NI's High-Frequency EDA Software Platform Enables Fast RF/Microwave Development Cycles at Linwave Technology
Linwave Technology (Linwave) is a United Kingdom-based supplier of high-technology solutions for a wide range of microwave and RF applications in the military, satellite communications, telecoms, and industrial markets. Linwave manufactures components using chip, wire, and surface-mount technologies (SMT) on laminate construction.
A typical Linwave product includes microstrip filters, matching networks, and power splitters and combiners. Linwave products range from ultra low-noise receivers (<1dB noise figure) to high-power transmitters (>500W), and span VHF to millimeter-wave frequencies.
The Design Challenge
A general design challenge we face at Linwave is to accurately model bond wires as they are vital to performance when designing high-frequency chip and wire devices. To ensure our designs and end product performance converge, we start every design with basic linear simulations to prove concept and as the design develops we add more detail. The final design will usually involve electromagnetic (EM) simulations and nonlinear modeling.
A specific design challenge we recently faced, however, involved an X-band predistortion linearizer operating at 7.9-8.4GHz. The design spec required that we produce a module that generates an AM-AM and AM-PM profile, which at a prescribed drive level cancels out the AM-AM and the AM-PM of a power amplifier (in this case a traveling-wave tube) and thereby extends its linear dynamic range. Of particular interest to us was also the ability to generate both positive and negative changes (Figure 1 and 2) in AM-PM using the exact same hardware.
For this linearizer design, the built-in Schottky diode model and AM-AM/AM-PM measurements made it possible to put together a simulation very quickly. Using a combination of variable attenuators and phase shifters in conjunction with the Microwave Office® tuning utility, a design that gave the required control of AM-AM and AM-PM was quickly realized. Moreover, when the real hardware was tested, the required response was obtained and this resulted in a significant improvement in intermodulation products.
AWR’s Microwave Office circuit design software has always been well known for its intuitive user interface. The logical way in which projects evolve within the design flow helps to make it an excellent productivity tool for Linwave’s design paradigm of starting with basic linear simulations and adding detail as the design develops. The supplied examples offer a good starting point for setting up a new simulation and the real-time variable tuner is a vital and impressive tool that has proved to be extremely useful for Linwave’s component designs.
As well as being fast and intuitive, Microwave Office has proved to be very accurate and has been successfully employed at Linwave to design a wide range of amplifiers, gain equalizers, filters, couplers etc. working to over 40GHz.
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