Design Of W-band Harmonic Mixer In SiGe BiCMOS Technology

W-band frequency is now widely used in the millimeter wave communication, imaging radar. Using a harmonic mixer can make the local frequency (LO) become 1/2, 1/3 or even lower of the radio frequency (RF), and then reduce the cost of W-band systems and lower the technical difficulties. So designing a harmonic mixer with excellent performance and high reliability has a high practical value.In this paper, 0.13μm SiGe BiCMOS technology is used for harmonic mixer design. Based on the harmonic mixing principle and design requirements, theoretical analysis and simulation design are both carried out for passive balun. And two structures are chosen for the design of W-band mixer:third harmonic mixer with multiplier and third harmonic double balance mixer.For W-band balun, multilayer coupling structure is used. Furthermore, in order to reduce the size of balun, symmetrical S structure is utilized. The size of W-band balun is 150μm×220μm, the bandwith is 65-105GHz, the insertion loss is less than 4.8dB, amplitude unbalance is less than 0.7dB, and phase unbalance is less than 10 degrees. For Ka-band balun, planar structure is utilized. The the proposed Ka-band balun has a compact size because of its spiral shape. The size of Ka-band balun is 120μm×340μm, the bandwith is 20～40GHz, the insertion loss is less than 4.5dB, amplitude unbalance is less than 0.6dB, and phase unbalance is less than 11 degrees.Based on theoretical analysis and computer simulation, this paper completed the design and layout drawing of these two mixers. Third harmonic mixer with multiplier is composed of tripler, amplifier and gilbert mixer. The simulation results show that it can achieve 81～91 GHz RF bandwidth, its intermediate frequency (IF) is 1GHz, the conversion loss is 7.3-9.2dB, the LO to IF isolation is greater than 35 dB and the LO to RF isolation is greater than 50 dB, the size of chip is 1290μm×865μm. For third harmonic double balance mixer, the simulation results show that it can achieve 81-91 GHz RF bandwidth, its IF is 1GHz, the conversion loss is 7-8dB, the LO to IF isolation is greater than 35 dB and the 3LO to RF isolation is greater than 45 dB, the size of chip is 1030μm×920μm. Compared with the former mixer, the third harmonic double balance mixer has smaller size and better temperature stability The simulation results of these two mixers are better than the requirements, which laid a foundation for tapout.Finally, the third harmonic mixer with multiplier has been tapout and tested. From the measured results, it can be seen that the conversion loss of the mixer is 13.2-17dB, the LO/IF isolation is great than 30dB, the LO/RF isolation is great than 33dB. Some of the conversion loss are not as good as expected, further exploration and optimization should be done for the structure and design of the circuit. The study of the W-band harmonic mixer in this paper has an important practical significance.