Abstract:This work presents a novel planar branch-line coupler topology developed for dual-band operation using an E-shaped impedance transformer network to supplant the conventional microstrip line. Explicit closed-form design equations for dual-band operation are derived using the ABCD matrices. The studied coupler features a large dual-band frequency ratio with a compact size. A prototype coupler centered at 1 and 8 GHz is first presented and experimentally examined to demonstrate the large frequency ratio. Further,… Show more
“…The second example is a dual-band branch line coupler 56 shown in Fig. 9 , implemented on the RO4003 substrate ( ε r = 3.5, h = 0.51 mm, tan δ = 0.0027).…”
Section: Demonstration Examplesmentioning
confidence: 99%
“…The computational model is implemented in CST Microwave Studio and evaluated using its time domain solver (~ 150,000 mesh cells, simulation time about 2 min). Figure 9 Dual-band branch-line coupler 56 ; circuit topology; port marked with numbers in circles. …”
The employment of numerical optimization techniques for parameter tuning of microwave components has nowadays become a commonplace. In pursuit of reliability, it is most often carried out at the level of full-wave electromagnetic (EM) simulation models, incurring considerable computational expenses. In the case of miniaturized microstrip circuits, densely arranged layouts with strong cross-coupling effects make EM-driven tuning imperative to achieve the optimum performance. The process is even more challenging due to a typically large number of geometry parameters, and the lack of reasonable initial designs. The latter often encourages the use of global search procedures, which may be prohibitively expensive. In this paper, a novel automated framework for reliable optimization of miniaturized microwave components is proposed. Our methodology is based on design specification management, where the performance requirements imposed on the system are temporarily relaxed if the current design is unlikely to be improved (e.g., due to being away from the target operating frequency). The specifications are re-adjusted at each iteration of the algorithm, and eventually converge to their original values. Using two examples of compact microstrip couplers and a power divider, the presented technique is demonstrated to significantly improve the efficacy of local search routines under challenging design scenarios.
“…The second example is a dual-band branch line coupler 56 shown in Fig. 9 , implemented on the RO4003 substrate ( ε r = 3.5, h = 0.51 mm, tan δ = 0.0027).…”
Section: Demonstration Examplesmentioning
confidence: 99%
“…The computational model is implemented in CST Microwave Studio and evaluated using its time domain solver (~ 150,000 mesh cells, simulation time about 2 min). Figure 9 Dual-band branch-line coupler 56 ; circuit topology; port marked with numbers in circles. …”
The employment of numerical optimization techniques for parameter tuning of microwave components has nowadays become a commonplace. In pursuit of reliability, it is most often carried out at the level of full-wave electromagnetic (EM) simulation models, incurring considerable computational expenses. In the case of miniaturized microstrip circuits, densely arranged layouts with strong cross-coupling effects make EM-driven tuning imperative to achieve the optimum performance. The process is even more challenging due to a typically large number of geometry parameters, and the lack of reasonable initial designs. The latter often encourages the use of global search procedures, which may be prohibitively expensive. In this paper, a novel automated framework for reliable optimization of miniaturized microwave components is proposed. Our methodology is based on design specification management, where the performance requirements imposed on the system are temporarily relaxed if the current design is unlikely to be improved (e.g., due to being away from the target operating frequency). The specifications are re-adjusted at each iteration of the algorithm, and eventually converge to their original values. Using two examples of compact microstrip couplers and a power divider, the presented technique is demonstrated to significantly improve the efficacy of local search routines under challenging design scenarios.
“…The second verification case is a dual-band branch line coupler (BLC) [17] implemented on the RO4003 substrate (ε r = 3.5, h = 0.51) mm, tan (δ = 0.0027). The circuit geometry has been shown in Fig.…”
Section: B Case Ii: Dual-band Branch-line Couplermentioning
confidence: 99%
“…Perhaps the major reason is that traditionally used analytical or network-equivalent tools are no longer adequate when EM cross-couplings [5], substrate anisotropy [6], the effects of environmental components (connectors, housing, nearby devices) [7], or multi-physics phenomena [8], are to be taken into account. At the same time, the topological complexity of microwave circuits has been gradually increasing to meet the stringent performance requirements pertinent to emerging areas (5G communications [9], energy harvesting [10], wireless power transfer [11], space applications [12]), to enable miniaturization [13]- [15], or to implement additional functionalities (dual-band [16], [17] or multi-band operation [18], [19], tunability [20], unconventional phase characteristics [21], etc.). Topologically sophisticated circuits are described by a large number of design variables that need to be simultaneously tuned in pursuit of controlling multiple performance figures and constraints.…”
Section: Introductionmentioning
confidence: 99%
“…FIGURE 6. Dual-band branch-line coupler[17]: circuit topology; ports marked with numbers in circles.…”
Parameter adjustment through numerical optimization has become a commonplace of contemporary microwave engineering. Although circuit theory methods are ubiquitous in the development of microwave components, the initial designs obtained with such tools have to be further tuned to improve the system performance. This is particularly pertinent to miniaturized structures, where the cross-coupling effects cannot be adequately accounted for using equivalent networks. For the sake of reliability, design closure is normally performed using full-wave electromagnetic (EM) simulation models, which entails considerable computational expenses, often impractically excessive. Available mitigation techniques include acceleration of the conventional (e.g., gradient-based) routines using adjoint sensitivities or sparse sensitivity updates, surrogate-assisted and machine learning algorithms, the latter often combined with nature-inspired procedures. Another alternative is the employment of variable-fidelity simulations (e.g., space mapping, co-kriging), which is most often limited to two levels of accuracy (coarse/fine). This work discusses an EM model management approach coupled with trust-region gradient-based routine, which exploits problem-specific knowledge for continuous (multi-level) modification of the discretization density of the microwave structure at hand in the course of the optimization run. The optimization process is launched at the lowest discretization level, thereby allowing for low-cost exploitation of the knowledge about the device under study. Subsequently, based on the convergence indicators, the model fidelity is gradually increased to ensure reliability. The simulation fidelity selection is governed by the algorithm convergence indicators. Computational speedup (i.e., reduction in the number of EM simulations required by the optimization process to converge) is achieved by maintaining low resolution in the initial stages of the optimization run, whereas design quality is secured by eventually switching to the high-fidelity model when close to concluding the process. Numerical verification is carried out using two microstrip circuits, a dual-band power divider and a dual-band branch-line coupler, with the average savings of almost sixty percent when compared to single-fidelity optimization.
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