Spin-wave microscale RF delay lines for mid- and high-frequency 5G band

Delay lines (DL) are crucial components in communication systems, providing the required time delays for signal timing, synchronization, and processing. DLs providing nanosecond-scale delays are conventionally based on acoustic waves; however, they cannot operate conveniently in a high-frequency range (EU 5G high-band 24.25–27.5 GHz) required by a modern generation of 5G communication technologies to speed up data transfer. The proposed solution is to use DL based on spin-wave (SW) transmission, as SW devices allow for operation at high-frequency ranges and can be scaled down to a few μm2. In this study, we investigate SW-based DL at the microscale at the frequency ranges of 4, 9, and 25 GHz. The DL is based on SW transmission between a pair of 250 nm wide microwave coplanar waveguide transducers, each with a footprint of 2.25×100μm2, and fabricated with varying mutual distances on a 97 nm thin yttrium iron garnet film. DLs are tested for in-plane SW modes (Damon–Eshbach and backward volume), and depending on the parameters, the extracted delay times are in the range of 6–165 ns. Furthermore, the insertion losses are extracted and compared to other DL concepts. Time-gating analysis of the measured transmission is performed, providing a detailed discussion of individual signal contributions to the measured spectra. Additionally, analytical theory is employed to compare the experimental delay times with analytical calculations and to predict how to adjust the device parameters to obtain variable time delays.