An Effective Method of Probe Calibration in Phase-Resolved Near-Field Scanning for EMI Application

Abstract

Near-field scanning can be used to determine the far-field emissions of electronic devices. In general, this requires phase-resolved electric and magnetic near-field data. To capture a broad frequency range relatively quickly, a multichannel oscilloscope can be used for data capture. The phase relationship of the fields between different space points and between the electric and the magnetic field needs to be known. Consequently, it is required to determine the complex-valued probe factor (PF) of the probe, cable, and amplifier chain. This paper presents a fast and efficient calibration method which uses the same setup and instruments during calibration and measurement, and it allows for easy and economical integration of the calibration hardware and software into the scanning system. Known fields are created by a microstrip trace driven with a comb generator. By referencing measured data to this known field, the PF is obtained over a broad frequency range by capturing one time-domain waveform.

A simple estimation of TRP and radiation pattern for mobile antennas using planar near-field scanning method

“…However, the phase-retrieval techniques are based on minimizing nonlinear inverse problems, which usually require complicated numerical treatment and may also suffer from ill-posedness of the measured data. Several techniques have been introduced to obtain the phase information directly from the near-field scanning measurement, [6,7]. According to the measurement equipment, these techniques can be divided into the frequency-domain and the time-domain measurements.…”

“…In this study, the time-domain measurement is employed to obtain the phase information. The time-domain measurement has several advantages compared with the frequency-domain measurements [7]. First, the phase information is accessible using relatively inexpensive equipment (i.e., oscilloscope) without an expensive instrument (i.e., VNA with specific functions) or a complicated measurement procedure (i.e., three times of sweeping with a spectrum analyzer).…”

“…With rapid development of wireless communications for the Internet of Things (IoT), RF integrated circuits (ICs) with compact chip size have become essential to reduce the unit cost of production [1][2][3][4][5][6][7][8]. To realize compact chip area, a power amplifier should be designed using a CMOS process by which the analog and digital circuits are integrated [9][10][11][12][13].…”

The impact of near-field scanning size on the accuracy of far-field estimation

“…x y k k  can be related by the following equations: Once the spectrum of tangential electric fields has been obtained with (6) and (7), the far-fields can be calculated by (1), which has been further simplified by the stationary phase method as [5],…”

“…The far-field measurement system is often an anechoic chamber with receiving antenna placed in the far field of the device under test (DUT). By making near-field measurements with well-calibrated field probes [1] and then using analytical transformation to compute far-field radiation characteristics, the complexity and cost can be significantly reduced [2].…”