Spiral-TL-Based Compact Ka-Band SPDT Switch and Power Divider

We demonstrate compact spiral-transmission-line (TL)-based Ka-band SPDT (single-pole double-throw) switch and Wilkinson power divider (with CRC isolation network) for millimetre-wave (mm-wave) 5G communications. For the power divider, a parallel capacitor is included at the input port to compensate the imaginary part of the input admittance for input matching. Dual spiral structure with TL length of about $\lambda / 14$ and symmetrical layout is used to achieve compact chip area and small amplitude imbalance (AI) and phase difference (PD). At 28 GHz, the power divider achieves prominent S
11
of -12.1 dB, S
22
and S
33
of -27 dB, S
32
of -17.4 dB, S
21
of -3.989 dB, S
31
of -3.964 dB, AI of -0.025 dB, and PD of 0.171°. The normalized chip area is $9.8 \times 10^{-5} \lambda_{0}^{2}$, one of the smallest normalized chip areas ever reported for mm-wave power dividers. For the SPDT switch, parallel capacitors are included at ports 1-3 to reduce the required TL length of the equivalent $\lambda / 4$ TLs for compact size. For 25-30 GHz, the SPDT switch achieves decent in less than 1.6 dB and isolation better than -30.4 dB.