Measurement and Control of RF ...

Measurement and Control of RF Power_IMeasurement and Control of RF Power (Part I) By Eamon Nash Applications Engineer, Analog Devices, Inc. Introduction Fig. 1. shows a typical modern communications signal chain. The signal to be transmitted is generated at baseband by a digital-to-analog converter (DAC.) This signal is then mixed up to an intermediate frequency (IF) where it is filtered before being mixed up to the final radio frequency (RF.) On the receive side the inverse transformation takes place. The received signal is amplified, mixed down to IF and filtered before being mixed down to baseband where it is digitized.

MIXER LNA DIFF AM P

ADC VGA
0 90

ADC
IQ DEMODULATOR

VCO/SYNT

RSSI/PHASE DETECT

DAC
HIGH POWER AM P RF VG A MIXER IQ MODULATOR

VGA

Σ

0 90

DAC

PO WE R DE TE CT

POWER CONTROL

Fig. 1: A Modern RF S