Multi-band Circuits Research Articles

Dual-Band Design Techniques for Microwave Passive Circuits: A Review and Applications

The introduction of new technology in the wireless communication industry increases the number of frequency bands in the communication environment. Therefore, a communication system capable of functioning over several frequency bands, known as a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">multiband communication system</i> , is required. In addition, multiband communication systems support technology upgrades by smoothly bridging the migration from the existing technology to a newer technology. A multiband communication system can be developed with the help of two approaches. The first approach is a multiband communication system that contains multiple microwave circuits, with each circuit optimized for a single band; for example, a dual-band communication system has two low-pass filters and two power amplifiers. But this approach increases not only the size but also the cost of the system. In the second approach, rather than using a separate power amplifier and filter for each frequency band, a single power amplifier, filter, and other components are used that can support more than one frequency band. These circuits are known as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">multiband microwave circuits</i> . Multiband circuits not only minimize size but also reduce the cost of designing the multiband communication system.

Procedure of definition of structure and parameters of multi-band matching circuits on the basis of intracavitary complex criterion for conformity to the ideal filter

The article gives the procedure of structurally parametric synthesis of multi-band frequency-selective circuits. A short characteristic of approaches to solve the problems of synthesis of the multi-band frequencyselective circuits based on the use of multifrequency resonators, frequency transformations and parametric transformations using numerical procedures of optimisation is given. The research presents a short description of three widely used estimation criteria of the characteristics of frequency-selective circuits: Taylor, Chebyshev and average-degree criteria. Expedients of an estimate of joint approximation of amplitude-frequency and phasefrequency characteristics of synthesized circuits to those of the ideal filter are shown. The criterion is suggested and the procedure is presented for structurally parametrical synthesis of multi-band matching circuits on the basis of intracavitary complex criterion of conformity to the ideal filter in a transmission band and interband Chebyshev criterion realized by numerical optimization of synthesized circuits relative to the chosen criterion for affinessy is given. With that, the multi-band circuit is represented in form of a ladder-type connection that, generally, consists of n different reactive resistances. The example of using the proposed procedure to solve the problem of structurally parametric synthesis of a two-band matching circuit is given. As a matching load we selected the first-type equivalent consisting of a serial connection of active resistance and capacity. In the example there is an additional requirement to ensuring interband frequency selectivity. Such requirement is ensured by introducing zero to the function of transmission of the synthesized circuit on an interband average geometric frequency. The requirement is implemented by introducing a parallel oscillating circuit to the first serial arm of the synthesized circuit. The structurally parametric synthesis of the two-band matching circuit selected in the example is carried out through Mathcad 15 software based on the integrated method of Levenberg-Marquardt optimization.

Mode Composite Sandwich Slot Line and its Applications in Antenna Development

In this article, a class of mode composite transmission line called mode composite sandwich slot line (MCSSL) is proposed, studied, and demonstrated. The MCSSL is composed of two substrate integrated waveguides (SIWs) and a sandwiched quasi-slot line. Structural parts of the two SIWs inherently serve as the two conductors of the quasi-slot line. The SIW supports the TE10 fundamental mode propagation, whereas the quasi-TEM mode is supported by the quasi-slot line. Two types of transition structures are proposed in this article, which enable an easier integration of the studied MCSSL with other transmission lines. An MCSSL-based antenna is designed and fabricated to theoretically and experimentally demonstrate its advantages and feasibility. It has been shown that the MCSSL features the physical and electrical characteristics of a joint structure (or structure sharing) in connection with a mode composite with planar structures, and it can find applications in broadband and multiband circuits and antenna developments.

Rapid simulation‐driven design of miniaturised dual‐band microwave couplers by means of adaptive response scaling

One of the major challenges in the design of compact microwave structures is the necessity of simultaneous handling of several objectives and the fact that expensive electromagnetic (EM) analysis is required for their reliable evaluation. Design of multi-band circuits where performance requirements are to be satisfied for several frequencies at the same time is even more difficult. In this work, a computationally efficient design of dual-band microstrip couplers is demonstrated by means of an adaptive response scaling (ARS) technique. ARS is a surrogate-assisted method that exploits a fast surrogate of the high-fidelity EM-simulation model of the coupler at hand constructed from its corrected equivalent circuit. ARS identifies nonlinear frequency and amplitude response scaling that accommodates the misalignment between the low- and high-fidelity models. Due to exploiting the knowledge embedded in the low-fidelity model ARS surrogate exhibits excellent generalisation capability. It is demonstrated here by optimisation of a dual-band microstrip coupler with enhanced bandwidth, working at 1 GHz and 2 GHz frequencies. The optimised design has been obtained at the cost of just a few high-fidelity EM simulations of the structure. Numerical comparisons indicate superiority of ARS over competitive surrogate-assisted techniques. Experimental validation is also provided.