Camera-Ready Paper for the 5th International Symposium on Power-Line Communications
and Its Applications (ISPLC2001), Scandic Triangeln, Malmœ,Av, Sweden April 4-6, 2001

Measurement of Japanese Indoor Power-line Channel
Shinji TSUZUKI, Shinji YAMAMOTO, Takashi TAKAMATSU, Yoshio YAMADA

Dept. of Electrical & Electronic Eng., Ehime University
3-Bunkyo, Matsuyama, 790-8577, JAPANtsuzuki@ee.ehime-u.ac.jp
Abstract The impedance characteristics of household-appliances and power-line channels in
the Japanese environment are measured in the high-frequency band, i.e., from 70kHz to 35MHz.
The transfer function of the channels is also measured and these results are shown. The powerline channel can be treated as a distributed constant circuit at the high frequency band. In thispaper, the distributed constants of a VVF cable with two wires, which is widely used for theindoor power-line in Japan, are obtained by measuring the relative dielectric constant (εr ) andthe dielectric loss-tangent (or dissipation-factor, tan δ).
Keyword: measurements and channel characterization, impedance characteristic of household
appliances and power-line, transmission characteristic, distributed constants of VVF cables

1Introduction

The research and development of high-speed power-line communications (PLC) of around 10M bps using the high-frequency band under 30MHz have become active. To realize the high-speed
PLC, it is important to know the characteristics of power-line as a communication channel. Considering the Japanese PLC environment, the allowed band is from 10kHz to 450kHz. Therefore,
the channel characteristics of Japanese power-line environments in the high-frequency band have
not yet surveyed suﬃciently.
In this paper, the impedance characteristics of household-appliances and power-line channels
are measured in the high-frequency band, i.e., less than 35MHz. And the transfer function of
the channels is measured and these results are shown[1].
The power-line channel must be treated as a distributed constant circuit at the high-frequency
band. In this paper, the distributed constants of a VVF (Vinyl insulation, Vinyl sheath, Flat)
cable with two wires of φ1.6mm, which is widely used for the residential power-line in Japan,
are obtained by measuring the relative dielectric constant (εr ) and the dielectric loss-tangent(or dissipation-factor, tan δ)[2].

2

Impedance of household-appliances

Figure 1 shows our impedance-measurement scheme. The impedance was calculated from theS-parameter of S11 measured by a network analyzer (HP4395A). The calibration was done at
the outlet as shown in the ﬁgure. The impedance of an appliance was calculated from that of
the AC-power-line itself and parallel-impedance of the AC-line and the appliance.
The result is shown in Fig.2. The 54 kinds of appliances with 89 power-on/oﬀ states weremeasured. The frequency range in log-scale was segmented into 40 sub-bands, and the maximum
and minimum impedance-values of each appliance in the respective band were measured. The
measured values were plotted as a probability distribution. For example, 78.8% appliances areincluded in the darkest-shadowed area.
One of the diﬃculty of PLC in the low frequency-band (less than 450kHz) is the dispersion ofindividual appliances’ impedance. However, it is measured that the dispersion tends to decrease
gradually in the range from 500kHz to 10MHz. When the frequency is higher than 10MHz, itchanges to increase again. Therefore, the frequency band where the inﬂuence of the dispersion
of appliances’ impedance is the least, is around 10MHz.

791

calibration

ElectricalappliancePowerline

Impedanceupper|Z| (ohm)
1k
5m
2m
1m

0.1µF
50Ω: 50Ω
Network
analyzer

Noise-cut trans.

AC power
supply(stabilizer)

HP4395A

100

100m

0.1

Figure 1: Impedance measurement(a) Frequency axis in log scale|Z| (ohm)
1M

Probability
distribution

100k

100%(MAX)
91%(MAX)
70.8%(MAX)

10k
1k
100

70.8%(MIN)
91%(MIN)
100%(MIN)

1010.10.01

0.1

110frequency (MHz)1frequency (MHz)10|Z| (ohm)
1k1m
5m

1002m0m

100 10 20 30 40 50 60 70 80 90100
frequency (MHz)(b) Frequency axis in liner scale

Figure 2: Impedance of appliances and its dispersion. (54appliances, 89 states)

Figure 3: Inﬂuence of the lengthof AC-power-supply cord on theappliance’s impedance.

At the frequency less than 10MHz, the impedance of appliance itself is dominant. On theother hand, when higher than 10MHz, an inﬂuence of an attached AC-power-supply cord, whichmust be treated as a distributed constant circuit, becomes dominant as shown in Fig.3 (a). Thisphenomenon agrees with that of impedance-dispersion increase beyond 10MHz shown in Fig.2.
Figure 3 (a) shows the impedance of a battery charger without the AC cord and with a 1m,2m, and 5m cord, respectively. Figure 3 (b) is the same as (a), but the frequency axis is changed
to a liner scale and the highest frequency is extended from 35MHz to 100MHz. When the lengthof the cord is 0m, i.e., without the cord, the impedance is almost constant to be around 30 ohm.
However, when the cord is connected, the impedance resonates. When the cord length is 1m,
the resonance occurs once at the frequency 40MHz. When 2m, it occurs twice at the frequencies
25M and 75MHz. When 5m, it occurs ﬁve times at the frequencies 10M, 30M, 50M, 70M and90MHz. These resonance can be explained by the theory of the distributed constant circuit.
From these observations, the equivalent circuit of the appliance (in this case, the batterycharger)’s impedance is given as Fig.4. The AC cord is given as a four terminal network, denotedby Z (1) , composed of a distributed constant circuit, where γ is the propagation constant, l is thelength of the cord, and Z0 is the characteristic impedance. The appliance itself is given as a twoterminal network, denoted by Z (2) , composed of lumped constants. Then, the total impedanceof the appliance with the AC cord is given as a cascade connection of Z (1) and Z (2) . The
distributed constants of Z (1) are as follows; R=0.400[Ω/m], L=650[nH/m], G=0.600[m✵/m],
C=40.3[ρF/m]. These values are based on the result of Sec.4, and modiﬁed to ﬁt with themeasurement results.
Figure 5 compares the impedance-model given in Fig.4 with the measurement. The 0m’s
lines shows the value of Z (2) . The model values of l = 0m and 5m ﬁt well with the measuredvalues. Even when the length l is changed to 1m and 2m, they ﬁts well, where the distributed
constants are the same as those of 5m.

802191Ω

cosh γlthe diﬀerent distribution power-linefrom the outlet 1Z0 sinh γlDN

25.0 Ω 51.0 nH 66.6 nF

Figure 4: Equivalent circuit of a battery charger.

18
office 17 15
office#2 19#121162068
Lab. #3UPWC

14 5Lab. #1
22

33.60m 3.60m 3.60m 3.80m|Z| (ohm)
1k

7

1012
Lab. #2

13.0 nF

sinh γlcosh γlZ0911100 µH

7.20m

2147.20m

29.0m

measurement
model5m

Figure 6: The outlets where the line-impedance
was measured.
probability
distribution
100%(MAX)
91.0%(MAX)70.8%(MAX)50.0%(MAX)50.0%(MIN)
70.8%(MIN)
91.0%(MIN)
100%(MIN)|Z| (ohm)

100

1k
100

100m
0.1

1

10

frequency (MHz)

10100
1(a) Frequency axis in log-scale|Z| (ohm)
1k

15.20m

✷6.40mZ : AC-power-supply cord

Z(2):electricappliance6.40m 2.40m(1)◦ the same phase with the outlet 1• the opposite phase to the outlet 1

0.1
measurement
model

0.1

1

10

frequency (MHz)5m

Figure 7: Impedance property of power-line.
(24 outlets)
100

power-line
wall socket

100

noise-cuttrans.

0m
10 20 30 40 50 60 70 80 90 100
frequency (MHz)wall socket

network-analyzer
HP 4395A
1:1(b) Frequency axis in linear-scale
Figure 5: Comparison of the impedance modeland the measurement. (A battery charger)

81312.5Ω : 50Ω

50Ω : 300Ω

Figure 8: Measurement scheme of the transfer
function between two outlets.

[dB]
0[dB]
0probability
distribution
100(MAX)
90.9%(MAX)70.5%(MAX)

-20

-20
-40

-40
70.5%(MIN)
90.9%(MIN)
100(MIN)-60

0.1

70.2%(MIN)
91.4%(MIN)
100%(MIN)

-60
-80

-80

0.1

110
frequency (MHz)110
frequency (MHz)Figure 10:
Transfer function
diﬀerent-phase outlets. (47 cases)

Figure 9: Transfer function between the samephase outlets. (44 cases)

3

probability
distribution
100%(MAX)
91.4%(MAX)70.2%(MAX)betweenCharacteristics of power-line

The impedance of 24 outlets of our laboratory shown in Fig.6 was measured. The result isshown in Fig.7. The impedance of power-line, to which a lot of electric equipment are connected, changes from an increasing function to a ﬂat one, which ﬂuctuates around 40 ohm in ourmeasurement, when the frequency is higher than 2MHz. This ﬂuctuation is the same reason asshown in Fig.3.
Another diﬃculty of PLC in the low frequency-band is the signal attenuation due to thephase-coupling loss[3]. This is encountered when the communication signal must cross the opposite phase. In Japan, electric power distribution containing center tap transformers is provided
for residential use. With this type of distribution network, if two nodes on the communication
channel are on opposite phases, a cross-phase coupling device consisting of a high pass ﬁlter isoften needed. However, it is observed from Fig. 9 and Fig. 10 that the transfer function of thechannels crossing phases is almost the same as that with the same phase, when the frequency ishigher than 1MHz. It means the coupling device is not needed in the higher frequency-band. The
signal seems to transfer to the opposite phase owing to the crosstalk at the power distribution
line of 3-wire VVF cable.

4

Distributed constants of a VVF cable

Distributed constants of a VVF cable manufactured by Suganami Electric Wire Co., Ltd. wasmeasured experimentally as shown in Fig.11. The impedance of the transmitting point A andthe receiving point C are matched to the coaxial cable of 50Ω. At the branch point B, a VVF
cable is connected. The opposite end D of the VVF cable is opened, so that all signals reﬂect
with the reﬂection factor r3D = 1. At another unmatched point B, signals reﬂect and transmit
with the reﬂection factor rB and the transmission factor tB (= 1 − |rB |). The transfer faction
from A to C was measure as shown in Fig.11(b), where its theoretical value is given in [4]. The
distributed constants of the VVF cable were selected to ﬁt to the measurement result[2].
In Fig.12, the theoretical value of the transfer function |H(f )| with the VVF cable lengthl3 = 38.7m is compared to the measured value. Even when the length l3 was changed to 12.1m
and 22.7m, the theoretical value agrees with the measured value.
From Fig.13 to 15, the obtained distributed constants of the VVF cable are shown. The
relative dielectric constant εr shown in Fig.13 and the dielectric loss tan δ shown in Fig.14 are ofthe vinyl insulation of the VVF cable. They are approximated by one or two linear function(s),respectively. The inductance L of the distributed constant was obtained to be 0.52µH/m.

82
4

Dr3D
ZL3

ZL1
l1A

dielectric loss ( tanδ ( f ) )

l3
r3B
t3B

ZL2
l2

B

r1B

0.30
0.28
0.26
0.24
0.22
0.20
0.18
0.14
0.12

C

t1B

(a) Multipath signal propagation channel
Network analyzer (HP4395A)
ZD = ∞D

l1

ACB

l2eq.(b)0coaxial cable(50Ω)

l3

1020
15
frequency f (MHz)52530

Figure 14: Dielectric loss tan δ of the VVF
cable.
eq.(a): tan δ(f ) = −8.119e−9 f + 0.3041
eq.(b): tan δ(f ) = −1.872e−9 f + 0.1791

VVF(b) Measurement scheme

resistance (R ( f )) [Ω/m]
0.6

Figure 11: Measurement of distributed constants of a VVF cable.
H( f ) [dB]0-2-4-6-8-10-12-14-16
05eq.(a)

0.5
0.4
0.3
0.2

theoreticalmeasured

0.1
010 15 20 25
frequency (f) [MHz]

30

05

10
1520
frequency f [MHz]2530

2530(a) Resistance R
Figure 12: Transfer function from A to C.
(l3 = 38.7m)

capacity C[pF/m]
67.0

relative dielectric constant (εr ( f ) )66.5

3.16

66.0

3.12

65.5
3.08

65.0

3.04
3.00

64.5
100k

64.0

1M
10M
frequency f (Hz)63.5

Figure 13: Relative dielectric constant εr ofthe VVF cable.
varepsilonr (f ) = −5.733e−2 log10 f + 3.444

05

10
20
15
frequency f [MHz](b) Capacity C

83
55conductance G(f ) [m✵/m]
1.6

In this paper, the impedance characteristics ofhousehold-appliances and power-line channels are measured in the range from 75kHz to35MHz. It is measured that the dispersion of
the individual appliances’ impedance tends todecrease gradually in the range from 500kHz
to 10MHz. Beyond 10MHz, the inﬂuence of an
attached AC-power-supply cord appears, andthe dispersion changes to increase again. The
impedance of power-line changes from an increasing function to a ﬂat one, which ﬂuctuatesaround 40 ohm in our measurement, when thefrequency is higher than 2MHz. It is measured
that the transfer function of the channels crossing phases is almost the same as that with thesame phase, when the frequency is higher than1MHz.
The distributed constants of a VVF cable wereobtained. They will be used to predict powerline channel properties from its wiring conﬁguration.

1.4
1.2
1.0
0.8
0.6
0.4
0.2
005102015
frequency f [MHz]25Conclusion

30(c) Conductance G
attenuation constant α(f ) [N p/m]
0.08

0.07
0.06
0.05
0.04
0.03
0.02
0.01

References

005102015
frequency f [MHz]2530[1] S.Yamamoto, S.Tsuzuki, Y.Yamada, Measurement of characteristic on indoor
power-line channel, IEICE Technical Report, SST2000-55, 2000-12. (In Japanese)(d) Attenuation constant αcharacteristic impedance Zo(f ) [Ω]91.0[2] T.Takamatsu,
S.Tsuzuki, Y.Yamada, Measurement ofdistributed constants of VVF Cable, IEICE Technical Report, SST2000-56, 200012. (In Japanese)

90.5
90.0
89.5

[3] Phase Coupling for Power Line Communications, Intellon, Application Note No.0050,
http://www.intellon.com/docs/appnotes/
26001087.pdf.

89.0
88.5

05

1020
15
frequency f [MHz]2530(e) Characteristic impedance Z0Figure 15: Distributed constants of the VVF
cable.

846[4] M.Zimmermann, K.Dostert, A multi-path
signalpropagation model for power line channel inthe high frequency range, Proc.ISPLC’99,
pp.45-51, Mar./Apr., 1999.