# Low Power Microwave Signal Detection With a Spin-Torque Nano-Oscillator in the Active Self-Oscillating Regime

## TL;DR

This paper demonstrates that a spin-torque nano-oscillator can rapidly analyze microwave spectra over a wide bandwidth with high sensitivity, offering a fast and efficient alternative to traditional detectors.

## Contribution

The study introduces a novel application of STNO as a high-speed, wideband spectrum analyzer with a linear response and low detection threshold, validated through numerical analysis.

## Key findings

- STNO can scan a 10 GHz bandwidth in less than 100 ns.
- Output voltage is proportional to input microwave amplitude with high sensitivity.
- Minimum detectable signal is about 1 pW at low scanning rates.

## Abstract

A spin-torque nano-oscillator (STNO) driven by a ramped bias current can perform spectrum analysis quickly over a wide frequency bandwidth. The STNO spectrum analyzer operates by injection locking to external microwave signals and produces an output DC voltage $V_{\rm dc}$ that temporally encodes the input spectrum. We found, via numerical analysis with a macrospin approximation, that an STNO is able to scan a $10~\rm GHz$ bandwidth in less than $100~\rm ns$ (scanning rate $R$ exceeds $100~\rm MHz/ns$). In contrast to conventional quadratic microwave detectors, the output voltage of the STNO analyzer is proportional to the amplitude of the input microwave signal $I_{\rm rf}$ with sensitivity $S = dV_{\rm dc}/dI_{\rm rf} \approx 750~\rm mV/mA$. The minimum detectable signal of the analyzer depends on the scanning rate $R$ and, at low $R \approx 1~\rm MHz/ns$, is about $1~\rm pW$.