A CMOS millimeter-wave (mmWave) downconversion mixer with a local-oscillator (LO) buffer is proposed for wireless Gb/s data-transfer enabling systems, such as 5G systems. To obtain high linearity at low supply voltages, the proposed mmWave downconversion mixer adopts an on-chip transformer-based topology. In order to achieve differential to single-ended conversion and IF output matching, while maintaining a high linearity performance, the proposed mmWave downconversion mixer incorporates an active balun with common-source and common-drain configurations employing common-mode noise and third-order intermodulation distortion cancellations. The proposed downconversion mixer with active balun and LO buffer was implemented using a 65-nm CMOS process and it draws 18 mA from a 1 V supply voltage. It demonstrates a gain greater than 5.6 dB, noise figure less than 10.9 dB, and third-order output intercept point more than 12.4 dBm, in the band from 57 to 66 GHz.

An external capacitor-less ultra low-dropout (LDO) regulator that can continue to provide high power-supply rejection (PSR) over a wide range of the load current is proposed. Using the loop-gain stabilizer (LGS) to fix the dc level of the output voltage of the error amplifier to the optimal value, the LDO can keep maximizing the unity-gain frequency, while the load current changes widely up to 200 mA. Despite the multiple poles in the regulating loop, the stability can easily be obtained due to an intrinsic left-half plane zero, generated by the auxiliary path of the LGS. The proposed LDO was fabricated in a 40-nm CMOS process, and it had an input voltage of 1.1 V. When the dropout voltage was 0.1 V and the load current was 200 mA, the measured PSRs were -60 and -35 dB at 1 and 10 MHz, respectively. Due to the LGS, the dc loop gain was maintained to be high, resulting in good load and line regulations of 19 μV/mA and 0.75 mV/V, respectively. While the total current consumption of the LDO was 275 μA, the LGS consumed only 7 μA. The area was 0.008 mm² with 4-pF on-chip capacitance for compensation.

A highly efficient CMOS linear power amplifier for WCDMA applications with feedback bias technique is presented. The method involves connecting the gates of common-gate devices of the driver stage and the power stage in cascode configurations by a feedback network for enhancing linearity. To achieve high efficiency and linearity simultaneously, large-signal IMD minimum (IMD sweet spot) is properly used at the desired output power level. The proposed PA was fabricated in a 0.18-μm CMOS technology. The experimental results demonstrate a gain of 26 dB, a maximum output power of 26 dBm with 46.4% of peak PAE, and a linear output power of 23.5 dBm with 40% PAE using a 3GPP WCDMA modulated signal. Both simulation and measurement results show an excellent large-signal IMD minimum at the output power using a WCDMA modulated signal.

A CMOS up-conversion mixer with an intermediate frequency (IF) amplifier and local oscillator (LO) buffer is presented for mobile 28-GHz-band 5G dual-conversion transceivers. A balun transformer with improved common-mode rejection ratio characteristics is proposed to improve the LO second-harmonic signal suppression, which is a problem in the up-conversion mixer of the 5G dual-conversion architecture. By applying the proposed balun transformer instead of the conventional one, a common-mode rejection ratio greater than 10 dB can be achieved at the frequencies of the LO second-harmonic leakage signal. An up-conversion mixer with an IF amplifier and LO buffer incorporating the proposed balun transformer was implemented in a 65-nm CMOS process, and it draws a current of 31.4 mA from a 1-V supply voltage. It provides a gain larger than 22.2 dB, a noise figure less than 4.1 dB, a thirdorder output intercept point higher than 4.6 dBm, and an LO second-harmonic leakage signal lower than -55.5 dBm in frequencies ranging from 26.5 GHz to 29.5 GHz. It also exhibits a suppression improvement of the LO second-harmonic leakage signal of approximately 14 dB with respect to an up-conversion mixer with IF amplifier and LO buffer using the conventional balun transformer. The proposed up-mixer with IF amplifier and LO buffer is the first one reported that addresses the 2LO leakage issue and the first demonstration of 2LO leakage signal suppression improvement for a 5G mmWave dual-conversion single-quadrature transmitter.