D.V. Zhuravlev1, A.N. Golubinsky2, N. A. Letov3

1–3 Voronezh State Technical University (Voronezh, Russia)
1ddom1@yandex.ru, 2annikgol@mail.ru, 3nikitaletovv@mail.ru

Problem statement. With the development of artificial neural networks that automatically classify electroencephalogram signals, the development of portable non-invasive brain-computer interfaces has become relevant. The versatility and ease of everyday use of neural headsets in such interfaces directly depends on the type of electrodes. The main parameter of the interfaces, such as classification accuracy, also depends on the type of electrodes. Traditionally, metal electrodes with an Ag/AgCl coating provide the best performance. However, their installation on the operator's head is quite laborious, while the skin-electrode surface requires wetting with a special electrically conductive gel, which makes their use in everyday use problematic.

The purpose of the work. Development of dry-type resistive-capacitive electrodes for use in portable brain-computer interfaces with bioelectric signal transmission characteristics similar to or exceeding those of traditional Ag/AgCl electrodes. Allowing for quick installation/removal without using an electrically conductive gel.

Results. Three circuit implementations of active resistive-capacitive pin-type electrodes have been developed. Electrode circuits based on the TLC272 operational amplifier have been developed in two versions. A variant with a single gain and an improved version with pre-amplification, an active bandpass filter in the frequency range of 0.1-120 Hz. A single gain circuit based on the TL062CD operational amplifier was also developed. Printed circuit boards and electrode designs have been developed, and existing product layouts have been manufactured. The electrodes are adapted for use in conjunction with recording equipment assembled from OpenBCI open source materials (Cyton board).

The methodology of electrode research is based on simulation modeling and field experiments. The calculation and comparison of key quality metrics are carried out: Сommon Mode Rejection Ratio, signal-to-noise ratio at the input and output of the system, noise factor. It has been found that the use of an active interference suppression circuit is critically important for "dry type" electrodes, making it possible to increase the common-mode rejection ratio from 96.94 dB to 100.95 dB. The configuration combining advanced active electrodes based on the TLC272 amplifier in combination with an active interference suppression circuit is considered optimal for practical use. This scheme provides a common-mode rejection ratio of 100.95 dB (obtained in field experiments). The circuit has a noise factor of 1.385 dB, which is almost similar to "wet type" electrodes, which give a noise factor of 1.346 dB.

Practical significance. The developed active resistive-capacitive electrodes are "dry type" electrodes. However, these electrodes have similar characteristics, and in some cases exceed the characteristics of classic Ag/AgCl "wet type" electrodes. This allows them to be used on a daily basis in portable brain-computer interfaces and to ensure the quality of recorded signals at the level of industrial stationary electroencephalogram recording complexes. It is noteworthy that the assessment of the considered quality metrics was carried out not separately on the developed electrodes, but on the entire "electrode-recording equipment" system. The values of quality metrics obtained during field experiments, which coincide with the results of simulation modeling, allow us to conclude that it is advisable to use small-sized OpenBCI recording equipment with active electrodes in portable brain-computer interfaces.

Zhuravlev D.V., Golubinsky A.N., Letov N.A. Development dry type resistive-capacitive electrodes for use in wearable portable brain-computer interfaces. Biomedicine Radioengineering. 2026. V. 29. № 2. P. 61–76. DOI: https:// doi.org/10.18127/ j15604136-202602-06 (In Russian)

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