Kishore Rama Rao

A single-chip CMOS transceiver for 802.11a/b/g wireless LANs

A dual-band trimode radio fully compliant with the IEEE 802.11a, b, and g standards is implemented in a 0.18-/spl mu/m CMOS process and packaged in a 48-pin QFN package. The transceiver achieves a receiver noise figure of 4.9/5.6 dB for the 2.4-GHz/5-GHz bands, respectively, and a transmit error vector magnitude (EVM) of 2.5% for both bands. The transmit output power is digitally controlled, allowing per-packet power control as required by the forthcoming 802.11 h standard. A quadrature accuracy of 0.3/spl deg/ in phase and 0.05 dB in amplitude is achieved through careful analysis and design of the I/Q generation parts of the local oscillator. The local oscillators achieve a total integrated phase noise of better than -34 dBc. Compatibility with multiple baseband chips is ensured by flexible interfaces toward the A/D and D/A converters, as well as a calibration scheme not requiring any baseband support. The chip passes /spl plusmn/2 kV human body model ESD testing on all pins, including the RF pins. The total die area is 12 mm/sup 2/. The power consumption is 207 mW in the receive mode and 247 mW in the transmit mode using a 1.8-V supply.

A CMOS RF front-end for a multistandard WLAN receiver

This letter describes the design and performance of a dual band tri-mode receiver front-end compliant with the IEEE 802.11a, b, and g standards. The receiver front-end was built in a 0.18-/spl mu/m CMOS process and achieves a noise figure of 4.7 dB/5.1 dB for the 2.4-GHz/5-GHz bands, respectively. The receiver front-end provides a dual gain mode of 5 dB/30 dB with an IIP3 of -1dBm for the low gain mode. The front-end draws 25 mA/27 mA from a 1.8-V supply for the 2.4-GHz/5-GHz bands, respectively.

A new ultrawide-bandwidth dielectric-rod antenna for ground-penetrating radar applications

A new ultrawide-bandwidth dielectric-rod antenna is presented with its application in detecting shallow targets, such as antipersonnel (AP) mines. The lowest hybrid mode is launched and guided along a circular-dielectric waveguide. The end of the waveguide is tapered to a point where electromagnetic waves are radiated out with field behavior similar to that radiated from a Hertzian dipole in the forward direction. The low antenna clutter and weak antenna-ground interaction are two unique features. Its near-field radiation properties are investigated by directly probing the fields and by numerical simulation with a three-dimensional finite-difference time-domain technique. Both measurement and numerical simulation results are presented for the detection of buried AP mines using a prototype dielectric-rod antenna operated at a frequency range from 1 to 6 GHz.

A single chip CMOS transceiver for 802.11 a/b/g WLANs

A 0.18 /spl mu/m dual-band tri-mode CMOS radio, fully compliant with the IEEE 802.11 a/b/g standards, achieves a system noise figure of 5.2/5.6 dB (high gain), and an EVM of 2.7/3.0% for the 2.4/5 GHz bands, respectively. Die area is 12 mm/sup 2/, and power consumption is 200 mW in RX and 240 mW in TX using a 1.8 V supply.

A tapered-permittivity rod antenna for ground penetrating radar applications

A new dielectric rod antenna design modified from its previous version developed by Chen [IEEE Trans. Geosci. Remote Sens. (accepted for publication)] is presented. Such an antenna is useful in detecting small and shallow subsurface objects with excellent depth and spatial resolutions. These features make it useful in detecting small anti-personnel (AP) mines, pavement cracks and the surface layer. Broad bandwidth electromagnetic energy is fed into the rod from one end, guided along the rod and then radiated from the other end where the rod diameter is linearly tapered to a point. The tapered-permittivity design uses an additional permittivity taper to overcome the problem of a frequency-dependent pattern when high dielectric material is used for size reduction. This new design reduces the internal reflections at the tapered section and results in better efficiency and less antenna clutter.

Discretization errors in finite methods: issues and possible solutions

In this paper, we review many of the sources of discretization error when finite methods is applied to high frequency electromagnetic problems. A major source of error is the numerical dispersion error. This error is probably the most serious error for electrically large geometries, and we review past efforts to reduce this error. We also present a new edge-based finite difference method which offers several improvements to current finite difference. This new method has less numerical dispersion error and less errors due to material discontinuities than current finite difference methods. We compare its performance to vector finite elements and show its superior accuracy. Finally, we propose a new subgridding scheme to reduce discretization error which maintains second-order accuracy.

Modified ultrawide-bandwidth dielectric rod antenna for ground penetrating radar applications

An ultra-wide bandwidth (UWB) dielectric rod antenna modified from its previous version developed by Chen (1999) is presented. Such antenna is useful in detecting shallowly buried targets, such as anti-personnel (AP) mines. Broad bandwidth electromagnetic energy is launched, guided and radiated from a dielectric rod that has a constant cross- section area and low-loss permittivity except at the end where the permittivity is gradually reduced to match to that of free air. The electromagnetic waves radiated out from rod end have field behavior similar to that of a Hertzian dipole. The low antenna clutter and weak antenna-ground interaction are two unique features. Its near-field radiation properties are investigated using three-dimensional finite difference time domain (FDTD) simulation technique. Some measurement and numerical simulation results are also included.

A single chip radio transceiver for 802.11a/b/g WLAN in 0.18/spl mu/ CMOS

This paper presents design and performance of a single chip CMOS radio covering the Wi-Fi 802.11 a(5GHz) and 802.11 b(2.4GHz), and a draft version of the 802.11 g(2.4 GHz OFDM/CCK) wireless standard. The radio is based on a configurable and digitally programmable transceiver architecture and adopts a frequency plan that: a) avoids use of external image reject filters and b) allows design of integrated low phase noise frequency synthesizer, as required by 54Mb/s 64-QAM modulation, while maintaining low power consumption. The resulting solution achieves maximum hardware share as mixers, PLLs and analog baseband chains are shared amongst the three standards. It was implemented in 0.18/spl mu/ CMOS technology with a die size of 12 mm/sup 2/ in a 48-pin package.

Electromagnetic scattering characteristics of UXO and non-UXO objects in the presence of a water table

An investigation of the scattering characteristics of a typical UXO target versus similar non-UXO targets is done. This investigation will be done with a computer code based on the finite difference time domain (FDTD) method. Initially, comparisons are made based on targets in free space excited by a plane wave. Then more realistic features are systematically incorporated into the model to determine their effects on the scattering characteristics of the UXO. First, the plane wave excitation is replaced by a dipole. Next, the UXO is embedded in a lossy half space with realistic ground conductivity and permittivity parameters. Finally, a water table is placed underneath the UXO.

Numerical modeling of an ultra-wide bandwidth dielectric rod antenna for ground penetrating radar applications

Ground penetrating radars (GPRs) have been used extensively as a non-intrusive means for subsurface investigation. Low antenna clutter and weak antenna-ground interaction are desirable features for the detection of shallow mines. We present a finite difference time domain (FDTD) simulation of a wide band dielectric rod antenna with these desirable features. The FDTD was chosen because of its ability to handle inhomogeneous media and provide accurate results over a wide range of frequencies. The near field radiation properties of the antenna are investigated. The effectiveness of the above antenna in humanitarian demining applications is studied by analyzing the response from a position scan on anti-personal (AP) mines.