Saab AB

About: Saab AB is a company organization based out in Thun, Switzerland. It is known for research contribution in the topics: Signal & Antenna (radio). The organization has 862 authors who have published 928 publications receiving 8807 citations. The organization is also known as: Saab AB & Svenska Aeroplan AB.

Arrangement and method for cross-monitoring of sensor data

Abstract: The present invention relates to a arrangement for cross monitoring two independent signals (s1(t), s2(t)). The arrangement comprises means (100; 305; 730) for calculating a value (y(t)) depending upon a signal value (s(t)), drift value ( v ) and a feedback value (g(t-1)), and means (100; 309; 310) for determining a larger one (g(t)) of the calculated value (y(t)) and a first predetermined value (P). The arrangement also comprises means (100; 320) for comparing said determined larger value (g(t)) with a second predetermined value (h) and means (100; 330) for delaying said determined larger value (g(t)) and change status of said larger value (g(t) to become an updated feedback value (g(t-1)) to be provided to the means for calculating the value (y(t)). The arrangement is characterized in that the signal value s(t) comprises information about an absolute value of a difference between the two independent generated signals (s1(t), s2(t)).

Main rotor arrangement of an UAV-helicopter

Abstract: A main rotor arrangement for an UAV-helicopter. A rotor mast defines a vertical axis of rotation. A hub is for attachment of rotor blades. The hub is mounted to the rotor mast in a tiltable way so as to reduce loads acting on the rotor blades during operation of the UAV-helicopter. A damping assembly is configured to damp the tilting of the hub.

Analysis of Lateral Thermal Coupling for GaN MMIC Technologies

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 $\mu \text{s}$ to 12 ms are identified Furthermore, the heat propagation properties are characterized for heat source-to-sensor distances of 86– $484~\mu \text{m}$ , resulting in delay times from 35 to $111~\mu \text{s}$ 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

On Thermomechanical Durability Analysis Combined With Computational Fluid Dynamics Thermal Analysis

Abstract: Manufacturers of aerospace, defense, and high performance (ADHP) equipment are currently facing multiple challenges related to the reliability of electronic systems. The continuing reduction in size of electronic components combined with increasing clock frequencies and greater functionality, results in increased power density. As an effect, controlling the temperature of electronic components is central in electronic product development in order to maintain and potentially improve the reliability of the equipment. Simultaneously, the transition to lead-free electronic equipment will most probably propagate also to the ADHP industry. Compared to well-proven tin-lead solder, the knowledge about field operation reliability of lead-free solders is still limited, as well as the availability of damage evaluation models validated for field temperature conditions. Hence, the need to fill in several knowledge gaps related to reliability and reliability prediction of lead-free solder alloys is emphasized. Having perceived increasing problems experienced in the reliability of fielded equipment, the ADHP industry has suggested inclusion of physics-of-failure (PoF) in reliability prediction of electronics as one potential measure to improve the reliability of the electronic systems.This thesis aims to contribute to the development of reliable ADHP systems, with the main focus on electronic equipment for the aerospace industry. In order to accomplish this, the thesis provides design guidelines for power distribution on a double-sided printed circuit board assembly (PBA) as a measure to improve the thermal performance without increasing the weight of the system, and a novel, computationally efficient method for PoF-based evaluation of damage accumulation in solder joints in harsh, non-cyclic field operation temperature environments.Thermal fatigue failure mechanisms and state‑of‑the‑art thermal design and design tools are presented, with focus on the requirements that may arise from avionic use, such as low weight, high reliability, and ability to sustain functional during high vibration levels and high g-forces. Paper I, II, and III describes an in-depth investigation that has been performed utilizing advanced thermal modeling of power distribution on a double-sided PBA as a measure to improve the thermal performance of electronic modules.Paper IV contributes to increasing the accuracy of thermal fatigue life prediction in solder joints, by employing existing analytical models for predicting thermal fatigue life, but enhancing the prediction result by incorporating advanced thermal analysis in the procedure.Papers V and VI suggest and elaborate on a computational method that utilizes surrogate stress and strain modeling of a solder joint, to quickly evaluate the damage accumulated in a critical solder joint from non-cyclic, non-simplified field operation temperature profiles, with accuracy comparable to finite element modeling. The method has been tested on a ball grid array package with SnAgCu solder joints. This package is included in an extensive set of accelerated tests that helps to qualify certain packages and solder alloys for avionic use. The tests include -20°C to +80°C and -55°C to +125°C thermal cycling of a statistically sound population of a number of selected packages, assembled with SnAgCu, Sn100C, and SnPbAg solder alloys. Statistical analysis of the results confirms that the SnAgCu-alloy may outperform SnPbAg solder at moderate thermal loads on the solder joints.In Papers VII and VIII, the timeframe is extended to a future, in which validated life prediction models will be available, and the suggested method is expected to increase the accuracy of embedded prognostics of remaining useful thermal fatigue life of a critical solder joint.The key contribution of the thesis is the added value of the proposed computational method utilized in the design phase for electronic equipment. Due to its ability for time-efficient operation on uncompressed temperature data, the method gives contribution to the accuracy, and thereby also to the credibility, of reliability prediction of electronic packages in the design phase. This especially relates to applications where thermal fatigue is a dominant contributor to the damage of solder joints.

Analysis of Compensation Methods and the Capability Boundary for Element Position Errors in Electrically Scanned Arrays

Abstract: Mechanical translational tolerances have negative effects on the radiation patterns in sensor and antenna arrays. Methods for restoring the radiation pattern of an array with element position errors to the designed one without the position errors have been investigated and the limits of their capabilities in different scenarios of real array configurations explored. A proof of concept has been established by manufacturing an intentionally erroneous antenna array and applying investigated compensation methods. Conclusion is that the possibilities of compensating for mechanical errors are greatly enhanced with increased digitalisation of the array antenna system. Analog systems may achieve a full compensation in a smaller solid angle, while digital systems can achieve a full compensation covering almost the half space.