Niclas Keskitalo

Considerations when Designing and Using Virtual Instruments as Building Blocks in Flexible Measurement System Solutions

In this paper the software and hardware structure of a virtual instrument measurement system is discussed. The focus is on flexibility, modularity, generality and hardware independence. A software architecture that meets these requirements is proposed and discussed in some detail. The proposed software architecture has a layered structure that makes it suitable for implementation of versatile measurement systems. The measurement functionality is encapsulated in its own, hardware independent layer and communicates with its environment, e.g. physical hardware, through intermediary software components. Finally a measurement system for characterization of power amplifiers that is designed following the proposed software architecture, with software driven measurements, is implemented.

A general evaluation criteria for behavioral power amplifier modeling

In this paper a new goodness measure for behavioral complex envelope power amplifier models is defined in the frequency domain. The measure can be calculated for any input signal using the same formulas, which makes it general and easy to use. The results will however be dependent on the input signal. The total model error, or normalized mean-square error, for power amplifier models are normally dominated by the in-band error, often mainly caused by the linear distortion. The new measure is aimed at capturing the nonlinear modeling performance of the amplifier model. This is of interest since it is most often the nonlinear, rather than the linear, distortion that causes most harm in real-life power amplifier applications.

Effect of dopants on chemical mechanical polishing of Silicon

In microelectronic manufacturing, chemical mechanical polishing (CMP) of silicon is becoming a more and more important process. This work investigates the effect of dopants on CMP of silicon. A high boron concentration is found to reduce the removal rate. The boron induced reduction is clearly demonstrated by observing boron diffused areas on a wafer protrude during polishing. A high phosphorus concentration enhances the removal rate. It is also found that the removal rate is lower for the Si(111) compared to the Si(100) orientation.

A test-bed designed to utilize Zhu's general sampling theorem to characterize power amplifiers

Characterizing power amplifiers require test set-ups with performance superior to the power amplifiers. A commonly used method is to use an IQ-demodulator. However, problem arises due to imperfections in the demodulator such as IQ-imbalance; an alternative method is to use a direct down converter to intermediate frequency. The drawback then is the limited bandwidth. However, the required bandwidth of the ADC does not need to be exceptional. According to Zhus general sampling theorem is it enough to sample the output signal at the Nyquist rate of the input. However, even though the required sampling rate is reduced the demands on the analog bandwidth remains. Unfortunately, commercially available instruments such as vector signal analyzers can not be used for this purpose since their analog bandwidth is too small. In this paper a test-bed is designed to utilize the Zhus general sampling theorem. The RF front-end has frequency range of 500 MHz - 2.7 GHz and a bandwidth of 1 GHz. All performance data are verified with measurements.

Wideband characterization of a Doherty amplifier using behavioral modeling

A Doherty amplifier was investigated using behavioral amplifier modeling techniques. A measurement system for simultaneous wide bandwidth (>100 MHz) and large dynamic range (-70 dBc ACLR) sampled measurements that are needed for the behavioral modeling is presented. Both the measurement system and the performance of the Doherty amplifier are described. The findings are that the well known and widely used parallel Hammerstein model, also denoted the memory polynomial model, is well suitable also for modeling and predistortion of Doherty amplifiers, and that a Doherty amplifier can be designed with only minor memory effects. This is seen in the modeling error, which is reduced by 13 dB, compared with a constant gain, using a memoryless polynomial model and only 6 dB further by adding memory to the model.

Defect distributions in silicon implanted with low doses of MeV ions

Deep level transient spectroscopy (DLTS) is used to study the distributions as a function of depth of the single negative divacancy complex in n-type FZ silicon implanted with low doses of H, He an ...

Wideband characterization of power amplifiers using undersampling

In this paper a radio frequency power amplifier is measured and characterized by the use of undersampling based on the generalized Zhu-Frank sampling theorem. A test system has been designed allowing the bandwidth of the stimuli signal to be 100 MHz in the characterization process. That would not be possible with any vector signal analyzer on the market. One of the more challenging problem within the proposed concept is the model validation process. Here, two different techniques for model validation are proposed, the multitone and the spectrum scan validation methods.

Measurement of ACLR with high dynamic range

In this paper a method to overcome the insufficient dynamic range of RF measurement instruments, i.e. signal generators and spectrum analyzers, for distortion measurements on feedforward and other highly linear amplifiers, is discussed. A circuit board is designed, built and verified. Its performance is found to be superior to traditional methods using filters, both from a technical performance and flexibility standpoint as well as from an economic view. ACLR measurements for WCDMA signals can be done well below −70 dBc using the produced circuit board.

Automated multidimensional characterization of power amplifier for design and production

Designing, optimizing and producing modern power amplifiers (PA) requires new and fast RF (radio frequency) measurement techniques capable of characterizing its real behavior. PAs are a truly multidimensional device where many desired performance parameters are contradictory to each other. This is especially true for the generation of modern communication PAs that require high efficiency, high linearity as well as high bandwidth. This paper presents a software-defined measurement setup for fast and cost efficient multidimensional measurements based on highly accurate standard instruments and a PC. The test bed as well as the graphical user interface is presented along with a demonstration of its functionality. During tuning of tank networks, drain quiescent current, and bias conditions, 3-dimensional graphs can be selected for the most appropriate axes of trade-off parameters to display a true behavior of the PA under test subjected to real-world or close to real-world signals. The measurement system offers the possibility to monitor envelope-tracking dynamic power consumption up to 100 MHz plus the possibility to use high crest factors.

Nonlinear network analysis for modern communication devices and systems

This paper presents a novel test setup, based on a vector signal generator (VSG) and a vector signal analyzer (VSA), capable of nonlinear characterization of communications devices such as RF power amplifiers. Envelope time-domain waveform extraction and correction is applied to the DUT reference plane, preserving vector correction even in modulated environments where ingoing and outgoing signals from the ports of the DUT can be distinguished. This tool is valuable in the analysis of nonlinear devices, the generation of behavioral models and the study of memory effects..