Microwave Circuits

Cavity Resonator Filter Modeling Tutorial

This application note demonstrates step-by-step modeling goide of six-cavity filters in WIPL-D Pro CAD. Each cylindrical cavity includes individual tuning screws, with separate screws for inter-cavity coupling adjustment. This document explains modeling using built-in primitives (cylinders, cuboids), transformations (rotate, translate, copy), and complex shapes via sweep. Boolean operations like unite, subtract, imprint, and simplify assemble the blocks into a fully parameterized model ready for tuning or optimization. Basic WIPL-D Pro CAD principles are outlined, with tips for external project modifications via Notepad or MATLAB. The final step adds built-in ports, producing a simulation-ready design suitable for efficient EM analysis and overall efficiency.

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Quadrature Hybrid Coupler Miniaturization

This application note demonstrates compact quadrilateral (branch-line) hybrid directional coupler design using WIPL-D Pro CAD and fast full-wave 3D EM simulation. Built-in primitives and automatic quadrilateral meshing optimized for WIPL-D HOBF enable rapid modeling. Microstrip couplers are simulated in seconds per frequency. Miniaturization halves the size, though detailed artificial transmission lines increase EM complexity; WIPL-D keeps simulation efficient. The model includes losses, metallization thickness, substrate and ground dimensions, and feed positions. Results provide return loss, output power division, input port isolation, and output port phases, ensuring accurate and complete EM characterization for modern compact couplers.

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Divider in Substrate Integrated Waveguide Technology

This application shows WIPL-D’s capabilities for full-wave EM simulation of a substrate-integrated waveguide divider at 60 GHz. Using WIPL-D Pro CAD, the CAD model is imported and meshed; its symmetry allows simulating only a quarter, reducing resources and time. The moderate-size model with small details requires just 8,100 unknowns per MoM matrix, solved efficiently on an inexpensive multicore desktop using CPU-only computation.
WIPL-D’s parallelization ensures fast execution. Simulation results include full current distributions for all five ports, highlighting the efficiency and accuracy of WIPL-D for compact waveguide dividers in SIW technology, combining precision, low computational cost, and quick turnaround for advanced EM design.

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Round Rod Interdigital Filter Optimization Using WIPL-D

This application note presents a comprehensive overview of the system’s design, operating principles, and practical performance. It explains the motivation behind the architecture, outlines the key technical choices made during development, and details the methods used to verify functionality under realistic conditions. Special attention is given to component selection, layout considerations, calibration steps, and measurement procedures that influence overall accuracy and stability. By guiding the reader through each stage of the process — from initial concept to validated results — this document aims to provide a clear, reliable reference that supports effective implementation, troubleshooting, and future enhancements of the system.

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Linear Transistor Modeling Using Equivalent Circuits

This note shows accurate transistor characterization for amplifier design using WIPL-D Microwave, providing a complete environment for implementing lumped circuit equivalent transistor models that deliver reliable S-parameter data. A low-power packaged GaAs HEMT is modeled, with intrinsic and extrinsic elements partitioned and their physical basis briefly explained. The calculated S-parameters are highly accurate, enabling designers to overcome limitations of sparsely tabulated transistor data and determine optimal biasing points for specific applications. WIPL-D Microwave ensures the flexibility to implement schematics of any commonly used linear transistor model, supporting efficient and precise amplifier design workflows.

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Rectangular Waveguide Interdigital Filter

This application note describes the detailed simulation of a band-pass interdigital filter in rectangular waveguide technology, modeled in WIPL-D Pro CAD using the native editor and built-in primitives. A symmetry plane was carefully utilized to reduce structural complexity, and two waveguide ports served as feeders. The model was simulated from 5 GHz to 14 GHz at 26 frequency points, with convergence checks performed to ensure high accuracy. After the convergence study, filter dimensions were finely tuned to achieve S11 values below –20 dB in the passband (8.30–10.86 GHz). Simulations can be efficiently performed on any desktop or laptop, preferably with multiple CPU cores, with per-frequency simulation times measured in seconds overall.

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Multi-hole Waveguide Coupler

The multi-hole waveguide coupler, basically an extension of the single-hole coupler, is specifically designed to increase operational bandwidth. Its overall performance mainly depends on the size of the coupling holes and the distances between them, ensuring wave amplification in the through-direction and cancellation in the opposite direction. Standard X-band WR-90 waveguides (22.86 mm × 10.16 mm) are coupled through a series of rectangular holes arranged in a zig-zag pattern. Simulations use a relatively low number of frequency points thanks to powerful built-in interpolation, and hardware requirements are minimal—any standard desktop or laptop can typically perform the simulation in seconds due to the rather small number of unknowns.

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7-Port Divider

In this application note, a 7-port divider is simulated from 1.4 GHz to 1.6 GHz in microstrip technology, with a probe-fed SMA Tx port and six Rx microstrip ports. The model is created in WIPL-D Pro using parametrized geometry, defining symbols, nodes, and plates, which, while slightly slower than importing DXF or other files, produces an optimal mesh minimizing simulation time. Efficiency is further improved with Copy/Layer manipulation. Thanks to built-in interpolation, only a few frequency points are required. WIPL-D Pro treats the 7-port divider as electrically small, resulting in minimal unknowns and very fast simulation. Simulation is completed on a standard desktop in few seconds, demonstrating accuracy and computational efficiency.

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SPDT Shunt PIN Diode Switch

This application demonstrates the design and simulation of a single pole double throw (SPDT) switch using PIN diodes in WIPL-D Microwave Pro. The diodes are modeled with equivalent circuits for ON and OFF states, while other schematic elements, including microstrip and coaxial components. Simulations show accurate performance analysis of semiconductor-based switches over relevant frequency ranges.
WIPL-D Microwave integrates full-wave 3D EM solver, circuit modeling, and built-in optimization, enabling efficient evaluation of complex microwave designs. This approach reduces simulation time, minimizes unknowns, and allows execution on standard desktop or laptop PCs, making WIPL-D a versatile solution for advanced microwave engineering.

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Lowpass Filter Design

In this application note, three filter models are designed and analyzed using WIPL-D’s Filter Designer, a wizard-like GUI for automated design of lowpass, highpass, bandpass, and bandstop filters of Chebyshev or Butterworth type. A lowpass Chebyshev approximation is considered: first model is an LC ladder, second a transmission line, and third a microstrip filter. The microstrip model is also simulated in WIPL-D’s 3D EM solver using full-wave EM analysis. The operating band is 0.014–2.8 GHz, and due to efficient interpolation, only 11 frequency points suffice for EM simulation on a standard desktop or laptop. Simulation time for circuit models is negligible, while full-wave EM simulation takes only a few seconds per frequency point.

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Metallic Cover over Wilkinson Power Divider

The Wilkinson power divider is a compact microwave circuit designed to split input power evenly between two output ports. In this note, the divider is simulated in WIPL-D Pro at 25 GHz on an ultra-thin 0.005 mm substrate (εr = 3), yet model remains stable. Microstrip ports are implemented using two trapezoidal plates connected by a short wire with triple junctions, ensuring excellent matching, minimal reflections, and accurate excitation. Output isolation is provided through a lumped resistor. A metallic enclosure is added to evaluate realistic packaging effects, and its influence is compared to the open version. Simulated results show clean −3 dB splitting, strong isolation, low return loss, and only slight impact from the added cover, overall simulation accuracy.

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Microwave Circuits Design in WIPL-D Microwave

Simulation of complex microwave circuits is demanding, so circuit-level analysis is typically the best starting point since it delivers quick, reliable results by using predefined library components that compute far faster than full-wave EM analysis, even across wide bands. WIPL-D Microwave provides a fast, accurate, and user-oriented environment, compatible with other tools through Touchstone import and seamlessly connected with the WIPL-D EM solver, Optimizer, and Time Domain Solver. Demonstrated designs include a single-stub tuner in rectangular waveguide matched at 10 GHz, a diplexer operating at 2 GHz and 2.2 GHz, and a Chebyshev coaxial impedance transformer spanning 2 to 8.5 GHz, all simulated on any standard desktop or laptop.

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