Analysis and design of complex impedance transforming marchand baluns

Contribution for newspaper or weekly magazine English RESTRICTED
Michaelsen, Rasmus Schandorph ; Johansen, Tom Keinicke ; Tamborg, Kjeld M. (2014)
  • Publisher: IEEE
  • Related identifiers: doi: 10.1109/MIKON.2014.6899854
  • Subject: Aerospace | Communication, Networking and Broadcast Technologies | Components, Circuits, Devices and Systems | Fields, Waves and Electromagnetics | Photonics and Electrooptics | Signal Processing and Analysis | Balun | Capacitors | Complex impedance transformation | Impedance | Impedance matching | Integrated circuit modeling | Marchand balun | Mathematical model | Microwave theory and techniques | MMIC | Ports (Computers)

A new type of Marchand balun is presented in this paper, which has the property of complex impedance transformation. To allow the Marchand balun to transform between arbitrary complex impedances, three reactances should be added to the circuit. A detailed analysis of the circuit gives the governing equations. To verify the theory, a design and electromagnetic simulation of a lumped element Marchand balun is made in a SiGe BiCMOS technology. The lumped element impementation is favorable because capacitors are placed where the additional reactances should be added. Thus it is possible to absorb a positive reactance by reducing a capacitor. At the design frequency of 10.5 GHz it matches 50Ω to 50 - j66Ω. It has an insertion loss of 5.1 dB, an input reflection of −20.8 dB, as well as phase and magnitude imbalance better than 0.2° and 0.12 dB, respectively.
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