Jingnan Pan

Radio-Frequency Interference Estimation Using Equivalent Dipole-Moment Models and Decomposition Method Based on Reciprocity

In modern electronic products, the noise from high-speed digital parts is likely to interfere with nearby receivers, causing radio-frequency interference (RFI) issues. In this paper, the equivalent dipole-moment models and a decomposition method based on reciprocity theory are proposed being used together to estimate the coupling from the noise source to the victim antennas. The dipole-moment models are extracted from the near fields of the noise source by solving the inverse problem. The tangential electromagnetic fields on a Huygenss surface, which enclose the victim antenna, can be calculated from these equivalent dipole-moment models. Then, the victim antenna only is treated as a radiator. The tangential electromagnetic fields from the radiating antenna on the same Huygenss surface can be obtained. With these two groups of the fields on the Huygenss surface, the reciprocity theory is applied to estimate the coupling from the noise source to the victim antenna. This method is validated by full-wave simulations and measurements of a simple printed circuit board. The proposed method provides convenience to estimate RFI issues in the early design stage and saves the time of RFI simulation and measurements.

Measurement validation of the dipole-moment model for IC radiated emissions

A procedure is proposed to extract equivalent dipole-moment model for the real integrated circuit (IC) from the near-field scanning data. The radiation fields from the extracted dipole-moment model match well with the measured ones in both near- and far-fields. Therefore, the dipole-moment model can be applied to take the place of real IC in the full-wave simulation tools, to predict the ICs radiated emissions with the presence of other structures. Radiation from a heat sink excited by the dipole-moment model of an IC has been simulated by HFSS. The simulated results were found to agree with those measured. Thus, the extraction procedure of dipole-moment models for IC radiation emission has been validated.

Far-Field Prediction by Only Magnetic Near Fields on a Simplified Huygens's Surface

For radiation source locating above a ground plane, its far field can be predicted by only the magnetic near field through the method proposed in this paper. This method applies the finite element method to get the equivalent current sources from the tangential magnetic near fields. With the equivalent current sources, the far-field radiation can be calculated based on Huygenss principle and image theory. The magnetic near field is scanned on a Huygenss surface that encloses the source with its ground. In this paper, this Huygenss surface was first proposed as a five-surface cube on the ground. Then, the Huygenss surface was further simplified by using four lines instead of four side walls to make the proposed method easier in regards to practical near-field scanning. Several numerical examples were tested to validate the proposed method. In addition, the proposed method was validated experimentally by using a patch antenna. The performance of using only the top plane near fields was also investigated and discussed. By using only the magnetic near fields on the simplified Huygenss surface, the proposed method significantly saves measurement time and cost while also retaining good far-field prediction.

Near-field coupling estimation by source reconstruction and Huygens's equivalence principle

This study is to estimate the near-field coupling in mixed digital/RF circuit design for modern high speed electronic systems. The noise source IC is first modelled by physics-based dipole moment model with data obtained from a near-field scanning plane. The victim RF antenna is modelled in full-wave simulation tool and the noise IC is further modelled as Huygenss equivalent source. The tangential fields on the Huygenss box can be calculated by dipole moment model with negligible multiple scattering effect assumption. The noise coupling then can be obtained by surface integration of Poynting vector at the RF antenna receiving port. A full-wave simulation model is first studied to demonstrate the method and a noisy clock buffer IC with victim patch antenna is measured for further validation.

Application of dipole-moment model in EMI estimation

This paper used magnetic near fields to extract the dipole-moment model to represent the real radiation source. This method prevents the measurement of electric fields so that the scanning time and points are saved significantly. These equivalent dipole-moment models can take the place of the real radiation source in the full-wave simulation tool. The electromagnetic interference between the real source and victim structures are well predicted in the simulation by the dipole-moment model. This is validated by a numerical example in this paper.

Measurement validation for radio-frequency interference estimation by reciprocity theorem

This paper presents the measurement validation of reciprocity theorem method for near-field coupling estimation. The overall problem is decomposed into two parts, the first part is called forward problem, and the second part is called the reverse problem. For forward problem, the noise source IC is modelled by physics-based dipole moment model with data obtained from a near-field scanning plane, then the tangential E and H fields on a Huygenss box enclosing the victim antenna are calculated by analytical expression. In reverse problem, the victim RF antenna is modelled in full-wave simulation tool and the tangential E and H field are obtained by simulation. With tangential E and H field obtained in forward problem and reverse problem, the coupled noise power is then estimated by reciprocity theorem. The estimated noise coupling power is compared with measured power at the victim antenna port with IC excited. The difference is within 5dB which is acceptable for engineering practice.

Investigation of interference in a mobile phone from a DC-to-DC converter

Turning on the LCD screen of a mobile phone causes desensitization of its receiver in the GSM lower frequency band (900 MHz). In this paper, the measurement techniques used for the investigation of intra-system interference in a mobile phone caused due to the DC-DC converters present on-chip the LCD driver IC are presented. An equivalent noise source model is created by modelling the flexible printed circuit board traces and obtaining a Thevenin equivalent noise by changing the load conditions.

Far-field radiation estimation from near-field measurements and image theory

This paper proposed a near-field to far-field transformation method for the radiation sources located on a large ground plane, based on the Huygenss principle and image theory. This method uses the tangential electromagnetic fields on a small near-field plane and the vertical electric fields, one tangential component (parallel to the ground plane) of magnetic fields around the near-field plane to extract the equivalent current sources. The far-field radiations are calculated from these equivalent sources and their images. The application of this method in several simulation models indicates that it has very good performance on both simple printed circuit boards and antenna radiation estimation. The method proposed in this paper can decrease the total scanning area in real measurements.

Radiation Noise Source Modeling and Application in Near-Field Coupling Estimation

Near-field coupling in mixed digital/RF circuit design is critical to system sensitivity for modern high speed electronic systems. This paper presents radiation noise source modeling methods and applies equivalent noise source models to near-field coupling estimations. The noise source can be either modeled by physics-based dipole moment model or Huygenss equivalent model with data obtained from near-field scanning. The fundamental principles of both methods are first studied by simulation. A clock buffer integrated circuit is first modeled as a dipole moment model. The tangential fields on Huygenss box can be calculated by a dipole moment model with negligible multiple scattering effect assumption. The noise coupling then can be obtained by surface integration of Poynting vector at the RF antenna receiving port by full-wave simulation.

Estimating the near field coupling from SMPS circuits to a nearby antenna using dipole moments

In this paper, the near field coupling from SMPS circuits to a nearby antenna is studied using dipole moments [1]. The dipole moments are extracted from scanned H fields on a plane above SMPS circuits, and then imported into an HFSS model to do full wave simulation. The simulated coupling matches well with direct measurement. Methods to resolve magnitude and phase of near fields of SMPS noise source are introduced. Error analysis is included in the end as well.