optimization technique employing determinants for the synthesis of microwave coupled filters

    Page(s): 1369 - 1372 Vol.3
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    A procedure is presented whereby cross-coupled filters can be synthesized using a gradient-based optimization technique employing determinants. The cost of function formulated depends on a minimum set of characteristics that can completely describe the desired response. An analytical gradient is also derived for the error function enhancing the efficiency of the optimization process. The proposed algorithm is less vulnerable to local minima and proves more robust compared to other optimization techniques. Examples demonstrating the efficiency of the proposed algorithm are provided. View full abstract»

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  • New type of MMIC reduced-size shunt/series stubs in coplanar waveguide

    Page(s): 1883 - 1886 Vol.3
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    This paper proposes a practical approach for developing a new class of compact coplanar waveguide (CPW) series/shunt tabs. This approach offers a reduction in length of about 50% by collocating multiple stubs together. The experimental results presented in this paper demonstrate the validity of the design method. View full abstract»

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  • Analysis and design of coupled line impedance transformers

    Page(s): 1951 - 1954 Vol.3
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    Impedance transformers employing coupled line sections that are less than quarter wavelengths are presented in this paper. Exact solutions relating the coupled line parameters and arbitrary impedance transformation ratios are derived. This is unlike previous coupled line transformers, which were designed based on electromagnetic simulations and provide only impedance transformation ratios of 1:4. Various design curves demonstrating a wide range of practical coupled line parameter values are presented and validated with experimental results. A 50 Ω to 170 Ω impedance transformer using λ/8 coupled line section achieved over 10 dB return loss from 0.5 to 0.9 GHz. View full abstract»

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  • A design of single and multi-section microstrip directional coupler with the high directivity

    Page(s): 1895 - 1898 Vol.3
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    In this paper, single and two-section microstrip directional couplers are implemented for realizing the high-directivity characteristics. The achievement of the high-directivity with microstrip configuration is carried out by the distributed capacitor to decrease the even and odd mode phase difference. Capacitive compensation is performed by gap coupling of open stub formed in sub-coupled line. Therefore, insertion loss and power handling capability are not affected by the gap coupling. The proposed structure is easy to fabricate and incorporate another microwave device due to planner microstrip. We designed and fabricated single and two-section directional coupler with 20 dB coupling. In spite of microstrip structure, the capacitive compensation structure shows the 30 dB (1.6 GHz-2 GHz range) and 26 dB (1 GHz-2.5 GHz) of directivity in single and two-section directional couplers, respectively. Experimental results show a good performance with excellent directivity characteristics. View full abstract»

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  • A high efficiency Chireix out-phasing power amplifier for 5GHz WLAN applications

    Page(s): 1535 - 1538 Vol.3
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    This paper describes the design methodology and presents measured results for a 5GHz Chireix out-phasing power amplifier. The outputs of two high efficiency amplifiers operating in class F are combined using a lossless combiner. A novel implementation of the class F output tuning networks and combiner using bond wires is also described. To our knowledge, this is the most efficient 802.11a amplifier ever reported. View full abstract»

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  • Analysis and experimental validation of a triaxial antenna for microwave tumor ablation

    Page(s): 1437 - 1440 Vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB) |  | HTML iconHTML  

    We apply a new triaxial antenna for microwave ablation procedures. The antenna consists of a coaxial monopole inserted through an 18-gauge biopsy needle positioned one quarter-wavelength from the antenna base. The biopsy needle creates a triaxial structure, which enhances return loss by more than 10 dB, thus limiting return currents along the feed line. Numerical simulations are used to optimize the antenna design. Numerical ex vivo experimental results are presented to quantify the field distribution, heating pattern and return loss of the antenna. View full abstract»

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  • Ultra-sensitive microwave detection of protein conformational changes

    Page(s): 1583 - 1586 Vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (435 KB) |  | HTML iconHTML  

    A coaxial driven planar slot antenna resonant in the microwave regime was used to detect changes in protein conformation induced by temperature modulation. Simultaneous dielectric and UV/VIS spectroscopy measurements were obtained by attaching the slot antenna to a fused-quartz UV/VIS sample holder. Similar thermodynamic parameters (midpoint temperature and enthalpy) were obtained from both techniques over a wide concentration range and under a variety of pH condition. Here we demonstrate that a near-field antenna can be used to detect changes in conformation at very low protein concentrations, and that the protein is not destabilized by the presence of microwave power. View full abstract»

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  • Microwave radiation force on a parallel-plate resonator

    Page(s): 2043 - 2046 Vol.3
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    A simulation method is proposed and tested in order to determine the radiation force on metal targets, whose size is comparable to wavelength. The method is based on the MoM solution of the electric field integral equation, accurate calculation of the near fields, and removal of the self-interaction terms responsible for the pinch effect. The method is used to determine the local force distribution for a parallel-plate metal resonator and a circular disk resonator at plane wave incidence. It is observed that, at the resonance, the individual metal plates may experience very large local force densities, despite the fact that the net radiation force still remains very small. View full abstract»

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  • Vector mixer characterization for image mixers

    Page(s): 1743 - 1746 Vol.3
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    The vector mixer characterization method first introduced by Dunsmore can be used only for mixers where the local oscillator (LO) frequency lies between the RF input and output frequencies. Attempts to use the method for image mixers, where the LO is greater than both the input and output frequencies, yield erroneous results. An improved method is described which can properly characterize both type of mixers. A theoretical basis is introduced and experimental results presented which justify the new method. View full abstract»

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  • A compact microstrip λ/4-SIR interdigital bandpass filter with extended stopband

    Page(s): 1621 - 1624 Vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (502 KB) |  | HTML iconHTML  

    This paper presents a new microstrip interdigital bandpass filter using λ/4 stepped impedance resonator (SIR) to achieve both size reduction and stopband extension. It is shown that as the low-impedance to high-impedance ratio is maintained smaller than unity, fundamental f0 and the first spurious fs shift to the lower and higher frequency value respectively, thus extending the rejection band, as in the case of λ/2-SIR. Unequal lengths spurlines are embedded into the resonators where additional transmission zeros can be realized in the spurious passband such that the upper rejection band can be further extended. A 3rd order Butterworth bandpass filter centered at 700MHz with spurious response up to 4f0 is simulated and measured to demonstrate the proposed design usefulness. View full abstract»

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  • Perturbation theory approach to the ferrite coupled stripline

    Page(s): 1903 - 1906 Vol.3
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    Perturbation theory is applied to analyze the ferrite coupled stripline (FCL) with longitudinal magnetization. Up to first order, the fields and propagation constants of the modes are obtained, neglecting the coupling to higher TE and TM modes. Based on this result, the scattering matrix of a FCL structure with a given finite length is calculated. Simple relations which connect the nonreciprocal behavior with the geometrical design parameters and the ferrite material properties are found. The perturbation results are in good agreement with simulation data and thus provide a basis for further design of nonreciprocal devices based on the FCL structure. View full abstract»

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  • A 2.4GHz/5.2GHz CMOS power amplifier for dual-band applications

    Page(s): 1539 - 1542 Vol.3
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    A 2.4GHz/5.2GHz CMOS dual band power amplifier is presented in this work. In order to design high power CMOS amplifier, various power NMOS transistor cells are scrutinized. Considering small signal and large signal characteristics of power NMOS cell, 2×128×5μm cell is chosen for our dual band PA. A modified macro model is used for the simulation accuracy. As for selecting desired band, there are band-switched matching networks on both input and load of the first stage amplifier, which is followed by NMOS SPDT switch. At 2.4Ghz and 5.2GHz bands, the achieved values of Psat are 9.7dBm and 19.5dBm, respectively. In case of PAE, we obtain 15.3% at 5.2GHz. View full abstract»

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  • High power and high efficiency 30 W compact S-band HBT power chips with gold or diamond heat spreaders

    Page(s): 1527 - 1530 Vol.3
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    HBT power technology offers an excellent compromise for high power and high efficiency amplifiers up to the Ku band. In this paper, we present the performances of GaInP/GaAs power chips. Two different approaches to thermal management were proposed for very high power levels. Pulsed power measurements of power chips integrating thick gold or diamond as heat spreaders are reported. An output power of 31 W with 49.5% of PAE was obtained at 2.9 GHz on 3.3mm2 of GaAs area. This corresponds to a power density of 9.4W/mm2. These power chips constitute very attractive chips for compact high power, high efficiency amplifiers for radar and communication systems. View full abstract»

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  • A new electronically tunable combline filter with simultaneous continuous control of central frequency and bandwidth

    Page(s): 1291 - 1294 Vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (519 KB) |  | HTML iconHTML  

    A new reconfigurable band pass filter with electronically continuous control of both central frequency and bandwidth is presented in this paper. The bandwidth tuning is achieved by means of an ingenious method to modify the electrical couplings of the filter resonators. The propose structure employs varactor capacitors as variable reactance elements. Finally, a filter prototype is designed, constructed and measured in suspended stripline technology in the UHF band (470-862 MHz). View full abstract»

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  • Novel inductance-incorporated microstrip coupled-line bandpass filters with two attenuation poles

    Page(s): 1979 - 1982 Vol.3
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    A microstrip coupled-line bandpass filter with good stopband rejection is proposed. By introducing an additional shunt inductance to the conventional coupled-line filter, along with the capacitively coupled gap between coupled-line sections, two attenuation poles at upper and lower stopbands may be achieved without increasing the circuit area. The proposed filter exhibits good stopband rejection with no repeated passband at twice the center frequency as compared to the conventional coupled-line filters. Specifically, a microstrip coupled-line bandpass filter centered at 2.4 GHz with 5.4% 3-dB bandwidth and two attenuation poles is implemented. View full abstract»

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  • Ultra wideband 8 to 40 GHz beam scanning phased array using antipodal exponentially-tapered slot antennas

    Page(s): 1757 - 1760 Vol.3
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    An antipodal exponentially-tapered slot antenna (AETSA), also called as an antipodal vivaldi antenna, is designed to achieve several octave bandwidth from 8 to 40 GHz, and a 1×4 AETSA array is designed for H-plane scanning from 8 to 40 GHz. A multi-line phase shifter controlled by a piezoelectric transducer (PET) is used for H-plane scanning. The antenna gain of single antenna varies from 5 to 10 dB over the operating frequencies. The 1×4 phased array shows a wide beam scanning capability of over 30° in the H-plane. View full abstract»

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  • Super compact split ring resonators CPW band pass filters

    Page(s): 1483 - 1486 Vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (402 KB) |  | HTML iconHTML  

    Coplanar waveguide (CPW) band pass filters consisting on signal-to-ground wire connections alternating with series gaps, and split ring resonators (SRRs) etched in the back substrate slide, underneath the slots, are presented for the first time. It is demonstrated that by properly tuning SRR dimensions, a narrow pass band below the cutoff frequency of the wired/gaped CPW structure can be obtained. The relevant characteristics of the designed structure are: insertion losses below 4 dBs in the allowed band, out of band rejection above 30 dBs, and very high transition slopes with only three SRR stages. Due to subwavelength operation of SRRs, the proposed structures are very compact with potential application to the fabrication of planar filters for future communication transceivers. View full abstract»

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  • Enhancement of power amplifier efficiency through dynamic bias switching

    Page(s): 2047 - 2050 Vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (426 KB) |  | HTML iconHTML  

    Linear digital modulation techniques in modern communication systems generate carrier signals with relatively high peak-to-average ratio. For linear amplification of such a signal, power amplifier must be operated at excessive back off, thus sacrificing the overall amplifier efficiency. Dynamic bias switching (DBS) can be used to enhance the efficiency of PA and the means to combat the degradation of spectrum regrowth and in-band noise are discussed in this paper. DBS is achieved by partitioning the required supply rail into two or several levels. The supply voltage is switched between the steps, and is adjusted in tune with the signal envelope. This is accomplished by using a pass-transistor (gate) operated as a switch with very low channel resistance. This approach avoids the energy loss associated with continuous tracking (amplification) of the signal envelope reported in the literature. View full abstract»

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  • Integration of parallel-plate ferroelectric varactors with BCB-on-silicon microstrip circuits

    Page(s): 1907 - 1910 Vol.3
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    A four mask process is developed to integrate parallel-plate ferroelectric varactors with BCB film microstrip circuits. A tri-layer stack, consisting of bottom electrode (M1), ferroelectric film and top electrode (M2), deposited on silicon substrate is used as a ground plane for microstrip circuits. A BCB film, spin coated on the tri-layer ground plane for microstrip circuits patterned in the third metal layer (M3). Simple circuits are fabricated to demonstrate the potential of the proposed integration. View full abstract»

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  • A study of feeding options aimed at cancelling crosstalk in multiconductor transmission lines

    Page(s): 1631 - 1634 Vol.3
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    This paper presents practical verification of a concept of total elimination of crosstalk between signals propagating in multiconductor transmission lines. The assumption is that the crosstalk should be eliminated by proper feeding and matching at the line ends, in the presence of physical coupling between conductors all along the lines. A family of proper feeding and matching configurations is investigated. Results of measurements are presented for two of them. Another one is verified by modelling. View full abstract»

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