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User Focus: Enhancing Productivity for RF/Microwave Design

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by Sherry Hess, VP of Marketing – AWR Group, NI

Electronic design automation (EDA) tools help engineers bring their high-tech products to market.  And in this day and age, as our infatuation with all things wireless continues to grow, so too must EDA solutions.  With this principle in mind, NI AWR Design Environment™ software has continued to evolve with each new release to not only keep pace with the state-of-the art in microwave/RF design but also to ensure the continual enhancement of productivity for its users—the MMIC, RF PCB, module, communication systems or radar systems designer.

From the very first release of AWR software (acquired by NI in 2011), a novel Windows-only use model coupled with a modern user interface and a wow-invoking  real-time tuning bar put AWR software on the map and entrenched its Microwave Office software in the market as the easy-to-use and easy-to-learn tool for high-frequency circuit design.

Fast forward to now — nearly two decades later — and the latest release of NI AWR Design Environment, V12, is no exception.  This latest release offers numerous new features and usability enhancements that support our traditional emphasis on our users and the tools they need to do their jobs better (higher performing designs, faster throughput, and more).  Highlights of this release include new technologies in critical customer areas for amplifier, antenna, and radar design.

Figure 1: The designer can select the appropriate load-pull data graphically
Figure 1: The designer can select the appropriate load-pull data graphically

Amplifier Design

Load-pull simulation has been a valuable tool for the design of amplifiers for more than a decade now. However, recent advances in data file formats by load pull measurement system vendors such as Maury Microwave and Focus Microwaves have significantly expanded the usefulness of load-pull characterization. These new file formats support a sweep of an independent variable such as input power, DC bias, or temperature, in addition to the swept source or load impedances. The ability to use this newer data within load-pull simulation to determine device characteristic impedances at harmonic frequencies greatly simplifies and speeds the design process. V12 allows the user to control the new load-pull file capabilities in an intuitive manner by adding important load-pull measurements and graphing control features. For example, in Figure 1, the designer can immediately see the various input powers used in the load-pull measurements. By simply moving the marker, all measurements and graphs are updated using the appropriate load-pull data.

Figure 2 shows an example of the new measurement capabilities. The red circle is showing acceptable loads to give the requested power-added efficiency (PAE) and output power. As the input power is changed, as illustrated in Figure 1, the curves and measurements automatically update, as shown in Figure 2.

Figure 2: An example of the new load-pull measurement capabilities. The red curve shows acceptable load ranges for a given power efficiency and output power
Figure 2: An example of the new load-pull measurement capabilities. The red curve shows acceptable load ranges for a given power efficiency and output power

In addition to the enhancements to load-pull simulations, stability analysis has been expanded within V12 to now include a connection to the AMCAD Engineering STAN tool. Stability can be difficult to predict in multi-stage amplifiers, which are commonly used in today’s designs. STAN allows the designer to probe internal parts of the circuit for potential stability violations. Potentially disastrous oscillations can thereby be avoided without sacrificing performance.

 Antenna Design

Antennas are a critical component of wireless communications systems. Most antennas have multiple input points, whereby the beam pattern can be controlled by proper excitation of the various inputs. Therefore, it is important to be able to predict the effect the driving circuitry has on the antenna pattern. At the same time, the load the antenna presents to the driving circuit changes as the beam changes. The antenna and circuit are coupled.

V12 has an important new capability to simulate this interaction: in-situ antenna analysis. The left image in Figure 3 shows an example of a 4 X 4 patch array, which is being scanned by changing the phase and amplitude of the input power to the various patches. By tuning the values of the phase and amplitude to the elements, the beam can be scanned. The right image in Figure 3 shows the top level of the feed network attached to the S-parameter simulation results from the EM simulation.

Figure 4 shows the 3D antenna pattern. As the tuner is moved, thereby changing the input power to each element, the beam scans. Optimization is also possible, as anything that can be tuned in Microwave Office can also be optimized. For example, the level of the side lobes of the antenna can be optimized for certain feed network characteristics.

Finally, it should be noted that the antenna patterns can now be brought into Visual System Simulator™, otherwise known as VSS, as the actual pattern to use in propagation models in communication systems. The system designer has a more accurate prediction for final system performance.

Figure 3: A 4 x 4 patch array in AXIEM EM simulator. The right figure shows the feed network.
Figure 3: A 4 x 4 patch array in AXIEM EM simulator. The right figure shows the feed network.

Radar Design

V12 advances the radar design capabilities in VSS. An improved phased array model supports the simulation of large arrays with a large variety of feed options and geometry configurations. The entire RF chain of the system can be constructed, including amplifiers, mixers, and filters. When the phased array model is inserted into the transmit/receive chain, the entire system can be optimized for optimum performance, as well as performance degradation due to antenna imperfections.

Integrated Third-Party Solutions

As an extension of our goal to develop features and functionalities to improve user productivity, we have also taken a broader view that our user base often needs specialized best-in-class tools for particular design challenges. Back in 2003, the EM socket concept was introduced into AWR software (now NI AWR Design Environment). This unique software feature enabled our users to readily and easily integrate third-party EM point tools (planar and full 3D) into the Microwave Office circuit design framework thereby giving designers the flexibility to use the tool of their choice for their design.

Our open mindset towards hybrid solutions has evolved and today is known as the AWR Connected program, which offers many specialized flows that provide a powerful and complete software-to-software and/or software-to-hardware design environment for printed circuit boards and test and measurement (T&M), as well as MMIC thermal and related synthesis technologies, to name a few.

Figure 4: The antenna pattern for the array. As the tuner is used, the input power and phase are changed to the elements and the beam scans
Figure 4: The antenna pattern for the array. As the tuner is used, the input power and phase are changed to the elements and the beam scans

Our latest AWR Connected solutions introduced in conjunction with the V12 release include:

AWR Connected for AMCAD – provides access to stability analysis (STAN) software from AMCAD Engineering. Stability can be difficult to achieve in microwave circuits, but with the link to STAN from Microwave Office, users are now able to locate and characterize the unwanted oscillations in components such as power amplifiers (PAs).

AWR Connected for DWT (Design Workshop Technologies) – provides an integrated DRC/LVS flow from within Microwave Office. The DWT DRC module is a full-featured DRC tool capable of complex layout rule checks that can be used as a sign-off tool that provides designers with an efficient tool for detecting network mismatches occurring in the physical layout of MMIC, PCB, and module designs.

Conclusion

NI AWR Design Environment has been developed out of the gate to enhance the user experience and maximize productivity. Each year we have introduced new features, functionalities, and third-party flows to support that philosophy, and our V12 release this year clearly continues the tradition of advancing and enhancing user productivity.

Learn more at ni.com/awr.

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