A tunable asymmetric coplanar waveguide (CPW)-type antenna using the 0th order resonance is presented in this paper. The reduction in antenna size is achieved by exploiting the unique zeroth-order resonant (ZOR) property. In order to electronically tune the operating frequency, the varactor diodes are inserted between the shunt chip inductor and ground in the CPW configuration. In addition, a bias network is realised to isolate the antenna from the bias line. By adjusting the reverse bias voltage, the shunt reactance is continuously varied, so that the resonant frequency is tuned. This proposed antenna is electronically tunable from 2.19 GHz to 2.51 GHz. Moreover, good impedance matching is achieved over the desired frequency range.