Mr. M. Abedi, Dr. J. Yavand Hasani,
Volume 14, Issue 2 (Vol.14 No.2 2017)
Abstract
In this paper, a dual loop PLL with short locking time, low power consumption and low reference spur is presented. The output frequency and reference frequency of the designed circuit are 3.2 GHz and 50 MHz, respectively, aimed to WiMAX applications. In the proposed circuit in locked state, some parts of the circuit could be powered off, to reduce overall power consumption. Phase detection in the circuit is based on Aperture Phase Detection (APD) method. In addition, the proposed charge pump reduces reference spur. The proposed structure of the frequency locked loop reduces the locking time. To evaluate the proposed approch, we simulated the designed PLL using the foundry design kit for 0.18μm CMOS technology. The spur level and lock time of the proposed circuit is -74dBc and 1.9 μs, respectively, implying 5dB improvement in spur level and 32% improvement in lock time compared with the previously proposed circuits. The power consumption of the proposed circuit is 4.15 mW.
Fardin Faraji, Dr. Javad Yavand Hasani,
Volume 19, Issue 2 (JIAEEE Vol.19 No.2 2022)
Abstract
SPDT switches are used as duplexer in wireless systems, as WIMAX, to switch between transmit and receive states. Microwave SPDT switches may be designed using FET’s or PIN diodes. However, PIN diode is suitable for duplexer applications due to its high power handling capability. I general, in frequencies higher than 3 GHz, isolation better than 30 dB is a challenge. This is due to the parasitic inductance of PIN diode.
In this paper, we propose a new structure for SDPT PIN diode switch to overcome this challenge. In the proposed structure a micro-strip line is adopted parallel to the diode. This line, in conjunction with another micro-strip line that is in series with the diode, eliminates the diode inductance in on-state and the diode capacitance in off-state, and hence improves both of isolation and insertion loss. The proposed structure has been analyzed mathematically and analytic equations have been derived to design the proposed switch. Finally, simulation results have been used to validate the performance of the switch. Simulations are performed using SMP1340 PIN diode and the model presented by the diode manufacturer. The simulations are in ADS and EM and EM_Cosim simulators are used to simulate the switch layout and include the layout effects accurately. Simulation results show more than 50dB isolation and less than 0.2dB insertion loss.
Farid Khamoii Toli, Dr. Javad Yavand Hasani,
Volume 19, Issue 2 (JIAEEE Vol.19 No.2 2022)
Abstract
High actuation voltage is one of the most important limitations of RF MEMS switches. One way to reduce the actuation voltage is to reduce the spring constant in the switch structure. In this paper, we model the spring constant using Energy Model and we obtain an analytic equation to calculate it. The result is an analytic design guide that determines the minimum value of the spring constant. Then, a new RF MEMS structure with very low actuation voltage is presented. The structure is modeled by the energy method and the spring constant is calculated analytically. Analysis results show the spring constant of 0.0714 N/m and an actuation voltage of 1.61 V. To evaluate the performance of the proposed structure and to validate the results of the analysis, a switch was designed using simulated COMSOL software. The results of this simulation show the actuation voltage of 1.8 volts, the switching time of 25.6 microseconds, the 4.5 MPa Von Mises stress, the natural frequency of 3118.6 Hz, its mass of 0.206 ng and finally the spring constant of 0.079 N/m. The beam is made of gold and Si3N4 is used as a dielectric. Finally, the high frequency performance of the switch is designed using simulated HFSS software. The simulation shows a 25 dB isolation, a 0.7 dB insertion loss, and a 16 dB return loss at 10 GHz.
