JPS6134285B2 - - 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. If the instantaneous frequency of the input carrier wave subjected to frequency modulation (FM modulation) is ₁ , then ₁ changes over time depending on the modulation signal, but its center frequency is ₀ , and the frequency of the carrier wave to be amplitude modulated (AM modulated) is 1. When is ₂ , ₂ is constant.

In Figure 1, 1 is the input terminal for the input carrier wave of carrier wave ₁ (hereinafter referred to as ₁ wave or frequency ₁ ), and 2 is a circuit whose transfer characteristics change according to changes in frequency. The center frequency is
It is set to ₀ . 3 is a diode, 4 is a circuit means having directionality such as a bridge circuit, a directional coupler or a circulator, and 5 is a frequency
₂ carrier wave (hereinafter referred to as ₂ waves or carrier wave ₂₎
6 indicates the output terminal of the carrier wave ₂ subjected to amplitude modulation, 7 is a low-pass circuit for passing the rectified current Id of the diode 3 and blocking high frequencies, and 8 is a circuit for short-circuiting appropriate components of |m ₁ ±n ₂ | (where m and n are integers including 0) generated in diodes, 9 is _{a 2-} wave blocking circuit, and 10 is a _1- wave blocking circuit. This is a blocking circuit.

The operating principle of FIG. 1 will be explained below. The input carrier wave ₁ applied to the terminal 1 undergoes a change in the transfer characteristic according to its frequency by the circuit 2, and is converted into a second carrier wave, for example.
The characteristics will be as shown in the figure. In FIG. 2, E ₁ represents the amplitude of the carrier wave 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 abbreviated as Rd) of the diode 3 )
changes in accordance with I _d , and as a result, R _d changes as shown in FIG. 3 in response to changes in the frequency of the input carrier wave ₁ . Now, if a carrier wave 2 with a sufficiently small amplitude is applied from the terminal 5 to the diode 3 via the circuit 4, the amplitude _E2 of the carrier _{wave 2 appearing} at the terminal 6 will be as shown in the first equation.

E ₂ =KR _d −R _p /R _d +R _p (1) where K is a constant and R ₀ represents the characteristic impedance of the circuit 4 having directionality.

That is, according to the change in R _d , R _d changes to R _p
is equal to , no _two waves appear at terminal 6, and
If the frequency of _one wave is changed and R _d becomes larger or smaller than R _p according to Figure 3, _two waves are output to terminal 6 according to the first equation according to the magnitude. appears, and as a result, the input carrier wave at terminal 1
For example, as shown in Figure ₄ , the amplitude _E2 of _{the two} waves at terminal 6 will change in accordance with the frequency change of wave ₁ , which is the FM wave.
It can be converted into an amplitude change of ₂ .

However _, in the conventional circuit as shown in _{FIG .} There was a drawback that the linearity of the characteristics shown in FIG. 4 was not good because the linearity of the relationship with the wave output amplitude was not very 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 ₂ waves changes, so it is sufficient to avoid noise due to the amplitude fluctuation of the input FM wave. It was necessary to apply a signal with the AM component suppressed to the FM-AM converter, and a high-performance amplitude limiting circuit had to be added to the front stage for this FM-AM converter.

Therefore, it is an object of the present invention to eliminate these drawbacks and yet provide an FM circuit with a simple configuration similar to the conventional circuit.
-Providing AM conversion equipment.

FIG. 5 is a circuit diagram showing the principle of the present invention. In the figure, 11 is an input terminal for _one wave, which is an FM wave.
Reference numeral 12 denotes a branching circuit whose transmission characteristics to its two output terminals change differently depending on changes in frequency; for example, as shown in FIG. 12, a divider 55 connected to the input terminal 11 The input signal is distributed to output terminals 51 and 52 by series resonant circuits 53 and 5, each having a different resonant frequency.
4 are connected. 13 and 14 are diodes such as a junction diode, a shot key barrier diode, a tunnel diode, a can diode, and an impact diode. 15 is the input terminal of carrier wave ₂ to be AM modulated; 16
is a distribution circuit using, for example, a directional coupler, and 17 and 18 are combining circuits using, for example, a directional coupler. 19 is the output terminal of carrier wave ₂ subjected to AM modulation, and 21 and 22 are |
m ₁ ±n ₂ | This is a trap circuit for short-circuiting appropriate components. Reference numerals 29 and 30 designate low-pass circuits or band rejection circuits that block _{the first} and _second waves and pass direct current and low frequencies in order to cause the rectified currents of the diodes 13 and 14 to go through one cycle, respectively.
25 and 26 are _one- wave pass blocking circuits and _two- wave band pass circuits. 27 and 28 are bias power supplies. 23 and 24 are _two- wave pass blocking circuits and _one- wave band pass circuits.

The operation of the present invention will be explained in detail below with reference to FIG. An FM modulated input wave ₁ is applied to a branching circuit 12 from a terminal 11. The branching circuit 12 has transmission characteristics to its two output terminals that change differently depending on the frequency, and in the target frequency range, for example, as shown in _FIG . It is a circuit with almost symmetrical characteristics. In FIG. 6, E ₁₁ is the output amplitude of the branching circuit 12 applied to the diode 13, and E ₁₂ is the output amplitude of the branching circuit 12 applied to the diode 14. A rectified current flows through the diodes 13 and 14 due to _one wave of amplitude E ₁₁ and E ₁₂ , respectively, and as a result, the small signal impedances R _d1 and R _d2 of each diode are changed, and these R _d1 and R As shown in FIG. 7, _d2 has a symmetrical characteristic with ₀ as the axis of symmetry in the target frequency range.

Therefore, the _two waves of a sufficiently small signal are divided into two by the distribution circuit 16, and the diode circuit 35 is connected to each terminal and C.
And diodes 13 and 14 through terminal work I of 36
, the _two waves reach terminals E and D of the combining circuit 17 after being attenuated differently by the small signal impedances R _d1 and R _d2 of the diodes. In this case, each transfer characteristic for _two waves from terminals B to E and from C to F
G ₁ and G ₂ are, for example, as shown in FIG. 8, and like FIG. 7, this also has symmetrical characteristics with ₀ as the axis of symmetry. The terminals of the distribution circuit 16 and the combining circuit 17 are labeled A, B, C, D, E, F as shown in FIG. 5, and the terminals A and B, A and C, E and D, F and D The phase amounts of the transfer characteristics between ∠AB, ∠AC, ∠ED,
When expressed as ∠FD, |(∠AB+ED)−(∠AC+∠
FD)｜=180°……(2) For example, set ∠AB to O°, ∠AC to O°, ∠ED to O°, so as to satisfy the second equation.
If a directional coupler with ∠FD of 180° is adopted as the distribution circuit 16 and the combining circuit 17, the diode circuit 35 will be connected from the terminal 15 through the distribution circuit 16.
and 36, the amplitude _E23 of _{the two} waves appearing at the output terminal D of the combining circuit 17 is the sum of the amplitude E21 due to the diode circuit ₃₅ and the amplitude E22 due to the diode circuit ₃₆ . ,
For example, as shown in FIG. That is, G ₁ and G ₂ are
Since the property is symmetrical with respect to ₀ as the axis of symmetry, E ₂₁
The absolute values of and E ₂₂ are _also symmetrical with respect to the axis of symmetry, and from the relationship in the second equation, the phases of E ₂₁ and E ₂₂ are opposite, so for example, using the phase of E ₂₁ as a reference, Then, as shown in FIG. 9, E ₂₁ and E ₂₂ become almost point symmetrical with respect to the point ₁ = ₀ on _one axis. Therefore, for example, when the circuit shown in FIG. 12 is used as a distribution circuit, by appropriately setting the resonant frequency and Q of the series resonant circuits 53 and 54, the frequencies of |E ₁₁ | and |E ₁₂ | If the interval and frequency change characteristics are set appropriately, the frequency interval and frequency change characteristics between E ₂₁ and E ₂₂ in Fig. 9 will be set appropriately,
E ₂₃ is 0 at ₁ = ₀ , as illustrated in Figure 9.
The graph becomes almost a straight line.

As described above, in accordance with the frequency change of _{the first} wave, the amplitude of _{the second} wave appearing at the output terminal D of the synthesis circuit 17 changes almost linearly as shown in the graph of _E23 in FIG. The linearity is better than that of conventional circuits (which is comparable to the linearity of E ₂₁ in FIG. 9, for example).

Next, E ₂₃ , which is the output of the combining circuit 17, is further added with an appropriate amplitude E _c of _two carrier waves in phase with E ₂₁ or in phase with E ₂₂ by another combining circuit 18. As a result, if the amplitude of _{the two} waves appearing at the output terminal 19 is _E2 , the graph representing the amplitude E2 of _{the two} waves appearing at the terminal 19 in response to the frequency change of _one wave applied to the terminal ₁₁ is shown in FIG. The graph obtained by translating the graph of E ₂₃ in the direction of the minor axis by E _c becomes a graph with characteristics as shown in FIG. 10, for example. Therefore, depending on the frequency of _{the one} wave applied to the terminal 11, the amplitude of _{the two waves} at the terminal 19 can be changed while maintaining good linearity. At the frequency of _one wave
The amplitude of _{the two} waves 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. still,
The setting of E _c can be determined, for example, by selecting the amount of coupling when using a directional coupler as a composite circuit, or by selecting the turns ratio when using the circuits shown in Figures 28 to 32. , or the 33rd, 3rd
When using the circuit shown in FIG. 4, this can be easily implemented by selecting the characteristic impedance of the branch.

In the example of FIG. 10, the amplitude E
_Two waves of _c were added 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 ₁ is modulated with, for example, a video signal, and the polarity of the modulation is a synchronization signal negative polarity method (that is, a method in which the instantaneous frequency of _one wave corresponding to the synchronization signal part is lower than the center frequency). ), as shown in Figure 10, _{the two} output AM modulated waves use the synchronous signal positive modulation method (that is, the method in which the carrier wave is larger than the average amplitude in the part corresponding to the synchronous signal).
becomes. Similarly, if _two waves of amplitude E _c are added to the same phase as E ₂₂ by the synthesis circuit 18, the graph of the change in E ₂ becomes the E ₂₃ as shown in FIG. 11, for example.
This graph is obtained by horizontally shifting the graph by E _c in the negative direction of the vertical axis, and the output AM modulated wave is a synchronizing signal negative modulation method (i.e. , a method in which the carrier wave has a smaller average amplitude in the portion corresponding to the synchronization 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 18 is configured with a directional coupler, the phase can be changed by changing the connection terminals thereof). possible) For the same FM input wave,
The modulation polarity of the output AM wave can be easily set to positive or negative.

Since the frequency spectrum of _one wave of input FM signal is near the center frequency ₀ , even if the amplitude of the input wave at input terminal 11 changes somewhat, the two output amplitudes E ₁₁ and E ₁₂ of branching circuit 12 will also be at the same rate. fluctuate and therefore
G ₁ and G ₂ also fluctuate at the same rate, and therefore E ₂₁ and E ₂₂ also fluctuate at the same rate, but as is clear from Figure 9, when ₁ = ₀ , E ₂₃ remains at 0 and does not fluctuate. Therefore, the E ₂ amplitude in FIG. 10 or 11 is
The amplitude at ₁ = ₀ does not fluctuate, and there is little fluctuation near ₀ . Therefore, the FM-AM conversion circuit according to the present invention is less susceptible to noise due to amplitude fluctuations of the FM input wave than the conventional conversion circuit.

In the above explanation, as an example of the branching circuit 12, the 12th
The circuit example shown in the figure has been described, and in the same figure, 53 and 54 are series resonant circuits connected in parallel, but these can be replaced by parallel resonant circuits or band rejection filters connected in series.

13 and 14 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 13, 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. Further, in Fig. 14, 61 and 62 are a low-pass filter and a high-pass filter, and in Fig. 15, 63 and 64 are directional couplers, and ₁ and ₂ are the electrical lengths of each line. , and ₁ and ₂ differ by an appropriate length. Also, in Figure 17, 65 and 66
is a directional coupler or magic T, 67 is a resonant circuit, and 68 is a short-circuit line. Also, 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 various branching circuits described above or in the middle thereof. Now, regarding ₂ , the diode circuits 35 and 36 are connected in parallel, but
Even if each terminal of the circuit 35 or 36 is marked with a symbol as shown in FIG. 5 and connected in series for _two waves as illustrated in FIG. 18, the same operating characteristics as described above can be obtained. 81 and 82 are circuits for short-circuiting _{the first} wave and passing _{the second} wave to create a loop path through the diodes 13 and 14 for the _first wave, and 81 and 82 may be included in the circuit 17 or may be omitted. .

In FIG. 18, the connection order of one or both of the circuits 25, 35, and 81 and the circuits 26, 36, and 82 is reversed so that the circuits 81, 35, 25, or the circuit 8
Even if 2, 36, 26 are connected in this order, the same operating characteristics as described above can be obtained.

In the above description, even if the polarity of one or both of the diodes 13 and 14 is reversed, the same operating characteristics as described above can be obtained. Furthermore, the same operating characteristics as described above can be obtained by using a nonlinear element other than the diodes described above, such as a transistor or an electron tube, in place of the diodes 13 and 14, and utilizing the diode characteristics between the appropriate terminals. That is clear.

In addition to the circuit examples described above, the circuits 35 and 36 may be balanced circuits using two pairs of diodes as shown in FIG. 19, or dual circuits using four pairs of diodes as shown in FIG. It is clear that the same FM-AM conversion characteristics as described above can be obtained even with a balanced circuit.

As shown in FIG. 21, a diode 86 is combined with a directional circuit 85 such as a bridge circuit, a directional coupler, or a circulator, and changes in the reflection coefficient due to changes in the small signal impedance of the diode 86 are utilized. Also, a transfer characteristic similar to that shown in FIG. 8 can be obtained, and an FM-AM conversion characteristic similar to that described above can be obtained.

Note that the trap circuit 21, the bias power supply 27, the low-pass circuit 29, etc. may be added to the circuits of FIGS. 19, 20, and 21, as in the examples of the circuits 35 and 36.

Even if a nonlinear circuit such as a transistor amplification circuit or an electron tube amplification circuit is used in place of the diode circuits 35 and 36 in the above principle diagram, the same characteristics as described above can be obtained as explained below. That is, for example, in FIG.
If, for example, terminals 71 are connected to G, 72 to I, and 73 to H by using _transistor amplification circuits as shown in FIG. By wave circuit,
As shown in FIG. 6, the amplitudes of E ₁₁ and E ₁₂ change in response to frequency changes and are applied to the transistor circuit. Since this transistor circuit has non-linear characteristics, the waveform of _one wave at the input and output ends is distorted.
As a result, a DC component is generated in the input/output signal. 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. In addition, since the DC component changes depending on the amplitude of _one input wave, the input/output small signal impedance changes according to the amplitude change of _one input wave of the transistor circuit, and the operating point and branching of the transistor change. circuit 1
If the characteristics of 2 are set appropriately, the small signal impedance can be made to change characteristics similar to the small signal impedance of the diode shown in FIG. 7, and in the above example, the collector and emitter of the transistor It is possible to make the small signal impedance characteristic between
AM conversion characteristics can be obtained. Also, terminal 7
The combination of 1, 72, 73 and terminals G, H, I is:
Any combination other than the combinations described above can be used.

As illustrated in FIG. 23, the two terminals 75 and 76 are used as the same transistor electrode, and this second
If the circuit in Figure 3 is used in place of the circuits 35 and 36 in Figure 5, for example, and the terminal 75 is connected as I, the terminal 76 as G, and the terminal 77 as H, the result will be the same as the example in Figure 22. FM-AM conversion characteristics can be obtained. Although the transistor is used in a grounded emitter circuit in FIG. 23, it is clear that similar characteristics can be obtained by using a grounded base or a grounded collector. In addition, in the example shown in Fig. 23, two terminals, 75 and 76, are provided on the base terminal, but FM-AM can also be provided on any other terminal.
It is clear that conversion properties can be obtained.

Further, similarly to the above, it is also possible to add a trap circuit 21, a low-pass circuit 29, etc. to the transistor circuit.

Also, similar FM-AM conversion characteristics can be obtained by using field effect transistors, multipolar electron tubes, etc. in place of the transistors shown in FIGS. 22 and 23. Furthermore, even if a two-gate field effect transistor is used as shown in Fig. 24 and _two waves are applied to one gate and _one wave is applied to the other gate, the same characteristics as shown in Fig. 23 can be obtained. It will be done.

Although the above circuit has been exemplified using one transistor, etc., the same effect can be achieved using two or more or using other elements, such as a composite circuit of a diode and a transistor, as shown in FIGS. 25 and 26. It is clear that the properties are obtained. Note that in FIGS. 25 and 26, the diode 78 is connected to the base electrode of the transistor 79,
It can also be connected to other electrodes. Further, although the diodes are connected in parallel in FIGS. 25 and 26, they can also be connected in series. or,
79 can obtain similar characteristics with field effect transistors, electron tubes, etc. in addition to transistors. Further, similar characteristics can be obtained by inserting a resistor or other circuit element 87 in parallel or series between the diode 85 and the transistor 86 as illustrated in FIG.

In the transistor circuit described above, the high frequency signal is applied to the transistor, diode, etc. through the DC blocking capacitor.
It is clear that similar characteristics can be obtained using a high frequency transformer.

In the above description, an example has been shown in which transistor circuits are used as the circuits 35 and 36 in FIG. 5, but they can also be used in series connection as shown in FIG. 18 in the same manner as above. Also, it can be used in place of the diodes shown in FIGS. 19, 20, and 21.

As described above, the circuits 35 and 36 in the present invention are not limited to simply diode circuits, but may generally be non-linear circuits for _one wave.

In the principle diagram explained above, the distribution circuit 16 and the combination circuit 17 are used as directional couplers, but it goes without saying that the same characteristics can be obtained with a Magic-T or a bridge circuit, for example. , a hybrid transformer circuit such as the equivalent circuit shown in Fig. 28 may be used, or by changing the terminals used, a hybrid transformer circuit with connections as shown in Figs. 29 and 30 may be used.
Similar characteristics can be obtained with a transformer circuit, and furthermore,
A high frequency transformer circuit with a center point tap as shown in FIG. 31 or 32, a distributed constant distribution circuit as shown in FIG. 33, a circuit obtained by converting the circuit shown in FIG. 33 into a lumped constant type, Furthermore, a simple T-branch circuit as shown in FIG. 34 can also be used. Furthermore, the 34th
In the figure, l ₁ and l ₂ indicate appropriate electrical lengths. Furthermore, although the circuits described above are mainly shown as lumped constant equivalent circuits, they may also be constructed with distributed constant circuits such as stripline or conductive tube circuits. It is also possible to use a distribution or combination circuit using active elements as shown in FIG. Similar characteristics can also be obtained by inserting an attenuator, amplifier, isolator, etc. into the input or output portion of the above distribution or combination circuit.

It is also possible to equivalently satisfy the condition of the second equation by inserting lines of appropriate electrical length into the input/output terminals of the above combining or dividing circuit.

If there is a difference in the phase amount of the transfer characteristics between the nonlinear circuits 35 and 36, the difference in phase amount is incorporated into the phase amount of the distribution circuit 16 or the combining circuit 17, and each of the distribution or combining circuits is By setting the phase amount between the terminals and the electrical length of the insertion line, the condition of the second formula can be satisfied in the same way.

In the principle diagram described above, the combining circuit 18 is omitted and the output terminal of the combining circuit 17 is connected to the output terminal 19 as in the example of FIG. Synthesis circuit 17
If the attenuator 90 is inserted in the middle of the wave, the amplitude of _{the two} waves at the output of the combining circuit 17 will be attenuated as shown in FIG. 37, and the amplitude of E ₂₁ will be attenuated as shown in _FIG .
It is possible to shift the intersection of the graph of the output amplitude E ₂₃ , which is the composite of E ₂₂ , and _{the first} axis, and by appropriately shifting the resonant frequency of the branching circuit 12 in advance, the third
As shown in Fig. 7, it is possible to output _two waves of the necessary amplitude near the center frequency of input frequency ₁ , without the synthesis circuit 18 in the above principle diagram,
FM-AM conversion characteristics similar to those described above can be easily obtained using the circuit example described above. However, according to the principle diagram in Figure 36, 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 clear that the circuit is better than the conventional circuit. It is.

In FIG. 36, instead of inserting the attenuator 90, the amplitudes of E ₂₁ and E ₂₂ can be made unbalanced by making the distribution and combination amounts of the distribution circuit 16 and the combining circuit 17 unbalanced. , characteristics similar to those described above can be obtained. Similarly, by making the output amplitudes of the two output terminals of the branching circuit 12 different, the non-linear circuits 35 and 3
Even if the amplitude of _{the single} wave applied to 6 is made unbalanced, and as a result the small signal impedances R _d1 and R _d2 are made different, the magnitudes of E ₂₁ and E ₂₂ can be similarly made different. , characteristics similar to those described above can be obtained.

As shown in FIG. 38, the distribution circuit 16 and the synthesis circuit 17
Even if a bypass is provided between the _two waves by, for example, providing resistors 91 and 92, the nonlinear circuits 35 and 3
The transfer characteristics G ₁ and G ₂ of 6 can be made to be equivalently different, and similar FM-AM conversion characteristics can be obtained without the combining circuit 18 as described above.

In addition, in FIG. 38, 91 and 92 are not limited to simply resistors, but may also be inductors, capacitors, or other composite circuits.Also, even if these circuits are inserted in series with the nonlinear circuits 35 and 36, the same result can be obtained. characteristics are obtained.

Also, as in the examples in Figures 36 and 38, the output E ₂₁
Even if the output E ₂₂ is not made asymmetrical and the characteristics shown in Fig. 9 are maintained, the same result as above can be obtained by using only the frequency range smaller than or larger than ₀ in the graph of E ₂₃ in Fig. 9.
AM with high modulation degree by obtaining FM-AM conversion characteristics
5 or 18 can be omitted, for example.

As illustrated in FIG. 39, 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 diodes 13 and 14 is extracted from 101 as shown in FIG. input ₁
The FM-AM converter 102, _two- carrier oscillator 108, and mixer 103 according to the present invention can obtain a frequency discriminator characteristic in which the DC current amplitude changes with respect to the frequency change of the wave, as shown in the system diagram shown in FIG. 40, for example. , intermediate frequency amplifier 104, limiter 10
If a superheterotine 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 FM applied to the input terminal 107
Even if the center frequency of the wave changes, it is applied to the FM-AM converter 102 by automatic frequency control operation.
The center frequency of the FM wave is controlled to be constant, so that the average carrier wave amplitude of the AM output signal at the AM output terminal 19 can be maintained at a constant value regardless of fluctuations in the input FM wave.

As illustrated in FIG. 41 of the system diagram, if the output of the terminal 101 is taken out through a low frequency amplifier 110 or the like, the input/output modulated signal of the receiver can be monitored.

As illustrated in the system diagram Fig. 42, the FM signal input is turned off or the terminal 10 is turned off at the same time as the FM signal input.
1 to another external low frequency input signal to the low frequency amplifier 11
If applied through 1, etc., this low frequency signal can also change the current of the nonlinear circuit, change the small signal impedance, and AM modulate the carrier wave _2. This AM modulated wave can be applied to the terminal. It can be sent from 19.

Figure 39 shows the FM-AM illustrated in Figure 5 above.
Although the example in which the converter is provided with the low frequency coupling terminal 101 has been shown, the circuit example in FIG.
FM using non-linear circuits other than diodes
FM-AM in which the AM conversion device and the synthesis circuit 18 as explained in FIGS. 36 and 38 are omitted.
The conversion device can also be provided with the low frequency coupling terminal 101 in the same manner as Matsutaku, and can be used in a similar manner.

As shown in FIG. 43, the detection circuit 201 and the amplifier 20
2 and the level control circuit 203 detect the deviation in amplitude of _{the two-} wave output of the combining circuit 18, amplify it, and control the level of _{the two} carrier waves applied to the combining circuit 18. Circuit _18-2
The wave output amplitude can be automatically controlled to a preset value. For example, if the center frequency ₀ of _one input wave fluctuates for some reason, the center amplitude of the output AM wave will fluctuate, as is clear from the graph showing the conversion characteristics _{in FIG} . is FM modulated with a video signal as in the example shown in Figure 10, this is inconvenient because it causes the center amplitude of the output AM wave to fluctuate, and therefore the synchronized peak amplitude of the output AM wave to fluctuate. However, at this time, in the example of FIG.
By using a peak value detector as 1 and a DC amplifier with a time constant faster than the fluctuation period of the center frequency ₀ described above as 202, it is possible to maintain the synchronized peak amplitude of the output AM wave at a constant value. .

As shown in FIG. 44, the detector 211 and the signal detector 2
12 demodulates the modulated signal of the AM wave output from the combining circuit 18, detects the magnitude of a specific signal contained therein, and demodulates the modulated signal of the AM wave output from the combining circuit 18, and detects the magnitude of a specific signal contained therein. By controlling the magnitude of the carrier wave ₂ applied to the combining circuit 1,
The modulation amplitude of the output AM wave of No. 8 can be automatically controlled to the set value. That is, to explain with reference to FIG. 45 showing the FM-AM conversion characteristics, for example, _one input wave that is FM modulated with a 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 two} output waves 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, by detecting a decrease in the amplitude of the SIG2' synchronization signal and controlling and increasing the level of _{the two} carrier waves applied to the distribution circuit 16 according to the amount of change, the slope of the conversion characteristic can be applied.
Since it is proportional to the level of the ₂ carrier waves, the slope can be corrected from the conversion characteristic of 217 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 a multiplex signal, the magnitude of a specific signal in the multiplex signal is detected, and as described above, ₂
By controlling the applied level of the carrier wave, the output AM amplitude can be kept constant.

Instead of controlling the amount of _two carrier waves applied to the bridge circuit 16 as shown in FIG. 44, the same characteristics can be obtained by inserting a level control circuit 214 at the output of the combining circuit 17 as shown in FIG. . Also the fourth
As shown in Figure 7, the level control circuit 214 is connected to the branching circuit 1.
Even if it is inserted into the input section of 2 and controls the magnitude of the ₁ wave applied to the demultiplexing circuit 12, the slope of the conversion characteristic 216 can be changed in the same way as described above.
The output AM amplitude can be corrected.

If the correction illustrated in FIG. 43 and the correction illustrated in FIG. 44, FIG. 46, or FIG. 47 are performed simultaneously, the peak value and modulation degree of the output AM signal wave 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 48th
As shown in the figure, correction circuits 215, 216, 217, 218 such as attenuators or amplifiers with inverse temperature change characteristics
If you use , you can easily perform the same correction as above.

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]

Fig. 1 is a principle diagram showing a conventional FM-AM conversion device, Figs. 2, 3, and 4 are graphs showing characteristics of the conventional circuit, and Fig. 5 is a block diagram of an embodiment of the present invention.
6, 7, 8, 9, 10, and 11 are graphs showing the characteristics of the device of the present invention;
Figures 5, 16, and 17 are diagrams showing examples of branching circuits.
FIG. 8 is a block diagram of another embodiment of the present invention, the first
9, 20, 21, 22, 23, 24, 25, 2
Figures 6 and 27 are diagrams showing examples of nonlinear circuits, Figure 28,
Figures 29, 30, 31, 32, 33, 34, and 35 are examples of distribution or combination circuits, and Figures 36, 38, 39, and 4
0,41,42,43,44,46,47,48
The figure is a block diagram of still another embodiment of the present invention, and Figures 37 and 45 are graphs showing characteristic examples of the apparatus 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 distribution circuit for distributing and applying a carrier wave to be amplitude modulated to the two non-linear circuits;
a synthesizing circuit for synthesizing amplitude modulated carrier waves in two non-linear circuits, the frequency modulated signal applied to the branching circuit is amplitude modulated using the frequency applied to the distribution circuit as a carrier wave. A carrier wave conversion device characterized in that a signal is obtained from the combining circuit.