A Wideband IQ-Mapping Direct-Digital RF Modulator for 5G Transmitters

Abstract

This article presents a wideband 2 × 12-bit direct-digital RF modulator (DDRM) operating in a 0.5-to-3-GHz band for 5G transmitters. The proposed digital Cartesian modulator features an advanced IQ-mapping technique to boost RF power by 3 dB and suppress the I/ Q image. To verify the proposed concept, a 40-nm CMOS prototype is implemented whose RF peak output power at 2 GHz is more than 14 dBm. It achieves an adjacent-channel leakage ratio (ACLR) of −52 dBc and an error vector magnitude (EVM) of −40 dB for a 20-MHz 256-QAM signal at 2.4 GHz. With a 320-MHz 256-QAM signal, the measured ACLR and EVM performances are better than −43 dBc and −32 dB at 2.4 GHz, respectively, without using any digital pre-distortion.

A Wideband Energy-Efficient Multi-Mode CMOS Digital Transmitter

“…11. It is categorized into interleaving [11], [20], [27] and non-interleaving modes [29], [32], featuring Cartesian or multi-phase operation utilizing LO clocks with different duty cycle. The multi-phase mode exploits the I/Q to multi-phase mapping.…”

“…17. In a Cartesian mode, these controlling signals are I/Q sign bits [I BB,UP [11] (Sign I ) and Q BB,UP [11] (Sign Q )]. The multi-phase operation modes demand 3-bit selection control signals to cover 8-octant, as discussed earlier.…”

“…To address these demands, digital TXs (DTXs) have emerged as favorable alternative architectures as they supplant the functionality of the conventional analog-intensive TXs circuit blocks, such as the baseband digital-to-analog converters (DACs), low-pass filter, mixer, and power amplifier (PA) with a single radio frequency DAC (RF-DAC) block [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15]. These DTXs consist of many unit cells comprising digital interpolation filters, bit-wise implicit mixers, and their digital PAs (DPAs).…”

“…Nonetheless, their Cartesian DTX [10], [11], [12], [13], [14], [15], [19] variants do not require a CORDIC, thus lowering the computing cost. The upconverted I BB /Q BB digital samples drive their respected RF-DACs that produce two RF signal components whose amplitudes are ideally proportional to the respective I/Q digital inputs.…”

Overview of Mobile Communications in Colombia and Introduction to 5G

“…Fifth-generation technology increases channel capacity with more bandwidth per carrier (from 5 to 400 MHz) [ 40 ], being spectrally more efficient due to the higher orders of the modulation schemes [ 41 , 42 ]. Previously employed in 4G, the multiple-input multiple output (MIMO) technique simultaneously uses multiple antennas with multiple channels for signal transmission and reception, increasing channel bandwidth and maintaining antenna efficiency without requiring additional power [ 43 , 44 ].…”