A complex charge sampling scheme for complex IF receivers

A charge sampling technique for complex filtering and further quadrature downconversion of an I/Q downconverted IF signal is introduced. The presented technique can be applied to complex IF radio receivers for attenuating the image signal at the IF and for partial channel selection filtering. Circuit level simulations of a test circuit for complex filtering and quadrature downconversion of a 50 MHz I/Q IF signal are shown.

1. INTRODUCTION

The recent progress in wireless and telecommunication circuit markets has initiated a strong ongoing research work within radio receivers. The tendency is towards higher integration degree and smaller circuit area. Much of research effort has been put both to circuit level designing as well as to to system level designing, including development of new receiver architectures. Due to their improved suitability for integration, receiver architectures utilizing complex signal processing (I/Q) techniques have caught a lot of attention recently. As examples, receiver topogies such as the wideband-IF receiver [1] and the wideband-IF low-IF receiver [2] make use of quadrature downconversion to a high complex 1^st IF.