Bandwidth Tuning in Transistor Embedded Metamaterials Using Variable Resistance

Abstract

Abstract-Metamaterials have been previously loaded with diodes and other types of passive circuit elements. Transistors offer an alternative to these established loading elements to expand the possible capabilities of metamaterials. With embedded transistors, additional degrees of freedom are achieved and lay out the architecture for more complex electromagnetic metamaterial design. A mathematical analysis of transistor loaded SRR unit cells is described in which the transistor acts as a variable resistor. From the mathematical analysis, we calculate transmission coefficients for a single unit cell. We then experimentally measure two SRRs with tunable quality factors and thus tunable bandwidth based upon modulating the effective loading circuit resistance to confirm the calculations. From the agreement between the calculated and measured transmission coefficients, we expand the analysis to show that a slab of more densely packed unit cells can achieve negative permeability with varying degrees of dispersion.

Active Tunable THz Metamaterial Array Implemented in CMOS Technology

“…The inductance Lm stores the magnetic energy in the resonant frequency, and the impedance Rm describes the resistance of SRR. In fact, capacitance and inductance store the same energy in resonance, the expression can be further simplified according to this principle in Equation On the other hand, when the transistor is on, and Rt is lower than the capacitance impedance, the loss will be reduced, and the Q factor will increase again [40]. The curve of the Q changing with the resistance Rt is illustrated in Fig.…”

“…Embedding transistors [32,33,40] and other conventional integrated circuit process technologies [41] into metamaterials has been implemented in the microwave frequency band, and is beginning to expand to the THz region. Meanwhile, advanced complementary metaloxide-semiconductor (CMOS) technology has been used above 400 GHz for the oscillator [42] and imaging applications [9].…”

Active Tunable THz Metamaterial Array Implemented in CMOS Technology

“…3a depicts a complete circulating current, which proves that the SRR was operating in the LC resonant state at this frequency. The equivalent circuit model of the SRR embedded transistor [37] is given in the inset of Fig. 3b, 6 on which the accurate circuit parameters and relevant mathematical relations are determined.…”

“…The transistor can be seen as a parallel combination of total drain-to-source capacitance (Cds) and equivalent resistance (Rt) between source and drain. In the transistors, Cds can be calculated from the known structural capacitance of the transistor [37] as shown in Equation 2, and would not be significantly varied when Vgs was adjusted. ) in the THz range was close to Rt, either one of them was not negligible in the calculation.…”

Active tunable THz metamaterial array implemented in CMOS technology

“…Embedding transistors [32,33,37] and other conventional integrated circuit process technologies [38] into metamaterials has been implemented in the microwave frequency band, and is beginning to expand to the THz region. Meanwhile, advanced complementary metaloxide-semiconductor (CMOS) technology has been used above 400 GHz for the oscillator [39] and imaging applications [9].…”