JPS6159001B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carrier wave conversion device (FM-AM conversion device) that directly converts a frequency modulated carrier wave into an amplitude modulated carrier wave.

FIG. 1 is a circuit diagram showing the principle of a conventional FM-AM converter. Let f ₁ be the instantaneous frequency of an input carrier wave subjected to frequency modulation (FM modulation), let f ₀ be its center frequency, and let f ₂ be the number of carrier waves to be amplitude modulated (AM modulated). In Figure 1, 1 is FM
At the input terminal of the modulated wave f ₁ , 2 is a circuit whose transfer characteristics change according to changes in frequency, and its center frequency is set to f ₀ . 3 is a diode, 4 is a circuit means having directionality such as a bridge circuit, a directional coupler, a circulator, etc., and 5 is a diode.
is the input terminal of the carrier wave f ₂ , 6 is the output terminal of the carrier wave f ₂ subjected to amplitude modulation, and 7 is a low-pass circuit to pass the rectified current I _d of the diode 3 and block high frequencies. 8 is a circuit for short-circuiting appropriate components of |mf ₁ ±nf ₂ | (where m and n are integers including 0, but excluding f ₁ and f ₂ ) generated by a diode, and 9 is a circuit for short-circuiting appropriate components of f ₂ wave blocking circuit, 1
0 is an _f1 wave blocking circuit.

The operating principle of FIG. 1 will be explained below. The input carrier wave f ₁ applied to the terminal 1 is subjected to a change in transfer characteristic according to its frequency by the circuit 2, resulting in a characteristic as shown in FIG. 2, for example. In addition, in Figure 2, E ₁
represents the amplitude of the carrier wave f ₁ applied to the diode 3. The carrier wave E ₁ generates a rectified current I _d in the diode 3, and the rectified current also changes according to the amplitude change of E _1. As a result, the small signal impedance (hereinafter referred to as R _d ) of the diode 3 and omitted)
changes in accordance with I _d , and as a result, R _d changes as shown in FIG. 3 in accordance with the frequency change of the input carrier wave f ₁ . Now, if a sufficiently small amplitude carrier wave f ₂ is applied to the diode 3 from the terminal 5 via the circuit 4, the amplitude E ₂ of the carrier wave f ₂ appearing at the terminal 6 becomes as shown in the first equation.

E ₂ ′=kR _d −R _O /R _d +R _O ………(1) However, k is a constant, and R _O is a circuit 4 with directionality.
represents the characteristic impedance of

That is, according to the change in R _d , R _d becomes R _O
When equal to , no f ₂ wave appears at terminal 6, or f ₁
By changing the wave frequency, R _d becomes R _O according to Figure 3.
If it becomes larger or smaller, an output of the _f2 wave will appear at the terminal 6 according to the first equation depending on the magnitude, and as a result, the frequency change of the input carrier wave f1 at the terminal ₁ For example, as shown in FIG.
The amplitude E ₂ of the f ₂ wave changes, and the frequency shift of the FM wave f ₁ can be converted into an amplitude change of the AM wave f ₂ .

However, in the conventional circuit as shown in FIG. 1, the linearity of the circuit 2 and the f ₁ applied to the diode
The linearity of the relationship between the wave amplitude E ₁ and the small signal impedance of the diode, and the small signal impedance and
Due to the fact that the linearity of the relationship with the f ₂ wave output amplitude is not very good, _the f ₂
There was a drawback that the linearity of the change in wave output amplitude was not good.

Also, if the amplitude of the FM wave applied to input terminal 1 changes, R _d changes, and the amplitude E ₂ of the output f ₂ wave changes, so in order to prevent the input from receiving noise due to the amplitude fluctuation of the M wave, The disadvantage of this method is that it is necessary to apply a signal with the AM component sufficiently suppressed, and that a high-performance amplitude limiting circuit must be added to the front stage of the FM-AM converter.

Therefore, the object of the present invention is to eliminate these drawbacks, and to provide an FM circuit with a simple structure similar to the conventional circuit.
An object of the present invention is to provide an AM conversion device.

FIG. 5 is a circuit diagram showing the principle of the present invention. In the same figure, 11 is the input terminal of the FM modulated wave _f1 ;
Reference numeral 2 denotes a branching circuit whose transfer characteristics to its two output terminals change differently depending on changes in frequency. As shown in FIG. 11, for example, this branching circuit 12 distributes an input signal to output terminals 51 and 52 by a distributor 55 connected to an input terminal 11, and outputs a resonant frequency to each of them. Series resonant circuits 53 and 54 having different values are connected. 31,
32 is a nonlinear circuit including diodes 13, 14, etc., respectively. 13 and 14 are diodes such as junction diodes, Schottky barrier diodes, tunnel diodes, and the like. 15 is
is the input terminal of the carrier wave f ₂ to be AM modulated,
16 is a circuit having a first directionality, such as a bridge circuit or a directional coupler, and 17 is a circuit having a second directionality, such as a directional coupler or a distributor. 18 is an output terminal of carrier wave f ₂ subjected to AM modulation, and 19 and 20 are trap circuits for short-circuiting |mf ₁ ±nf ₂ | components. 21 and 22
is a low-pass circuit that allows the rectified currents of the diodes 13 and 14 to pass through each circuit, blocking high frequencies and passing direct current and low frequencies. 23 and 24 are f ₂
In the wave passage blocking circuit, 25 and 26 are _f1 wave passage blocking circuits, and 27 and 28 are bias power supplies.

The operation of the present invention will be explained in detail below with reference to FIG. The FM modulated input wave f ₁ is applied to the branching circuit 12 from the terminal 11 . The branching circuit 12 has transfer characteristics to its two output terminals that change differently depending on the frequency, and in the frequency range targeted by the frequency characteristics, the center frequency f ₀ is set as an axis of symmetry as shown in FIG. It is a circuit with almost symmetrical characteristics. In FIG. 6, _E11 is the output amplitude of the branching circuit 12 applied to the diode 13 in the nonlinear circuit 31, and _E12 is the output amplitude of the branching circuit applied to the diode 14 in the nonlinear circuit 32. 12 output amplitudes. In addition, the transfer characteristics illustrated in Fig. 6 are as follows:
For example, when using the branching circuit illustrated in FIG. 11, the series resonant frequency and load Q can be adjusted appropriately by appropriately setting the values of the inductance and capacitance that constitute the series resonators 53 and 54. , and the frequency interval and frequency change temporality of |E ₁₁ | and |E ₁₂ | can be set as desired.
Rectified currents flow through the diodes 13 and 14 due to f ₁ of the amplitudes E ₁₁ and E _12, respectively, and as a result, the small signal impedance of each diode also changes, and as shown in FIG. 7, the target frequency range is The property is symmetrical with f ₀ as the axis of symmetry. In FIG. 7, R _d1 is the small signal impedance of the diode 13, and R _d2 is the small signal impedance of the diode 14.

Now, a circuit having a first directionality from terminal 15,
For example, through the bridge circuit 16, the diode 13
If a sufficiently small amplitude carrier wave f ₂ is applied to and 14,
The amplitude E ₂₃ in consideration of the phase of the f ₂ wave at the output terminal 33 of the bridge circuit 16 is as shown in FIG. 8, for example. That is, in FIG. 8, f ₂ that is reflected by the diode 13 and appears at the output terminal 33 of the bridge circuit 16 is E ₂₁ , and is reflected by the diode 14,
Assuming that the amplitude of the f ₂ wave appearing at the output terminal 33 is E ₂₂ , the shape of each graph is almost the same as E ₂ in FIG. 4. Now, connect the fifth terminal to each terminal of the bridge circuit 16.
As shown in the diagram, mark the terminals A, B, C, and D.
and B, B and _C , C and D, and D and _A , _{respectively .}
When expressed as _D and θ _DA , |(θ _AB +θ _BC )−(θ _CD +θ _DA )| = 180°...(2) In order to satisfy the second equation, for example, θ _AB is set to 0° as the bridge circuit 16. , θ _BC is 0°, θ _CD is 180
If a bridge circuit in which θ and θ _DA are 0° is adopted, E ₂₁ and E ₂₂ will have opposite phases. Since R _d1 and R _d2 are symmetrical with respect to f ₀ as shown in Fig. 7, |E ₂₁ | and |E ₂₂ | are symmetrical with respect to f ₀ , and as mentioned above, E ₂₁ and E ₂₂ are in opposite phase with each other, so E ₂₁ and E ₂₂ end up on the f ₁ axis as f 1 = f ₁ as shown in Figure 8.
It is almost point symmetric with respect to the f ₀ point. Note that FIG. 8 is expressed with the phase of E ₂₁ as a reference. output
Since E ₂₃ is the sum of E ₂₁ and E ₂₂ , if the frequency interval and frequency change characteristics of |E ₁₁ | and |E ₁₂ | in FIG. 6 are appropriately set, E 21 and E ₂₂ in FIG. By appropriately setting the frequency interval with E ₂₂ and the frequency change characteristics, E ₂₃ becomes a substantially straight line graph that becomes 0 at f ₀ as shown in FIG. As described above, in accordance with the frequency change of the f ₁ wave, the amplitude of the f ₂ wave appearing at the output terminal of the bridge circuit 16 changes almost linearly as shown in the graph of E ₂₃ in FIG. The linearity is better than that of the conventional circuit (which is comparable to the linearity of E ₂₁ in FIG. 8, for example).

Next, E ₂₃ , which is the output of the bridge circuit 16, is further added with an f ₂ carrier wave having an appropriate amplitude E _C by a second directional circuit 17 in the same phase as E ₂₁ or in phase with E ₂₂ . It will be done. As a result, output terminal 18
The graph representing the amplitude E ₂ of the f ₂ wave appearing in is a graph obtained by translating the graph of E ₂₃ in FIG. 8 by E _C in the vertical axis direction, and has a characteristic as shown in FIG. 9, for example. Therefore, depending on the frequency of the _f1 wave applied to the terminal 11, the amplitude of the _f2 wave at the terminal 18 can be changed while maintaining good linearity, and if E _C is set appropriately, At the required frequency of the _f1 wave, the amplitude of the _f2 wave can be set to zero. That is, it is possible to easily convert an input FM wave into an AM wave with a sufficiently high degree of modulation while maintaining good linearity.

Also, as is clear from FIGS. 8 and 9, the output amplitude of the f ₂ wave by the circuit of the present invention is
If the amplitude of _{the f2} wave applied to
Therefore _, the output power of the converter according to the present invention can be approximately four times that of the conventional circuit.
This is a major feature of the present invention.

In the example of FIG. 9, the amplitude E _C
f ₂ was added to be in phase with E ₂₁ , and the graph of E ₂₃ was translated in the positive direction of the vertical axis. In this case, the input FM modulated wave _f1 is modulated with a video signal, for example,
When the polarity of the modulation is a synchronous signal negative polarity method (that is, a method in which the instantaneous frequency of the f ₁ wave corresponding to the synchronous signal portion is lower than the center frequency), the output AM modulated wave f ₂ is synchronized as shown in Fig. 9. This is a signal positive modulation method (that is, a method in which the carrier wave has a larger average amplitude in the portion corresponding to the synchronization signal). Similarly, the _f2 wave of amplitude E _C is generated by the synthesis circuit 17.
If it is added in the same phase as E ₂₂ , the graph of change in E ₂ will be a graph obtained by shifting the graph of E ₂₃ in parallel in the negative direction of the vertical axis by E _C , as shown in FIG. The output AM modulated wave for the FM input signal of the video signal modulated wave can be a synchronizing signal negative modulation method (that is, a method in which the carrier wave has a smaller average amplitude in the portion corresponding to the synchronizing signal). As described above, according to the present invention, by changing the phase at which E _C is added (for example, if the combining circuit 17 is configured with a directional coupler, the phase can be changed by changing the connection terminals thereof). Possible) You can easily set the modulation polarity of the output AM wave to positive or negative for the same FM input wave. This is also a feature of the present invention.

When the FM input wave f ₁ is around the center frequency f ₀ , even if the amplitude of the input wave at the input terminal 11 changes somewhat, the two output amplitudes E ₁₁ and E ₁₂ of the branching circuit 12 also change at the same rate, Therefore, R _d1 and R _d2 also vary at the same rate,
Therefore, the amplitudes of E ₂₁ and E ₂₂ fluctuate at the same rate, but
As is clear from FIG. 8, when f ₁ = f ₀ , E ₂₃ remains 0 and does not change, so E ₂ in FIG. 9 or 10 does not change.
The amplitude at f ₁ = f ₀ does not fluctuate, and the fluctuation around f ₀ is also small. Therefore, the FM-AM according to the invention
The conversion circuit is less susceptible to noise due to amplitude fluctuations of the FM input wave than conventional conversion circuits.
This is also a feature of the present invention.

In the above explanation, as an example of the branching circuit 12, the first
The circuit example in Figure 1 has been described, and in the same figure, 53 and 54 are series resonant circuits connected in parallel, but these can be replaced with parallel resonant circuits connected in series or band instant stop filters. can.

12 and 13 as other examples of the branching circuit 12.
It is clear that similar characteristics can be obtained with circuits based on the principles shown in the circuit diagrams shown in FIGS. In addition, in Figure 12, 59 and 60
are parallel resonant circuits with different resonant frequencies,
Similar characteristics can be obtained by using a series resonant circuit connected in series or a band pass filter in place of 59 and 60. Also, in Figure 13, 61
and 62 are a low-pass filter and a high-pass filter, and in FIG. 14, 63 and 64 are directional couplers, θ ₁ and θ ₂ are the electrical lengths of the respective lines, and θ ₁ and It differs from θ ₂ by an appropriate length. Also, in Figure 16, 65 and 6
6 is a directional coupler or magic T, 67 is a resonant circuit, and 68 is a short-circuit line. Further, similar FM-AM conversion characteristics can be obtained by connecting a directional circuit such as an amplifier, an attenuator, or an isolator to the input/output terminals of the above-mentioned various branching circuits or in the middle thereof.

In the above principle diagram, the diodes 13 and 14 are connected in parallel, but even if they are connected in series as in the example of FIG. 17, the same operating characteristics as described above can be obtained. In addition, in Figure 17, 81, 82, 83, and 8
4 is a low-pass circuit. Further, even if the polarities of one or both of the diodes 13 and 14 are reversed, the same operating characteristics as described above can be obtained. It is clear that the same operating characteristics as described above can be obtained by using nonlinear elements other than diodes, such as transistors and electron tubes, in place of the diodes 13 and 14, and utilizing the diode characteristics between their appropriate terminals. It is.

Also, non-linear circuits 31 and 3 using diodes
Even if a non-linear circuit such as a transistor amplification circuit or an electron tube amplification circuit is used instead of 2, the same characteristics as described above can be obtained as explained below. That is, for example, in FIG.
If a transistor amplification circuit as shown in FIG. 18 is used instead of each, the input f ₁
The wave is applied to the transistor circuit by the branching circuit 12, where the amplitude changes in E ₁₁ and E ₁₂ according to the frequency change as shown in FIG. Since this transistor circuit has nonlinear characteristics, the waveform of the _f1 wave at its input and output terminals is distorted, and as a result, a DC component is generated in the input and output signals. This DC component changes the operating point of the transistor, and as a result changes the input/output small signal impedance of the transistor circuit. Also, since the DC component changes depending on the amplitude of the input _f1 wave, the input of the transistor circuit ends up being
The input/output small signal impedance will change according to the amplitude change of f ₁ wave, and if the operating point of the transistor and the characteristics of the branching circuit 12 are set appropriately, the small signal impedance will be as shown in Fig. 7 above. It is possible to obtain a change characteristic similar to that of the small signal impedance of the diode shown. Therefore, if a sufficiently small amplitude carrier wave f ₂ is applied to the transistor circuit through the circuit 16, FM-AM conversion characteristics similar to those shown in FIGS. 8, 9, and 10 can be obtained.

Similarly, even if an electron tube circuit such as a triode amplification circuit or a pentode amplification circuit as illustrated in FIG. Similar FM-AM conversion characteristics can be obtained using the same principle. In addition,
Although the circuits of FIGS. 18 and 19 show examples of emitter grounding and cathode grounding, respectively, it is clear that similar characteristics can be obtained with other grounding systems. Furthermore, it is clear that similar characteristics can be obtained with nonlinear circuits other than transistors and electron tubes.

Alternatively, the synthesis circuit 17 may be omitted and the output 33 of the bridge circuit 16 may be connected to the output terminal 1 as in the example shown in FIG.
8 and insert an attenuator 90 between the bridge circuit and, for example, the nonlinear circuit 32, the amplitude of the f ₂ wave at the output of the bridge circuit 16 will be as shown in FIG. The amplitude of E ₂₂ is attenuated as in E ₂₁
If we can shift the intersection of _{the graph of the output amplitude E 23 , which} is the composite of It is possible to output the _f2 wave with the necessary amplitude near the center frequency of _f1 ,
It is also possible that the same FM-AM conversion characteristics as described above can be obtained without the synthesis circuit 17, more easily than in the circuit example described above. However, according to the principle diagram in Fig. 20, the balance is shifted compared to the case of the circuit described above, so the characteristics of the operation described above are somewhat impaired, but it is better than the conventional circuit. is clear. In addition, in FIG. 20, the attenuator 90
Instead of inserting the
Even if the magnitudes of the two small signal impedances R _d1 and R _d2 are made different, the characteristics shown in FIG. 21 can be obtained.

Also, as illustrated in FIG. 22, resistors 91 and 92
21, it is possible to equivalently change the magnitude of the small signal impedance seen from the bridge circuit 16, and the characteristics shown in FIG. 21 can be obtained. Also, the second
In FIG. 2, 91 and 92 are not limited to resistors, but may be inductors, capacitors, or composite circuits thereof. Further, in FIG. 22, the non-linear circuit is inserted in parallel, but the same characteristics can be obtained even if the non-linear circuit is inserted in series.

Even if the output E ₂₁ from the nonlinear circuit 31 and the output E ₂₂ from the nonlinear circuit 32 are not made asymmetrical as in the example in FIG. 20, and the characteristics shown in FIG. 8 are maintained, E ₂₃ in FIG.
If only the frequency range smaller than or larger than f ₀ is used in the graph, the same FM-AM conversion characteristics as described above can be obtained, and an AM wave with a high modulation degree can be obtained, and the synthesis circuit 17 can be omitted. can do.

As illustrated in FIG. 23, if a terminal 101 coupled to the low frequency current path of the non-linear circuit is provided and a part of the rectified current of the diodes 13 and 14 is extracted from 101 as shown in FIG. A frequency discriminator characteristic in _which the DC current amplitude changes with respect to a change in the frequency of the input f ₁ wave is obtained, and as shown in the system diagram shown in FIG. and mixer 1
03, intermediate frequency amplifier 104, limiter 105,
If a superheterodyne receiver is configured with a variable frequency local oscillator 106 and the like, and the oscillation frequency of the oscillator 106 is controlled by the output of the terminal 101, for example, the center frequency of the FM wave applied to the input terminal 107 can be varied. FM applied to the FM-AM converter 102 by automatic frequency control operation
The center frequency of the wave is controlled to be constant,
The average carrier wave amplitude of the AM output signal at the AM output terminal 18 can be maintained at a constant value regardless of fluctuations in the input FM wave. As illustrated in system diagram No. 25, the output of the terminal 101 is connected to the low frequency amplifier 110.
You can also monitor the input/output modulation signal of this receiver by taking it out through a cable. As shown in Figure 26 of the system diagram, turn off the FM signal input or
Simultaneously with the signal input, if another external low frequency input signal is applied to the terminal 101 through the low frequency amplifier 111 etc., this low frequency signal will also change the current in the nonlinear circuit and change the small signal impedance. Therefore, the carrier wave f ₂ can be subjected to AM modulation, and this AM modulated wave can be sent out from the terminal 18.

Figure 23 shows the FM-AM illustrated in Figure 5 above.
Although an example in which the converter is provided with the low frequency coupling terminal 101 has been shown, an FM-AM converter using a necessary linear circuit other than the diode shown in the circuit example in FIG. 17 or in FIGS. 18 and 19 is also applicable. Also, for the FM-AM converter in which the combining circuit 17 is omitted as explained in FIG. 20 and FIG. For example, the method described in the 17th
FIG. 27 shows an example in which the FM-AM converter shown in the figure is provided with a low frequency coupling terminal. FIG. 28 shows an example in which transistors are used.

As shown in FIG. 29, the detection circuit 201 and the amplifier 2
02 and the level control circuit 203 detect the width difference in the amplitude of the _f2 wave output of the synthesis circuit 17, amplify it, and control the level of the _f2 carrier wave applied to the synthesis circuit 17. For example, the _f2 wave output amplitude of the synthesis circuit 17 can be automatically controlled to a preset value. For example, if the center frequency f ₀ of the input f ₂ wave fluctuates for some reason, the output
The center amplitude of the AM wave will fluctuate, and for example, if the input _f1 wave is FM modulated with a video signal as in the example in Figure 9, the synchronized peak amplitude of the output AM wave will fluctuate. Although it is inconvenient, in this case, as in the example shown in FIG.
By using a DC amplifier with a time constant faster than the fluctuation period of f ₀ , it is possible to maintain the synchronous peak amplitude of the output AM wave at a constant value.

As shown in FIG. 30, the detector 211 and the signal detector 2
12 demodulates the modulated signal of the AM wave output from the synthesis circuit 17, detects the magnitude of a specific signal contained therein, and applies it to the bridge circuit 16 by the DC amplifier 213 and level control circuit 214. By controlling the magnitude of the carrier wave f ₂ to be
The modulation amplitude of the output AM wave can be automatically controlled to the set value. That is, to explain with reference to FIG. 31 showing the FM-AM conversion characteristics, for example, the input _f1 wave that is FM modulated with the video signal is represented as SIG1, and the graph of the conversion characteristics in the normal state is shown as 21.
6, the amplitude change characteristic of the output _f2 wave at this time becomes SIG2 in FIG. Now, if the conversion characteristic changes as shown in 217 due to a change in temperature characteristics, for example, the output amplitude change characteristic will change as shown in SIG2'. For example, if a decrease in the amplitude of the synchronizing signal of the SIG2' signal is detected and the level of the _f2 carrier wave applied to the bridge circuit 16 is increased by controlling the amount of change, the slope of the conversion characteristic can be changed. Since the level of the applied _f2 carrier wave is proportional, 21
The slope can be corrected from the conversion characteristic of 7 to the conversion characteristic of 216, and the output AM wave can be maintained at SIG2 after all.

In addition to the synchronization signal described above, for example, if the signal is modulated by multiplexing, the magnitude of a specific signal in the multiplexed signal can be detected and the applied level of the _f2 carrier wave can be controlled in the same way as above. Depending on the output AM
The amplitude can be kept constant.

Instead of controlling the amount of f ₂ carrier wave applied to the bridge circuit 16 as shown in FIG. 30, as shown in FIG. 32,
Even if the level control circuit 241 is inserted into the input part of the branching circuit 12 and the magnitude of the _f1 wave applied to the branching circuit 12 is controlled, the slope of the conversion characteristic 216 can be changed in the same way as described above. It is possible to correct the output AM amplitude.

If the correction illustrated in FIG. 29 and the correction illustrated in FIG. 30 or 32 are performed simultaneously, the peak value and modulation degree of the output AM signal can be corrected, for example.

If the above correction amount is, for example, temperature change characteristics,
If it is known in advance, for example, the 33rd
As shown in the figure, by using correction circuits 215, 216, 217 such as attenuators or amplifiers having inverse temperature change characteristics, the same correction as described above can be easily performed.

It is clear that the above correction method can be applied not only to the circuit shown in FIG. 5 but also to all the FM-AM conversion circuits described above.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of a conventional FM-AM conversion device.
Figures 2, 3, and 4 are graphs showing the characteristics of conventional circuits.
FIG. 5 is a block diagram of an embodiment of the present invention; FIGS. 6, 7, 8, 9, and 10 are graphs showing characteristics of the device of the present invention;
Figures 5, 16 and 16 are examples of branching circuits, Figure 17 is a block diagram of another embodiment of the present invention, Figures 18 and 19 are diagrams showing other examples of non-linear circuits, and Figure 20 is a diagram of another embodiment of the present invention. FIG. 21 is a block diagram of still another embodiment, and FIG. 21 is a graph showing the characteristics of the device of the present invention.
4, 25, 26, 27, 28, 29, 30, 3
Figures 2 and 33 are block diagrams of embodiments of the present invention;
FIG. 1 is a graph showing the characteristics of the device of the present invention.

Claims (1)

[Claims] 1. A branching circuit having two outputs whose transfer characteristics change differently depending on the frequency, and two nonlinear circuits connected to each of these outputs,
A circuit having a first directionality connected to the non-linear circuit, and a circuit having a second directionality connected to the circuit having the first directionality, and applying voltage to the branching circuit. The frequency modulated signal is
Converting the frequency applied to the circuit having the first directionality into an amplitude modulated signal using a carrier wave,
Balanced so that the amplitude of the amplitude modulated signal appearing at the output end of the circuit having the first directionality becomes 0 at the center frequency of the frequency modulated signal, and having the second directionality. A carrier wave conversion device, characterized in that it adds or subtracts a part of the carrier wave to be amplitude modulated via a circuit.