Computer-aided design of evanescent mode waveguide bandpass filterwith nontouching E-plane fins

The authors present an efficient computer-aided-design procedure that systematically utilizes a lookup table containing scattering parameters from variously dimensioned E-plane fins. The main idea is to achieve an optimal combination of filter parameters by proper selection of the E-plane fins from the table and appropriate determination of the other filter elements in order to satisfy the given filter specifications. The technique of selecting the proper fin from the table is explained. The relationship between the desired center frequency of the filter and the approximate resonant frequency of the single fin in the table is shown. The relationship between each design parameter and the filter characteristic is presented. The algorithm is applied to the design of a bandpass filter with two E-plane fins operating in the Ka-band. The algorithm is verified by comparing the characteristics of the designed filter with the experimental results     

Analysis and design of periodically time-varying IIR filters, withapplications to transmultiplexing

Fundamental constraints on the form of infinite impulse response (IIR) periodically time-varying (PTV) filters are identified, and a design technique with well-defined error and stability characteristics based on those constraints is presented. The design technique is based on the selection of poles and zeros within the time-invariant filter banks of equivalent PTV filter analysis structures. A simple example is presented to illustrate the design method, which implements the IIR PTV as a time-invariant all-feedback IIR filter of the form 1/D(z^P) cascaded with an finite impulse response (FIR) PTV filter. An application of IIR PTV filters to telecommunications transmultiplexing is presented to illustrate the design method and for comparison to an existing PTV design method. The computational complexity of the resulting system compares favorably with that of existing transmultiplexers     

K-band quasi-planar tapped combline filter and diplexer

Quasi-planar realizations of a combline bandpass filter and diplexer using multiple coupled suspended substrate striplines (MCSSSs) have demonstrated good performance at K-band without any tuning. The N MCSSSs excite N zero-cutoff-frequency quasi-TEM modes. A computer-aided filter design approach employing a rigorous spectral domain approach and 2N-port microwave circuit theory accounts for the effects of the N quasi-TEM modes, the couplings through nonadjacent MCSSSs, and cover height. Two 19.5-20.5 GHz MCSSS combline filters with different cover heights have been built and tested to compare their filter characteristics. The reduction in cover height has been found to decrease the amount of nonadjacent coupling through MCSSSs and to result in better filter stopband performance. An 18.5-19 GHz and 20-20.5 GHz MCSSS diplexer is also presented. All the measured results for the combline filters and diplexers agree well with the theoretic calculations     

Multidimensional multirate filters and filter banks derived fromone-dimensional filters

A method by which every multidimensional (M-D) filter with an arbitrary parallelepiped-shaped passband support can be designed and implemented efficiently is presented. It is shown that all such filters can be designed starting from an appropriate one-dimensional prototype filter and performing a simple transformation. With D denoting the number of dimensions, the complexity of design and implementation of the M-D filter are reduced from O(N^D) to O(N). Using the polyphase technique, an implementation with complexity of only 2N is obtained in the two-dimensional. Even though the filters designed are in general nonseparable, they have separable polyphase components. One special application of this method is in M-D multirate signal processing, where filters with parallelepiped-shaped passbands are used in decimation, interpolation, and filter banks. Some generalizations and other applications of this approach, including M-D uniform discrete Fourier transform (DFT) quadrature mirror filter banks that achieve perfect reconstruction, are studied. Several design example are given     

Scattering parameters of E-plane printed opposite fin inwaveguide

An analysis of the E-plane printed opposite fin in a waveguide is presented. The current distribution existing on the metal fin is obtained through a variational technique that utilizes the extremization process. The eigenvalue functions derived from the transverse resonance condition are used to include the effects of the dielectric layer. The computed data for a simplified case with Duroid substrate are compared with those obtained by means of the spectral-domain method. Based on the calculated results, a band-reject filter has been designed and tested at Ka-band. Good agreement on the filter response has been observed between theory and measurement     

Field theoretical CAD of open or aperture matched T-junctioncoupled rectangular waveguide structures

The rigorous computer-aided design of rectangular waveguide structures coupled by open or rectangular iris loaded E- or H-plane T-junctions is described. The design theory is based on the full wave mode-matching method for the key-building-block T-junction element associated with the generalized S-matrix technique for composite structures. The waveguide structures may be arbitrarily composed of the T-junction and already known key-building-block elements (such as the double step and the septum discontinuity) combined with homogeneous waveguide sections between them. The E- or H-plane T-junction effect, large apertures, finite iris or septum thicknesses, and higher-order mode interactions at all step discontinuities are rigorously taken into account. Typical design examples, like rectangular iris coupled T-junctions, narrow-stopband waveguide filters, high return loss E-plane T-junction diplexers, an elliptic function E-plane integrated metal insert filter and a simple ortho-mode transducer demonstrate the efficiency of the method. The theory is verified by measurements     

Pipelined recursive filter with minimum order augmentation

Pipelining is an efficient way for improving the average computation speed of an arithmetic processor. However, for an M-stage pipeline, the result of a given operation is available only M clock periods after initiating the computation. In a recursive filter, the computation of y(n) cannot be initiated before the computations of y(n-1) through y(n-N) are completed. H.B. Voelcker and E.E. Hartquist (1970) and P.M.Kogge and H.S. Stone (1973) independently devised augmentation techniques for resolving the dependence problem in the computation of y(n). However, the augmentation required to ensure stability may be excessively high, resulting in a very complex numerator realization. A technique which results in a minimum order augmentation is presented. The complexity of the resulting filter design is very much lower. Various pipelining architectures are presented. It is demonstrated by an example that when compared to the prototype filter, the augmented filter has a lower coefficient sensitivity and better roundoff noise performance     

Input I-V and sampling time characteristics ofthe ACT device

The input I-V and sampling-time characteristics of the acoustic charge transport (ACT) device are presented for ohmic-contact charge injection and Schottky-gate-modulated charge injection. A computationally efficient analysis technique is developed to calculate the I-V and sampling-time data from two-dimensional potential and carrier-density distributions. Device physics and architecture are incorporated into the analysis through a numerical charge-injection model which is used to compute the potential and carrier-density distributions. Theoretical results are presented to demonstrate the charge injection characteristic of some typical device structures. The effects that the injection method, the epitaxial layer structure and the acoustic wave amplitude have on device performances are discussed. The physical basis of the analysis enables it to be used to study several other design parameters. Experimental measurements of a device I-V and input transconductance show good agreement with calculated data. This analysis technique provides a means of assessing the performance potential of new device designs     

Spectral shaping and digital synthesis of an M-ary timeseries

The use of pulse shaping to control transmitted spectral density precisely is examined. A digital filter architecture is described that not only mitigates the traditional problems of lengthy development intervals and cost manufacturing methods, but offers the additional features of intrinsically coding high-speed binary (M=2) data into M-ary symbols while ensuring highly reproducible, baud-normalized, transmitter pulse shaping. A conceptual basis for the digital synthesis method is first described, including a functional circuit appropriate to the simplest filter realizations. Spectral effects internal to the filter are considered, and a simple method to obtain desired transmitted spectra is outlined. It is shown that even relatively short pulses used in high-level modulation systems lead to impractical memory storage demands; however, the simple expedient of segmenting the finite impulse function greatly reduced the individual memory requirements, though it necessitates intermediate adding operations. Experimental examples illustrate the design methodology for quaternary (M=4) data signals in a Nyquist communication channel and serve as points of reference for addressing performance and design flexibility     

Correction of (sin x)/x distortion introduced bydiscrete-time/continuous-time signal conversion

A new analytical method is proposed for the correction of the (sin x)/x distortion which is characteristic of the spectra of discrete-time signals converted to continuous-time waveforms. The method is based on the adjustment of the quality factors associated with the poles of the reconstruction filter transform function. Simulation results show that, in spite of its simplicity, the new technique yields significant improvements in the frequency spectrum of the continuous-time signal after the conversion     

Modal S-matrix design of metal finned waveguide componentsand its application to transformers and filters

Optimized all-metal E-plane finned waveguide components are designed with the rigorous method of modal field expansion into the ridged eigenmodes, which includes both the higher order mode interaction between the step discontinuities and the finite thickness of the fins. The design, which combines the advantage of constant fin thickness with that of the optimum matching potential of different waveguide inner cross-section dimensions and fin heights, achieves very broadband transformers and evanescent-mode filters with improved performance. Computer optimized data demonstrate the efficiency of the method by typical design examples: compact transformers for WR112, WR42, WR15, and WR12 input waveguides to E-plane finned waveguides, corrugated lowpass filters designed for a cutoff frequency in the waveguide Ku and U bands, and an evanescent-mode bandpass filter with unequal fin heights. The theory is verified by available measurements     

Si IC-compatible inductors and LC passive filters

Passive inductors and LC filters fabricated in standard Si IC technology are demonstrated. Q-factors from three to eight and inductors up to 10 nH in the gigahertz range have been realized. Measurements on a five-pole maximally flat low-pass filter give midband insertion loss and -3 dB bandwidth close to the nominal design values of 2.25 dB and 880 MHz     

Characterization of a novel passive RF filter for frequencies of4-225 MHz

The design and experimental characterization of a passive RF (4-225 MHz) filter pertinent to industrial and military aviation environments is presented. The filter utilizes three different low-pass stages and a simple DC discriminating circuit. A detailed theoretical analysis (lumped parameter modeling) of the filter's frequency response is provided. Even though it is not part of the initial design criteria, the filter also effectively blocks both out-of-band high-frequency (f>225 MHz) and low-frequency (f>4 MHz) harmonics     

The importance of the n-base in p-n-p-n-like structures subjectedto dV/dt ramps

A simple yet thorough analysis of physical effects induced in p-n-p-n-like silicon structures by the high rate of the OFF-state forward anode voltage rise (dV/dt) is discussed. The importance of n-base parameters in shaping the faulty triggering of thyristors subjected to dV/dt ramps is clearly demonstrated. The main implications of the findings for thyristor physics and design are also outlined     

Digital control of three-phase PWM inverter with LC filter

A digital control algorithm for the three-phase sinusoidal voltage inverter with an output LC filter has been developed. To take the transient of the LC filter during the discretization time into consideration, a fourth-order matrix state equation of the current and the voltage on the d-q frame is discretized. Precise discrete equations for the inverter are introduced. Using these equations, a deadbeat controller consisting of a d-g current minor loop and a d-q voltage major loop, with precise decoupling of the d-q components, was developed. The voltage major loop controller assures the sinusoidal output voltage and stabilizes the system. A deadbeat controller is used because both the current minor loop and the voltage major loop can used one sampling response. The validity of these techniques is confirmed by simulation studies. This method is expected to be useful for direct digital control of large-capacity sinusoidal voltage inverters using low-switching-frequency devices     

M-ary frequency shift keying withlimiter-discriminator-integrator detector in satellite mobile channelwith narrowband receiver filter

An expression is derived for the error probability of M-ary frequency shift keying with a limiter-discriminator-integrator detector and a narrowband receiver filter in the satellite mobile channel. This channel contains, as special cases, the Gaussian and Rayleigh (land mobile) channels. The error probability is computed as a function of various system parameters for M=2, 4, 8 symbols and a third-order Butterworth receiver filter     

A technique for realizing linear phase IIR filters

A real-time IIR filter structure is presented that possesses exact phase linearity with 10~1000 times fewer general multiplies than conventional FIR filters of similar performance and better magnitude characteristics than equiripple or maximally flat group delay IIR filters. This structure is based on a technique using local time reversal and single pass sectioned convolution methods to realized a real-time recursive implementation of the noncausal transfer function H(z^-1). The time reversed section technique used to realize exactly linear phase IIR filters is described. The effects of finite section length on the sectional convolution are analyzed. A simulation methodology is developed to address the special requirements of simulating a time reversed section filter. A design example is presented, with computer simulation to illustrate performance, in terms of overall magnitude response and phase linearity, as a function of finite section length. Nine example filter specifications are used to compare the performance and complexity of the time reversed section technique to those of a direct FIR implementation     

A coding scheme for m-out-of-n codes

A scheme for the construction of m-out-of-n codes based on the arithmetic coding technique is described. For appropriate values of n, k, and m, the scheme can be used to construct an (n,k) block code in which all the codewords are of weight m. Such codes are useful, for example, in providing perfect error detection capability in asymmetric channels such as optical communication links and laser disks. The encoding and decoding algorithms of the scheme perform simple arithmetic operations recursively, thereby facilitating the construction of codes with relatively long block sizes. The scheme also allows the construction of optimal or nearly optimal m-out-of-n codes for a wide range of block sizes limited only by the arithmetic precision used     

Design and characterization of optimal FIR filters with arbitraryphase

An algorithm for designing a Chebyshev optimal FIR filter that approximates an arbitrary complex-valued frequency response is presented. This algorithm computes the optimal filter by solving the dual to the filter design problem. It is guaranteed to converge theoretically and requires O(N²) computations per iteration for a filter of length N. For the first time, properties of the optimal filter are derived, and the case where the desired filter has arbitrary constant group delay is studied in detail