Analog Circuit Design Volume Three

Chapter 492

A low power, direct-to-digital IF receiver with variable gain

Walter Strifler

Abstract

A variable gain amplifier plus analog-to-digital converter (VGA + ADC) combination circuit is described.

Keywords

IF receiver

LTC6412 VGA

LTC2261 14-bit ADC

Introduction

Modern communication receivers require an ADC to digitize an incoming analog signal for decoding in a suitable FPGA device. The direct-conversion method of receiver design typically performs a single frequency downconversion and an analog-to-digital conversion (ADC) near baseband. While elegant and simple, this receiver architecture has problems with in-band blockers, out-of-band interferers and LO leakage reflections within the receiver itself.

In the face of these ...