JP2000068870A - Receiver preventing intermodulation and reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver that effectively prevents deterioration in reception quality due to intermodulation. SOLUTION: The receiver is provided with a communication reception section 3 that has a variable attenuator 16 to receive a required channel and to attenuate a reception level, a monitoring reception section 4 that detects a reception level of a channel of a disturbing wave, and a control means 5 that controls an attenuation quantity of a variable attenuator of the communication reception section 3 based on the detection result of the monitoring reception section. The monitoring reception section detects reception levels of plural disturbing waves generating intermodulation waves to provide interference on the required channel, the control means calculates a reception level of the intermodulation wave from the reception level of the disturbing wave so as to control the attenuation quantity of the variable attenuator so that the reception level of the intermodulation wave shared in the reception level of the required channel becomes a threshold level or below. Thus, the intermodulation wave included in the reception channel is properly suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus such as a mobile phone or a commercial MCA radio apparatus, and a receiving method thereof, and more particularly to suppressing intermodulation (IM).

[0002]

2. Description of the Related Art When a plurality of signals are input to a receiving apparatus, the frequencies of the signals are mixed to generate a signal having a frequency different from the input signal. This is called an intermodulation wave.

The frequency f of the intermodulation wave is f = | m × f ₁ ± n × f ₂ | (m, n: positive integer), where f ₁ and f ₂ are the frequencies of the input signal. m + n is called the order of the intermodulation wave.

In a system in which a plurality of channels are used for transmission and reception in the same area, the frequency of a required reception channel and the frequency of an intermodulation wave caused by a plurality of interfering waves match or are close to each other. Is higher to some extent, interference occurs and the receiving performance on the receiving channel decreases.

Since the level of the intermodulation wave is higher as the order is lower, the order is 3 (m = 2, n = 1 or n = 2, m = 1).
This is a problem in the case of

In order to avoid interference due to intermodulation,
One method is to set the channel arrangement so that the frequency of the intermodulation wave does not match the frequency of the channel. However, in this case, the number of usable channels decreases, and a wide frequency band is required.

Therefore, in a conventional receiving apparatus, in order to suppress the interference due to the intermodulation (IM), the gain in the high frequency stage before the sufficient band limitation is performed is suppressed as much as possible.

[0008] JP-A-9-205332 discloses IM
A conventional receiver for improving the above is disclosed. As shown in FIG. 8, the receiving section of this device uses a low noise amplifier (LNA) 23 capable of varying the amplification gain to receive a received signal (RF-I
N) RF front-end unit 22 for amplifying 21; and local oscillator for oscillating an oscillation signal for determining a reception channel
25, a down converter 24 for mixing a signal oscillated from the local oscillator 25 to convert the frequency of the received signal to an intermediate frequency (IF), a filter for extracting an IF signal, an AGC amplifier, a filter and an amplifier, I
An IF-AGC unit 26 for variably amplifying the F signal, a demodulator 27 for detecting the IF signal, and converting the output of the demodulator 27 into a digital signal to receive an RSSI (received sig) representing the strength of the received signal.
A / D converter 28 that outputs the signal as a nal strength indicator) and the IF-AGC unit 2 based on the input RSSI.
6, a gain adjustment forming unit 29 for controlling the amplification gain of the LNA 23 based on the input RSSI, and an RSSI output from the gain adjustment forming units 29 and 30 as an analog signal. D / A converter 3 for conversion
1 and 32, and an RSSI-TH-CONTROL 33 for controlling thresholds (RSSI-TH1, RSSI-TH2) for specifying the RSSI control range of the gain adjustment forming units 29 and 30.

In this device, the input received signal 21 is L
Amplified by NA23, mixed with local signal oscillated by local oscillator 25 by downconverter 24,
It is converted to an intermediate frequency (IF) signal. The IF signal is band-limited by a filter of an IF-AGC unit 26, and is amplified by an AGC amplifier and an amplifier.
And is detected as RSSI. This RSSI
Is converted into a digital signal by the A / D converter 28, and then input to the gain adjustment forming unit 29 and the gain adjustment forming unit 30.

The gain adjustment forming section 29 controls the amplification gain of the IF-AGC section 26 according to the input RSSI, and the gain adjustment forming section 30 controls the amplification gain of the LNA 23 according to the input RSSI. At this time, the gain adjustment forming unit 30 sets the amplification gain of the LNA 23 lower than the amplification gain of the IF-AGC unit 26 controlled by the gain adjustment forming unit 29.

As described above, by suppressing the gain at the high frequency stage before the band limitation is performed, the reception level of the interfering wave can be suppressed, and the level of the IM that causes interference generated in the reception unit can be suppressed. Can be.

[0012]

However, in the conventional receiver, the sum of the reception level of the required channel and the reception level of the intermodulation wave due to the interfering channel is detected as the RSSI level. Can not know. For this reason, there is a problem in that appropriate reception level control cannot be performed, and it is necessary to limit the number of channels used and the effective use area in order to avoid interference due to intermodulation.

[0013] Further, the receiving apparatus of the intermittent transmission / reception system performs IM reception during a transmission suspension period during communication, predicts the reception level at the next reception from the RSSI, and determines the amount of attenuation. However, this method has a problem that it cannot cope with a sudden change in the reception level due to a time delay.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to provide a receiving apparatus capable of effectively preventing reception quality from deteriorating due to intermodulation, and to provide a receiving method therefor. The purpose is.

[0015]

Therefore, according to the present invention, a monitoring receiver for detecting a reception level of a channel of an interference wave is provided separately from a communication receiver for receiving a required channel. Then, the reception levels of a plurality of interfering waves that generate intermodulation waves that interfere with the required channel are detected, the reception level of the intermodulation wave is calculated from the detected data, and the reception of the intermodulation wave in the reception level of the required channel is detected. The reception level of the required channel is attenuated so that the level becomes equal to or less than the threshold.

Therefore, the intermodulation wave included in the reception level of the reception channel is accurately and continuously suppressed.
It is possible to improve reception quality.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 of the present invention is a receiving apparatus for a transmission / reception system in which transmission / reception is performed using a plurality of channels, for receiving a required channel and attenuating a reception level. A communication receiver including a variable attenuator, a monitoring receiver for detecting a reception level of a channel of an interference wave, and an attenuation amount of the variable attenuator of the communication receiver based on a detection result of the monitoring receiver. Control means for controlling, a monitoring receiver detects reception levels of a plurality of interfering waves that generate intermodulation waves interfering with a required channel, and the controlling means detects the interfering waves detected by the monitoring receiver. The reception level of the intermodulation wave is calculated from the reception level of the variable attenuator, and the attenuation of the variable attenuator is controlled such that the reception level of the intermodulation wave in the reception level of the required channel is equal to or less than the threshold. Are those were, it is possible to accurately suppress the intermodulation wave contained in the received channel.

According to a second aspect of the present invention, the monitoring receiver periodically scans a plurality of channels of the interfering wave to detect the reception level of the interfering wave, and the control means receives the signal and performs variable attenuation. The attenuation level of the modulator is controlled continuously, and the reception level is adjusted according to the constantly changing intermodulation level while continuing to receive on the required channel.
The intermodulation level can be suppressed.

According to a third aspect of the present invention, there is provided a reception method in a transmission / reception system in which transmission / reception is performed using a plurality of channels, wherein a reception level of a required reception channel is detected and interference occurs with the required reception channel. Detect the reception levels of a plurality of interfering waves that generate intermodulation waves, determine the reception level of the intermodulation waves from the reception levels of the detected interference waves, and obtain the reception level of the intermodulation waves in the reception level of the required reception channel. , So that the reception level of the required reception channel is attenuated so that the threshold value becomes equal to or less than the threshold value, and the intermodulation level can be appropriately suppressed.

According to a fourth aspect of the present invention, the SNR of the demodulated output when the reception level of the required reception channel is attenuated is calculated, and the attenuation is executed only when the SNR exceeds a threshold value. And an appropriate SNR can be maintained.

According to a fifth aspect of the present invention, when the receiving channel A and the receiving channel D are at positions that are inverted with respect to the channels B and C of two interfering waves on the frequency axis,
The detection result of the reception levels of the interference waves B and C obtained for calculating the attenuation level of the reception level of the reception channel A is also used when calculating the attenuation level of the reception level of the reception channel D. Thus, the amount of attenuation in the channel located at the position of the image channel with respect to the interference wave can be quickly obtained.

According to a sixth aspect of the present invention, the receiving channel A and the receiving channel D are located at positions that are inverted with respect to the channels B and C of the two interfering waves on the frequency axis. When the reception channel G is at a position that is inverted with respect to the channels E and F of the two interference waves on the frequency axis, the interference waves B and C obtained for calculating the attenuation of the reception level of the reception channel A are obtained. When the reception level detection result of the reception channel D and the reception level detection result of the interference waves E and F obtained for calculating the reception level attenuation amount of the reception channel G are used to calculate the reception level attenuation amount of the reception channel D. In this case, the amount of attenuation of the image channel can be quickly obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) In this embodiment, a receiving device of a base station will be described. As shown in FIG. 2, the receiving apparatus includes a plurality (n) of communication receiving units 3 prepared for receiving a required channel, a monitoring receiving unit 4 for monitoring a reception level of an interference wave, an antenna The communication device includes a distributor 2 for distributing a reception signal received from the communication receiver 1 to a plurality of communication receivers 3 and a plurality of monitoring receivers 4, and a CPU 5 for controlling the amount of attenuation of the reception level of the communication receiver.

The monitoring receiver 4 includes an RF front-end unit 6 composed of a filter, an amplifier, and a filter.
And a local synthesizer unit 8b having a PLL synthesizer circuit that oscillates a local signal by sequentially switching frequencies according to an instruction of a local control signal 13b of the CPU 5.
MIX 7b that mixes a local signal with a received signal to convert it to an IF signal, an IF amplifier 9b composed of a filter and an amplifier that extracts and amplifies the IF signal, and detects the IF signal and outputs it as a DC signal RSSI detector 10 and RS
An A / D converter 11b for A / D converting the output signal of the SI detector 10 and sending it to the CPU 5 is provided.

As shown in FIG. 1, the communication receiving unit 3 includes a filter for extracting a received signal, a variable attenuator 16 for attenuating a reception level, an RF including an amplifier and a filter.
Front end unit 15 and local control signal 13 of CPU 5
a, a local synthesizer unit 8a that oscillates a local signal of the frequency indicated by a, a MIX 7a that mixes the local signal with the received signal to convert it into an IF signal, and an IF that is composed of a filter and an amplifier that extracts and amplifies the IF signal. Amplifier
9a, a demodulator 17 having an RSSI detector function of detecting an IF signal and outputting a demodulated output 18 and outputting a DC signal of the demodulated signal as RSSI;
An A / D converter 11a for A / D converting the SSI and sending it to the CPU 5, and an attenuator control signal output from the CPU 5
A D / A converter 19 for converting the signal 14 into an analog signal and an attenuator control unit 20 for controlling the amount of attenuation of the variable attenuator 16 based on the attenuator control signal 14 are provided.

In this receiving apparatus, when setting the receiving channel of the communication receiving section 3, the CPU 5 selects an empty channel which is not affected by the intermodulation wave of the channel being used. However, since the use state of the channel constantly changes, and the intermodulation wave also changes accordingly, in this receiving apparatus, the monitoring receiver 4 uses the RS
The SI is constantly detected, and the CPU 5 calculates the level of the intermodulation wave that interferes with the required receiving channel from the RSSI, and based on the calculation result, determines the attenuation of the variable attenuator 16 of the communication receiver 3. Adjust within the range that does not fall below the specified SNR.

At this time, in the monitoring receiving section 4 for monitoring the interference channel, the local synthesizer section 8 b
The local signal of the frequency specified by the local control signal 13b of U5 is oscillated, and the MIX 7b mixes the received signal amplified by the RF front-end unit 6 with the local signal and converts the frequency to an IF signal. This IF signal is amplified by the IF amplifier 9b, detected by the RSSI detector 10, and output as RSSI. This RSSI
Is converted into a digital signal by the A / D converter 11b,
The data is input to the CPU 5 as the RSSI 12a.

In the communication receiving unit 3, the attenuator control signal 14 output from the CPU 5 is converted into an analog signal by the D / A converter 19 and input to the attenuator control unit 20. The attenuation of the variable attenuator 16 of the RF front end unit 15 is controlled based on the control signal. The reception level of the reception signal input to the RF front end unit 15 is adjusted by the variable attenuator 16.

The reception signal whose reception level has been adjusted is the MI signal.
At X7a, the signal is mixed with a local signal of the local synthesizer 8a for determining a required channel frequency, and is frequency-converted into an IF signal. The output signal of the MIX 7a is extracted and amplified by the IF amplifier 9a, detected by the demodulator 17 and output as a demodulated output 18. The detected DC signal is output as RSSI, converted into a digital signal by the A / D converter 11a, and input to the CPU 5.

The CPU 5 adjusts the attenuation of the variable attenuator 16 of the communication receiver 3 based on the RSSIs input from the monitoring receiver 4 and the communication receiver 3. To perform this operation, as shown in FIG. 3, the CPU 5 includes a channel frequency table 41a in which frequencies of all channels used in the transmission / reception system are described, a conversion table 41b of the reception level and the RSSI, a An IM calculation table 41c for calculating the IM level using the nosfigure (NF) of the circuit block, the gain of the amplifier, and the intercept point (IP) as calculation parameters; an IM level threshold table 41d describing allowable IM level thresholds; And an SNR threshold table 41e for defining an allowable S / N ratio.

The operation of the CPU 5 will be described with reference to the flowchart of FIG.

Step 1: Channel frequency table 41
a, calculating an interfering channel frequency for generating an IM on a required receiving channel, and extracting a disturbing channel and a channel generated by intermodulation of the disturbing channel. A local control signal 13b is sent to the local synthesizer 8b to control the frequency of the local signal so that the extracted interference channel can be received.

Step 4: RSSI from the monitoring receiver 4
When 12b is input, the reception level of the interference channel is calculated using the conversion table 41b of the reception level and the RSSI. The operations from step 2 to step 4 are performed for all of the interference channels extracted in step 2, and the operations are repeated. Accordingly, the local synthesizer 8b of the monitoring receiver 4 periodically scans the local frequency.

Step 5: The CPU 5 calculates the reception level (IM level) of the channel generated by the intermodulation of the interference wave from the reception level of the interference wave channel obtained in step 4 by using the IM calculation table 41c. Next, the difference between the IM level obtained in step 5 and the IM level threshold is calculated using the IM level threshold table 41d.

Step 7: The IM level is added to the reception level obtained from the RSSI 12a. The amount of attenuation required to reduce the IM level occupying the reception level by the difference obtained in step 6 or more is calculated. When the reception level is attenuated, the IM level is also attenuated at the same rate.

Step 8: The reception level (B) of the reception channel when the calculated attenuation is added is calculated. Step 9: The calculated reception level (B) is calculated based on the specified SNR described in the SNR threshold table 41e. Is compared with the reception level (C) for satisfying If B> C, Step 10: The attenuation obtained in Step 7 is designated to the attenuator controller 20 by the attenuation control signal 14.

Step 11: If B≤C in step 9, the attenuation of the variable attenuator 16 is set to 0, and the control of the variable attenuation 16 is stopped.

In FIG. 5, by controlling the attenuation of the variable attenuator, the reception level of the reception channel and the IM level are controlled.
The figure shows how the level changes.

As described above, the receiving apparatus of the first embodiment constantly monitors the reception level of the intermodulation wave that interferes with the reception channel while communicating on the required channel, and adjusts the IM level based on the monitoring. And it can control continuously.

Although the base station has been described in this embodiment, the same technique can be applied to the mobile station.

(Second Embodiment) In the second embodiment,
A description will be given of a case where the variable attenuation amounts of the plurality of communication receiving units 3 are controlled in the receiving device (FIGS. 1 and 2) of the first embodiment.

FIG. 6 shows the relationship between the frequencies of the receiving channels (desired wave: channel 1, desired wave: image channel 4) and the channels of the disturbing waves (channel 2, channel 3) of the two communication receivers. I have. Here f ₁ the frequency of the channel 1 of the desired wave is, f ₂ the frequency of the channel 2 of the interference wave, the frequency of the channel 3 of the interference wave f _3, also the frequency of the channel 4 of the desired wave and f _4,
Further, the frequency of IM ₁ (= 2f ₂ −f ₃ ) generated by the intermodulation of the interfering waves of channel 3 and channel 4 is equal to f _1, and the frequency of IM ₂ (= 2f ₃ −f ₂ ) is and equal to f _4. At this time, the channel 4 of the desired wave has a relationship of an image channel obtained by inverting the channel 1 with respect to the channels 2 and 3.

[0044] In communication receiver for receiving the channel 1, to detect the IM ₁ level, the procedure for setting the attenuation amount of the variable attenuator 16 in order to suppress the IM ₁ levels below the threshold value, the first This has been described in the embodiment.

F ₂ obtained for detecting the IM ₁ level
Data of the received level and f _3, in a communication receiver for receiving channel 4 is an image channel of the channel 1 can also be used when detecting the IM ₂ levels.

As described above, the mutual use of the detection data makes it possible to instantaneously perform the operation of setting the attenuation of the variable attenuator 16 in the communication receiver for receiving the image channel. .

FIG. 7 shows the relationship of FIG. 6 in a further enlarged manner. Here, the frequency of channel 1 of the desired wave is f
₁ , the frequency of the disturbance wave channel 2 is f ₂ , the frequency of the disturbance wave channel 3 is f ₃ , the frequency of the desired wave channel 4 is f ₄ , the frequency of the disturbance wave channel 5 is f ₅ , the disturbance wave channel The frequency of channel ₆ is f ₆ , and the frequency of channel 7 of the desired wave is f ₇ . Also, channel 3
Generated by intermodulation of interfering waves of channel 4 and channel 4
The frequency of ₁ (= 2f ₂ −f ₃ ) is equal to f ₁ and IM ₂ (=
2f ₃ −f ₂ ) is equal to f _4, and the frequency of IM ₃ (= 2f ₅ −f ₆ ) generated by intermodulation of the interfering waves of channel 5 and channel 6 is equal to f _{4. Four}
(= 2f ₆ -f ₅₎ frequency is equal to f _7.

At this time, channel 4 is replaced with channel 2
And channel 3 is the channel 1 image channel, and at the same time channel 5 and channel 6 is the channel 7 image channel.

In order to set the attenuation of the variable attenuator 16 in the communication receiving unit for receiving the channel 4,
As IM level, it is necessary to determine the level of the accumulated sum of the IM ₂ and IM _3, the calculation of IM ₂ levels were determined for IM ₁ level detected by the communication receiver that receives channel 1 it is possible to use the data of the reception level of f ₂ and f _3, also in the calculation of IM ₃ levels, f ₅ and the communication reception section that receives a channel 7 was determined for IM ₄ level detection data of the received level of the f ₆ can be utilized.

As described above, in the communication receiving unit that receives the image channel, the setting operation of the attenuation of the variable attenuator 16 is efficiently performed by using the data detected by the other communication receiving units. be able to.

[0051]

As is apparent from the above description, the receiving apparatus of the present invention can continuously and accurately suppress the IM level that interferes with the receiving channel while continuing communication, and can improve the communication quality. Improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a receiving device according to a first embodiment of the present invention;

FIG. 2 is a block diagram showing a configuration of a receiving device of a base station according to the first embodiment of the present invention;

FIG. 3 is a diagram showing a table used in a receiving method according to the first embodiment of the present invention;

FIG. 4 is a flowchart showing a receiving method according to the first embodiment of the present invention;

FIG. 5 shows a reception level of a required channel and an IM based on an interference channel according to the reception method of the first embodiment of the present invention
Diagram showing how the level changes,

FIG. 6 is a diagram illustrating a relationship between a desired wave channel and an interference channel, illustrating a receiving method according to a second embodiment of the present invention;

FIG. 7 is a diagram illustrating another relationship between a desired wave channel and a jamming channel for explaining a receiving method according to the second embodiment of the present invention;

FIG. 8 is a block diagram illustrating a configuration of a conventional receiving apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Receiving antenna 2 Distributor 3 Communication receiving unit 4 Monitoring receiving unit 5 CPU 6 RF front end unit 7 MIX 8a, 8b Local synthesizer unit 9a, 9b IF amplifier unit 10 RSSI detector 11a, 11b A / D converter 12a, 12b RSSI 13a, 13b Local control signal 14 Attenuator control signal 15 RF front end section 16 Variable attenuator 17 Demodulation section. 18 Demodulation output 19 D / A converter 20 Attenuator control section 21 RF IN 22 RF front end section 23 LNA 24 Down converter 25 Local oscillator 26 IF AGC unit. 27 Demodulator 28 A / D converter 29, 30 Gain adjustment forming unit 31, 32 D / A converter, 33 RSSI TH CONTROL

Claims (6)

[Claims] 1. A receiving device of a transmitting / receiving system for transmitting / receiving using a plurality of channels, comprising: a communication receiving unit that receives a required channel and includes a variable attenuator for attenuating a reception level; A monitoring receiver for detecting the reception level of the channel of the interference wave, and control means for controlling the attenuation of the variable attenuator of the communication receiver based on the detection result of the monitoring receiver,
The monitoring receiver detects reception levels of a plurality of interfering waves that generate an intermodulation wave that interferes with the required channel, and the control unit detects the reception level of the interfering waves detected by the monitoring receiver. A receiving device that calculates a reception level of the intermodulation wave and controls an attenuation amount of the variable attenuator so that a reception level of the intermodulation wave in a reception level of the required channel is equal to or less than a threshold. . 2. The monitoring receiver according to claim 1, wherein the monitoring receiver periodically scans a plurality of channels of the interfering wave to detect a reception level of the interfering wave. The receiving device according to claim 1, wherein the amount is continuously controlled. 3. A reception method in a transmission / reception system in which transmission / reception is performed using a plurality of channels, wherein a reception level of a required reception channel is detected and an intermodulation wave that interferes with the required reception channel is generated. The reception level of the plurality of interfering waves is detected, and the reception level of the intermodulation wave is obtained from the reception levels of the plurality of detected interference waves, and the reception level of the intermodulation wave in the reception level of the required reception channel is equal to or less than a threshold. A receiving level of the required receiving channel is attenuated such that 4. An SNR of a demodulated output when the reception level of the required reception channel is attenuated is calculated.
4. The receiving method according to claim 3, wherein the attenuation is performed only when the value exceeds a threshold. 5. When the receiving channel A and the receiving channel D are at positions that are inverted with respect to the two interfering channels B and C on the frequency axis, the amount of attenuation of the receiving level of the receiving channel A is calculated. 4. The reception method according to claim 3, wherein the detection results of the reception levels of the interfering waves B and C obtained for the reception are used also when calculating the attenuation of the reception level of the reception channel D. . 6. The receiving channel A and the receiving channel D are located at positions that are inverted with respect to the two interfering wave channels B and C on the frequency axis, and the receiving channel D and the receiving channel G are Detection of the reception levels of the interfering waves B and C obtained to calculate the amount of attenuation of the receiving level of the receiving channel A when the two interfering waves are at positions inverted with respect to the channels E and F on the axis. The result and the detection result of the reception level of the interference waves E and F obtained for calculating the attenuation level of the reception level of the reception channel G are also used for calculating the attenuation level of the reception level of the reception channel D. The receiving method according to claim 3, wherein the receiving method is used.