JPH10200353A - Burst agc circuit and burst agc control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a burst AGC circuit and a burst AGC control method for reducing the power consumption of a variable gain amplifier in a state that a burst signal is not present, and operating satisfactory AGC control from the first part of the burst signal. SOLUTION: A burst presence or absence discriminating part 10 outputs a reception discrimination signal (L level) 10a for designating an AGC operation mode in a burst signal presence period (burst receiving timing), outputs the reception discrimination signal (H level) 10a for designating an AGC non- operation mode in a non-receiving(non-signal) period, and moreover, outputs the reception discrimination signal (L level) 10a for designating the AGC operation mode at a point of time a little before the arrival of the next burst receiving timing. A gain setting part 7 in an AGC control part 4 sets the gain of a variable gain amplifier 3 based on reception signal intensity detected by a reception level detector 5 in the AGC operation mode, and sets the gain of the variable gain amplifier 3 to the minimum value in the AGC non-operation mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burst AGC circuit and a burst AGC control method for automatically adjusting the amplification gain of a burst signal (intermittent signal) and outputting a burst signal in a predetermined level range. The present invention relates to a burst AGC circuit and a burst AGC control method in which the amplification gain is fixed to a small value in a period in which no AGC exists.

[0002]

2. Description of the Related Art An AGC (Automatic Gain Control) circuit is a circuit capable of amplifying a received signal having a level fluctuation to a fixed level and outputting the amplified signal. The AGC circuit is important in the configuration of a receiver in digital radio communication or the like. is there. The burst signal is a signal of only a necessary section on the time axis for effective use of radio waves and electric power.

FIG. 8 is a block diagram of a conventional AGC circuit. A conventional AGC circuit 101 includes a distributor 102 for distributing a received burst signal 101a, and a distributor 102.
Variable gain that amplifies one of the burst signals 102a distributed by the above with an amplification gain specified by a gain control signal 103b supplied to a gain control input terminal 103a and outputs a burst signal in a predetermined level range as an AGC output signal 103c. A variable gain amplifier 1 based on the amplifier 103 and the other burst signal 102b distributed by the distributor 102;
03, a gain control signal 103b for controlling the amplification gain
And an AGC control unit 104 for generating the same.

The AGC control unit 104 controls the burst signal 10
2b, a signal level detector 105 for detecting a signal level and outputting a reception intensity signal 105a;
A / D converter 106 for converting a into reception intensity data 106a corresponding to reception intensity, gain setting section 107 for outputting gain control data 107a set in advance corresponding to reception intensity data 106a, and gain control data 107a And a low-pass filter (low-pass filter: LPF) 109 for smoothing the analog signal 108a with a predetermined time constant and outputting a gain control signal 103b. I have.

The signal level detector 105 is supplied from a rectifier circuit for rectifying the burst signal 102b and a logarithmic amplifier (log amplifier) for logarithmically amplifying the rectified output.
It outputs an SSI (Received Signal Strength Indicator) signal. Amplification gain setting section 107
Is provided with a conversion table for receiving intensity data 106a and gain control data 107a configured using a ROM (Read Only Memory).

FIG. 9 is a timing chart showing the operation of a conventional AGC circuit. (A) shows the presence or absence of a burst signal. (B) shows a gain control signal 103b output from the low-pass filter (LPF) 109. (C) is AGC
5 shows the envelope of the output signal 103c.

In a state where the burst signal 101a is present (signal reception period), a reception intensity signal 105a corresponding to the reception level of the burst signal 101a is output from the signal level detector 105, and the A / D converter 106 corresponds to the reception level. Since the received reception data 106a is output, the gain control data 1 corresponding to the reception level is output from the amplification gain setting section 107.
07a is output, and the D / A converter 108 outputs an analog signal 108a corresponding to the gain control data 107a. This analog signal 108a is
And supplied to the variable gain amplifier 103 as a gain control signal 103b. As a result, the amplification gain of the variable gain amplifier 103 is set according to the reception level, and the burst signal amplified to a predetermined output level is output as the AGC output signal 103c.

[0008]

SUMMARY OF THE INVENTION Burst signal 101a
When there is no signal (no signal period), the signal level detector 10
5 has a low level corresponding to the level of a noise signal or the like, and the A / D converter 1
Also, the reception strength data 106a output from 06 becomes a small value. When the level of the input signal is low, amplification gain setting section 107 outputs gain control data 107a designating a large amplification gain. Therefore, D / A converter 108 outputs high-voltage analog signal 108a, and LPF 109
, The voltage of the gain control signal 103b output via the controller becomes high, and a state in which the maximum gain is almost specified. For this reason,
In a conventional AGC circuit, the amplification gain of the variable gain amplifier 103 is maximized in a no-signal state, and a so-called full noise output state is set. In this full noise output state, the power consumption of the variable gain amplifier 103 increases, so that power is wasted.

[0009] Further, from a state where there is no burst signal 101a (no signal period) to a state where a burst signal is received (signal period).
, The gain control data 107 a corresponding to the reception strength of the burst signal is output from the amplification gain setting unit 107, and the analog signal 108 a having the voltage corresponding thereto is output from the D / A converter 108. Since the gain control signal 103b gradually changes due to the constant delay, a delay occurs until the amplification gain of the variable gain amplifier 103 is set to a gain corresponding to the reception strength of the burst signal. For this reason, as shown in FIG. 9C, a signal having a level higher than the standard level is output at the start of receiving the burst signal.

An excessively high level AG is output from the AGC circuit 101.
When the C output signal 103c is output, it causes erroneous synchronization or inability to synchronize, and places a heavy burden on the synchronization system. Also, the AGC output signal 103 having an excessive level
There is a possibility that c may destroy a circuit element at a later stage.

Japanese Unexamined Patent Publication No. 59-37741 discloses a burst detection circuit for detecting the presence or absence of a burst, a sample and hold circuit for holding a control voltage when a burst is present, and the gain of a variable gain amplifier when there is no signal. An automatic gain control circuit is described which prevents the occurrence of high-level noise by maintaining the gain when present.

However, the automatic gain control circuit proposed in the above-mentioned publication requires a sample-and-hold circuit, so that the circuit configuration is increased and power consumption is increased by the increase in the circuit configuration. Further, in the absence of a burst signal, noise and the like are amplified with the gain set when the burst signal is present, so that the power consumption of the variable gain amplifier increases by the amount of amplification.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a burst AGC circuit and a burst AGC circuit capable of reducing power consumption in the absence of a burst signal and performing AGC control on the burst signal. An object of the present invention is to provide an AGC control method.

[0014]

In order to solve the above-mentioned problems, a burst AGC circuit and a burst AG according to the present invention are provided.
The C control method includes an AGC operation mode for controlling the amplification gain of a variable gain amplifier for amplifying a burst signal according to the signal level of the burst signal, and an AGC non-operation for fixing the amplification gain of the variable gain amplifier to a preset small value. The mode is switched in synchronization with the presence or absence of a burst signal.

While the burst signal is being received, the AGC operation mode is set. When the burst signal is not received, the mode is switched to the AGC non-operation mode, and the AGC operation mode is set a predetermined time before the arrival timing of the next burst signal. It is desirable to switch to

In the burst AGC circuit and the burst AGC control method according to the present invention, the amplification gain of the variable gain amplifier for amplifying the burst signal is set to a small value in the absence of a burst signal. Thus, it is possible to prevent a full noise output state in a no-signal state. Therefore, it is possible to prevent the power consumption of the variable gain amplifier from increasing due to the full noise output.

Further, since the state in which the amplification gain of the variable gain amplifier is set to a small value is switched to the AGC operation mode, an excessive level signal is not output from the variable gain amplifier at the time of switching to the AGC operation mode. .

Further, by switching to the AGC operation mode a predetermined time before the arrival timing of the next burst signal, the burst signal can be reliably AGC amplified. Considering the response characteristics of the variable gain amplifier at the time of changing the gain and the delay time (time constant) of the low-pass filter when the gain control signal is supplied to the variable gain amplifier via the low-pass filter, the AGC is performed. By setting the timing of switching to the operation mode, it is possible to amplify the burst signal with a substantially appropriate amplification gain from the first part.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of a burst AGC circuit according to the present invention. The burst AGC circuit 1 according to the present invention includes a distributor 2, a variable gain amplifier 3, an AGC control unit 4, and a burst presence / absence determination unit 10. The AGC control unit 4 includes a reception level detector 5, an A / D converter 6, a gain setting unit 7, a D / A converter 8, and a low-pass filter (LPF: low-pass filter) 9.

The received burst signal 1 a is supplied to a variable gain amplifier 3 via a distributor 2 and to a reception level detector 5. The variable gain amplifier 3 can vary the amplification gain by a gain control signal 3b supplied to a gain control input terminal 3a. The burst signal supplied via the distributor 2 is amplified with an amplification gain specified by the AGC control unit 4, and is output as an AGC output signal 3c.

The reception level detector 5 detects the signal level of the burst signal supplied via the distributor 2, and outputs a reception intensity signal 5a corresponding to the signal level. The signal level detector 5 includes a rectifier circuit for rectifying the burst signal, and a logarithmic amplifier (log amplifier) for logarithmically amplifying the rectified output of the rectifier circuit. The signal level detector 5 outputs a so-called RSSI signal that is logarithmically proportional to the level of the received signal as a received intensity signal 5a. Since the reception level detector 5 includes a logarithmic amplifier (log amplifier), it can output a reception intensity signal 5a corresponding to the reception level over a wide range of the reception level. The reception intensity signal 5a is A
/ D converter 6.

The A / D converter 6 converts the reception intensity signal 5a into a digital reception intensity signal, and outputs the converted digital reception intensity signal as reception intensity data 6a. The reception intensity data 6a is supplied to the gain setting unit 7.

When the AGC operation mode is set based on reception determination signal 10a, gain setting section 7 outputs gain control data 7a set in advance corresponding to reception intensity data 6a. The gain setting unit 7 receives the reception determination signal 10a.
When the AGC non-operation mode is set on the basis of the above, the gain control data 7a specifying the amplification gain of a small value set in advance is output.

FIG. 2 is a block diagram showing a specific example of the gain setting section. The gain setting unit 7 shown in FIG.
It is configured using. The address input of the ROM 7A is
The number of bits of the gain control data 7a is increased by at least one bit. Then, for example, the reception determination signal 10a is supplied to the most significant bit of the address input. Here, the reception determination signal 10a indicates the AGC operation mode when the logic level is L, and the AGC operation mode when the logic level is H.
The non-operation mode shall be specified. Most significant bit is L
The gain control data 7a set in advance corresponding to the reception intensity data 6a is stored in the address area. That is, in the AGC operation mode, the reception intensity data 6a is used as an address, and the gain control data at the reception intensity is output from the data output terminal of the ROM 7A. For example, gain control data for setting the minimum amplification gain is stored in the address area where the most significant bit is H. That is, in the AGC non-operation mode, for example, the gain control data for setting the minimum amplification gain is always output regardless of the reception intensity data 6a.

FIG. 3 is a block diagram showing another specific example of the gain setting unit. A gain setting unit 7 shown in FIG. 3 includes a ROM 7B storing gain control data when the reception intensity data 6a is used as an address and a non-AGC gain control data setting for supplying the gain control data when the AGC is not operating. It comprises a unit 7C and a data selection circuit 7D. The gain control data when the AGC is not operating specifies the minimum amplification gain of the variable gain amplifier 3 or a preset small amplification gain. When the reception determination signal 10a is at the L level (AGC operation), the data selection circuit 7D
The gain control data corresponding to the reception intensity output from the ROM 7B is selected and output. When the reception determination signal 10a is at the H level (AGC not operating), the data selection circuit 7D
Non-A supplied from non-AGC gain control data setting section 7C
GC gain control data is selected and output. With such a configuration, the storage capacity of the ROM can be made the same as the conventional one.

FIG. 4 is a block diagram showing still another specific example of the gain setting section. The gain setting unit 7 shown in FIG.
It comprises a ROM 7B storing gain control data at the reception intensity when the reception intensity data 6a is used as an address, and a multiplier 7E. The multiplier 7E outputs R when the reception determination signal 10a specifies the AGC operation mode.
Each bit of the gain control data output from the OM 7B is multiplied by 1, and the multiplication result is output as the gain control data 7a. That is, the multiplier 7E receives the reception determination signal 1
0a designates the AGC operation mode, the ROM
The gain control data output from 7B is directly output as gain control data 7a. The multiplier 7E outputs R when the reception determination signal 10a specifies the AGC non-operation mode.
Each bit of the gain control data output from the OM 7B is multiplied by 0, and the multiplication result is output as the gain control data 7a. That is, the multiplier 7E receives the reception determination signal 1
When 0a designates the AGC non-operation mode, the gain control data 7a in which all bits become 0 is output. Thus, the minimum gain is designated in the AGC non-operation mode.

Note that a circuit section other than the gain setting section 7 shown in FIG. 1 may perform gain switching between AGC operation and AGC non-operation. For example, in the AGC non-operation mode, the A / D conversion operation of the A / D converter 6 shown in FIG. 1 is stopped, and the output side of the A / D converter 6 is pulled up or down to set the gain. When all bits of the reception intensity data 6a are H or L, the unit 7
You may make it output the gain setting data at the time of GC non-operation. With such a configuration, the power consumption of the A / D converter 6 in the AGC non-operation state can be reduced.

As shown in FIG. 1, the gain control data 7a output from the gain setting section 7 is supplied to a D / A converter 8. The D / A converter 8 outputs an analog signal (voltage signal) 8a corresponding to the gain control data 7a. The analog signal (voltage signal) 8 a is supplied to the low-pass filter 9.

The low-pass filter 9 smoothes the analog signal (voltage signal) 8a with a preset time constant, and outputs the smoothed analog signal (voltage signal) as a gain control signal 3b. The gain control signal 3b is supplied to a gain control input terminal 3a of the variable gain amplifier 3.

The variable gain amplifier 3 has a gain control input terminal 3
a is not supplied with the gain control signal 3b, and
When the voltage of the gain control signal 3b is lower than a preset threshold voltage, the amplification gain is set to the minimum gain, and when the AGC is not operating, the D / A conversion operation of the D / A converter 8 is performed. Stop and analog signal (voltage signal)
The output of 8a may be stopped. Thereby, the power consumption of the D / A converter 8 in the AGC non-operation state can be reduced. Note that the conversion operation of the A / D converter 6 may be stopped at the same time.

The variable gain amplifier 3 has a gain control input terminal 3
a is not supplied with the gain control signal 3b, and
When the voltage of the gain control signal 3b is lower than a preset threshold voltage, the amplification gain is set to the minimum gain, and the output side of the low-pass filter 9 and the gain control input terminal of the variable gain amplifier 3 are set. A cutoff switch circuit may be provided between the control circuit 3a and the gain control signal 3b when the AGC is not operating. Further, instead of cutting off the supply of the gain control signal 3b, a switch circuit or a clamp circuit for grounding the output of the low-pass filter 9 with low impedance is provided. May be prevented from being supplied.

The variable gain amplifier 3 has a built-in D / A conversion function to set the amplification gain based on the gain control data. For example, the resistance value of a feedback resistor or an input resistor can be varied, or the variable gain amplifier 3 can be set based on the gain control data. The variable gain amplifier 3 is configured so that the amplification gain can be changed based on the digital signal by changing the attenuation amount of the attenuator, and the gain control data 7a output from the gain setting unit 7 is digitally controlled. May be directly supplied to the variable gain amplifier 3.

The burst presence / absence determination section 10 supplies a reception determination signal 10a for designating the AGC operation mode and the AGC non-operation mode to the gain setting section 7 and the like based on the presence / absence of the burst signal. In other words, the burst presence / absence determining unit 10 constitutes an AGC operation / non-operation mode switching control unit that controls switching between the AGC operation mode and the AGC non-operation mode.

In a receiver or the like in which the burst period and the duration of the burst signal are fixed, and the intermittent reception timing is controlled by an intermittent reception control unit (not shown), the burst is controlled by using the intermittent reception control unit. The presence / absence determination unit 10 can be configured. In this case, the burst presence / absence determining unit 10 outputs a reception determination signal (for example, L level) 10a specifying the AGC operation mode during a period in which a burst signal is present (burst reception timing), and when a non-reception (no signal) period is reached. At the same time, it outputs a reception discrimination signal (for example, H level) 10a designating the AGC non-operation mode, and furthermore, a reception decision signal (for example, L level) slightly before the next burst reception timing arrives. 10a is output.

A little before this point, the response characteristic of the variable gain amplifier when the gain is changed, and the delay time in the low-pass filter when the gain control signal is supplied to the variable gain amplifier through the low-pass filter ( In consideration of the time constant, a setting is made so that the signal can be amplified with a substantially appropriate amplification gain from the first part of the next arriving burst signal.

FIG. 5 is a block diagram showing a specific example of a burst presence / absence determining section for generating a reception determination signal based on a received burst signal. When the reception time of the burst signal or the duration of the burst signal is undefined, it is necessary to generate the reception determination signal 10a based on the received burst signal 1a. Burst presence / absence determining section 10 shown in FIG. 5 receives reception intensity signal 5 output from reception level detector 5 shown in FIG.
a or reception intensity data 6a as an A / D conversion output thereof
Is generated based on the received signal.

5 includes a burst signal reception presence / absence determination unit 11, a reception determination threshold setting unit 12, a time clock generation unit 13, a time counter 14, and an early switching control unit 15. , An early switching timing setting unit 16 and a reception determination signal output unit 17.

The burst signal reception presence / absence determination section 11 compares the reception intensity signal 5a or the reception intensity data 6a with the reception determination threshold value 12a, and determines whether the reception intensity signal 5a or the reception intensity data 6a has the reception determination threshold value 12a. If it exceeds, it indicates a burst signal reception state (for example, H level).
It outputs the reception state signal 11a. When the reception strength signal 5a or the reception strength data 6a is equal to or less than the reception determination threshold value 12a, the burst signal reception presence / absence determination unit 11 generates the reception state signal 11a indicating a non-reception state (no signal state) (for example, L level). Output.

The reception determination threshold value setting unit 12 supplies a preset reception determination threshold value 12a to the burst signal reception presence / absence determination unit 11. The reception determination threshold value 12a can detect the presence of a burst signal even when the reception electric field strength is low, for example, even when the electric field strength at a service limit point of a wireless communication service or the like or the communication reception electric field is slightly lower. Is set as follows. When the burst signal reception presence / absence determination unit 11 determines that burst reception is to be performed based on the reception intensity signal 5a, the reception determination threshold setting unit 12
Supplies a preset reception determination threshold signal 12a. When the burst signal reception presence / absence determination unit 11 determines the burst reception based on the reception intensity data 6a, the reception determination threshold value setting unit 12 supplies preset reception determination threshold data 12a.

The clock generator 13 generates a clock 13a having a period sufficiently shorter than the burst period. The clock 13a is supplied to a clock input terminal of the clock counter 14.

The time counter 14 receives the reception state signal 11a.
Resets the counter value when it changes from the non-reception state (L level) to the reception state (H level), and counts the clock 13a immediately after the reset. When the count value reaches a preset count upper limit value, the timer counter 14 stops the stepping operation of the counter and holds the counter value. The count upper limit is set longer than the burst period of the burst signal. The count value 14 a of the time counter 14 is supplied to the early switching control unit 15.

The early switching control section 15 has a count value 14a.
Temporarily stores the value (maximum count value) before returns to zero. However, when the count value 14a is the count upper limit value, the early switching control unit 15 does not take in the count value 14a. Therefore, the previously stored count value is retained. The early switching control unit 15 subtracts the early switching count value 16a supplied from the early switching timing setting unit 16 from the temporarily stored previous maximum count value, and uses the count value obtained by the subtraction to start the AGC operation. It is temporarily stored as the operation start count value. When the next count value 14a reaches the AGC operation start count value, the early switching control unit 15 issues the AGC operation start request 1
5a is output.

The early switching timing setting section 16 supplies an early switching count value 16a for designating how far before the reception timing of the next burst signal the AGC operation should be started. The early switching time is obtained by multiplying the early switching count value 16a by the period of the clock clock.
The early switching count value 16a is determined by the response characteristic of the variable gain amplifier when the gain is changed, and the delay time (time constant) of the low-pass filter when the gain control signal is supplied to the variable gain amplifier via the low-pass filter. ) Is taken into consideration so that the burst signal arriving next can be amplified with an approximately appropriate amplification gain from the first part.

When the AGC operation start request 15a is supplied, or when the reception state signal 11a changes from the non-reception state (L level) to the reception state (H level), the reception determination signal output unit 17 outputs the AGC signal. An AGC non-operation mode is designated when the reception state signal 11a changes from the reception state (H level) to the non-reception state (L level) when the reception determination signal 10a specifying the operation mode (L level) is output ( (H level) A reception determination signal 10a is output. In addition,
The reception determination signal output unit 17 outputs the AGC operation start request 15a.
If the reception state signal 11a indicating the reception state (H level) is not supplied even after a predetermined time has passed from the point at which the AGC is supplied, the reception determination signal 10a designating the AGC non-operation mode (H level) is output. Make up. The reception determination signal output unit 17 outputs the (H level) reception determination signal 10a designating the AGC non-operation mode when the count upper limit signal 14b indicating that the count upper limit has been reached is supplied from the clock counter 14. May be configured.

FIG. 6 is a timing chart showing the operation of the burst presence / absence determining section shown in FIG. FIG. 6A shows a reception burst signal, FIG. 6B shows a reception intensity, and FIG.
FIG. 6C shows a reception state signal 11a output from the burst signal reception presence / absence determining section 11, and FIG.
6 (e) shows the reception determination signal 10a output from the burst presence / absence determination unit 10.

As shown in FIG. 6D, the count value 14a
Is switched to the AGC operation mode when the AGC operation start count value is reached, so that the AGC operation mode can be set just before the next burst signal 1a arrives.

FIG. 7 is a timing chart showing the operation of the burst AGC circuit according to the present invention. 7A shows the presence / absence of the burst signal 1a, and FIG. 7B shows the designation state of the AGC operation / non-operation mode by the reception determination signal 10a.
FIG. 7C shows a change in the gain control signal 3b, and FIG. 7D shows a waveform (envelope) of the AGC output signal 3c.

In a period in which no reception burst signal is received (no signal period), the AGC non-operation mode is set.
Thereby, the amplification gain of the variable gain amplifier 3 is set to the minimum gain or a small value. The AGC operation mode is set shortly before the next burst signal arrives. Thereby, the AGC control unit 4 starts the operation of adjusting the amplification gain of the variable gain amplifier 3 according to the reception intensity. Since the AGC operation is started before the burst signal arrives, gain control data 7a having a large value is output from gain setting section 7 to increase the amplification gain of variable gain amplifier 3 based on a small level of a noise signal or the like. However, the gain control signal 3b supplied to the gain control input terminal 3a of the variable gain amplifier 3 by the time constant of the low-pass filter 9 is shown in FIG.
As shown in (c), the signal gradually increases from the state in which the minimum gain is specified to the direction in which the amplification gain increases. And
When the burst signal 1a is received, the gain control data 7a is set based on the signal strength of the received burst signal 1a.

Here, as shown in FIG. 7 (b), the time T for accelerating the start of the operation, that is, the time constant of the low-pass filter 9 for switching the timing to the AGC operation mode, and the variable gain amplifier if necessary The burst signal is received from the point of switching to the AGC operation mode by setting including the response time of 3 (the time from when the amplification gain is set by the gain control signal 3b to when the amplification gain becomes the designated amplification gain). During this period, the AGC output signal 3c having a substantially appropriate level range can be obtained from the first part of the burst signal without the amplification gain becoming excessive.

[0050]

As described above, the burst AGC circuit and the burst AGC control method according to the present invention provide an AGC operation mode for controlling the amplification gain of a variable gain amplifier for amplifying a burst signal according to the signal level of the burst signal. The AGC non-operation mode in which the amplification gain of the variable gain amplifier is fixed to a preset small value is switched in synchronization with the presence or absence of a burst signal. The amplification gain can be set small. Accordingly, it is possible to prevent the power consumption of the variable gain amplifier from increasing due to the full noise output state in the no-signal state, and to prevent an excessive level from being supplied to the subsequent circuit elements and the like. In addition, since the amplification gain of the variable gain amplifier is switched to the AGC operation mode from a small value, an excessive level signal is not output from the variable gain amplifier at the time of switching to the AGC operation mode.

Further, in the burst AGC circuit and the burst AGC control method according to the present invention, the AGC operation mode is set during reception of the burst signal, and when the burst signal is not received, the mode is switched to the AGC non-operation mode, and the next burst A predetermined time before the arrival timing of the signal
Since the mode is switched to the C operation mode, AGC amplification of a burst signal arriving next can be reliably performed. Considering the response characteristics of the variable gain amplifier at the time of changing the gain and the delay time (time constant) of the low-pass filter when the gain control signal is supplied to the variable gain amplifier via the low-pass filter, the AGC is performed. By setting the timing of switching to the operation mode, it is possible to amplify the burst signal with a substantially appropriate amplification gain from the first part.

[Brief description of the drawings]

FIG. 1 is a block diagram of a burst AGC circuit according to the present invention.

FIG. 2 is a block diagram showing a specific example of a gain setting unit.

FIG. 3 is a block diagram showing another specific example of the gain setting unit.

FIG. 4 is a block diagram showing still another specific example of the gain setting unit.

FIG. 5 is a block diagram illustrating a specific example of a burst presence / absence determining unit that generates a reception determination signal based on a received burst signal.

FIG. 6 is a timing chart showing an operation of a burst presence / absence determining section shown in FIG. 5;

FIG. 7 is a timing chart showing an operation of the burst AGC circuit according to the present invention.

FIG. 8 is a block diagram of a conventional AGC circuit.

FIG. 9 is a timing chart showing the operation of a conventional AGC circuit.

[Explanation of symbols]

 Reference Signs List 1 burst AGC circuit 2 distributor 3 variable gain amplifier 4 AGC control unit 5 signal level detector (logarithmic amplifier) 6 A / D converter 7 gain setting unit 8 D / A converter 9 low-pass filter (low-pass filter) 10 Burst existence judgment part

Claims (10)

[Claims] 1. A distributor that distributes a received burst signal into two, and a burst signal distributed by the distributor, which is input into an AG.
A variable gain amplifier capable of changing a gain so as to enable C operation; a logarithmic amplifier for converting a burst signal distributed by the distributor into an analog value for displaying a received signal electric field; An A / D converter for converting an analog value to a received signal electric field display digital value; an AGC on-state gain control digital data corresponding to the received signal electric field display digital value so as to enable an AGC operation; AGC-off state gain control digital data for minimizing the gain of the variable gain amplifier regardless of the signal electric field display digital value is stored, and gain control digital data corresponding to these two states is input from outside. R to switch and output according to the instruction of the received discrimination signal
OM; a D / A converter for converting the gain control digital data output from the ROM into an analog value; smoothing the gain control analog value output from the D / A converter and providing a time constant to vary the gain. A burst AGC circuit comprising: a low-pass filter for inputting a gain control signal to an amplifier. 2. A reception determination signal for determining whether a reception signal is on or off is supplied to the ROM, and the reception determination signal indicates to the ROM that the signal is on when the signal is on. To select the AGC ON state,
2. The burst A according to claim 1, further comprising: a burst presence / absence determining unit for instructing the ROM that the signal is off when the signal is off and selecting the AGC off state.
GC circuit. 3. The burst presence / absence determination unit changes the AGC off state from the AGC off state in consideration of a delay in the low-pass filter.
The reception discrimination signal switching timing for turning on the C-state is set slightly before the signal is turned on. Immediately after the signal is switched from off to on, the gain control signal output from the low-pass filter is set to the AGC output level. The burst AGC circuit according to claim 2, wherein the burst AGC circuit is controlled. 4. A distributor for distributing a received burst signal into two, and receiving the burst signal distributed by the distributor,
A variable gain amplifier for changing a gain to enable C operation; a logarithmic amplifier for converting a burst signal distributed by the distributor to a received signal electric field indicating analog value; and a receiving signal electric field from the received signal electric field indicating analog value. An A / D converter for converting into a display digital value; a ROM for outputting gain control digital data corresponding to an input received signal electric field display digital value so as to enable an AGC operation; and a gain control digital data output from the ROM. AGC only when the signal is on
A multiplier for converting the gain control digital data into an operable one; a D / A converter for converting the gain control digital data output from the multiplier into an analog value; a gain control analog value of the variable gain amplifier And a low-pass filter for applying a time constant to the gain amplifier and inputting it as a gain control signal to the gain amplifier. 5. A signal for determining whether a received signal is on or off is supplied to the multiplier, and a signal indicating that the signal is on when the signal is on is supplied to the multiplier. The gain control digital data output from the ROM is multiplied to be converted into gain control digital data that turns on the AGC. When the signal is off, a signal indicating that the signal is off and the gain control digital data output from the ROM are converted. 5. The burst AGC circuit according to claim 4, further comprising a burst presence / absence discriminator for multiplying and converting the data into gain control digital data that is turned off. 6. The burst presence / absence determining unit switches an AGC off state from an AGC off state in consideration of a delay in the low-pass filter.
The reception discrimination signal switching timing for turning on the C-state is set slightly before the signal is turned on. Immediately after the signal is switched from off to on, the gain control signal output from the low-pass filter is set to the AGC output level. The burst AGC circuit according to claim 5, wherein the burst AGC circuit is controlled. 7. A variable gain amplifier to which a burst signal is input and whose amplification gain is varied based on a gain control signal, a reception level detector that detects a level of the burst signal and outputs a reception intensity signal, An A / D converter for converting an intensity signal into reception intensity data; gain control data set in advance corresponding to the reception intensity data; and gain control data when the AGC is not operating. A gain setting unit that outputs gain control data corresponding to the reception intensity data when the AGC operation mode is designated based on the AGC operation mode, and outputs the gain control data when the AGC operation is not performed when the AGC non-operation mode is set A D / A converter for converting the gain control data output from the gain setting unit into an analog signal; and an A / D converter output from the D / A converter. It bursts AGC circuit, characterized in that by smoothing with a time constant that set the log signal previously provided with a low-pass filter is supplied to the variable gain amplifier as the gain control signal. 8. A burst AGC circuit for controlling an amplification gain of a variable gain amplifier according to a signal level of a burst signal, wherein when the burst signal does not exist, the amplification gain of the variable gain amplifier is reduced to a preset small value. A burst AGC control method characterized by being fixed. 9. An AGC operation mode for controlling an amplification gain of a variable gain amplifier for amplifying a burst signal according to a signal level of a burst signal, and an AGC operation mode for fixing the amplification gain of the variable gain amplifier to a preset small value. A burst AGC control method, wherein an operation mode is switched in synchronization with the presence or absence of a burst signal. 10. The AGC operation mode is set during reception of a burst signal, and when the burst signal is not received, the mode is switched to the AGC non-operation mode, and the AGC operation mode is performed a predetermined time before the arrival timing of the next burst signal. 10. The burst AGC control method according to claim 9, wherein the mode is switched to a mode.