Divider in Substrate Integrated Waveguide Technology

This application presents capabilities of WIPL-D software suite for full wave electromagnetic simulation of waveguide divider realized in substrate integrated waveguide technology, along with simulation results and requirements. WIPL-D is modern and extremely efficient Method of Moments full wave 3D EM simulator.

The divider in wave guide technology is moderate size model with certain smaller details, so WIPL-D advantages are pronounced in full extent. The simulation model has low number of mesh elements and low number of unknown coefficients needed to determine current distributions. The code executes rather quickly on inexpensive CPU platforms thanks to excellent parallelization capabilities. The simulation model of the waveguide divider originates from the provided CAD file, imported into WIPL-D Pro CAD. The model is symmetrical so only quarter of the model is simulated. This dramatically saves resources and simulation time. The device is designed for 60 GHz.

The simulation is carried out by using only CPU technology considering the fact that the model is not electrically large. The simulation requires only 8,100 unknown coefficients in MoM matrix, but it is carried out 4 times to generate results for all 5 ports (model symmetry). The total simulation time per frequency point is 39 sec on multicore desktop PC:

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Round Rod Interdigital Filter Optimization Using WIPL-D

This application note presents the results of round rode interdigital filters optimization using WIPL-D Pro, a full wave 3D electromagnetic simulation software empowered with Optimizer, a WIPL-D add-on tool.

Two filter responses have been considered, one with 180 MHz bandwidth and the other with 240 MHz bandwidth, both centered around 3.75 GHz. The lengths of the resonators, the gaps between the resonators and the height of the metallic box have been optimized using WIPL-D Optimizer. The optimization iteration takes only under 30 sec on any modern quad core laptop or desktop computer.

The illustrative examples of 5th order round rod interdigital filter optimization has been presented. The examples demonstrate that WIPL-D Pro can be successfully used to aid the real life design of a important filter structure. The basic strengths of the full 3D EM simulation program are high accuracy and extremely fast simulation which allows for quick optimization against various filter specifications.

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Linear Transistor Modeling Using Equivalent Circuits

The accurate transistor characterization is a starting point to carry out an amplifier design. Lumped circuit equivalent transistor models are compact and versatile means of providing reliable S parameter data. WIPL-D Microwave provides a complete environment to implement these models.

The modeling of a commercially available low power packaged GaAs HEMT has been illustrated. The partitioning of the transistor equivalent circuit to intrinsic and extrinsic elements has been presented and physical grounds behind each of the elements explained in brief. It has been shown that S parameters calculated using the model are highly accurate and can be utilized to overcome the limitation imposed with sparsely tabulated transistor data, e.g. to find the optimal biasing point for a desired application.

WIPL-D Microwave design environment provides required flexibility to implement a schematic of any commonly used linear transistor model.

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Rectangular Waveguide Interdigital Filter

This application note describes simulation of a band-pass, interdigital filter in rectangular waveguide technology. The filter was modeled using WIPL-D Pro CAD by using native editor and built-in primitives.

Symmetry plane has been utilized to reduce the complexity of the structure and two Waveguide Ports were used as feeders. The model was simulated from 5 GHz to 14 GHz in 26 frequency points. To ensure high accuracy, the convergence of the results has been checked. After the convergence study, dimensions of the filter were tuned to set values of s11 in the pass-band (8.30 GHz to 10.86 GHz) below -20 dB.

Computer used can be any desktop or laptop, desirably with higher number of CPU cores, with simulation time per frequency measured in
seconds.

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Matching Network Design for Power Amplifiers

The adequate modeling of matching networks is crucial for the success of power amplifier design. Due to a set of simulation tools included, WIPL-D Microwave provides a complete environment for accurate and efficient modeling and design of power amplifiers.

Example of a commercially available power transistor has been presented to explain the matching network topologies preferred for the power amplifier application and to demonstrate the outline of the complete design flow. The necessity to introduce electromagnetic analysis to accurately model typical power amplifier matching networks or otherwise face the significant inaccuracy due to the effects of coupled discontinuities has also been explained.

The design has been carried out for the microstrip substrate recommended by a manufacturer. If necessary, it can be easily adapted to any other substrate preferred providing that the substrate thickness conforms with the height of the transistor lead and the first transmission line element in the networks remains wider than the width of the transistor lead.

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Power Detector with Zero-Bias Schottky Diode

The design of a power detector can be easily accomplished if the right set of tools is available. WIPL-D Microwave is a one stop design environment providing a microwave circuit designer with several modeling options. The modeling using analytical elements can be smoothly expanded to EM analysis as an automated transfer of any schematic comprising elements with adequate layout representation to a 3D EM component is available whenever more accurate modeling is
required.

A choice between non-matched or matched power detectors is driven by the context of a particular application. For the case of a matched detector, the simplest matching network topology is preferred where detector sensitivity is a must. However, the return loss values obtained by a simple network may not be sufficient for some applications. If this is the case, a more complex matching network must be designed trading-off the sensitivity for favorable return loss values. To accurately account for all the effects occurring within the matching network, use of electromagnetic modeling is highly recommended.

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Multi-hole Waveguide Coupler

Multi-hole waveguide coupler is extension of single-hole coupler, designed to increase the operational bandwidth. The performance is based on size of the coupling holes and distance between them, since it is important to achieve wave amplification in the through-direction and cancellation in the opposite direction.

The waveguides used correspond to standard X-band WR-90, with dimensions of 22.86 mm by 10.16 mm. The waveguides are coupled through a series of rectangular cross-section holes arranged in a zig-zag order.

Simulation is performed at low number of frequency points due to powerful built-in interpolation. The hardware requirements are minimum, any standard desktop or laptop yields simulation time measured in seconds, owing to rather small number of unknowns.

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7-Port Divider

In this application, we simulate 7-port divider from 1.4 GHz to 1.6 GHz. This device is realized in microstrip technology, fed by probe with SMA connector at Tx port and the remaining 6 ports (Rx) are microstrip ports.

The model was made by using WIPL-D Pro as parametrized geometry (defining symbols, nodes, creating plates…). It is very simple process, but it takes a bit more time than the other possibilities (import of the DXF or any other geometry file, building the model in WIPL-D Pro CAD). The result is optimal mesh with minimum simulation time. The process is done more efficiently if the Copy/Layer manipulation is used.

A low number of frequency points is possible owing to built-in interpolation. In WIPL-D pro, even a 7-port divider is considered as electrically small structure. The number of unknowns and simulation time are minimum, so the simulation was carried out on regular desktop in just a couple of seconds.

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SPDT Shunt PIN Diode Switch

Design of various microwave circuits using semiconductor devices can be carried out utilizing WIPL-D Microwave. Many types of diodes, such as PIN and Schottky diodes, or transistors operating in a linear regime, can be simulated by inserting into a schematic a suitable equivalent circuit usually provided by a manufacturer. Other schematic elements from the libraries available, including ideal, microstrip, co-planar or coaxial elements, can be subsequently added to the schematic to complete the design of complex microwave circuits such as switches, detectors, amplifiers, oscillators etc.

The application note illustrates the PIN diode through the design of single pole double throw (SPDT) switch utilizing two PIN diodes. The diodes are represented in a form of an equivalent circuit.  Due to the operating principle of the switch, both ON and OFF equivalent circuits are used in the same circuit.

An illustrative example of a SPDT PIN diode switch simulation using WIPL-D Microwave demonstrates that besides main strengths in EM related problems, the WIPL-D suite provides a complete environment for design of complex microwave circuits including those using semiconductor devices.

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