Analysis of the suppression method of lightning electromagnetic pulse coupled by receivers

Abstract

In this paper, we proposed an approach to suppress the lightning electromagnetic pulse for receiver by utilizing lightning protection device. The equivalent circuit model of the antenna in receiving state together with the lightning protection device is established for both theoretical and numerical analysis. The combination wave generator (CWG) was used to generate 8/20 $\mu$ s current injected into the return stroke channel, and the induced overvoltage and energy distribution the lightning electromagnetic wave coupled by receivers have been analyzed. Results illustrate that the induced lightning overvoltage can be well suppressed by using the proposed circuit, and the additional circuit has little effect on the performance of the antenna. The experimental results have good agreement with that of the theory of equivalent circuit.

Keywords

Receiver suppress lightning electromagnetic pulse lightning protection device

1. Introduction

The lightning electromagnetic pulse (LEMP) can cause serious damages to the electronic devices as it operates within very wide-band frequency regime and large energy level. So the research on the suppression of the LEMP in electronic systems, especially for the large-scale integrated circuits which operate in very low power state and is very sensitive to LEMP, has attracted great attentions in recent years [1, 2, 3]. Transient Voltage Suppression (TVS) is a semiconductor protection component which is widely used. The ideal protection component must have features of quick response and low break-over voltage, as well as the ability to absorb surge energy. When a TVS is loaded with high impact current, its impedance decreases immediately (in dozens of micro-microseconds). Meanwhile, the energy is absorbed and, converted into thermal energy, keeping voltage between both the ends of the TVS at a predetermined value. Thus it can protect circuit elements from being impacted by transient high energy [4, 5, 6, 7].

Receiver is a circuit system consisting of an antenna, a filter, an amplifier and a A/D converter. Antenna is one of the essential parts of a radio system, such as the communication basic stations for broadcast and mobile communications, navigation, radar, measurement and control, microwave remote sensing, radio astronomy and electronic counter-measure [8]. When a lightning occurs, LEMP is generated by lightning channels and can be coupled to receiver. Due to the features of high energy and wideband frequency, the induced overvoltage caused by LEMP that the receiver couples can cause damages of the antenna amplifier circuit devices in receiver [9]. At present, Qin analyzed the mathematical model of the lightning electromagnetic pulse and concluded that, under the interference of lightning electromagnetic pulse, the coupling energy of the antenna port is large enough to interfere with or damage the receiver [10]. For the serious threat that electromagnetic pulse causes by coupling with high energy into the radar system through the antenna, cable, apertures and so on, Zhen gave the antenna coupling formula of radars, and finally proposed the measures of anti-EMP [11]. Wang investigated the electromagnetic interference for the airborne equipment when the LEMP energy is coupled to a shortwave antenna that is connected to the equipment [12]. A grounding scheme for electrical and electronic installations is proposed by Darwanto to prevent and minimize risks caused by the antenna that may be induced with high LEMP energy [13]. In order to protect the subsequent equipment from the damage of lightning over-voltage, Furukawa proposed a method of installing surge protector between antennas and the subsequent equipment [14]. Hasse has made a typical research results in the suppression of lightning electromagnetic pulse, and participated in the development of IEC standards for lightning protection of electrical and information systems [15]. In view of the problem of propagation and suppression method of lightning wave in coaxial line, Li concluded that the GDT will become a reflector when the lightning wave go through it and part of the wave will be reflected. Part of the energy of the lightning wave will be discharged by GDT and only a little of the energy will be absorbed by the load [16]. Up to date, none of these literatures pay attention to the suppression of the lightning electromagnetic wave energy coupled by receivers. According to the principle of the lightning electromagnetic wave coupled by receivers and combining it with the experimental data, this paper presents a solution that using protection devices that are respectively TVS, low capacitance TVS diode array and TVS array to restrain the LEMP coupled by receivers.

2. Electromagnetic field generated by lightning discharge

2.1 Electromagnetic field of lightning discharge

The process of lightning discharge is shown in Fig. 1a [17].The thundercloud with negative charge generates leader towards to the ground, combining with the positive charge upward leader generated by the ground when it arriving at the nearby ground, leading neutralization of the thundercloud negative charge, and forming the main discharge. The main discharge channel develops from the ground to the thundercloud at the speed of $v$ , about 1/20 $\sim$ 1/2 of the speed of light. When lightning strikes the ground near a transmission line, the electromagnetic field will induce an overvoltage on the wire. In the pilot stage of the lightning discharge, the wire is in the electric field excited from thundercloud, leader channel and ground. Due to electrostatic induction, a horizontal wire will attract positive charges (different from thundercloud charges) in the central part, thus forming bound charge. Negative charges on the wire are excluded to move towards both sides of the wire, and then flow into the earth through line leak conductance and system neutral point. Because of the relatively slow average speed of leader discharge, the aggregation process of conductor bound charges is slow, the presented conductor current is really small. We generally do not consider the space electromagnetic field forming in leader stage.

Figure 1b shows the process of positive lightning discharge. Main discharge with positive charges has an upward progress, but there is no neutralization of negative lightning discharge.

Figure 1.

Thundercloud discharge process. (a) Negative lightning discharge model; (b) Positive lightning discharge model.

The process of negative lightning discharge is shown in Fig. 1a. The lightning current of the main lightning channel will produce a vector potential ${A}$ . Meanwhile, residual charges of the leader channel will also generate a scalar potential $\phi$ . The whole space incident electric field generated by them can be expressed as:

${{\bf E}}^{i}={{\bf E}}_{e}^{i}+{\rm{\bf E}}_{m}^{i}=-\nabla\phi-\frac{% \partial{\rm{\bf A}}}{\partial t}$ (1)

While for the process of positive lightning discharge as shown in Fig. 1b, the lightning current of the main discharge channel generates the vector potential ${{\bf A}}$ , and the charges within the main discharge channel generate the scalar potential $\phi$ .

Figure 2.

Magnetic field model produced by lightning discharge channels finite line current.

2.2 Electromagnetic wave radiated by lightning channel

In Fig. 2, assuming the lightning current is $i(t)$ , the distance between the current element $idz^{\prime}$ of source point ${P}$ and field point $Q$ is

$r_{PQ}=\sqrt{(z-z^{\prime})^{2}+r^{2}}$ (2)

Supposing vector magnetic potential is

$\displaystyle A_{Z}=\frac{\mu_{0}i}{4\pi}\int_{-l\mathord{\left/{\vphantom{l2}% }\right.\kern-1.2pt}2}^{l\mathord{\left/{\vphantom{l2}}\right.\kern-1.2pt}2}{% \frac{dz^{\prime}}{\sqrt{(z-z^{\prime})+r^{2}}}}=\frac{\mu_{0}i}{4\pi}\ln\left% ({\frac{-z+l\mathord{\left/{\vphantom{l2}}\right.\kern-1.2pt}2+\sqrt{(z-l% \mathord{\left/{\vphantom{l2}}\right.\kern-1.2pt}2)+r^{2}}}{-\left({z+l% \mathord{\left/{\vphantom{l2}}\right.\kern-1.2pt}2}\right)+\sqrt{(z+l\mathord{% \left/{\vphantom{l2}}\right.\kern-1.2pt}2)+r^{2}}}}\right)$ (3)

Where: $\mu_{0}=4\pi\times 10^{-7}$ , representing permeability of vacuum. The magnetic induction intensity in the field is

$\displaystyle\vec{B}=\nabla\times A_{z}=\left({\frac{1}{r}\frac{\partial A_{z}% }{\partial\phi}\frac{\partial A_{\phi}}{\partial\phi}}\right)i_{r}+\left({% \frac{\partial A_{r}}{\partial z}\frac{\partial A_{z}}{\partial r}}\right)+% \frac{1}{r}\left({\frac{\partial}{\partial\phi}\left({rA_{\phi}}\right)\frac{% \partial A_{r}}{\partial\phi}}\right)i_{z}=\frac{\partial A_{z}}{\partial r}i_% {\phi}=\frac{\mu_{0}i}{4\pi r}\left({\frac{-z+l\mathord{\left/{\vphantom{l2}}% \right.\kern-1.2pt}2}{\sqrt{(z-l\mathord{\left/{\vphantom{l2}}\right.\kern-1.2% pt}2)^{2}+r^{2}}}+\frac{z+l\mathord{\left/{\vphantom{l2}}\right.\kern-1.2pt}2}% {\sqrt{(z+l\mathord{\left/{\vphantom{l2}}\right.\kern-1.2pt}2)^{2}+r^{2}}}}% \right)i_{\phi}$ (4)

When the magnetic tape is far less than the length of the lightning channel (such as lightning conductor, down conductor, lightning protecting wire, transmission tower and communication, control cables), lightning channel can be regarded as “infinite length” current-carrying straight wire, namely

$\displaystyle\mathop{\lim}\limits_{l\to\infty}\vec{B}=-\frac{\partial A_{z}}{% \partial r}i_{\phi}=\frac{\mu_{0}i}{2\pi r}i_{\phi}$ (5)

The magnetic field intensity $H$ a round the lightning current $i(t)$ channel is

$\displaystyle H=\frac{B}{\mu_{0}}=\frac{i(t)}{2\pi r}$ (6)

2.3 Receiver internal antenna

The working process of the receiver is the inverse process of the transmitter, and its basic task is to receive the electromagnetic wave coming from the air and restore it to the original signal, which has the function of amplification and matching filtering.

In this paper, we only discuss the part of the receiver from the antenna to the low noise amplifier circuit, which is shown in Fig. 3a. In order to protect the antenna follow-up equipment, the lightning protective device was welded between the amplifier circuit and the feed port of the antenna. The schematic diagram is shown as Fig. 3b. Considering the antenna and protection device as a whole, we need to ensure that installing the protective devices does not affect the normal transmission of the signal received by the receiver.

Figure 3.

Antenna part of the receiver. (a) Without lightning protection device; (b) Adding lightning protection device at the feed end of receiversâ€™ antenna.

Inside the protective device, different lightning protection devices are parallel connected. Figure 4 shows the circuit structures. In Fig. 4a, the lightning protection device is Transient Voltage Suppressor (TVS), a rectifier bridge structure, because it can reduce the distributed capacitance of TVS. The TVSs are P6KE6.8A and P6KE12A, whose operation voltage are 6.8 V and 12 V respectively; In Fig. 4b, the lightning protection device is low capacitance TVS diode array, whose model is SR05 and action voltage is 5 V; The lightning protection device is array of transient voltage suppressor whose model is slvu2.8-4 as shown in Fig. 4c, which has four pairs of pins, representing as 1, 2; 3, 4; 5, 6; 7, 8, respectively. They are independent of each other, and any pair can be used as well.

Figure 4.

The internal circuit diagrams of protective devices. (a) The lightning protection device is TVS; (b) The lightning protection device is R05; (c) The lightning protection device is array of transient voltage suppressor slvu2.8-4.

2.4 Theory of receiving antenna

The physical process of antenna receiving electromagnetic energy can be conducted as follows: Induction electromotive force is aroused on a receiving antenna under the external field, and generate current on the surface of conductor. The current transmits into the load $Z_{L}$ (receiver), and to power the receiver circuit. Therefore, the receiving antenna is an energy conversion device that converts the energy of space electromagnetic wave into the high frequency current energy, whose working process is exactly the inverse process of transmitting antenna, as shown in Fig. 5.

Figure 5.

Schematic diagram of antenna reception.

The receiving antenna generally locates in the far-field zone of the transmitting antenna. In far-field zone, the radiated spherical transverse wave by transmitting antenna can be regarded as plane wave on a local surface [18, 19]. Therefore, the receiving antenna is usually regarded to be excited by a plane wave source.

Assuming the angle between direction of arrival (DOA) and the included angle of dipole is $\theta$ , and the wave electric field $E^{\prime}$ can be decomposed into two components $E^{\prime}_{1}$ and $E^{\prime}_{2}$ . When $E^{\prime}_{2}$ is perpendicular to the dipole, it will not work, only when $E^{\prime}_{1}=E^{\prime}_{2}=E^{\prime}\sin\theta$ , will oscillator make induced current, producing scattered field $E_{s}(I)$ (a function which definite the induced current $I$ as an unknown).

The receiving antenna also can be regarded as a voltage source, and it is substituted as an equivalent voltage generator. When the voltage source is in a short-circuit state, corresponding to the free wave field, internal resistance looked from the external circuit is called as the receiving antenna impedance, and expressed as $Z_{in}=R_{in}+jX_{in}$ . The equivalent circuit of the receiving antenna is shown in Fig. 6a, where Z ${}_{L}$ is the loaded impedance and expressed as $Z_{L}=R_{L}+jX_{L}$ , and $E^{\prime}$ is the component of the incident electric field on the polarization direction when the antenna is emitted. When $Z_{L}$ and $Z_{in}$ is in conjugate matching state, that is

$\displaystyle Z_{L}=Z_{in},\left\{{\begin{array}[]{l}R_{L}=R_{in}\\ X_{L}=-X_{in}\\ \end{array}}\right.$ (7)

The antenna output current is expressed as follows:

$\displaystyle I_{in}=\frac{U}{Z_{in}+Z_{L}}=\frac{L_{e}E^{\prime}F(\theta,% \varphi)}{Z_{in}+Z_{L}}=\frac{L_{e}E^{\prime}F(\theta,\varphi)}{2R_{in}}$ (8)

The received power is:

$\displaystyle P_{re}(\theta,\varphi)=\frac{1}{2}\left|I\right|^{2}R_{L}=\frac{% 1}{2}\frac{(L_{e}E^{\prime})^{2}}{4R_{in}}F^{2}(\theta,\varphi)$ (9)

Figure 6b is the equivalent circuit where TVS is parallel installed on the feed port of the antenna. Figure 6c illustrates the state that suppressor is out of work, where the capacitor C is the distribution capacitor of the suppressor. Figure 6d indicates that the suppressor acts, where the resistance R is the equivalent resistance as the suppressor works with a nonlinear voltage-current diagram.

Under a conjugate matching condition, if the main direction of receiving antenna is in the same direction as DOA ( $F(\theta,\phi)=$ 1), and the polarization is also consistent ( $E^{\prime}=E_{i}$ ), the receiver would obtain the maximum received power:

$\displaystyle P_{re\max}=\frac{1}{2}\frac{(L_{e}E^{\prime})^{2}}{4R_{in}}$ (10)

Figure 6.

Equivalent circuits of the receiving antenna. (a) Without protector; (b) Adding protector; (c) The protector is out of work; (d) The protector works.

3. Analysis on experimental results and data

3.1 The setup of the experiment

The whole experimental setup was placed above a conducting plane. The ground was assumed as a perfect conductor. The return stroke channel was mimicked by a copper conductor wounded on an insulating rod in such a way that the propagation velocity of the current along the channel was about 11% of that of light in free space. Local restrictions have limited the height of the stroke channel model to 12 m. The number of turns was approximately 323 per meter of rod length and the diameters of the copper conductor and of the insulating rod were 0.7 mm and 25.4 mm, respectively. The value of surge impedance for the return stroke channel model was 2.2 k $\Omega$ . Thus, for the elimination of reflections, a non-inductive resistor of 2.2 k $\Omega$ was connected between the top of the stroke channel model and the mesh of conductors that provided the current return path, as shown in Fig. 7. The return conductors were separated by a distance of about 1 m. Therefore, the electromagnetic field in the region was established by the current along the return stroke channel model (R.S.M.) [20].

For the model, the front time of the simulated stroke current must be about 60 ns. Moreover, the current amplitude must be of the order of at least a few amperes in order to enable the study of the effect of surge arresters. Thus, a high-voltage cable, 280 m long, charged by a direct current (DC) voltage source, was used to generate such a current. Once the desired voltage was reached, the cable was connected by a high-speed switch to the R.S.M. As the circuit impedance was predominantly resistive, currents of relatively short front times could be generated.

Combination waveform (CW), whose virtual resistance is 2 $\Omega$ , is characterized by 1.2/50 $\mu s$ open circuit voltage wave and 8/20 $\mu s$ short circuit current wave. The combination wave generator (CWG) was used to generate 8/20 $\mu s$ current injected into the R.S.M. and the current was measured at ground level by a current probe associated with an amplifier [21]. The receiver was respectively placed at 5 m, 10 m and 15 m from the return stroke channel to couple the simulated lightning electromagnetic pulse. The induced voltage was measured by a digital storage oscilloscope (DSO). A schematic diagram of the experimental setup is presented in Fig. 7.

Finally, disposing the signal of voltage wave collected to the feed end of internal antenna of receivers and antennas paralleling with various suppressors respectively, we can obtain the voltage amplitude and energy that the receivers couple lightning electromagnetic pulse. Furthermore, the S ${}_{11}$ curves of internal antenna of receivers needed to be measured by a network analyzer E5071C before carrying out the experiment.

3.2 Measuring the return loss of the internal antenna of receivers

S ${}_{11}$ indicates the input reverse coefficient, namely the input return loss (Loss Return, RL), RL $=$ $-$ S ${}_{11}$ , so we can reflect RL through the S ${}_{11}$ parameters of antennas.

Five different receivers are used in the experiments, whose internal antennas operate at frequencies of 315 MHz, 433 MHz, 0.8 GHz, 2.4 GHz and 4 GHz, respectively. The S ${}_{11}$ curves of each antenna are measured by E5071C network analyzer. The S ${}_{11}$ parameters of the antennas loaded with and without TVS are listed in Table 1. From the table, the center frequency and bandwidth are slightly reduced with a TVS loaded.

Table 1
The S ${}_{11}$ parameters of the internal antenna of receivers

Categories	Center frequency (GHz)	Bandwidth (MHz)
315 MHz not paralleling TVS	0.313	16.5
315 MHz paralleling TVS	0.310	13.3
433 MHz not paralleling TVS	0.425	25.2
433 MHz paralleling TVS	0.413	19.5
0.8 GHz not paralleling TVS	0.886	124.8
0.8 GHz paralleling TVS	0.881	113.2
2.4 GHz not paralleling TVS	2.430	266.9
2.4 GHz paralleling TVS	2.412	231.1
4 GHz not paralleling TVS	4.126	317.3
4 GHz paralleling TVS	4.096	278.6

Figure 7.

Schematic diagram of the experimental setup.

S ${}_{11}$ curves of the internal antenna of receivers are shown in Fig. 8 before and after the parallel connection of TVS. We can see that the TVS has little impact on the S ${}_{11}$ of the antenna, where the center frequency moves to lower frequency and bandwidth are slightly narrowed.

Figure 8.

S ${}_{11}$ curves of the antennas. (a) 315 MHz; (b) 433 MHz; (c) 0.8 GHz; (d) 2.4 GHz; (e) 4 GHz.

3.3 Analysis of the electromagnetic wave characteristics of receivers under different conditions

3.3.1 Influence on electromagnetic interference before and after 315 MHz antenna paralleling slvu2.8-4

Figures 9a and b reveal that the induced peak voltage and energy varies with the source impulse current where the internal antenna of receiver operating at 315 MHz is load with and without slvu2.8-4. Figure 9a illustrates a comparison of the peak voltage at 15 m from radiation source. Based on the experimental results, we can find that, with the increase of impulse current, the peak voltage caused by the coupling of lightning electromagnetic wave increases approximately linearly, indicating that the depressing effect is enhanced. In Fig. 9b, the induced energy is compared when the receiver is located at 10 m from radiation source. The vertical coordinate indicates the induced energy of the receiver coupling to lightning electromagnetic wave. It is not difficult to see from the figure that impulse current varies from 5 kA to 40 kA and the energy that the simulated lightning electromagnetic wave coupled by the receiver also increases gradually; without the lightning protection device, it is roughly presented as an exponential growth trend. With the load of slvu2.8-4, the induced energy nearly keeps unchanged, and the energy curve is approximately a straight line, which verifies that suppression device has a good restraining of the induced voltage.

Table 2 indicates the peak voltage and energy before and after the internal antenna of receiver is load with a slvu2.8-4. When there is no lightning protection device, the range of the voltage amplitude is 1.6 $\sim$ 16.8 V, and when the lightning protection device is installed, the induced voltage ranges from 0.9 V to 11.4 V. It is found that the energy reduces in two orders of magnitude compared with that there is no lightning protection device, indicating that the restrained effect is quite obvious.

Table 2
Voltage peak and energy before and after a slvu2.8-4 is parallel setup to the receiver antenna with its working frequency at 315 MHz

Impulse current (kA)	Voltage (V)		Energy (J)
	No suppressors	slvu2.8-4	No suppressors	slvu2.8-4
5	1.6	0.9	4.64E-05	7.27E-07
10	3.6	1.2	6.26E-05	1.84E-06
15	4.4	1.1	1.04E-04	3.80E-06
20	7.2	2.4	1.82E-04	6.43E-06
25	9.4	4.6	3.61E-04	9.27E-06
30	10.8	6.4	6.12E-04	1.26E-05
35	14.8	8.6	9.06E-04	1.65E-05
40	16.8	11.4	1.36 E-03	2.20E-05

Figure 9.

The induced peak voltage and energy varies with the source impulse current where the receiver antenna operating at 315 MHz is load with and without slvu2.8-4. (a) Voltage peak at 15 m away from radiation source; (b) Energy at 10 m away from radiation source.

The following example is used to illustrate the working situation of the antenna follow-up equipment for installing protective devices.

The center frequency of the receiver antenna is 315 MHz, and the amplifier chip is XN255, CLC425 and ATR4251, respectively. XN255 is a low noise amplifier chip, whose working voltage range is 2.7 V $\sim$ 3.3 V, when the supply voltage is 3.3 V, the insulation voltage is 7 V; CLC425 is an operational amplifier, whose operating voltage range is $-$ 5 V $\sim$ $+$ 5 V, when the service voltage is 5 V, the isolation voltage is 11 V; ATR4251 is a low noise antenna amplifier, whose voltage range is 8 V $\sim$ 11 V, when the supply voltage is 8 V, insulation voltage is 16.8 V. Under different impact current and distances from the radiation source, the working situation of the first stage amplifier circuit of the receiver is shown in Table 3.

Table 3

The working condition of the amplifier chip under different impulse current

Impulse	5 m			10 m			15 m
current (kA)	XN255	CLC425	ATR4251	XN255	CLC425	ATR4251	XN255	CLC425	ATR4251
6	N	N	N	N	N	N	N	N	N
9	N	N	N	N	N	N	N	N	N
12	N	N	N	N	N	N	N	N	N
15	N	N	N	N	N	N	N	N	N
17	D	N	N	N	N	N	N	N	N
18.5	–	N	N	D	N	N	N	N	N
19.8	–	N	N	–	N	N	D	N	N
24	–	D	N	–	N	N	–	N	N
27	–	–	N	–	D	N	–	N	N
33	–	–	N	–	–	N	–	D	N
35.6	–	–	D	–	–	N	–	–	N
37	–	–	–	–	–	D	–	–	N
40	–	–	–	–	–	–	–	–	D

a. N indicates normal, D indicates damaged.

In Table 3, with the increase of impact current, the induced voltage coupled by receivers increases. When the induction voltage exceeds the insulation voltage of first stage amplifier circuit, chip is damaged. Due to the induced voltage is very high, it is easy to go beyond insulation pressure level of chips. Installing protection devices between the internal antenna of receivers and the first stage amplifier circuit can inhibit the induction voltage to a very low level, making the chip work normally under the impact current, thus the receiver following equipment can be well protected. The result indicates that adding lightning protection devices between the receiver antenna and the follow-up equipment has a good protective effect.

3.3.2 Influence of the coupling distance on electromagnetic interference of the receiver

Figures 10a and b illustrate the peak voltage and induced energy of the receiver that is parallel setup with lightning protection device in distances of 5 m, 10 m and 15 m. Figure 10a shows the peak voltage where a slvu2.8-4 is parallel setup to the internal antenna of receiver with its working frequency at 0.8 GHz. It can be seen from the curve that, with the increase of the impulse current, the voltage peak caused by the coupling of electromagnetic wave increases. The induced voltage value changes with the distance variation of the receiver from the radiation source. The closer to the radiation source, the greater the voltage value is; the farther away from the radiation source, the smaller the voltage value is, and this drift becomes more obvious when we increase the impulse current. Comparing with Figs 9a and 10a, we can see that the smaller the center frequency of the internal antenna of receiver is, the higher the induced voltage peak value is, and the converse is also true.

Figure 10b depicts the energy comparison chart that the internal antenna of receiver is set up with and without a SR05 and the antenna is work at 433 MHz. Seeing from the figure, it can be found that, with the increase of the impulse current, the induced energy of the receiver caused by coupling of lightning electromagnetic wave is also increasing. The induced energy varies with the distance changing from the radiation source. When the distance from the radiated source is 15 m, the coupling energy becomes very small, and with the increase of the impact voltage, the energy changes slightly.

Table 4 shows the peak value and energy at different distances that slvu2.8-4 and SR05 are parallel installed on the internal antenna of receiver with operating frequency of 0.8 GHz. Under the same impulse current, the farther away from the radiation source, the smaller voltage amplitude and energy are; when the distance keeps unchanged, with the increase of the impulse current, the coupling voltage amplitude and energy are larger, too.

Table 4
Voltage peak and energy when slvu2.8-4 and SR05 are parallel installed on the receiver antenna operating at 0.8 GHz at different distances

Impulse current	Peak value after 0.8 GHz antenna			Energy after 0.8 GHz antenna
(kA)	adding slvu2.8-4 (V)			adding SR05 (J)
	5 m	10 m	15 m	5 m	10 m	15 m
5	0.62	0.46	0.36	5.78E-07	3.84E-07	4.25E-08
10	1.04	0.72	0.48	1.48E-06	1.16E-06	9.64E-08
15	1.46	0.92	0.62	3.49E-06	2.46E-06	2.48E-07
20	1.86	1.24	0.86	6.28E-06	3.87E-06	3.86E-07
25	2.42	1.56	1.18	9.01E-06	5.46E-06	5.68E-07
30	2.96	1.92	1.46	1.12E-05	7.36E-06	7.66E-07
35	3.54	2.54	1.82	1.43E-05	9.48E-06	9.35E-07
40	4.36	3.22	2.26	1.74E-05	1.16E-05	1.56E-06

Figure 10.

The peak voltage and induced energy of the receiver antennas that is parallel setup with suppression device in distances of 5 m, 10 m and 15 m. (a) The peak voltage where a slvu2.8-4 is parallel setup to the receiver antenna with its working frequency at 0.8 GHz; (b) The energy that the receiver antenna, working at 433 MHz, is set up with and without a SR05.

3.3.3 Influence of the coupling receiver antenna type on electromagnetic interference

When lightning protection device is parallel setup to different types of receiver antennas, the comparison diagrams of the induced voltage peak and energy are shown in Fig. 11. Figure 11a reflects peak voltage that the receiver antennas are parallel setup with slvu2.8-4. We can see that from the curve, with the increase of the impulse current, the voltage peak value caused by the coupling of electromagnetic wave is increasing. The induced voltage value of each receiver antenna changes with the lightning protection device. The smaller the center frequency of the receiver antenna is, the bigger the induced voltage peak value is, and the larger the center frequency is, the smaller the voltage peak value is. Figure 11b indicates the energy value that SR05 is parallel installed on each receiver antenna. In the figure, with the increase of the impulse current, the energy value of the antenna caused by the coupling of electromagnetic wave is also increasing, what’s more, the induced voltage amplitude and energy caused by the coupling of electromagnetic wave increase linearly with the decreases of the center frequency. This is because the lightning current is mainly distributed in the low-frequency part, and decreases with the increase of frequency.

Table 5 indicates the peak value that each receiver antenna is parallel setup with slvu2.8-4 at 10 m, and Table 6 shows the energy which each receiver antenna is parallel setup with SR05 at 10 m. We can obtain that from Tables 5 and 6, when the impulse current is certain, the higher the center frequency of the internal antenna of receiver is, the smaller the coupling voltage amplitude and energy are; when the center frequency of the receiver antenna is constant, with the increase of impulse current, the coupling voltage amplitude and energy are greater.

Table 5
Voltage peak that receiver antenna is parallel setup with slvu2.8-4 at 10 m (V)

Impulse current (kA)	315 MHz	433 MHz	0.8 GHz	2.4 GHz	4.0 GHz
5	1.48	1.26	0.92	0.74	0.54
10	1.72	1.48	1.14	0.88	0.68
15	2.12	1.76	1.42	1.16	0.82
20	2.58	2.18	1.78	1.36	0.98
25	3.14	2.52	2.08	1.62	1.16
30	3.66	3.02	2.46	1.94	1.38
35	4.28	3.54	2.88	2.26	1.72
40	4.96	4.26	3.36	2.64	2.12

Figure 11.

The comparison diagrams of the induced voltage peak and energy when suppression device is parallel setup to different receivers’ antenna at 10 m. (a) The comparison of voltage peak after paralleling slvu2.8-4; (b) The comparison of energy after installing SR05.

3.3.4 Influence of the suppression device on electromagnetic interference of the receiver

Figure 12a displays the voltage peak that the receiver antenna with its operating frequency at 2.4 GHz is setup with and without various suppression devices at 10 m from the source. Based on the figure, when without any lightning protection devices, the coupling voltage peak of the receiver in 10 m varies from 1.12 V to 5.7 V; while the peak voltage of which is basically below than 2 V with the load of lightning protection devices. Compared to several other lightning protection devices, P6KE12A can suppress voltage to a lower level.

Figure 12b depicts energy comparison chart that the internal antenna of receiver is setup with and without various lightning protection devices at 15 m from the source and the antenna is work at 4 GHz. As without any lightning protection devices, the coupling energy of the receiver at 15 m changes from 2.78E-6 to 1.26E-4. Figures 12c and d are respectively the magnification of Figs 12a and b after the parallel connection of all lightning protection devices, because the two figures clearly show inhibitory effect after adding the lightning protection devices. Adding lightning protection devices can reduce the energy by 2 $\sim$ 3 magnitudes, in which the restrained effect of P6KE12A is more evident.

Figure 12.

Influence of the lightning protection device on electromagnetic interference of the receiver antenna at 10 m and 15 m respectively. (a) The induced voltage peak that the receiver antenna with its operating frequency at 2.4 GHz is setup with and without various lightning protection devices at 10 m; (b) Energy that the receiver antenna is setup with and without various lightning protection devices at 15 m and the antenna is work at 4 GHz; (c) The magnification of Fig. 12a after the parallel connection of all lightning protection devices; (d) The magnification of Fig. 12b after installing a variety of lightning protection devices.

At 10 m from the radiation source, the induced voltage peak values that the receiver antenna operating at 2.4 GHz is set up with various lightning protection devices are listed in Tables 7 and 8 shows the energy that a variety of lightning protection devices are parallel installed on the receiver antenna with its working frequency at 4 GHz. In Tables 7 and 8: when the impulse current is constant, the induced voltage amplitude and energy that the receiver antenna is parallel setup with various lightning protection devices are smaller than that there is no lightning protection device, which reflects that installing lightning protection device can has a good inhibitory effect. Among the four kinds of lightning protection devices, the latter two TVSs have better inhibitory effect, and the inhibitory effect of P6KE12A is better than P6KE6.8A, which indicates that the greater the action voltage of TVS is, the better the inhibitory effect is.

Table 6

Voltage peak that SR05 is parallel installed on receiver antenna at 10 m (J)

Impulse current (kA)	315 MHz	433 MHz	0.8 GHz	2.4 GHz	4.0 GHz
5	1.46E-07	1.28E-07	7.70E-08	5.78E-08	2.48E-08
10	2.47E-07	1.63E-07	1.22E-07	1.02E-07	3.48E-08
15	4.00E-07	3.07E-07	2.26E-07	1.95E-07	7.36E-08
20	6.28E-07	4.95E-07	3.82E-07	3.21E-07	1.32E-07
25	8.29E-07	7.11E-07	5.09E-07	4.32E-07	1.90E-07
30	1.08E-06	9.32E-07	7.02E-07	5.85E-07	2.83E-07
35	1.38E-06	1.15E-06	8.93E-07	7.19E-07	3.61E-07
40	1.68E-06	1.37E-06	1.09E-06	8.69E-07	4.19E-07

Table 7

Voltage peak that the internal antenna of receiver working at 2.4 GHz is setup with and without various suppressors at 10 m (V)

Impulse current (kA)	No suppressors	slvu2.8-4	SR05	P6KE6.8A	P6KE12A
5	1.12	0.26	0.22	0.12	0.10
10	1.76	0.46	0.36	0.22	0.14
15	2.72	0.62	0.54	0.34	0.24
20	3.44	0.84	0.72	0.48	0.36
25	4.16	1.04	0.90	0.66	0.50
30	4.60	1.22	1.10	0.82	0.68
35	5.10	1.44	1.28	0.98	0.88
40	5.70	1.70	1.52	1.14	1.02

Table 8

Energy that the receiver antenna with its operating frequency at 4 GHz is set up with and without various suppressors at 10 m (W)

Impulse current (kA)	No suppressors	slvu2.8-4	SR05	P6KE6.8A	P6KE12A
5	2.78E-06	4.98E-08	4.21E-08	3.60E-08	2.48E-08
10	6.06E-06	6.02E-08	4.95E-08	4.40E-08	3.48E-08
15	1.55E-05	1.21E-07	9.64E-08	8.20E-08	7.36E-08
20	2.54E-05	2.36E-07	1.69E-07	1.48E-07	1.32E-07
25	4.52E-05	3.18E-07	2.65E-07	2.16E-07	1.90E-07
30	6.12E-05	5.01E-07	4.12E-07	3.24E-07	2.83E-07
35	9.13E-05	6.15E-07	5.24E-07	4.01E-07	3.61E-07
40	1.26E-04	8.64E-07	7.15E-07	5.61E-07	4.19E-07

In summary, the induced voltage amplitude and energy caused by the coupling of lightning electromagnetic wave cause certain damage to the receiver internal antenna amplifier circuit. Lightning protection device can effectively restrain the induced voltage and energy. In practical application, parameters need to be considered such as center frequency and bandwidth, which also change accordingly after the antenna feed port is loaded with lightning protection devices. Therefore, it is necessary to take the distribution parameters of the lightning protection device into account. The lightning protection device and internal antenna of receiver should be designed as a whole.

4. Conclusions

In this paper, the electromagnetic interference caused by the LEMP for receiver is investigated and corresponding suppressing schemes have been presented by utilizing the TVS. The performances of different experimental setups under different conditions are demonstrated in laboratory. Some conclusions can be down as follows:

Under the same impulse current, the internal antenna of receiver is parallel setup with the same lightning protection device. The farther away from the radiation source, the smaller the voltage amplitude of the coupling waveform is, and the suppression effect is weakened. When the distance is certain, the bigger the impulse current is, the more distinct the inhibitory effect is.

The induced voltage amplitude and energy caused by the coupling of electromagnetic wave increase linearly with the decreases of the center frequency. Such as the receiver antenna operating at 315 MHz, when it installing lightning protection device, the voltage amplitude and energy are evidently suppressed.

The coupling energy reduces in two orders of magnitude compared with there is no lightning protection device. In addition, P6KE12A has the most obvious restrained effect among the four lightning protection devices.

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