Microwave Circuits

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.

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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.

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