JP3679325B2 - Diversity receiver and orthogonal frequency division multiplex signal receiving method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diversity receiver that receives a radio signal using a plurality of antennas, and more particularly to a diversity receiver that receives a signal subjected to orthogonal frequency division multiplexing on a transmission side.
[0002]
[Prior art]
An orthogonal frequency division multiplexing (OFDM) method is known as a method for transmitting digital signals wirelessly.
In this orthogonal frequency division multiplexing system, a digital signal can be efficiently transmitted by multiplexing and transmitting the digital signal using a number of subcarriers having different frequencies. Also, in the orthogonal frequency division multiplexing scheme, by providing a guard interval section in front of an effective symbol section, it is possible to prevent deterioration of reception characteristics due to intersymbol interference even when multipath occurs.
[0003]
2. Description of the Related Art Conventionally, an antenna switching type diversity receiver as shown in FIG. 3 is known as a means for reducing the influence of fading caused by mobile reception of a radio signal subjected to such orthogonal frequency division multiplexing.
[0004]
The conventional diversity receiver shown in FIG. 3 amplifies the received signals received by the antennas 18 to 21 by the LNAs 22 to 25 and inputs them to the selector 26. The selector 26 selects one received signal based on the select signal from the demodulator 28 and inputs it to the tuner 27. The tuner 27 converts an RF (Radio Frequency) signal in a desired band into an IF (Intermediate Frequency) signal and sends it to the demodulator 28.
[0005]
The tuner 27 detects the signal level of the received signal and notifies the demodulator 28 using a signal RSSI (Received Signal Strength Indication) indicating the received signal strength. The demodulator 28 monitors the signal RSSI, and controls the selector 26 to switch the selection of the received signal when the signal level falls below a predetermined threshold value. If the signal level after the selection is switched is also below the threshold, the operation for switching the selection is further repeated.
[0006]
[Problems to be solved by the invention]
In the conventional diversity receiver, it is impossible to detect in advance whether or not the signal level of the received signal is increased by switching the selection of the received signal. For this reason, the reception state after switching may be worse than that before switching, and signals subjected to orthogonal frequency division multiplexing may not be received stably.
[0007]
In addition, when the demodulator 28 shown in FIG. 3 demodulates a digital signal transmitted with a configuration using a signal equalization circuit, the frequency characteristic changes abruptly by switching the selection of the received signal. In some cases, an error in equalization becomes large, and a possibility that a demodulation error occurs is increased.
[0008]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a diversity receiver that can stably receive a signal subjected to orthogonal frequency division multiplexing.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a diversity receiver according to the first aspect of the present invention provides:
A signal subjected to orthogonal frequency division multiplexing is received using a plurality of antennas,
A plurality of amplifying means for amplifying received signals received by the respective antennas;
A plurality of attenuation means for attenuating the received signal amplified by each of the amplifying means with a variable amount of attenuation;
Signal combining means for combining the received signals attenuated by the plurality of attenuation means;
Demodulating a digital signal from the signal synthesized by the signal synthesizing means, and a demodulating means for switching and controlling attenuation amounts in the plurality of attenuation means,
The demodulating means includes
When switching the attenuation amounts in the plurality of attenuation means, the data indicating any one of the plurality of attenuation means is stored in a predetermined storage means, thereby switching the attenuation amount among the plurality of attenuation means. An attenuation target specifying means for specifying
When switching the attenuation amounts in the plurality of attenuation means, data indicating the minimum attenuation amount among the plurality of attenuation means is stored in a predetermined storage means, whereby the plurality of attenuation means A fixed target specifying means for specifying a fixed amount of attenuation among them ,
Among the plurality of attenuation means, when the attenuation amount in the plurality of attenuation means is switched and controlled, the attenuation means having the smallest attenuation amount includes at least one attenuation means designated by the fixed target designating means. Control the attenuation in one attenuation means to be kept to a minimum,
It is characterized by that.
[0010]
According to the present invention, the demodulating means demodulates the digital signal from the signal synthesized by the signal synthesizing means and switches and controls the attenuation amounts in the plurality of attenuating means. Further, the demodulating means can specify the attenuating means for fixing the attenuation amount by the designation of the fixation target designating means when switching the attenuation amounts in the plurality of attenuating means.
In this way, the demodulating means can set an appropriate attenuation amount by fixing one of the attenuation amounts in the plurality of attenuation means by a simple process when switching the attenuation amount. Can do.
In other words, it is possible to demodulate a transmitted digital signal without switching received signals received by a plurality of antennas, and when controlling attenuation switching, a decrease in reception level is prevented and an appropriate attenuation is obtained. Can be set. Thereby, it is possible to stably receive a signal subjected to orthogonal frequency division multiplexing.
[0011]
More specifically, the demodulating means, when switching and controlling the amount of attenuation in the plurality of attenuating means, the attenuating means designated by the attenuating target designating means and the attenuating means designated by the fixed target designating means, Are determined to be the same, and if it is determined to be the same, it is desirable to change the attenuation means designated by the attenuation target designating means and to control the attenuation to be switched.
[0013]
An orthogonal frequency division multiplex signal receiving method according to a second aspect of the present invention includes:
A method for receiving signals subjected to orthogonal frequency division multiplexing using a plurality of antennas,
An amplification step of amplifying the received signal received by each of the antennas;
Attenuation step for attenuating the received signal amplified in the amplifying step by using a plurality of attenuators and attenuating variable amounts corresponding to the antennas,
A signal synthesis step of synthesizing the reception signal attenuated in the attenuation step;
A demodulating step for demodulating a digital signal from the signal synthesized in the signal synthesizing step, and for switching and controlling an attenuation amount when the received signal is attenuated corresponding to each antenna in the attenuation step;
The demodulating step stores the data indicating one of the plurality of attenuators in a predetermined storage unit when switching the attenuation amount in the attenuation step of the received signal corresponding to each antenna, thereby storing the plural Attenuator for switching the attenuation amount is designated by the first pointer, and data indicating the attenuation amount of the plurality of attenuators being the smallest is stored in a predetermined storage means , whereby the plurality of attenuators are switched. Attenuator with a fixed attenuation is designated by the second pointer, and it is determined whether or not the attenuator designated by the first pointer and the attenuator designated by the second pointer are the same. and, if determined to be the same, by changing the attenuator specified by the first pointer, Controls switching to apply attenuation while maintaining a minimum at least in any one attenuation of the serial plurality of attenuators,
It is characterized by that.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, diversity receiver 100 according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 1 is a diagram showing a configuration of a diversity receiver 100 according to the embodiment of the present invention.
As shown, the diversity receiver 100 includes a plurality of antennas 1 to 4, a plurality of LNAs (Low Noise Amplifiers) 5 to 8, a plurality of variable attenuators 9 to 12, a mixer 13, and a tuner 14. And a demodulator 15.
[0017]
The plurality of antennas 1 to 4 are for receiving orthogonal frequency division multiplexing (OFDM) on the transmission side and receiving RF (Radio Frequency) signals transmitted wirelessly. The antenna 1 is coupled to the variable attenuator 9 via the LNA 5. The antenna 2 is coupled to the variable attenuator 10 via the LNA 6. The antenna 3 is coupled to the variable attenuator 11 via the LNA 7. The antenna 4 is coupled to the variable attenuator 12 via the LNA 8.
[0018]
Here, the RF signal subjected to orthogonal frequency division multiplexing received by the plurality of antennas 1 to 4 is a signal for transmitting digital data using a number of subcarriers orthogonal to each other in a symbol period. The symbol interval of the period is divided into an effective symbol interval and a guard interval interval. The guard interval interval is a redundant signal interval that is preceded by an effective symbol interval with a symbol period and is copied from the rear portion of the effective symbol interval.
[0019]
The plurality of LNAs 5 to 8 are amplifier circuits that are provided corresponding to the respective antennas 1 to 4 and amplify the received signal.
The LNAs 5 to 8 send the amplified received signals to the variable attenuators 9 to 12 that are coupled to each other.
[0020]
The plurality of variable attenuators 9 to 12 are attenuation circuits for defining attenuation amounts according to the control signals sent from the demodulator 15 and attenuating the signals received from the LNAs 5 to 8 with variable attenuation amounts. That is, the variable attenuator 9 attenuates the signal received from the LNA 5 by an attenuation amount corresponding to the level of the signal C_ANT1 sent from the demodulator 15. The variable attenuator 10 attenuates the signal received from the LNA 6 by an attenuation amount corresponding to the level of the signal C_ANT2 sent from the demodulator 15. The variable attenuator 11 attenuates the signal received from the LNA 7 by an attenuation amount corresponding to the level of the signal C_ANT3 sent from the demodulator 15. The variable attenuator 12 attenuates the signal received from the LNA 8 by an attenuation amount corresponding to the level of the signal C_ANT4 sent from the demodulator 15.
For example, when the level of the signals C_ANT1 to C_ANT4 is high, the attenuation amount in each of the variable attenuators 9 to 12 is large, and when the level is low, the attenuation amount is small. When the levels of the signals C_ANT1 to C_ANT4 are the lowest, the attenuation amount in each of the variable attenuators 9 to 12 is zero.
[0021]
The mixer 13 is for adding and combining the received signals sent from the plurality of variable attenuators 9 to 12.
The mixer 13 sends a signal obtained by combining the received signals to the tuner 14.
[0022]
The tuner 14 includes a down converter, a band-pass filter, and the like, and selects and extracts a received signal that transmits a desired digital signal, and performs IF (Intermediate).
This is for conversion to a frequency (intermediate frequency) signal.
Further, the tuner 14 measures the received signal strength based on the magnitude of the received signal sent from the mixer 13, generates a signal RSSI having a signal level corresponding to the received level, and supplies the signal RSSI to the demodulator 15. .
[0023]
The demodulator 15 includes an A / D (Analog / Digital) converter, an FFT (Fast Fourier Transform) circuit, a signal equalization circuit, a demapping circuit, and the like, and performs orthogonal frequency division from the IF signal extracted by the tuner 14. The digital signal transmitted by the multiplexing method is demodulated and output as demodulated data.
[0024]
Here, the demodulator 15 generates signals C_ANT1 to C_ANT4 and sends them to the variable attenuators 9 to 12, respectively, thereby controlling the attenuation of the received signals received by the antennas 1 to 4.
The demodulator 15 includes an antenna control pointer 16 and an antenna fixed pointer 17.
[0025]
The antenna control pointer 16 is for designating a variable attenuator 9 to 12 to be subjected to attenuation switching control.
For example, the antenna control pointer 16 designates a variable attenuator to be subjected to attenuation switching control by storing data indicating one of the variable attenuators 9 to 12 in the semiconductor memory.
[0026]
The antenna fixing pointer 17 is used to designate one of the variable attenuators 9 to 12 that fixes the attenuation amount to zero when the attenuation amount switching control is performed.
For example, the antenna fixed pointer 17 stores data indicating any one of the variable attenuators 9 to 12 in the semiconductor memory, thereby performing attenuation control when switching the attenuation amount and performing measurement of the reception level or the like. Specifies a variable attenuator that fixes the amount to zero.
[0027]
The operation of diversity receiver 100 according to the embodiment of the present invention will be described below.
An RF signal that is subjected to orthogonal frequency division multiplexing on the transmission side and transmitted wirelessly is received by a plurality of antennas 1 to 4.
[0028]
Signals received by the plurality of antennas 1 to 4 are sent to the LNAs 5 to 8 and amplified, and then sent to the variable attenuators 9 to 12.
[0029]
Each of the variable attenuators 9 to 12 attenuates the reception signals received by the plurality of antennas 1 to 4 with an attenuation corresponding to the levels of the signals C_ANT1 to C_ANT4 received from the demodulator 15 and sends the attenuated signals to the mixer 13.
[0030]
The mixer 13 combines the received signals received from the variable attenuators 9 to 12 and sends the synthesized signals to the tuner 14.
[0031]
The tuner 14 selects and extracts a received signal in a band for transmitting a desired digital signal from the signal synthesized by the mixer 13, converts it to an IF signal, and sends the IF signal to the demodulator 15. At this time, the tuner 14 measures the received signal strength from the magnitude of the received signal, generates a signal RSSI indicating the received level, and sends it to the demodulator 15.
[0032]
The demodulator 15 detects a valid symbol period of the received signal, for example, and executes processing for demodulating the digital signal, such as fast Fourier transform and signal equalization processing.
[0033]
Here, the demodulator 15 generates signals C_ANT1 to C_ANT4 and sends them to the variable attenuators 9 to 12, respectively, thereby controlling the attenuation amount in each of the variable attenuators 9 to 12.
For example, the demodulator 15 changes the reception level by switching the attenuation amount while sequentially changing the attenuation attenuators among the variable attenuators 9 to 12 in order to improve the reception state. Set the appropriate attenuation by measuring.
[0034]
At this time, the demodulator 15 switches the attenuation amount in each of the variable attenuators 9 to 12 so that at least one of the attenuation amounts in the variable attenuators 9 to 12 becomes zero in order to prevent the reception level from decreasing. Control.
[0035]
That is, the demodulator 15 uses the variable attenuator 9 to 12 as the antenna affixing pointer to the variable attenuator whose current attenuation is zero and also holds the attenuation to zero when the attenuation is switched. 17 is specified.
[0036]
The operation when the demodulator 15 switches and controls the attenuation in the variable attenuators 9 to 12 will be described below with reference to the flowchart shown in FIG.
[0037]
When the demodulator 15 identifies one of the variable attenuators 9 to 12 whose attenuation is to be switched, the demodulator 15 changes the variable attenuator designated by the antenna control pointer 16 to the one whose attenuation is to be switched (step S1).
[0038]
At this time, the demodulator 15 determines whether or not the variable attenuator designated by the antenna control pointer 16 and the variable attenuator designated by the antenna fixed pointer 17 are the same (step S2).
[0039]
When the demodulator 15 determines that the variable attenuators designated by the two pointers are the same (YES in step S2), the process returns to step S1 and the variable attenuator designated by the antenna control pointer 16 is determined. Further change.
That is, when the variable attenuator set in the antenna control pointer 16 and the variable attenuator designated by the antenna fixed pointer 17 match, the demodulator 15 changes the variable attenuator to be switched of the attenuation amount to another variable attenuator. change.
Thereby, the demodulator 15 can prescribe | regulate operation | movement so that the attenuation amount in what was designated with the antenna fixed pointer 17 among the variable attenuators 9-12 may not be switched.
[0040]
On the other hand, when the demodulator 15 determines that the variable attenuators designated by the antenna control pointer 16 and the antenna fixed pointer 17 are not the same (NO in step S2), the demodulator 15 performs an attenuation switching operation (step S3).
That is, the demodulator 15 switches the attenuation amount of the variable attenuator 9 to 12 designated by the antenna control pointer 16 by changing the level of the signals C_ANT1 to C_ANT4, for example. At this time, the demodulator 15 sets a more appropriate attenuation amount by measuring the reception level from the signal RSSI sent from the tuner 14.
Accordingly, it is possible to set a more appropriate attenuation amount by switching and controlling the attenuation amount while fixing at least one of the attenuation amounts in the variable attenuators 9 to 12 to zero. That is, it becomes possible to stably receive a signal subjected to orthogonal frequency division multiplexing.
[0041]
After that, the demodulator 15 determines whether or not the attenuation at the variable attenuator whose attenuation has been switched, that is, the attenuation at the variable attenuator designated by the antenna control pointer 16 is zero (step S4). .
[0042]
When the demodulator 15 determines that the amount of attenuation in the variable attenuator designated by the antenna control pointer 16 is zero (YES in step S4), the demodulator 15 sends the variable attenuator designated by the antenna control pointer 16 to the antenna fixed pointer 17. Set (step S5).
As a result, the demodulator 15 can change the variable attenuator that fixes the attenuation amount to zero the next time when the attenuation amount in the variable attenuators 9 to 12 is controlled to be switched, and specify a more appropriate attenuation amount. Can do.
[0043]
On the other hand, when demodulator 15 determines that the amount of attenuation in the variable attenuator designated by antenna control pointer 16 is not zero (NO in step S4), it skips step S5 and switches the attenuation. End the operation.
[0044]
In this way, when the attenuation amount in the variable attenuators 9 to 12 is switched and controlled, the attenuation amount in the variable attenuator 9 to 12 designated by the antenna fixing pointer 17 is fixed. Accordingly, it is possible to set a more appropriate attenuation amount by switching control of the attenuation amount with a simple process while fixing at least one of the attenuation amounts in the variable attenuators 9 to 12 to zero. That is, it is possible to prevent a decrease in reception level when switching the attenuation amount, and to stably receive a signal subjected to orthogonal frequency division multiplexing.
[0045]
As described above, according to the present invention, the demodulator 15 that switches and controls the attenuation amount in the variable attenuators 9 to 12 fixes the attenuation amount of the variable attenuator designated by the antenna fixing pointer 17 to adjust the attenuation amount. Execute switching control.
As a result, with simple processing, at least one of the attenuation amounts in the variable attenuators 9 to 12 is fixed to zero, and the attenuation amounts of the other variable attenuators are switched and controlled to perform orthogonal frequency division multiplexing. The received signal can be received stably.
[0046]
Further, according to the present invention, the selection of the received signal is not switched as in the prior art.
For this reason, it is possible to prevent the frequency characteristics of the received signal from changing suddenly, and it is possible to stably receive a signal subjected to orthogonal frequency division multiplexing.
[0047]
The present invention is not limited to the above embodiment, and various modifications and applications are possible.
For example, in the above-described embodiment, it has been described that the signals transmitted wirelessly are received by the four antennas 1 to 4. In consideration, a signal subjected to orthogonal frequency division multiplexing may be received by an arbitrary number of antennas.
[0048]
【The invention's effect】
As described above, according to the present invention, when performing switching control of attenuation amounts in a plurality of variable attenuators, at least any one attenuation amount is fixed to zero, and an appropriate attenuation amount can be obtained by simple processing. Can be set.
Thereby, it is possible to stably receive a signal subjected to orthogonal frequency division multiplexing.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a diversity receiver according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining an operation when a demodulator switches and controls attenuation in a variable attenuator.
FIG. 3 is a diagram illustrating a configuration of a conventional diversity receiver.
[Explanation of symbols]
1-4, 18-21 Antenna 5-8, 22-25 LNA
9 to 12 Variable attenuator 13 Mixer 14, 27 Tuner 15, 28 Demodulator 16 Antenna control pointer 17 Antenna fixed pointer 26 Selector 100 Diversity receiver

Claims (3)

A diversity receiver that receives signals subjected to orthogonal frequency division multiplexing using a plurality of antennas,
A plurality of amplifying means for amplifying received signals received by the antennas;
A plurality of attenuation means for attenuating the received signal amplified by each of the amplifying means in a variable amount of attenuation;
Signal combining means for combining the reception signals attenuated by the plurality of attenuation means;
Demodulating a digital signal from the signal synthesized by the signal synthesizing means, and a demodulating means for switching and controlling attenuation amounts in the plurality of attenuation means,
The demodulating means includes
When switching the attenuation amount in the plurality of attenuation means, data indicating any one of the plurality of attenuation means is stored in a predetermined storage means, thereby switching the attenuation amount among the plurality of attenuation means An attenuation target specifying means for specifying
When switching the attenuation amounts in the plurality of attenuation means, the data indicating the minimum attenuation amount among the plurality of attenuation means is stored in a predetermined storage means, whereby the plurality of attenuation means A fixed target specifying means for specifying a fixed amount of attenuation among them ,
Among the plurality of attenuation means, when the attenuation amount in the plurality of attenuation means is switched and controlled, the attenuation means having the smallest attenuation amount includes at least one attenuation means including the attenuation means designated by the fixed target designating means. Control the attenuation in one attenuation means to be kept to a minimum,
A diversity receiver characterized by that. When the demodulating means performs switching control of the attenuation amounts in the plurality of attenuating means, the attenuating means designated by the attenuating target designating means and the attenuating means designated by the fixed target designating means are the same. If it is determined that they are the same, the attenuation means designated by the attenuation target designating means is changed, and the attenuation amount is switched and controlled.
The diversity receiver according to claim 1. An orthogonal frequency division multiplexing signal receiving method for receiving a signal subjected to orthogonal frequency division multiplexing using a plurality of antennas,
An amplification step of amplifying the received signal received by each of the antennas;
Attenuation step for attenuating the received signal amplified in the amplifying step by using a plurality of attenuators and attenuating variable amounts corresponding to the antennas,
A signal synthesis step of synthesizing the reception signal attenuated in the attenuation step;
A demodulating step for demodulating a digital signal from the signal synthesized in the signal synthesizing step, and for switching and controlling an attenuation amount when the received signal is attenuated corresponding to each antenna in the attenuation step;
The demodulating step stores the data indicating any one of the plurality of attenuators in a predetermined storage unit when switching the attenuation amount in the attenuation step of the received signal corresponding to each antenna, and Attenuator for switching the amount of attenuation is designated by a first pointer, and data indicating the minimum amount of attenuation among the plurality of attenuators is stored in a predetermined storage means . Attenuator with a fixed attenuation is designated by the second pointer, and it is determined whether or not the attenuator designated by the first pointer and the attenuator designated by the second pointer are the same. and, if determined to be the same, by changing the attenuator specified by the first pointer, Controls switching to apply attenuation while maintaining a minimum at least in any one attenuation of the serial plurality of attenuators,
An orthogonal frequency division multiplex signal receiving method.

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