Contents I. Introduction
Nowdays, the millimeter wave wideband radar system has great advantages in many applications, such as automotive imaging [1], [2], electronic countermeasure (ECM) [3], [4] and the through-the-wall surveillance [5]. In one hand, the advanced millimeter wave (mmW) technology contributes a lot to the reduction of the size and weight of the active circuits and antenna, in another hand, the wider bandwidth can provide high probability for radar to successfully detect and jam more enemy targets in different frequency bands, and also greatly improve range resolution that allows for the discrimination of the close targets. But due to the dc-offset effect and the leakage of local signal (LO), the homodyne architecture is not fit for the short range application [6], [7]. To address the issue, the heterodyne architecture is widely implemented in a radar system [7], [8]. Accordingly, a variety of internal core components have gained a great deal of research and design including transmit/receive (T/R) modules, antennas and transceivers [9]–[11]. In [9], a dual channels transmit/receive (T/R) module covering 3 to 6 GHz is designed. In [10], a class of broadband mm-wave printed antennas operating over the entire Ka band is described for multiple mm-wave radio service application. And the system architecture, modeling, and design constraints for an ultra-wideband transceiver with very low power consumption are presented in [11].
