Nanoscale spin-wave frequency-selective limiter for 5G technology

TL;DR

This work addresses protecting high-frequency 5G links by developing nanoscale ferrite-based Frequency Selective Limiters (FSLs) that exploit spin-wave transmission in a 97 nm YIG film. Using 250 nm CPW transducers, the authors demonstrate DE and BV spin waves up to 25 GHz, revealing power-limiting behavior driven by four-mMagnon scattering and extracting $P_{\text{th}}$, $P_{\text{L}}$, IL, and BW across modes and transducer lengths. An analytical framework based on four-magnon interactions and a micromagnetic simulation pipeline validate the experimental findings, showing good agreement for insertion losses and power thresholds. The results indicate a promising path toward integrated 3-in-1 spin-wave devices (limiter, filter, delay) for compact, energy-efficient components in 5G high-band systems.

Abstract

Power limiters are essential devices in modern radio frequency (RF) communications systems to protect highly sensitive input channels from large incoming signals. Nowadays-used semiconductor limiters suffer from high electronic noise and switching delays when approaching the GHz range, which is crucial for the modern generation of 5G communication technologies aiming to operate at the EU 5G high band (24.25-27.5 GHz). The proposed solution is to use ferrite-based Frequency Selective Limiters (FSLs), which maintain their efficiency at high GHz frequencies, although they have only been studied at the macroscale so far. In this study, we demonstrate a proof of concept of nanoscale FSLs. The devices are based on spin-wave transmission affected by four-magnon scattering phenomena in a 97-nm-thin Yttrium Iron Garnet (YIG) film. Spin waves were excited and detected using coplanar waveguide (CPW) transducers of the smallest feature size of 250 nm. The FSLs are tested in the frequency range up to 25 GHz, and the key parameters are extracted (power threshold, power limiting level, insertion losses, bandwidth) for different spin-wave modes and transducer lengths. An analytical theory has been formulated to describe the fundamental physical processes, and a numerical model has been developed to quantitatively describe the insertion losses and power characteristics of the FSLs. Additionally, the perspective of the spin-wave devices is discussed, including the possibility of simultaneously integrating three devices into one: a frequency-selective limiter, an RF filter, and a delay line, allowing for more efficient use of space and energy.

Figures (7)

• Figure 1: (a) (left) Schematic illustration of spin-wave (SW) power transmission for increasing input powers from left to right. The SW signal (light blue) and electromagnetic leakage (dark blue) are indicated for the first plot. The SW signal maximum is highlighted in green. (right) Power limiting characteristics extracted from the SW signal maxima at different input powers. The power threshold $P_{\mathrm{th}}$ and power limiting level $P_{\mathrm{L}}$ are indicated. The multi-magnon scattering, which takes place above the power threshold, is depicted in the orange box. (b) Schema of the spin wave and electromagnetic leakage transmission between the transducers placed on the YIG film.
• Figure 2: Fabricated structures and experimental setup. (a) SEM image of fabricated $10\,\upmu\mathrm{m}$ long CPW transducers of a center-to-center distance of $3\,\upmu\mathrm{m}$ on $97\,\mathrm{nm}$ thin YIG film. The width of the signal (S) and ground (G) conductors is $250\,\mathrm{nm}$, and the spacing between the conductors is $750\,\mathrm{nm}$. (b) Image from the optical microscope of the whole structure together with the curved transducer pads needed for contacting the picoprobes. (c) CPW transducers are connected via picoprobes and coaxial cables to VNA.
• Figure 3: Measured spin-wave power transmission using $100\,\upmu\mathrm{m}$ and $10\,\upmu\mathrm{m}$ long CPW transducers for Damon-Eshbach (DE, in blue) and Backward Volume (BV, in red) modes at frequency ranges around (a) $4\,\mathrm{GHz}$, (b) $9\,\mathrm{GHz}$ and (c) $25\,\mathrm{GHz}$ for input powers from $-40\,\mathrm{dBm}$ up to $10\,\mathrm{dBm}$. Raw data (in red and blue) are plotted together with the processed data with subtracted background (in grey) as a guideline for peak position. Raw data are plotted in dark [light] color (blue for DE or red for BV) when measured using $100\,\upmu\mathrm{m}$ [$10\,\upmu\mathrm{m}$] long transducers. The applied magnetic fields are depicted in Table \ref{['tab2']}. The data shown in this figure are also in Supplementary Material SupplMat at a larger scale and with a grid, and the measured data are available at Phaidra.
• Figure 4: Power characteristic and insertion losses extracted from raw data at the peak maximum at (a) $4\,\mathrm{GHz}$, (b) $9\,\mathrm{GHz}$ and (c) $25\,\mathrm{GHz}$ measured using $100\,\upmu\mathrm{m}$ (dark color) and $10\,\upmu\mathrm{m}$ (light color) long CPW transducers for Damon-Eshbach (DE, in blue) and Backward Volume (BV, in red) modes. The simulated trends are plotted in light grey for DE and in dark grey for BV. The applied magnetic fields are depicted in Table \ref{['tab2']}.
• Figure 5: Extracted (a) power threshold, (b) power limiting level and (c) insertion losses from data depicted in Fig. \ref{['fig3']} for Damon-Eshbach (DE, in blue) and Backward Volume (BV, in red) for CPW transducers of the length of $10\,\upmu\mathrm{m}$ (in light color) and $100\,\upmu\mathrm{m}$ (in dark color) at $4\,\mathrm{GHz}$, $9\,\mathrm{GHz}$ and $25\,\mathrm{GHz}$. The insertion losses were extracted in the linear region at the input power of $-30\,\mathrm{dB}$. For better visibility, there is a slight offset in frequency between the extracted values measured using different transducer lengths and spin-wave modes at the same frequency.