Young-hwan Yun

Effects of on-chip and off-chip decoupling capacitors on electromagnetic radiated emission

Recently, electromagnetic interference (EMI) and radiated emission has become a major problem for high-speed circuit and package designers, and it is likely to become even severe in the future. However, until recently, designers of integrated circuit and package did not give much consideration to electromagnetic radiated emission and interference in their designs. Decoupling capacitors have been mostly used to reduce the power/ground bounce of high-speed digital system and boards. However, there has not been a systematic study to understand the effects of on-chip and off-chip decoupling capacitors on the electromagnetic radiated emission. In this paper, we report the simulation and the measurement results regarding the radiated emission due to the power/ground bounce. And we discuss the effects of the on-chip and off-chip decoupling capacitors to the power/ground bounce and the electromagnetic radiated emission. This circuit is simulated using HSPICE. Test ICs and printed circuit boards were designed and fabricated. Using a transverse electromagnetic (TEM) cell, the radiated electric field of the device under test (DUT) is measured. Combined placement of the on-chip and off-chip decoupling capacitor achieves more than 10 dB suppression of the radiated emission on the whole spectrum region. The design rule of the optimum placement of the decoupling capacitor was obtained.

Separated role of on-chip and on-PCB decoupling capacitors for reduction of radiated emission on printed circuit board

The power/ground fluctuation is known as a significant source of radiated emission. We discuss the separated functions of on-PCB and on-chip decoupling capacitors on the suppression of electromagnetic radiated emission. Due to the different ranges of parasitic inductance and the different locations of the on-chip current drivers, on-PCB and on-chip decoupling capacitors exhibit separated frequency characteristics in terms of suppression efficiency of radiation. The roles of on-PCB and on-chip decoupling capacitors are estimated by circuit simulation and a simple antenna model, and are confirmed by experiments. It is found that the on-chip decoupling capacitors are mainly effective for the suppression of radiated emission over 100 MHz frequency. Increase of the on-chip decoupling capacitance and decrease of the parasitic inductance of the package produce an improved suppression ratio at high frequency range. Combined placement and sizing of the decoupling capacitors have achieved more than 10 dB suppression of the electromagnetic radiated emission over a wide spectrum range.

The electromagnetic radiation with phase difference in rectangular loop antenna or rectangular loop circuit

By using algebra, we showed that current phase difference should not be neglected when predicting the radiation of a loop antenna. The pattern of electric field is dependent on the position of the current source. The phase of electric field is dependent on the angle. In the rectangular loop antenna, either width or length is zero, but still there exists a radiation. Only if both width and length are zero is there no radiation.

A study of design for improved EMI in a chip level

Overall EMI level of keyboard controlled IC has been improved to the level of satisfaction in the specification, which is believed to be the first time in the chip level. The ground-to-power line decoupling capacitance, the output RC filtering (or capacitance alone), and the formation of microstrip line have shown to be possible solutions for suppressing EMI characteristics in the chip level. The output RC filtering has resulted to satisfy the specification of FCC the most. The electric field peak and average value was improved to 8.8 dB and 3.1 dB respectively.

Differential-line-scheme of clock and signal bus of high-speed digital circuits and systems for minimizing electromagnetic radiated emission

Even though the electromagnetic radiated emission due to the ground and power line fluctuation of the integrated circuit (IC) and printed circuit board (PCB) is minimized, the additional reduction of the radiated emission from the clock and the signal lines are not easy. In this paper, we introduce a new clock and signal line scheme to suppress the radiated emission from the fast transition of the clock and data signals. We proved that the proposed differential-line-scheme (DLS) could reduce the radiated emission by more than 10 dB compared to the conventional single-line-scheme (SLS). First, we report the necessity and the usefulness of the differential-line-scheme and explain the operation of the inverter circuit for the differential-line-scheme using HSPICE simulation. Test ICs and PCBs were designed and fabricated, to verify the effect of differential-line-scheme with the proposed inverter circuit. The electromagnetic radiated emission due to the device under test (DUT) is measured using a gigahertz transverse electromagnetic (GTEM) cell. The measured result has shown that the differential-line-scheme with the proposed inverter circuit achieves more than 10 dB suppression of the electromagnetic radiated emission. The results confirm that the clock and signal line is fundamental source of the radiation. The proposed differential-line-scheme with the proposed inverter circuit will be useful for both high-speed digital IC and PCB design.