Based on a W-band high-power source, two schemes are proposed to realize a 335 GHz frequency multiplier source. The first scheme involves producing a 335 GHz signal with a two-stage doubler. The first doubler adopts two-way power-combined technology and the second stage is a 335 GHz doubler using a balanced circuit to suppress the odd harmonics. The measured output power was about 17.9 and 1.5 dBm at 167.5 and 335 GHz, respectively. The other scheme involves producing a 335 GHz signal with a single-stage quadrupler built on 50 µm thick quartz circuit adopting an unbalanced structure. The advantage of the unbalanced structure is that it can provide bias to the diodes without an on-chip capacitor, which is hard to realize with discrete devices. The measured output power was about 5.8 dBm at 337 GHz when driven with 22.9 dBm. Such 335 GHz frequency multiplier sources are widely used in terahertz imaging, radiometers, and so on.

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An improved architecture of sixth subharmonic mixers is proposed in this paper. In order to meet the need of low conversion loss, antiparallel diodes are selected and the length of four open/shorted microstrip stubs at both sides of the antiparallel diodes are carefully designed. For any important idle frequency components which can't be reused by the four stubs, reactive terminations are presented by adjusting the length of main RF and LO microstrip. The tested results indicate the lowest conversion loss is 26.1 dB at the radio frequency of 72 GHz, with fixed LO at 12 GHz. The proposed circuit architecture is suitable for the implementation of subharmonic mixers in E-band as well as other millimeter and submillimeter-wave regions where high quality and high frequency LOs are difficult to realize.

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