JP3885625B2 - Automatic reception gain control method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for automatic reception gain control of a time division duplex (TDD) type radio that handles burst waves, and a circuit for implementing the method.
[0002]
[Prior art]
A conventional automatic gain control (AGC) method for a TDD type radio that handles burst waves has been as follows.
[0003]
A) Continuously sample the received power of the burst wave.
B) The value of the received power level is determined based on the sampling result, and the comparison result with the standard received power level is immediately returned to the output level to the subsequent circuit (level amplification or suppression) (steady state).
C) Therefore, when fading, rainfall, etc. occur and the received power level decreases, the output level to the subsequent circuit also decreases, but the process returns to the steady state by the processing of A) and B).
D) If the received power level increases due to fading or reflected waves, the output level to the subsequent circuit also increases, but the output level to the subsequent circuit returns to the steady state by the processing of A) and B). .
[0004]
In the AGC circuit technology of the conventional TDD type radio, it is necessary to equip the radio with high-speed sampling and an immediate feedback AGC circuit in order to cope with an environment where the propagation state changes every moment such as mobile radio communication. It was.
[0005]
However, if an excessive level interference wave (burst wave from another radio) that cannot be distinguished from the desired radio wave is input to the radio, the level suppression operation to compensate the level of the burst type interference wave is AGC. When the received power level difference between the interference wave and the next desired burst wave is large, the required amount of operation of the AGC circuit increases and the AGC circuit cannot follow (the amplitude detection system of the radio becomes unstable) There was a risk. As a result, in the worst case, communication may be interrupted.
[0006]
In order to avoid this, an AGC circuit capable of operating a wider range at a high speed is required, and there is a problem in feasibility and cost.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide an automatic reception gain control method and apparatus that can operate satisfactorily even when an excessive level of interference wave is input.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is characterized in that a reception gain is automatically controlled in accordance with a difference between a level obtained by moving averaging the received power level of a radio and a preset value. Thus, the moving averaging process includes an A / D conversion step of converting the received power level into a digital signal, a step of holding the maximum value of the output of the A / D conversion in the maximum value extraction block that is a predetermined period , And determining an average received power level based on an average value of maximum values in a plurality of maximum value extraction blocks .
[0010]
Another feature of the present invention is a reception power level detection circuit that detects a reception power level of a radio, an A / D converter that converts an output of the detection circuit into a digital signal, and an output of the A / D converter A maximum value holding circuit that holds a maximum value for each maximum value extraction block that is a predetermined period of time, an averaging processing circuit that averages the maximum values in the plurality of maximum value extraction blocks and determines an average received power level, and A reception power level determination circuit for determining a difference between the average reception power level and a preset value, and an automatic reception gain control device for controlling the gain of the variable amplifier according to the difference.
[0011]
According to the present invention, the AGC circuit samples the received power level at regular time intervals. The AGC circuit determines and extracts the maximum value within a certain range (maximum value extraction block) for the sampled received power level group, and then simply moves the maximum value between multiple maximum value extraction blocks (averaging window). The average method (moving average processing) is applied, and the operating range of the AGC circuit is determined by calculating the difference from the standard received power level (which has been set in advance).
[0012]
If the present invention is used, even if a high-level burst-type interference wave is received, the determination received power level is smoothed by the simple moving average method (moving average processing). This is less than the case where the present invention is not applied.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the operating principle of the algorithm of the present invention.
[0014]
The input (a) from the radio is input to the AGC circuit through the detection circuit (b). Sampling is always performed on the detection output at regular time intervals (c), and the maximum hold (MAX HOLD) type processing (d) is performed on the sampling result (received power level). The execution result of the MAX HOLD type process is extracted at the end of the maximum value extraction block and stored in the memory. Apply the simple average method (moving average processing) to multiple maximum values (received power level) accumulated in a fixed number of maximum value extraction block (averaged window) to determine the average received power level ( f). The difference between the average received power level and the standard received power level (which is set in advance) is calculated to determine the operation amount of the AGC circuit.
[0015]
In the radio input (a) of FIG. 1, 10, 11, 12, and 13 indicate desired TDM bursts, and 10a, 11a, and 12a indicate interference wave inputs.
[0016]
The operations (1) to (6) in FIG. 1 are as follows.
[0017]
(1): The maximum value in the block increases due to the input of interference waves.
(2): The maximum value in the block increases due to the desired TDM burst.
(3): The maximum value in the block is further increased by the input of a high level interference wave.
{Circle over (4)} A desired TDM burst is input, but the maximum value does not increase because the level is lower than the input level of the interference wave in {circle over (3)}.
(5): The maximum value is read at the end of the block, stored in the memory, and then erased.
{Circle over (6)} The accumulated maximum value is subjected to the simple average method (moving average processing) in the averaging window to determine the average received power level. After that, the standard received power level and the difference are calculated and set as the operation amount of the AGC circuit.
[0018]
FIG. 2 shows an example of moving average processing using the algorithm of the present invention. The TDM frame length is 1.024 msec, the sampling interval is 1 μsec, the maximum value extraction block length is 2 msec, and moving average processing is performed for every 10 maximum value extraction blocks. That is, for example, in the case of “AVR_1” in the figure, the moving average processing simply averages from “MAX_1” to “MAX_10”, and in the case of “AVR_2”, it simply averages from “MAX_2” to “MAX_11”. . The radio unit (slave station) receives a desired wave in the range of -48 to -50 dBm during downlink burst reception, and receives radio waves in the range of -55 to -70 dBm during uplink burst transmission time. It is assumed that there are about three interference wave inputs (in the range of −35 to −40 dBm) per averaging window.
[0019]
In this figure, there is a maximum difference of 15 dB between the reception level of the desired wave and the reception level of the interference wave, but the relative variation of the averaged result by the algorithm of the present invention (the averaged result between adjacent averaging windows) The difference is 1 dB. That is, in the conventional technique (immediate feedback type), the AGC circuit requires a 15 dB operation amount at 1 μsec which is one sampling interval. However, by using the algorithm of the present invention, a 1 dB operation amount is required in 2 msec. It can be seen that the amount of operation required for the AGC circuit when receiving an excessive level of burst type interference wave is reduced.
[0020]
FIG. 3 is an example of a circuit that implements the algorithm of the present invention, taking as an example a slave station of a point-to-multipoint type radio system employing a time division multiplex communication (TDM) system. 1 is a block diagram illustrating an embodiment of the present invention.
[0021]
The radio device 10 has a transmission system 20 and a reception system 30.
[0022]
The input signal is applied to the transmission system circuit 20 via the hybrid circuit 40, amplified by the amplifiers (21, 23), and frequency-converted by the mixer 22. The output of the transmission system circuit 20 is applied to the antenna 46 via the transmission / reception changeover switch 44 and emitted into the air.
[0023]
The radio wave received by the antenna 46 is applied to the reception system circuit 30 via the transmission / reception changeover switch 44. The reception system circuit 30 includes a low noise amplifier (LNA) 31, a mixer 32, and an amplifier 33. A reception signal frequency-converted by the mixer 32 is extracted as an output signal through the hybrid circuit 40. Switching between the transmission system and the reception system is performed by switching between the transmission / reception selector switch 44 and the local oscillator / switching unit 42 by a switching control signal.
[0024]
The reception power level detection circuit 51 detects a power level received through an antenna, an LNA (low noise amplifier) 31 or the like.
[0025]
The output from the received power level detection circuit 51 is sampled (quantized) through an analog-to-digital converter (A / D converter) 52 and output to a maximum value holding (MAX HOLD) circuit 53.
[0026]
In the MAX HOLD type processing circuit 53, the maximum value is extracted at the end of the maximum value extraction block (a plurality of predetermined TDM burst units) and is output to the averaging processing circuit 54.
[0027]
The maximum value input to the averaging processing circuit 54 is stored in a memory, and a simple average method (moving average processing) is performed on the stored maximum value in an averaging window unit composed of a plurality of predetermined maximum value extraction blocks. When applied and the average received power level is determined, it is output to the received power level determination circuit 55. After the average received power level is determined / output, the maximum value is reset / erased.
[0028]
The reception power level determination circuit 55 stores a preset standard reception power level, and determines a difference from the input signal (average reception power level) from the averaging processing circuit 54 (0, positive or negative). The difference is output to the AGC control circuit 56.
[0029]
The AGC control circuit 56 controls the variable amplifier for received power, and controls the amplification amount of the variable amplifier 33 based on the input signal (difference) from the received power level determination circuit 55.
[0030]
Thus, the present invention can be implemented with a very simple circuit.
[0031]
【The invention's effect】
As described above, by applying the present invention to the AGC operation, even when a burst type interference wave is input, the difference in the determination reception power level on the time axis is reduced, and the AGC circuit within the unit time is reduced. There is an advantage that the required operation amount is small (the operation should be performed within a time range in which the simple average method (moving average processing) is applied).
[0032]
In fixed wireless communication systems, a high-speed AGC circuit is not necessary because the propagation path environment is very stable. However, even if a relatively low-speed AGC circuit is used, excessive levels of burst-type interference are required. If there is a wave input, the amount of operation required for the AGC circuit will increase. However, if the algorithm of the present invention is applied, it is possible to reduce the influence of an excessive level of burst type interference wave on the operation amount of the AGC circuit, and as a result, it is possible to apply an AGC circuit having a relatively small operation amount. Therefore, there is a great advantage in introduction to the fixed wireless communication system.
[Brief description of the drawings]
FIG. 1 is a diagram showing an operation principle of the present invention.
FIG. 2A is an example of moving average processing using the present invention.
FIG. 2B is an example of moving average processing using the present invention.
FIG. 3 is a block diagram showing an embodiment of the present invention.
[Explanation of symbols]
10 radio
20 Transmission system
30 reception system
33 Variable amplifier
51 Received power level detection circuit
52 A / D converter
53 MAX HOLD circuit
54 Averaging circuit
55 Received power level judgment circuit
56 AGC control circuit

Claims (2)

A method of automatically controlling reception gain according to a difference between a level obtained by moving average processing of a reception power level of a radio and a preset value,
A step wherein the moving averaging process, to hold the A / D conversion step of converting the received power level into a digital signal, the maximum value of the output of the A / D conversion at the maximum value extraction block which is a predetermined time period, a plurality And determining an average received power level based on an average value of the maximum values in the maximum value extraction block of the automatic reception gain control method. A reception power level detection circuit for detecting the reception power level of the radio, and
An A / D converter for converting the output of the detection circuit into a digital signal;
A maximum value holding circuit for holding a maximum value for each maximum value extraction block that is a predetermined period of the output of the A / D converter;
An averaging processing circuit that averages the maximum values in a plurality of maximum value extraction blocks and determines an average received power level;
A received power level determination circuit for determining a difference between the average received power level and a preset value;
An automatic reception gain control apparatus for controlling a gain of a variable amplifier according to the difference.

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