JP2015139208A - Digital amplitude modulation device and transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform impedance matching without performing disconnection and recoupling in a circuit where the impedance matching is necessary for a filter section, a matching section or the like.SOLUTION: A digital amplitude modulation device comprises: a plurality of power amplifiers being capable of performing ON/OFF control in response to a voltage amplitude level of a modulation signal, being connected in parallel, amplifying a carrier signal and outputting the carrier signal amplified; a synthesis section generating an amplitude modulation wave signal by synthesizing output of each of the plurality of power amplifiers; and a filter section performing filtering of the amplitude modulation wave signal generated by the synthesis section. Further, the filter section is configured so as to have a variable element capable of changing inductance or capacitance on the basis of impedance or characteristics calculated by the inductance or the capacitance presently set to the filter section.

Description

  Embodiments described herein relate generally to a digital amplitude modulation apparatus and a transmission system.

  Conventionally, medium-wave broadcasting has a plurality of power amplifiers arranged in parallel, and an amplified carrier signal is output by controlling on / off of the plurality of power amplifiers according to the voltage amplitude level of the modulation signal. The number of power amplifiers to be changed is changed, the output signal of the power amplifier in the on state is synthesized by the synthesis unit, and AM wave (Amplitude Modulation Wave) is filtered by filtering to remove unnecessary components by the filter unit There are known digital amplitude modulators for generating.

  When this type of digital amplitude modulation device is used for actual broadcasting, when the signal synthesized by the synthesis unit is transmitted from the transmission antenna via the filter unit, it cooperates with the filter unit constituting the digital amplitude modulation device. Therefore, it is necessary to provide a matching section that performs impedance matching.

US Pat. No. 4,580,111

  When performing impedance matching in these filter units and matching units, it was necessary to use a dedicated measuring device and to temporarily separate the filter unit and matching unit.

  Furthermore, in order to obtain characteristics such as distortion, efficiency, and spurious after impedance matching, it is necessary to perform measurement after combining these filter parts and matching parts. When certain characteristics do not satisfy the standard, there is a possibility that repeated work may occur.

  Accordingly, an object of the present invention is to provide a digital amplitude modulation device and a transmission system capable of performing impedance matching without disconnecting and recombining in a circuit that requires impedance matching, such as a filter unit and a matching unit. is there.

The digital amplitude modulation apparatus according to the embodiment is connected in parallel so that ON / OFF control is possible according to the voltage amplitude level of the modulation signal, and a plurality of power amplifiers that amplify and output the carrier signal and the output of each power amplifier are combined By doing so, a synthesizing unit that generates an amplitude-modulated wave signal and a filter unit that filters the amplitude-modulated wave signal generated by the synthesizing unit are provided.
The filter unit includes a variable element that can change the inductance or the capacitance based on the impedance or the characteristic calculated by the inductance or capacitance currently set in the filter unit.

FIG. 1 is a schematic configuration block diagram of a digital amplitude modulation apparatus according to an embodiment. FIG. 2 is an explanatory diagram of an example of a π-type low-pass filter using a variable element. FIG. 3 is an explanatory diagram of a more specific configuration of the digital amplitude modulation apparatus. FIG. 4 is a process flowchart of the impedance matching process procedure of the filter unit. FIG. 5 is an explanatory diagram of impedance matching. FIG. 6 is an explanatory diagram when matching is performed with efficiency priority. FIG. 7 is an explanatory diagram in the case where the impedance is varied from a reference point impedance within a certain norm. FIG. 8 is a process flowchart of a conventional impedance matching process. FIG. 9 is a schematic configuration block diagram of the transmission system according to the first embodiment. FIG. 10 is a process flowchart of the impedance matching process in the matching unit. FIG. 11 is a schematic configuration block diagram of a transmission system according to the second embodiment. FIG. 12 is a schematic configuration block diagram of a digital amplitude modulation apparatus according to the third embodiment. FIG. 13 is a flowchart of impedance measurement and adjustment processing according to the third embodiment. FIG. 14 is a schematic configuration block diagram of a transmission system according to the fourth embodiment. FIG. 15 is a schematic configuration block diagram of a transmission system according to the fifth embodiment. FIG. 16 is a schematic configuration block diagram of a protection unit according to the sixth embodiment.

Hereinafter, preferred embodiments will be described with reference to the drawings.
FIG. 1 is a schematic configuration block diagram of a digital amplitude modulation apparatus according to an embodiment.
As shown in FIG. 1, the digital amplitude modulation apparatus 100 is roughly divided into a modulation control unit 11, a power amplification unit 12, a synthesis unit 13, a filter unit 14, a carrier signal input terminal Tc, an audio signal input terminal Ts, and a signal output. A terminal Tout is provided.

A carrier signal Sc that is a transmission signal is input to the carrier signal input terminal Tc.
The audio signal Ss, which is a modulation signal, is input to the audio signal input terminal Ts.
From the signal output terminal Tout, an amplitude-modulated signal SAM that is impedance-matched and filtered after synthesis is output.

  The power amplifying unit 12 includes n power amplifiers (PA) 12-1 to 12-n that are connected in parallel and can be individually turned on / off. The carrier signal Sc input to the carrier signal input terminal Tc is distributed to the power amplifiers 12-1 to 12-n via the modulation control unit 11.

The power amplifiers 12-1 to 12-n are individually turned on (driven) by the on control from the modulation control unit 11. Then, the power amplification units 12-x (x: 1 to n) in the on state each amplify the carrier signal Sc to a predetermined level and output the amplified carrier signal Sac to the synthesis unit 13. Further, the power amplifiers 12-1 to 12-n are turned off (stopped) by the off control from the modulation control unit 11.
In the present embodiment, the carrier signal Sc and the control signal are used as a method for performing on / off control of the power amplifiers 12-1 to 12-n as shown in FIG. On the other hand, it is also possible to realize the on / off control by changing the phase difference of the carrier signal Sc. It is also possible to change the amplification level in the power amplifiers 12-1 to 12-n by changing the phase difference of the carrier signal Sc.

The synthesizer 13 synthesizes the amplified carrier signals Sac output from the power amplifiers 12-1 to 12-n in the on state, and outputs a synthesized carrier signal Ssac.
In the present embodiment, by adopting a variable element in the filter unit 14 of the digital amplitude modulation device 100 and the matching unit 15 connected to the subsequent stage of the digital amplitude modulation device 100, the inductance value and the capacitance value are kept live, that is, Realize a mechanism that can be changed while maintaining the combined state.

Examples of the variable element used in the present embodiment include a variable coil or a variable capacitor.
For example, a variable coil can be cited as a variable element that varies the inductance. In the case of a variable coil, the inductance value is changed by changing the effective number of turns or length of the coil, changing the amount of magnetic flux obstruction, magnetic permeability, or the like.

  Moreover, a variable capacitor is mentioned as a variable element which changes a capacitance. In the case of a variable capacitor, the capacitance value can be changed by changing the dielectric constant by changing the applied voltage and controlling the thickness of the depletion layer, or by rotating the mechanical shaft. A variable capacitor is used that changes the capacitance value by changing the area where the electrodes face each other and the distance between the electrodes.

FIG. 2 is an explanatory diagram of an example of a π-type low-pass filter using a variable element.
Further, in the π-type low-pass filter 30, as shown in FIG. 2, the variable coil 31 and the variable capacitors 32 and 33 are connected in a π-shape and combined to change the resistance component and reactance component of the impedance. To do.

  Furthermore, in the π-type low-pass filter, either a variable coil or a variable capacitor can be obtained by combining a rejector circuit, a trap circuit, a series resonant circuit, or a parallel resonant circuit connected to a transmitting antenna (not shown). It is also possible to change the resistance component and the reactance component of the impedance only.

  In the present embodiment, by employing a variable element such as the variable coil or variable capacitor as described above, impedance matching can be performed without separating them from the circuit.

  The filter unit 14 suppresses unnecessary components included in the combined carrier signal Ssac by filtering the combined carrier signal Ssac output from the combining unit 13. Furthermore, the filter unit 14 uses, for example, the above-described variable element (when the π-type low-pass filter 30 is configured, the variable coil 31 and the variable capacitors 32 and 33) so as to be 50Ω at the signal output terminal Tout. Impedance matching is performed, and an amplitude modulation signal SAM that is an amplitude-modulated RF band broadcast wave (AM wave) is output from the signal output terminal Tout.

In the case of the above example, a matching unit 15 for impedance matching of the transmission antenna input impedance to 50Ω is provided at the subsequent stage of the signal output terminal Tout.
That is, the impedance matching of the filter unit 14 is intended to connect the digital amplitude modulation device 100 and the matching unit 15 with a coaxial cable or the like, and the impedance matching of the matching unit 15 is illustrated in front of the matching unit 15. The purpose is not to connect to the transmitting antenna.

Therefore, the impedance matched by the filter unit 14 is set to a value of 50Ω because the characteristic impedance of a general coaxial cable or the like is 50Ω.
In addition, since a rejector circuit, a trap circuit, or the like is inserted between the signal output terminal Tout and a transmission antenna (not shown), the impedance matched by the matching unit 15 is a value that takes into account the rejector circuit, the trap circuit, and the like. Set to

FIG. 3 is an explanatory diagram of a more specific configuration of the digital amplitude modulation apparatus.
In this embodiment, as shown in FIG. 3, a pickup unit (detection unit) is further provided before and after the filter unit 14 and the subsequent matching unit 15 of the digital amplitude modulation apparatus 100A, and the amplitude is detected by a resistor, a capacitor, or a current transformer. The voltage component and the current component of the modulated RF band broadcast wave (AM wave) are picked up (detected), and the impedance is calculated while the connection state of the filter unit 14 or the matching unit 15 is maintained.

As pickup units corresponding to the filter unit 14 of the digital amplitude modulation apparatus 100A, two pickup units 17A and 17B are assumed in this embodiment.
However, either the front pickup unit 17A or the rear pickup unit 17B may be used, and only the impedance of either the input side or the output side of the filter unit 14 may be calculated. Alternatively, three or more pickup units can be provided as necessary (for example, two voltage pickup units, two current pickup units, etc.).

  According to the above configuration, the filter unit 14 (or the matching unit 15) and other circuit units are also calculated by calculating characteristics such as distortion rate and spurious based on the voltage component and current component picked up by the pickup unit. Separation is not necessary, and furthermore, it is possible to suppress the occurrence of repetitive work by simultaneously observing impedance and characteristics (such as distortion rate and spurious).

  It is also possible to provide a pickup unit for picking up voltage components and current components for calculation of impedance and characteristics between the filter unit 14 and the matching unit 15 so that the filter unit 14 and the matching unit 15 can share the pickup unit. It is.

  Furthermore, it is necessary to provide a pickup unit for each of the calculation circuits (in the example of FIG. 3, the impedance calculation unit 42, the characteristic calculation unit 43, and the protection unit 44) that performs calculation based on the output signal of the pickup unit. In the embodiment of FIG. 3, an input signal selection switching unit (selection switching circuit) 41 is provided at the input stage of the arithmetic circuit so as to minimize the number of pickup units.

  Furthermore, a λ / 4 transformer or the like is used for the configuration of the pickup unit, and the impedance or filter unit 14 can be obtained only with the voltage value V1 and the voltage value V2 (corresponding to the current value) whose phase is π / 2 away from the voltage value V1. Alternatively, it may be configured to calculate characteristics such as the characteristics of the matching unit 15.

  In addition, the display unit 46 is connected to the arithmetic circuit (in the example of FIG. 3, the impedance calculation unit 42, the characteristic calculation unit 43, and the protection unit 44) via the control unit 45, and the impedance and filter unit 14 as the calculation result Alternatively, the characteristics of the matching unit 15 can be displayed, or the communication unit 47 can be connected to transmit information on the calculation result to the external control device.

As a characteristic of the digital amplitude modulation apparatus 100, the efficiency can be calculated from information from a power supply unit (not shown).
As described above, the pickup unit of the present embodiment is also used as the pickup unit of the protection unit 44 that protects the power amplifiers 12-1 to 12-n constituting the power amplification unit. An increase in circuit scale can be suppressed.

Here, as an example, impedance matching in the filter unit 14 will be described in detail.
The filter unit 14 is usually configured as a band pass filter (BPF) or a low pass filter (LPF). However, in the following description, the case where the filter unit 14 is configured as a band pass filter (BPF) will be described as an example. To do.

FIG. 4 is a process flowchart of the impedance matching process procedure of the filter unit.
Based on the information from the pickup unit, the current input impedance of the BPF as the filter unit 14 is calculated (step S11), and the characteristics (output power, efficiency, distortion rate, spurious) are calculated (step S12).

Subsequently, based on the characteristic calculation result, it is determined whether the characteristic is within the standard, that is, whether the characteristic satisfies the standard (step S13).
If it is determined in step S13 that the characteristic satisfies the standard (step S13; Yes), impedance matching is terminated.

  On the other hand, if it is determined in step S13 that the characteristics do not satisfy the standard (step S13; No), the variable element is controlled to change the input impedance of the BPF as the filter unit 14 (step S14).

  Then, the process again proceeds to step S12, the characteristic of the input impedance of the BPF as the changed filter unit 14 is calculated (step S12), and it is determined whether or not the characteristic satisfies the standard (step S13). .

  If it is determined in step S13 that the characteristics are not satisfied again, the input impedance of the BPF as the filter unit 14 is further changed (step S14), and the same processing is repeated until the standard is satisfied.

Specifically, it is assumed that the output impedance of the BPF as the filter unit 14 is 50 + j0Ω, and the current input impedance of the BPF as the filter unit 14 is 40−j10Ω.
The target characteristics are an efficiency of 75% or more and a distortion rate of 2.5% or less.
For example, when the input impedance of the BPF as the filter unit 14 is 40-j10Ω, the efficiency is 80%, but when the distortion is calculated as 3%, the BPF as the filter unit 14 is configured. The variable element is changed to change the input impedance of the BPF.

  When the BPF input impedance is 40-j5Ω, the efficiency is calculated as 81% and the distortion rate is 3.2%. When the BPF input impedance is 40-j15Ω, the efficiency is 76% and the distortion rate is Assume 2%.

FIG. 5 is an explanatory diagram of impedance matching.
As shown in FIG. 5, it is the simplest way to change the impedance in four directions (the step amount is an arbitrary value) as shown in FIG. 5. Generally, the efficiency optimum point and the distortion optimum point do not match. While satisfying the standard, either one will be given priority.

In this description, priority is given to the distortion rate. For example, if the input impedance (40-j12.5Ω) of a certain BFP is calculated as 78% efficiency and 2.3% distortion rate, BPF Is determined to be the optimum point.
As another method, a method of measuring eight points around the reference impedance and performing matching with priority on efficiency will be described.

FIG. 6 is an explanatory diagram when matching is performed with efficiency priority.
When the unit impedance in the R direction / X direction is changed from the reference point impedance (± 0 step), there is no change in characteristics, and a point where efficiency is improved can be selected.

FIG. 7 is an explanatory diagram in the case where the impedance is varied from a reference point impedance within a certain norm.
As shown in FIG. 7, a method is also conceivable in which measurement is carried out at an angle of 45 ° with a constant norm as a range from the impedance serving as a reference point (center point). In this case, a plurality of norms may exist.

FIG. 8 is a process flowchart of a conventional impedance matching process.
Here, a conventional impedance measurement and adjustment process will be described with reference to FIG.
Conventionally, when performing impedance measurement and adjustment processing, first, the BPF as the filter unit 14 is disconnected (step S101), and the input impedance of the BPF is calculated (step S102).

Subsequently, the BPF as the filter unit 14 is connected again (step S103), and characteristics such as output power, efficiency, distortion, and spurious are calculated (step S104).
Then, it is determined whether or not the characteristic calculated in step S104 is within the standard (step S105).
If it is determined in step S105 that the calculated characteristic is within the standard (step S105; Yes), the process ends.

  However, when the characteristic calculated in the determination in step S105 is out of the standard (step S105; No), the BPF as the filter unit 14 is disconnected (step S106), and the input impedance of the BPF is changed (step S107). The process proceeds to step S10 again, and the same process is repeated until the characteristics fall within the standard.

  As described above, in the conventional method, since the measurement and adjustment of the impedance requires disconnection and connection of the BPF as the filter unit 14, as shown in FIG. As shown in FIG. 6, the time required to calculate all 8 points in ± 1 step, or the time required to calculate a constant norm range as shown in FIG. It is easy to see that the BPF is very large compared to the proposed method in which disconnection and connection of the BPF are not required.

[1] First Embodiment FIG. 9 is a schematic configuration block diagram of a transmission system according to a first embodiment.
The transmission system 200 is connected to the digital amplitude modulation device 100 of the first embodiment and the signal output terminal Tout of the digital amplitude modulation device 100, and is disposed in the previous stage of the matching unit 15, and the voltage value of the input signal of the matching unit 15 and A pre-pickup unit 23 for detecting a current value, a post-pickup unit 25 that is arranged after the matching unit 15 and detects a voltage value and a current value of an output signal of the matching unit 15, and a pre-pickup The selection switching unit 41 that selectively outputs the output signal of the unit 23 or the output signal of the rear pickup unit 24, and the output signal of the front pickup unit 23 output from the selection switching unit 41 or the output of the rear pickup unit 25 Based on one of the signals, either the input impedance of the matching unit 15 or the output impedance of the matching unit 15 is calculated and output. Various information for controlling the input impedance of the matching unit 15 and the output impedance of the matching unit 15 calculated by the impedance calculation unit 26 are displayed on the display unit 28, or via the communication unit 29. And a control unit 27 that notifies an external control device (not shown).

In this case, the two pickup parts of the front pickup part 23 and the rear pickup part 25 are provided corresponding to the matching part 15, but it is also possible to provide only one of them.
In addition, the front pickup unit 23 may be configured to be shared with the rear pickup unit 22 that is located after the filter unit 14 of the digital amplitude modulation apparatus 100. Further, the selection switching unit 41, the impedance calculation unit 26, the control unit 27, the display unit 28, and the communication unit 29 are shown in FIG. 3 with the selection switching unit 41, the impedance calculation unit 42, the control unit 45, the display unit 46, and It can also be configured to be shared with the communication unit 47.

FIG. 10 is a process flowchart of the impedance matching process in the matching unit.
When a variable element is employed for the matching unit 15, the impedance matching method is as follows.
First, the impedance calculation unit 26 calculates the impedance of the matching unit 15 based on information from the front pickup unit 23 and the rear pickup unit 25 (step S21), and characteristics (output power, efficiency, distortion rate, spurious) Is calculated (step S22).

Subsequently, based on the characteristic calculation result, it is determined whether the characteristic is within the standard, that is, whether the characteristic satisfies the standard (step S23).
If it is determined in step S23 that the characteristics satisfy the standard (step S23; Yes), impedance matching is terminated.

  On the other hand, if the characteristic does not satisfy the standard in the determination in step S23 (step S23; No), the inductance of the variable coil (L), which is a variable element constituting the LPF as the matching unit 15, and the variable capacitor (C ) To control the input impedance of the LPF as the matching unit 15 (step S24).

And it is discriminate | determined whether the impedance of LPF as the matching part 15 after a change is target impedance (step S25).
In the determination of step S25, when the impedance of the LPF as the matching unit 15 after the change is not the target impedance (step S25; No), the process is transferred again to step S24, and the same process is performed thereafter. Do.
On the other hand, in the determination of step S25, when the impedance of the LPF as the matching unit 15 after the change is the target impedance (step S25; Yes), the characteristics (output power, efficiency, The distortion and spurious are measured (step S26), and it is determined whether or not the characteristics satisfy the standard (step S27).

If it is determined in step S27 that the characteristics do not satisfy the standard again (step S27; No), the impedance of the LPF as the matching unit 15 is further changed (step S24), and the same processing is repeated until the standard is satisfied. It will be.
On the other hand, if it is determined in step S27 that the characteristic satisfies the standard (step S27; Yes), the process ends.

Hereinafter, the process will be described more specifically.
For example, it is assumed that the antenna impedance is 200 + j300Ω and the input impedance of the matching unit 15 is 50 + j5Ω. Since the target impedance is 50 + j0Ω, the impedance of the matching unit 15 is changed.

Then, it is determined whether or not the characteristics satisfy the standard under the condition that the impedance of the matching unit 15 after the change is 50 + j0Ω.
If the characteristics satisfy the standard, the impedance matching ends.
On the other hand, if the standard is not satisfied, the impedance of the LPF as the matching unit 15 is changed, and the point having the standard is searched again by the same procedure.

[2] Second Embodiment Next, a second embodiment will be described.
In a transmission system used for a digital amplitude modulation device and a matching unit used for transmission of medium wave broadcasting, a redundant system is often configured to ensure reliability as a mechanism for continuing broadcasting.

  In general, a working standby system having two digital amplitude modulation devices is adopted, an output switching unit that controls which output signal of the digital amplitude modulation device is selected, an audio system device that distributes an audio system, Generally, it is configured in combination with an external control device that controls the control. In addition, it can be configured in combination with an oscillation system device for distributing a carrier signal or a dummy load system circuit. In the active standby system, which digital amplitude modulation device is generally operated during operation and the other is in a standby state, for maintenance / repair, etc., it is connected to a dummy load system circuit for characteristic evaluation. The configuration is possible.

FIG. 11 is a schematic configuration block diagram of a transmission system according to the second embodiment.
As shown in FIG. 11, the transmission system 200A of the second embodiment is a combination of two systems of digital amplitude modulation devices 100A to which the audio signal Sc is input from the audio system device 35 and one system of the matching unit 15A. The current backup method is adopted.

  In this case, the output switching unit 24 for switching the two systems of digital amplitude modulation devices 100A is provided in the preceding stage of the matching unit 15A, and the post pickup unit 25 and the impedance calculation unit 26 are provided in the subsequent stage of the matching unit 15A. In addition, the matching unit 15, the post pickup unit 25, and the impedance calculation unit 26 are shared by the two systems of digital amplitude modulation devices 100A.

The output switching unit 24 connects either one of the two systems of digital amplitude modulation devices 100A to the matching unit 15A.
As a result, the post-pickup unit 25 detects the voltage component and current component of the matching unit 15 </ b> A and outputs them to the impedance calculation unit 26.

  The impedance calculation unit 26 employs a configuration in which the impedance of the matching unit 15A is calculated using the voltage component and current component picked up (detected) by the post pickup unit 25 and displayed on the external control device 36.

In the above configuration, the front pickup unit 23 can be provided separately, and the impedance calculation unit 26 can be incorporated in the external control device 36. Further, a configuration in which a display system device is provided separately from the external control device 36 is also conceivable. It is also possible to take a configuration in which a plurality of matching sections 15A are provided, and the post pickup section 25 is provided with a switching section so that the plurality of matching sections can be shared.
Furthermore, in order to measure the impedance between the variable elements (intermediate point) of the matching unit, an intermediate pickup unit in which the pickup unit is placed between the input end and the output end can be considered.

As for the impedance calculation method, it is common to set the relationship between the reference voltage waveform, current waveform, and impedance in advance, and calculate the current impedance from the amount of change in amplitude and phase of the voltage waveform and current waveform. Is. Of course, not only a combination of a voltage waveform and a current waveform, but also a combination of a voltage waveform V1 and a voltage waveform V2 whose phase is separated from the V1 by π / 2 is possible.
Further, as a mechanism for confirming the constant of the variable element, for example, a mechanism for confirming the capacitance value by measuring a voltage applied to the variable capacitor may be combined.

[3] Third Embodiment FIG. 12 is a schematic configuration block diagram of a digital amplitude modulation apparatus according to a third embodiment.
12 is different from the first embodiment of FIG. 3 in that the digital amplitude modulation apparatus 100B has an inductance element and a capacitance constituting the filter unit 14 based on the impedance calculation result and the characteristic calculation result of the filter unit 14. The driving operation unit 48 and the driving device 49 are provided for automatically adjusting impedance and characteristics by electrically or mechanically driving variable elements such as elements.

FIG. 13 is a flowchart of impedance measurement and adjustment processing according to the third embodiment.
First, the impedance calculation unit 42 measures (calculates) the impedance of the filter unit 14 based on information from the front pickup unit 17A and the rear pickup unit 17B (step S31).
Subsequently, the characteristic calculation unit 43 calculates characteristics (output power, efficiency, distortion, spurious) based on information from the front pickup unit 17A and the rear pickup unit 17B (step S32).

Subsequently, based on the characteristic calculation result, it is determined whether the characteristic is within the standard, that is, whether the characteristic satisfies the standard (step S33).
If it is determined in step S33 that the characteristics satisfy the standard (step S33; Yes), impedance matching is terminated.

  On the other hand, if it is determined in step S33 that the characteristics do not satisfy the standard (step S33; No), the inductance of the variable coil (L), which is a variable element constituting the BPF as the filter unit 14, and the variable capacitor ( The capacitance of C) is changed (step S34).

  Then, based on the calculation results of the impedance and characteristics, the drive calculation unit 48 is a mechanism part that changes the position of the flapper for changing the amount of hindering the magnetic flux of the coil in the variable coil, and the area where the electrodes in the variable capacitor face each other. Further, the driving amount of the driving device (actuator) 49 corresponding to each mechanism portion for rotating the shaft for changing the distance between the electrodes is calculated, and drive control is performed (step S35).

  Subsequently, the control unit 45 determines whether or not the impedance of the LPF as the filter unit 14 after the drive control of the drive device 49 is a target impedance (step S36).

  In the determination of step S36, when the impedance of the BPF as the filter unit 14 after the drive control of the driving device 49 is not the target impedance (step S36; No), the process is transferred again to step S35, Thereafter, the same processing is performed.

  On the other hand, in the determination of step S36, when the impedance of the BPF as the filter unit 14 after the drive control of the drive device 49 is the target impedance (step S36; Yes), the characteristics (BPF as the filter unit 14) ( Output power, efficiency, distortion, and spurious are measured (step S37), and it is determined whether or not the characteristics satisfy the standard (step S38).

If it is determined in step S38 that the characteristics do not satisfy the standard again (step S38; No), the impedance of the BPF as the filter unit 14 is further changed (step S34), and the same processing is repeated until the standard is satisfied. It will be.
On the other hand, if it is determined in step S38 that the characteristics satisfy the standard (step S38; Yes), the process ends.

  As described above, according to the third embodiment, the mechanism portion that changes the position of the flapper for changing the amount of hindering the magnetic flux of the coil in the variable coil, the area where the electrodes in the variable capacitor face each other, A driving device (actuator) is combined with a mechanism portion for rotating a shaft for changing the distance between the electrodes, and automatic adjustment to an optimum point becomes possible while checking characteristics.

[4] Fourth Embodiment FIG. 14 is a schematic configuration block diagram of a transmission system according to a fourth embodiment.
As shown in FIG. 14, the transmission system 200B according to the fourth embodiment is a combination of two systems of digital amplitude modulation apparatus 100B having the same configuration as the digital amplitude modulation apparatus of the third embodiment and one system of matching unit 15A. The current backup method is adopted.

  In this case, an output switching unit 24 for switching the two systems of digital amplitude modulation devices 100B is provided in front of the matching unit 15A, and a post pickup unit 25, an impedance calculation unit 26, and a matching unit 15A are configured in the subsequent stage of the matching unit 15A. A matching operation unit 51 and a driving device 52 for automatically adjusting impedance and characteristics by electrically or mechanically driving a variable element such as an inductance element or a capacitance element are employed. 15A, the post-pickup unit 25, the impedance calculation unit 26, the drive calculation unit 51, and the drive device 52 are shared by the two systems of digital amplitude modulation devices 100B.

Then, one of the two systems of digital amplitude modulation devices 100B is connected to the matching unit 15A by the output switching unit 24.
As a result, the post-pickup unit 25 detects the voltage component and current component of the matching unit 15 </ b> A and outputs the detected voltage component and current component to the impedance calculation unit 26.

  The impedance calculation unit 26 calculates the impedance of the matching unit 15A using the voltage component and current component picked up (detected) by the post-pickup unit 25, displays the impedance on the external control device 36, and sets the impedance of the matching unit 15A. A configuration for outputting to the drive calculation unit 51 is adopted.

  Thereby, based on the input impedance, the drive calculation unit 51 can change the position of the flapper for changing the amount of interference with the magnetic flux of the coil in the variable coil constituting the matching unit 15A, the variable capacitor The drive amount of the drive device (actuator) 52 corresponding to the mechanism portion for rotating the shaft for changing the area where the electrodes face each other and the distance between the electrodes is calculated, and drive control is performed.

  As described above, according to the fourth embodiment, in addition to automatic impedance adjustment in the digital amplitude modulation apparatus 100B, automatic adjustment can be performed on the matching unit 15A with the same mechanism.

  As a result, for example, for transmission antenna input impedance due to snowfall, etc., and for fluctuations in output power that occur due to fluctuations in the filter unit output side impedance and matching unit input side impedance due to changes in the coil / capacitor constant when temperature changes, Automatic adjustment can reduce output signal fluctuation.

In addition, stress on a circuit such as a power amplifier can be reduced by bringing the standing wave ratio and the like closer to the matching state.
Further, as a result, it is possible to use an inexpensive and small capacitor as compared with the case where a capacitor having excellent temperature characteristics is used.

[5] Fifth Embodiment FIG. 15 is a schematic configuration block diagram of a transmission system according to a fifth embodiment.
The transmission system 200C according to the fifth embodiment is an active standby transmission system that assumes a disaster or the like, and includes a pickup unit 25A that detects a voltage value or a current value for impedance measurement, and is connected to a transmission antenna 57. The matching unit 15C has two systems, and for each matching unit 15C, the impedance calculation unit 26A, the drive calculation unit 51, and the drive device 52 corresponding to the impedance calculation unit 26, the drive calculation unit 51, and the drive device 52 of the fourth embodiment are provided. During normal operation, it operates as a working backup method.

In other words, during operation, one of the digital amplitude modulation devices 100B and one of the matching units 15C operate, and the other is in a standby state. In this case, the carrier signal Sc that is a transmission signal is input from the oscillation system device 71 to the carrier signal input terminal Tc of both the digital amplitude modulation apparatuses 100B, and the modulation is performed from the audio system device 35 to the audio signal input terminal Ts. An audio signal Ss as a signal is input.
However, it is possible to operate as a 2-input / 2-output compatible transmission system 200C in the event of an emergency such as a disaster.

  In this case, two completely independent transmission systems can be driven by changing the audio signal or carrier frequency on one input side to a signal and frequency different from the other.

  After that, by performing automatic adjustment at the specified frequency by the drive calculation units 48 and 55, for example, when an abnormality occurs in the transmission system for wide area broadcasting in an area where wide area broadcasting and prefectural area broadcasting can be heard. However, broadcasting can be covered by using this transmission system 200C in a station that transmits prefectural broadcasting.

  In this case, the audio signal may be the same program, or depending on the case, it is possible to receive an interrupt or broadcast wave on the Internet line, etc., and retransmit it at a different frequency, so that it can be relayed, It is also possible to support live broadcasting at the transmitting station. In this example, two examples of the matching unit 15C are assumed, but there may be a case where there are three or more matching units 15C in the active standby method, and a combination of switching of the matching unit 15C and automatic adjustment may be considered.

In this case, the modulation control unit 11, the impedance calculation unit, the characteristic calculation unit, the drive calculation unit, and the like can be realized by a single calculation unit (CPU, FPGA / ASIC, etc.), and latency, load / redundancy can be reduced. It may be realized with a plurality of arithmetic units.
A plurality of inputs such as three inputs and three outputs are possible, and a change to an FM modulation method using digital amplitude modulation and a change in output power and frequency can be realized by an automatic adjustment function. Furthermore, in order to strengthen the cooperation with the power supply facility in the event of a disaster, the operation can be performed while adjusting the output power by the automatic adjustment function according to the remaining power that can be supplied.

[6] Sixth Embodiment The sixth embodiment is an embodiment applicable to any of the first to fifth embodiments described above, and a protection unit used in place of the protection unit 44 in each embodiment. 44A is an embodiment that can be surely adapted to a sudden change such as a lightning strike.

FIG. 16 is a schematic configuration block diagram of a protection unit according to the sixth embodiment.
The protection unit 44A according to the sixth embodiment includes a distribution unit 61 that distributes the detection result signal of the pickup unit output from the selection switching unit 41, and the detection result signal distributed by the distribution unit 61 is fixed by a comparator such as an analog IC. A protection index that monitors a protection index such as a wave ratio and configures the instantaneous stop circuit 62 that controls the instantaneous stop and the detection result signal distributed by the distribution unit 61 as a mixed circuit of an analog IC and a digital IC, and performs the calculation of the protection index An index calculation unit 63, a stop processing unit 64 that repeatedly stops and returns all the power amplifiers 12-1 to 12-n according to the size of the protection index that is a calculation result of the protection index calculation unit 63, and a stop Stops the power amplifiers 12-1 to 12-n that are actually driven according to the magnitude of the protection index, which is the calculation result of the protection index calculation unit 63, when the processing unit 64 is not operating. A reducer section 65 to perform fine return individually, and a.

  According to the above configuration, the control unit 45 performs control based on the output result of the stop processing unit 64 or the reduction processing unit 65 without performing calculation by itself, and the power amplifiers 12-1 to 12-n. Can be protected, and the control load of the control unit 45 can be reduced.

Furthermore, it is possible to reduce the protection delay due to the operation latency in the control unit 45.
In this case, as described in the third to fifth embodiments, by performing automatic adjustment of impedance and characteristics, it is possible to minimize deterioration of characteristics when protection is performed. It becomes possible.

[7] Effects of Embodiments As described above, according to each embodiment, in circuits that require impedance matching, such as a filter unit and a matching unit, these circuits are connected when the circuit is actually driven. Impedance matching can be performed without disconnecting and reconnecting to other circuits.

[8] Modification of Embodiment The control program executed by the digital amplitude modulation apparatus or the transmission system of this embodiment is an installable or executable file, such as a CD-ROM, a flexible disk (FD), a CD. It may be provided by being recorded on a computer-readable recording medium such as -R or DVD (Digital Versatile Disk).

Further, the control program executed by the digital amplitude modulation apparatus or transmission system of the present embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. good. In addition, a control program executed by the digital amplitude modulation apparatus or transmission system of the present embodiment may be provided or distributed via a network such as the Internet.
Further, the control program for the digital amplitude modulation apparatus or the transmission system according to the present embodiment may be provided by being incorporated in advance in a ROM or the like.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

100, 100A, 100B Digital amplitude modulation device 200, 200B, 200C Transmission system 11 Modulation control unit 12 Power amplification unit 12-1 to 12-n Power amplifier 13 Synthesis unit 14 Filter unit 15, 15A, 15C Matching unit 17A Pre-pickup Unit 17B Post-pickup unit 24 Output switching unit 25 Post-pickup unit 25A Pickup unit 26, 26A, 42 Impedance calculation unit 27 Control unit 28 Display unit 29 Communication unit 30 π-type low-pass filter 31 Variable coil 32 Variable capacitor 41 Selective switching Unit 43 Characteristic calculation unit 44, 44A Protection unit 45 Control unit 46 Display unit 47 Communication unit 48, 51, 55 Drive calculation unit 49, 52, 56 Drive device 57 Sending antenna 61 Distribution unit 62 Instantaneous stop circuit 63 Protection index calculation unit 64 Stop processing part 6 Reducer unit SAM amplitude modulation signal Sac amplified carrier signal Sc carrier signal Ssac synthetic carrier signal Tc carrier signal input terminal Tout signal output terminal Ts audio signal input terminal

Claims (11)

A plurality of power amplifiers connected in parallel that can be controlled on / off according to the voltage amplitude level of the modulation signal, and amplifying and outputting the carrier signal;
A combining unit that generates an amplitude-modulated wave signal by combining the outputs of the power amplifiers;
A filter unit that performs filtering of the amplitude-modulated wave signal generated by the synthesis unit, and
The filter unit is configured to include a variable element capable of changing the inductance or the capacitance based on the impedance or the characteristic calculated by the inductance or capacitance currently set in the filter unit.
Digital amplitude modulator. An impedance calculation unit that calculates an input impedance or an output impedance based on an inductance or capacitance currently set in the filter unit;
The digital amplitude modulation apparatus according to claim 1. A characteristic calculation unit that calculates the characteristic when using the inductance or capacitance currently set in the filter unit by calculation,
The digital amplitude modulation apparatus according to claim 1 or 2. An impedance calculation unit for calculating an input impedance or an output impedance based on an inductance or capacitance currently set in the filter unit; and
A characteristic calculation unit that calculates the characteristic when using the inductance or capacitance currently set in the filter unit;
A driving device for driving a variable element constituting the filter unit;
Based on the input impedance or output impedance and the characteristics, a drive arithmetic unit that controls the drive device;
The digital amplitude modulation apparatus according to claim 1, further comprising: The characteristics include efficiency and distortion rate;
The variable element changes inductance or capacitance in favor of efficiency out of the efficiency and distortion rate.
The digital amplitude modulation apparatus according to claim 3 or 4. The characteristics include at least one of output power, efficiency, distortion, and spurious.
The digital amplitude modulation apparatus according to claim 3 or 4. The filter unit changes the inductance or capacitance of the variable element in cooperation with a matching unit, a filter, a rejector, or a trap circuit connected to a subsequent stage of the digital amplitude modulation device.
The digital amplitude modulation device according to any one of claims 1 to 6. Configured as an analog circuit, based on the input impedance or output impedance of the filter unit, a momentary stop circuit that performs processing for turning off all the amplification units, and
Configured as a composite circuit of an analog circuit and a digital circuit, performing a calculation based on the input impedance or the output impedance of the filter unit, and outputting a protection index;
A stop processing unit that performs a process of repeatedly stopping and returning all the power amplifiers based on the protection index;
A reduction processing unit that operates exclusively with the stop processing unit, and performs processing for individually stopping and returning the power amplifier that is actually driven based on the protection index;
A control unit that performs on / off control of the plurality of power amplifiers based on processing results of the instantaneous stop open circuit, the stop processing unit, and the reduction processing unit;
A digital amplitude modulation apparatus according to claim 1, comprising: A digital amplitude modulation device according to any one of claims 1 to 8,
A matching unit that performs impedance matching between the digital amplitude modulation device and the transmission antenna,
The matching unit is configured to include a variable element capable of changing an inductance or a capacitance based on the impedance calculated for the matching unit.
Transmission system. An impedance calculation unit that calculates the input impedance or output impedance of the matching unit by calculation,
The transmission system according to claim 9. A second driving device for driving a variable element constituting the matching unit;
A second drive calculation unit for controlling the second drive device based on the impedance;
The transmission system according to claim 9 or 10, further comprising:

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