KR20110087091A - Automatic Gain Control Method and Apparatus Used in Concubine Spread Spectrum Systems - Google Patents

Abstract

PURPOSE: An automatic gain adjusting device using a chirp spread spectrum system is provided to adaptive adjust the length of time interval which estimated an average power of an output signal. CONSTITUTION: A gain amplification unit(110) amplifies a gain of an input signal. A first power estimation unit(121) estimate average power of an input signal during the time interval corresponding to the first window. A second power estimating unit(122) estimates average power of an input signal during time interval corresponding to the second window. A packet detector(130) detects the number of input full chirp signals. A comparison unit(150) generates a control signal through comparing between average power and reference power of the estimated input signal.

Description

METHOD FOR AUTOMATIC GAIN CONTROL USING CHIRP SPREAD SPECTRUM SYSTEM AND AUTOMATIC GAIN CONTROLLER}

An automatic gain adjustment method and apparatus are disclosed. In particular, in a chirp spread spectrum system, an automatic gain adjustment method and apparatus for controlling the gain of a signal in consideration of both adaptation time and stability are disclosed.

In general, an automatic gain controller (AGC) is a device that adjusts the level of the output signal to a level of a predetermined reference signal regardless of the level of the input signal. Such an automatic gain adjusting device is used in a control field, a communication field, and the like.

The existing automatic gain control apparatus estimates the average power of the output signal for a predetermined period, and adjusts the level of the input signal by comparing the estimated average power with the preset reference power.

At this time, when the length of the time interval for estimating the average power of the output signal is long, it is difficult for the output signal to change rapidly with the level change of the input signal. In addition, when the length of the time interval for estimating the average power of the output signal is short, if the signal disappears or suddenly a large signal is input during the time interval for estimating the average power, the output signal may be unstable.

Accordingly, there is a need for a technique capable of stably outputting an output signal by quickly adapting to a change in the level of an input signal and stably outputting an output signal even when a sudden signal change occurs during a time interval for estimating average power.

The present invention adjusts the length of the time interval for estimating the average power of the output signal adaptively, the automatic gain adjustment method that can output the output signal stably even in the event of a sudden change in the signal while rapidly adapting to changes in the input signal And an apparatus.

The automatic gain control method includes amplifying a gain of a full chirp signal composed of a plurality of sub-chirp signals, and calculating a time interval for estimating an average power of the full chirp signal. Estimating the average power of the amplified signal during the time period set as the first window, generating a control signal by comparing the estimated average power with a predetermined reference power, and generating the control signal. Adjusting a gain of a next full chirp signal based on the first step; when two or more full chirp signals are input, changing the time interval to a second window; and adjusting the gain of the amplified signal during the time interval changed to the second window. Estimating an average power, comparing the estimated average power with a predetermined reference power to generate a control signal, and based on the control signal, the next pool Adjusting the gain of the chirp signal.

In addition, the automatic gain control device, a gain amplifier for amplifying the gain of the full chirp signal consisting of a plurality of sub-chirp signals, a time interval for estimating the average power of the full chirp signal Is a first window, the first power estimator for estimating the average power of the amplified signal during the time interval set as the first window; A second power estimator configured to set a window and estimate the average power of the amplified signal during the time period changed to the second window, and compare the estimated average power with a predetermined reference power to generate a control signal It may include wealth. Then, the gain amplifier may adjust the gain of the next pooled signal based on the control signal.

In addition, a packet search unit for determining the number of input pooled signals by performing matched filtering on each of the plurality of sub-cue signals, and when two or more pooled signals are input, The method may further include a switch for changing from the first window to the second window.

The automatic gain adjustment method and apparatus can adaptively adjust the length of the time interval for estimating the average power of the output signal, thereby quickly adapting to changes in the input signal, and stably outputting the output signal even in the event of sudden changes in the signal. have.

1 is a diagram illustrating a configuration of an automatic gain adjusting device.
2 is a diagram illustrating a full chirp signal composed of a plurality of sub-chirp signals.
3 is a flowchart provided to explain a method for automatically adjusting gain of a chirp signal.
4 is a diagram showing a simulation result of the performance between the conventional automatic gain control device (AGC) and the automatic gain control device.
5 is an experimental result showing the waveform of the CSS signal measured using an oscilloscope.

Hereinafter, with reference to the accompanying drawings, it will be described an embodiment of the present invention.

1 is a diagram illustrating a configuration of an automatic gain adjusting device.

Referring to FIG. 1, the automatic gain control apparatus 100 may include a gain amplifier 110, a power estimator 120, a packet searcher 130, a switch 140, and a comparator 150. have.

The gain amplifier 110 may amplify the gain of the _input signal V _input . In this case, the gain amplifier 110 may adjust and output the gain of the input signal based on the control signal input from the comparator 140 to be described later. For example, a VGA (Variable Gain Amplifier) may be used as the gain amplifier 110.

In this case, the gain amplifier 110 may continuously input a full chirp signal composed of a plurality of sub-chirp signals. For example, as shown in FIG. 2, the full chirp signal may be composed of four or more sub-chirp signals, and the chirp signals may be configured as a symbol. Here, a guard time may exist between the full chirp signal and the full chirp signal.

The power estimator 120 may include first and second power estimators 121 and 122.

The first power estimator 121 may estimate an average power of a signal input during a time period corresponding to the first window. Here, the first window is a predetermined time interval for estimating the average power of the input signal, and the size of the first window may be smaller than the second window.

For example, when a full chirp signal consisting of four sub-chirp signals is input, the first window may be set to a sub-chirp duration of one sub-chirp signal.

In this case, 1.1875 μsec may be used as the duration of one sub-chipping signal. In this way, by setting the time interval as short as the duration of the subcue signal to estimate the average power of the input full-cub signal, the output signal (V _output ) also changes rapidly and _outputs even if the magnitude of the input signal changes rapidly. Can be. That is, it is possible to quickly adjust the output of the signal by quickly adapting to the change in the magnitude of the signal input to the automatic gain control device.

The second power estimator 122 may estimate an average power of a signal input during a time period corresponding to the second window. Here, the second window may be set larger in size than the first window.

In one example, the second window may be set to the full chirp duration of the full chirp signal. In this case, 6 μsec may be used as the duration T _chirp of the full chirp signal. As such, by estimating the average power of the pull-in signal that is input by setting the time period to be large as the duration of the pull-in signal, the output signal (V _output ) is reduced even if the signal disappears or suddenly a large signal is input during the time period. It can be output stably.

The packet detector 130 may match the filtered plurality of sub-chip signals, respectively, and determine the number of input full-chp signals. In this case, when the number of full chirp signals is less than two, the switch 140 may switch to the first power estimator 121 so that the time interval is set as the first window.

In addition, when the determined number of full chirp signals is two or more, the switch 140 may switch to the second power estimator 122 so that the time interval is set as the second window. That is, when the determined number of full chirp signals is two or more, the signal interval for estimating the average power may be changed from the first window to the second window.

The comparator 150 may generate a control signal by comparing the estimated average power of the input signal with the reference power V _ref . Here, the reference power may be preset to a value for maintaining a constant level of the signal (V _output ) _output from the automatic gain control device.

For example, the comparator 150 may calculate a difference between the estimated average power and the reference power, and generate the calculated difference V _err as a control signal. In addition, the comparator 150 may transmit the generated control signal to the gain amplifier 110.

Then, the gain amplifier 110 may reduce or amplify the gain of the next full splice signal input based on the control signal. For example, when the difference (V _err ) received from the comparator 150 is negative, the gain amplifier 110 may reduce the gain of the input full chirped signal by the absolute value (| V _err |) of the difference and output the difference. Can be.

In addition, when the difference V _err transmitted from the comparator 150 is a positive number, the gain amplifier 110 may amplify and output the gain of the full chirped signal by the difference value V _err . Here, the gain-adjusted full chirp signal may be the next full chirp signal inputted continuously after the full chirp signal used in power estimation.

3 is a flowchart provided to explain a method for automatically adjusting gain of a chirp signal.

Referring to FIG. 3, the gain amplification unit 110 may amplify the gain of the input full chirp signal (S310).

Subsequently, when the number of input full chirp signals is not two or more (S320: NO), the first power estimator 121 may set the time interval as the first window (S330). That is, when the number of full chirp signals is less than two, the time interval may be set as the first window.

In one example, the first window may be set to the duration of the sub-cue signal. In this case, the number of full chirp signals input by matching filtering the plurality of sub chirp signals may be determined.

Then, the first power estimator 121 may estimate the average power of the amplified signal during the time period set as the first window (S340).

In addition, the comparator 150 may generate a control signal based on the estimated average power (S350).

For example, the comparator 150 may generate a control signal as a difference V _err between the estimated average power and the predetermined reference power.

Then, the gain amplification unit 110 may adjust the gain of the next pooled signal based on the control signal (S360).

For example, when the difference between the average power and the reference power (V _err ) is negative, the gain amplifier 110 may reduce the gain of the next full chirp signal by the absolute value of the difference and output.

At this time, when the difference between the average power and the reference power (V _err ) is positive, the gain amplifier 110 may amplify and output the gain of the next pooled signal by the difference value.

Meanwhile, when the number of full chirp signals is two or more in operation S320 (S320: YES), the second power estimator 122 may set a time interval as a second window (S370).

That is, when the number of full chirp signals is two or more, the time interval may be changed and set from the first window to the second window through switching. Here, the second window may be set larger than the size of the first window. In one example, the second window may be set to the duration of the pull-in signal.

Subsequently, the steps S340 to S360 may be repeated.

That is, the second power estimator 122 may estimate the power of the signal amplified in step S310 during the time period set as the second window. Then, based on the control signal generated by comparing the estimated power and the reference power, the gain amplifier 110 may adjust the gain of the next pooled signal to increase or decrease.

4 is a diagram showing a simulation result of the performance between the conventional automatic gain control device (AGC) and the automatic gain control device. 4 is a simulation result when an additive white Gaussian noise (AWGN) channel model is applied.

In this case, the chirp signal is generated by the chirp-shift-keying generator, the chirp rate (μ) is 2π × 7.3158 × 10 ¹² rad / sec ² and the sampling rate can be 32 MHz. In addition, each of the sub-chirp signals is composed of 38 samples, the full chirp signal is composed of 192 samples each, and may have a guard time between the full chirp signals.

According to (a) of FIG. 4, when the time interval is set to be short as in the first window, the conventional AGC rapidly decreases the gain at the start point of the preamble. It can be seen that there are many tines where the signal suddenly fluctuates during the guard time.

In addition, according to FIG. 4B, when the time interval is set to be large as in the second window, the conventional AGC has a smooth curve of gain during the guard time, but preambles. It can be seen that the adaptation time becomes longer at the start point of the preamble.

On the other hand, according to (c) of FIG. 4, when the time interval is set differently according to the number of full-cub signals, the gain is rapidly decreased at the start point of the preamble, so that the adaptation time is short and the tine region during the guard time. It can be seen that this less stability (stability) than the conventional AGC.

In the above description, when two or more full chirp signals are input, the time interval is set as the second window. However, this corresponds to an embodiment, and as illustrated in FIG. 5, when eight or more full chirp signals are input, If the time interval is set to the second window and the full chirp signal is less than eight, the time interval may be set to the first window. That is, eight full chirp signals can be packetized into one.

In addition, although the above description has been made of changing the time section from the first window to the second window, this is an embodiment, and the time section may be changed from the second window to the first window.

For example, when an interference signal is input or a communication failure occurs during the time period, the time period may be changed from the second window to the first window.

In addition, the automatic gain adjustment method may be implemented using a Verilog hardware description language.

In addition, an automatic gain control device can be implemented using the Altera Stratix II EP2S180 FPGA board and the MAX2830 RF board. In this case, the automatic gain control apparatus may control the gain amplifier in the RF substrate using a serial data transfer line.

In addition, the communication apparatus, the terminal apparatus, and the interference alignment method according to the embodiments of the present invention include a computer readable medium including program instructions for performing various computer-implemented operations. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The media may be program instructions that are specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

Claims (10)

Amplifying the gain of a full chirp signal consisting of a plurality of sub-chirp signals;
Setting a time interval for estimating average power of the pooled signal as a first window;
Estimating an average power of the amplified signal during the time interval set as the first window;
Generating a control signal by comparing the estimated average power with a preset reference power;
Adjusting a gain of a next pooled signal based on the control signal;
Changing the time interval to a second window when more than one full chirp signal is input;
Estimating an average power of the amplified signal during the time period changed to the second window;
Generating a control signal by comparing the estimated average power with a preset reference power; And
Adjusting a gain of the next full chirp signal based on the control signal
Automatic gain adjustment method comprising a. The method of claim 1,
And the second window has a larger size than the first window. The method of claim 1,
And the first window is set to a sub-chirp duration of the sub-chip signal. The method of claim 1,
And the second window is set to a full chirp duration of the full chirp signal. The method of claim 1,
Changing to the second window,
Determining the number of input full chirped signals by performing matched filtering on each of the plurality of sub-chirped signals;
Including,
And when the determined number of full chirp signals is two or more, changing the time interval to a second window. A gain amplifier for amplifying a gain of a full chirp signal composed of a plurality of sub-chirp signals;
A first power estimator configured to set a time interval for estimating the average power of the full chirp signal as a first window and estimate the average power of the amplified signal during the time interval set to the first window;
A second power estimator configured to set the time interval as a second window and estimate an average power of the amplified signal during the time interval changed to the second window when two or more full chirp signals are input; And
A comparator for generating a control signal by comparing the estimated average power with a predetermined reference power
Including,
The gain amplifier unit,
And adjusting the gain of the next full chirp signal based on the control signal. The method of claim 6,
A packet search unit configured to perform a matched filtering on each of the plurality of sub-chirp signals to determine the number of input full chirp signals; And
A switch for changing the time interval from the first window to the second window when two or more full chirp signals are input;
Automatic gain control device further comprising. The method of claim 6,
And the first window is set to a sub-chirp duration of the sub-chip signal. The method of claim 6,
And the second window is set to a full chirp duration of the full chirp signal. The method of claim 6,
The second window has a larger size than the first window,
And said full chirp signal comprises four or more sub-chirp signals.

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