| 1. |
- Bremer, Johan, 1991, et al.
(author)
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Analysis of Lateral Thermal Coupling for GaN MMIC Technologies
- 2018
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In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 66:10, s. 4430-4438
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Journal article (peer-reviewed)abstract
- This paper presents a study of the lateral heat propagation in an aluminum gallium nitride/gallium nitride (AlGaN/GaN) heterostructure grown on a silicon carbide substrate. The study is enabled by the design of a temperature sensor that utilizes the temperature-dependent I-V characteristic of a semiconductor resistor, making it suitable for integration in GaN monolithic microwave integrated circuit technologies. Using the sensor, we are able to characterize the thermal transient response and extract lateral thermal time constants from the measurements. Time constants in the range from 25 mu s to 1.2 ms are identified. Furthermore, the heat propagation properties are characterized for heat source-to-sensor distances of 86-484 mu m, resulting in delay times from 3.5 to 111 mu s. It is shown that both the time constants and propagation delay increase with temperature. An empirical model of the sensor current versus temperature and voltage is proposed and used to predict the junction temperature of the sensor. The study provides knowledge for heat management design and proposes an integrated temperature measurement solution for future highly integrated GaN applications.
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| 2. |
- Bremer, Johan, 1991, et al.
(author)
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Compensation of Performance Degradation Due to Thermal Effects in GaN LNA Using Dynamic Bias
- 2018
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In: 2018 48th European Microwave Conference, EuMC 2018. - 9781538652855 ; , s. 1213-1216
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Conference paper (peer-reviewed)abstract
- This paper investigates the possibilities of using a dynamic bias control scheme for a low noise amplifier to compensate for performance degradation due to thermal effects. The study was performed by characterization of bias voltage and temperature dependence between -25°C to 75°C of a GaN MMIC LNA. The performance, in terms of gain, linearity and noise, degraded, at elevated chip temperatures. Nonlinear behavioral models were developed and used to predict performance for different bias and temperature conditions. Bias conditions to achieve constant gain and noise figure versus temperature are determined. Enhanced RF performance, with improved gain and linearity is demonstrated and is shown to require increased power and involves a trade-off between improving noise figure and gain.
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| 3. |
- Hanning, Lowisa, 1993, et al.
(author)
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Optimizing the Signal-To-Noise and Distortion Ratio of a GaN LNA using Dynamic Bias
- 2018
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In: 2018 91st ARFTG Microwave Measurement Conference: Wideband Modulated Test Signals for Network Analysis of Wireless Infrastructure Building Blocks, ARFTG 2018. - 9781538654491 ; 1
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Conference paper (peer-reviewed)abstract
- This paper shows how the signal-to-noise and distortion ratio (SNDR) for low noise amplifiers (LNA) can be derived from the commonly specified parameters noise figure, gain, third order output intercept point and 1 dB compression point. The parameters dependency of the biasing of the amplifier are also incorporated which enables the possibility to study how SNDR can be optimized for different operating conditions by dynamically change the gate- and drain voltage. An experimental verification shows that improvements in SNDR can be achieved by selecting gate- and drain voltage of the LNA according to the level of the input signal power.
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