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Transistor random threshold voltage variations due to process fluctuations seriously affects the stability of Static Random Access Memory (SRAM). In this paper, a SRAM bit transistors threshold voltage $({Vth})$ deviation monitoring scheme and system is proposed. This scheme ingeniously achieves on-chip measurement of all transistors threshold voltages without altering compact SRAM bit array layout. Control signal strategies and Transistor ${Vth}$ Determination Circuit (TVDC) for different types of Devices Under Test (DUTs) have been proposed. The system is implemented using a 65 nm CMOS process with a core area of 0.01875mm2. Through Monte Carlo analysis, the Weighted Average (WA) difference of the proposed scheme and the direct measurement method is not more than 10mV, and the Root Mean Square Error (RMSE) difference is not more than 3mV. This system can also effectively detect the cell position of the transistor threshold voltage mismatch simulated by modifying the substrate voltage. For SRAM arrays of different scales, the method proposed in this paper has area efficiency and flexible reconfigurability. [ABSTRACT FROM AUTHOR]

Automated GUI testing consists of simulating user events and validating the changes in the GUI in order to determine if an Android application meets specifications. Traditional record-replay testing tools mainly focus on facilitating the test case writing process but not the replay and verification process. The accuracy of testing tools degrades significantly when the device under test (DUT) is under heavy load. In order to improve the accuracy, our previous work, SPAG, uses event batching and smart wait function to eliminate the uncertainty of the replay process and adopts GUI layout information to verify the testing results. SPAG maintains an accuracy of up to 99.5 percent and outperforms existing methods. In this work, we propose smart phone automated GUI testing tool with camera (SPAG-C), an extension of SPAG, to test an Android hardware device. Our goal is to further reduce the time required to record test cases and increase reusability of the test oracle without compromising test accuracy. In the record stage, SPAG captures screenshots from device's frame buffer and writes verification commands into the test case. Unlike SPAG, SPAG-C captures the screenshots from an external camera instead of frame buffer. In the replay stage, SPAG-C automatically performs image comparison while SPAG simply performs a string comparison to verify the test results. In order to make SPAG-C reusable for different devices and to allow bettersynchronization at the time of capturing images, we develop a new architecture that uses an external camera and Web services to decouple the test oracle. Our experiments show that recording a test case using SPAG-C's automatic verification is as fast as SPAG's but more accurate. Moreover, SPAG-C is 50 to 75 percent faster than SPAG in achieving the same test accuracy. With reusability, SPAG-C reduces the testing time from days to hours for heterogeneous devices. [ABSTRACT FROM PUBLISHER]

The residual phase noise (RPN) of externally modulated long microwave optical links (MOLs) is measured for the first time by means of a two-tone correlation-based method. In the conventional RPN measurement system with a double-balanced mixer, the phase noise of the reference microwave sources contributing to the noise floor will increase with the increasing of the delay of the device under test (DUT). This noise floor component is first suppressed here by correlating the measurement on two microwave tones, so as to improve the sensitivity of the RPN measurement system when measuring large-delay DUTs, such as long MOLs. In the experiments, the link lengths of 1 m, 2 km, and 6 km were employed, respectively. A noise floor of -142 dBc/Hz at 1-kHz offset and -152 dBc/Hz at 10-kHz offset were obtained when using two microwave tones at 9.5 and 9.6 GHz, the phase noises of which were both -124 dBc/Hz at 1-kHz offset and -131 dBc/Hz at 10 kHz. The RPN of a 6-km fiber link was successfully measured to be -130 dBc/Hz at 1 kHz offset and -140 dBc/Hz at 10-kHz offset. [ABSTRACT FROM PUBLISHER]

This article proposes a new class of sensors for built-in test in RF devices. These sensors are placed in close proximity to the DUT on the same substrate without being electrically connected to it. Instead, they monitor it by virtue of being subjected to the same process variations. The authors also describe other types of sensors they have studied, including DC probes, an envelope detector, and a current sensor. [ABSTRACT FROM PUBLISHER]