A Broadband Active Dual Probe by Asymmetric Calibration Method

The frequency response and sensitivity of a near-field probe can be improved by using a low-noise amplifier (LNA). In this communication, a broadband active dual probe with two LNAs is proposed as a high-performance near-field detection tool for the first time. For broadband passive dual probe, a strictly symmetric structure is required. However, the symmetry of the active dual probe is difficult to achieve due to many factors, such as redundant transmission structure and asymmetric LNA chip. Therefore, an asymmetric calibration method (ACM) is adopted to eliminate the effects of the asymmetric structure, which can broaden the operating frequency of the active dual probe. Besides, a characterization method of sensitivity for the active dual probe is presented with an independent source. By analyzing the relationship between the transfer matrix and the physical size (or time delay) of the asymmetric structure, the calibration results of the active probe by using the ACM have been verified. Meanwhile, the sensitivity of this active dual probe is also verified by comparing the calculation and measurement results. Furthermore, by measuring a standing wave, the proposed active probe is broadened to 12 GHz by the ACM.