Broadband quasi-Chebyshev bandpass filters with multimode stepped-impedance resonators (SIRs)

Planar broadband bandpass filters of order up to 9 are synthesized based on the multimode property of stepped-impedance resonators (SIRs). Based on the transmission line theory, the modal frequencies of the SIRs are calculated based on the impedance and length ratios of its hi- and low-Z segments. In the synthesis, the SIR coupling schemes are determined by the split mode graphs. Using one, two, two, three, and three dual- or triple-mode SIRs, quasi-Chebyshev filters with four, six, six, eight, and nine transmission poles, respectively, are synthesized with a fractional bandwidth (BW) /spl Delta/=50%. Emphasis is placed not only on designing the I/O coupling structures for matching the external Q (Q/sub ext/) and the circuit BW, but also on matching the resonant peaks of the circuit with the nominal Chebyshev poles. Measured results of experimental circuits show good agreement with simulated responses.     

Coaxial Bandpass Filter Design

A technique is described for synthesis of coaxial bandpass filters based on an improved design of impedance inverters. This technique is applicable to filters having bandwidths between approximately 1 percent and 20 percent of the center frequency. The inverter used to realize the filters is a section of either low-Z/sub 0/ line or high-Z/sub 0/ line and is synthesized as a distributed element rather than as a lumped shunt capacitance or lumped series inductance, respectively. Three methods of accommodating the discontinuity capacitance associated with an abrupt change in the characteristic impedance are reviewed. The first two methods are most useful for filters with a fractional bandwidth/spl gsim/ 10 percent and the third for a fractional bandwidths /spl lsim/10 percent. Numerical and experimental verification of the design procedure is provided.     

Periodic stepped-impedance ring resonator (PSIRR) bandpass filter with a miniaturized area and desirable upper stopband characteristics

A periodic stepped-impedance ring resonator (PSIRR) is proposed to design dual-mode bandpass filters with a miniaturized area and desirable upper stopband characteristics. Design parameters of a PSIRR include impedance ratio R of the hi-Z to low-Z sections, their lengths, and number of impedance steps 2N. The resonant characteristics of PSIRRs with various N and R values are investigated by both the transmission-line theory and electromagnetic simulation. Proper choice of the above parameters leads to an optimal reduction of circuit area and extension of upper rejection bandwidth. Two extra transmission zeros exist in the upper stopband and are tunable via changing the arm lengths of the line-to-ring coupling structure. Realized by the standard microstrip technology, the dual-mode PSIRR bandpass filter has not only the first spurious response at higher than 3.7/spl times/ the passband frequency, but also an area reduction of better than 60% against a conventional ring filter. Experimental results of several fabricated circuits validate the analysis and theoretical prediction.     

A Two-Stage SIR Bandpass Filter With an Ultra-Wide Upper Rejection Band

Two-stage stepped-impedance resonator (SIR) filters are designed to have a wide upper stopband. Two transmission zeros are also created near the passband to form a quasi-elliptic response. For a 20-dB rejection level, with properly designed SIR geometry and tapped-line structure, the leading three spurious resonances of the SIR are suppressed by transmission zeros and respective unmatched singly loaded Q (Q_si) values. Measured results illustrate that stopbands up to 8.4 and 5.3 times the design frequency can be achieved for rejection levels of 20 and 30dB, respectively     

Precise Design of a Bandpass Filter Using High-Q Dielectric Ring Resonators

A precise design is presented for a bandpass filter constructed by placing TE/sub 01delta/ dielectric ring resonators coaxially in a TE/sub 01/ cutoff circular waveguide. On the basis of a rigorous analysis by the mode- matching technique, the interresonator coupling coefficients are determined accurately from the calculation of two resonant frequencies f/sub sh/ and f/sub op/ when the structurally symmetric plane is short- and open-circuited. For the TE/sub 01delta/ ring resonator,the resonant frequency f/sub 0/, the temperature coefficient tau/sub f/, the unloaded Q(Q/sub u/), and the other resonances are also calculated accurately in a similar way. From the calculations, the optimum dimensions are determined to obtain the maximum Q/sub u/, as F/sub r/ = f/sub r/ /f/sub 0/ is kept constant, where f/sub r/ is the next higher resonant frequency the ring resonator using low-loss ceramics (epsilon/sub r/ = 24.3, tan delta = 5 x 10/sup -5/) has Q/sub u/ = 16800 at 12 GHz and tau/sub f/ = 0.1+-0.5 ppm/° C, while the rod one has Q/sub u/ = 14700. A four-stage Chebyshev filter having ripple of 0.04 dB and equiripple bandwidth of 27.3 MHz at f/sub 0/ =11.958 GHz is fabricated using these resonator; the measured frequency responses agree well with theory. The insertion loss is 0.9 dB, which corresponds to Q/sub u/ = 9800.     

A novel frequency doubler using feedforward technique and defected ground structure

A novel design of frequency doubler using feedforward technique and defected ground structure (DGS) is proposed. The feedforward loop in the proposed frequency doubler suppresses the fundamental component (f/sub o/), and the DGS diminishes the higher order harmonics such as third, fourth, and so on. Due to the combination of feedforward structure and DGS, only the doubled frequency component (2f/sub o/) appears at the output port and the other unwanted components are suppressed excellently. A frequency doubler is designed at 1.85GHz of f/sub o/ by the proposed technique and measured. The measured output power of 2f/sub o/ is -3 dBm when the input power is 0 dBm. The obtained suppression of f/sub o/, 3f/sub o/, and 4f/sub o/ are 42.9, 19.2, and 29.7dB, respectively.     

Novel coplanar-waveguide bandpass filters using loaded air-bridge enhanced capacitors and broadside-coupled transition structures for wideband spurious suppression

Novel inline coplanar-waveguide (CPW) bandpass filters composed of quarter-wavelength stepped-impedance resonators are proposed, using loaded air-bridge enhanced capacitors and broadside-coupled microstrip-to-CPW transition structures for both wideband spurious suppression and size miniaturization. First, by suitably designing the loaded capacitor implemented by enhancing the air bridges printed over the CPW structure and the resonator parameters, the lower order spurious passbands of the proposed filter may effectively be suppressed. Next, by adopting the broadside-coupled microstrip-to-CPW transitions as the fed structures to provide required input and output coupling capacitances and high attenuation level in the upper stopband, the filter with suppressed higher order spurious responses may be achieved. In this study, two second- and fourth-order inline bandpass filters with wide rejection band are implemented and thoughtfully examined. Specifically, the proposed second-order filter has its stopband extended up to 13.3f/sub 0/, where f/sub 0/ stands for the passband center frequency, and the fourth-order filter even possesses better stopband up to 19.04f/sub 0/ with a satisfactory rejection greater than 30 dB.     

Wide-stopband microstrip bandpass filters using dissimilar quarter-wavelength stepped-impedance resonators

Wide-stopband and compact microstrip bandpass filters (BPFs) are proposed using various dissimilar quarter-wavelength (/spl lambda//4) stepped-impedance resonators (SIRs) for multiple spurious suppression. The use of /spl lambda//4 SIRs is essential in widening the filter stopband and reducing the circuit size. By properly arranging the individual /spl lambda//4 SIR, which has the same fundamental resonance frequency f/sub 0/, but has different spurious (harmonic) resonance frequencies, and also carefully misaligning the maximum current density nodes, several higher order spurious resonances may be suppressed so that a BPF with wide stopband may be realized. In this study, the basic concept of multiple spurious suppression is demonstrated by thoroughly investigating the spurious characteristics of the fourth-order interdigital BPFs, which consist of two different types of /spl lambda//4 SIRs. To widen the rejection bandwidth, the fourth-order coupled-resonator BPFs based on three and four different types of /spl lambda//4 SIRs are implemented and carefully examined. Specifically, a very wide-stopband microstrip BPF composed of four dissimilar /spl lambda//4 SIRs is realized and its stopband is extended even up to 11.4f/sub 0/ with a rejection level better than 27.5 dB.     

Equivalent Circuit of Orthogonal-Loop-Coupled Magnetic Resonance Filters and Bandwidth Narrowing Due to Coupling Inductance

The equivalent circuit of an orthogonal-loop-coupled magnetic resonance filter is shown to consist of a gyrator, two ferrite-induced inductances, and two coupling loop inductances. The effects of the coupling inductances on the passband and stopband responses are shown to be significant by means of calculations based on this equivalent circuit. It is proved that the maximum passband bandwidth /spl Delta//spl conint//sub -3dB/ = /spl conint//sub 0/ (L/sub f/ / L/sub c/), where /spl conint//sub 0/, is the center frequency, and L/sub f/ and L/sub c/ the ferrite-induced and the coupling-loop inductance, respectively. Other unusual insertion-loss characteristics of this filter which differ from those of a conventional reciprocal-element bandpass filter are shown. Finally, a test circuit for determining experimentally the coupling inductance ratio L/sub c/ /L/sub f/ and the external Q, Q/sub f/ of a ferrite resonator is presented.     

Magnetically Tunable Nonreciprocal Band-Pass Filters Using Ferrimagnetic Resonators

Possibilities of a small-bandwidth, small-insertion loss, magnetically tunable band-pass filters with nonreciprocal characteristics have been studied. the unloaded Q(Q/sub u/) for a ferrimagnetic sample has been derived, considering the fundamental definition of Q for a resonator. Theoretical analysis is given for coupling due to ferrimagnetic resonance, between two RF transmission circuits when the RF magnetic fields due to the two circuits are circularly polarized or, in general, elliptically polarized. The analysis gives the open-circuit impedance parameters for the equivalent circuit representing the ferrimagnetic coupling mechanism, from which the external-loading Q's (Q/sub e1/ and Q/sub e2/) are obtained. This analysis, applied to the case of the waveguides, shows that the behavior of the Q/sub e/ vs frequency characteristic depends upon the ellipticity of the RF magnetic field, and hence, upon the location of the off-axis position of the ferrimagnetic resonator. Also, the nonreciprocity depends upon the ellipticity of the RF magnetic field--the nonreciprocal behavior being optimum when the RF magnetic field is circularly polarized. Thus, again, for the case of waveguide circuits, the off-axis position determines the reverse-coupling-vs-frequency characteristic. The measurements on the experimental filters, tunable from 8.2 to 12.4 kMc, verify the results obtained from the theory. The forward and the reverse directions of the operation of these filters can be interchanged by reversing the dc magnetic field. Power limiting with these filters is briefly described.     

A relationship between quantization and watermarking rates in the presence of additive Gaussian attacks

A system which embeds watermarks in n-dimensional Gaussian data and distributes them in compressed form is studied. The watermarked/compressed data have to satisfy a distortion constraint, and the watermark has to be recoverable in a private scenario (in which the original data are available at the watermark detector). The performance of the system in the presence of additive Gaussian attacks is considered, and the region of achievable quantization and watermarking rate pairs (R/sub Q/,R/sub W/) is established. Moreover, two surprising facts are demonstrated: (1) at low R/sub Q/, the maximum achievable R/sub W/ is the same as when there are no attacks; and (2) at high (but finite) R/sub Q/, the maximum achievable R/sub W/ is the same as when there is no compression (R/sub Q/=/spl infin/). Finally, the performance of related schemes is also discussed.     

On The General Relation Between /spl alpha/ and Q (Correspondence)

The relation between the quality factor Q and the attenuation constant /spl alpha/ of a transmission line has been known as follows: /spl alpha/ = /spl beta/ / /2Q where /spl beta/ is the phase constant. Recently from the following relation of propagation constant at resonance /spl Gamma/(/spl omega//sub 0/) + /spl part//spl Gamma/ / /spl part//spl omega/ /spl Delta//spl omega//spl cong/ i/spl beta/(/spl omega//sub 0/), where /spl Gamma/(/spl omega//sub 0/) = /spl alpha/(/spl omega//sub 0/) + i/spl beta/(/spl omega//sub 0/). Yeh derived a general relation between Q and /spl alpha/, namely, /spl alpha/ = /spl upsi//sub p/ / /spl upsi//sub g/ /spl beta/ / /2Q where /spl upsi//sub p/, and /spl upsi//sub g/ are the phase velocity and group velocity of the wave respectively. This general relation can be derived very simply from the generally accepted definition of /spl alpha/ and Q.     

The empirical distribution of rate-constrained source codes

Let X = (X/sub 1/,...) be a stationary ergodic finite-alphabet source, X/sup n/ denote its first n symbols, and Y/sup n/ be the codeword assigned to X/sup n/ by a lossy source code. The empirical kth-order joint distribution Q/spl circ//sup k/[X/sup n/,Y/sup n//spl rceil/(x/sup k/,y/sup k/) is defined as the frequency of appearances of pairs of k-strings (x/sup k/,y/sup k/) along the pair (X/sup n/,Y/sup n/). Our main interest is in the sample behavior of this (random) distribution. Letting I(Q/sup k/) denote the mutual information I(X/sup k/;Y/sup k/) when (X/sup k/,Y/sup k/)/spl sim/Q/sup k/ we show that for any (sequence of) lossy source code(s) of rate /spl les/R lim sup/sub n/spl rarr//spl infin//(1/k)I(Q/spl circ//sup k/[X/sup n/,Y/sup n//spl rfloor/) /spl les/R+(1/k)H (X/sub 1//sup k/)-H~(X) a.s. where H~(X) denotes the entropy rate of X. This is shown to imply, for a large class of sources including all independent and identically distributed (i.i.d.). sources and all sources satisfying the Shannon lower bound with equality, that for any sequence of codes which is good in the sense of asymptotically attaining a point on the rate distortion curve Q/spl circ//sup k/[X/sup n/,Y/sup n//spl rfloor//spl rArr//sup d/P(X/sup k/,Y~/sup k/) a.s. whenever P(/sub X//sup k//sub ,Y//sup k/) is the unique distribution attaining the minimum in the definition of the kth-order rate distortion function. Consequences of these results include a new proof of Kieffer's sample converse to lossy source coding, as well as performance bounds for compression-based denoisers.     

Application of Ferrite to Electromagnetic Wave Absorber and its Characteristics

An electromagnetic wave absorber utilizing ferrite or rubber ferrite composed of ferrite powder and rubber is described. In our investigation, the existence of a matching frequency f/sub m/ and a matching thickness t/sub m/ has been found. The terms f/sub m/ and t/sub m/ mean that the ferrite which is backed with a conducting plate can be a perfect absorber only under the conditions that the frequency of the incident wave is f/sub m/ and that the thickness of the ferrite is t/sub m/.Each ferrite has two matching frequencies f/sub m1/, f/sub m2/, (f/sub m1相似文献   

新型高选择性双模宽带带通滤波器设计

首先利用阶梯阻抗谐振器和交叉耦合馈线结构设计了一种带宽达73．2％新型双模带通滤波器。该谐振器在通带内产生两个可调模式,馈线结构在阻带对称产生两个传输零点。接着在馈线上加载短路线,使原有的两个传输零点向截止频率靠近,并在上阻带新增一个零点,从而在保持原滤波器通带性能的同时提高了频率选择性和上阻带特性。通过对比两个滤波器S参数进一步验证改进效果。最后制作测试了该短路线加栽的滤波器,仿真和实测结果吻合良好。     

Compact bandpass filters with wide controllable fractional bandwidth

In this letter, complementary split ring resonators (CSRR) are proposed to design bandpass filters (BPFs) having wide controllable 3-dB fractional bandwidth (FBW). FBW can be varied between 10% and 100%. In addition, filters have the advantages of compactness, sharp rejection, low insertion loss (IL), and low cost. Two prototype fabricated filters of FBW 10.8% and 81.6% show a maximum passband IL of 1.2dB. Filter occupying area is less than 0.25/spl lambda//sub g//spl times/0.15/spl lambda//sub g/, where /spl lambda//sub g/ is the guided wavelength at the midband frequency.     

Mode Propagation in a Nonuniform Cylindrical Medium (Correspondence)

A simplified form of the coupling coefficient C(/spl beta//sub p/, /spl beta//sub q/) resulting from a coupled mode theory analysis of wave propagation in a nonuniform medium is derived. It is found for most situations of interest that C(/spl beta//sub p/, /spl beta//sub q/) is proportional to 1/(/spl beta//sub p/-/spl beta//sub q/) and the power transfer between two modes is proportional to 1/(/spl beta//sub p/ - /spl beta//sub q/)/sup 4/. /spl beta//sub p/ and /spl beta//sub q/ are the two different modal propagation constants. For a dielectric rod C(/spl beta//sub p/, /spl beta//sub q/) is a simple line integral around the rod boundary. Approximate forms are presented for optical waveguides.     

Compression mappings on primitive sequences over Z/(p/sup e/)

Let Z/(p/sup e/) be the integer residue ring with odd prime p/spl ges/5 and integer e/spl ges/2. For a sequence a_ over Z/(p/sup e/), there is a unique p-adic expansion a_=a_/sub 0/+a_/spl middot/p+...+a_/sub e-1//spl middot/p/sup e-1/, where each a_/sub i/ is a sequence over {0,1,...,p-1}, and can be regarded as a sequence over the finite field GF(p) naturally. Let f(x) be a primitive polynomial over Z/(p/sup e/), and G'(f(x),p/sup e/) the set of all primitive sequences generated by f(x) over Z/(p/sup e/). Set /spl phi//sub e-1/ (x/sub 0/,...,x/sub e-1/) = x/sub e-1//sup k/ + /spl eta//sub e-2,1/(x/sub 0/, x/sub 1/,...,x/sub e-2/) /spl psi//sub e-1/(x/sub 0/,...,x/sub e-1/) = x/sub e-1//sup k/ + /spl eta//sub e-2,2/(x/sub 0/,x/sub 1/,...,x/sub e-2/) where /spl eta//sub e-2,1/ and /spl eta//sub e-2,2/ are arbitrary functions of e-1 variables over GF(p) and 2/spl les/k/spl les/p-1. Then the compression mapping /spl phi//sub e-1/:{G'(f(x),p/sup e/) /spl rarr/ GF(p)/sup /spl infin// a_ /spl rarr/ /spl phi//sub e-1/(a_/sub 0/,...,a_/sub e-1/) is injective, that is, a_ = b_ if and only if /spl phi//sub e-1/(a_/sub 0/,...,a_/sub e-1/) = /spl phi//sub e-1/(b_/sub 0/,...,b_/sub e-1/) for a_,b_ /spl isin/ G'(f(x),p/sup e/). Furthermore, if f(x) is a strongly primitive polynomial over Z/(p/sup e/), then /spl phi//sub e-1/(a_/sub 0/,...,a_/sub e-1/) = /spl psi//sub e-1/(b_/sub 0/,...,b_/sub e-1/) if and only if a_ = b_ and /spl phi//sub e-1/(x/sub 0/,...,x/sub e-1/) = /spl psi//sub e-1/(x/sub 0/,...,x/sub e-1/) for a_,b_ /spl isin/ G'(f(x),p/sup e/).     

An analysis of small-signal source-body resistance effect on RF MOSFETs for low-cost system-on-chip (SoC) applications

In this paper, we demonstrate a comprehensive analysis of small-signal source-body resistance (R/sub sb/) effect on the RF performances of RF MOSFETs for low-cost system-on-chip (SoC) applications for the first time. Our results show that for RF MOSFETs, both the kink phenomena of S/sub 11/ and S/sub 22/ become more obscure as reverse body bias (V/sub B/) increases due to the decrease of transconductance (g/sub m/). In addition, an increase of source-body spacing enhances both the kink phenomena of S/sub 11/ and S/sub 22/, but deteriorates the current-gain cut-off frequency (f/sub T/), maximum oscillation frequency (f/sub MAX/), and RF noise and power performances due to the increase of R/sub sb/ of the devices. Analytical formulas are derived to explain the kink phenomena of S/sub 11/ and S/sub 22/, and to explain why increasing R/sub sb/ leads to a reduction of equivalent substrate resistance R/sub sub/, or worse f/sub T/, f/sub MAX/, and RF noise performances of the devices. The present analyzes enable RF engineers to understand the S-parameters, noise parameters, and power performances of RF MOSFETs more deeply, and hence are helpful for them to optimize the layout of MOSFETs and to create a fully scalable RF CMOS model for SoC applications.