CMOS mixer design for cable modem RF tuner

An up-conversion mixer for RE tuner of cable modem has been designed in a standard 0.35 mu CMOS process. As an up converter, the mixer translates 40MHz to 900MHz input band to the Intermediate frequency of 1.2GHz. Overall conversion gain of 13dB, noise figure of 11.4dB, IIP3 of -11 dBm, 1 dB gain compression point of -17dBm for LO power of 4dBm is obtained and the circuit takes around 7mA from a 3.3 V supply. Simulations were done using cadence spectre RF. The design shows that mixer have comparable linearity with expected noise performance

Spectroscopy of silicon dioxide films grown under negative corona stress

Silicon dioxide films were grown in oxygen ambient under negative corona stress at low temperatures (400-450 degreesC). Fourier transform infrared spectra of these films show a peak at 935 cm(-1) along with the conventional transverse optic mode peaks around 1074, 800, and 456 cm(-1). A broad shoulder at 1150 cm(-1) was also observed. The extra peak is attributed to the presence of SiO42- ions and could be the outcome of incomplete oxidation at the surface. The films indicated properties similar to a fully relaxed thermally grown silicon dioxide film with a contradictory nature. The results of these experiments can be comprehensively explained only by assuming the presence of some mixed phase of SiO2. (C) 200

Optically tunable spiral inductor for RIF applications

The inductors are found in impedance matching networks, filters, tuned amplifiers and voltage controlled oscillators. The performance of these circuits is heavily depends on these passive components. Many researchers are working on improving the performance of passive components in particular inductors. A novel method of implementing the tunability in inductor is proposed. Tunability in this passive component gives better performance of RF front end circuits by adjusting the centre frequency of band pass filter. This work is based on improving the mutual impedance by increasing the length of the additional conductor without effecting the overall spiral length by optical switching. This method does not increase the resistance of the spiral inductor as we are not increasing the physical length of the spiral, but we are increasing the coupling

E-beam deposited SnO2Pt-SnO2 and Pd-SnO2 thin films for LPG detection

The electron-beam evaporation method was used to deposit undoped and Pt (or Pd) doped SnO2 thin films. After careful study of their physical properties, SnO2 thin films with suitable growth conditions were selected for probing their response to LPG and other common household gases. The response behaviour is explained with the help of theoretical models. Based on these results, the optimum parameters for film growth and sensor operation were identified for LP gas detection. (C) 1999 Elsevier Science S.A.

Study of Ta2O5 based MOS capacitors, with tantalum oxidized in O-2 : NH3 ambient

Tantalum Pentaoxide, an alternative to SiO2, as a high-k dielectric for DRAM and MOS applications, faces the problem of interface mismatch at silicon. SiO2 or Si3N4 interfacial layer could help in overcoming this problem. The higher band offsets of these materials also help in the reduction of leakage currents at low electric fields. Here we study the physical and electrical characteristics of Ta, oxidized in O-2:NH3 ambient, and without any other interface layer. This is done to check if N/H moves to the interface, and thus improves the electrical properties. XRD studies of the film, showed the presence of Ta2O5. Peaks corresponding to TaSi2, un-oxidized tantalum and TaN were also found in the film. But the intensity of these peaks decreased with the reduction of NH3 content. Thus a higher oxygen content could reduce the content of TaN and unoxidized tantalum. FTIR analysis however showed strong Ta=O and Si-O peaks. For the MOS capacitors, due to the presence of resistive components, the maximum capacitance was reduced, compared to that of pure Ta2O5 films. Oxide charges in the films were observed to be around 1.9E10 cm(-2). But the traps in these films were found to be almost negligible as observed from the negligible hysteresis in the C-V characteristics. Films with N/H showed lesser oxide charges by an order of magnitude, as compared to pure Ta2O5 films

Growth and study of high-k Ta2O5 films deposited by Ta sputtering followed by its thermal oxidation

For large-scale integration of devices, due to the problems associated with very thin layers of SiO2, a high-k dielectric becomes a necessity. In this work, Ta2O5 as a high-k dielectric in MOS device is studied. The deposition of Tantalum Pentoxide was carried out by thermal oxidation of sputtered Ta. Ta2O5 was directly deposited on silicon, without any buffer layer and its physical and electrical characteristics have been reported

EFFECT OF ANNEALING ON THE SURFACE AND INTERFACE PROPERTIES OF INDIUM OXIDE SILICON STRUCTURES

Indium-indium oxide films were formed by vacuum evaporation of elemental indium onto Si/SiO2 substrates. It is shown that the oxidation of indium takes place at the substrate. The surface and structure of the film were investigated using X-ray diffraction and scanning electron microscopy. X-ray photoelectron spectroscopy and electrical (capacitance-voltage) characterization were used to study the effect of annealing on the interface. Temperature studies of this system indicate the growth of an interfacial insulating layer. This layer was identified as an oxide of silicon. This study is significant for understanding the behavior of In2O3/Si structures used in a variety of applications such as silicon doping with indium and sensor fabrication using an evaporated indium film

Optically controlled microwave phase shifter using Mach-Zehnder interferometer geometry

A new type of optically controlled microwave phase shifter is proposed here. The phase shifter employs the Mach-Zehnder interferometer in a microstrip form on a semiconducting: substrate. One of the arms of the interferometer hus an optically excited gap. The gap is modeled hv a variable series impedance. A general analysis of the phase shifter is presented. Results show that the phase shifter can be realized at microwave frequencies on silicon substrate. and phase shifts from 0 to 90 degrees can be obtained with optical power less than 100 mW. (C) 2001 , Inc