TY - CHAP A1 - Hörner, Eugen A1 - Bochtler, Ulrich A1 - Cervellino, Roman A1 - Zentgraf, Ralf A1 - Trunzer, Dominic A1 - Wölfel, Maximilian A1 - Böttcher, Arthur A1 - Schneider, Johannes T1 - Drahtlose Hochtemperaturmessung mit Oberflächenwellensensoren (OW-Sensor) T2 - Energy Harvesting Congress, München KW - Oberflächenwellenelement Y1 - 2013 ER - TY - THES A1 - Wölfel, Maximilian T1 - Hochintegriertes hardwaregestütztes Messverfahren zur Untersuchung von fehlerbehafteten Übertragungskanälen in TETRA-Objektfunkversorgungen KW - TETRA, Telekommunikation Y1 - 2018 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:91-diss-20180404-1403407-1-3 ER - TY - CHAP A1 - Probst, Anne-Catherine A1 - Hitzinger, Hans A1 - Bochtler, Ulrich A1 - Wölfel, Maximilian A1 - Schmitt, Christoph ED - U.R.S.I. Landesausschuss in Deutschland e.V. 2021, T1 - High Frequency Power Amplifier for Wideband Wireless Communication Systems T2 - Proceedings of the 2021 Kleinheubach Conference N2 - Increasing data transmission rates and bandwidth both belong to the challenges of the development of high-performance wireless communication systems. Multi-channel communication systems commonly use several narrowband power amplifiers each one for a single communication channel. Lossy couplers are needed both to separate the different channels from each other at the amplifiers input and to combine the amplified signals on each channel at the output. This approach depicts a poor efficiency and is limited to a few number of channels since each channel duplication involves 3 dB losses due to couplers. Alternatively, broadband radio frequency power amplifiers ensuring the simultaneous transmission of several carriers on a wide frequency range contribute to increase the cost and resource efficiency of transceivers in wireless communication systems. Gain flatness, a high output power, and low power levels of second and third order harmonics are required on the whole operating frequency range of the power amplifier in multi-carrier communication systems since overtones will degrade the quality of the communication. The present work investigates the performances of a broadband push-pull power amplifier based on LDMOS transistors, the input matching network using a 8:1 transmission line transformer. For the first time investigations on harmonic distortions of the amplified signal when using a transformer with 8:1 impedance transformation ratio are presented. Characterisation of the power amplifiers performances is focused on gain flatness, output power, harmonic distortions and efficiency at 110 W. KW - LDMOS KW - broadband RF power amplifier KW - push-pull KW - transmission line transformer KW - harmonic distortion KW - Hochfrequenzverstärker KW - Leistungsverstärker KW - Kommunikationssystem Y1 - 2021 U6 - https://doi.org/10.23919/IEEECONF54431.2021.9598443 VL - 2021 ER - TY - JOUR A1 - Köhler, Tim A1 - Wölfel, Maximilian A1 - Ciba, Manuel A1 - Bochtler, Ulrich A1 - Thielemann, Christiane T1 - Terrestrial Trunked Radio (TETRA) exposure of neuronal in vitro networks JF - Environmental Research N2 - Terrestrial Trunked Radio (TETRA) is a worldwide common mobile communication standard, used by authorities and organizations with security tasks. Previous studies reported on health effects of TETRA, with focus on the specific pulse frequency of 17.64 Hz, which affects calcium efflux in neuronal cells. Likewise among others, it was reported that TETRA affects heart rate variability, neurophysiology and leads to headaches. In contrast, other studies conclude that TETRA does not affect calcium efflux of cells and has no effect on people's health. In the present study we examine whether TETRA short- and long-term exposure could affect the electrophysiology of neuronal in vitro networks. Experiments were performed with a carrier frequency of 395 MHz, a pulse frequency of 17.64 Hz and a differential quaternary phase-shift keying (π/4 DQPSK) modulation. Specific absorption rates (SAR) of 1.17 W/kg and 2.21 W/kg were applied. In conclusion, the present results do not indicate any effect of TETRA exposure on electrophysiology of neuronal in vitro networks, neither for short-term nor long-term exposure. This applies to the examined parameters spike rate, burst rate, burst duration and network synchrony. KW - Neuronales Netz Y1 - 2018 U6 - https://doi.org/10.1016/j.envres.2017.12.007 VL - 2018 IS - 162 SP - 1 EP - 7 ER - TY - CHAP A1 - Köhler, Tim A1 - Wölfel, Maximilian A1 - Bochtler, Ulrich A1 - Thielemann, Christiane T1 - TETRA specific long-term exposure of neuronal in vitro networks T2 - BioEM2016 KW - Neuronales Netz Y1 - 2016 ER - TY - CHAP A1 - Neumaier, Marcel A1 - Probst, Anne-Catherine A1 - Wölfel, Maximilian A1 - Bochtler, Ulrich T1 - Performance Analysis in a Digital TETRA-Simulcast System T2 - 2025 16th German Microwave Conference (GeMiC) N2 - In radio communication of mission-critical services, resilient solutions are strongly required to account for public safety. Additionally to the cellular network based on the professional mobile radio European standard TETRA, a digital TETRA-simulcast system is proposed as a redundant network to ensure area coverage in case of base station failure caused e.g. by disasters. This paper presents a preliminary study about network planning of a frequency-efficient digital TETRA-simulcast system to be physically deployed in a hilly region of Germany. Coverage as well as ray tracing analysis and channel modeling were performed by simulations and prove to be helpful tools for the systematic optimization of system performances, especially with regard to the control of intersymbol interference in overlapping zones. KW - digital radio KW - intersymbol interference KW - overlapping zones KW - quasi-synchronous transmission KW - TETRA KW - TETRA, Telekommunikation Y1 - 2025 ER - TY - CHAP A1 - Probst, Anne-Catherine A1 - Neumaier, Marcel A1 - Hufgard, Christopher A1 - Wölfel, Maximilian A1 - Schmitt, Christoph A1 - Bochtler, Ulrich T1 - Network Planning a Digital TETRA-Simulcast-System T2 - Kleinheubacher Tagung, Miltenberg, 23.09.2025 - 25.09.2025 KW - TETRA, Telekommunikation Y1 - 2025 ER -