Key analog/RF blocks for a programmable broadband actuator architecture

Abstract

n modern telecommunications, the ever increasing demands on signal bandwidth with the adoption of Millimeter Wave (mm-W) frequency bands for the Fifth-Generation (5G) standard make ensuring Power Amplifier (PA) linearity, while maintaining efficiency, a major challenge in the design of Transmitter (TX) circuits. As Digital Pre-
Distortion (DPD) linearizers become too power hungry for wide-band applications, various Analog Pre-Distortion (APD) techniques have been explored as alternatives. However, the applicability of these is typically limited to a single or a narrow range of PA
topologies. This work presents a novel concept for a combined DPD and APD system with a tunable transfer function for the APD allowing for digital control by the DPD based on the PA distortion characteristic. As a result power consumption can be reduced
compared to pure DPD and the system may be utilized to linearize a wide range of different PAs.

Popular Abstract

Wireless telecommunication, a facet of modern life which has completely altered the way human society functions. The simple ability to communicate across the globe almost instantaneously can be said to have redefined modern life. We are now able to contact friends and family whenever we wish, work remotely, communicate with strangers we would have never have been able to interact with were it not for the existence of these technologies, among numerous other things which would have been unimaginable to the average person living 50 years ago. This sudden paradigm shift in our lives has been enabled by the rapid development and mass adoption of modern communication technologies, which is still progressing as fast as ever at the time of writing.

A crucial concern in this field is ensuring that the information, transmitted through the air in the form of electromagnetic waves, is recognizable enough to be processed at the receiving end. Electromagnetic waves have two main properties: frequency and power. The frequency describes the speed at which a wave oscillates, that is, how many "peaks" and "valleys" appear in the wave over the course of 1 second. Power, on the other hand, is defined as the amount of energy contained in a wave, quite literally how powerful it is, meaning how tall the "peaks" and how deep the "valleys" are. Advantage is taken of both these quantities to ensure that information travels properly.

The frequency of a wave allows for it to be distinguished from radiation at other frequencies. Therefore, to make certain that signals from different devices do not interact or "mix", so called frequency "bands" are allocated for each signal, defining the frequencies it is allowed to occupy. This is typically referred to as the signal bandwidth, the width of its frequency band. Digital information is made up of bits and in general any useful piece of data contains multiple thousands of these. If the bandwidth of a signal is wide it can carry a large amount of information in a short amount of time, which enables fast communication. Consequentially, as the field develops and the demands on speed and the quantity of data to be transmitted increase (high quality video streaming for example), a central goal becomes to produce devices which are able to handle wider signal bandwidths.

The signal carrying this information must be powerful enough to travel the needed distance and not be drowned out by disturbances caused by the radiation which is ever present at all frequencies, known as "noise". A receiver system will always pick up this noise and the signal power must be high enough to ensure that the data is detectable. For this reason, the systems within our electronics which are responsible for transmission contain a component known as a power amplifier.

The power amplifier is responsible for amplifying the signal power before it is transmitted through the air. Naturally, since energy cannot be generated from nothing, a certain amount must be fed into these components. Some of this energy will be lost in the form of heat instead of being used for the intended purpose, a limitation of all electronics. In transmitter systems the power amplifiers are generally the most significant contributors to the overall power consumption. Additionally, the power efficiency of these devices will increase for stronger signals. Essentially, feeding a more powerful signal into the amplifier would make it more efficient, meaning that a larger part of the invested energy is converted to useful output signal compared to that wasted as excess heat. An issue, however, is the fact that power amplifiers distort stronger signals more, making them unusable after a certain point, setting a limit on how effectively the device may be utilized.

To remedy the issue of distortion caused by power amplifiers, while keeping efficient operation, a widely used technique is something called pre-distortion. The input signal is deformed in a way opposite to that which it would experience passing through the amplifier. As a result the distortion of the amplifier shapes the signal back into its original form and all information is preserved. The typical way this is done is via digital pre-distortion, deforming the signal based on mathematical algorithms applied in the digital domain. The advantage here is that the pre-distortion may be manipulated in any way desirable as any function may be applied to the digital signal. A core disadvantage is the fact that as the signal bandwidth increases, the digital circuitry must operate at faster rates while performing complex calculations, therefore consuming more energy. The entire goal of this technique is to make a more efficient system, but after a certain point digital pre-distortion becomes an ineffective solution.

For this reason a method known as analog pre-distortion has been explored for use at high signal bandwidths to save power. What is meant by analog here is that the processing is done on the signal after it has been converted from digital to analog form. This has the advantage of the circuitry not being required to perform any digital calculations, rather the pre-distortion is done by shaping the form of the analog signal directly. Unfortunately, the main benefit is also a major downside as analog circuitry cannot be easily reprogrammed and can typically only be applied to a single power amplifier design, good for highly specific use cases like satellite technologies, but making it less suitable for mass adoption in everyday consumer electronics.

The underlying idea behind the work done for this thesis is the possibility of combining these two methods in a sort of digital and analog hybrid pre-distortion system which would keep the advantage of re-programmability while retaining the increased efficiency of analog processing. More specifically, the thesis work revolves around designing the core block of the analog part for this system, which shapes the signal and is controlled by the digital component. The main challenge to be overcome is the design of analog circuitry fast enough to handle high bandwidth signals.

• author: Coti, Marin
• supervisor: Henrik Sjöland
• organization: Department of Electrical and Information Technology
• course: EITM02 20261
• year: 2026
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• report number: LU/LTH-EIT 2026-1168
• language: English
• id: 9246076
• date added to LUP: 2026-07-02 10:21:35
• date last changed: 2026-07-02 10:21:35