AbstractIn this study, a novel compact chipless RFID transponder is presented. The coding information is based on spectral signature using three types of multiresonator: spiral, slot, and U‐shaped defected ground structure (DGS). Each resonator can be seen as a band‐stop filter which contributes to a particular resonance frequency. The previous spiral resonator based barcodes have only 1 bit information on each resonator which result in a large quantity of resonators relatively and a long microstrip line. In our design, the slot is cutting on the spiral resonator so more bits can be stored. The combination of slot and spiral resonators together provides an efficient decrease in resonator numbers. The DGS structure takes use of ground plane of the tag which further increases the capacity without expanding the size. The method of using these three types of resonators presents a clear improvement in miniaturizing the transponder which leads to a compact size of the tag. By applying frequency shift coding (FSC) coding technique, a coding density of 0.946 bit/cm2 is achieved. Improvement in two cross‐polarized transmitting and receiving antennas is also considered in the design. Corresponding experiments on realized prototypes are provided to validate the effectiveness of the proposed design.