Spiral-Coupled-Line-Based Wilkinson Power Divider

A spiral-coupled-line-based Ka-band (26.5-40 GHz) CMOS Wilkinson power divider with a shunt capacitor (C) at the input and a shunt RC (or C) between the outputs is reported. The spiral coupled line, i.e., two noninverting spiral transmission lines (TLs) with magnetic coupling, has a positive mutual inductance. This leads to a significant TL-length reduction (from about λ/7 to λ/12) for a specific TL series inductance. At 33 GHz, the power divider achieves prominent S
₁₁
of -21.5, S
₂₂
of -22.1, S
₃₃
of -22.1, S
₃₂
of -26.1, S
₂₁
of -4.063, and S
₃₁
of -4.052 dB. The corresponding amplitude imbalance (AI) and phase difference (PD) are -0.011 dB and -0.336°, respectively. Moreover, S11 is smaller than -10 dB for 0-45.3 GHz, corresponding to 137.3% fractional bandwidth (FBW). S32 is smaller than -10 dB for 24.1-40.2 GHz, covering the Ka-band and corresponding to 48.8% FBW. The power divider occupies a normalized area of 1.2 × 10
^-4
λ
₀
²
, one of the smallest normalized chip areas ever reported for millimeter-wave power dividers.