Robust Digital Predistortion for LTE/5G Power Amplifiers Utilizing Negative Feedback Iteration

A robust digital predistortion(DPD)technique utilizing negative feedback iteration is introduced for linearizing power amplifiers(PAs)in long term evolution(LTE)/5G systems.Different from the conventional direct learning and indirect learning structure,the proposed DPD suggests a two-step method to identify the predistortion.Firstly,a negative feedback based iteration is used to estimate the optimal DPD signal.Then the corresponding DPD parameters are extracted by forward modeling with the input signal and optimal DPD signal.The iteration can be applied to both single-band and dual-band PAs,which will achieve superior linear performance than the conventional direct learning DPD while having a relatively low computational complexity.The measurement is carried out on a broadband Doherty PA(DPA)with a 200 MHz bandwidth LTE signal at 2.1 GHz,and on a 5G DPA with two 10 MHz LTE signals at 3.4/3.6 GHz for validation in dual-band scenarios.

A compliant surgical robotic instrument with integrated IPMC sensing and actuation

Robotic assisted surgery is becoming widely adopted by surgeons for a number of reasons,which include improved instrumentation control and dexterity as well as faster patient recovery times and cosmetic advantages.Robotic assisted surgery is currently one of the fastest growing applications in robotics.Although the traditional robotic actuators which are currently used have advanced performance which can,in some aspects,surpass that of humans,they simply do not have the capabilities and diversity required to meet the demand for new applications in robotic surgery.Novel transducers which have advanced capabilities and which allow safe operation in delicate environments are needed.Ionic polymer-metal composites(IPMCs)have extensive desirable characteristics when compared with traditional actuators and as their transduction mechanisms can mimic biological muscle they have much potential for future advanced biomedical and surgical robotics.In this research,a complete two degree-of-freedom(2DOF)surgical robotic instrument has been developed,which with the attachment of surgical tools(scalpel,etc.)has the ability to undertake surgical procedures.The system integrates an IPMC sensor and actuator at each joint.A gain scheduled(GS)controller,which is tuned with an iterative feedback tuning(IFT)algorithm,has been developed to ensure an accurate and adaptive response.The main advantages of this device over traditional devices are the improved safety through a natural compliance of the joints as well as the mechanical simplicity which ensures ease of miniaturisation for minimally invasive surgery(MIS).The components of the system have been tested and shown to have the capabilities required to operate the device for certain surgical procedures,specifically a device work envelope of 1600 mm^(2),compliance of 0.0668 m/N while still maintaining enough force to cut tissue,IPMC sensor accuracy between 3-22%and a control system which has shown to guarantee zero steady state error.