JPH04341027A - Radio receiver for multi-carrier signal - Google Patents

Abstract

PURPOSE:To prevent an error rate from being deteriorated due to cross modulation distortion caused with a carrier of other low incoming call level when an incoming call level of a specific carrier in a multi-carrier signal is high extremely. CONSTITUTION:A comparator circuit 16b compares a threshold equivalent to a predetermined standard incoming call level to suppress cross modulation distortion within a prescribed reference value with a maximum level being an output of an OR circuit 23 and feeds back the difference to a variable attenuator 2. The maximum level of the output of the OR circuit 23 as a result, that is, a maximum incoming call level of the carrier in the received multi-carrier is higher than the threshold level, that is, the standard incoming call level, then the level of the carrier is decreased to the standard incoming call level and the level of other carrier is decreased in a same rate. Thus, the IF signal of the multi-carrier is sent to a branch device 6, in which the signal is branched into three and each carrier is extracted by band pass filters 7-9. Each extracted carrier is given to AGC amplifiers 10-12, in which the gain of the low level signal is increased and the result is given to demodulators 13-15, in which the signal is demodulated into a base band signal.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a wireless communication system that transmits digital signals using a multicarrier method in order to improve fading resistance, and particularly when the arrival level of a particular carrier in a multicarrier signal is unbalanced. The present invention relates to a radio receiving apparatus equipped with a gain control means for preventing high incoming signal levels from degrading the error rate due to cross-modulation distortion occurring between carriers with other low incoming signal levels.

[0002] In recent years, the gain control (AGC) method for countering high incoming signal levels in multi-carrier systems has been developed for multi-carrier signals (for example, 110, 130, and 150 MH).
The system detects all incoming power and attenuates the level by controlling the variable attenuator using AGC until the total power reaches the standard incoming power level.

[0003] Therefore, multipath fading (up
In the case of fading) or rain attenuation, differences in amplitude occur between each wave of a multicarrier. For example, the incoming level of one wave is extremely high, but the level of each other wave is low, and the total power is below the standard level. If it is lower than the incoming call level, the AGC
level control is not applied. Therefore, one wave with a high level of incoming signal passes through the amplifier in the receiving board with that level intact, and the error rate deteriorates significantly due to cross-modulation distortion due to the nonlinear characteristics of the amplifier.

[0004] Therefore, as a countermeasure for high incoming call levels, A method that can always obtain high communication quality without deteriorating cross-modulation distortion is proposed.
There is a strong demand for a wireless receiving device equipped with GC control means.

[0005]

2. Description of the Related Art FIG. 7 shows the configuration of a conventional radio receiving apparatus that receives multicarrier signals independently in a non-space diversity system. Multicarrier is 110,
It is assumed that it is composed of three waves of 130 and 150 MHz.

In FIG. 7, 1 and 3 are low-noise amplifiers for RF signals, 2 is a variable attenuator, 4 is a frequency converter (MIX) that converts the RF signal into an IF signal, 5 is an AGC control circuit, and 6 is a Turnout composed of hybrid circuit, 7~
9 is a bandpass filter (BPF) that separates the three carrier waves that make up the multicarrier, 10 to 12 are AGC amplifiers that raise the signal level below the reference level to improve the S/N, and 13 to 15 are demodulators (DEM). , 48 is a detector that detects the power level of the multicarriers by averaging each carrier, and 50 is a comparison circuit using an OP amplifier that compares the average level of the detected multicarriers with a standard incoming signal level.

[0007] Three waves of multicarrier RF signals inputted from an antenna are frequency-converted into an IF signal by a frequency converter 4 . Regarding this IF signal, the average level of all carriers is detected by the detector 48 of the AGC control circuit 5. Further, the comparison circuit 50 compares the detected average level with a threshold value corresponding to the standard incoming call level, and controls the variable attenuator 2 with the difference output, so that the IF signal level in the figure becomes equal to the standard incoming call level. Adjust to

The AGC-controlled IF signal is branched into three carriers by the branching device 6, and further AGC-controlled.
Amplifiers 10 to 12 raise the signal level of the carrier below the reference level, and demodulators 13 to 15 demodulate the signal. Next, Figure 8
In the space diversity method, the main (MAIN)
) and auxiliary (SD) systems of multicarrier signals.

In FIG. 8, reference numbers 1 to 4, 24, 4
The elements indicated by 8 correspond to the elements with the same numbers in FIG. 7, but include elements of the MAIN system and elements common to both the MAIN and SD systems. Also 1' to 4',
Elements 24' and 48' belong to the SD received signal system and correspond to elements 1 to 4, 24, and 48 of MAIN, respectively.

On the other hand, new elements 24 and 24' are branchers that branch the MAIN and SD IF multicarrier signals into three, and 25 to 27 are branchers that branch the SD IF signals branched by the brancher 24'. infinite phase shifter,
28 to 30 are the 3 output signals of the splitter 24 and the infinite phase shifter 25
A multiplexer that combines the three output signals of ~27 on a one-to-one basis, 49
is an OR circuit which takes out the larger signal level of the outputs of the wave detector 48 and the wave detector 48'.

The MAIN and SD RF signals received by the main and sub antennas pass through variable attenuators 2 and 2', respectively, and are converted into IF signals by frequency converters 4 and 4'. Each IF signal is branched to the AGC control circuit 5 and detected by detectors 48, 48' to generate DC signals corresponding to the average power of each IF signal. The higher level of these DC signals is input from the OR circuit 49 to the comparison circuit 50 .

The comparator circuit 50 compares the level of the input DC signal with a preset threshold value corresponding to a standard incoming call level, and if the input DC level exceeds the threshold level, the MAIN signal is output. The attenuation amounts of the variable attenuators 2 and 2' of both SD systems are simultaneously increased, and the average level of the received signal of the one with high incoming calls is reduced to the standard incoming signal level, and the level of the other received signal is also increased at the same rate. lower.

In this way, the IF signals of both the MAIN and SD systems, whose high incoming signal levels have been suppressed, are divided into three by branchers 24 and 24', respectively, and the signals of the SD system are further divided into three by an infinite phase shifter. 25 to 27 receive a phase shift to compensate for fading fluctuations, and multiplexers 28 to 30
The signals from both systems are combined.

Since the configurations of the circuits subsequent to the multiplexers 28 to 30 are the same, only the circuits after the multiplexer 28 will be described. The combined output of the multiplexer 28 is branched into three parts by the splitter 6, and each branch output is divided into three parts by the bandpass filters 7 to 9.
Two different carrier signal components are extracted. The three extracted carrier signals are sent to AGC amplifiers 10 to 1, respectively.
2, signal levels below the reference level are adjusted to raise them to the reference level, and demodulated into baseband signals by demodulators 13 to 15, respectively. Infinite phase shifter 25~
27, the amount of phase shift is controlled by a fading compensation circuit (not shown) so that each carrier signal is at its optimum level.

[0015]

[Problems to be Solved by the Invention] The conventional control system using AGC to counter high incoming call levels has the following two problems. ■． Under normal operating conditions, differences in incoming signal levels often occur between each wave (carrier) of a multicarrier due to multipath fading (particularly up fade) or rain attenuation. At this time, for example, if the incoming signal level of one wave is extremely high, the levels of the other two waves are low, and the total power of the three waves is lower than the standard incoming signal level, AGC control may not be applied. Therefore, a single wave with a high incoming level passes through the receiving board at this level, resulting in greater deterioration due to third-order and fifth-order cross-modulation distortion, resulting in a higher error rate.

[0016]■. On the other hand, if the incoming signal level of one wave is extremely low, but the level of the other two waves is high, and the total power of the three waves is higher than the standard incoming signal level, the combined level of the three waves will be set to the standard incoming signal level by AGC control. can be lowered to As a result, the distortion of the two high-level waves is improved, but the level of the remaining one wave with a low incoming level is further lowered, so the S/
N deteriorates, the error rate increases, and the quality of the line deteriorates. An object of the present invention is to provide a radio receiving device equipped with means for dealing with a high incoming signal level that does not worsen the error rate when the incoming signal level of one wave in a multicarrier is particularly high or low compared to other waves. It is an object.

[0017]

[Means for Solving the Problems] The present invention provides AGC at the average level of the incoming level of each carrier when there is a significant difference between the incoming level of one carrier and the incoming level of other carriers in a multicarrier. Rather than controlling
AGC control is performed based on the maximum level of the incoming call level of each carrier, and the incoming call level of each carrier is suppressed to below the standard incoming call level.

FIGS. 1 and 2 are diagrams showing the basic configuration of the present invention, with FIG. 1 illustrating the configuration of each radio receiving device in the case of the single reception method and FIG. 2 illustrating the configuration of each radio receiving device in the case of the space diversity method. be. Note that multicarrier is 110 MHz,
It is assumed that it is composed of three carrier waves of 130 MHz and 150 MHz.

First, the configuration of the single reception method shown in FIG. 1 will be explained. 1 and 3 are low noise amplifiers, 2 is a variable attenuator, 4 is a frequency converter, 5 is an AGC control circuit, 6 is a splitter, 7 to 9 are bandpass filters that extract each carrier in a multicarrier, 10 to 12 is an AGC (variable gain) amplifier,
13 to 15 are demodulators, 16a is a level detection circuit, 16b
is a comparison circuit, 17 to 19 are bandpass filters that extract each carrier in the multicarrier, 20 to 22 are detectors, and 23
is an OR circuit that detects the maximum level.

The basic operation of the circuit shown in FIG. 1 except for AGC control is the same as that of the conventional example shown in FIG. The level is adjusted by an attenuator 2, further amplified by a low noise amplifier 3, and converted into an IF signal by a frequency converter 4. The converted multi-carrier IF signal is
Next, the branch 6 and the level detection circuit 16 of the AGC control circuit 5
input to a.

The multi-carrier IF signal input to the level detection circuit 16a is filtered by three carriers (110 MHz, 130 MHz,
150 MHz), each with a detector 20~
22, and converted into a DC signal corresponding to the signal level of each carrier. The OR circuit 23 compares the maximum level of the DC signal levels of each detector output with the comparison circuit 16.
input to b.

The comparison circuit 16b compares the maximum level of the output of the OR circuit 23 with a threshold value corresponding to a predetermined standard incoming signal level for suppressing cross-modulation distortion within a certain reference value, and calculates the difference. and feeds back to the variable attenuator 2. As a result, when the maximum level of the output of the OR circuit 23, that is, the maximum incoming level of a carrier in the received multicarrier, is larger than the threshold, that is, the standard incoming level, the level of that carrier is lowered to the standard incoming level, and the level of that carrier is lowered to the standard incoming level, and It also lowers the level of other carriers.

The multi-carrier IF signal whose incoming signal level has been suppressed below the standard incoming signal level in this way is sent to a splitter 6 where it is split into three parts, and individual carriers are extracted by bandpass filters 7 to 9. Ru. Each extracted carrier is demodulated into a baseband signal by demodulators 13 to 15 after increasing the gain of the low level signal in AGC amplifiers 10 to 12.

Next, the configuration of the space diversity system shown in FIG. 2 will be explained. In the configuration of FIG. 2, in the AGC control circuit 5 of the conventional configuration shown in FIG. This is replaced by the circuit 16b, and the other configurations are the same, so the explanation will be omitted. Here, MA in Figure 2
IN system and SD system level detection circuits 16a, 16a'
is the same as the level detection circuit 16a in FIG. 1, and the respective circuit elements 17-23 and 17'-23' correspond to each other.

The level detection circuit 16a detects the received MA
The level detection circuit 16a' detects the incoming level of each carrier in the multi-carrier signal of the IN system, and on the other hand, the level detection circuit 16a' detects the incoming level of each carrier in the received multi-carrier signal of the SD system, and detects the incoming level of each carrier in the received multi-carrier signal of the SD system, and The signal is output to the OR circuit 23 in each of the level detection circuits 16a and 16a'.
, 23'.

Since the outputs of the two OR circuits 23 and 23' are wired OR-connected, the carrier with the highest incoming level among all the carriers detected in each of the two level detection circuits 16a and 16a' is Only the DC signal corresponding to the level is input to the comparator circuit 16b.

The comparison circuit 16b compares the level of the input DC signal with a threshold value corresponding to the standard incoming signal level, feeds back the difference to the MAIN and SD variable attenuators 2, 2', and determines the maximum incoming signal level. Adjust the attenuation amount so that it is at the standard incoming call level. In this way MAIN and SD
The levels of the received signals of both systems are simultaneously controlled based on the carrier having one common maximum incoming level, and are suppressed so as not to exceed the standard incoming level.

[0028]

[Operation] The operation of the present invention will be explained in comparison with the conventional example using FIGS. 3(a) to 3(d). The waveform on the left side of the diagram is AGC
The multicarrier received signal before control, the waveform on the right side of the figure is A
It is an example of a multicarrier received signal after GC control.

FIGS. 3(a) and 3(b) show the difference between the conventional example in the case of a single reception system and the incoming level control of the multicarrier received signal of the present invention, and (a) in FIG. ), the standard incoming call level is multi-carrier 3.
Since the incoming call level of one wave is higher than the standard incoming call level, if the three-wave average is equal to the standard incoming call level, level suppression by AGC control will not work, so it will not exceed the standard incoming call level. The carrier level is output as is.

On the other hand, in the case of the present invention shown in FIG. 3(b), the standard incoming signal level is compared with the maximum value of the incoming signal level for each carrier, and the A of the entire multicarrier received signal is calculated.
Since GC control is performed, the incoming call level of any carrier is controlled so as not to exceed the standard incoming call level.

FIGS. 3(c) and 3(d) show the difference between the conventional example and the incoming signal level control of the present invention in the case of a space diversity reception method. In the conventional example shown in FIG. 3(c), , AGC control does not work because the three-wave average of both MAIN and SD systems does not exceed the standard incoming call level.
The carrier level exceeding the standard incoming call level is output as is.

On the other hand, in FIG. 3(d), MAIN
Since the level of one of the three carrier waves exceeds the standard arrival level, the level of each MAIN and SD multicarrier received signal is suppressed, and the carrier exceeding the standard arrival level is not output.

According to the present invention, as a result of attenuating carriers exceeding the standard incoming level to below the standard incoming level,
Carriers with a level much lower than the standard incoming signal level are also attenuated in the same way, worsening the S/N ratio, but such low-level carriers are
It can be amplified in an amplifier to raise its level to a reference level. Figure 4 shows the level control algorithm in that case.

[0034]

Embodiment FIG. 5 shows the configuration of one embodiment of the present invention. This embodiment has a mechanism to attenuate the standard incoming call level, but
Furthermore, when carriers below the reference level that deteriorate the S/N occur, a mechanism is additionally provided to reduce attenuation so that the lowest level in each wave of the multicarrier becomes equal to or higher than the reference level. For convenience, the configuration of the embodiment corresponding to the single reception method shown in FIG. 1 is shown, but as can be easily guessed, the embodiment can be similarly configured for the case of the space diversity method shown in FIG. 2.

In FIG. 5, the variable attenuator 2a corresponds to the variable attenuator 2 in FIG. 1, but unlike the case in FIG. 1, the input to the level detection circuit 16a is from the output side of the variable attenuator 2a. It is taken. Further, a variable attenuator 2b is provided in series with the variable attenuator 2a, and is used to prevent the lowest level carrier from falling below a reference level.

In FIG. 5, circuit elements 31 to 41 are for controlling the lowest level of this carrier, and 31 to 33 are for controlling each carrier in the multicarrier received signal output from the low noise amplifier 3. 34 to 36 are detectors that detect the level of the carrier,
37 to 39 are inverting amplifiers that invert the polarity of the level of each carrier and provide an offset; 40 are inverting amplifiers 37 to 39;
41 is a comparator that compares the lowest level with a reference level and controls the attenuation amount of the variable attenuator 2b based on the difference output; 42 is an OR circuit, 43 is a comparator 4
1 is a reference voltage circuit that provides a limit level for prohibiting attenuation control below a reference level.

With the configuration of the embodiment shown in FIG. 5, the basic operation is to attenuate the maximum carrier level of the multicarrier received signal so that it does not exceed the standard incoming level, which increases distortion, and furthermore, the minimum level is set to S/N. When the attenuation is below the reference level, which deteriorates the attenuation, an operation can be obtained to suppress the attenuation below the reference level.

FIG. 6 shows an embodiment in which the AGC control function of FIG. 5 is replaced with an MPU, and 44 in the figure is the detector 20-2.
A/2 converts each output DC signal into a digital signal.
D converter, 45 is an MPU that detects the maximum level and minimum level and generates an AGC control signal that can obtain the optimum carrier signal level, 46 is a ROM in which control programs and conversion tables are stored, 47 is an MPU output This is a D/A converter that converts signals into analog signals.

The configuration of the embodiment shown in FIG. 6 makes it possible to reduce the amount of hardware and the mounting space.

[0040]

According to the present invention, even if a level difference occurs between carriers in a multicarrier received signal due to fading or rain attenuation, AGC control can be performed to optimize distortion, and furthermore, S/ AGC control that takes N into consideration is also possible, and a wireless receiving device equipped with an effective AGC control method when receiving a high number of calls can be realized.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic configuration of the present invention using a single reception method.

FIG. 2 is a diagram showing the basic configuration of the present invention using a space diversity method.

FIG. 3 is an explanatory diagram of the operation of the present invention.

FIG. 4 is an explanatory diagram of an algorithm for multicarrier signal level control according to the present invention.

FIG. 5 is a configuration diagram of an embodiment of the present invention using a single reception method.

FIG. 6 is a configuration diagram of an embodiment of the present invention using an MPU.

FIG. 7 is a configuration diagram of a conventional device using a single reception method.

FIG. 8 is a configuration diagram of a conventional device using a space diversity method.

[Explanation of symbols]

1,3 Low noise amplifier 2 Variable attenuator 4 Frequency converter 5 AGC control circuit 16a Level detection circuit 16b Comparison circuit 17-19 Bandpass filter 20~22 Detector 23 OR circuit

Claims (2)

[Claims] Claim 1: A single system multi-carrier signal radio reception device comprising: a variable attenuator (2) for adjusting the level of the received multi-carrier signal; and a level of each carrier in the received multi-carrier signal. When the maximum level of the levels of each carrier detected by the level detection circuit (16a) and the level detection circuit (16a) is greater than a predetermined standard reception level, the The variable attenuator (2
) A comparison circuit (16b) for controlling the gain of a single system multi-carrier signal radio receiving apparatus. [Claim 2] In a wireless receiving device for multiple systems of multicarrier signals using a space diversity method,
A variable attenuator (2, 2') that adjusts the level of the multicarrier signal received for each of the multiple systems, and a variable attenuator (2, 2') that adjusts the level of the individual carrier in the multicarrier signal received for each of the multiple systems. A level detection circuit (16a, 16a') that detects the maximum level of each system, and a level detection circuit (16a, 16a') that is common to each of the multiple systems.
), identify the maximum level among them, and when it is greater than a predetermined standard reception level, make the maximum level equal to the standard reception level. Comparison circuit (16) that simultaneously controls the gain of variable attenuator (2, 2') of each system
A wireless receiving device for multi-carrier signals of multiple systems, characterized by comprising the following.