A Tripler to 220 GHz Using a Back-To-Back Barrier N-N+ Varactor Diode Choudhary, D. ; Siegel, P. H. ; Räisänen, A. V. ; Martin, S. C. ; Smith, R. P. Abstract Publication: Fifth International Symposium on Space Terahertz Technology Pub Date: May 1994 Bibcode: 1994stt..conf..475C