This paper aims to produce a high data capacity and miniaturized flexible chipless RFID tag based on the frequency signature using the Modified Complementary Split Ring Resonator (MCSRR). The proposed 19 bits chipless RFID tag using the frequency shifting technique consists of five slotted overlaying MCSRR with Different Width (MCSRR with DW) structures and the dimension of 48 mm $\times48$ mm. The structure is designed by using a flexible (Polyethylene Terephthalate ) PET substrate with permittivity of 0.2. The operating frequency is between 0.9 GHz and 2.7 GHz. The advancement of slotted overlaying MCSRR with DW structures has successfully miniaturized the chipless RFID tag structure to about $107~{\mathrm {mm}}^{2}$ / bit, $0.02\lambda _{mid}^{2}/\mathrm {bit}$ and 0.09 GHz/bit by maximizing the number of resonators in a limited space and minimizing the frequency separation between the resonators. The omnidirectional tag antenna is incorporated with the proposed MCSRR structure using the retransmission measurement method. The log-periodic antenna with a gain of 5–7 dBi is used for this measurement to improve the range distance between tag and reader system. Based on the retransmission measurement involving the antenna tag, the 19 bits chipless RFID tag which consists of five MCSRR with DW structures can be detected with a maximum range distance of 30 cm and a power transmitted level of 30 dBm.

Frequency reconfigurable antennas gain interest especially in future wireless communication systems due to flexibility in many applications. This paper reviews three different configurations of frequency reconfigurable antenna. The first configuration is the narrowband to narrowband frequency reconfigurable using slot type of antenna and microstrip antenna. The second configuration is the wideband to narrowband frequency reconfigurable antenna, planar monopole contribute to the wideband characteristic while a slot antenna is for narrowband. The third configuration used tunable electromagnetic band-gap (EBG) to configure the band notched frequency. The designed structures simulated performances and analysis are discussed in this paper. The analysis is also focused on the performance of the diode as a switch to reconfigure the frequencies.