Active magnetostatic wave delay line

Two configurations for an active microwave delay line with feedback to improve the loss per unit delay time have been made and characterized. The lines utilized thin yttrium iron garnet (YIG) film, magnetostatic wave (MSW) passive elements, a microwave amplifier, and a variable attenuator connected in a feedback loop. The two delay line setups used a surface wave (MSSW) configuration with a single MG element and a nondispersive configuration with MSSW and backward volume wave (MSBVW) delay lines in series. For each setup, a sequence of delayed pulses at the output is observed when a single microwave pulse is fed to the input. The one-pass delay time T of the pulse through the MSW delay line and the number n of circulations in the feedback loop defines the total delay time nT for the nth pulse. The feedback resulted in a reduction in the output pulse decay rate and longer useful delay times. For a passive delay line with no feedback, typical values of the loss p.u. delay time L and useful delay time (nT)_U were -110 dB/μs and 0.1-0.2 μs, respectively. With feedback for the MSSW delay line, a 4.5-GHz operating frequency, and 40 ns input pulses, L and (nT)_U were -19 dB/μs and 0.6 μs, respectively. Feedback with the nondispersive delay line gave L and (nT)_U values of -12 dB/μs and 3 μS, respectively, for 4.5-GHz, 40-ns input pulses