Four-Way Power Divider and Distributed Attenuator for 39 GHz Bidirectional Phased-Array Transceiver

We demonstrate the design and analysis of a four-way power divider and a variable distributed attenuator for 39 GHz bidirectional phased-array transceiver. The four-way power divider can also be applied to a 60 GHz transceiver due to its wideband performance. The four-way power divider constitutes a dual-spiral two-way power divider, followed by two inverting-single-spiral two-way power dividers. Symmetrical spiral transmission line (TL) with length of $\lambda / 11-\lambda / 14$ is adopted to achieve miniature area and small amplitude imbalance (AI) and phase difference (PD). The power divider occupies a normalized area of $5.14 \times 10^{-4} \lambda_{0}{ }^{2}$, and achieves $S_{22}$ and $S_{33}$ of $\mathbf{- 1 7. 6 ~ d B, ~} S_{21}$ of $8.035 \mathrm{~dB}, \mathrm{~S}_{31}$ of $\mathbf{- 8. 1 6 3 \mathrm { dB }}$, AI of $\mathbf{0. 1 2 8} \mathrm{dB}$, and PD of $\mathbf{0. 1 4 5}^{\circ}$ at $\mathbf{4 0}$ GHz, one of the best results ever reported for four-way power dividers. Moreover, the distributed attenuator constitutes a synthetic TL in conjunction with 4 distributed linearity-boosted DTMOS-with- $\mathrm{R}_{\mathrm{B}}$ switch networks in series with an inductance L2 (for RMS phase error reduction due to the compensation of the parasitic capacitance effect). The distributed attenuator achieves excellent input 1 dB compression point ($\mathrm{IP}_{1 \mathrm{~dB}}$) of 20 dBm. For 4bit gain control ($-4 \sim-19 \mathrm{~dB}$) with $1 \mathrm{~dB} /$ step, the distributed attenuator achieves an RMS gain error of 0.01-0.5 dB, and RMS phase error of $4.5^{\circ}-5.9^{\circ}$ for 37-41 GHz.