DAF27BZ02-DV025 — Wide Pass Bandwidth, High Selectivity, Continuously Tunable Notch Filters

Wideband receivers used in electronic warfare (EW), signals intelligence (SigInt), and electronic support measures (ESM) need to instantaneously capture broad swaths of spectrum to avoid missing frequency agile radio frequency (RF) signals. Wideband receivers, however, lack the dynamic range to capture wide bandwidths of spectrum containing both large interferers and weak signals of interest. Thus, multiple receivers are needed in these applications which results in large size and power consumption.

The objective of this topic is to develop miniature, low power, and high selectivity tunable notch filters capable of protecting wideband receivers from large interferers. The effort will target the largest interferers which are in L, S, C, and X bands with tunable notch filters, while allowing pass bandwidths spanning L through Ku bands. Each notch filter must be continuously tunable across a minimum of 3 of the 4 targeted bands (L, S, C, and X) while having a notch depth > 20 dB and a notch bandwidth < 1 % across all tuned frequencies. With a narrow notch bandwidth, each notch filter must be programmable and maintained with an accuracy of 50% of the notch bandwidth and should maintain this accuracy over temperature. The notch filters must be able to reject large interfering signals and therefore should be able to notch receive interference levels greater than 5 dBm. In the bandpass each filter must cover L-Ku band (1-18 GHz) while maintaining a low insertion loss and noise figure of less than 1.5 dB and low passband distortion with an IIP3 > +50 dBm. Each notch filter must be small, less than 3 cc, and should be connectable in series without interfering with one another to notch multiple frequencies in the same receive chain. Finally, the power consumption, including any tuning electronics, of each notch filter should be less than 100 mW. The required metrics are: Passband frequency range (GHz)1 – 18 Maximum passband insertion loss or noise figure (dB) ≤ 1.5 Passband IIP3 (dBm)≥ 50 Notch band tunable frequency range (GHz)1 – 12 Number of bands covered by a single, continuously tunable notch≥ 3 Minimum notch depth across all tuned notch states (dB)≥ 20 Maximum notch fractional bandwidth (%)≤ 1Size (cc)≤ 3 Power consumption (mW)≤ 100

This topic is intended for a technology proven ready to move directly into a Phase II program. A Phase I SBIR award will not be made. The offeror is required to provide details and documentation in the Direct to Phase II (D2P2) proposal which demonstrates accomplishments of a "Phase I-like" effort, including demonstrating the expertise needed to design and fabricate miniature, high selectivity tunable notch filters. The offeror should have demonstrated, in a laboratory environment (TRL3), a notch filter achieving a 20dB deep notch with a bandwidth less than 5% of the tuned frequency, a continuous tuning range of at least 3:1, and a passband insertion loss below 3 dB across a wide frequency range. Demonstration of zero static power tuning and a filter volume of approximately 1 cc is desired. The offeror should have demonstrated the capability of maintaining low passband distortion and high notch depth across all tuned states. The proposal should illustrate past success at the aforementioned performance levels with tunable notch filter technologies fitting the above descriptions

The desired outcome of this topic is to demonstrate miniature, low power, and high selectivity tunable notch filters capable of protecting wideband receivers from large interferers. The effort will deliver prototype notch filters continuously tunable across a minimum of 3 of the 4 targeted bands (L, S, C, and X) while having a notch depth > 20 dB and a notch bandwidth < 1 % across all tuned frequencies.

Phase III is accomplished when the DoW and/or commercial applications of this SBIR-funded R&D are developed using non-SBIR/STTR funds. The most direct military application is the integration of these miniature, continuously tunable notch filters into the RF front ends of wideband receivers used for electronic warfare (EW), signals intelligence (SigInt), and electronic support measures (ESM). By selectively rejecting large interferers and jammers in L, S, C, and X bands while preserving reception across the full L–Ku passband, the filters enable a single high-dynamic-range wideband receiver to replace multiple narrowband receivers, directly reducing platform size, weight, and power. Additional DAF and DoW transition opportunities include receiver protection in airborne and ground-based radar systems, jam-hardened wideband communications and SATCOM-on-the-move terminals, and reconfigurable RF front ends for software-defined radios, where the same look-through capability allows the system to respond to threat pulses without missing frequency-hopped waveforms. Potential commercial applications include interference mitigation for 5G systems operating adjacent to incumbent services (such as C-band interference into radio altimeters and co-channel interference in cellular receivers), test and measurement instrumentation, and spectrum-monitoring equipment, all markets where compact, low-power, high-selectivity tunable filtering is increasingly required as the spectrum becomes more congested. The expected Phase III effort would advance the technology from its Phase II exit point of TRL5 toward TRL7 and beyond through integration into a host receiver subsystem, environmental qualification to applicable military standards, and demonstration in a relevant operational environment. This effort would also include maturation of the manufacturing process to support production quantities, screening and reliability testing, and the establishment of a qualified supply chain. Transition planning anticipates partnership with a DoW prime contractor or system integrator as the host platform sponsor, with the small business supplying the notch filter as a component or subassembly. Known government activities required prior to fielding include security classification review, ITAR/export-control determination, and any platform-specific airworthiness or system certification associated with the selected transition host. Early engagement with DAF program offices, EW and SigInt system developers, and additional DoW customers during Phase II is recommended to identify a committed transition partner and to align the filter's form factor and interface with the targeted receiver architecture.