Application of high impedance antennas in low cost ISM wireless chips

In case of integrated digital radio chips devoted to low cost, licence free short range radio systems the necessary bill of material and the battery life are one of the most important issues. The targeted RF power level determines whether a low or a high Q output architecture (output driver stage+optional matching+antenna) gives better result. It is shown that in case of the most commonly used radiated power ranges (-20...+10 dBm) for this radios, the high impedance configuration is advantageous. The high Q configuration is applied in a general purpose 0.6um BiCMOS transmitter chip operating in the 315, 434, 868 and 915MHz bands. Novell printed high Q antenna topologies ad matching network are presented as well.