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A novel compact CPW-type magnetic loop probe (2.3times2.3 mm) is proposed. Unlike the conventional one[1], the new probe move the impedance-transition to the CPW line part, so that the new probe possesses the property of symmetry (to suppress the influence of induced magnetic field created by the probe) as well as inherits/enhances the ability to suppress the loop self resonance(up to 10 GHz). Based on this probe, a 2.5D automatic vector near-field measurement system is developed by using the automatic network analyzer (ANA) as the signal detector. In this preliminary study, the magnetic field distribution of a section of short-circuited microstrip line and a square-loop type resonator are scanned by the novel probe. For reference, the electric field measurement results and theoretical ones by 3D simulator are all given. The good comparison between the measured results with the reference data shows the good performance of this probe. In addition, an extended study on extracting the effective dielectric constant of the substrate by our probe is also included with the experimental validation.

A transmission-line-theory-based novel synthesis theory is proposed to design an ultra-wideband bandpass filter to meet Federal Communications Commission (FCC)'s spectrum limit. One-wavelength parallel coupled stepped-impedance resonators (SIRs) are used to achieve a fraction passband from 3.1 GHz to 10.6 GHz (greater than 100%). An unsymmetrical SIR is employed to replace the conventional centrally-symmetrical one, so that the coupling gap is successfully enlarged to alleviate the requirement on fabrication precision. A simpler equivalent circuit for the parallel coupled-line is used in this synthesis to avoid calculation of parameter J [7]. As an example, a filter with two-stages is synthesized, simulated and fabricated. The good agreement between the measured and predicted results validates the effectiveness of newly proposed synthesis theory. Meanwhile, the designed filter exhibits good characteristics of low insertion loss, sharp skirts, flat group delay and good stopband (especially in lower one) as well.