9.7 An LTE SAW-less transmitter using 33% duty-cycle LO signals for harmonic suppression

An anti-alias harmonic-reject phase modulation for digital outphasing transmitter

“…The algorithm in [9] is also simulated using a 20 KHz bandwidth signal at 1 MHz carrier frequency with 10-bit phase resolution, and the result shows the ACLR is −65 dBc, as same as our work. Compared with the implementation in [7], our work avoids using 6 times multiple LO to generated 33% duty carrier, which is complex and power consumption. In addition, with a much lower 3xLO suppression, a much better CIM3/CIM5 performance can be achieved.…”

“…Outphasing transmitter is an attractive structure to achieve all these objectives [2,3,4,5]. However, digital outphasing transmitter suffers from ACLR degradation and OOB property deteriorated due to sampling images and harmonic components modulation, which are common problems for all kinds of digital transmitters [2,5,7,8,9,10]. To address these issues, many authors presented alternative modulation options.…”

“…To address these issues, many authors presented alternative modulation options. SAW-less 33% duty-cycle LO is an efficient scheme to achieve harmonic suppression; however, 6ÂLO increases power consumption and 33% duty-cycle leads into even harmonics [7]. Sigma Delta (AEÁ) modulation is another simple method to realize noise shaping for digital transmitters [5,8]; however, the operating frequency should be a multiple of carrier frequency, which is limited by the reconfigurable hardware resources.…”

Flexible Integrated Architectures for Frequency Division Duplex Communication

“…Most notably, further harmonic traps may be used to reduce the uncancelled fifth and higher harmonics to push the linearity of the transceiver to higher TX powers. An additional option is the use of a harmonic cancelling architecture for both the TX and DAC, similar to those of [66,67,44], in order to cancel the harmonics at the output of each device, obviating the need for resonant traps. Furthermore, the digital backend cancellation detailed in this work shows a large amount of potential for further research.…”

13.4 All-digital RF transmitter in 28nm CMOS with programmable RX-band noise shaping

“…In order to reduce costs and enable SAW-less operation, many recent transmitter implementations have thus targeted stringent out-of-band (OOB) emission levels. Analog-intensive TX architectures achieve low OOB noise at the price of large area consumption, as complex reconstruction filters are used to suppress DAC quantization noise and image replicas [1,2]. On the other hand, due to the lack of analog filtering, digital-intensive TX architectures need 12-14 bits of DAC resolution for low OOB noise, which complicates DAC design and typically requires DPD or calibration [3][4][5].…”