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Efficient test strategies for Analog/RF circuits

Description

Test cost has become a significant portion of device cost and a bottleneck in high volume manufacturing. Increasing integration density and shrinking feature sizes increased test time/cost and reduce observability. Test engineers have to put a tremendous effort in order

Test cost has become a significant portion of device cost and a bottleneck in high volume manufacturing. Increasing integration density and shrinking feature sizes increased test time/cost and reduce observability. Test engineers have to put a tremendous effort in order to maintain test cost within an acceptable budget. Unfortunately, there is not a single straightforward solution to the problem. Products that are tested have several application domains and distinct customer profiles. Some products are required to operate for long periods of time while others are required to be low cost and optimized for low cost. Multitude of constraints and goals make it impossible to find a single solution that work for all cases. Hence, test development/optimization is typically design/circuit dependent and even process specific. Therefore, test optimization cannot be performed using a single test approach, but necessitates a diversity of approaches. This works aims at addressing test cost minimization and test quality improvement at various levels. In the first chapter of the work, we investigate pre-silicon strategies, such as design for test and pre-silicon statistical simulation optimization. In the second chapter, we investigate efficient post-silicon test strategies, such as adaptive test, adaptive multi-site test, outlier analysis, and process shift detection/tracking.

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Date Created
2012

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Built-in-self test of transmitter I/Q mismatch and nonlinearities using self-mixing envelope detector

Description

Built-in-Self-Test (BiST) for transmitters is a desirable choice since it eliminates the reliance on expensive instrumentation to do RF signal analysis. Existing on-chip resources, such as power or envelope detectors, or small additional circuitry can be used for BiST purposes.

Built-in-Self-Test (BiST) for transmitters is a desirable choice since it eliminates the reliance on expensive instrumentation to do RF signal analysis. Existing on-chip resources, such as power or envelope detectors, or small additional circuitry can be used for BiST purposes. However, due to limited bandwidth, measurement of complex specifications, such as IQ imbalance, is challenging. In this work, a BiST technique to compute transmitter IQ imbalances using measurements out of a self-mixing envelope detector is proposed. Both the linear and non linear parameters of the RF transmitter path are extracted successfully. We first derive an analytical expression for the output signal. Using this expression, we devise test signals to isolate the effects of gain and phase imbalance, DC offsets, time skews and system nonlinearity from other parameters of the system. Once isolated, these parameters are calculated easily with a few mathematical operations. Simulations and hardware measurements show that the technique can provide accurate characterization of IQ imbalances. One of the glaring advantages of this method is that, the impairments are extracted from analyzing the response at baseband frequency and thereby eliminating the need of high frequency ATE (Automated Test Equipment).

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Date Created
2012

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Design and calibration of a 12-bit current-steering DAC using data-interleaving

Description

High speed current-steering DACs with high linearity are needed in today's applications such as wired and wireless communications, instrumentation, radar, and other direct digital synthesis (DDS) applications. However, a trade-off exists between the speed and resolution of Nyquist rate

High speed current-steering DACs with high linearity are needed in today's applications such as wired and wireless communications, instrumentation, radar, and other direct digital synthesis (DDS) applications. However, a trade-off exists between the speed and resolution of Nyquist rate current-steering DACs. As the resolution increases, more transistor area is required to meet matching requirements for optimal linearity and thus, the overall speed of the DAC is limited.

In this thesis work, a 12-bit current-steering DAC was designed with current sources scaled below the required matching size to decrease the area and increase the overall speed of the DAC. By scaling the current sources, however, errors due to random mismatch between current sources will arise and additional calibration hardware is necessary to ensure 12-bit linearity. This work presents how to implement a self-calibration DAC that works to fix amplitude errors while maintaining a lower overall area. Additionally, the DAC designed in this thesis investigates the implementation feasibility of a data-interleaved architecture. Data interleaving can increase the total bandwidth of the DACs by 2 with an increase in SQNR by an additional 3 dB.

The final results show that the calibration method can effectively improve the linearity of the DAC. The DAC is able to run up to 400 MSPS frequencies with a 75 dB SFDR performance and above 87 dB SFDR performance at update rates of 200 MSPS.

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Date Created
2014

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Low-overhead built-in self-test for advanced RF transceiver architectures

Description

Due to high level of integration in RF System on Chip (SOC), the test access points are limited to the baseband and RF inputs/outputs of the system. This limited access poses a big challenge particularly for advanced RF architectures where

Due to high level of integration in RF System on Chip (SOC), the test access points are limited to the baseband and RF inputs/outputs of the system. This limited access poses a big challenge particularly for advanced RF architectures where calibration of internal parameters is necessary and ensure proper operation. Therefore low-overhead built-in Self-Test (BIST) solution for advanced RF transceiver is proposed. In this dissertation. Firstly, comprehensive BIST solution for RF polar transceivers using on-chip resources is presented. In the receiver, phase and gain mismatches degrade sensitivity and error vector magnitude (EVM). In the transmitter, delay skew between the envelope and phase signals and the finite envelope bandwidth can create intermodulation distortion (IMD) that leads to violation of spectral mask requirements. Characterization and calibration of these parameters with analytical model would reduce the test time and cost considerably. Hence, a technique to measure and calibrate impairments of the polar transceiver in the loop-back mode is proposed.

Secondly, robust amplitude measurement technique for RF BIST application and BIST circuits for loop-back connection are discussed. Test techniques using analytical model are explained and BIST circuits are introduced.

Next, a self-compensating built-in self-test solution for RF Phased Array Mismatch is proposed. In the proposed method, a sinusoidal test signal with unknown amplitude is applied to the inputs of two adjacent phased array elements and measure the baseband output signal after down-conversion. Mathematical modeling of the circuit impairments and phased array behavior indicates that by using two distinct input amplitudes, both of which can remain unknown, it is possible to measure the important parameters of the phased array, such as gain and phase mismatch. In addition, proposed BIST system is designed and fabricated using IBM 180nm process and a prototype four-element phased-array PCB is also designed and fabricated for verifying the proposed method.

Finally, process independent gain measurement via BIST/DUT co-design is explained. Design methodology how to reduce performance impact significantly is discussed.

Simulation and hardware measurements results for the proposed techniques show that the proposed technique can characterize the targeted impairments accurately.

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Date Created
2015