A new wireless tag design for a precise ranging system is presented. The proposed approach, based on a SAW delay line, is optimized for very low-power operation and low-cost manufacturing without compromising the measurement accuracy. Furthermore, the tag architecture allows the simultaneous use of the 2.4 GHz and the 5.8 GHz ISM bands, which may be used to improve the measurement resolution and accuracy in harsh multipath environments. A new calibration concept is introduced as well, allowing the online compensation of measurement offsets with a minor modification of the ranging system. Although On-Off-Keying (OOK) modulated PN-sequences were used for the first evaluation, the modular system architecture makes it a suitable platform for the exploration of multiple waveforms for ranging and communications.