JPH09307490A - Diversity reception method and its device for high speed data transmission system in high speed mobile communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reception error rate by using a circuit of a simple configuration consisting of a level discrimination circuit, a voltage comparator and a changeover circuit so as to realize effective frequency diversity and space diversity. SOLUTION: A LEV 19 is a level discrimination circuit for reception input level and always monitors AGC voltages a1 , b1 , a2 , b2 from receivers 31 , 32 , 41 , 42 , selects a receiver whose output level is maximum, discriminates a frequency of the selected receiver and outputs a frequency switching signal (d) to a SW 17. When the reception level of the selected receiver is a preset threshold voltage or below, the LEV 19 again compares the AGC voltages a1 -b2 received from the receivers 31 , 32 , 41 , 42 , selects a frequency of the receiver whose reception level is maximum and outputs a frequency switching signal (d) to the SW 17. Two receivers with the frequency designated by the frequency switching signal (d) are selected and a receiver witching signal C1 or C2 received from a COMP 18 is used to conduct space diversity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed data transmission system for high-speed mobile radio such as a train radio that travels on a track, and particularly to a diversity in a high-speed data transmission system using a zone wrap method using millimeter waves with severe fading. The present invention relates to a receiving method and its device.

[0002]

2. Description of the Related Art Diversity reception is conventionally known as a remedy for the deterioration of the code error rate due to the reduction of received power caused by coherent fading.

Specific methods for realizing diversity reception include frequency diversity and space diversity. As a method using both of them, for example, FIG.
It is a block diagram which shows the conventional diversity receiving method shown by 5732 publication. In the figure, 1 and 2 are two antennas for space diversity, and 3 and 4 are two receivers whose reception frequencies can be set independently of each other. 5 and 6 are high frequency amplifiers, 7 and 8 are frequency converters, 9 and 10 are local oscillators, 11 and 12 are intermediate frequency amplifiers, 1
Reference numerals 3 and 14 are demodulation circuits, and 15 and 16 are AGC circuits, which are respectively referred to as RFA, MIX, OSC, IFA,
It is written as DEM and AGC. The configuration of this receiver is OSC9
The output frequency of 10 and 10 (that is, the reception frequency) can be switched from the outside. 37 is both receivers 3,
A switching circuit (hereinafter, referred to as SW) that selects one of the four outputs that has a good reception state and a large output level, 38
Is a voltage comparator (hereinafter referred to as COMP) that compares the output levels of the AGCs 15 and 16 of both receivers 3 and 4 to give a switching signal to the SW 37. Since the AGC output voltage of the receiver becomes the voltage corresponding to the input level of the receiver,
The AGC circuits 15 and 16 are used as comparison inputs of the COMP 38.
Using the output of, the reception input levels of both receivers 3 and 4 can be compared. Reference numeral 39 is a reception input level determination circuit (hereinafter referred to as LEV), which determines whether or not the AGC voltage of the receiver having the higher level exceeds a preset threshold voltage. 30 determines from the outputs of COMP 38 and LEV 39 whether to change the frequency of the receiver, and sends control signals c _{1 to} OSC 9 and OSC _10.
And c ₂ respectively, to control the reception frequency of the receivers 3 and 4 (hereinafter referred to as CONT). If the threshold level for determining the reception level is set to a level slightly higher than the level at which reception is poor, by performing space diversity while selecting the frequency with the better reception level, frequency diversity and space diversity We have realized a diversity reception method that makes the most of both advantages.

[0004]

In the above-mentioned conventional diversity reception method, both receivers always receive at the same reception frequency, and the reception frequency is switched to the other reception frequency by OSC due to the drop of the AGC voltage. However, since the reception level of the reception frequency that is not selected cannot be detected when this reception frequency is switched (Japanese Patent Publication No.
(See page 1, column 1, line 10 to column 2, line 9), switching is performed even when the reception level of the reception frequency after switching is low. In addition, the frequency of the received data is changed abruptly at the time of switching the reception frequency, which increases the error rate of output data in the baseband, and the signal error rate increases as the transmission / reception transmission signal speed increases. was there.

It is an object of the present invention to realize effective frequency diversity and spatial diversity by using a reception level measuring circuit having a simple structure to improve the reception error rate, especially for high speed mobile communication using millimeter waves. A diversity receiving method and apparatus suitable for a high-speed data transmission system.

[0006]

That is, the diversity receiving method of the present invention is such that at least two independent antennas for receiving the same radio signal modulated to at least two different frequencies are connected to each of the antennas. Selected receivers each having a reception frequency corresponding to each frequency, and comparing the reception levels of all the receivers to select the receiver having the highest reception level; A second step of selecting a receiver having the highest reception level from among the receivers having the same reception frequency as the receiver having the highest reception level and outputting by the receiver. The reception level detection values of the receiver and all other receivers having the same reception frequency as the receiver are less than or equal to a preset threshold level value. When it has been decided to again perform the said first and second steps. In the first step, frequency diversity of the radio signal is performed, and in the second step, space diversity of the radio signal is performed. Furthermore, it is assumed that the frequency diversity is switched after demodulation.

Further, the diversity receiver of the present invention is
At least two independent antennas for receiving the same radio signal modulated to at least two different frequencies, and a separate receiver connected to each of the antennas and having a reception frequency corresponding to each of said frequencies; While comparing the reception levels of all receivers and selecting the receiver with the highest reception level, the reception levels of the selected receiver and all other receivers that have the same reception frequency as the receiver are preset. Level determination circuit that repeats the selection operation of the receiver with the highest reception level when the threshold value becomes less than or equal to the specified threshold level value, and one receiver with the highest reception level than the receivers with the same reception frequency. The level is judged from the voltage comparator that selects for each receiver frequency for all receivers and the received output of all receivers. Having a frequency of a receiver selects the road, the largest receiving level selected voltage comparators 1
And a switching circuit for selecting and switching one of the receivers.

As described above, the diversity receiving method and apparatus of the high-speed data transmission system according to the present invention reduces the data error rate at the time of frequency switching by performing the frequency diversity switching after demodulation, so that all receivers can be operated at all times. By monitoring the received electric field of, it is possible to provide diversity reception that selects the receiver with the best reception level.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of the diversity receiving method of the present invention.
FIG. 2 is a block diagram showing the configuration of a receiving device using an example embodiment.
is there. In the figure, 1 and 2 are 2 for space diversity.
3 antennas₁ , 4₁ Is the reception frequency f₁ Receiver,
Three_Two , 4_Two Is the reception frequency f_TwoReceiver. 21₁ ,
21_Two , 22₁ , 22_Two Are high-frequency amplifier and frequency
A number converter, a local oscillator, a receiver including an intermediate frequency amplifier,
13₁ , 13_Two , 14 ₁ , 14_Two Is a demodulation circuit, 15₁ ,
Fifteen_Two , 16₁ , 16_Two Is an AGC circuit. 17 received
Belief 3₁ , 3_Two , 4₁ , 4_Two Of the output of the reception level
Greater reception level than two receivers with large frequency
Switching circuit (hereinafter referred to as SW) that selects one of the outputs, 1
8 is a receiver switching signal c to SW17₁ , C_Two To give
To receiver 3₁ And 4₁ AGC circuit 15₁ , 16₁ Enter from
AGC voltage a₁ And a_Two And also receiver 3_Two 
And 4_Two AGC circuit 15_Two , 16_Two Input from AGC
Voltage b₁ And b_Two Voltage comparator (hereinafter, COMP
And the receiver switching signal for each case.
Issue c₁ And c_Two Is output. The AGC output voltage of the receiver is
Since the voltage corresponds to the input level of the receiver, COM
The AGC circuit 15 is used as a comparison input for P18.₁ , 15_Two , 1
6₁ , 16_Two If you use the output of receiver 3,₁ And 4₁ And 3
_Two And 4_Two You can compare the received input levels of
Wear. Reference numeral 19 is a level determination circuit for the reception input level (hereinafter,
LEV), receiver 3₁ And 3 _Two , 4₁ And 4_Two 
AGC voltage a from₁ And b₁ , A_Two And b_Two Always supervised
Select the receiver with the highest output level and
The frequency of the receiver is judged and the frequency switching signal d is sent to SW17.
Output.

The LEV 19 is a reception signal input from the receiver.
Select the receiver frequency with the highest level and select
The threshold level for which the receiver's reception level is preset
If the voltage drops below the threshold voltage, the receiver 3₁ Or 4_Two 
AGC voltage a input from ₁, A_Two , B₁ , B_Two Ratio
And select the frequency of the receiver with the highest reception level.
And outputs the frequency switching signal d to SW17. SW17
Are two of the frequencies specified by the frequency switching signal d.
Select the receiver and input from COMP18
Machine switching signal c₁ Or c_Two Space diversity
To do.

FIG. 2 is a waveform example for explaining the operation of the circuit of FIG.
In the figure, 2 frequencies f₁ , F_Two And receiver 3 depending on the reception level
₁ , 3_Two , 4₁ , 4_Two An example of automatic selection of
You. The frequency of the two waves received is f₁ And f_Two And FIG.
Waveform a₁ And a_Two Is the frequency at antennas 1 and 2 respectively
Number f₁ Receiver 3 when receiving₁ And 4₁ Receiving level
(AGC voltage), b₁ And b_Two Are each Anne
Frequency f with tenor 1 and 2 _Two Receiver 3 when receiving
_Two , 4_Two Shows the reception level (AGC voltage). Receiver off
Replacement signal c₁ Is the reception level a₁ , A_Two With COMP18
The waveforms are compared and the receiver 3₁ The reception level of is high
When level 1 and receiver 4₁ The reception level of is high
When it reaches the threshold, it indicates level 0. Receiver switching signal c_Two Is
Confidence level b₁, B_Two Is a waveform compared by COMP18.
Receiver 3_Two Level 1 when the reception level of is high
And receiver 4_Two When the reception level of is high, the level
Indicates 0. The frequency switching signal d has a signal level a₁ And a
_Two , B₁ And b_Two Is above the threshold level
Frequency selection output from LEV19 detecting whether
The waveform is shown. The level of the frequency switching signal d is 1 in SW17.
When the receiver 3₁ , 4₁ Output (frequency f₁ )
Receiver is 0 when Le is 0_Two , 4_Two Output (frequency f_Two)
Select to switch.

Now, the time t ₀ is the initial state, and the time t _0
1 , t ₂ , t ₃ are frequency switching timings, and LE
The timing when the reception level of one of the receivers input to V19 falls below the threshold level is shown.

Time t₀ At reception level a₁ , A_Two , B₁ ,
b_Two With LEV19, receiver 4₁ Reception level of
a_Two Is the maximum, so time t₁ Reception frequency is up to f₁ 
Receiver 3 set to₁ , 4₁ Is selected
Space diversity is performed between them. Time t₁ Select with
Receiver 4₁ Reception level a_Two Is threshold
Below the level, but a₁ , A_Two , B₁ , B_Two Reception of
Bell comparison at time t₁ Then reception level a₁ Is the best
Larger receiver 3₁ The frequency selection signal d is selected
The reception frequency is not changed and remains as it is. Time t_Two so
Receiver 3₁ Reception level a₁ Is below the threshold level
Around, at this time the reception level b₁ Because the maximum is the receiver
Three_Two Is selected and the frequency selection signal d is changed to level 0
And receive frequency f with SW17_Two Receiver set to
Three_Two , 4_Two The receivers are switched on and the space between them is reduced.
Perform iversity. Time t_Three Received selected
Machine 3 _Two Reception level b₁ Is below the threshold level
But at time t_Three At receiver 4_Two Reception level b_Two But
Since the frequency is the maximum, the frequency selection signal d remains at level 0.
Do not change the reception frequency.

As described above, by setting the level for determining the deterioration of the reception level to be slightly higher than the level at which the reception is poor, it is possible to perform space diversity while selecting a frequency with a good reception level. Further, since the reception voltage of all the receivers is constantly monitored, the best receiver is selected at the time of switching, and the reception frequency difference between the receivers does not occur, so that the space diversity can be performed. According to this method, space diversity and frequency diversity are effectively performed in the reception of a mobile station having a particularly high moving speed and a short frequency switching period, and the transmission quality of high-speed digital signals can be improved.

For the sake of simplicity, the case where the number of frequencies is 2 has been described above. However, even when the frequencies are 3 or more, the reception levels can be simultaneously compared by the same method. It can be easily understood by those skilled in the art that it is possible to select the reception frequency of the receiver that performs the space diversity.

[0017]

As described above, the diversity receiving method and apparatus according to the present invention is effective in frequency diversity and space diversity by using a circuit having a simple structure including a level judgment circuit, a voltage comparator and a switching circuit. It has a great effect on the improvement of the reception error rate when receiving a data transmission signal in a propagation path with severe fading. Especially, the receiving situation like the high-speed data transmission system for high-speed mobile communication using millimeter waves can be achieved. The effect fluctuates drastically and the effect is extremely large in a line with a short frequency switching period.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a receiving apparatus using a diversity receiving method of a high speed data transmission system for high speed mobile communication of the present invention.

FIG. 2 is a waveform example diagram illustrating an operation of the apparatus of FIG.

FIG. 3 is a block diagram showing a configuration of an example of a receiving apparatus using a conventional diversity receiving method.

[Explanation of symbols]

1, 2 Antenna 3, 4 Receiver 5, 6 High frequency amplifier 7, 8 Frequency converter 9, 10 Local oscillator 11, 12 Intermediate frequency amplifier 13, 14 Demodulation circuit 15, 16 AGC circuit 3 ₁ , 3 ₂ , 4 ₁ , 4 ₂ receiver 21 ₁ , 21 ₂ , 22 ₁ , 22 ₂ receiver 13 ₁ , 13 ₂ , 14 ₁ , 14 ₂ demodulation circuit 15 ₁ , 15 ₂ , 16 ₁ , 16 ₂ AGC circuit 17 switching circuit 18 voltage comparator 19 level determination circuit 30 control circuit 37 switching circuit 38 voltage comparator 39 level determination circuit

Claims (4)

[Claims] 1. At least two independent antennas for receiving the same radio signal modulated to at least two frequencies different from each other, and an individual unit having a reception frequency corresponding to each of the frequencies connected to each of the antennas. A first step of comparing the reception levels of all the receivers and selecting the receiver with the highest reception level, the diversity reception method of the high-speed data transmission system for high-speed mobile communication using the receiver of A second step of selecting the receiver having the highest reception level from among the receivers having the same reception frequency as the selected receiver having the highest reception level and outputting the receiver by the receiver, Of the receiver and all other receivers having the same reception frequency as the receiver have preset threshold values. A diversity receiving method in which the first step and the second step are executed again when the level becomes equal to or lower than the drive level value. 2. The diversity receiving method according to claim 1, wherein frequency diversity reception of the radio signal is performed in the first step, and space diversity reception of the radio signal is performed in the second step. 3. The diversity receiving method according to claim 2, wherein the frequency diversity reception is performed after demodulation of a received radio signal. 4. A diversity receiver for a high-speed data transmission system for high-speed mobile communication, comprising: at least two independent antennas for receiving the same radio signals modulated to at least two different frequencies, and The receivers that have the highest reception level are selected by comparing the reception levels of all the receivers with the individual receivers that have the reception frequencies corresponding to each of the above-mentioned frequencies, and select the receiver that has the highest reception level. Level determination that repeats the selection operation of the receiver having the largest reception level when the reception levels of the receiver and all other receivers having the same reception frequency as the receiver become less than or equal to a preset threshold level value. The circuit and one receiver with the highest reception level among receivers with the same reception frequency are Of the voltage comparator selected for each reception frequency of the receiver and one of the reception levels selected by the voltage comparator having the frequency of the receiver selected by the level determination circuit from the reception outputs of all the receivers. Diversity receiver consisting of a switching circuit that selects and switches the receiver of.