| The purpose of this work is to apply the concept of active integrated antennas to microwave receiver front-ends. More specifically, the dual-feed quasi-Yagi antenna is integrated with microwave circuitry to create a more compact front-end. Two designs are presented that utilize this approach.;The first design consists of subharmonic mixers integrated on each feed of the dual-feed antenna in order to form a quadrature direct conversion receiver. The antenna serves as a power splitter to separate the received RF signal into an I and Q channel. A C-band prototype is constructed, which is utilized to successfully downconvert and demodulate a QPSK signal. However, the radiation properties of the quasi-Yagi antenna in the dual-feed configuration render it unsuitable for the intended application as an I/Q receiver.;Instead, the dual-feed quasi-Yagi antenna is more suited for monopulse radar applications. Unique properties of the antenna allow sum and difference radiation patterns to be formed using one antenna, as opposed to traditional arrays. Based on this concept, a low-noise active integrated antenna is developed that consists of low-noise amplifiers (LNAs) integrated on each feed of the dual-feed quasi-Yagi antenna. By combining the outputs of the LNAs with an 180 deg. hybrid, both sum and difference patterns can be obtained. Again, a C-band prototype is constructed, and measured results presented. In addition, simulation and measurement methodologies for designing a low-noise active antenna are also explored. |
