Next Generation Broadband Preselector
The design goal in this system was to update and modernize the legacy preselector systems used by NTIA for monitoring and measuring possible emission violating from 2-20[GHz] for one preselector, and 18-50[GHz] for another mmWave optimized preselector. Initially the redesign was contained to the PCB redesign for a modern and modular control system to operate multiple relays, amplifiers, and RF switches that automate measurement operations in communication with a local PC and Signal Analyzer. For the RF, the bandwidth being limited to 26.5-40[GHz].
Upon independent noise figure analysis of the cascaded system, along with component capability and availability studies, I redesigned the layout and proposed the purchase of components that would expand capability to 18-50[GHz] in a single chained system. Additionally proposing an optimized integration of both preselectors into a consolidated modern and unified 1[MHz]-50[GHz] Preselector device using switched channels for specific bandwidths while optimizing such that overlaps on each bandwidth’s start and end points gave continuity. Optimizing noise, filtering, and low noise amplification to improve preselector specifications. Currently the first of these two designs is being implemented, using a manually selectable wr28 or 2.4mm bulkhead that fed the rest of the system. Simulated noise figures resting around 13-14dB at lower frequencies, and 14-16dB at the higher mmWave levels. As of writing this we are at the purchase and assembly stage, I also anticipate tuning lengths for optimizations, but the overall design and future revision prospects are complete. A custom ordered PCB utilizes an ethernet-controlled raspberry pi pico to automate the progressive bandwidth scans as well as initial protections and calibration that a noise source and internal attenuator perform to protect the sensitive systems.
Eventually with funding the program hopes to expand to 75[GHz] and beyond which will require a near complete rework to facilitate it. As well as custom RF circuitry if they allow me.
