This paper gives an overview of the recent developments in using near-field scanning for proactive EMC work. The aim is to use measured near fields as a source for simulations in order to predict radiated emission from printed circuit boards placed in a product. Far fields were predicted based on only H-fields on the top and bottom surface on a Huygens' box surrounding the board. Simulation of a simple board with microstrips and measurements of a complicated signal board were used to evaluate the proposed method.

Recent developments in using measured sources in computational EMC

The invention relates to a photoelectric electric field near field probe manufactured by using a printed circuit board and relates to a measuring probe for measuring an electromagnetic variable. The photoelectric electric field near field probe comprises an adjustable power supply, a cable, a laser, a black skin optical cable, a fixing hole, a silicon photocell array, a microstrip gap structure, a signal output terminal, a signal line shield, a band-shaped line, a copper-clad ground, a compensation capacitor, and a current-limiting resistor. The photoelectric electric field near field probe is a micro receiving antenna manufactured by using the printed circuit board and provided with the band-shaped line and the microstrip gap structure. The capacitor parameter of a probe circuit is adjusted by a power-adjustable laser so that a defect is overcome that a conventional electric field near field probe is susceptible to interference, narrow in frequency measurement range, and large in size.

Photoelectric electric field near field probe manufactured by using printed circuit board

This thesis reports high-fidelity near-field spatial microwave addressing of long-lived 43Ca+ "atomic clock" qubits performed in a two-zone single-layer surface-electrode ion trap. Addressing is implemented by using two of the trap's integrated microwave electrodes, one in each zone, to drive single-qubit rotations in the zone we choose to address whilst interferometrically cancelling the microwave field at the neighbour (non-addressed) zone. Using this field-nulling scheme, we measure a Rabi frequency ratio between addressed and non-addressed zones of up to 1400, from which we calculate an addressing error (or a spin-flip probability on the qubit transition) of 1e-6. Off-resonant excitation out of the qubit state is a more significant source of error in this experiment, but we also demonstrate polarisation control of the microwave field at an error level of 2e-5, which, if combined with individual-ion addressing, would be sufficient to suppress off-resonant excitation errors to the 1e-9 level. Further, this thesis presents preliminary results obtained with a micron-scale coupled-microstrip differential antenna probe that can be scanned over an ion-trap chip to map microwave magnetic near fields. The probe is designed to enable the measurement of fields at tens of microns above electrode surfaces and to act as an effective characterisation tool, speeding up design-fabrication-characterisation cycles in the production of new prototype microwave ion-trap chips. Finally, a new multi-layer design for an ion-trap chip which displays, in simulations, a 100-fold improvement in addressing performance, is presented. The chip electrode structure is designed to use the cancelling effect of microwave return currents to produce Rabi frequency ratios of order 1000 between trap zones using a single microwave electrode (i.e. without the need for nulling fields). If realised, this chip could be used to drive individually addressed single-qubit operations on arrays of memory qubits in parallel and with high fidelity.

Near-field microwave addressing of trapped-ion qubits for scalable quantum computation

A novel ultra-wide band wireless probe applied to near-field electromagnetic measurement is presented in this paper, in which the probe is built on an FR-4 substrate with three layers. This paper presents both simulation and measurement study of the probe performance affected by various factors including the vias influence and terminal soldering. A temperature compensation circuit is designed to deal with the influence of temperature variation of the printed circuit board substrate. To assess the effectiveness of the proposed probe, the return loss, gain, and radiation pattern are simulated and experimentally tested. Both simulation and measurement demonstrate that the probe working frequency ranges from 3.1 to 10.6 GHz and the gain is greater than −50 dBm. Moreover, the tested results show that the probe has good stability in terms of temperature, and that it is suitable for the electromagnetic interference (EMI) near-field measurement.

Investigation of Multilayer Print Circuit Board Probe With Temperature Compensation for Ultra-Wideband Near-Field Measurement

The accurate measurement of near-field EMI of Printed circuit board (PCB) and electronic equipment is essential nowadays. The photoelectric type probe could provide a better solution to the near-field measurement. In this paper, a combined with copper-clad laminate and electron component, the strip line embedded into PCB basal lamina is designed to get a specific frequency response. However, in consideration of the spatial electro-magnetic disturbance and the high-frequency harmonic jamming from the power supply to the probe, a photoelectric type power supply is proposed to make the power tunable. a structure of the strip line is simulated and analyzed. By changing the value of the patch capacitance between the strip line and the copper-clad laminate, three fixed resonance frequency points are located at 327.046MHz, 1.699GHz and 2.439GHz. The probe proposed in this paper can be widely used in near-field EMI testing.

A photoelectric type tunable frequency probe for near-field EMI measurement

We present an automated near-field scanner for system- to chip-level EMC/EMI evaluations in the RF domain. The scanning system combines a large scanning volume of 500×500×100mm3 with micrometre resolution. A novel optical surface reconstruction system allows measurement of the height map of the device under (DUT) test with better than 20μm uncertainty. This allows scanning at a precise distance above arbitrary electronic components. Key components of the scanning system are novel active miniaturized electro-optical time-domain E- and H-field sensors in the frequency range from 0.01 to >6GHz measuring the complex amplitude with a dynamic range of >120dB. The full optical isolation of the probes eliminates disturbance of the field of the DUT compared to electrically connected probes and offers up to 60dB better sensitivity than passive electro-optical probes.

E. Grobelaar

Papers

Automated near-field EMC/EMI scanning system with active electro-optical field probes