Category Archives: Scattering parameters

Wideband bandpass filter – Designed and analyzed using SolidWorks and HFWorks

By

Nadya Gary, Application Engineer, ElectroMagneticWorks Inc.

HFWorks for SOLIDWORKS helps designers to size their passive RF and Microwave components to ensure reliability and optimal performance. HFWorks is seamlessly integrated inside SOLIDWORKS, allowing RF and microwave designers to run simulations right inside SolidWorks environment, without the need for re-importing data with each design iteration.

In this blog post, we will see how HFWorks can be used to study a printed bandpass filter (BPF) centered at a frequency of 4GHz. The objectives of the simulation are 1) Finding the S-parameters for the filter and 2) Electric field distribution inside the filter

What is a bandpass filter and what are its applications?

A bandpass filter in general is an electronic device that allows signals between two specific frequencies to pass but doesn’t allow any other frequencies. Think of it as a gate keeper in a high security building where only people with an entry passcode can enter.  These kinds of filters are widely used in wireless transmitters and receivers and it serves the function of a gate keeper. It limits the passage of output signal to the band accepted for transmission. So if a device is authorized to transmit say between 2 and 5 GHz, it will only allow signals within this frequency to be transmitted and all other signals will not be allowed. On the other hand if you take a receiver, it will receive all kinds of signals with various frequencies. A bandpass filter will ensure that signals within a selected range of frequency be heard or decoded. So all unwanted frequencies will be blocked. A wideband bandpass filter has a wider bandwidth and hence its name. The figure below shows a design of a wideband bandpass filter used in a wireless receiving device. It is expected to operate between 2 and 6 GHz frequency.

real model

Figure 1 – Wideband Bandpass Filter

Simulation results

The scattering parameters (also called as s-parameters) are very important set of parameters that is used to characterize or describe RF and microwave devices. Electronics engineers would like to get the s-parameter matrix for their design so that they can use this information to build complex circuits using their passive components. HFWorks can automatically compute and output the s-parameter matrix. Figure 2 shows the s-parameters calculated by HFWorks for the wideband bandpass filter. In addition to the s-parameters other results like Impedance matrix, VSWR are also computer by HFWorks.

results table1

Figure 2 – HFWorks gives all engineering details including s-parameters in a Result Table

HFWorks is a 3D field simulation software and users can visualize results like electric field, magnetic field etc in 3D. For example users can see the Electric field distribution inside their filter (as shown in Figure 3). This 3D plot helps engineers to identify areas in the model where the Electric field strength are high. They can also create section plots to look at the electric field results inside their designs.

E-Plot_Final

Figure 3 – Electric field distribution inside the filter

HFWorks in action

Watch a quick video showing how HFWorks allows electronic designers to analyze their passive RF and Microwave component designs seamlessly inside SolidWorks.


Learn more about HFWorks

HFWorks is the first and only Gold Certified software for SOLIDWORKS which helps SOLIDWORKS users study their passive RF and microwave component designs seamlessly inside SolidWorks. It can utilize the geometry created using SOLIDWORKS directly for simulation thus obviating the need to do any geometry transfer. Its user interface emulates the SOLIDWORKS interface and so there is no learning curve associated with HFWorks for SOLIDWORKS users. Please feel free to contact us about trial, benchmark and pricing for HFWorks and see how it helps you design better products.

Get a Benchmark or a trial

Get an analysis of your design with an HFWorks benchmark. We can test your SOLIDWORKS assembly for a variety of different applications including: antennas, connectors and transitions, Filters, passive components, resonators, transmission lines and much more.

Output of HFWorks/Antennas module?

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The Antennas module outputs the following results for each study at each frequency:• All antenna parameters including gain, directivity, efficiency, axial ratio, input impedance, etc
• Far field parameters including radiation patterns
• Generalized S-parameters matrix
• Re-normalized S-parameters matrix
• Unique impedance matrix
• Unique admittance matrix
• TDR
• VSWR
• Propagation parameters at each port
• Impedances at each port
• Electric near field distribution
• Magnetic near field distribution

HFWorks/S-parameters Analysis?

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Scattering parameters or S-parameters (the elements of a scattering matrix or S-matrix) describe the electrical behaviours of linear electrical networks when undergoing various steady state stimuli by electrical signals. Although applicable at any frequency, S-parameters are mostly used for networks operating at radio frequency and microwave frequencies where signal power and energy considerations are more easily quantified than currents and voltages. S-parameters change with the frequency are readily represented in matrix form and obey the rules of matrix algebra.The HFWorks/S-parameters analysis belongs to the high frequency electromagnetic, or the full wave, regime, i.e. Maxwell’s displacement current that couples the electric and magnetic fields is significant and thus taken into consideration. The vector wave equation, i.e. combination of the full Maxwell’s equations, is solved using vector finite element to obtain the S-parameters and the electric/magnetic fields and related design parameters. It has many practical applications, including:

• Connectors
• Filters
• Couplers
• Attenuators
• Terminators
• Baluns
• Integrated Circuit
• Waveguides
• Power dividers
• Multiplexers
• Power combiners
• Transitions