Microstrip quasi-horn antenna for UWB radars and sensors

A microstrip quasi-horn antenna for UWB radars and sensors has been developed. The antenna achieves good performance in both frequency domain for CW signals from 0.3-6 GHz and time domain for monocycle pulses of various durations. The time-domain measurement, particularly, shows that the antenna can transmit and receive monocycle pulses effectively with minimum distortion, little ringing, and small reflection, clearly demonstrating the signal fidelity of the antenna in reproducing the waveform of UWB signals which is critical for UWB radars and sensors. For time-domain applications, such as UWB radars which transmit and receive pulse signals, characterizing the antenna's transient responses directly is useful and important for accurate assessment of its signal fidelity and matching. The developed antenna employs non-uniform microstrip transmission line and has good linear phase, simple fabrication, and easy integration with microwave integrated circuits. It requires no transition or balun at its input, leading to wide bandwidths and high operating frequencies. The antenna has been successfully used in several UWB surface-penetrating radars.