JP4050212B2 - Signal receiving device - Google Patents

Description

The present invention relates to a signal receiving apparatus and a signal receiving method avoidable that the reception level is cause signal degradation by excessive and too far or lowered rise.

  For example, in a microwave radio communication system, a fluctuation in reception input level called fading occurs. As this fading, there are known up-fading in which the received input level is higher than the standard level and attenuating fading in which the received input level is lower than the standard level.

    When up fading occurs, the reception input level becomes excessive, the high frequency amplifier in the receiving apparatus is saturated, and a large distortion occurs. In order to avoid this problem, a conventional microwave radio communication apparatus receiver has employed a technique for increasing the saturation level of the high-frequency amplifier itself, or a technique for inserting a fixed attenuator in front of the high-frequency amplifier. As a technique for attenuating a received microwave signal by a method of inserting a fixed attenuator and preventing a high-frequency amplifier from being saturated even during up-fading, the microwave receiving apparatus described in Patent Document 1 can be cited. In the method of increasing the saturation level of the high-frequency amplifier itself, there are problems such as an increase in the size of the high-frequency amplifier and an increase in power consumption.

JP 2000-315960 A

  FIG. 4 is a diagram showing waveforms for comparing and explaining an operation example of the conventional receiving apparatus using the method of inserting the fixed attenuator and the conventional receiving apparatus not using the fixed attenuator. In a configuration that does not use a fixed attenuator, as shown in waveform A, the high-frequency amplifier is saturated when the reception input level exceeds a saturation level that is higher than a standard reception level by up-fading. When the high frequency amplifier is saturated, the microwave signal cannot be amplified without distortion, and as a result, a signal error occurs.

  When a fixed attenuator is inserted in front of the high frequency amplifier, the signal input to the high frequency amplifier has a waveform B, and saturation of the high frequency amplifier at the time of up fading as described above can be avoided. However, when attenuating fading occurs as shown by the waveform B in FIG. 4, the input level of the high-frequency amplifier is further lowered by the fixed attenuator, so that the S / N is reduced and the error rate is increased. Arise. This problem becomes serious especially when the input level of the high-frequency amplifier is lower than the amplification lower limit level.

  An object of the present invention is to prevent signal degradation caused by an increase in reception level in a signal receiving apparatus used in a microwave radio communication system or the like. Another object is to eliminate signal discontinuity during control.

A signal receiving apparatus according to the present invention includes a duplexer that bifurcates and outputs a received signal received via an antenna, and a first amplifier that amplifies one received signal output from the duplexer. A second receiving circuit comprising: a first receiving circuit; a second amplifier that amplifies the other received signal output from the duplexer; and a variable attenuator connected to a preceding stage of the second amplifier. Selection means for selecting one of the output of the first reception circuit and the output of the second reception circuit, and control means for controlling the selection by the selection means based on the level of the reception signal The first amplifier and the second amplifier have the same characteristics, and the control means, when the output of the first receiving circuit is selected by the selection means, Below the saturation level in the first amplifier When the level of the received signal exceeds the level of 1, the output of the second receiving circuit is selected by the selection means, and then the attenuation amount of the variable attenuator is set to a predetermined attenuation amount, while the second When the output of the receiving circuit is selected by the selecting means, if the level of the received signal falls below a second level that is higher than the amplification lower limit level in the second amplifier, the attenuation amount of the variable attenuator is set to a predetermined amount. After the attenuation amount is set to zero, the output of the first receiving circuit is selected by the selection means.

A signal receiving method according to the present invention includes a duplexer that bifurcates and outputs a received signal received via an antenna, and a first amplifier that amplifies one received signal output from the duplexer. A first receiving circuit, a second amplifier having the same characteristics as the first amplifier, amplifying the other received signal output from the duplexer, and connected to the previous stage of the second amplifier A second receiving circuit comprising a variable attenuator, selecting means for selecting one of the output of the first receiving circuit and the output of the second receiving circuit, and selection by the selecting means A signal receiving method in a signal receiving device comprising a control means for controlling based on the level of the received signal, and when the output of the first receiving circuit is selected by the selection means by the control means, In the first amplifier When the level of the received signal exceeds the first level lower than the saturation level, the output of the second receiving circuit is selected by the selection means, and then the attenuation amount of the variable attenuator is set as a predetermined attenuation amount. When the output of the second receiving circuit is selected by the selecting means and the level of the received signal falls below the second level higher than the amplification lower limit level in the second amplifier, the variable attenuator The attenuation amount is set to zero from a predetermined attenuation amount, and thereafter, the output of the first receiving circuit is selected by the selection means.

  According to the signal receiving apparatus of the present invention, since either one of the output of the first receiving circuit not provided with the attenuator and the output of the second receiving circuit provided with the attenuator can be selected, the second fading is performed at the time of up fading. The output of the first receiving circuit can be selected and dealt with, and the attenuation fading can be selected and dealt with.

  Further, when the output of the first receiving circuit is selected by the selecting means, if the level of the received signal exceeds the first level lower than the saturation level in the first amplifier, the output of the second receiving circuit is By selecting, switching is performed before saturation, and when the output of the second receiving circuit is selected by the selecting means, the second level higher than the amplification lower limit level in the second amplifier is set to the received signal. When the level falls below, by selecting the output of the first receiving circuit, switching can be performed before the amplification lower limit is reached, thereby eliminating signal discontinuity.

  A signal receiving apparatus is realized by adopting a dual system configuration including a first receiving circuit and a second receiving circuit. Hereinafter, a signal receiving apparatus according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows the configuration of the signal receiving apparatus according to the first embodiment. This signal receiving apparatus constitutes a second receiving circuit and an active receiving apparatus 2 that receives a microwave via an antenna 1 and constitutes a first receiving circuit for a received signal via a duplexer 7. A configuration is adopted in which the standby receiving device 3 is branched and given. Either one of the output of the active receiving device 2 and the output of the standby receiving device 3 is selected by the switch 8 and sent to a circuit that performs the next processing of the signal.

  The active receiving device 2 includes a high-frequency amplifier 21 that is a first amplifier, and a level detector 6 that converts a signal on the input side of the high-frequency amplifier 21 into an input level. The high frequency amplifier 21 amplifies the input received signal and sends the output to the switch 8. The output of the level detector 6 is sent to the control circuit 9.

  The standby reception apparatus 3 includes a high-frequency amplifier 31 that is a second amplifier, and a variable attenuator 5 that is connected to the previous stage of the high-frequency amplifier 31. The high frequency amplifier 31 amplifies the received signal (the signal that has passed through the variable attenuator 5) and sends the output to the switch 8, and has the same characteristics as the high frequency amplifier 21. The variable attenuator 5 controls the amount of attenuation by a control signal Sb given from the control circuit 9. When the variable attenuator 5 is set to a predetermined amount of attenuation, the received signal at the time of the maximum predicted up fading is set. Is lowered from the saturation level in the high frequency amplifier 31 and supplied to the high frequency amplifier 31.

  The control circuit 9 receives a signal SL corresponding to the level of the received signal transmitted from the level detector 6, compares the signal SL with the first level V1 and the second level V2, and compares the signal SL with the variable attenuator 5 and the switch. 8 is controlled. FIG. 2 shows the relationship between the first level V1, the second level V2, the saturation level VSA in the high frequency amplifier 21 (high frequency amplifier 31), and the amplification lower limit level VLOW in the high frequency amplifier 21 (high frequency amplifier 31). The first level V1 is lower than the saturation level VSA in the high frequency amplifier 21 (high frequency amplifier 31), and the second level V2 is higher than the amplification lower limit level VLOW in the high frequency amplifier 21 (high frequency amplifier 31). That is, VSA> V1> V2> VLOW.

  Then, when the level SL of the received signal exceeds the first level V1, the control circuit 9 controls the switch 8 with the control signal Sa to select the output of the standby receiver 3 (high frequency amplifier 31), Next, the variable attenuator 5 is controlled by the control signal Sb so that the variable attenuator 5 has a predetermined attenuation. This predetermined attenuation is an attenuation that can prevent the saturation level VSA in the high-frequency amplifier 21 (high-frequency amplifier 31) from exceeding the up-fading in the received signal. When the received signal level SL falls below the second level V2 higher than the amplification lower limit level VLOW, the control circuit 9 controls the variable attenuator 5 with the control signal Sb to set the attenuation amount of the variable attenuator 5 to zero. Next, the switch 8 is controlled by the control signal Sa to select the output of the active receiver 2 (high frequency amplifier 21). When the attenuation amount of the variable attenuator 5 is zero, a high frequency amplifier 21 (high frequency amplifier 31) is used that does not fall below the amplification lower limit level VLOW even if attenuating fading occurs in the received signal.

  Since the signal receiving apparatus configured as described above operates in accordance with the flowchart shown in FIG. 3 as follows, this will be described. Initially, the control circuit 9 selects the output of the active receiver 2 by controlling the switch 8 (S1). At this time, the attenuation amount of the variable attenuator 5 is zero. When the output of the active receiver 2 is selected, the control circuit 9 detects whether or not the level SL of the received signal transmitted from the level detector 6 exceeds the first level V1 (S2). .

  As a result of the determination in step S2, when the level SL of the received signal exceeds the first level V1, the control circuit 9 controls the switch 8 with the control signal Sa to output the output of the standby receiver 3 (high frequency amplifier 31). Next, the variable attenuator 5 is controlled by the control signal Sb so that the variable attenuator 5 has a predetermined attenuation (S4). Thus, when the level SL of the received signal exceeds the first level V1, when the switching is performed by the switch 8, the amount of attenuation of the variable attenuator 5 is zero. The obtained signal is the same as before switching, and if instantaneous interruption due to switching is excluded, signal output continues as if a continuous (or the same) signal is output. After that, the variable attenuator 5 is controlled to set the attenuation amount of the variable attenuator 5 to a predetermined value, so that the received signal is gradually attenuated and the signal obtained via the switch 8 is continuously changed. Therefore, a discontinuous signal that jumps between two signals is not output by switching, so that stable signal processing is possible. Further, since the variable attenuator 5 has a predetermined attenuation, it is possible to prevent the level of the signal arriving at the high frequency amplifier 21 from exceeding the saturation level.

  As described above, when the output of the standby receiving apparatus 3 is selected, the control circuit 9 detects whether or not the level SL of the received signal sent from the level detector 6 has fallen below the second level V2. (S5). When it is detected in step S5 that the received signal level SL is lower than the second level V2, the control circuit 9 uses the control signal Sb to reduce the attenuation amount of the variable attenuator 5 to zero. Thus, the variable attenuator 5 is controlled (S6), and then, the switch 8 is controlled by the control signal Sa to select the output of the active receiver 2 (high frequency amplifier 21) (S7).

  As described above, when the level SL of the received signal falls below the second level V2, the attenuation amount of the variable attenuator 5 is first made zero, so that the attenuation amount of the variable attenuator 5 is zero. When this happens, the output of the standby receiving device 3 selected by the switch 8 has the same signal waveform as the output of the active receiving device 2 not selected by the switch 8, and then when switching is performed by the switch 8. The signal obtained via the switch 8 is the same as before the switching, and if the instantaneous interruption due to the switching is excluded, the signal output is continued as if a continuous (or the same) signal is output. In this way, even when switching is performed when the level SL of the received signal falls below the second level V2, a discontinuous signal that jumps between the two signals is not output and is stable. Signal processing becomes possible. Further, by selecting the active receiver 2 that does not have the variable attenuator 5 after switching, the input level of the high-frequency amplifier is further lowered when attenuating fading occurs, and the S / N is reduced. The problem that the error rate increases can be avoided.

  Stable signal by switching between active and standby receivers that receive the same received signal and controlling the attenuation of the variable attenuator provided in the standby receiver before or after switching A signal receiving circuit capable of processing can be realized.

The block diagram which shows the Example of the signal receiver which concerns on this invention. The figure which shows the relationship between the level which concerns on the characteristic in the high frequency amplifier of the signal receiver which concerns on this invention, and the level which a control circuit controls. The flowchart for demonstrating operation | movement of the signal receiver which concerns on this invention. The figure which shows the signal waveform change for demonstrating operation | movement of the signal receiver which concerns on a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Active system receiver 3 Standby system receiver 5 Variable attenuator 6 Level detector 7 Divider 8 Switch 9 Control circuit 21 High frequency amplifier 31 High frequency amplifier

Claims (2)

A duplexer that bifurcates and outputs the received signal received via the antenna;
A first receiving circuit comprising a first amplifier for amplifying one received signal output from the duplexer;
A second receiving circuit comprising: a second amplifier that amplifies the other received signal output from the duplexer; and a variable attenuator connected to a preceding stage of the second amplifier;
Selecting means for selecting one of the output of the first receiving circuit and the output of the second receiving circuit;
Control means for controlling the selection by the selection means based on the level of the received signal,
The first amplifier and the second amplifier have the same characteristics;
The control means, when the output of the first receiving circuit is selected by the selection means, when the level of the received signal exceeds a first level lower than a saturation level in the first amplifier, The output of the second receiving circuit is selected by the selecting means, and then the attenuation of the variable attenuator is set to a predetermined attenuation, while the output of the second receiving circuit is selected by the selecting means In addition, when the level of the received signal falls below a second level higher than the amplification lower limit level in the second amplifier, the attenuation amount of the variable attenuator is reduced from a predetermined attenuation amount to zero, and then the first receiving circuit. Is selected by the selection means. A duplexer that bifurcates and outputs the received signal received via the antenna;
A first receiving circuit comprising a first amplifier for amplifying one received signal output from the duplexer;
A second amplifier having the same characteristics as the first amplifier and amplifying the other received signal output from the duplexer; and a variable attenuator connected to a preceding stage of the second amplifier. A second receiving circuit;
Selecting means for selecting one of the output of the first receiving circuit and the output of the second receiving circuit;
A signal receiving method in a signal receiving device comprising: control means for controlling selection by the selection means based on a level of the received signal;
By the control means,
When the output of the first receiving circuit is selected by the selection means, if the level of the received signal exceeds the first level lower than the saturation level in the first amplifier, the second receiving circuit The output is selected by the selecting means,
After that, while making the attenuation amount of the variable attenuator a predetermined attenuation amount,
When the output of the second receiving circuit is selected by the selection means, if the level of the received signal falls below a second level higher than the amplification lower limit level in the second amplifier, the attenuation of the variable attenuator The amount is reduced from the predetermined attenuation to zero,
Then, the signal receiving method is characterized in that the selection means selects the output of the first receiving circuit.

Images