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A Fully Integrated Transformer-Coupled Active Power and Impedance Detector for WLAN 802.11ax 5 and 6 GHz Frequency Bands

Hagslätt, Holger LU (2024) EITM01 20241
Department of Electrical and Information Technology
Abstract
This thesis proposes a fully integrated transformer-coupled active power and antenna impedance detector for WLAN 802.11ax 5 and 6 GHz frequency bands. The detector is integrated into a transceiver, utilising the receive chain to down convert sensed RF voltage and current and digitally calculate the active power and antenna impedance on-chip. The RF current measurement is realized by a sense winding near the output transformer, while the RF voltage measurement is performed by capacitive voltage division.
This work presents a theoretical analysis of the detector’s viability, the coupling mechanisms, and power- and impedance-sensing accuracy. The proposed detector was designed and evaluated using the Cadence Virtuoso software in a 22 nm CMOS... (More)
This thesis proposes a fully integrated transformer-coupled active power and antenna impedance detector for WLAN 802.11ax 5 and 6 GHz frequency bands. The detector is integrated into a transceiver, utilising the receive chain to down convert sensed RF voltage and current and digitally calculate the active power and antenna impedance on-chip. The RF current measurement is realized by a sense winding near the output transformer, while the RF voltage measurement is performed by capacitive voltage division.
This work presents a theoretical analysis of the detector’s viability, the coupling mechanisms, and power- and impedance-sensing accuracy. The proposed detector was designed and evaluated using the Cadence Virtuoso software in a 22 nm CMOS technology. Multiple sense winding layouts were created and analysed to understand which design choices contribute to accurate current sensing.
Both power- and impedance-sensing accuracy are solely determined by the accuracy of estimations of proportionality factors between sensed and actual active power and antenna impedance, as well as the relative phase shift between the sensed current and voltage. The estimations are accurate if the values during the detector’s use remain similar to the estimated values found during calibration.
The detector was proven to work in the frequency range of 5.15-7.125 GHz, and the maximum insertion loss in this frequency range was 0.42 dB. At 6 GHz, 50◦C, and a VSWR of 3, the power sensing error was ≤0.42 dB, and the impedance sensing magnitude/phase errors were ≤0.039 and ≤2.7◦, respectively. At 5.15- 7.125 GHz, −40-125◦C, and a VSWR of 3, the power sensing error was ≤1.75 dB, and the impedance sensing magnitude/phase errors were ≤0.071 and ≤13.3◦, respectively. The detector had a footprint area of 825 μm2. (Less)
Popular Abstract
The Internet’s increased popularity has been a major cause of the biggest cultural and technical revolutions in the last decades. It has made it possible to obtain an almost unlimited amount of information, watch cute animal videos, have face-to-face conversations with friends and family on the opposite side of the world, and if it is in your interest, you can create hostile bot farms and propaganda networks to undermine the fabric of democratic nations.

Wi-Fi is a technology that allows our devices to connect to the internet wirelessly. In any Wi-Fi network, a router acts as the middleman between your devices (like your phone or laptop) and the internet. The router is connected to an Internet Service Provider (ISP), which actually... (More)
The Internet’s increased popularity has been a major cause of the biggest cultural and technical revolutions in the last decades. It has made it possible to obtain an almost unlimited amount of information, watch cute animal videos, have face-to-face conversations with friends and family on the opposite side of the world, and if it is in your interest, you can create hostile bot farms and propaganda networks to undermine the fabric of democratic nations.

Wi-Fi is a technology that allows our devices to connect to the internet wirelessly. In any Wi-Fi network, a router acts as the middleman between your devices (like your phone or laptop) and the internet. The router is connected to an Internet Service Provider (ISP), which actually provides the connection to the Internet.

When you connect to Wi-Fi, your device and the router communicate using radio waves, much like radios or TVs. These radio waves travel back and forth between the router and your device, carrying data packets (small bits of information). When you request something on the internet, like loading a web page, your device sends data packets to the router, which then sends them to the ISP, which reaches out to the server that hosts the website. The server replies with the requested data, which travels back through the ISP to your router, and finally to your device.
The radio waves are created by oscillating electrical currents in an antenna, which generate electromagnetic waves that travel through the air. These waves spread out in all directions, radiating away from the antenna. The waves travel at the speed of light, carrying the data across the air. Other devices with Wi-Fi can pick up these signals. When these waves reach the receiving device, their antenna captures them and converts them back into electrical signals.
A common way of connecting any electrical device to Wi-Fi is to connect it to a so-called integrated circuit (IC) dedicated to handling these Wi-Fi signals. Often, the IC is, in turn, connected to an antenna.

This thesis aims to design a detector integrated into a Wi-Fi IC that measures the power (energy per unit time) sent from the antenna as well as the antenna impedance (a measure of how much something resists the flow of electrical current in a circuit. You can think of it as a kind of “friction” for electricity).


By obtaining the information from the two measurements, a couple of benefits to the ICs performance can be gained. First of all, to market and sell Wi-Fi ICs in a specific market, it must be verified that the device complies with regulations put forward by ETSI (European Telecommunications Standards Institute), FCC (Federal Communications Commission), or an equivalent regulatory body. One such requirement applicable to Wi-Fi is limiting the maximum power radiated into the air. With the power measurement, it becomes possible to optimize the power given the situation while complying with the regulations. If you don’t need to have a very high power you can limit it to reduce energy consumption of the IC and if maximum range from the antenna is needed you can maximise the power. The antenna impedance measurement provides information regarding how well the antenna is fitting the specific IC. For example, to optimize the IC’s energy efficiency it is important for the antenna to match the IC well.

The power and antenna impedance can indirectly be measured by measuring the current and voltage delivered to the antenna. This thesis investigates how current and voltage measurements can be optimally performed to achieve high accuracy. Mathematical models are derived and multiple design possibilities are compared and analysed. The final proposed power and impedance detector was shown to function and achieve accurate measurements. The findings could be used to integrate a detector into a Wi-Fi IC that is manufactured and sold. (Less)
Please use this url to cite or link to this publication:
author
Hagslätt, Holger LU
supervisor
organization
alternative title
En fullt integrerad transformator-kopplad aktiv effekt- och impedansdetektor för WLAN 802.11ax 5 och 6 GHz frekvensband
course
EITM01 20241
year
type
H2 - Master's Degree (Two Years)
subject
report number
LU/LTH-EIT 2024-1032
language
English
id
9178104
date added to LUP
2024-11-22 13:24:21
date last changed
2024-11-22 13:24:21
@misc{9178104,
  abstract     = {{This thesis proposes a fully integrated transformer-coupled active power and antenna impedance detector for WLAN 802.11ax 5 and 6 GHz frequency bands. The detector is integrated into a transceiver, utilising the receive chain to down convert sensed RF voltage and current and digitally calculate the active power and antenna impedance on-chip. The RF current measurement is realized by a sense winding near the output transformer, while the RF voltage measurement is performed by capacitive voltage division.
This work presents a theoretical analysis of the detector’s viability, the coupling mechanisms, and power- and impedance-sensing accuracy. The proposed detector was designed and evaluated using the Cadence Virtuoso software in a 22 nm CMOS technology. Multiple sense winding layouts were created and analysed to understand which design choices contribute to accurate current sensing.
Both power- and impedance-sensing accuracy are solely determined by the accuracy of estimations of proportionality factors between sensed and actual active power and antenna impedance, as well as the relative phase shift between the sensed current and voltage. The estimations are accurate if the values during the detector’s use remain similar to the estimated values found during calibration.
The detector was proven to work in the frequency range of 5.15-7.125 GHz, and the maximum insertion loss in this frequency range was 0.42 dB. At 6 GHz, 50◦C, and a VSWR of 3, the power sensing error was ≤0.42 dB, and the impedance sensing magnitude/phase errors were ≤0.039 and ≤2.7◦, respectively. At 5.15- 7.125 GHz, −40-125◦C, and a VSWR of 3, the power sensing error was ≤1.75 dB, and the impedance sensing magnitude/phase errors were ≤0.071 and ≤13.3◦, respectively. The detector had a footprint area of 825 μm2.}},
  author       = {{Hagslätt, Holger}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{A Fully Integrated Transformer-Coupled Active Power and Impedance Detector for WLAN 802.11ax 5 and 6 GHz Frequency Bands}},
  year         = {{2024}},
}