Noninverting Single-Spiral Power Divider and Its QC and Balun

We demonstrate noninverting single-spiral Ka-band (26.5-40 GHz) CMOS power divider and its quadrature coupler (QC) and balun. For the power divider, a parallel capacitor is included at the input port for matching, and a parallel RC network is connected between the output ports for matching and isolation. Transmission-line (TL) length of about $\lambda/12$ is adopted to achieve miniature area and small amplitude imbalance (AI) and phase difference (PD). Negative and positive phase-shift TLs with phase-shift of -45° (or -90°) and 45° (or 90°), respectively, are included at ports 2 and 3 of the power divider to form QC (or balun). Decent result is obtained. For example, the QC achieves S11 of -13.5dB, S22 of -14.5 dB, S33 of -19.4 dB, S32 of -10.5 dB, S21 of -4.713dB, and S31 of -4.731dB at 28 GHz. AI and PD deviation (PDD) are 0.018 dB and -0.1°, respectively. Moreover, S11 is smaller than -10dB for 10.4-50 GHz, equivalent to a fractional bandwidth (FBW) larger than 141.4%. The QC occupies a normalized area of $6.1\times 10^{-4}\lambda_{0}^{2}$, one of the smallest normalized areas ever reported for millimeterwave (mm-wave) QC or balun.