V.A. Efimov, E.V. Sorokin

The heart rate (HR) is one of the main parameters of an estimation of a functional condition of the person health. There are various methods of HR measurement, which choice depends on the purpose of medical-biologic research. 2 or 3 channels for daily HR (ECG) monitoring organization are more often used. In this article one of possible variants of organization of heart activity daily monitoring is considered. The sug-gested acquisition - transmission device for biomedical data transferring consists of two blocks. The first - contains electrodes, power supply, amplification and signal filtration microchip, the micropower transmitter. The second block located on a belt of the patient or in any other place near first block, witch contains memory, the reception device, a communication interface with external PC, the power supply. Device-s blocks are connected together by micropower communication system. There are various types of communication standards for data transmission: Bluetooth, Zigbee, 433Mhz communication, 128 KHz communication and others. 128 KHz communication is chosen in this article because it provides the lowest power consumption. The developed block diagram of communication system includes a transmitter and receiver. Transmitter consists of the specialized integrated circuit for collecting and processing of a HR signal, OOKIFM (On-off keying of impulse flow modulation) modulator, the generator and the ferrite antennas. Receiver consists of the ferrite antenna, preamplifier, band pass filter, amplifier and amplitude detector. It is possible to use for 128 KHz communication the printed antenna or the coil antenna with the ferrite core. The carried out researches have shown, that ferrite magnetic antenna has the best characteristics. In this article circuit design variants are considered for realization of transmitting and receiver devices. Results of an experimental research are resulted. In a model sample the communication distance 40 cm is provided at low power consumption: 2,3 мА in the transmitter and 4,05 мА in the receiver. Approximate sensitivity of the receiver is 1 mV at 20dB SNR (Signal to Noise Ratio). For increase of a communication distance up to 80 cm and increase of a noise immunity of a system it is supposed to increase inductance of the ferrite antenna of transmitting and receiving modules, the order of the band pass filter and use DBPSK modulation instead of OOKIFM.