Robust stability characterizations of active metamaterials with non-Foster loads<xref rid="cpb_27_2_028102_fn1" ref-type="fn">*</xref><fn id="cpb_27_2_028102_fn1"><label>*</label><p>Project supported by the National Natural Science Foundation of China (Grant No. 61701349), the Natural Science Foundation of Shandong Province, China (Grant Nos. ZR2017QF012 and ZR2017MF042), and the Program for the Top Young Innovative Talents, China (Grant No. Q1313-03).</p></fn>

Robust stability characterizations of active metamaterials with non-Foster loads**

Project supported by the National Natural Science Foundation of China (Grant No. 61701349), the Natural Science Foundation of Shandong Province, China (Grant Nos. ZR2017QF012 and ZR2017MF042), and the Program for the Top Young Innovative Talents, China (Grant No. Q1313-03).

Fan Yi-Feng^{1, 1}, Sun Yong-Zhi^{1, 2, †}

(color online) Typical Nyquist plot of a closed loop transfer function for stable operating point indicated with PM and GM.^[33]