A 190-to-220GHz 4-Bit Passive Attenuator with 1.4dB Insertion Loss and Sub-0.4dB RMS Amplitude Error Using Magnetically Switchable Coupled-Lines in 0.13µm CMOS Technology

This paper reports a new attenuator topology using magnetically switchable coupled-lines and switched transistors with dummies suitable for millimeter-wave and terahertz systems. In contrast to conventional topologies where the switch transistor on-resistance RON exists in signal path at reference state and contributes to insertion loss (IL) of attenuators, the proposed topology utilizes RON as part of the attenuation network at attenuation state and has zero contribution to attenuator IL. The degree of attenuation is established by switch transistor sizing with carefully designed impedance matching. The measured attenuator reveals excellent performance from 190 to 220GHz that is at least twofold of the operation frequencies in previous works. It also features small IL of 1.4–2.0dB and RMS amplitude error of 0.12–0.34dB only across the operation frequencies. The circuit occupies a core area of 0.026mm² and consumes zero DC power.