CHARACTERIZATION

One way to assess filter performance is measuring the passband, off-resonance isolation and Q-factor versus frequency. Three of these measurements, which were performed using a Keysight Technologies E5071C network analyzer, are shown in Figure 5. Keeping the passband bandwidth constant at approximately 40 MHz, the Q-factor increases as the frequency increases, from 59 at 2.23 GHz to 75 at 3.3 GHz and 111 at 4.4 GHz. At 6 GHz, the Q reaches 160, confirming the performance of the YIG-based design is better than other tunable filter technologies. This characteristic of increasing Q with frequency is clearly seen in Figure 6, which plots the measured Q-factor versus frequency and adds the effect of temperature, from -40°C to +85°C. The data shows Q-factor is stable over temperature.

Figure 6

Figure 6 Measured Q-factor vs. center frequency and temperature.

Figure 7

Figure 7 Tunable filter bandwidth vs. center frequency and temperature.

Additional temperature characterization assessing the sensitivity of the 40 MHz filter bandwidth versus frequency is shown in Figure 7. The passband bandwidth is stable across temperature and frequency. Figure 8 plots the offset of the center frequency from the intended frequency as a function of the center frequency and temperature. The goal is 0 MHz offset, which is achieved over most of the graph, although the offset increases as the temperature increases.

Figure 8

Figure 8 Center frequency tuning offset vs. center frequency and temperature.

Figure 9

Figure 9 Surface-mount tunable YIG filter demonstrator.


A surface-mount demonstrator of the Next Generation YIG-tuned filter has been developed to enable customer evaluation (see Figure 9). Table 1 summarizes its performance.

Table 1

SUMMARY

Continued demand for increased bandwidth shows no signs of slowing, nor the demand for smaller, lower power and higher performance filters, particularly at S- and C-Band. Next-generation YIG technology has the potential to meet this need and is ready for production. VIDA Products is working with early adopters to develop custom designs for their programs.

This new YIG-tuned filter technology achieves the long-recognized performance of YIG resonators without the drawback of their large size, high power consumption and high cost. By integrating the YIG spheres into a single resonant cavity and reducing the complexity, size and power of the magnet, this new design approach can achieve up to a 10x reduction in size and power consumption compared to traditional YIG designs. VIDA’s technology roadmap envisions moving from today’s YIG spheres to a nano-film technology that could yield another 10x reduction in size and power.

Considering the performance capabilities and benefits, YIG-based filters warrant consideration.12 This new generation of YIG technology offers performance with reduced size and is more economical than historic YIG design. It provides a solution for systems that need to increase performance while reducing footprint and decreasing cost.

References

  1. “Our Most Valuable Natural Resource – the Frequency Spectrum,” Lumenradio, October 2017, Web: https://lumenradio.com/our-most-valuable-natural-resource.
  2. T. Kidd, “Radio Frequency Congestion,” CHIPS, US Navy, October 2009, Web: www.doncio.navy.mil/chips/ArticleDetails.aspx?ID=2616.
  3. “Congestion in the Radio Frequency Spectrum,” Tait Radio, Tait Communications, September 2012, Web: https://blog.taitradio.com/2012/09/06/congestion-in-the-radio-frequency-spectrum.
  4. J. R. Hoehn, et al. “Overview of Department of Defense Use of the Electromagnetic Spectrum,” CRS Reports, October 2020, Updated August 2021, Web: https://sgp.fas.org/crs/natsec/R46564.pdf.
  5. “Auction 107: 3.7 GHz Service,” Federal Communications Commission, December 2020, Web: www.fcc.gov/auction/107/factsheet.
  6. J. Nielsen, “Nielsen’s Law of Internet Bandwidth,” Nielsen Norman Group, April 1998, Updated September 2019, Web: www.nngroup.com/articles/law-of-bandwidth.
  7. R. K. Ackerman, “Defense Experts Plan More Agile Spectrum Use,” SIGNAL Magazine, December 2020, Web: www.afcea.org/content/defense-experts-plan-more-agile-spectrum-use.
  8. Analog Devices, Inc. “Three Digitally-Controlled Tunable Filters for VHF to 18 GHz Applications,” Microwave Journal, Vol. 64, No. 1, January 2021, pp. 92-96, Web: www.microwavejournal.com/articles/35248-three-digitally-controlled-tunable-filters-for-vhf-to-18-ghz-applications.
  9. “Q Factor,” Wikipedia, Wikimedia Foundation, October 2021, Web: https://en.wikipedia.org/wiki/Q_factor.
  10. “3.45 GHz to 6.25 GHz, Tunable Band-Pass Filter,” Analog Devices, September 2018, Web: www.analog.com/media/en/technical-documentation/data-sheets/HMC892ALP5E.pdf.
  11. Al-Yasir, I.A. Yasir, et al. “A Varactor-Based Very Compact Tunable Filter with Wide Tuning Range for 4G and Sub-6 GHz 5G Communications,” Sensors, Vol. 20, No. 16: 4538, August 2020, pp. 12, Web: doi.org/10.3390/s20164538.
  12. “Superhet Radio RF Amplifier & Tuning,” Electronics Notes, Web: www.electronics-notes.com/articles/radio/superheterodyne-receiver/superhet-rf-amplifier-tuning.php.