Metamaterial-inspired miniaturized microwave sensing probes

A Compact High-Resolution Resonance-Based Capacitive Sensor for Defects Detection on PCBAs

“…For the existing E-field-based near-field RF NDE methods in the literature, for the methods using open-ended coaxial probing technique [14]- [17], the spatial resolution lies in the range from a few millimetres to a few centimetres, which is relatively large. While for the methods using cavity resonance technique [18], [19], SRRs [13], [20], [21], and open-ended waveguide slit [22], [23], the spatial resolution could be high but the cost will increase due to higher working frequency, complex fabrication process or measurement setup. For the H-field-based RF NDE methods mentioned in [24]- [29], recent progresses from [26], [28] could detect single thin crack with width equals to 0.1 mm on a bare metal plate, but the sensor size falls in the range of more than few millimeters, which means the spatial resolution is not enough to distinguish errors in the complex PCBA environment.…”

“…However, the sharpen tip is sensitive to vibration and thus a sophisticated anti-vibration system is needed for the measurement, which dramatically increases both the complexity and the cost of the measurement. Recently, split-ring resonators (SRRs) have been applied for near-field sensing [13], [20], [21]. The sensing is conducted through the strong electrical field at the slit of the ring where the size of the slit decides the spatial resolution of sensing.…”

“…The sensing is conducted through the strong electrical field at the slit of the ring where the size of the slit decides the spatial resolution of sensing. A DUT placed near the slit changes the resonant frequency due to its electrical properties, thus the electrical properties can be deduced from the measured shifted of resonant frequencies [13], [20], [21]. For a high spatial resolution, the size of the SRR has to be reduced, which increases the resonant frequency and subsequently the cost of the driving circuit.…”

Non-destructive evaluation of pipes by microwave techniques and artificial neural networks

“…This approach was found to be advantageous regarding manufacturing difficulty, resolution, and reconstruction complexity [4,28]. Split-ring resonators (SRRs) and their complementary counterparts (CSRRs), as near-field microwave sensors, have recently gained wide attention [2,[29][30][31][32]. Due to their cost-effectiveness, miniaturization, and label-free detection, SRRs and CSRRs can be employed in electrically small resonant structures for dielectric sensing and imaging of test specimens [26,33,34].…”

An Aligned-Gap and Centered-Gap Rectangular Multiple Split Ring Resonator for Dielectric Sensing Applications

“…Wiwatcharagoses et al [ 13 ] had introduced a modified split ring resonator to be implemented in near field sensing of dielectric materials. The sensor consists of a microstrip line loaded with circular SRRs on both sides that are directly connected to the edge of the line.…”