Prakash Easwaran

A current mode 2.4 GHz direct conversion receiver

A novel direct-conversion RF architecture is proposed that has a current mode interface between the low noise amplifier (LNA) and the down-conversion mixer, as well as the mixer and the base-band filter. The proposed architecture eliminates the voltage swing at the output of all the radiofrequency blocks. The voltage swing is seen only in the baseband after second order filtering, thus resulting in significant linearity improvements and robustness to adjacent channel interference. The current mode interface between filter and mixer also eliminates a redundant voltage-current conversion, giving significant noise advantages. A prototype wireless local area network (WLAN) receiver was designed and simulated in 0.13 /spl mu/m technology, giving a third-order input-referred intercept point of 5 dBm and a noise figure of 2.7 dB for the receive chain. The circuit (including base-band) consumes 8 mA from a 1.2 V supply.

Specification Driven Design of Phase Locked Loops

The factors that impact the topology and the performance specifications for a Phase locked loop (PLL) is presented. Correct specification of the PLL is critical for optimizing the performance and power of the system. PLL specifications for different systems have been derived and the architectural tradeoffs have been discussed. Three PLL design examples have been presented for WLAN base-bandPLL application, DVB-H receiver base-band PLL application and a high speed (MIPI) transmitter application.

Single amplifier bi-quadratic filter topologies in transimpedance configuration

Active-RC configurations, implemented as cascaded bi-quadratic sections (biquads), are the filters of choice for low distortion applications in the base-band. For low power and area applications, single amplifier biquads are best, and are well studied in literature. However, in many applications the input signal is in current domain while the output is a voltage. Output of a current steering digital-analog converter, and output of a down-conversion mixer, are two such examples. In this paper, the authors propose two generic classes of single amplifier bi-quadratic low-pass filter topologies, achieving a second order roll-off in transimpedance (-to-) configuration. Both these topologies are derived with the constraint of fully differential signal processing. The transimpedance active-RC configurations presented here eliminate redundant current-voltage-current conversion and hence provide immense advantages in terms of noise and linearity.