Combined LNA and mixer circuits for 2.4 GHz ISM band

We present a combined LNA-mixer circuit with low area and low power, for the 2.4 GHz ISM band. The circuit has two versions: one has an output RC low-pass filter suitable for low IF frequencies; the other has an output LC band-pass filter suitable for medium IF frequencies. Circuits, with IF of 50 MHz and 400 MHz, were designed using UMC 0.13 mum CMOS technology and 1.2 V supply, and dissipate approximately 7.6 mW.

I. Introduction

Conventional receiver architectures use independent blocks: a single narrowband low noise amplifier (LNA), a mixer, and an oscillator within a PLL [1], [2]. These blocks were originally designed independently because other blocks (mainly filters) were necessary between them. Impedance matching was required at all ports because filters could not be integrated, and non-integrated long connections were required. This leads to signal power waste and to complex circuits. Nowadays, with full system integration, long connections between blocks are unnecessary, and so impedance matching is not required.