simulated frequency responses between the proposed and the conventional dual-mode DGW resonator filter. The resonant frequency of the DGW resonator can be reduced by the loading element by about 48%.Charge distributions of this designed DGW resonator are shown in Figure 3. It is interestingly found that the high-density distributions are located on the corners of resonator. Also, the phase difference of the high-density distributions between two degenerate modes is about 90 . The fabricated filter is given in Figure 4. A comparison between the simulated and measured frequency responses is described in Figure 5. Results show that the proposed filter has a fraction bandwidth of 4.6% at central frequency of 1.30 GHz, and its insertion loss in passband is less than 2 dB. There are two transmission zeros on the sides of the passband. They are À48 and À34 dB at frequencies of 1.21 and 1.42 GHz, respectively. They are close to the passband edges and can greatly improve the selectivity and stopband suppression of the proposed filter. Measured results agree well with the simulated ones and prove the validity of the introduced design principles to produce the dual-mode characteristics. Some discrepancy can be attributed to the inaccuracy in fabrication and implementation.
CONCLUSIONS
This paper presents CMOS radio frequency (RF) rectifier circuit design for radio frequency identification (RFID) tag with integrated on‐chip antenna. The proposed design focuses on high sensitivity and high efficiency at low input power. The rectifier circuit was designed using Advanced Design System (ADS) software tool with the UMC130 process as a single‐ended rectifier structure in different topologies where sensitivity and efficiency enhancement techniques are applied. This work presents the performance of the proposed CMOS RF rectifier circuit in comparison with previously published works for 915 MHz and 5.8 GHz operating frequencies. For the 915 MHz band, the highest sensitivity of −19.8 dBm is provided by the adaptive threshold voltage compensation circuit with a power conversion efficiency of 9.843%. The 5.8 GHz band uses the adaptive threshold voltage compensation and dynamic bulk bias techniques providing the highest sensitivity of −16.8 dBm. Compared with other works in the literature, the proposed circuits offer greater sensitivity and can easily be matched with ultrasmall on‐chip antennas because of appropriate values of the input impedance.
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