Imbalance-compensated direct down conversion receiver for UMTS base stations

In this work, a new method for the estimation and the compensation of in-phase quadrature-imbalances in direct down conversion receivers is presented. The considerations are based on a receiver structure that is developed for the simultaneous down conversion of up to four neighboring carriers in universal mobile telecommunications system base stations. The image suppression of the system must achieve at least 60 dB. This requirement is not fulfilled by the analogue part and hence, an error estimation and compensation in the digital domain is necessary. In laboratory measurements using a wideband code-division multiple-access signal, the image suppression of the complete set-up including the analogue parts could be improved by 34 dB.     

A dual-frequency Wilkinson power divider: for a frequency and its first harmonic

A Wilkinson power divider operating not only at one frequency f/sub 0/, but also at its first harmonic 2f/sub 0/ is presented. This power divider consists of two branches of impedance transformer, each of which consists of two sections of 1/6-wave transmission-line with different characteristic impedance. The two outputs are connected through a resistor, an inductor, and a capacitor. All the features of a conventional Wilkinson power divider, such as an equal power split, impedance matching at all ports, and a good isolation between the two output ports, can be fulfilled at f/sub 0/ and 2f/sub 0/, simultaneously.     

Improved four-channel direct-conversion SiGe receiver IC for UMTS base stations

This work presents the design and measurement results of an improved four-channel, direct down conversion receiver (DCR) for the application in universal mobile telecommunications system base stations. The whole analog receiver functionality including low noise amplifier, variable gain amplifier, local oscillator frequency divider, in-phase and quadrature DCR mixers and seventh-order active lowpass filter is integrated using Atmel's 50-GHz f/sub t/, 50-GHz f/sub max/ SiGe foundry technology (Atmel, 1998). Important cascaded design parameters of the fully ESD-protected device are a noise figure 1.5 to 2 dB; IIP3 (third-order intercept point) -20.3 to -15.8 dBm and a voltage gain of 51 to 57 dB into a 1000-/spl Omega/ /spl par/ 2.5-pF differential load [analog to digital converter].