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Radiated Spurious Emissions Measurement by Substitution Method

Qin Yu Alcatel-Lucent USA 6200 E. Broad St., Rm 4L04-1G Columbus, OH 43213 Abstract The total power substitution method is a measurement approach preferred by FCC and other authorities for evaluating the radiated spurious emissions of an RF product. This paper reviews and discusses the setup and procedures for conducting radiated spurious emissions measurement by using this approach. Two estimation methods, the free space path loss (FSPL) method and the site attenuation method, are also presented and elaborated in the paper. With a given field strength of a spurious signal at the receiving antenna, its effective radiated power (ERP) and the required input power to the substitution antenna can be estimated beforehand to save testing time and efforts. The calculated results are compared with the measured ones from both broadband EMC antennas and tunable dipoles. The pros and cons of each method are addressed as well. I. INTRODUCTION A. Frequency Spectrum to Be Investigated The frequency range required for radiated spurious evaluation in general depends on the fundamental frequency of the equipment under test (EUT). FCC requires that the highest frequency to be investigated for an intentional radiator be the 10th harmonics of the highest fundamental frequency or 40GHz, whichever is lower if it operates below 10GHz [2]. ITU-R SM.329-9 recommends that the spurious emissions in the frequency range between 30MHz and the 5th harmonics of the highest fundamental frequency be restricted for the fundamental frequency between 600MHz and 5.2GHz. Nevertheless, China YD 1169.2 only requires the spurious emissions between 30 MHz to 1GHz to be measured. Table I. YD 1169.2 Radiated Spurious Emissions Requirements for Cellular System (No Less Than 3m) Freq. Range (MHz) 30 ­ 88 >88-216 >216-960 960-1000 B. Limits The spurious emissions limits specified by YD 1169.2, FCC Parts 22, 24 and 27 and 3GPP are given in Tables I-III, where flow and fup are the lower and upper frequency block edges in MHz, respectively. In the frequency range below 30 Limit (Peak, dBm) -57 -54 -51 -43 RBW (kHz) spurious signal and the required input power to the substitution antenna. The calculated results are compared with the measured ones from both broadband EMC antennas and tunable dipoles. The pros and cons of each estimation method and different type of substitution antennas are addressed and discussed as well in the paper. II. RADIATED SPURIOUS MEASUREMENT To conduct an effective radiated spurious measurement, the frequency spectrum to be investigated, the limits to be applied, the equipment setup to be used and the testing procedures to be followed are four important aspects which need to be known or investigated before the actual testing starts. Each of the above aspects is addressed in the following. Also discussed are two commonly used power units, EIRP (Equivalent isotropically radiated power or, alternatively, Effective isotropically radiated power) and ERP.

Many countries, including the United States, require the measurement of radiated spurious emissions of an intentional radiator as part of its regulatory certification. Spurious emissions of a radiator are unwanted emissions on frequencies which are outside the necessary bandwidth during its normal operation excluding out-of-band emissions. Normally, the limits of spurious emissions are specified in terms of field strength, or peak power, or mean power attenuation relative to the mean output power of a transmitter [1-5]. As a result, the radiated spurious emissions of a product are usually measured either by the total power substitution method or the field strength approach. The total power substitution method is an approach preferred by many regulatory and industry authorities, such as FCC, China MII (Ministry of Information Industry) [3], TIA [4] and 3GPP [5], for making the radiated spurious emissions measurement. TIA [4] provided the detailed measurement procedures for using the total power substitution method. The measurement uncertainty was discussed in [6]. CISPR 16-2-3 [7] discusses the substitution method for measuring the radio disturbance in the frequency range of 30 MHz to 18 GHz. But it fails to provide well defined and consistent measurement procedures. This paper reviews and discusses the equipment setup and measurement procedures for making the radiated spurious emissions measurement by using the substitution method. With a given field strength of a spurious signal at the receiving antenna, two approaches, the FSPL and the site attenuation approaches, are presented and elaborated in the paper for estimating the effective radiated power of the


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MHz, the magnetic field strength is to be measured instead of the electric field strength per FCC instructions. Table II. FCC Radiated Spurious Emissions Requirements for Intentional Radiators Rules FCC Frequency /Resolution Bandwidth Freq RBW Freq RBW (MHz) (MHz) flow 1MHz f d flow - t100 <f< t1% 1MHz kHz flow & of & fup< f BW f t fup + < fup + 1MHz t1M 1MHz; Hz Power Limit (Ave.)

specified in the standard that whether the EIRP or ERP shall be measured. D. Measurement Antenna and Site ITU [1] states that the antenna used in the total power substitution measurement can be a tuned dipole antenna or a reference antenna with a known gain referenced to an isotropic antenna. In other word, a broadband antenna can be used as long as its dBi is available from the antenna calibration data sheet, where dBi represents the gain of an antenna in decibels with respect to an isotropic radiator. There are many advantages in using a broadband antenna. The broadband antenna is easier to use than a tunable dipole and permits fast measurement. It exhibits less mutual coupling as well. The tunable dipole can only be used for discrete frequency measurement. Additionally, it is not suitable for vertically-polarized measurements for a frequency lower than 75MHz due to its size. Otherwise, significant errors would be introduced by using tunable dipoles at low frequencies. The testing site can be either a semi-anechoic chamber or OATS (Open Area Test Site) which meets the site attenuation requirement [1]. III. MEASUREMENT SETUP AND PROCEDURES

22.917 (850) 24.238 (PCS) ; 27.53(g) (AWS)

-13 dBm

Table III. 3GPP TS25.113 Radiated Emissions Limits Freq. Range (MHz) 30 ­ 1000 1000-12,750 Limit (ERP, dBm) -36 -30 RBW (kHz) 100 1000

Though FCC prefers using the total power substitution method for measuring radiated spurious emissions, FCC still accepts the testing results based on the field strength measurement at this time. For the field strength measurement, if a radiation limit is specified in power, its equivalent field strength limit has to be derived based on the relationship between radiation power and field strength for an ideal radiator, such as, an ideal half-wave dipole. C. EIRP vs. ERP In the above three tables, the limits of spurious emissions are all specified in terms of different power. The EIRP and ERP are two terms commonly used when referring to the radiated power. The EIRP is the amount of power that a theoretical isotropic antenna (that evenly distributes power in all directions) would emit to produce the same power density observed in the direction of maximum antenna gain at a given point [8]. The ERP is similar to the EIRP, but uses other reference antennas than an isotropic antenna, e.g. a half-wave dipole. The ERP is equal to the amount of power that would have to be applied to a half-wave dipole, oriented in direction of maximum gain, to give the same power density at a given point. A half-wave dipole antenna has a gain of 2.15dB greater than that of an isotropic antenna [4]. The dipole can focus the available energy in certain desired directions, so that the radiation in those directions is greater than the radiation from an isotropic source with the same power fed into the antenna. As a result, for the same field strength, the EIRP needs 2.15dB more power than the ERP does. Therefore, it is EMI conservative to measure the EIRP instead of the ERP against the required limit if it is not

The measurement setup and testing procedures are addressed in the following. A. Measurement Setup The initial setup for the total power substitution measurement is same as for the field strength measurement: a. b. Place the EUT on a non-conductive pad or a table on the turntable. Terminate the EUT antenna port with a non-radiating load of 50 through a non-radiating cable if the EUT does not have an integral antenna; Otherwise, the tests are to be run with the EUT equipped with the integral antenna. If the condition of the dummy loads used is not clear, special care must be taken to prevent the dummy loads from radiating and overloading the receiver by placing the dummy loads under the turntable if possible. Turn on the measurement equipment, set up the EUT and let the EUT warm up for 30 minutes before the actual measurement starts. Mount the antenna on the antenna mast and connect the accessories. Set the measurement antenna at least 3 meters away from the EUT boundary, where the EUT boundary is the minimum circle centered on the turntable and encircled the EUT and its accessories.


d. e.

B. Testing Procedures Based on the procedures provided in TIA-603-C [4] and the author's own experience, the step-by-step testing procedures for performing radiated substitution measurement are recapped below: a. Connect the equipment as illustrated in Figure 1.



Adjusting the spectrum analyzer for the appropriate settings (see Tables I-III), where the video bandwidth needs to be at least three times of the resolution bandwidth.

Receiving Antenna RF Amplifier


EUT g. h.


fc Rejection Filter

horizontally polarized, and with the SG tuned to a particular spurious frequency, raise and lower the receiving antenna to obtain a maximum reading at the spectrum analyzer. Adjust the output power of the SG until the previously recorded maximum reading is obtained for this set of setup conditions. During the height scan, a narrow frequency span or sample averaging can be utilized to avoid the ESD generated signals if needed. Repeat the above step f with both antennas vertically polarized for each spurious frequency. Calculate the EIRP or ERP numbers by correcting the readings obtained from the steps f and g with the path loss (PL) and antenna gain G: EIRP (dBm) = PSG(dBm) ­ PL (dB) + G (dBi), ERP (dBm) = EIRP(dBm) - 2.15 dB, (1)


Figure 1. Measurement setup for evaluating the field strength of spurious emissions.

where PSG is the output power of the SG into the substitute antenna and G is the gain of the substitution antenna relative to an isotropic antenna (dBi). IV. RADIATED POWER ESTIMATION After the maximum field strength is measured, estimating the necessary input power to the substitution antenna or the radiated power is an important step before the actual measurement of the radiated power. It will save significant amount of time and efforts in trial and error during the measurement. Based on the known field strength E at the receiving point, its EIRP can be estimated. Three approaches which are commonly used for estimating EIRP are discussed here. One uses the relationship between electric field strength and power, one uses the FSPL, and another approach uses the site attenuation to estimate the EIRP. The first two approaches, as are shown below, are essentially same. A. Electric Field Strength vs Power Formula For a directive antenna at the frequency f, its net input power P (watts) and the maximum field strength E (V/m) in the free space at a distance R(m) on its bore-sight axis exhibits the following relation:

E (V / m ) 30 u Pt ( w ) u G t R (m) ,

RF Amplifier

Receiving Antenna


Substitution Antenna


fc Rejection Filter

SG Turntable

Figure 2. Measurement setup for determining the radiating power of EUT at spurious frequencies. c. Set the receiving antenna at horizontal polarity. For each spurious frequency, raise and lower the test antenna from 1m to 4m while rotating the turntable 360° to determine the maximum reading; record this maximum reading and frequency. Be sure to have enough sampling points for accurate frequency readings. Repeat the above step c with the receiving antenna polarized vertically. Record the testing data. Remove the EUT and replace it with a substitute antenna (see Figure 2). The centre of the substitute antenna should be placed in the same spot as the geometric centre of the EUT and parallel with the receiving antenna. If the EUT is comprised of more than one unit, each unit shall be measured separately [7]. If a tuned dipole is used, the antenna should be half-wavelength for each frequency involved. At the lower frequencies, where the substitute antenna is very long, the half-wavelength requirement will be impossible to achieve when the antenna is polarized vertically. In such case the lower end of the antenna should be 0.3m above the ground [4]. Feed the substitute antenna with a signal generator (SG) through a non-radiating cable, as illustrated in Figure 2, where the SG is placed on the floor at the end of the chamber near wall. With the antennas at both ends

d. e.



where Gt is the transmitting antenna gain (numeric) at R and f. The gain Gt at some typical distances, such as 1m or 3m, usually can be found from antenna's calibration data sheets. The distance R is measured from the transmitting antenna to the field point on its bore-sight axis. Here, the effects of other objects including the receiving antenna on the transmitting antenna are ignored. The minimum far field distance can be roughly estimated by using the formula /2 for wire antennas and 2D2/ for aperture antennas [11]. Since EIRP = Pt(w)×Gt, the equation (2) can be rewritten as [1]

E (V / m ) 30 u EIRP . R (m)



The EIRP thus equals



the EIRP can be estimated by


107 E adj (dBPV / m) 20 log R(m) 2.15

E (dBm) 20 log R(m) 2.15, ERP E (dBm) 20 log R(m),



Eradj ( dBm) FSPL 20 log f ( MHz ) 29.79,


where E (dBm) is the adjusted field strength measured at the receiving antenna and corrected by the path loss or gain and the antenna factor. The net input power to the substitute antenna equals

PSG (dBm)



EIRP(dBm) PLt (dB) Gt (dBi)


E (dBm) 20 log R(m) 2.15 PLt (dB) Gt (dBi),

where PL is the path loss between the SG and substitute antenna. Hence, for a known electric field strength at R and f, its EIRP and the required input power to the substitute antenna can be estimated from Eq. (4) and Eq. (5), respectively. In other words, by injecting the amount of power estimated from Eq. (5) to the substitution antenna that is separated from the receiving antenna by a distance of R, the receiving system should detect a field strength value close to what is expected if everything functions properly. When R=3m, the EIRP and ERP values of the substitute antenna can be calculated by:

EIRP 3 m ( dBm ) ERP 3 m ( dBm ) E adj ( dBm ) 11 .69, E adj ( dBm ) 9.54 .

where Eadjr is the field strength at the receiver in dBm. It can be shown that Eq. (6) is identical to Eq. (4) by substituting the expression for FSPL into Eq. (6). In other words, the estimation based on either Eq. (3) or the FSPL method will provide the same result due to the fact that both formulas assume free space condition. However, the field strength measured during normal EMC testing gives the maximum value by adjusting the antenna height from 1m to 4m. This height scan could increase the reading by several decibels due to the ground reflections when the testing is conducted on an OATS or in a semi-anechoic chamber. The EIRP calculated by Eq. (4) does not take this effect into the consideration and thus needs to be corrected by a correction factor CF. An average 4.7dB CF is suggested by FCC [10], while ITU suggests a 4.0dB CF [1]:

EIRP ( dBm ) ERP E

adj max adj Emax ( dBm ) CF 20 log R ( m ) 2.15,


( dBm ) CF 20 log R ( m ),

where Eadjmax is the maximum field strength measured at the receiving antenna adjusted by the path loss or gain and the receiving antenna factor. C. Site Attenuation Method The EIRP at a spurious frequency can also be estimated from the measured site attenuation data:

EIRP ( dBm ) Pr ( dBm ) PL ( dB ) Gr ( dBi ) SiteLoss ( dB ),

Similarly, when R=5m, the EIRP and ERP values of the substitute antenna can be calculated by:

EIRP 5 m ( dBm ) ERP 5 m ( dBm ) E adj ( dBm ) 16 .48, E adj ( dBm ) 13 .98 .

B. FSPL Method FSPL is the loss in signal strength of an electromagnetic wave through free space, with no obstacles nearby to cause reflection or diffraction. FSPL is defined as (4 R/ )2, where is the wavelength in meter and R is the distance between the receiving antenna and radiating source. The FSPL can be expressed in decibel as

FSPL ( dB ) 20 log f ( MHz ) 20 log R ( m ) 27 .6 .

where Pr is the reading of the receiver and Gr is the gain of the receiving antenna in dBi. In a non-freespace environment, the calculated or measured site attenuation data should be used instead of the FSPL to take the reflections from the floor, walls and ceiling and mutual coupling into consideration. The Normalized Site Attenuation (NSA) is normally conducted for the site certification. The NSA is the site attenuation divided by the antenna factors of the radiating and receiving antennas (AFTx and AFRx) [9]:

NSA(dB ) V direct V site AFTX AFRX 'AF ,

The EIRP is thus equal to [1]

EIRP ( dBm) Pradj (dBm ) FSPL ( dB ),

where Padjr is the power reading of the receiver (Pr ) adjusted by the path loss PLr between the receiver and the receiving antenna in dB and the gain of the receiving antenna Gr in dBi. The Padjr equals

Pr adj ( dBm ) Pr ( dBm ) PL r ( dB ) G r ( dBi ).

Since Eradj (dBm) Pr (dBm) PLr (dB) AFr , and

AF 9.73


, 20 log10 f MHz 29.79,

G ( dB ) AF ( dBm 1 )

where Vdirect is the reading from the measurement with two coaxial cables disconnected from the receiving and transmitting antennas used for the site attenuation and connected to each other via an adapter, Vsite is the reading of the maximum signal from the receiving antenna when the coaxial cables reconnected to their respective antennas and the receiving antenna's height is scanned, AF is the correction factor for antenna mutual impedance and AFs account for the changes from antenna mutual coupling, antenna coupling with ground plane, antenna pattern, non-uniform field illumination and near-field effects, etc. [9]. ANSI C63.4 gave the correction factors for tuned dipoles at 3m separation. The AF correction is not necessary if the geometry-specifically measured AFs are used, that is, NSA measurements are performed in the same geometry as in their


antenna calibration [9]. Using accurate AFs is critical for achieving an accurate NSA. It can be derived that

EIRP ( dBm ) E radj ( dBm ) NSA ( dB )


' AF 20 log f ( MHz ) 29 . 79 ,

8) are listed in Table VII, where the NSA data measured by EMCO 3110B Biconical and 3148 Log-Periodic antennas over a 5m distance at 1m height were used in the calculation. Using the same type of antennas for both NSA measurement and radiated substitution measurement should provide more accurate results. Table IV. EUT Radiated Field Strength Measured with 120kHz RBW and Peak Detector

Test No Freq (MHz) Ant Pol (V/H) Height (cm) Eadjmax (dBm)

where NSA is the normalized site attenuation value at the same antenna height, distance and polarization as the field strength measured. The site attenuation approach is the preferred way for estimating the EIRP and the antenna input power if possible. The FSPL approach is relatively simpler, flexible and easier to use and it does not require the site NSA data. V. RESULTS AND DISCUSSIONS One compact wireless base station was used as the testing model. Its radiated emissions were first measured by the field strength method at a testing distance of 5m. The EUT, as shown in Figure 3, has a height of 0.5m and its bottom is 0.725m away from the floor.

1 2 3 4

35.6 37.2 198.8 295.8


100 100 250 200

-76.40 -76.74 -75.36 -68.53

Table V (a). Radiated Power Measured with Biconical and Log-Periodic Antennas

Test No Freq (MHz) Power of SG (dBm) PL (dB) Ant Gain (dBi) EIRP (dBm)

0.5m 1.225m

1 2 3 4

35.6 37.2 198.8 295.8

-58.0 -59.1 -62.7 -63.2

0.24 0.31 0.69 0.83

-10.3 -9.58 1.35 4.96

-68.54 -68.99 -62.04 -59.07

Table V (b). Radiated Power Measured with Tunable Half-Wavelength Dipole Figure 3. Geometric Size of the EUT. The radiated field strength of the above EUT was measured first and four highest noise signals were observed and recorded in Table IV, where the EMCO 3110B Biconical antenna and EMCO 3148 Log-Periodic antenna were used for the measurement. The above EUT was then replaced by a broadband EMC antenna and an EMCO 3121C tunable dipole, respectively. The input power PSG from the SG to the substitute antenna and the EIRP were recorded in Table V. The antenna gains listed in Table V were extrapolated from their calibration data with same polarization at 2m height and 5m testing distance, except for the tunable dipole at vertical polarization where its gain at 2.5 m height was used. It can be seen from Table V that the difference between the EIRP values measured by a broadband EMC antenna and a half-wave dipole at 198.8MHz and 295MHz is very small, less than 1.1dB. But the discrepancy of their EIRP values at 35.6MHz and 37.2MHz is not trivial. The significant error was mainly caused by the large size of tunable dipole at low frequencies for vertical polarization. Based on the measured electric field strength listed in Table IV, the EIRP values from the FSPL approach (Eq. 7) with a 4.7dB CF are calculated and given in Table VI, where B (dB) and D (dB) give the difference between the estimated EIRP and the measured EIRP by using a broadband antenna and a half-wave tunable dipole, respectively. The estimated EIRP values from the site attenuation approach (Eq.

Test No Freq (MHz) Power of SG (dBm) PL (dB) Ant Gain (dBi) EIRP (dBm)

1 2 3 4

35.6 37.2 198.8 295.8

-48.5 -50.7 -64.4 -59.1

0.24 0.31 0.69 0.83

0.7 0.95 2.0 1.9

-48.04 -50.06 -63.09 -58.03

It can be seen from Table VI that after applying a CF in the FSPL equation, the discrepancy between the estimated and measured EIRP values has been reduced significantly to below 4dB, excluding the lower frequency signals with tunable dipoles. However, for the measurement over a wide frequency range, the receiving antenna with 1~4 meter height scan may not observe the ground reflection at certain frequencies and certain height. Therefore, using a 4.7dB CF in Eq. (6) may not always be appropriate. In addition, the effects from chamber wall, ceiling and the mutual coupling among antennas and the floor have not been taken into consideration in the FSPL equation. In the site attenuation method, the measured site attenuation takes the geometry related effects, chamber imperfection and coupling from the surrounding into the account. Using the calculated NSA with geometry-specific AFs can also produce fairly accurate results. The AFs supplied by manufacturers are inaccurate and have to be corrected with correction factors [10-11]. The mutual-coupling effects are evident for closely-spaced horizontally-polarized antennas, especially at low antenna


heights [10]. These coupling effects are more pronounced for tunable dipoles than broad-band antennas. The NSA data used in Table VII were measured by using EMCO Biconical and Log-periodic antennas. Table VI. Estimated EIRP with the FSPL Method (Eq. 7)

Test No Freq (MHz) Eadjmax (dBm) EIRP (dBm)



antenna gave larger error than the 3148 Log-Periodic antenna. VI. CONCLUSIONS This paper reviewed and outlined the testing setup and procedures for making the substitution measurement of radiated spurious emissions. Two methods, the free space path loss method and the site attenuation method, were presented and discussed for estimating the radiated spurious power. The estimated results were compared with the measured ones from both broadband antennas and tunable dipoles. The results showed that the site attenuation method usually gives more accurate estimation than the FSPL method. When the measurement is conducted in an OATS or semi-anechoic chamber, the FSPL method can give a relatively good and quick estimation if the reflection from the floor is compensated. Tunable dipoles are not suitable for low frequencies measurement due to its size. With broadband EMC antennas, a good agreement between the measured and calculated EIRP/ERP can be achieved. REFERENCES [1]. Recommendation ITU-R SM.329-9, Spurious Emissions [2]. FCC Parts 2, 22, 24, and 27, Title 47 Code of Federal Regulations, Federal Communications Commission, Washington DC, USA, October 1, 2008 [3]. YD1169.2-2001, Requirement and Measurement Methods of Electromagnetic Compatibility for 800 MHz CDMA Digital Cellular Mobile Telecommunications System, Part 2: Base Station and Ancillary Equipment, Communication Industry Standard of People's Republic of China, November 1, 2001 [4]. TIA-603-C, Land Mobile FM or PM - Communications Equipment - Measurement and Performance Standards, TIA, December 2004 [5]. 3GPP TS 25.113, Technical Specification Group Radio Access Network; Base Station (BS) and repeater Electromagnetic Compatibility (EMC), V6.4.0, 2006-03 [6]. S. Jayashankar, "A Detailed Test Method for Measuring Radiated Spurious Emissions by Signal Substitution and the Effect of Relevant Source Parameters", IEEE 2002 EMC Symposium, vol. 1, pp. 509-514, 2002 [7]. CISPR 16-2-3, Specification for Radio Disturbance and Immunity Apparatus and Methods, Part 2-3 Methods of Measurement of Disturbances and Immunity ­ Radiated Disturbance Measurements [8]. IEEE Std. 100, The Authoritative Dictionary of IEEE Standards Terms, 7th Edition, The Institute of Electrical and Electronics Engineers, New York, 2000. [9]. Zhong Chen and Mike Windler, "Systematic Errors in Normalized Site Attenuation Testing", Compliance Engineering 17, No.1 pp. 38­48, Jan/Feb 2000. [10].Albert A. Smith, Jr., Robert F. German and James B. Pate, "Calculation of Site Attenuation From Antenna Factors", IEEE Trans on Electromagnetic Compatibility, Vol. 24, No. 3, pp. 301-316, Aug. 1982 [11]. Q. Yu, "Measurement of 1-40GHz Radiated Electric Field Spurious Emissions", IEEE 2001 EMC Symposium, vol. 1, pp. 458-463, 2001



1 2 3 4

35.6 37.2 198.8 295.8

-76.40 -76.74 -75.36 -68.53

-64.9 -65.3 -63.9 -57.1

3.6 3.7 -1.9 2.0

-16.9 -15.2 -0.0 0.9

Table VII. Estimated EIRP with Site Attenuation Method

Test No Freq (MHz) Eadjmax (dBm) NSAc (dB) EIRP (dBm) (Est)




1 2 3 4

35.6 37.2 198.8 295.8

-76.40 -76.74 -75.36 -68.53

10.6 9.7 -5.9 -10

-64.6 -65.4 -65.1 -58.9

4.0 3.6 -3.0 0.2

-16.5 -15.4 -2.0 -0.9

6.00 4.00 2.00 Psg (dB) 0.00 -2.00 -4.00 -6.00 10 100 1000 Freq (MHz) 10000

Bicon-H Bicon-V Log-Periodic-H Log-Periodic-V Horn-H Horn-V


Figure 4. The Discrepancy between Measured and Calculated Input Power to Substitute Antenna. The above EUT measured only has a limited number of noise signals (see Table IV). In order to cover a wider frequency range, the EIRP in the frequency range of 30MHz to 12GHz was measured with the assumed field strength at the receiving antenna and compared with the estimated ones by using the NSA method (Eq. 8). The EMCO 3310B Biconical antennas, 3148 Log-Periodic antennas, and 3115 Double-Ridged Horn antennas, were used to conduct the testing in the frequency range of 30MHz to 250MHz, 200MHz to 1GHz, and 1GHz-12GHz, respectively. The measurement above 12GHz was not conducted due to lack of the site attenuation data. The results were plotted in Fig. 4, where the antenna gain calibrated at 1m height and 3m test distance was utilized. The plot shows that in general, the discrepancies between the measured and the calculated input power to the substitution antenna are less than 4dB. At 230MHz, the 3310B Biconical antenna gave a larger error near its upper frequency range than the 3148 Log-Periodic antenna. Similarly, at 1GHz, the 3115 Double-Ridged Horn



Radiated Spurious Emissions Measurement by Substitution Method

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