Radio transmitter output controller

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to an output control device for a multicarrier type digital wireless transmitter. The multi-carrier system is a system in which a single wireless communication system uses different carriers (carrier waves) to transmit and receive a plurality of modulated waves at the same time, which improves economic efficiency.

【0002】

[Conventional technology]

As shown in the frequency spectrum of FIG. 10, in the multi-carrier system, in each wireless communication system, for example, three different carriers are used for transmission / reception, and the frequency bands occupied by each wireless communication system are adjacent to each other. Have been placed.

【0003】

[Problems to be Solved by the Invention]

On the other hand, the frequency vs. output characteristics of the transmitted wave generated in a certain wireless communication system are shown by solid lines in FIG.

【0004】

By the way, as the amplifier or the like in the transmitter of the wireless communication system deteriorates, cross-modulation occurs, and cross-modulation distortion as shown by the broken line in FIG. 11 occurs. This cross-modulation distortion causes deterioration of line quality and line disconnection in the own wireless communication system, but also this cross-modulation distortion extends to the frequency band of the adjacent wireless communication system as shown in FIG. It adversely affects the line quality of the adjacent wireless communication system and leads to line disconnection.

【0005】

Since a failure has occurred in the own wireless communication system, it is unavoidable that the line quality deteriorates or the line is disconnected in the own wireless communication system, but originally, the adjacent wireless that does not include the faulty part. There was a request to avoid only the deterioration of line quality and line disconnection in the communication system.

【0006】

However, conventionally, in the multi-carrier type digital wireless transmitter, no measures have been taken against the influence of such cross-modulation distortion affecting the adjacent wireless communication system.

【0007】

The present invention has been made in view of these points, and an object of the present invention is to provide a wireless transmitter output control device that prevents deterioration of line quality and line disconnection of an adjacent wireless communication system due to cross-modulation distortion. And.

【0008】

[Means for solving problems]

In the present invention, in order to achieve the above object, as shown in FIG. 1, the intermodulation distortion amount detecting means 2 for detecting the intermodulation distortion amount included in the output of the wireless transmitter 1 and the intermodulation distortion amount detecting means 2 Provided is a wireless transmitter output control device characterized by having an output control means 3 for controlling the output of the wireless transmitter 1 based on the amount of cross-modulation distortion detected by the above.

【0009】

Further, the output control means 3 has the intermodulation strain amount detected as a result of comparison between the comparison means 3a for comparing the intermodulation distortion amount detected by the intermodulation distortion amount detecting means 2 with a predetermined value and the comparison means 3a. Includes an output level lowering means 3b that lowers the output level of the wireless transmitter 1 when is larger than the above predetermined value.

【0010】

Further, the output control means 3 has a cross-modulation distortion amount detected by the cross-modulation distortion amount detection means 2 as a result of comparison by the comparison means 3a after the output level of the wireless transmitter 1 is lowered by the output level lowering means 3b. Further includes an output blocking means 3c that blocks the output of the wireless transmitter 1 when is larger than the above predetermined value.

【0011】

[Action]

In the above configuration, first, the intermodulation distortion amount detecting means 2 detects the intermodulation distortion amount included in the output of the wireless transmitter 1. Then, the output control means 3 controls the output of the wireless transmitter 1 based on the cross-modulation distortion amount detected by the cross-modulation distortion amount detecting means 2.

【0012】

In the output control of the output control means 3, for example, the intermodulation distortion amount detected by the intermodulation distortion amount detecting means 2 by the comparison means 3a is compared with a predetermined value. As a result, when the detected cross-modulation distortion amount is larger than the predetermined value, the output level lowering means 3b lowers the output level of the wireless transmitter 1.

【0013】

In the wireless transmitter 1, generally, when the output level decreases, the amount of cross-modulation distortion decreases in proportion to the square of the amount of decrease. This reduction in the amount of cross-modulation distortion prevents deterioration of line quality and line disconnection that occur in the adjacent wireless communication system due to the cross-modulation distortion of the own wireless communication system.

【0014】

If the cross-modulation distortion does not fall below a predetermined value due to this decrease in the output level, the output of the wireless transmitter 1 is blocked by the output blocking means 3c. As a result, deterioration of line quality and line disconnection that occur in the adjacent wireless communication system due to cross-modulation distortion are surely prevented.

【0015】

[Example]

Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 2 is a configuration diagram showing a first embodiment of the wireless transmitter output control device of the present invention. In the figure, three modulators 11 to 13, a hybrid 14, an IF band amplifier 15, a frequency converter 16, a variable attenuator 17, and an RF band amplifier 18 are shown as parts constituting the wireless transmitter. Each output from the three modulators 11 to 13 is combined by the hybrid 14, amplified by the IF band amplifier 15, and then frequency-converted by the frequency converter 16 to create an RF signal. This RF signal is output from an antenna (not shown) via the variable attenuator 17 and the RF band amplifier 18. The variable attenuator 17 operates so that the output level of the RF band amplifier 18 is constant. That is, the amount of attenuation of the variable attenuator 17 is controlled by the ALC circuit described later based on the output of the RF band amplifier 18. The RF band amplifier 18 is a microwave band amplifier having a built-in GaAs FET or the like.

【0016】

The output control device includes a directional coupler 19, a cross-modulation distortion detection circuit 21, a determination device 22, and an ALC circuit control unit 23. That is, the output of the RF band amplifier 18 is branched by the directional coupler 19, and the amount of intermodulation distortion contained in the output is detected by the intermodulation distortion detection circuit 21. The detected intermodulation distortion amount is compared with the reference value by the determination device 22, and when the detected intermodulation distortion amount is larger than the reference value, the determination device 22 outputs a switching signal to the ALC circuit control unit 23. To do. When the switching signal is not input, the ALC circuit control unit 23 detects the difference between the output level of the RF band amplifier 18 and the standard level offset, and sends the difference to the variable attenuator 17. On the other hand, when a switching signal is input, instead of this standard level offset, for example, an offset lowered by about 2 dB is used to detect the difference between the output level of the RF band amplifier 18 and the offset lowered by about 2 dB. The difference is sent to the variable attenuator 17. The variable attenuator 17 changes the amount of attenuation in the direction in which the difference sent is reduced. Therefore, when the cross-modulation distortion amount becomes larger than the reference value and a switching signal is generated, the attenuation amount of the variable attenuator 17 increases as compared with the case where the cross-modulation distortion amount is small, which causes the wireless transmitter. The output level is reduced.

【0017】

In a wireless transmitter, in general, when the output level decreases, the amount of intermodulation distortion decreases in proportion to the square of the amount of decrease. Therefore, the decrease in the amount of intermodulation distortion causes the intermodulation distortion of the own wireless communication system. This prevents deterioration of line quality and line disconnection that occur in adjacent wireless communication systems.

【0018】

Next, the cross-modulation distortion detection circuit 21 will be described. The cross-modulation distortion detection circuit 21 is composed of a frequency converter 21a, an oscillator 21b, an IF band amplifier 21c, a low-pass filter 21d, and a detector 21e. Explaining these operations with reference to FIG. 3, first, the RF band signal shown in FIG. 3A is input to the frequency converter 21a. It is assumed that this RF band signal contains cross-modulation distortion that is maximum at frequencies f1 and f2, respectively. The oscillator 21b is set to generate a local oscillation signal of frequency f1, and the local oscillation signal is sent to the frequency converter 21a. Therefore, the RF band signal is frequency-converted by the frequency converter 21a, which is a mixer, to become the IF band signal shown in FIG. 3 (B). The local oscillation signal of frequency f2 may be sent from the oscillator 21b to the frequency converter 21a.

【0019】

This IF band signal is amplified by the IF band amplifier 21c and then passed through a low-pass filter 21d. As a result, only the cross-modulation distortion component shown in FIG. 3 (C) can be obtained. The cross-modulation distortion level is detected by detecting this with the detector 21e.

【0020】

This cross-modulation distortion level is input to the (+) terminal of the judgment device 22 composed of an operational amplifier, and the reference voltage is supplied to the (-) terminal of the judgment device 22. The determination device 22 outputs a switching signal when the cross-modulation distortion level exceeds the reference voltage.

【0021】

The ALC circuit control unit 23 includes a detector 23a, a DC amplifier 23b, an offset generator consisting of resistors R1, R2, and R3, and a changeover switch 23c. In the offset generator, DC power is supplied to both ends of the resistors R1, R2, R3 connected in series, and the standard level offset is sent from the connection point of the resistors R1 and R2 to the changeover switch 23c, and the resistors R2, R3 An offset that is, for example, 2 dB lower than the standard level offset from the connection point of is sent to the changeover switch 23c.

【0022】

The changeover switch 23c is located as shown by the solid line in FIG. 2 while the changeover signal is not input from the determination device 22, and supplies the standard level offset to the (-) terminal of the DC amplifier 23b. On the other hand, when the changeover signal is input from the determination device 22, the changeover switch 23c switches to the position shown by the broken line in FIG. 2 and supplies an offset 2 dB lower than the standard level offset to the (-) terminal of the DC amplifier 23b.

【0023】

The detector 23a detects the output of the RF band amplifier 18 to obtain an output level, and supplies this to the (+) terminal of the DC amplifier 23b. The DC amplifier 23b detects the difference between the output level supplied to the (+) terminal and the offset supplied to the (-) terminal, and sends the difference to the variable attenuator 17.

【0024】

Thus, the DC amplifier 23b detects the difference between the output level of the RF band amplifier 18 and the standard level offset when the switching signal is not input, and sends the difference to the variable attenuator 17. On the other hand, when a switching signal is input, instead of this standard level offset, an offset lowered by about 2 dB is used to detect the difference between the output level of the RF band amplifier 18 and the offset lowered by about 2 dB, and the difference is detected. Send the difference to the variable attenuator 17.

【0025】

In the above embodiment, it is assumed that an offset 2 dB lower than the standard level offset is sent from the connection point of the resistors R2 and R3 to the changeover switch 23c, but if this is lower than the standard level offset, It may be another value.

【0026】

Further, in the above embodiment, when the switching signal is generated, the output level of the wireless transmitter is reduced to reduce the amount of cross-modulation distortion, which causes deterioration of line quality and line in the adjacent wireless communication system. Although the disconnection is prevented, instead of this, the output of the wireless transmitter is cut off when a switching signal is generated due to an increase in the amount of cross-modulation distortion, which causes a line generated in an adjacent wireless communication system. It may be possible to prevent deterioration of quality and line disconnection. Specifically, it is realized by setting the drain voltage of the FETs constituting the RF band amplifier 18 to 0 when the switching signal is generated. Alternatively, the power of the wireless transmitter may be cut off when the switching signal is generated.

【0027】

Next, a second embodiment will be described. FIG. 4 is a configuration diagram showing a second embodiment of the wireless transmitter output control device of the present invention. Since the configuration of the second embodiment is basically the same as the configuration of the first embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted.

【0028】

In the second embodiment, the control unit 25, the maximum attenuation output unit 26, and the changeover switch 27 are newly added. A switching signal is input to the control unit 25 from the determination device 22. When the switching signal is first input from the determination device 22, the control unit 25 transfers the switching signal to the ALC circuit control unit 23 as it is, but when the switching signal is continuously input for a predetermined time, the switching switch Output the switching operation signal to 27. The changeover switch 27 is normally located as shown by a solid line in FIG. 4, but when it receives a changeover operation signal from the control unit 25, it switches to the position shown by a broken line in FIG. The maximum attenuation output unit 26 outputs a level value at which the variable attenuator 17 reaches the maximum attenuation amount.

【0029】

The operation of the second embodiment configured in this way will be described with reference to the timing chart of FIG. When the cross-modulation distortion as shown in FIG. 5 (A) occurs, the switching signal as shown in FIG. 5 (B) is sent from the determination device 22 to the ALC circuit control unit 23 via the control unit 25. The level difference detected by the ALC circuit control unit 23 is sent to the variable attenuator 17 via the changeover switch 27. As a result, if the amount of cross-modulation distortion is lower than the reference value [Fig. 5 (A)], the control unit 25 does not generate a switching operation signal [Fig. 5 (C)], and the changeover switch 27 is shown in solid line in FIG. Maintain the position indicated by. In this case, the operation is the same as that of the first embodiment.

【0030】

If, for some reason, the cross-modulation distortion amount does not drop below the reference value even if the switching signal is generated, FIGS. 5 (D) to 5 (F) show. That is, cross-modulation distortion as shown in FIG. 5 (D) occurs, and a switching signal as shown in FIG. 5 (E) is sent from the determination device 22 to the ALC circuit control unit 23 via the control unit 25. The level difference detected by the ALC circuit control unit 23 is sent to the variable attenuator 17 via the changeover switch 27. As a result, if the amount of cross-modulation distortion does not fall below the reference value [FIG. 5 (D)], the control unit 25 generates a switching operation signal as shown in FIG. 5 (F). Therefore, the changeover switch 27 switches to the position shown by the broken line in FIG. 4, and therefore the output from the maximum attenuation output unit 26 is sent to the variable attenuator 17. As a result, the amount of attenuation of the variable attenuator 17 becomes the maximum amount of attenuation, and the output of the wireless transmitter is effectively cut off.

【0031】

As described above, in the second embodiment, if for some reason the intermodulation distortion amount does not decrease below the reference value even if the switching signal is generated continues for a predetermined time, the output of the wireless transmitter is cut off. Put it in a state. As a result, deterioration of line quality and line disconnection that occur in the adjacent wireless communication system due to the cross-modulation distortion of the own wireless communication system are surely prevented.

【0032】

In the second embodiment described above, when the state in which the cross-modulation distortion amount does not decrease below the reference value continues for a predetermined time even if a switching signal is generated, the attenuation amount of the variable attenuator 17 is set to the maximum attenuation amount. Instead of this, the drain voltage of the FET constituting the RF band amplifier 18 is set to 0 when the state in which the cross-modulation distortion amount does not drop below the reference value continues for a predetermined time even if a switching signal is generated. You may. Alternatively, the power of the wireless transmitter may be cut off.

【0033】

Next, a third embodiment will be described. FIG. 6 is a configuration diagram showing a third embodiment of the wireless transmitter output control device of the present invention. Since the configuration of the third embodiment is the same as that of the first embodiment except for the cross-modulation distortion detection circuit, the same components are designated by the same reference numerals and the description thereof will be omitted. The illustration of the ALC circuit control unit is omitted.

【0034】

In the third embodiment, the intermodulation distortion detection circuit 28 is provided in place of the intermodulation distortion detection circuit 21 of the first embodiment. The intermodulation distortion detection circuit 28 includes a frequency converter 28a, an IF band amplifier 28b, a bandpass filter 28c, and a detector 28d. A local oscillator 29 is connected to the frequency converter 28a. Although not shown in FIG. 2 of the first embodiment, the local oscillator 29 is originally an oscillator that constitutes a wireless transmitter and provides a local oscillation frequency to the frequency converter 16. Was diverted to the cross-modulation distortion detection circuit 28.

【0035】

Explaining these operations with reference to FIG. 7, first, the output of the radio transmitter branched by the directional coupler 19 is input to the frequency converter 28a and converted into the same band as the IF band signal of the radio transmitter. [Fig. 7 (A)]. Here, let f3 be the frequency of the maximum value of the lower intermodulation distortion component in this IF band signal spectrum. The bandpass filter 28c is set with this frequency f3 as a pass band. Therefore, only the cross-modulation distortion component as shown in FIG. 7 (B) is obtained at the output of the bandpass filter 28c. The cross-modulation distortion level is detected by detecting this with the detector 28d. Subsequent operations are the same as in the first embodiment.

【0036】

As described above, in the third embodiment, the local oscillator 29 for the wireless transmitter can be diverted as the local oscillator for the frequency converter 28a. Next, a fourth embodiment will be described.

【0037】

FIG. 8 is a configuration diagram showing a fourth embodiment of the wireless transmitter output control device of the present invention. Since the configuration of the fourth embodiment is the same as the configuration of the third embodiment except for the cross-modulation distortion detection circuit, the same components are designated by the same reference numerals and the description thereof will be omitted, and the same components will be omitted. A part of the illustration is omitted.

【0038】

In the fourth embodiment, the cross-modulation distortion detection circuit 30 is provided in place of the cross-modulation distortion detection circuit 28 of the third embodiment. The intermodulation distortion detection circuit 30 includes a first frequency converter 30a, an IF band amplifier 30b, a second frequency converter 30c, a low-pass filter 30d, a detector 30e, and an oscillator 30f. Again, the local oscillator 29 is connected to the frequency converter 30a.

【0039】

Explaining these operations with reference to FIG. 9, first, the output of the radio transmitter branched by the directional coupler 19 is input to the frequency converter 30a and converted into the same band as the IF band signal of the radio transmitter. [Fig. 9 (A)]. Again, let f3 be the frequency of the maximum value of the lower intermodulation distortion component in this IF band signal spectrum. The oscillator 30f sends the oscillation frequency of frequency f3 to the second frequency converter 30c. Therefore, the output of the second frequency converter 30c is as shown in FIG. 9 (B). By passing this through the low-pass filter 30d, only the cross-modulation distortion component shown in FIG. 9 (C) can be obtained. The cross-modulation distortion level is detected by detecting this with the detector 30e.

【0040】

The cross-modulation distortion detection circuit shown in the third and fourth embodiments may be applied to the second embodiment.

【0041】

[Effect of the invention]

As described above, in the present invention, the amount of intermodulation distortion contained in the output of the wireless transmitter is detected, and the output of the wireless transmitter is controlled based on the detected amount of intermodulation distortion. That is, when the detected cross-modulation distortion amount is larger than a predetermined value, the output level of the wireless transmitter is lowered. Since the amount of cross-modulation distortion decreases as the output level decreases, deterioration of line quality and line disconnection that occur in the adjacent wireless communication system due to the inter-modulation distortion of the own wireless communication system can be prevented.

【0042】

If the cross-modulation distortion does not fall below a predetermined value due to this decrease in output level, the output of the wireless transmitter is cut off. As a result, deterioration of line quality and line disconnection that occur in the adjacent wireless communication system due to cross-modulation distortion are surely prevented.

[Simple explanation of drawings]

[Figure 1]

It is a principle explanatory drawing of this invention.

[Figure 2]

It is a block diagram of the 1st Example.

[Fig. 3]

It is a figure which shows the detection process of a cross modulation distortion.

[Fig. 4]

It is a block diagram of the 2nd Example.

[Fig. 5]

It is an operation timing chart of the 2nd Example.

[Fig. 6]

It is a block diagram of the 3rd Example.

[Fig. 7]

It is a spectrum diagram of each part of a cross modulation distortion detection circuit.

[Fig. 8]

It is a block diagram of the 4th Example.

[Fig. 9]

It is a spectrum diagram of each part of a cross modulation distortion detection circuit.

[Fig. 10]

It is a figure which shows the multi-carrier system.

[Fig. 11]

It is a figure which shows the cross modulation distortion.

[Explanation of symbols]

1 wireless transmitter 2 Intermodulation distortion detection means 3 Output control means 3a Comparison means 3b Output level reduction means 3c Output blocking means