Category Archives: HFWorks

Designing and simulating a Multi-Coupled Resonator Microwave Diplexer with High Isolation

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By Nadia Gary, Application Engineer, EMWorks.

Diplexer is a device used for either splitting a frequency band into two sub-bands or for combining two sub-bands into one wide band. It is popularly used in satellite communication systems to combine both the Tx and the Rx antennas on space craft. Microwave diplexer is commonly used in the Radio Frequency (RF) front end of cellular radio base stations to separate the Tx and the Rx channels.

Conventionally, microwave diplexers are achieved by connecting two separately designed filters together via an external energy distribution device. This connecting device could be a T-junction,  a Y-junction, a circulator, a manifold  or a common resonator. In this article, we present without an external junction a microwave diplexer [1], and replacing it with resonators which provide resonant poles in the diplexer response.

Here is a design flow and a simulation of a 10-pole (10th order) diplexer that has been successfully designed and simulated. The diplexer is composed of 2 poles from the dual-band filter, 4 poles from the Tx bandpass filter, and the remaining 4 poles from the Rx bandpass filter. The design was implemented using asynchronously tuned microstrip square open-loop resonators. Figure 1 shows the design of the diplexer using SolidWorks.

Figure1- Geometry of Multi-Coupled Resonator Microwave Diplexer

Fig. 2 shows the diplexer layout which consists of a multi-coupled resonator designed using SolidWorks. The diplexer fed by a 50 microstrip-line (width WF = 1.1 mm) for each port, the center frequency is 1.84 GHz, The RT/Duroid 6010LM substrate with a dielectric constant of 10.8, a loss tangent of 0.0023, and a substrate thickness of 1.27 mm was used for the simulation. The geometrical parameters of the multi coupled resonator diplexer (S1, S2, S3, S4, S5, S6, S7, S8, S9, t1 and t2) are defined in a file and they will be imported to SolidWorks as equations in order to facilitate and accelerate the workflow.Diplexer layout and fabricated model

Figure2 – Diplexer layout and fabricated model [1]

The table below summriazes the diffrent dimensions (global variables) to be imported into SolidWorks.

Dimension Value(mm)
S1 1.5
S2 2
S3 2
S4 1.6
S5 0.9
S6 1.65
S7 1.95
S8 2
S9 1.45
t1 1.45
t2 1.35

Table1 – summarizes the list of dimensions to be imported into SolidWorks 

The diplexer circuit model was simulated using HFWorks S-Parameters analysis. Figure 3, depicts the distribution of the electric field and figure 4 shows the simulated results S-parameters  of the geometry of Multi-Coupled Resonator Microwave Diplexer.

Distribution of the electric field at 1.9GHz

Figure3 – Distribution of the electric field at 1.9GHz

Simulation responses of the diplexer circuit model with HFWorks

Figure4 – Simulation responses of the diplexer circuit model with HFWorks

 Measured and simulated (with ADS) results of the diplexer circuit model

Figure5 – Measured and simulated (with ADS) results of the diplexer circuit model

The measured results and the EM loss simulation results with HFWorks are presented, in Fig.4 and indicated that the isolation between the Tx and Rx bands is about 40 dB. The graphs clearly show a good agreement between the simulation and measurement.

REFERENCES

[1] Augustine O. Nwajana, Kenneth S. K. Yeo, ” Multi-Coupled Resonator Microwave Diplexer with High Isolation”, 2016 European Microwave Conference, pp. 1167-1170, 4–6 Oct 2016, London, UK.

Wideband bandpass filter – Designed and analyzed using SolidWorks and HFWorks

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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.

Locking your study in EMS and HFWorks

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To protect your work from accidental changes, we recommend that use the Study Locking feature in both EMS and HFWorks. A locked study may be viewed but cannot be edited or changed. Of course, you can always unlock the study if you need to make changes.  To lock your study simply right-click on the study name and select Lock.  To unlock select Unlock.

 

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

RF & Microwave devices in HFWorks?

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All RF & Microwave devices can readily be designed in HFWorks. Below is just a sample list of devices and applications classified by areas:

RF& Microwave
• Antennas
• Connectors
• Filters
• Resonators
• Couplers
• Frequency-selective surfaces
• Band-gap (EBG) structures and meta-materials
• RF coils for MRI

EDA/Electronics
• Signal integrity
• Power integrity
• PCBs and IC Packages
• Chip-Package-Board systems

EMI/EMC
• All EMI/EMC structures
• Simultaneous switch noise (SSN)
• Simultaneous switching output (SSO)
• EM field exposure

Symmetry Boundary Conditions in HFWorks

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HFWorks is SolidWorks-embedded for high frequency applications. High frequency problems tend to be quite large because they are inversely proportional to the wavelength. Therefore, it is essential to take advantage of symmetry, when it exists, and apply the appropriate boundary condition. Several HFWorks users have asked for a clarification about this issue. There are two and only two types of symmetry B.C.:

Perfect magnetic conductor symmetry: applicable when the electric field is purely tangential, i.e. magnetic field is purely normal, on the plane of symmetry.

Perfect electric conductor symmetry: applicable when the electric field is purely normal, i.e. magnetic field is purely tangential, on the plane of symmetry.

Below is an illustration on a rectangular waveguide:

symmetry

Treating very thin conductors in HFWorks

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Today’s tip is about thin conductors in HFWorks

High frequency devices usually involve very thin conductor such as the printed traces in PCB and IC circuits. Actually even if they are not geometrically very thin, they are usually electrically so because at high frequencies, the wavelength is very small. Such thin conductors are difficult to mesh and could lead to a very large number of mesh elements. Fortunately, SolidWorks has a neat feature called split surfaces which consist of splitting a surface to one or more sub-surfaces. Hence, we recommend to not represent the thin conductors with any part or body. Simply split the upper surface of the substrate and apply the corresponding boundary condition just on the metallic split sub-surfaces. This trick minimizes the number of mesh elements considerably and gives accurate results.