Multiband Reconfigurable Broadband Transmitter Supporting 5G New Radio

This article presents a 1.5–4-GHz transmitter with a reconfigurable 10–200-MHz signal bandwidth, supporting multiband in 5G new radio (NR). A fully differential operational amplifier (OPA) with novel capacitor-coupled feedforward compensation is proposed to support broadband analog baseband (ABB) with enhanced efficiency and linearity. The linear-in-dB gain control method, utilizing the thermometer code and the reusable resistor block (RB), is proposed to ensure accurate and monotonic gain control. The proposed two-stage push–pull power driver amplifier (PDA), covering the 1.5–4-GHz range, employs an efficiency-enhanced on-chip transformer and switched-capacitor arrays to support broadband operation. Designed using a CMOS large-signal (LS) nonlinear model and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {G}_{\mathrm {3}}$ </tex-math></inline-formula> fluctuation method, the complementary PDA extends the linear operating range, mitigates AM–PM distortion, and improves efficiency. Moreover, the matching network is systematically analyzed to achieve the most efficient power transfer and load matching. To compensate for the dc offset caused by process, voltage, and temperature (PVT) variations, as well as the dc level mismatch between ABB stages, both digital dc offset calibration circuits and an analog level shifter are integrated on-chip. The transmitter is implemented in 55-nm CMOS with a 1.8/2.5-V power supply and a core chip area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {2.99 mm}^{2}$ </tex-math></inline-formula>. The transmitter achieves S22 output matching below −12 dB across the 1.5–4-GHz frequency range and provides a 36-dB gain range with a 0.375-dB step. The measured error vector magnitude (EVM) for the NR40MHz signal is 1.67% at 4.2-dBm average output power in n41 and 1.54% at 3.7-dBm average output power in n78, with corresponding adjacent channel power ratio (ACPR) of −48.75 and −48.067 dBc, respectively.