Quasonix Uses NI AWR Software and Modelithics to Achieve First-Pass Success With a Transmitter‘s Harmonic Filter Design
Quasonix designs, develops, and manufactures high performance aeronautical telemetry products and is a recognized industry leader for spectrally efficient modulations such as SOQPSK-TG and Multi-h (ARTM) CPM. The Quasonix line of advanced products includes multi-mode telemetry transmitters, multi-mode, multi-symbol trellis telemetry demodulators, complete multi-mode telemetry receivers, and rack-mount receiver analyzers. More and more, flight-test engineers are discovering that Quasonix products regularly outperform and outclass all other equipment on the market.
The Design Challenge
RF/microwave design computer-aided-engineering (CAE) tools have existed for many years and are used extensively by engineers to design linear and nonlinear RF/microwave circuits. These design efforts have been supported by linear S-parameter models for passives and compact nonlinear models and load-pull power device data for active devices, as provided by many component manufacturers.
At application frequencies above 1 GHz, the component parasitics such as series inductance in capacitors and shunt capacitance in inductors, as well as substrate-dependent component parasitics, significantly impact the actual circuit performance.
If these component parasitics are not included in the simulation, the accuracy of the simulation results will be significantly degraded. Consequently, extensive prototype board-level bench tuning and rework is typically required to achieve the desired results. Often a second or third board iteration (or spin) is needed to achieve acceptable performance. This is costly, not only in terms of board fabrication costs, but in engineering time, design productivity, lost calendar time, and missed time-to-market windows for new products.
The Quasonix product development team successfully designed a low-pass harmonic filter in a single pass using NI AWR Design Environment, specifically Microwave Office circuit design software, and Modelithics® Global Microwave Models™ included in the Modelithics CLR Library. Starting with ideal lumped element capacitors and inductors and including the interconnecting microstrip lines, the 2.2 to 2.4 GHz harmonic filter was designed for low S11 in the passband and high rejection at the second harmonic and above. The simulated response from Microwave Office shows insertion loss less than 0.05 dB, second harmonic rejection of 49 dB, and minimum 47 dB rejection up to 20 GHz.
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