Ka-Band Compact Four-Way Power Dividers and Variable-Gain Low-Noise Amplifier for 5G Communications

We demonstrate the design and analysis of Ka-band miniature four-way Wilkinson power dividers (with CRC or RC isolation network) and variable-gain low-noise amplifier (VGLNA) for 5G systems. The four-way Wilkinson power divider with CRC (or RC) isolation network constitutes three two-way Wilkinson power dividers with CRC (or RC) isolation network. For the two-way power divider, a parallel capacitor is included at the input to compensate the imaginary part of the input admittance for input matching. Dual spiral structure with transmission line length of about λ/14 and symmetrical layout is adopted to achieve miniature chip area and small amplitude imbalance (AI) and phase difference (PD). Remarkable results are achieved. For instance, at 28 GHz, the two-way power divider (with CRC isolation network) achieves prominent S11 of − 12.1 dB, S22 and S33 of − 27 dB, S32 of − 17.4 dB, S21 of − 3.989 dB, S31 of − 3.964 dB, AI of − 0.025 dB, and PD of 0.171°. The normalized chip area is 9.8×10−5λ02. This is one of the smallest normalized chip areas ever reported for millimeter-wave power dividers. Moreover, the VGLNA constitutes a cascode input stage followed by a cascode output stage. To tune the power gain of the VGLNA, a current-steering transistor switch in parallel with the input transistor of the cascode output stage is adopted. A large gain tuning range of 14.9 dB is achieved.