Real Frequency Technique Research Articles

A Real Frequency Approach to Describe Lossless Two-Ports Formed with Mixed Lumped and Distributed Elements

Summary The design of microwave filters, matching networks, amplifiers, that is the “Broadband Networks” with mixed lossless lumped and distributed elements, has been a significant concern of the circuit theoreticians of the field. Yet, there has been no complete practical solution introduced in the literature so far. In this paper, an attempt has been made to design broadband networks constructed with a cascade connection of low pass LC ladders connected with commensurate transmission lines. The new design procedure is based on the two-variable description of the Simplified Real Frequency Technique. Up to five mixed-elements explicit equations are given to describe some selected network topologies. In general, synthesis is carried out employing a decomposition technique first introduced by Alfred Fettweis. A “Double Matching Design” exampleis presented to exhibit the merits and the application of the new approach.

Design of broadband phasing network by real frequency technique

The application of the real frequency technique in broadband phasing network design is proposed. The technique uses real frequency load data over any prescribed frequency band for the design of a phasing network. The advantage is that no circuit topology or analytic form of the transfer function is required.

Efficient numerical CAD technique for RF and microwave amplifiers

The real frequency technique (RFT) is an efficient numerical method to design the matching networks of microwave active circuits. It provides several advantages over most of the usual techniques. By directly including measured scattering and noise parameter data, it does not require any rational functions or circuit models. Moreover, a predetermined matching circuit topology is not necessary. The described method also allows the design of stability-guaranteed broadband circuits when employing potentially unstable transistors. With the Levenberg–Merquardt algorithm, the RFT can be applied to simultaneously optimize transducer power gain, input and output VSWRs, noise figure, and group delay of a multistage microwave active circuit. Applications as different as low-noise amplifier, active filter, or broadband amplifier are possible. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 131–141, 1998.

Design of broad-band matching network with lossy junctions using the real-frequency technique

A computer-aided design (CAD) procedure based on the real-frequency technique (RFT) is introduced for treating the matching of an arbitrary load to a complex generator. In this paper, the method has been applied to the design of interstage matching networks for microwave active circuits. The RFT provides several advantages over most of the usual techniques. It requires neither any transistor model because it directly includes measuring scattering- and noise-parameter data, nor a predetermined matching-circuit topology is necessary. A low-noise amplifier (LNA) design proceeding directly from experimental data is presented. Moreover, a new idea for treating the broadband matching problem leads to the use of an equalizer topology containing cascaded transmission lines with lossy junctions. Thus, gain-flatness and stability are satisfied by designing the input and the output matching circuits by the line-segment technique. An example is presented for the matching of a 0.1-5 GHz amplifier.

Broadband microwave and optoelectronic devices design by the real frequency technique

Broadband microwave and optoelectronic devices design by the real frequency technique

Broadband microwave and optoelectronic devices design by the real frequency technique

Broadband microwave and optoelectronic devices design by the real frequency technique

A new method for solving broadband matching problems

A new method for computing the component values of LC ladder equalizers for broadband matching purposes is presented. The method is inspired by the theory of recursive identification and results in a very compact algorithm. As in the usual real frequency technique, the load and generator impedances have to be known only at a small number of frequencies. Starting from an assumed topology for the equalizer with random values for the components, the equalizer components are iteratively built with a recursive identification algorithm, in order to satisfy asymptotically a least mean squares criterion. In contrast to the usual deterministic least mean squares algorithms used in existing equalization techniques a stochastic algorithm has been developed. This stochastic treatment leads to very simple equalization techniques. On the basis of the solution found with the stochastic recursive identification algorithm a random search of a limited region of the component hyperspace is initiated in order to refine the solution. The paper includes many examples in which the above method has been successfully applied. As a special feature, the method has been applied to equalizers made up of series and parallel resonant circuits.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Broadband microstrip antenna design with the simplified real frequency technique

Broadband microstrip antenna design with the simplified real frequency technique

Broadband active microstrip antenna design with the simplified real frequency technique

This paper deals with the design of broadband active microstrip antennas where the amplifier is integrated with the radiator. Theoretically sound definitions for gain and noise figure of the active antenna are introduced, and their relationships with the definitions for the composing circuit and radiator parts are explained. A sequential design procedure is presented that allows the straightforward and optimal design of transmitting and receiving antennas with multiple active stages, taking into account input and output matching, the gain-versus-frequency curve as well as the noise performance. The theoretical concepts are illustrated with two examples: one of a transmitting active antenna and one of a receiving antenna. The former one is a two-stage design that achieves nearly 25% of bandwidth with regard to gain and matching and 24 dB gain improvement as compared to the matched passive antenna. The second one is a receiving antenna (one stage) with a measured noise figure of 1.2 dB in a bandwidth of over 17% and a gain improvement of 11.9 dB over the corresponding passive antenna. Finally co- and cross-polar radiation patterns in E- and H-plane prove that the antennas also have favorable radiation characteristics in a wide bandwidth (at least 18%). >

A design method for lumped broadband MMIC matching networks with semiuniform frequency-dependent losses

A design method for broadband MMIC matching networks which consist of lumped inductors and capacitors is presented. Based on a fictitious transformation between the lossy network and the lossless one, the transducer power gain (TPG) of the lossy network is calculated using impedance matrix and transmission parameter matrix methods. Then, on the basis of the result of TPG optimization, the matching network can be synthesized. Since only the complexity of the matching network needs to be specified, the advantage of the real frequency technique of B.S. Yarman and H.J. Carlin (1982) is retained. In this design procedure the frequency-dependent losses of lumped elements can be considered. Thus the actual gain response tends to coincide with the desired performance more than when the element losses are neglected. An example is given to show the application of the method to broadband GaAs FET amplifier design.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Broadband circularly polarised microstrip antenna in two-sided structure with coaxial probe coupling

A broadband circularly polarised (CP) microstrip antenna in a two-sided structure is presented. The newly developed transmission line model of the microstrip antenna and the simplified real frequency technique are employed to design the lossless matching networks. Measurements show that the designed CP antenna has broad gain bandwidth, good polarisation purity, and low input VSWR.

Stable broadband microwave amplifier design using the simplified real frequency technique

B.S. Yarman's (RCA Rev., vol.43, p.529-41, Sept. 1982) simplified real frequency technique is modified and used to design a stability-guaranteed broadband microwave amplifier consisting of a potentially unstable transistor. The source and load terminations can be complex impedances. The stability is maintained by the conductances resulted from transforming the source and load terminations through the input and output matching circuits. The input and output matching circuits are derived concurrently, instead of sequentially. Repeating the design of an example from a previous paper shows that the transducer gain obtained by using this method is higher, with fewer matching circuit elements, than that obtained by using supercompact optimizers. Moreover, with the same number of matching circuit elements, the transducer gain is slightly higher than that obtained by using the dynamic CAD technique.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An algorithm for wideband matching using Wiener-Lee transforms

An arbitrary passive load to be matched by a lossless equalizer to a resistive source so that system response approximates any desired gain shape over a prescribed band, e.g., rectangular, is considered. A least-squares optimization procedure is described that determines the equalizer design. The method stems from the real frequency technique and uses trigonometric basis functions (Wiener-Lee transforms) for expanding the real and imaginary parts of the unknown equalizer immittances. The algorithm is relatively simple and efficient since it is implemented using the fast Fourier transform. It also incorporates physical realizability considerations. The procedure is such that a large number of variables (Fourier coefficients) can be employed. This permits a determination of the limiting value of flat gain (a useful design yardstick) as the number of equalizer elements becomes infinite.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An integrated design tool to construct lossless matching networks with mixed lumped and distributed elements

A design tool that combines the simplified real frequency technique of broadbanding with an appropriate application of algebraic network decomposition and replacement techniques is presented. The method incorporates the outstanding merits of modern single-variable broadbanding techniques, i.e. during the course of the design, there is no need to choose a circuit topology with mixed elements in advance, nor is it necessary to invent a realizable transfer function in two variables to measure the system performance. Examples are presented to exhibit the application of the tool, which is expected to be useful for constructing practical MMIC matching networks, since the fringing lumped element parasitics which arise due to the physical implementation can easily be adsorbed within the mixed element network structure. >

CAD technique for designing microwave transistor active filters

A CAD method for designing microwave active filters, based on an extension of the simplified real frequency technique, is presented. This approach is analogous to the design of the matching networks in microwave amplifiers: the filter is developed by cascading active devices with passive two-ports which have a particular form of the transfer function. The potential of the method is illustrated by a computer simulated design of bandpass active filters.

Matching network design of microstrip antennas with simplified real frequency technique

A new approach for increasing the bandwidth of microstrip antennas by using the simplified real frequency technique is presented. The method is numerical, its most significant feature is that it does not require any form of equivalent circuit or analytical impedance functions for the antennas and generators, and the measured or calculated impedance data are processed directly. Furthermore, neither an a priori choice of a matching network topology nor an analytic form of the system transfer function is needed. A representative example shows the validity of the design procedure.

Stable broad-band microwave amplifier design

A modified real-frequency technique for designing a broadband microwave amplifier with guaranteed stability is presented. This method generates the two sets of resistive excursions necessary for synthesizing the source and load admittances of the amplifier concurrently, rather than sequentially, while both the stability and realizability requirements are satisfied simultaneously. Regardless of its constrained nature, the method has been formulated as an unconstrained optimization problem. An 8-12-GHz-band amplifier design example is presented to demonstrate its application. The transducer power gain obtained in the example by this method is 11.3+or-0.4 dB, which is 2.6-dB higher than that obtained by using the real-frequency technique.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Computer-aided double matching via parametric representation of Brune functions

A new computer-aided broadband matching technique, the so-called parametric approach, is applied to double-matching problems. The technique takes less computation time and yields superior gain performance over the other available brute-force CAD techniques. Examples are presented to exhibit the practical use of the parametric approach. The results obtained are compared with those obtained via the real-frequency-direct-computational technique, which offers superior design performance with simple equalizer structures. The real-frequency techniques of broadbanding are implemented with several computational phases in which data-fitting processes, explicit factorization of real polynomials, and solution of a set of linear equations are required. The proposed parametric approach is a reformulation of the real-frequency techniques that eliminates the laborious numerical computations of the latter. The approach involves the parametric representation of Brune functions. Neither the use of explicit factorization of polynomials nor the solution of linear equation systems is necessary. Thus, the parametric method of broadband matching requires less computation with improved numerical stability. >

Computer-aided design of hybrid and monolithic broad-band amplifiers for optoelectronic receivers

In very-high-data-rate fiber-optic systems, it is necessary to have an ultrawideband, high-gain, low-noise amplifier after the front end. The authors show how powerful analytical techniques, such as the real frequency technique, can be applied to the design of a 4-MHz-7-GHz amplifier. A two-stage monolithic amplifier designed according to the theory gives 17-dB gain; a three-stage hybrid amplifier exhibits 16-dB gain across the same frequency band. The gain, noise figure, and pulse response of each amplifier are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Real frequency technique applied to the synthesis of lumped broad-band matching networks with arbitrary nonuniform losses for MMICs

A computer-aided synthesis technique for lumped matching networks with arbitrary nonuniform losses is presented. It is especially applicable to the design of broadband amplifiers in MMIC form. A useful theorem and two corollaries for the transformation between lossy and lossless networks are developed, so that the design of the lossy matching networks is considerably simplified and can yield complex models of the lumped elements with arbitrary nonuniform losses. An example showing the application of the method to monolithic broadband amplifier design is given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>