How to meter and calibrate a double-ridged horn antenna

Introduction:

Double ridge horn antenna how to measure and calibrate is an important work of the laboratory managers, every year need to be all the electromagnetic instruments and equipment in the warehouse calibration work, in particularDouble ridge horn antennaWith the characteristics of broadband and high gain, so it is very widely used in EMC testing, we need to know more about how to calibrate the double ridge horn antenna.

Double ridge horn antenna polarization:

The polarization of a double ridge horn antenna can be determined by the direction of the antenna polarization by the direction of the diaphragm in the middle of the antenna, with the polarization (electric field) parallel to the direction of the diaphragm in the double ridge horn setup. For horizontal polarization, the N-connector must be on the side. For vertical polarization, the N-connector faces the ground (or top).

Horizontal polarization of a double-ridged horn antenna

When horizontally polarized, the septum is also horizontally aligned;

Vertical polarization of a double-ridged horn antenna

With vertical polarization, the diaphragm is also vertically aligned.

How to Calibrate the Gain and Antenna Factor of a Double Ridge Horn Antenna

NOTE: The gain and antenna factor are centered between the end of the test horn antenna and the N connector.

For either measurement, an additional set of test horn antennas is required to transmit or receive the signal from the horn antenna under test.

Using a test horn antenna to measure the horn antenna under test

When conducting launch tests:

The test antenna uses the transmit function. The antenna under test uses the receive function.

Antenna installations should measure the distance from the center of the N connector and the end of the antenna to the equipment under test (EuT).The actual field strength in RX applications is determined by the antenna coefficient (with the addition of frequency-dependent cable loss for greater accuracy). The antenna factor describes the ratio of the incident field strength to the voltage (50 W) generated at the antenna connector.

Plot of antenna coefficient test results for a double ridge horn antenna

During immunity testing:

The test antenna uses the receive function. The antenna under test uses the transmit function.

It is required to measure the distance between the end of the antenna and the device under test. In immunity testing and other applications (TX) where it is necessary to generate a defined field strength, calculations are made using an antenna gain plot. The field strength graph provided simplifies the determination of the drive power.

Plot of antenna gain test results for a double ridge horn antenna

A method for determining the directional pattern-direction map of a double-ridged horn antenna:

The directional pattern of the antenna can be used to estimate the size of the homogeneous area.3 dB angle (half-power beamwidth) describes the angle of antenna rotation required to obtain a field strength attenuation of -3 dB (to 711 TP3T) from the main lobe (0 dB = 1001 TP3T) to the left and to the right. In this case, the radiated power density (power per unit area) is 501 TP3T.

Example of a directional pattern for a double-ridged horn antenna