Microstrip Combline Bandpass Filter

A successful simulation of microstrip combline bandpass filter is demonstrated in this application note. The software tool used for the simulation is WIPL-D Pro software, a full wave 3D EM Method-of-Moments (MoM) based solver.

Simulation of one of the classical printed structure, the microstrip combline bandpass filter, was performed in a reasonable time on cost-effective, moderate computer platform. The fabrication of the microstrip filter prototype can follow immediately after the optimization.  The optimal dimensions of the filter resonators, input and output lines and the gaps between the lines are all realizable in any standard microstrip technology. In addition, dielectric parameters have been chosen targeting a popular, commercial substrate.

The combline filter was simulated between 4.0 GHz and 5.5 GHz. The efficient Fitter, which is part of the WIPL-Graph window, enabled the wideband response of this microstrip filter to be accurately interpolated from model simulation at 37 discrete frequency points.

Described bandpass filter is very simple, but it still has very good properties as calculated S-parameters confirm the existence of a transmission zero above the passband which can be used to increase the selectivity at high passband edge.

According to all of the analysis details presented, it can be concluded that WIPL-D software is very suitable for the simulation of various microstrip filter structures for both, commercial and academic purposes.

In addition, the practical and educative value of this document should be recognized. This document with published dimensions of the structure can be used as a starting point for microstrip combline bandpass filter design and further research.

View PDF

Microwave Circuits Design in WIPL-D Microwave

Simulation of complex microwave circuits presents a challenge for modern computational software. Using circuit level analysis is recommended option for the starting calculations in order to get results quickly. In circuit solvers, all circuit elements are modeled by predefined library components whose calculations are performed faster than calculations in full-wave EM analysis, even over a wide frequency range, practically on-the-fly.

WIPL-D Microwave is fast, accurate and easy-to-use software tool, what is proofed by several simulation examples. WIPL-D Microwave is compatible with many other software tools because of supported Touchstone file import. It is integrated with WIPL-D EM solver, WIPL-D Optimizer and WIPL-D Time Domain Solver.

The examples of circuit designs include single-stub tuner with rectangular waveguides (matched at 10 GHz), Diplexer operating at 2 GHz and 2.2 GHz, and Chebyshev impedance transformer in coaxial technology from 2 GHz up to 8.5 GHz. Computer required for these simulations is any standard desktop or laptop PC.

View PDF

Microstrip Bandpass Filters

This application note presents S-parameters obtained with effective usage of WIPL-D Fitter, number of unknowns, computer memory required and simulation time per frequency obtained after simulation of two passive, microstrip, band pass filters. The first simulated filter is interdigital, while the second one is filter with coupled resonators.

The software tool used for simulations is WIPL-D Pro, a full wave 3D EM Method-of-Moments based solver. Interdigital BPF was simulated from 1900 MHz to 2600 MHz, while coupled resonator filter was simulated from 2000 MHz to 2700 MHz. Both simulations were performed in 9 frequency points. The S11-parameter curve is very smooth, owing WIPL-D Fitter efficient interpolation of the frequency response.

Simulations show extremely low number of unknowns and can be run at any desktop or laptop PC, with simulation times measured in seconds.

View PDF

Six-Port as Wireless Communication Receiver

The analysis and simulation of a six-port receiver for 24 GHz QPSK signal usign WIPL-D Microwave design environment has been demonstrated. The set of simulation tools available within the program allows not only for the accurate and reliable design of the individual components comprising a receiver system, but for detailed analysis of the system itself. Example of studying an impact of imperfections of branch-line hybrids to receiver performance has been presented.

Additional simulations of the receiver system are possible. The simulations should address impact of phase imbalance larger then considered 1° to receiver performance. Voltages at ports 1 and 2, both been set to 1 V for the demonstration, can be set to more realistic values. Measured voltages can be multiplied by a coefficient to take into account real conversion characteristic of the detector. Knowing sensitivity threshold of DSPU, minimum received signal level can then be determined. Simulation blocks of branch line and Wilkinson combiner circuits can be replaced with the blocks of S parameters measured on fabricated samples to explore signal constellations with real-world circuits. All these simulations can be carried out using WIPL-D Microwave.

View PDF