Balanced and symmetric design of active composite right- / left-handed transmission line with gain

We present a balanced and symmetric design of microwave composite right- / left-handed active metamaterial transmission lines incorporating gain devices. Our results show that by inserting a Ge tunnel diode at the unit cell level, the negative phase constant (i.e., left-handedness) and gain (negative attenuation constant) can be obtained simultaneously. By considering the parasitic effects of the diode, balanced and symmetric responses are achieved over a significant bandwidth.