ANSI C63.4A-2017 pdf free download – American National Standard for Methods of Measurement of Radio- Noise Emissions from Low-Voltage Electrical and Electronic Equipment in the Range of 9 kHz to 40 GHz Amendment 1 : Test Site Validation C63.
D.2.3 Measurement methods
NSA shall be measured using one or both of the following procedures:
-The discrete frequency measurement method — see D.4 (for use with tuned dipole antennas orbroadband antennas)
—The swept frequency measurement method – see D.5
The swept frequency method may be used only with broadband antennas, but tuned dipoles may be used atspecific (fixed) frequencies in case spot checks or troubleshooting of such NSA values becomes necessary(i.e., for standard test sites only; tuned dipoles shall not be used for NSA validation of alternative test sites- see D.3.2).
For tuned dipoles,Figure D.1 illustrates the horizontal polarization NSA measurement geometry and FigureD.2 illustrates the vertical polarization NSA measurement geometry (assuming that the dipoles are tuned forall frequencies down to 30 MHz, see figures in D.8).The limiting factor of maintaining at least a 25 cmclearanice between the reference ground plane and the lower tip of the receive antenna and the transmitantenna is addressed by fixing the transmit antenna height at 2.75 m and restricting the downward travel of thereceive antenna. These restrictions are stated explicitly by the lower scan-height limit in Table D.8(see D.8).
For NSA measurements with broadband antennas，the horizontal polarization geometry is also illustratedby Figure D.1. For vertical polarization NSA measurements with broadband antennas，scan heightrestrictions usually are not required because of the much smaller fixed dimensions of a broadband antennacompared with a tuned dipole，especially between 30 MHz and 80 MHz. Using linearly-polarizedbroadband antennas allows minimum transmit antenna and receive antenna heights of i m (see also N.2 inAnnex N of ANSI C63.4-2014 for dimensional restrictions on hybrid antennas). The requirement for aminimum clearance of 25 cm between the reference ground plane and the lower tips of the receive antennaand the transmit antenna also applies for broadband antennas.
NOTE 1—For both the discretc frequency and the swept frequency methods, an impedance mismatch at the output ofthe signal source or at the input of the EMl receiver or spectrum analyzer may result in cable reflections that couldcause errors exceeding the NSA tolerance.This can be avoided by use of padding attenuators of 10 dB,i.e., one at theantenna end of the transmit antenna cable and one at the receiver end of the receive antenna cable, for both VoDrwt andVSste measurements. Attenuator values of b dB are often adequate, and values as low as 3 dB can sometimes be used.
NOTE 2—For vertically polarized antennas, it is especially important to maintain cables leaving the antennas in thesame horizontal plane as the center of the antenna directly behind the antenna for a minimum distance of 1 m. Use offerrite beads on both the transmit antenna and the receive antenna cables close to the antennas can help to eliminatecommon-mode signals that can contribute to measurement errors.
D.2.4 Single-position NSA measurements for standard test sites
A standard test site shall be validated by measuring NSA with the transmit antenna and the receive antennaseparated by the measurement distance, for both horizontal and vertical antenna polarizations,for a singlelocation of the antenna pair above the reference ground plane.Basic setups are shown in Figure D.l andFigure D.2 (see D.8), for horizontal polarization and vertical polarization of the antenna pair, respectively.Thetest site shall be evaluated in the exact measurement geometry (i.e., locations of transmit antenna and receiveantenna on the site) that is used for subsequent product testing. The transmit antenna shall be placed at theEUT location used during subsequent radiated emission measurements (e.g., at the center of the turntable),while the receive antenna shall be positioned at a location that is separated from the transmit antenna locationby the measurement distance; see also the site descriptions in 5.4.1, and the site layout in Figure 5 of 5.7 (bothin ANSI C63.4-2014).The transmit antenna and the receive antenna shall be placed in the same polarization,and oriented towards each other.Antenna heights above the ground plane per polarization and antenna typefor single-position NSA standard test site validation are as shown in Table D.2.ANSI C63.4A pdf download.