Microwave Connector De-Embedding and Antenna Characterization

110 IEEE AntEnnAs & ProPAgAtIon MAgAzInE J U N E 2 0 1 8 1045-9243/18©2018IEEE T his article describes a systematic procedure for microwave connector de-embedding in a single-port antenna system. Coaxial connectors are a much-used medium to probe the electrical properties of radio-frequency (RF) components. However, connectors impact the magnitude and phase response of the device under test (DUT). Thus, it is essential to de-embed the connector properties to access the actual characteristics of the DUT. Various deembedding techniques reported in the literature considered the DUT as a twoport device. A detailed and accurate procedure for connector de-embedding in a single-port antenna system in the context of active antenna design is demonstrated in this article. For this purpose, a continuous two-port antenna model is derived, and the results of connector de-embedding are presented with active antenna examples. Such a de-embedding procedure is an essential step in active antenna system design. The proper connector de-embedding step increases the accuracy and overall performance of the active antenna system. ANTENNAS AS PART OF RF SYSTEMS Traditionally, antennas and RF frontend electronic systems are designed separately and cascaded assuming 50-Ω port impedance. But an antenna can also be designed as an integral part of RF systems serving more than simply a radiating element. For example, antenna integrated oscillators are reported in [1]–[3], where the antenna provides a feedback path and improves the phase noise characteristics (by the high selectivity nature of microstrip antennas) with a simple single-ended oscillating architecture. High-efficiency power amplifiers are reported in [4] and [5] where harmonic tuning is achieved by a dielectric resonator antenna and a microstrip antenna, respectively. On the other hand, interesting antenna characteristics are also achieved from integrated active antenna systems, such as antenna miniaturization [1], [6], bandwidth enhancement [7], [8], and improved radiation performance [9]. One of the initial steps in active antenna system implementation is to characterize the antenna for which measurement results are preferred to avoid discrepancy in the subsequent steps. Generally, coaxial connectors are used to probe the characteristics of the microwave components and circuits. It is important to remember that connectors affect both the magnitude and phase responses of the circuit unless their properties are de-embedded.