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204 results on '"Stadius, Kari"'

2. Full-Duplex OFDM Radar With LTE and 5G NR Waveforms: Challenges, Solutions, and Measurements

Author

Barneto, Carlos Baquero, Riihonen, Taneli, Turunen, Matias, Anttila, Lauri, Fleischer, Marko, Stadius, Kari, Ryynänen, Jussi, and Valkama, Mikko

Subjects
Electrical Engineering and Systems Science - Signal Processing
Abstract

This paper studies the processing principles, implementation challenges, and performance of OFDM-based radars, with particular focus on the fourth-generation Long-Term Evolution (LTE) and fifth-generation (5G) New Radio (NR) mobile networks' base stations and their utilization for radar/sensing purposes. First, we address the problem stemming from the unused subcarriers within the LTE and NR transmit signal passbands, and their impact on frequency-domain radar processing. Particularly, we formulate and adopt a computationally efficient interpolation approach to mitigate the effects of such empty subcarriers in the radar processing. We evaluate the target detection and the corresponding range and velocity estimation performance through computer simulations, and show that high-quality target detection as well as high-precision range and velocity estimation can be achieved. Especially 5G NR waveforms, through their impressive channel bandwidths and configurable subcarrier spacing, are shown to provide very good radar/sensing performance. Then, a fundamental implementation challenge of transmitter-receiver (TX-RX) isolation in OFDM radars is addressed, with specific emphasis on shared-antenna cases, where the TX-RX isolation challenges are the largest. It is confirmed that from the OFDM radar processing perspective, limited TX-RX isolation is primarily a concern in detection of static targets while moving targets are inherently more robust to transmitter self-interference. Properly tailored analog/RF and digital self-interference cancellation solutions for OFDM radars are also described and implemented, and shown through RF measurements to be key technical ingredients for practical deployments, particularly from static and slowly moving targets' point of view., Comment: Paper accepted by IEEE Transactions on Microwave Theory and Techniques

Published
2019
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4. Adaptive Nonlinear RF Cancellation for Improved Isolation in Simultaneous Transmit-Receive Systems

Author

Kiayani, Adnan, Waheed, Muhammad Zeeshan, Anttila, Lauri, Abdelaziz, Mahmoud, Korpi, Dani, Syrjälä, Ville, Kosunen, Marko, Stadius, Kari, Ryynänen, Jussi, and Valkama, Mikko

Subjects
Electrical Engineering and Systems Science - Signal Processing
Abstract

This paper proposes an active radio frequency (RF) cancellation solution to suppress the transmitter (TX) passband leakage signal in radio transceivers supporting simultaneous transmission and reception. The proposed technique is based on creating an opposite-phase baseband equivalent replica of the TX leakage signal in the transceiver digital front-end through adaptive nonlinear filtering of the known transmit data, to facilitate highly accurate cancellation under a nonlinear TX power amplifier (PA). The active RF cancellation is then accomplished by employing an auxiliary transmitter chain, to generate the actual RF cancellation signal, and combining it with the received signal at the receiver (RX) low noise amplifier (LNA) input. A closed-loop parameter learning approach, based on the decorrelation principle, is also developed to efficiently estimate the coefficients of the nonlinear cancellation filter in the presence of a nonlinear TX PA with memory, finite passive isolation, and a nonlinear RX LNA. The performance of the proposed cancellation technique is evaluated through comprehensive RF measurements adopting commercial LTE-Advanced transceiver hardware components. The results show that the proposed technique can provide an additional suppression of up to 54 dB for the TX passband leakage signal at the RX LNA input, even at considerably high transmit power levels and with wide transmission bandwidths. Such novel cancellation solution can therefore substantially improve the TX-RX isolation, hence reducing the requirements on passive isolation and RF component linearity, as well as increasing the efficiency and flexibility of the RF spectrum use in the emerging 5G radio networks., Comment: accepted to IEEE

Published
2017
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9. Reconfigurable Signal Processing and DSP Hardware Generator for 5G and Beyond Transmitters

Author

Ghosh, Agnimesh, Spelman, Andrei, Cheung, Tze Hin, Boopathy, Dhanashree, Stadius, Kari, Gomony, Manil Dev, Valkama, Mikko, Ryynanen, Jussi, Kosunen, Marko, and Unnikrishnan, Vishnu

Abstract

The digital front-end of the communication transceivers envisioned for fifth-generation (5G) and beyond requires highly configurable high-performance digital signal processing (DSP) hardware operating at very high sampling rates to accommodate increasing signal bandwidths and support a range of modulation schemes and transmitter architectures. In this article, we present an efficient implementation of a highly configurable DSP hardware generator that can generate high-performance DSP hardware for multiple transmitter architectures including Cartesian, polar, outphasing, and multilevel outphasing modulators. The generated hardware unit, which consists of multistage multirate filters and other required DSP operations, runs at sample rates up to 4 GHz. The hardware supports an adjacent channel leakage ratio (ACLR) down to −48 dB and an error vector magnitude (EVM) of 0.78% with a 7-bit phase signal at a sampling rate of 4 GHz for multilevel outphasing modulation. Digital synthesis of the circuit in a 5-nm complimentary metal-oxide semiconductor (CMOS) process yields a core area consumption of 0.01 mm2 and an estimated power consumption of 37.2 mW for a 200-MHz bandwidth 5G new radio (NR) baseband (BB) signal.

Published
2024
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20. Leveraging frequency agility of an MIMO antenna cluster with a transmitter IC.

Author

Saleem, Ali Raza, Luomaniemi, Rasmus, Lehtovuori, Anu, Stadius, Kari, Kosunen, Marko, Viikari, Ville, and Ryynänen, Jussi

Subjects
FREQUENCY agility, ANTENNAS (Electronics), TRANSMITTERS (Communication), MOBILE antennas, INTEGRATED circuits
Abstract

This paper presents the prototype demonstration where an integrated transmitter circuit drives a mobile handset terminal antenna in order to provide frequency tunability and multiple input multiple output (MIMO) operation across the 0.5–4.5 GHz frequency range. The transmitter implementation incorporates on-chip weighted signal generation, i.e. amplitude and phase scaling to provide sufficient MIMO performance in the low band (700–960 MHz) and in the high band (1.5–4.5 GHz). In the transmitter, two antenna elements are used for MIMO operation in the low band and another two in the high band. The transmitter integrated circuit (IC) is fabricated in a 28 nm bulk CMOS technology with an active on-chip area of 0.2 mm $^2$. A custom antenna measurement procedure is proposed here in order to support and verify active antenna measurements with transmitter IC. A measurement procedure for the transmitter system comprising the transmitter IC and four antenna clusters is developed and discussed in comparison with traditional passive antenna measurements. The measurement results demonstrate that the transmitter IC driving the antenna clusters provides total antenna efficiency of $-6.5$ dB to $-1.5$ dB, and envelope correlation coefficient below 0.4 across the designated frequency bands. The results indicate that the implemented transmitter IC successfully tunes frequency response of the antenna clusters, and enhances the MIMO operation of such mobile antennas. [ABSTRACT FROM AUTHOR]

Published
2023
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31. A 1.5-5-GHz Integrated RF Transmitter Front End for Active Matching of an Antenna Cluster

Author

Saleem, Ali, Stadius, Kari, Hannula, Jari-Matti, Lehtovuori, Anu, Kosunen, Marko, Viikari, Ville, Ryynänen, Jussi, Jussi Ryynänen Group, Department of Electronics and Nanoengineering, Aalto-yliopisto, and Aalto University

Subjects
wideband antenna tuning, Hardware_GENERAL, Multiport antenna, Hardware_INTEGRATEDCIRCUITS, reconfigurable antenna, transmitter
Abstract

openaire: EC/H2020/704947/EU//ADVANTAG5 Lataa oa, kun julkaistu. A recently proposed method for realizing frequency-reconfigurable antennas across a wideband is based on adjusting the feed amplitudes and phases of a multiport antenna. In this article, we demonstrate the feasibility of the method, for the first time, with a conjunction of an integrated RF transmitter and a four-element antenna cluster. The implementation performs on-chip amplitude and phase tuning with supply scaling and delay tuning circuits to tune the antenna cluster without requirement of matching network. The antenna cluster is built with four closely spaced antenna elements implemented on a printed circuit board. The transmitter integrated circuit (IC) is implemented in a 28-nm CMOS process with the chip size of 0.85 mm x 0.95 mm, including pads. The proof-of-concept implementation demonstrates tunability across a wideband from 1.5 to 5 GHz.

Published
2020

36. Analysis and design of passive polyphase filters

Author

Kaukovuori, Jouni, Stadius, Kari, Ryynanen, Jussi, and Halonen, Karl A.I.

Subjects
Circuit design -- Methods, Electric filters -- Design and construction, Circuit designer, Integrated circuit design, Business, Computers and office automation industries, Electronics, Electronics and electrical industries
Abstract

Passive RC polyphase filters (PPFs) are analyzed in detail in this paper. First, a method to calculate the output signals of an n-stage PPF is presented. As a result, all relevant properties of PPFs, such as amplitude and phase imbalance and loss, are calculated. The rules for optimal pole frequency planning to maximize the image-reject ratio provided by a PPF are given. The loss of PPF is divided into two factors, namely the intrinsic loss caused by the PPF itself and the loss caused by termination impedances. Termination impedances known a priori can be used to derive such component values, which minimize the overall loss. The effect of parasitic capacitance and component value deviation are analyzed and discussed. The method of feeding the input signal to the first PPF stage affects the mechanisms of the whole PPF. As a result, two slightly different PPF topologies can be distinguished, and they are separately analyzed and compared throughout this paper. A design example is given to demonstrate the developed design procedure. Index Terms--Image reject, loss, passive polyphase filter (PPF), quadrature generation, transceivers.

Published
2008

43. A 2–5.5 GHz Beamsteering Receiver IC With 4-Element Vivaldi Antenna Array

Author

Zahra, Mahwish, primary, Kempi, Ilia, additional, Haarla, Jaakko, additional, Antonov, Yury, additional, Khonsari, Zahra, additional, Miilunpalo, Toni, additional, Ahmed, Nouman, additional, Inkinen, Juha, additional, Unnikrishnan, Vishnu, additional, Lehtovuori, Anu, additional, Viikari, Ville, additional, Anttila, Lauri, additional, Valkama, Mikko, additional, Kosunen, Marko, additional, Stadius, Kari, additional, and Ryynanen, Jussi, additional

Published
2020
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