Wide-band high dynamic range variable passive intermodulation generator using fabric-over-foam gasket

Abstract

Accurate measurement of Radio Frequency (RF) component’s passive intermodulation (PIM) and systematic evaluation of PIM’s effect on mobile communication require flexible PIM generator. This work presents a wide-band high dynamic-range PIM generator using a fabric-over-foam (also known as RF Interference Shielding Gasket) as superstrate of low-PIM microstrip line (MS-line). An air gap of 1 mm introduced between the foam and the MS-line to ensure long-term repeatability by avoiding the nonlinearity that can be generated by the metal-to-metal contact. To make the PIM generator adjustable, the foam moved transversely over the MS-line. The size of the gasket selected in such a way that it slightly changes the S-parameters of the MS-line. Due to the variation of the exposure area of the foam (which is an electromagnetic magnetic material) to the electromagnetic (EM) field generated by the MS-line; the PIM level of the MS-line changes with the foam’s location. The minimum PIM level of the proposed generator determined by the PIM level of the MS-line, which is no more than -125dBm @2×43dBm. However, the maximum PIM level can be as high as -48dBm @2×43dBm, achieved by placing a gasket piece on the top of the MS-line. The proposed generator verified from 700MHz to 2.7GHz and all of the measurement results show its feasibility. Moreover, presented PIM generator can be used a single-port or two-port calibration device.