Wideband and Multiband Metamaterial Based Microwave Passive Components

Abstract

Miniaturized wideband, multi-functional and reconfigurable 180° hybrid couplers realized in inexpensive printed circuit board technology have been developed. Bandwidth is enhanced by replacing some of the conventional transmission lines of ring hybrid by lefthanded transmission lines. Miniaturization is achieved as a result of the slow-wave effect introduced by right-handed and left-handed artificial transmission lines. Three couplers were designed namely wideband coupler, frequency reconfigurable coupler, and fixedlayout reconfigurable coupler. The technique proposed by Caloz et al. is used to design a wideband hybrid that exhibits 60% bandwidth enhancement at 1.5 GHz, with relative size reduction of 32%. A frequency agile coupler operating at three frequency bands centered at 0.9 GHz, 1.5GHz, and 2 GHz, and covering many commercial and industrial standards has also been developed. Although frequency selection can be operated by CMOS switches and controlled by 1-bit signal for inserting or removing unit cells to achieve the desired electrical length of the branches of the ring coupler, however in our realization, three separate circuits are designed to implement different switching conditions. The insertion losses of the switches were ignored. The bandwidth of the coupler in each frequency band is large leading to a wide operating range of coupler. Also, the physical size of the coupler is significantly reduced with respect to the standard realization at the same frequencies, with relative area of about 3.6% at 900 MHz, 7.7% at 1.5GHz, and 13.8% at 2 GHz. The design is validated by a full-wave electromagnetic simulator. Furthermore, a novel fixed layout reconfigurable coupler is also proposed wherein frequency, power division ratio, and topology of the coupler is reconfigured by changing the values of lumped components used to implement LH and RH artificial TLs while the layout of the circuit remains same. Two circuits were designed and fabricated operating at frequencies of 0.9 GHz and 1.5 GHz having coupling coefficients of 3 dB and 6 dB respectively. The measured results are in good agreement with simulated ones. Moreover, the dimensions of the couplers are also significantly reduced to 3.5% and 9.7% respectively