An H-Band mHEMT-Based Millimeter-Wave True-Time Delay MMIC

This paper reports the investigation of a monolithic millimeter-wave integrated True-Time Delay (TTD) circuit for H-Band frequencies (220-325 GHz), using Fraunhofer IAF 35-nm mHEMT technology. The circuit is based on a 4-bit-cascaded delay elements architecture, consisting of two single-pole double-throw switches and thin-film microstrip lines as delay and reference paths. A TTD circuit with 16 relative delay states is obtained with a maximum delay of 3.398 ps. It has a resolution of 0.227 ps with an RMS delay error less than 0.09 ps, and a relative bandwidth of 35% of the H-Band. The average insertion loss is 8.1 dB, and the return loss is better than 15 dB at the input and output. The results of this research work allow projecting a 4-bit TTD circuit and its inclusion in broadband transmit/receive applications.