The use of linear modulation and complex access schemes has increased the linearity requirements of the power amplifiers used in wireless communication systems. To maintain system capacity and avoid interference, external linearization circuitry must be added to correct the distortion created by the amplifier. Feedforward linearization is a technique commonly used in wireless base station applications, as it offers a wide bandwidth and excellent linearity correction. However, this linearization technique is expensive, complex, and very difficult to implement. This thesis presents a hybrid linearization technique that integrates DSP into the structure of the basic analog feedforward linearizer. This allows the implementation of equalizers to correct the frequency response of the components in the system. The novel linearizer maintains the excellent performance of feedforward, while overcoming many of its drawbacks. An experimental circuit is designed and tested to demonstrate the capabilities of the hybrid linearizer.
An image-reject low-noise amplifier with passive Qenhanced notch filters in 0.18µm CMOS is presented. Available IR-LNA designs employ a single notch filter to reject the precise image frequency and therefore require an additional automatic tuning circuit. This design achieves image-rejection over a bandwidth by using two seriesconnected passive notch filters, thereby relaxing the requirement of any additional tuning circuit. The proposed image-reject low noise amplifier has 16 dB gain at the signal frequency of 2.4 GHz and 58dB rejection over a bandwidth of 100MHz centered at the image frequency of 1.6 GHz. Noise Figure of 2.25dB and P1dB of -13dBm are obtained with bias current of 3.9mA drawn from a 1.5V power supply.
@Copyrlght 1980 Offshore Technology ConferenceThis paper was presented at the 12th Annual OTC In Houston, Tex" May 5·8, 1980. The matorlalls subJect to correction by the author. Permission to copy Is restricted to an abstract of not more than 300 words.
ABSTRACTA geotechnical and geophysical reconnaissance was performed in anticipation of offshore drilling and construction in the Orinoco River Delta, Venezuela. The survey results show that a major portion of the study area is covered by cohesive sediments with an intriguing range of properties. An examination of regional geologic history suggests that fluctuations in regional sea. level were probably the cause of sediment property variation.A relationship between undrained shear strength, water. content and liquid limit was developed, and the relationship is similar to relationships for the Mississippi Delta. The variation of liquid limit with plasticity index is expressed by a straight line relationship that is in good agreement with the data.The geotechnical and geophysical data were used for evaluating the following: anchor holding capacity, seafloor bearing capacity for guide bases, conductor pipe installation, and seafloor support of jack-up drilling rigs.
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