APPLICATION NOTE ANTENNA AND PROPAGATION SIMULATION WITH CST STUDIO SUITE AND WINPROP

Transcription

1 APPLICATION NOTE ANTENNA AND PROPAGATION SIMULATION WITH CST STUDIO SUITE AND WINPROP This Application Note describes how the CST STUDIO SUITE software package can be linked to WinProp to simulate the radiation characteristics of an antenna and its performance in a complex indoor or outdoor environment. The full-wave 3D solvers in CST STUDIO SUITE are used to the design and simulation of the antenna itself, while the wave propagation methods in WinProp use the calculated radiation pattern to calculate coverage in an electrically large environment. For the installation of radio systems, especially mobile, wave propagation models are necessary to determine propagation characteristics for any arbitrary configuration. The predictions are required for a proper coverage planning, the determination of multipath effects as well as for interference and cell calculations, which are the basis for the high-level network planning process. In a cellular network this planning process includes the prediction of the received power for each transmitting antenna among others. With the evolution of wireless broadband services in 3G, 4G, and 5G systems and in Wireless Local Area Networks (W-LAN), the wideband properties (e.g. delay spread, angular spread and impulse response) of the mobile radio channel become more and more important for system design and the site-specific planning process. The environments where these systems are installed range from small indoor office scenarios up to large urban, suburban or even rural areas. Hence wave propagation prediction methods are required to cover the full range of potential scenarios and special environments such as tunnels, stadiums or along highways. Besides the obstacles present in the corresponding environment (e.g. buildings in an urban scenario) the performance of the wireless transmission is also significantly impacted by

2 APPLICATION NOTE ANTENNA AND PROPAGATION SIMULATION WITH CST STUDIO SUITE AND WINPROP 2 the performance of the transmitting and receiving antennas. Therefore it is important to consider 3D antenna patterns describing the antenna characteristic in all directions and furthermore to combine these antenna patterns with the above-mentioned wave propagation models. Electromagnetic simulation can be used to design the antennas themselves, and also to compute the radiation characteristics in terms of a 3D antenna pattern. The resulting 3D antenna patterns describe antenna characteristic in the farfield and can then be superposed to the 3D radio channels computed with the wave propagation models. ANTENNA TEST MODELS CST STUDIO SUITE includes multiple solvers for a wide range of applications, including the time domain solver (general purpose, especially suitable for broadband antennas), the frequency domain solver (useful for narrowband and electrically small antennas) and the integral equation solver (best suited for wire antennas and reflector antennas). Any solver which is able to output farfield data can be used to characterize the antenna as installed and therefore used to link to WinProp. Two test cases have been selected in order to show the link between CST STUDIO SUITE and WinProp. This article focuses on two classic scenarios of interest an outdoor antenna mounted on a mast, and an indoor WLAN patch antenna array. The type of antenna selected for the outdoor analysis is the high gain stacked bicone omnidirectional antenna shown in Figure 1, operating at 3.5 GHz and mounted in the vicinity of a classical tower, having 4 vertical poles connected by bracing struts between them. The radiation pattern for this antenna is shown in Figure 2. For more information about this antenna and the simulation workflow please refer to the whitepaper Installed Performance of Communication Antenna Arrays. [1] The patch antenna array model used in the indoor scenario is assembled and simulated using the the SAM (System Assembly and Modeling) workflow (Figure 3), including the effect of the matching network, plastic housing and mechanical support without losing any parameterization of each single part. A farfield monitor at the frequency of interest (5.5 GHz) has been defined. z Outdoor scenario Theta Phi x Figure 1: Communication antenna array mounted on a tower. Figure 2: 3D farfield pattern of the antenna array in the vicinity of the tower.

3 APPLICATION NOTE ANTENNA AND PROPAGATION SIMULATION WITH CST STUDIO SUITE AND WINPROP 3 FARFIELD EXTRACTION The corresponding simulated result obtained with the Time Domain solver is shown in Figure 4. For more information about this antenna and the simulation workflow please refer to the CST application article Microstrip Patch Array Design. [2] Due to chosen alignment of the axes, the main lobe is pointing at the broadside and is aligned with the z-axis. Indoor scenario A VBA script can be executed inside CST STUDIO SUITE in order to export the data to the.apa (Antenna Pattern ASCII) format. The script is available under the Macro menu, in Results > Import and Export > Export Farfield to AWE WinProp. The.apa format requires that the axes be oriented such that the main lobe of the antenna is aligned with the x -Axis (Theta=90, Phi=0 ). For the WLAN antenna the axes must be arranged as shown in Figures 5 and 6, in order to be oriented according to the aforementioned rules. The.apa file can be retrieved in the Result folder of the.cst project. Figure 3: Schematic View (left) and 3D assembled model of the patch array (right). y Phi z Theta x Figure 4: 3D farfield 5.5. GHz. Figure 5: Macro settings used to export the farfield of the WLAN antenna.

4 APPLICATION NOTE ANTENNA AND PROPAGATION SIMULATION WITH CST STUDIO SUITE AND WINPROP 4 WINPROP FEATURES The WinProp software includes sophisticated wave propagation models for various scenarios (rural, urban, indoor, tunnel, stadium,...) and frequency bands as well as network planning modules for many air interfaces (incl. GSM, UMTS, LTE, CDMA, WiMAX, and WLAN). The WinProp software package includes the tools AMan, WallMan, and ProMan which lead users through the simulation workflow. AMan is the antenna manager and can be used to display the 3D antenna patterns generated in CST STUDIO SUITE and saved in the WinProp format. The WallMan software included in the WinProp package offers a convenient way to generate and edit corresponding 3D vector databases including various objects with individual material properties. Several import filters for standard CAD data (DXF, DWG,...) and GIS data (MapInfo, ArcView,...) are available. Furthermore bitmaps can be imported in WallMan in order to draw the walls manually based on the bitmap in the background. WallMan comes with a large material catalogue with the properties of typical construction materials. The ProMan software includes sophisticated wave propagation models (various ray-optical models including the accelerated IRT ray tracing and the unique dominant path model which combines high accuracy with short computation time) and considers the 3D antenna patterns for the computation of the coverage (path loss) for each individual transmitter. The network planning modules included in ProMan superpose the coverage plots for the individual antennas and determine the interference levels. Based on the cell assignment then maps of overall coverage and interference (SNIR), statistics such as maximum data rate and maxiumum throughput can be computed. z Theta x Phi y Figure 6: 3D farfield 5.5. GHz with changed axes orientation.

5 APPLICATION NOTE ANTENNA AND PROPAGATION SIMULATION WITH CST STUDIO SUITE AND WINPROP 5 Figure 7: Communication antenna array farfield pattern displayed in AMan. Figure 8: WLAN antenna pattern displayed in AMan.

6 APPLICATION NOTE ANTENNA AND PROPAGATION SIMULATION WITH CST STUDIO SUITE AND WINPROP 6 The Figures 9 and 10 show the indoor radio coverage computed in ProMan with a ray-optical wave propagation model considering the WLAN antenna shown in Figure 1 using the farfield source computed with CST STUDIO SUITE. The Figures 11 and 12 show the urban radio coverage in S band computed in ProMan with a ray-optical wave propagation model considering the outdoor omni-directional antenna on boom shown in Figure 1, using the farfield source computed with CST STUDIO SUITE. Figure 9: Indoor coverage (2D display) for WLAN antenna computed in ProMan with ray-optical model. Figure 10: Indoor coverage (3D display) for WLAN antenna computed in ProMan with ray-optical model.

7 APPLICATION NOTE ANTENNA AND PROPAGATION SIMULATION WITH CST STUDIO SUITE AND WINPROP 7 CONCLUSION REFERENCES This application note has demonstrated the combined work flow for simulating antennas and propagation using CST STUDIO SUITE and WinProp. By combining these tools, communication systems can be simulated in a realistic environment in an accurate, straightforward way. 1 Chris Walker, Spectrum Consulting, Installed Performance of Commu nication Antenna Arrays, 2 CST, Microstrip Patch Array Design, Figure 11: Urban coverage (2D display) for outdoor antenna computed in ProMan with ray-optical model. Figure 12: Urban coverage (3D display) for outdoor antenna computed in ProMan with ray-optical model.

8 APPLICATION NOTE ANTENNA AND PROPAGATION SIMULATION WITH CST STUDIO SUITE AND WINPROP 8 ABOUT AWE COMMUNICATIONS AWE Communications was founded in 1998 as a spin off from the Institute of Radio Frequency Technology at the University of Stuttgart. Since these early days, the main focus of AWE Communications has been the development of software tools for wave propagation and radio network planning. WinProp, the main software suite of AWE Communications, is a standard software in the world of wireless propagation and radio network planning. AWE Communications GmbH Otto-Lilienthal-Str. 36 D Böblingen mail@awe-communications.com During the last 16 years, AWE Communications has accompanied the evolution of wireless and cellular mobile communications including the migration from 2G via 3G to 4G cellular networks. Together with strategic partners and involved in multiple public funded projects, AWE Communications has developed different software tools for various applications in the world of wireless communications. AUTHORS Reiner Hoppe, AWE Davide Tallini, CST AG ABOUT CST Founded in 1992, CST offers the market s widest range of 3D electromagnetic field simulation tools through a global network of sales and support staff and representatives. CST develops CST STUDIO SUITE, a package of high-performance software for the simulation of electromagnetic fields in all frequency bands, and also sells and supports complementary third-party products. Its success is based on a combination of leading edge technology, a user-friendly interface and knowledgeable support staff. CST s customers are market leaders in industries as diverse as telecommunications, defense, automotive, electronics and healthcare. Today, the company enjoys a leading position in the high-frequency 3D EM simulation market and employs 280 sales, development, and support personnel around the world. CST STUDIO SUITE is the culmination of many years of research and development into the most accurate and efficient computational solutions for electromagnetic designs. From static to optical, and from the nanoscale to the electrically large, CST STUDIO SUITE includes tools for the design, simulation and optimization of a wide range of devices. Analysis is not limited to pure EM, but can also include thermal and mechanical effects and circuit simulation. CST STUDIO SUITE can offer considerable product to market advantages such as shorter development cycles, virtual prototyping before physical trials, and optimization instead of experimentation. Further information about CST is available on the web at Trademarks CST, CST STUDIO SUITE, CST MICROWAVE STUDIO, CST EM STUDIO, CST PARTICLE STUDIO, CST CABLE STUDIO, CST PCB STUDIO, CST MPHYSICS STUDIO, CST MICROSTRIPES, CST DESIGN STUDIO, CST BOARDCHECK, PERFECT BOUNDARY APPROXIMATION (PBA), and the CST logo are trademarks or registered trademarks of CST in North America, the European Union, and other countries. Other brands and their products are trademarks or registered trademarks of their respective holders and should be noted as such. CST STUDIO SUITE is a CST product. CST Computer Simulation Technology AG, Bad Nauheimer Str. 19, Darmstadt, Germany