Design and performance of an ultrawide-band ceramic-loaded slot spiral

The miniaturization of a broadband square slot spiral antenna is proposed using high-contrast (/spl epsiv//sub r/>30) dielectric materials. A previously developed circular slot spiral antenna is the starting point of the design. This spiral is first modified in terms of its feed and termination to facilitate the dielectric loading of the antenna by means of a superstrate. The subsequently placed superstrate is also modified by tapering its thickness to improve impedance matching. Several measurements were carried out using square spiral apertures having diameters of 2' and 6', respectively. It is demonstrated that the ceramic loading of a 2' spiral with an /spl epsiv//sub r/=90 shifts the initial operating frequency by nearly 320 MHz down to 564 MHz representing a size reduction of 36%. Additionally, a 6' aperture loaded with a superstrate having /spl epsiv//sub r/=30 is shown to operate down to 270 MHz corresponding to a size reduction of 18%.     

Achievable key rates for universal simulation of random data with respect to a set of statistical tests

We consider the problem of universal simulation of an unknown source from a certain parametric family of discrete memoryless sources, given a training vector X from that source and given a limited budget of purely random key bits. The goal is to generate a sequence of random vectors {Y/sub i/}, all of the same dimension and the same probability law as the given training vector X, such that a certain, prescribed set of M statistical tests will be satisfied. In particular, for each statistical test, it is required that for a certain event, /spl epsiv//sub /spl lscr//, 1 /spl les/ /spl lscr/ /spl les/ M, the relative frequency /sup 1///sub N/ /spl Sigma//sub i=1//sup N/ 1/sub /spl epsiv//spl lscr//(Y/sub i/) (1/sub /spl epsiv//(/spl middot/) being the indicator function of an event /spl epsiv/), would converge, as N /spl rarr/ /spl infin/, to a random variable (depending on X), that is typically as close as possible to the expectation of 1/sub /spl epsiv//spl lscr/,/ (X) with respect to the true unknown source, namely, to the probability of the event /spl epsiv//sub /spl lscr//. We characterize the minimum key rate needed for this purpose and demonstrate how this minimum can be approached in principle.     

Wideband simple cylindrical dielectric resonator antennas

Bandwidths of the coaxial fed and aperture coupled cylindrical dielectric resonator antennas (DRAs) with broadside radiation patterns are enhanced by exciting the HEM/sub 11/spl Delta// (1相似文献   

Wideband coplanar waveguide-to-rectangular waveguide transition using fin-line taper

This letter introduces a new wideband coplanar waveguide-to-rectangular waveguide transition. The transition uses a uniplanar circuit in line with the waveguide, which eases the design and fabrication. The design does not require airbridges. Simulations and measurements of X-band (8.2-12.4 GHz) transitions based on both a low- and high-permittivity material (/spl epsiv//sub r/= 2.33 and 10.8) show that the transition works fine over the full frequency band. For /spl epsiv//sub r/= 2.33 the measured return and insertion loss of a back-to-back transition are more than 16 dB and less than 0.4dB, respectively. The corresponding values for /spl epsiv//sub r/= 10.8 are more than 10 dB and less than 1.0 dB, respectively, over 90% of the frequency band. The measured insertion loss values indicate losses of less than 0.14 dB and 0.36 dB at the center frequency for a single transition on a substrate with /spl epsiv//sub r/= 2.33 and 10.8, respectively.     

Loss characteristics of high-/spl epsiv//sub r/ microstrip lines fabricated by an etchable thick-film on ceramic MCM technology

Etchable thick-film multi-chip-module (MCM) technology has led to the possibility of fabricating microwave integrated circuits (MICs) with performance similar to MICs produced using more expensive conventional thin-film MCM-D techniques. However, little data is available on the loss characteristics of the technology at microwave frequencies. This paper describes an experimental investigation into the loss properties of high-definition etchable thick-film MCM microstrip lines formed on a variety of high dielectric constant (high-/spl epsiv//sub r/) ceramic substrates. Substrates investigated comprise 96% alumina (/spl epsiv//sub r/=9.5), (Zr,Sn)TiO/sub 4/(/spl epsiv//sub r/=36.6) and BaO-PbO-Nd/sub 2/O/sub 3/-TiO/sub 2/ (/spl epsiv//sub r/=90.9). Microstrip loss properties are determined by fabricating a series of loosely coupled half-wave resonators on each substrate, with a range of characteristic impedance values. Measurements to 6 GHz are compared to those for similar lines fabricated using conventional thin-film MCM-D technology. The results demonstrate that etchable thick-film MCM technology provides many of the advantages of thin-film MCM-D technology, such as low-loss and high-definition conductors, and is suitable for the cost-effective fabrication of miniaturised high-performance microstrip MICs in high volume.     

RF HBT oscillators with low-phase noise and high-power performance utilizing a (/spl lambda//4/spl plusmn//spl delta/) open-stubs resonator

This paper presents a new type of transmission-line resonator and its application to RF (microwave and millimeter-wave) heterojunction bipolar transistor (HBT) oscillators. The resonator is a parallel combination of two open stubs having length of /spl lambda//4/spl plusmn//spl delta/(/spl delta//spl Lt//spl lambda/), where /spl lambda/ is a wavelength at a resonant frequency. The most important feature of this resonator is that the coupling coefficient (/spl beta//sub C/) can be controlled by changing /spl delta/ while maintaining unloaded Q-factor (Q/sub u/) constant. Choosing a small value of /spl delta/ allows us to reduce /spl beta//sub C/ or equivalently to increase loaded Q-factor (Q/sub L/). Since coupling elements such as capacitors or electromagnetic gaps are not needed, /spl beta//sub C/ and Q/sub L/ can be precisely controlled based on mature lithography technology. This feature of the resonator proves useful in reducing phase noise and also in enhancing output power of microwave oscillators. The proposed resonator is applied to 18-GHz and 38-GHz HBT oscillators, leading to the phase noise of -96-dBc/Hz at 100-kHz offset with 10.3-dBm output power (18-GHz oscillator) and -104-dBc/Hz at 1-MHz offset with 11.9 dBm (38-GHz oscillator). These performances are comparable to or better than state-of-the-art values for GaAs- or InP-based planar-circuit fundamental-frequency oscillators at the same frequency bands.     

Asymptotic properties on codeword lengths of an optimal FV code for general sources

This correspondence is concerned with asymptotic properties on the codeword length of a fixed-to-variable length code (FV code) for a general source {X/sup n/}/sub n=1//sup /spl infin// with a finite or countably infinite alphabet. Suppose that for each n /spl ges/ 1 X/sup n/ is encoded to a binary codeword /spl phi//sub n/(X/sup n/) of length l(/spl phi//sub n/(X/sup n/)). Letting /spl epsiv//sub n/ denote the decoding error probability, we consider the following two criteria on FV codes: i) /spl epsiv//sub n/ = 0 for all n /spl ges/ 1 and ii) lim sup/sub n/spl rarr//spl infin///spl epsiv//sub n/ /spl les/ /spl epsiv/ for an arbitrarily given /spl epsiv/ /spl isin/ [0,1). Under criterion i), we show that, if X/sup n/ is encoded by an arbitrary prefix-free FV code asymptotically achieving the entropy, 1/nl(/spl phi//sub n/(X/sup n/)) - 1/nlog/sub 2/ 1/PX/sup n/(X/sup n/) /spl rarr/ 0 in probability as n /spl rarr/ /spl infin/ under a certain condition, where P/sub X//sup n/ denotes the probability distribution of X/sup n/. Under criterion ii), we first determine the minimum rate achieved by FV codes. Next, we show that 1/nl(/spl phi//sub n/(X/sup n/)) of an arbitrary FV code achieving the minimum rate in a certain sense has a property similar to the lossless case.     

Dielectric resonator with discrete electromechanical frequency tuning

A novel approach for discrete frequency tuning of dielectric resonators based on electromechanical actuators such as the microelectromechanical system is presented. The concept is based on the intermodal coupling between the TE/sub 01/spl delta// mode of a cylindrical dielectric resonator and the radially arranged planar slotline resonators. The resonance frequency of the dielectric resonator is changed by switching a resistive load at the open end of each quarter-wave slotline resonator leading to a variation of the coupling between the slotline resonator mode and the TE/sub 01/spl delta// mode of the dielectric resonator. As a consequence, the resonance frequency of the TE/sub 01/spl delta// mode changes. Based on this novel tuning concept, discrete tuning by 5 MHz in 0.25-MHz frequency steps was demonstrated for a test resonator at 2 GHz. The unloaded quality factor is about 12000 and the measured switching time is about 1 ms.     

Measurements of V-band n-type InSb junction circulators

A V-band n-type indium antimonide (InSb) junction circulator supported in a three-port finline structure has been fabricated and measured. Broad-band operation for a semiconductor junction circulator over the frequency range 50-75 GHz at a temperature of 77 K has been demonstrated for the first time. With an applied magnetic flux density of 0.88 T, approximately 10 dB of differential isolation has been measured over the entire waveguide frequency band. The measured results also indicate that circulation is possible when the semiconductor material has /spl epsiv//sub eff/<0. In principle, broader bandwidths are predicted since frequency tracking can be achieved from /spl epsiv//sub eff/<0 to /spl epsiv//sub eff/>0, but the bandwidths of the circulators measured are restricted by the cutoff frequency of the V-band waveguide. Experimental evidence also showed that a disc or triangular-shaped semiconductor suspended in an E-plane junction without the finline circuit provides circulation. The experimental results clearly illustrate the broad-band behavior of semiconductor junction circulators for operation beyond 40 GHz, which is difficult to achieve with ferrite-based circulators.     

On the scaling limit of ultrathin SOI MOSFETs

In this paper, a detailed study on the scaling limit of ultrathin silicon-on-insulator (SOI) MOSFETs is presented. Due to the penetration of lateral source/drain fields into standard thick buried oxide, the scale-length theory does not apply to thin SOI MOSFETs. An extensive two-dimensional device simulation shows that for a thin gate insulator, the minimum channel length can be expressed as L/sub min//spl ap/4.5(t/sub Si/+(/spl epsiv//sub Si///spl epsiv//sub I/)t/sub I/), where t/sub Si/ is the silicon thickness, and /spl epsiv//sub I/ and t/sub I/ are the permittivity and thickness of the gate insulator. With t/sub Si/ limited to /spl ges/ 2 nm from quantum mechanical and threshold considerations, a scaling limit of L/sub min/=20 nm is projected for oxides, and L/sub min/=10 nm for high-/spl kappa/ dielectrics. The effect of body doping has also been investigated. It has no significant effect on the scaling limit.     

Computer-Aided Design of Three-Port Waveguide Junction Circulators

The complete performance of a lossless three-port H-plane waveguide junction loaded coaxially with various inhomogeneous ferrite cylanders has been evaluated over the waveguide bandwidth and compared with experiment. Qualitative agreement between the predicted and measured performance was generally good using only the first three modes, n=0/spl plusmn/1. It has been shown theoretically and verified experimentally that if the 4/spl pi/M/sub s/ of a homogeneous rod or the internal field is increased, the circulation frequency f/sub 0/ increases; conversely, if the pemittivity is increased, f/sub 0/ decreases. These conflicting effects are modified when the magnetization 4/spl pi/M/sub s/ and permittivity /spl epsiv/ are inhomogeneous. For example, if the 4/spl pi/M/sub s/(/spl gamma/) is small at the outer surface of the rod (with permittivity held constant), the effect on f/sub 0/ is very small; but if 4/spl pi/M/sub s/(spl gamma) approaches zero for /spl gamma/ small, then f/sub 0/ may decrease significantly. On the other hand, if /spl epsiv//sub/spl gamma//(/spl gamma/) approaches unity near the outer surface of the rod, f/sub 0/ may increase significantly; but if /spl epsiv//sub/spl gamma//(/spl gamma/) approaches unity near the center of the rod, f/sub 0/ is affected relatively little. The inhomogeneous structure has also shown that decreasing the ferrite volume may improve the performance, and high-power applications are suggested. With a conducting pin down the center of the ferrite, relative bandwidths of 40-50 percent are predicted.     

Correction Due to a Finite Permittivity for a Ring Resonator in Free Space

To better determine the resonant fields of a dielectric resonator with high permittivity epsilon/sub r/, the asymptotic theory with1//spl radic/epsilon/sub 3/ as a small parameter is extended by adding higher order terms in 1//spl radic/epsilon /sub r/ in the fields, the resonant wavenumber, and radiation Q. Extensive data are shown for the Phi independent "nonconfined" mode of a ring resonator, which radiates as a magnetic dipole. Some results are added for the "magnetic quadruple" mode.     

InGaAs-InP DHBTs for increased digital IC bandwidth having a 391-GHz f/sub /spl tau// and 505-GHz f/sub max/

InP-In/sub 0.53/Ga/sub 0.47/As-InP double heterojunction bipolar transistors (DHBT) have been designed for use in high bandwidth digital and analog circuits, and fabricated using a conventional mesa structure. These devices exhibit a maximum 391-GHz f/sub /spl tau// and 505-GHz f/sub max/, which is the highest f/sub /spl tau// reported for an InP DHBT-as well as the highest simultaneous f/sub /spl tau// and f/sub max/ for any mesa HBT. The devices have been aggressively scaled laterally for reduced base-collector capacitance C/sub cb/. In addition, the base sheet resistance /spl rho//sub s/ along with the base and emitter contact resistivities /spl rho//sub c/ have been lowered. The dc current gain /spl beta/ is /spl ap/36 and V/sub BR,CEO/=5.1 V. The devices reported here employ a 30-nm highly doped InGaAs base, and a 150-nm collector containing an InGaAs-InAlAs superlattice grade at the base-collector junction. From this device design we also report a 142-GHz static frequency divider (a digital figure of merit for a device technology) fabricated on the same wafer. The divider operation is fully static, operating from f/sub clk/=3 to 142.0 GHz while dissipating /spl ap/800 mW of power in the circuit core. The circuit employs single-buffered emitter coupled logic (ECL) and inductive peaking. A microstrip wiring environment is employed for high interconnect density, and to minimize loss and impedance mismatch at frequencies >100 GHz.     

Theory of Direct-Coupled-Cavity Filters

A new theory is presented for the design of direct-coupled-cavity filters in transmission line or waveguide. It is shown that for a specified range of parameters the insertion-loss characteristic of these filters in the case of Chebyshev equal-ripple characteristic is given very accurately by the formula P/sub 0/ / /P/sub L/ = 1+h/sup 2/T/sub n//sup 2/[/spl omega//sub 0/ / /spl omega/ sin(/spl pi/ /spl omega/ / /spl omega//sub 0/) / sin/spl theta//sub 0/'] where h defines the ripple level, T/sub n/ is the first-kind Chebyshev polynomial of degree n, /spl omega/ / /spl omega//sub 0/ is normalized frequency, and /spl theta//sub 0/' is an angle proportional to the bandwidth of a distributed lowpass prototype filter. The element values of the direct-coupled filter are related directly to the step impedances of the prototype whose values have been tabulated. The theory gives close agreement with computed data over a range of parameters as specified by a very simple formula. The design technique is convenient for practical applications.     

Characterization of copper germanide as contact metal for advanced MOSFETs

The material and electrical characteristics of /spl epsiv/-Cu/sub 3/Ge as a contact metal were investigated. The samples were prepared by direct copper deposition on germanium wafers, followed by rapid thermal annealing. The /spl epsiv/-Cu/sub 3/Ge formed at 400 /spl deg/C has a resistivity of 6.8 /spl mu//spl Omega//spl middot/cm, which is lower than typical silicides for silicon CMOS. Cross-sectional transmission electron microscopy showed smooth germanide/germanium interface, with a series of nanovoids aligning close to the top surface. These voids are believed to be the results of Kirkendall effect arising from the different diffusion fluxes of copper and germanium. The specific contact resistivity of Cu/sub 3/Ge, obtained from four-terminal Kelvin structures, was found to be as low as 8/spl times/10/sup -8/ /spl Omega//spl middot/cm/sup 2/ for p-type germanium substrate. This low resistivity makes Cu/sub 3/Ge a promising candidate for future contact materials.     

Compact microstrip-T coupled patch antenna for dual polarisation and active antenna applications

A novel way of feeding single-layer microstrip patch antennas using electromagnetically coupled microstrip-T junctions is proposed. The measured isolation and 10 dB bandwidth of an X-band dual polarised antenna are /spl sim/32 dB and 2.1%, respectively, on an /spl epsiv//sub r/ 3.0 substrate. Since both ports of the antenna are electromagnetically coupled, the proposed antenna eliminates the need for capacitors in the RF path for active antenna applications.     

Miniature and tunable filters using MEMS capacitors

Microelectromechanical system (MEMS) bridge capacitors have been used to design miniature and tunable bandpass filters at 18-22 GHz. Using coplanar waveguide transmission lines on a quartz substrate (/spl epsiv//sub r/ = 3.8, tan/spl delta/ = 0.0002), a miniature three-pole filter was developed with 8.6% bandwidth based on high-Q MEMS bridge capacitors. The miniature filter is approximately 3.5 times smaller than the standard filter with a midband insertion loss of 2.9 dB at 21.1 GHz. The MEMS bridges in this design can also be used as varactors to tune the passband. Such a tunable filter was made on a glass substrate (/spl epsiv//sub r/ = 4.6, tan/spl delta/ = 0.006). Over a tuning range of 14% from 18.6 to 21.4 GHz, the miniature tunable filter has a fractional bandwidth of 7.5 /spl plusmn/ 0.2% and a midband insertion loss of 3.85-4.15 dB. The IIP/sub 3/ of the miniature-tunable filter is measured at 32 dBm for the difference frequency of 50 kHz. The IIP/sub 3/ increases to >50 dBm for difference frequencies greater than 150 kHz. Simple mechanical simulation with a maximum dc and ac (ramp) tuning voltages of 50 V indicates that the filter can tune at a conservative rate of 150-300 MHz//spl mu/s.     

Guided Waves in Inhomogeneous Focusing Media Part III: Wall Effects, Losses, and the Transition from Fast to Slow Waves

This paper is concerned with the determination of field patterns, propagation constants, and losses for axially propagating modes guided by an enclosed circular cylindrical, radially inhomogeneous dielectric of the type discussed in Parts I and II. The homogeneous outer medium (/spl gamma/ /spl ges/ /a) is assumed to have a large relative permittivity /spl epsiv//sub 2/, and the analysis includes the perfect conductor case /spl epsiv//sub 2/ /spl rarr/ /spl infin/. The transition to trapped waves as the binding effect increases is demonstrated. Propagation constants in the case with loss are determined using a perturbation technique.     

Temperature dependence of permittivity and loss tangent of lithium tantalate at microwave frequencies

Lithium tantalate (LiTaO/sub 3/) exhibits excellent electro-optical, piezoelectric, and pyroelectric properties and a very low thermal expansion. In this paper, we report measurements of loss tangent and the real part of the relative permittivity /spl epsiv//sub r/spl perp// measured in c-axis LiTaO/sub 3/ crystals in the temperature range from 14 K to 295 K at a frequency of 11.4 and 10 GHz. Microwave properties of LiTaO/sub 3/ were determined by measurements of the resonance frequency and the unloaded Q/sub o/ factor of a TE/sub 011/ mode cylindrical cavity containing the sample under test and accounting for uncalibrated cables and adaptors inside the cryocooler. The permittivity of LiTaO/sub 3/ was found to increase from 38.9 to 41.1 and the loss tangent to change from 1.1/spl times/10/sup -4/ to 6.5/spl times/10/sup -4/ over the full temperature range. Due to its low loss and relatively high permittivity, LiTaO/sub 3/ is suitable for microwave applications.     

End Effect in a Shorted Slot (Short Papers)

An investigation of the end effect in a shorted-slot line is described. It is shown that the apparent position of the short is a small fraction of a wavelength beyond the end of the slot. The reactance seen at the end of the slot is, therefore, inductive. Experimental curves are presented which show normalized inductive reactance versus frequency for substrates with /spl epsi//sub r/ =12 and /spl epsi//sub r/=20 for several slot widths.