A Wideband Saw-Less Transmitter Operating in Closed-Loop With Embedded N-Path Filtering

The New Radio interface for 5G communications below 6 GHz need to support channels with bandwidths of up to 100 MHz. In the proposed transmitter, a passive mixer, located after a passive base-band stage, performs up-conversion and direct recombination of the I and Q signal in the current domain. This is done at the virtual ground of a closed-loop RF transimpedance amplifier (TIA) that directly drives the 50 Ω load through an integrated balun. Closed loop operation allows to meet the required linearity without using pre-distortion for a modulated signal of up to 3 dBm power. Measured results shows a RF bandwidth of 50 MHz. The dc power consumption at 1.8 V of supply is around 57.6 mW, resulting in an efficiency of 3.7% (Pout 3 dBm). The ACLR is -40 dBc, while the CIM3 is -49 dBc. The noise at 80 MHz offset from the carrier is -153.5 dBc/Hz.