JP2012105155A - Weak electric wave transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a weak radio wave transmitter capable of eliminating a peak exceeding a specific level for an OFDM signal and adapting to a sudden change in instantaneous transmission power.
An amplitude limit circuit 3 for inputting an OFDM signal and outputting a signal obtained by cutting a waveform portion exceeding the peak value of the input signal waveform exceeding a specific value, and an output of the amplitude limit circuit 3 A gain changing circuit 4 for increasing / decreasing the gain, and a control circuit 6 for controlling the gain of the gain changing circuit 5 based on the amplitude limiting level information of the amplitude limiting circuit 3. The control circuit 6 transmits weak radio waves to the amplitude limiting level. The gain changing circuit 5 is controlled so that the peak power of the signal transmitted by the apparatus is constant.
[Selection] Figure 1

Description

  The present invention relates to a weak radio wave transmission device that transmits an RF signal, and more particularly to a weak radio wave transmission device that transmits an OFDM signal with a predetermined electric field strength or less.

  With the widespread use of mobile terminals that can receive 1Seg broadcasting, services that provide information by implementing 1Seg broadcasting independently for specific narrow areas are being studied. Such broadcasting can be easily carried out using weak radio waves that do not require a license. In this case, for example, a large number of antennas are installed at a predetermined interval of several meters.

For example, in Patent Document 1, a transmitter and a repeater are provided, and a radio wave having a frequency lower than the frequency of one-segment broadcasting is output by the transmitter with relatively large power, and the radio wave is received by the repeater and converted to the frequency of one-segment broadcast. By reconverting and outputting, one-segment broadcasting can be received in areas where radio waves do not reach or in specific areas.
However, the radio wave output by re-conversion here is a weak radio wave that does not require a license in the range of 322 MHz to 10 GHz, and is controlled so that the transmission power does not increase using an AGC circuit.

Note that the weak radio waves that do not require a license here are radio waves that are excluded from the license subject to the Radio Law, and in the frequency band (470 to 710 MHz) used for one-segment broadcasting, a distance of 3 meters from the radio station. The electric field strength is a radio wave having a peak value of 35 μV / m or less.
One-segment broadcasting refers to a broadcasting service that uses one segment for mobile phones and mobile terminals among the 14 OFDM segments used for one channel of terrestrial digital television broadcasting.

JP 2010-93542 A

The Journal of the Institute of Image Information and Television Engineers Vol.55, No.7 “Examination of C / N improvement in multistage transmission of digital terrestrial television relay equipment”

  Since one-segment broadcasting uses OFDM signals, the peak power of the signal waveform is larger than the average transmission power. Since a weak radio wave is defined by a peak value, a transmission device that satisfies the condition of the weak radio wave needs to reduce the average transmission power by an amount corresponding to the ratio of the peak power to the average transmission power. As a result, there is a problem that reducing the average transmission power reduces the receivable area, or the receivable area becomes narrow, which increases the number of transmitters per unit area and increases installation costs. There is a problem in that the convenience of users who receive one-segment broadcasting using weak radio waves is reduced.

  Since one-segment broadcasting uses OFDM signals, the instantaneous transmission power of the signal waveform changes steeply, and if the AGC circuit tries to limit the peak value of instantaneous transmission power that changes sharply, the time constant is shortened, The response needs to be fast. However, when the time constant of the AGC circuit is shortened, the following problem occurs.

FIG. 13 shows an example of the AGC circuit, 41 is an AGC circuit, and 42 is a time constant setting circuit for setting the time constant of the AGC circuit 41. FIG. 14 shows an example of an output spectrum waveform when the AGC circuit 41 is applied to the peak power limitation of the OFDM signal and the time constant setting circuit is set at high speed. FIG. 14 shows that a very large distortion occurs in the one-segment signal in the above-described one-segment broadcasting frequency band. As shown in FIG. 14, when the time constant is set to be short and high so as to apply the AGC circuit 41 to the peak power limitation of the OFDM signal, there is a problem that an excessive response occurs, and a very large distortion occurs in the one-segment signal. .
Therefore, it is difficult to limit the peak power by shortening the time constant of the AGC circuit 41 for a signal with a large fluctuation in instantaneous transmission power, such as an OFDM signal, and the AGC circuit 41 is only for the purpose of controlling the average power. It could not be used (see Non-Patent Document 1).

  On the other hand, in the case of a limiter circuit, a diode is usually used. FIG. 15 shows a limiter circuit using a pair of diodes D43 and D44, and FIG. 16 shows the input level vs. amplitude limit level characteristic of this limiter circuit. FIG. 16 shows that a high input level is required to limit the peak value of the instantaneous transmission power fluctuation. Specifically, the transmission power of the weak radio station is normally about −70 dBm, but the amplitude limit by the diode requires an input level of about 17 dBm in order to suppress −3 dB from FIG. Therefore, when applied to a device that targets weak radio waves, it is necessary to amplify a -70 dBm signal to 87 dBm to 17 dBm, and after limiting the amplitude by a diode, attenuate the 87 dB level by an attenuator to obtain a -70 dBm signal. There is a problem that an amplifier with a very high gain is required. Further, since signals having a very large level difference coexist in the same frequency band, there is a problem that it is difficult to ensure isolation between signals.

  Therefore, in view of such problems, the present invention eliminates the occurrence of peaks exceeding a predetermined level in the OFDM signal, can cope with a sharp change in instantaneous transmission power, and can expand a receivable area. The object is to provide a radio wave transmitter.

In order to solve the above-mentioned problem, the weak radio wave transmitter according to the invention of claim 1 inputs an OFDM signal and cuts the waveform exceeding the peak value of the waveform of the input signal exceeding a specific value. And a transmission power increase / decrease unit for increasing / decreasing the output of the signal amplitude limiter.
According to this configuration, the occurrence of a peak exceeding a specific level can be eliminated by the signal amplitude limiting means. Therefore, the average transmission power can be increased while suppressing the peak value within a certain electric field strength, and the receivable area can be expanded.

According to a second aspect of the present invention, in the configuration of the first aspect, a gain control circuit for controlling a gain of the transmission power increasing / decreasing means is provided, and the gain control circuit is based on amplitude limit information of the signal amplitude limiting means. Control is performed so that the average output power of the transmission power increasing / decreasing means becomes a specific value.
According to this configuration, it is possible to control the average transmission power of the weak radio wave transmitter according to the amplitude limit amount.

According to a third aspect of the present invention, in the configuration according to the second aspect, the signal amplitude limiting unit limits the peak power of the input signal, and the transmission power increasing / decreasing unit determines the weakness based on the amplitude limitation information. Control is performed to increase the average transmission power so that the peak power of the signal transmitted by the radio wave transmitter is constant.
According to this configuration, the peak value of the instantaneous transmission power transmitted by the weak radio wave transmission device can be made constant.

According to a fourth aspect of the present invention, in the configuration according to the third aspect, the transmission power increasing / decreasing means transmits the electric field intensity measured at a predetermined distance which is a condition of weak radio waves while satisfying a peak value below a predetermined value. Control is performed to increase the average transmission power of the transmitted signal.
According to this configuration, the receivable area can be expanded while the peak value of the electrolytic strength satisfies 35 μV / m or less at a distance of 3 meters, which is the current condition of weak radio waves.

According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, the signal amplitude limiting means includes at least one transistor that amplifies and outputs an input signal, and the transistor has an input signal waveform. The peak value is cut by class AB operation that amplifies and outputs a waveform that exceeds half-wave component and less than the full waveform, or class B operation that amplifies and outputs only the half-wave component of the input signal waveform. Features.
According to this configuration, it is possible to cope with a steep change in instantaneous transmission power with a simple circuit and to favorably limit the peak value.

According to a sixth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, the signal amplitude limiting means has two stages of clip circuits each including a class AB-operating transistor, and the input signal has positive and negative peaks. A peak value cut is performed on the value, and a signal having a peak value equal to or less than a predetermined value is transmitted.
According to this configuration, it is possible to cope with a sudden change in instantaneous transmission power with a simple circuit by operating the transistor in class AB, and it is possible to favorably limit the peak value.

A seventh aspect of the invention is characterized in that, in the configuration of the sixth aspect, the signal amplitude limiting means includes a level adjustment circuit for adjusting an input of a subsequent clip circuit between the two clip circuits. To do.
According to this configuration, even if the characteristics of the preceding and succeeding clip circuits are different, a peak exceeding a specific value can be favorably cut with respect to the positive and negative waveforms of the input signal.

According to the present invention, the signal amplitude limiting means can eliminate the occurrence of a peak exceeding a specific level for the input OFDM signal. Therefore, the average transmission power can be increased while suppressing the peak value within a certain electric field strength, the receivable area can be expanded, the number of transmitters per unit area can be reduced, and the installation cost can be reduced. be able to.
In addition, by operating the transistors in class AB or class B, it is possible to cope with a sudden change in instantaneous transmission power with a simple circuit, and it is possible to satisfactorily limit the peak value.

It is a circuit diagram which shows an example of the weak radio wave transmission apparatus which concerns on this invention. 1 shows peak power with the horizontal axis representing the frequency of the weak radio wave transmission apparatus, where (a) is before amplitude limitation and (b) is after amplitude limitation. 1 shows the instantaneous transmission power with the horizontal axis representing the time of the weak radio wave transmission apparatus, where (a) is before amplitude limitation and (b) is after amplitude limitation. It is a circuit diagram of the weak radio wave transmitter which shows the other form of this invention. FIG. 5 is an input level vs. amplitude limit level characteristic diagram of the circuit of FIG. 4. It is a circuit diagram which shows the other example of the weak radio wave transmission apparatus which concerns on this invention. FIG. 7 is an operation characteristic diagram of the amplitude limiting circuit of FIG. 6, (a) is a characteristic of the first clip circuit, (b) is a characteristic of the second clip circuit, and (c) is a case where the clip circuit is operated in class A. The characteristics are shown. The relationship between the clipping amount of the amplitude limiting circuit and the input level is shown. (A) shows the characteristic of only one stage of the clip circuit, and (b) shows the characteristic of two stages of the clip circuit. (A)-(c) has shown an example of the level adjustment circuit. It is a circuit diagram which shows the other example of a weak radio wave transmitter. It is a circuit diagram which shows the other example of a weak radio wave transmitter. It is a circuit diagram which shows the other example of a weak radio wave transmitter. It is a circuit diagram which shows an example of the conventional weak radio wave transmitter. FIG. 14 is an output spectrum waveform diagram when the circuit of FIG. 13 is applied to one segment. It is a circuit diagram which shows the other example of the conventional weak radio wave transmitter. FIG. 16 is a characteristic diagram of the input level versus the amplitude limit level in FIG. 15.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an example of a weak radio wave transmission apparatus according to the present invention, wherein 1 is a signal input terminal for inputting a one-segment signal, 2 is a signal output terminal to which an antenna is connected, and 3 is a signal including a transistor Q1. An amplitude limiting circuit as amplitude limiting means, 5 is a gain changing circuit (GC) as transmission power increasing / decreasing means, 6 is a control circuit for controlling the gain changing circuit 5, 7 is an A / D converter (ADC), 8 is D / D A converter (DAC).

The amplitude limiting circuit 3 is a class AB operation circuit composed of a grounded emitter circuit of a high frequency amplification NPN transistor Q1, and has a peak waveform exceeding a specific value with respect to a one-segment signal composed of an OFDM signal inputted from the signal input terminal 1. This is a clip circuit that outputs a clip (cut).
Specifically, the variable resistor VR1 for changing the collector current Ic for adjusting the amplitude limit level, the determination resistor R10 for detecting the collector current, and the collector voltage Vc are set at the emitter of the transistor Q1 of the amplitude limit circuit 3. The first DC power source V1 and the second DC power source V2 for setting the base voltage Vb are provided, and for a waveform in which the peak value of the input signal waveform exceeds a specific value, the transistor Q1 operates in a class AB to obtain a specific value. The variable resistor VR1 is adjusted so as to clip and output the waveform exceeding the limit.

  The threshold for cutting the peak waveform of the amplitude limiting circuit 3 is specifically set in consideration of the gain balance of the gain changing circuit 5, and the peak power value of the signal output from the signal output terminal 2 is taken into account. Is set. L1 is a matching transformer for matching output impedance, and L2 and L3 are choke coils that block the passage of high-frequency signals.

  The control circuit 6 is composed of a microcomputer, and determines the resistance limit level of the amplitude limiter circuit 3 based on the voltage drop information (amplitude limit information) of the resistor R10 converted into digital data by the A / D converter 7. The control signal is converted into analog data by the D / A converter 8 and the gain of the gain changing circuit 5 is controlled. As a result, the signal output from the signal output terminal 2 can increase the average power for the level on which the amplitude is limited.

  FIG. 2 shows the peak power with the horizontal axis representing the frequency of the weak radio wave transmitter of FIG. FIG. 3 shows the instantaneous transmission power with the horizontal axis representing the time of the weak radio wave transmission apparatus of FIG. In either case, (a) shows a state before amplitude limitation, and (b) shows a state in which the peak value of a specific value or more is limited by adjusting the variable resistor VR1. 2 and 3, it can be seen that after the amplitude is limited, the electric power having a magnitude greater than the specific value is suppressed on the frequency axis and the time axis.

  The weak radio wave transmitter configured in this way amplifies the input signal by controlling so that the peak waveform exceeding the specific value set by the variable resistor VR1 is cut and the average transmission power is kept constant. Is output. For example, the level in which the amplitude is limited is compensated so that the maximum value of the electric field intensity of a signal radiated from an antenna (not shown) connected to the signal output terminal 2 is 35 μV / m or less at a peak value at a distance of 3 meters. Thus, the control circuit 6 controls the gain changing circuit 5. As a result, the average transmission power is controlled to increase while the peak power is maintained at a predetermined value or less.

Thus, the occurrence of a peak exceeding a specific level can be eliminated by the amplitude limiting circuit 3, and even if the average transmission power is increased by controlling the gain changing circuit 5, the peak value is suppressed within a certain electric field strength. The average transmission power can be increased without increasing the peak value. Furthermore, the gain changing circuit 5 can control the peak power to be constant according to the amount of amplitude limitation of the amplitude limiting circuit 3, and can keep the peak value of the instantaneous transmission power of the weak radio wave transmission device constant. As a result, the receivable area can be expanded while satisfying the condition of weak radio waves.
Furthermore, the peak value of the transmission signal can be limited with a simple circuit that causes the transistor to perform class AB operation.

  FIG. 4 shows another example of the weak radio wave transmitting apparatus, and the same components are assigned the same reference numerals. The configuration of the output circuit is different from that in FIG. 1 and the gain changing circuit 5 is not provided. Further, the variable resistor R10 for adjusting the amplitude limit level is not provided, but is a fixed resistor R7. FIG. 5 shows the input level vs. amplitude limit level characteristic of this circuit. As shown in FIG. 5, even with an amplitude limit circuit using an NPN transistor alone, instantaneous transmission power fluctuations can be reduced at a low input level by using class AB operation. Peak value can be limited. Therefore, it is possible to configure a weak radio wave transmitter that can suppress peak power and does not transmit a signal having an electric field intensity exceeding a specific value.

  In the above-described embodiment, a signal whose peak value is limited is output by operating the NPN transistor in class AB. However, a signal whose peak value is limited can be output even when the NPN transistor is operated in class B. . Thus, by amplifying by class AB or class B, the signal quality can be improved as compared with, for example, the use of a class C amplifier circuit.

  The circuit diagram of FIG. 6 shows another example of the weak radio wave transmitter according to the present invention. Reference numeral 23 denotes a clip circuit (first clip circuit 23a and second clip circuit 23b) that clips and outputs a peak value of a specific magnitude or more of the input signal, and reference numeral 24 denotes a signal input to the second clip circuit 23b. This is a level adjustment circuit for adjusting the level, and the same reference numerals are given to the components common to those in FIG. The first clip circuit 23a, the second clip circuit 23b, and the level adjustment circuit 24 constitute an amplitude limiting circuit 30 that cuts a peak value that is greater than a specific value.

  As shown in FIG. 6, the amplitude limiting circuit 30 includes a two-stage clip circuit 23 (23a, 33b), and both the clip circuits 23 have the same circuit configuration. However, since the signals input to the second clip circuit 23b at the subsequent stage have phases inverted with respect to the input signals of the first clip circuit 23a at the previous stage, they complement each other.

  Specifically, the first clip circuit 23a is a grounded emitter circuit of the first transistor Q11 composed of a high-frequency amplification NPN transistor, and has a configuration in which a bias is set so as to perform class AB operation. Similarly, the second clip circuit 23b is also a grounded-emitter circuit of the second transistor Q12 composed of a high-frequency amplification NPN transistor, and is configured to be biased so as to operate in class AB.

  As a result, the first clip circuit 23a and the second clip circuit 23b both clip and output a peak waveform exceeding a specific value with respect to the input signal. Therefore, a peak waveform exceeding a specific value is cut and output with respect to the one-segment signal composed of the OFDM signal input from the signal input terminal 1. The first clip circuit 23a clips and outputs one of the positive and negative peaks, and the second clip circuit 23b clips and outputs the other peak. Further, the clip circuit 23 is configured to operate the NPN transistor in the class AB, so that the peak value can be satisfactorily limited in the frequency band of the one-segment broadcasting.

  FIG. 7 shows an operation characteristic diagram (Ic-Vce characteristic diagram) of the clip circuit 23, (a) shows the characteristic of the first clip circuit 23a at the first stage, and (b) shows the second characteristic at the second stage. The characteristics of the clip circuit 23b are shown and will be further described with reference to this figure. In each figure, P is an operating point, Si is an input signal, So is an output signal, and Io is an output current. By providing two stages, the output is limited by reliably cutting the peaks for both the positive and negative waveforms of the signal waveform. For reference, (c) shows the characteristics when Class A amplification is performed.

  As shown in FIG. 7A, by setting the operating point P of the first transistor Q11, the peak is clipped and output for a peak waveform exceeding a certain voltage value. At this time, the voltage level to be clipped is set by the resistor R4. Further, by setting the operating point P of the second transistor Q12 as shown in FIG. 7B, the peak is clipped and output for a peak waveform exceeding a certain voltage. At this time, the voltage level to be clipped is set by the resistor VR2. As a result, both positive and negative peak waveforms are clipped and output.

  The clip circuit 23 is a circuit similar to the amplitude limiting circuit 3 shown in FIG. 1 and exhibits peak power characteristics as shown in FIG. Moreover, the instantaneous transmission power characteristic shown in FIG. 3 is shown.

  Similar to the circuit of FIG. 1, the gain changing circuit 5 is controlled by a control circuit 6 comprising a microcomputer so that the output power is constant. The control circuit 6 determines the resistance limit level of the second clip circuit 23b based on the voltage drop amount information (amplitude limit information) of the resistor R10 converted into digital data by the A / D converter (ADC) 7. Generate and output a control signal. This control signal is converted into analog data by a D / A converter (DAC) 8 and sent to the gain changing circuit 5 to control the gain of the gain changing circuit 5. In this way, the clip circuit 23 limits the peak power of the input signal, and the gain changing circuit 5 increases the average transmission power so that the peak power of the signal output from the clip circuit 23 is constant based on the amplitude limit information. To implement.

   FIG. 8 shows the relationship between the clipping amount of the amplitude limiting circuit 30 and the input level, FIG. 8A shows the characteristics of the clipping amount and the input level of only the first clip circuit 23a, and FIG. The clipping characteristics of a two-stage clip circuit obtained by adding a second clip circuit 23b to one clip circuit 23a are shown. M1 is a clipping amount and M2 is a MER (modulation error ratio). For example, when the clipping amount when the MER is 12 dB is compared, it is 3.8 dB in FIG. 5A and 4.8 dB in FIG. 5B, and the MER value is deteriorated by clipping both positive and negative peak values. It can be seen that the clipping amount can be increased without any problem. In addition, in the case of one stage, there is a limit to the amplitude limit, but it can be seen that the amplitude limit can be increased by using two stages.

  Thus, in each clip circuit 23, the peak waveform exceeding a specific value is cut to limit the peak power. Then, the gain changing circuit 5 increases and decreases the average transmission power so that the average transmission power of the signal output from the clip circuit 23 becomes a specific value based on the amplitude limit information. For example, the level in which the amplitude is limited is compensated so that the maximum value of the electric field intensity of a signal radiated from an antenna (not shown) connected to the signal output terminal 2 is 35 μV / m or less at a peak value at a distance of 3 meters. Thus, the control circuit 6 controls the gain changing circuit 5. As a result, the average transmission power is controlled to increase while the peak power is maintained at a predetermined value or less. However, the standard value of the maximum value of the electric field strength varies depending on the frequency band used.

  FIG. 9 shows the level adjustment circuit 24, (a) and (b) showing a fixed type, and (c) showing a variable type circuit. In FIG. 6C, the level can be changed by adjusting the variable resistor VR31. By providing such a level adjustment circuit, even if the characteristics of the first transistor Q11 of the first clip circuit 23a and the second transistor Q12 of the second clip circuit 23b are different or the circuit characteristics are different, the input is possible. Peaks exceeding a specific value with respect to the positive and negative peak waveforms of the signal can be cut well.

In this way, by configuring the amplitude limiting circuit 30 with two clip circuits 23, it is possible to eliminate the occurrence of positive and negative peaks exceeding a specific level with respect to the input OFDM signal. Therefore, the average transmission power can be increased while suppressing the peak value within a certain electric field strength, and the receivable area can be expanded.
Further, by operating the transistors Q11 and Q12 in class AB, a simple circuit can cope with a sudden change in instantaneous transmission power, the peak value can be well limited, and the weak radio wave according to the amplitude limit amount of the clip circuit 23 The average transmission power of the transmission device can be controlled.
Then, the receivable area can be expanded while the peak value of the electrolytic strength satisfies 35 μV / m or less at a distance of 3 meters, which is the current condition of weak radio waves. It should be noted that the same operation is achieved even in a frequency band of 322 MHz or lower, which is lower than the frequency band of normal one-segment broadcasting.

  10 to 12 show other examples provided with a two-stage clip circuit. In FIG. 10, the level adjustment circuit 24 has an automatic adjustment function. The emitter current of the first clip circuit 23a at the first stage is detected by an A / D converter (ADC) 31, and a microcomputer (microcomputer) 32 determines the amplitude limit amount from this current information, and the D / A converter (DAC) ) 33 to output a control signal to the level adjusting unit 24a. By this control, the level adjustment unit 24a automatically adjusts the output of the first clip circuit 23a to a level at which the second clip circuit 23b in the second stage performs optimum amplitude limitation.

11 and 12 are configured without a level adjustment circuit. By providing a specific relationship between the characteristics of the first transistor Q11 of the first clip circuit 23a and the characteristics of the second transistor Q12 of the second clip circuit 23b, the level adjustment circuit can be eliminated. For example, by making the second transistor Q12 have a high output with respect to the first transistor Q11, it is possible to perform satisfactory amplitude limitation without a level adjustment circuit as shown in FIG.
In FIG. 12, variable resistors VR4 and VR10 are provided at the emitters of both transistors Q11 and Q12, and the level adjustment circuit is eliminated by adjusting the bias.

  In addition to these configurations, the level adjustment circuit can be eliminated even if the collector current of the second transistor Q12 is controlled based on the collector current information of the first transistor Q11.

  1 .... Signal input terminal 2 .... Signal output terminal 3 .... Amplitude limiting circuit (signal amplitude limiting means) 5 .... Gain changing circuit (transmitting power increasing / decreasing means) 6 .... Control circuit (gain control circuit) , Q1 .. Transistor, 23 .. Clip circuit, 23a .. First clip circuit, 23b .. Second clip circuit, 24 .. Level adjustment circuit, 30 .. Amplitude limiting circuit (signal amplitude limiting means), Q11... First transistor, Q12.

Claims (7)

When an OFDM signal is input and the peak value of the input signal waveform exceeds a specific value, a signal amplitude limiting unit that outputs a signal obtained by cutting the excess waveform and the output of the signal amplitude limiting unit are increased or decreased. A weak radio wave transmission device comprising transmission power increase / decrease means. A gain control circuit for controlling the gain of the transmission power increase / decrease means;
2. The weak radio wave transmission according to claim 1, wherein the gain control circuit controls the average output power of the transmission power increasing / decreasing means to be a specific value based on amplitude limit information of the signal amplitude limiting means. apparatus. The signal amplitude limiting means limits the peak power of the input signal, and the transmission power increase / decrease means averages so that the peak power of the signal transmitted by the weak radio wave transmitter is constant based on the amplitude limit information. The weak radio wave transmission device according to claim 2, wherein control for increasing transmission power is performed. The transmission power increasing / decreasing means performs control to increase an average transmission power of a signal to be transmitted while an electric field intensity measured at a predetermined distance which is a condition of weak radio waves satisfies a predetermined value below a peak value. The weak radio wave transmission device according to claim 3. The signal amplitude limiting means includes at least one transistor that amplifies and outputs an input signal, and the transistor amplifies and outputs a waveform that exceeds the half-wave component of the input signal waveform and does not satisfy all waveforms. 5. The weak radio wave transmission device according to claim 1, wherein the peak value is cut by an operation or a class B operation for amplifying and outputting only a half-wave component of the input signal waveform. The signal amplitude limiting means has two stages of clipping circuits including transistors that operate in class AB, and performs peak value cut for positive and negative peak values of an input signal,
5. The weak radio wave transmission device according to claim 1, wherein a signal having a peak value equal to or less than a predetermined value is transmitted. 7. The weak radio wave transmission device according to claim 6, wherein the signal amplitude limiting means includes a level adjustment circuit for adjusting an input of a subsequent clip circuit between the two clip circuits.

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