Contents I. Introduction
With the increasing power consumption of electronic devices, the decreasing physical size, and the decreasing radiation of some electronic devices, better requirements are put forward for the sensitivity of probes [1], [2], [3], [4]. As a key parameter of near-field probes, sensitivity has attracted the attention of many experts and scholars. Recently, using active circuits to amplify the induced voltage of magnetic field probes is considered a good design method. Therefore, many engineers usually use magnetic field probes connected to amplifiers to enhance their sensitivity. An integrated active magnetic probe array is designed by using SOI-CMOS technology to improve the sensitivity of magnetic field probes [5]. Since then, many active magnetic field probes [6], [7] have been designed and developed for weak magnetic field interference detection. However, these probes are all based on CMOS circuit technology, which is expensive and complicated. Nowadays, based on printed circuit board (PCB) manufacturing technology, several new designs have been introduced into the electric and magnetic field probes in [8], [9], [10], [11], and [12], which can significantly enhance detection signals by loading them at the end of the detection loop. In addition, some resonant circuits and impedance-matching techniques are also used to achieve high-sensitivity near-field probes at specific test frequencies [13], [14]. An electric field resonant probe with high sensitivity for electromagnetic emission near-field testing in narrow frequency bands is designed in [13], which is based on transmission line resonators and cascaded 1/4 wavelength transformers. In addition, based on low-temperature fired ceramics technology, shielded coil loops and via arrays are used to suppress common-mode electric field coupling and improve the common-mode rejection ratio of magnetic field probes [15]. Two parallel C-type striplines are also embedded into the front end of the magnetic field probe loop to form a common mode high-pass notch filter to suppress common mode electric field coupling and improve magnetic field probes’ rejection of common mode electric field noise [16]. Different from the C-type striplines as part of a high-pass notch filter, multiple parasitic loops, which can receive more electromagnetic energy and significantly enhance the detection sensitivity, have been massively used in the design of the magnetic field probes in [17], [18], [19], and [20]. Although these magnetic field probes have high detection sensitivity, they can only measure a magnetic field component, which will not be suitable for testing multiple components of radiation sources. Recently, in order to improve the testing efficiency of electromagnetic interference (EMI), multiple-component probes with high detection sensitivity have been studied in [21], [22], [23], and [24]. Note that these parasitic loops in the multiple-component probes are connected in parallel, which will result in lower sensitivity of the probe at low frequencies and higher sensitivity at high frequencies. Thus, it is urgent to develop a new multiple-component probe with high detection sensitivity at low frequencies.
