Probes and antennas

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We are constantly surrounded by electric and magnetic fields in our environment. A DC magnetic field of 25 μT to 65 μT (or 0.25 Gauss to 0.65 Gauss) has always been present due to rotation of Earth‘s molten core. The development of science and technology in the 20th century utilized electromagnetic waves properties, especially for communication purposes. At first, simpler radio communications appeared, and later also TV and radio transmitters, which brought picture and sound to every home. Rapid development of technology has brought wireless communications into all segments of our lives. Nowadays, we daily use mobile phones, not only for calling, but also for Internet access via operator networks as well as via Wi-Fi connections. Satellites are also frequently used, not only for communication among different continents and for the broadcasting of TV signal, but also for navigation purposes. Moreover, wireless technologies such as Wi-Fi, Bluetooth and others permit mass-integration of electronic devices on Internet, i.e., Internet of Things (IoT). All these electronic devices must coexist in modern world; on the one hand, they must function flawlessly and safely and must enable reliable communication with other devices when needed, but on the other hand, the electronic devices must not interfere with each other. To meet these two, often contradictory requirements, all electronic devices must be thoroughly inspected, especially in terms of electromagnetic compatibility (EMC testing). The tests shall verify (i.) that the devices do not generate an excessive electromagnetic field which could interfere with operation of other devices or even generate the field that is dangerous for humans and, (ii.) that the device under test is insensitive to interfering external electromagnetic fields. These EMC tests use electric, magnetic, and electromagnetic field meters and probes as well as various receiving and transmitting antennas (monopole, loop, horn, biconical, log-periodic and others), which operate from DC up to RF frequencies which may even exceed 50 GHz. All equipment related to field generation and measurement must be properly calibrated too. At SIQ we perform calibration of meters and probes for electric and magnetic fields and calibration of receiving and transmitting antennas.

Calibration of test equipment at SIQ

Electric and magnetic field meters and probes

Electric field meters and probes can be calibrated accredited in the frequency range from 10 Hz to 20 kHz in the range from 10 V/m to 2000 V/m. Magnetic field meters and probes can be calibrated accredited in the frequency range from 10 Hz to 10 kHz in the range from 0.1 μT to 195 μT (i.e., 1 mGauss to 1.95 Gauss, or 80 mA/m to 155 A/m). More information about the maximal electric and magnetic field can be found in the attached PDF file. Typically, we calibrate frequency response and linearity of the meters and probes according to IEEE 1309-2013 standard – Standard for Calibration of Electromagnetic Field Sensors and Probes (Excluding Antennas) from 9 kHz to 40 GHz. Isotropy according to IEEE 1309-2013 standard can be also calibrated nonaccredited.

Residual (DC) magnetic field meters

Residual (DC) magnetic field meters (i.e., Gauss meters) can be calibrated up to 100 A/cm (i.e., up to 12.5 mT or up to 125 Gauss). Nonaccredited calibration typically involves linearity measurement at 10 measuring points.

Calibration of transmitting and receiving loop antennas

Antenna factor (AF) is a key parameter for loop antennas that is used for EMC tests according to MIL-STD-461, RE101, IEEE 291 and CISPR 16 standards. The AF is defined as ratio between the electromagnetic field and the voltage on the loop antenna; the AF of receiving antennas is defined as the ratio between the incident electromagnetic field and the voltage at the output port of the receiving loop antenna and vice versa, the AF of transmitting antenna is defined as the ratio between the transmitting electromagnetic field and the voltage at the input port of the antenna.

At SIQ we calibrate AF according to the absolute and relative calibration method. Three antenna method is used as the absolute method and in this case the AF is calculated from measurements of different three antenna pairs. When a relative method is applied the AF of unknown antenna is determined using a known AF of a reference antenna. Both methods are described in CISPR 16-1-6 and ANSI IEEE C63.5 standards. The AF calibration is performed in the frequency range from 9 kHz to 120 MHz.

Calibration of transmitting and receiving monopole (rod) antennas

At SIQ we calibrate antenna factor (AF) of monopole antennas according to CISPR 16-1-6 and ANSI IEEE C63.5 standards. Calibration is performed using the Equivalent Capacitance Substitution Method in the frequency range from 9 kHz to 30 MHz, or up to 100 MHz if required.

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