@phdthesis{TomazdeCarvalho2024, author = {Tomaz de Carvalho, Antonio}, title = {A novel system for characterization of GaN-based low-noise amplifiers}, doi = {10.26127/BTUOpen-6844}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-68446}, school = {BTU Cottbus - Senftenberg}, year = {2024}, abstract = {Although low-noise amplifiers (LNA) are designed to amplify low RF power levels, there are possibilities that they receive high RF powers as front-end radios and electronic warfare receiver systems. Commonly, this high power levels are not desired. Due to such applications and demands, robust LNA are required. The GaN-based HEMT low-noise amplifiers are being considered an established technology used on different applications for telecommunications systems and radars. The GaN-based LNAs can handle high RF input powers, and they still keep functional. These GaN-based robust LNAs have several advantages, as no limiters are required to protect them against high RF input powers. As a result, these robust LNAs have a simplified RF receiver architecture and are cheaper to manufacture. However, the GaN HEMTs LNAs are known to show significant memory effects, which also play a negative role when a high RF input power level is received by the LNA and drives it into compression. After degradation of the LNA performance, it needs time to recover to its normal small-signal operation mode. This time is called recovery time. This is an important measurement parameter, once some applications require receivers to work immediately after a high RF input power was received, especially for pulse-radar applications. The main focus of this thesis is on the implementation of a novel measurement setup suitable to characterize the GaN-based robust LNAs and their recovery time. First, the system concept was implemented step by step using different instruments. The whole system setup has been programmed to work remotely, to perform the measurement and to save the results automatically. A software based on Matlab script language was developed and integrated to the system setup in order to control the test equipment. The setup allows for simultaneous measurements and data acquisitions. The setup can perform recovery time measurements in time domain, can measure the reflected power and also monitor the drain current of the LNA. A pulse signal is used as overdrive signal to stress the LNA with high-power levels, which can be variously defined in width and period according to the target application. This overdrive signal can also be monitored and measured during the recovery time characterization. The core of the measurement system is an PNA-X vector network analyzer, which allows the characterization of small-signal gain recovery time. The reflected power is measured using a power sensor, while the drain current is monitored using an oscilloscope. In order to validate the system setup, three different GaN LNAs were used. Finally, the system was extended to work also for 5 GHz frequency band. The results shown in this thesis enables for innovative future research activities on robust LNAs.}, subject = {Amplifier; LNA; Robust; GaN; Microwave; Rauscharmer Verst{\"a}rker; Robustheit; {\"U}berlastfall; MMIC; RF und Mikrowellentechnik; MMIC; Rauscharmer Verst{\"a}rker; Galliumnitrid; HEMT; {\"U}berlast}, language = {en} } @phdthesis{Fleischmann2022, author = {Fleischmann, Manfred}, title = {A novel technique to improve the spurious-free dynamic range of digital spectrum monitoring receivers}, doi = {10.26127/BTUOpen-5898}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-58984}, school = {BTU Cottbus - Senftenberg}, year = {2022}, abstract = {This dissertation presents a novel technique for enhancing the spurious-free dynamic range of radio monitoring receivers with a bandwidth of several gigahertz. The improvement is based on suppressing the discrete spurious signals that occur at higher drive levels in the output spectrum of the required broadband analog-to-digital converter. The achievable improvement of the spurious-free dynamic range is typically more than 20 dB, allowing better, gap-free monitoring of wide frequency ranges. The attenuation of the spurious signals is achieved by a unique combination of two separate analog-to-digital converters working in parallel and subsequent digital signal processing. The developed solution is not limited to broadband radio monitoring receivers but can generally suppress certain types of spurious signals generated during analog-to-digital conversion.}, subject = {Broadband receiver; Spurious signals; Analog-to-digital converter; Spurious-free dynamic range; Digital signal processing; Breitbandempf{\"a}nger; St{\"o}rsignale; Analog-digital-Wandler; St{\"o}rungsfreier Dynamikbereich; Digitale Signalverarbeitung; Analog-Digital-Umsetzer; Breitbandempf{\"a}nger; Digitale Signalverarbeitung; St{\"o}rsignal}, language = {en} } @phdthesis{Gerlich2016, author = {Gerlich, Stefan}, title = {Fully monolithically integrated X-band amplifiers with frequency selective feedback}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-39255}, school = {BTU Cottbus - Senftenberg}, year = {2016}, abstract = {The thesis addresses the design of monolithically integrated radio frequency amplifiers for X-band applications. The focus is on low-voltage low-noise amplifiers and efficient power amplifiers with high output power level. The challenge here is to realize stable amplifiers with remarkable performance metrics at low supply voltages. The general approach for stabilization amplifiers in the above frequency range is the use of a cascode topology which, however, requests higher supply voltages then single transistor operation. By using a special passive frequency-selective feedback, the use of the cascode topology could be avoided, and the amplifiers are stabilized over the entire frequency spectrum. Simultaneously, this feedback is used to neutralize the intrinsic feedback of the transistor at operating frequencies. As a result, a frequency dependent performance degeneration of the transistor can be mitigated. This work describes the influence of the passive frequency-selective feedback. Its usage as well its limitation are explained using the examples of a realized low noise amplifier and different power amplifiers. Further, the design of radio frequency amplifiers at X-band frequencies that employs silicon-germanium heterojunction bipolar transistors is described. All amplifiers were either incorporated in a 0.25 µm SiGe:C BiCMOS technology or in a 0.35 µm SiGe:C bipolar technology. The main achievements of this work include: - A 8.7 GHz narrow-band low noise amplifier incorporated in a 0.35 µm SiGe bipolar technology. The noise figure is 2.2 dB and the gain 28 dB at a supply voltage of 3 V. The low noise amplifier was subsequently used for a design of a double-balanced I/Q mixer. - Two packaged high efficient power amplifiers operating at a center frequency of 12 GHz. They are incorporated in a 0.35 µm SiGe bipolar technology. One amplifier uses a transformer-based output matching network and achieves 30.9 \% of power-added efficiency and 23.9 dBm of maximum output power at a supply voltage of 1.8 V. The second amplifier utilizes an LC-balun for impedance matching at the output and a power-added-efficiency of 38 \% at 1.8 V is measured. The maximum output power was 23.4 dBm. - A power amplifier in a 0.35 µm SiGe bipolar technology that uses power combining techniques to achieve 30 dBm (1 W) and 30 \% of power-added efficiency at 10 GHz and 2 V supply voltage. - Two power amplifiers, incorporated in a 0.25 µm SiGe:C BiCMOS technology, demonstrating the capability of a non-advanced SiGe process to be used for radio frequency power applications. Power combining techniques, the use of the passive frequency-selective feedback and layout optimization enables the realization of power amplifiers which exhibit an output power of 30 dBm and a power-added efficiency of 35 \% at supply voltages lower as 2.6 V.}, subject = {Amplifier; PA; X-Band; SiGe; Rauscharm; Leistungsverst{\"a}rker; Verst{\"a}rker; Low-Noise; SiGe; X-band; Hochfrequenzverst{\"a}rker; Leistungsverst{\"a}rker}, language = {en} }