JPH08223057A - Output level control circuit - Google Patents

Abstract

PURPOSE: To set the control speed of automatic output level control(ALC) and that of automatic transmission output level control(ATPC) independently of each other by controlling the level of a signal in first and second level control means by extents in advance, set corresponding to level control information. CONSTITUTION: The first level control means which controls the level of an input signal by a first control speed γ1 to output it and the second level control means which controls the level of the signal sent from the first level control means by a second control speed γ2 lower than the first control speed are provided. The first level control means gives an extent of attenuation corresponding to a reference level Vref3 or Vref4 to the input signal and sends it to the second level control means. An operational amplifier 11 controls the level of the inputted signal so that the output of a detector 16 matches with a reference level Vref1 or Vref2 , and the result is transmitted as the output signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output level control circuit used in, for example, a digital radio system.

In a digital radio system having a step-level control type automatic output level control function (for example, an automatic transmission output level control function), a threshold is set for the reception level of a receiving device, and the reception level is set below the threshold. When it decreases, the output level of the opposing transmitter is stepwise increased by a predetermined amount.

Here, as a factor of the change in the reception level,
For example, there are temperature fluctuations / aging of the transmitter and fading that occurs in the transmission path. When the output level of the transmitter is controlled to compensate for this change in the reception level, the transmitter uses an automatic transmission output level control function with a slower control speed for the former and a faster control speed for the latter. It is necessary to provide a transmission output level control function so that the control speed of these functional parts can be set independently.

[0004]

2. Description of the Related Art FIG. 6 is a block diagram of a conventional example. In FIG. 6, the input microwave band signal is transmitted to the outside through the variable attenuator 22 and a power amplifier (not shown) at a predetermined power and frequency, and at the same time, a part of the power is input to the detector 23.

The detector 23 applies the detection output obtained by detecting the input microwave power to the (-) terminal of the operational amplifier 21. On the other hand, at the (+) terminal, for example, the reference level V _ref1 generated by dividing the reference voltage V by the variable resistor RV ₁₁ ,
The voltage is applied through the selector SEL ₅ and the time constant circuit 24 having the time constant τ ₃ .

Therefore, the operational amplifier 21 amplifies the difference between the reference level and the detector output and takes out the amplified output, which is added to the variable attenuator 22 via the time constant circuit 25 having the time constant τ ₂ .
Adjustable attenuator so that the detection output matches the reference level V _ref1
Controls the attenuation of 22.

Note that τ ₂ ≧ τ ₃ is set. Here, there are two types of binary control information for automatic transmission output level control (hereinafter, abbreviated as ATPC) of High / Low, and the selector SEL ₅ has, for example, ATPC binary control information of H. The reference level V _ref1 is selected at the time, and the reference level V _ref2 is selected at the time of L. This control information is received by the opposite station → transmitter of the opposite station → (reverse line) → own station From the receiving device to the transmitting device of the own station.

Although the circuit configuration for controlling the transmission output level is simple as shown in FIG. 6, the control speed of ATPC is the same as the control speed of automatic output level control (hereinafter abbreviated as ALC). Therefore, it is a good idea when the modulation method can increase the ALC control speed like the PSK method. However, this is a problem because the control speed of ALC cannot be increased in the multilevel QAM method.

In the case of the PSK method, the position of the signal point is on the circumference of the average power, so even if the ALC control is fast, the fixed deterioration (the theoretical value of the reception level corresponding to the given BER is obtained. Difference between the measured value and the actual value).

However, in the case of the multi-valued QAM system, since the position of the signal point is located outside the average value, the ALC function performs an operation of pulling the peak value to the average value, which causes a characteristic deterioration. Therefore, the ALC operation cannot be speeded up.

[0011]

As described above, although the circuit configuration of the conventional example is simple, the control speed of ATPC becomes the same as the control speed of ALC. Therefore, the modulation method is PSK and ALC
It is a good idea if the control speed of the
The M method has a problem that it is difficult to follow fast fading because the ALC control speed cannot be increased.

[0012]

According to a first aspect of the present invention, a first level control means for controlling and outputting the level of an input signal at a first control speed, and the first level control means sends the same. Second level control means for controlling and outputting the signal level at a second control speed slower than the first control speed is provided.

Then, the first level control means and the second level control means are each configured to control the level of the signal by a preset amount corresponding to the level control information.

In the second aspect of the present invention, the first level control means and the second level control means are provided in the radio frequency band of the transmitter. According to a third aspect of the present invention, the first level control means and the second level control means are provided in an intermediate frequency band of the transmitter.

According to a fourth aspect of the present invention, the first level control means is provided in one of the intermediate frequency band and the radio frequency band, and the second level control means is provided in the other.

[0016]

FIG. 1 is a diagram for explaining the principle of the present invention, (a) is a principle configuration diagram, and (b) is a control state diagram.

According to the present invention, as shown in FIG. 1 (a), a _first output is performed by controlling the level of an input signal at a first control speed (τ ₁ ).
And the second level control means for controlling the level of the signal sent by the first level control means at the _second control speed (τ ₂ ) slower than the first control speed.

Then, the first level control means gives the input signal an attenuation amount corresponding to one of the reference levels V _ref3 / V _ref4 and sends it to the second level control means.
Operational amplifier 11 in the second level control means, either so as to coincide with one to control the level of the input signal the output signal of the output reference level V _ref1 / V _{re f2} of the detector 16 To send as.

The selectors SEL ₁ and SEL ₂ are adapted to select the reference levels corresponding to the input level control information. That is, the second level control means
It is provided for ALC control, and by selecting the reference level by the level control information (that is, ATPC control information),
The level of the output signal is controlled by controlling the amount of attenuation of the built-in second level control portion 14.

Further, the first level control means controls the attenuation amount of the first level control portion 15 at a control speed faster than that of the second level control means to perform the level control of the input signal. The level change of the output signal sent by the level control means is accelerated.

Further, the output level control circuit has three time constant circuits having time constants τ ₁ , τ ₂ and τ ₃ which determine the control speed. The time constant τ ₁ is the control speed (AT
Control speed of PC), which is usually set slower than the tracking speed of AGC of the receiving device (not shown).
If set fast, the input level of the demodulator in the receiver may fluctuate and errors may occur.)

Further, since the time constant τ ₁ is set faster than the control speed of ALC, τ ₂ > τ ₁ . Further, when the time constant τ ₃ is slower than the time constant τ ₂ , the rise of the reference level V _ref1 / V _ref2 applied to the operational amplifier 11 is delayed, so that the output signal level is oscillated as described below. It occurs (see the middle of Fig. 1 (b)).

That is, for example, if the attenuation amount of the first level control portion is reduced, the output level of the signal to be transmitted becomes high. Therefore, the reference level of the operational amplifier 11 must be made higher than the previous value, but the reference level is the time constant τ ₃
It will not reach a high state until the time of.

For this reason, the operational amplifier 11 determines that the detection output has increased and increases the attenuation amount of the second level control portion so as to reduce the transmission output. In order to avoid this, the relation of τ ₂ ≧ τ ₃ is necessary.
The control using the control signal of the PC is performed in a stable state.

The portion A in FIG. 1 (b) is the region where τ ₁ is dominant, the portion B is the region where τ ₂ has started to follow, and C
The region of is the region where τ ₃ tracking started.

[0026]

FIG. 2 is a block diagram of the first and second embodiments of the present invention (in the case of ATPC binary level control), and FIGS. 3 and 4 are block diagrams of the third embodiment of the present invention (ATPC. (For binary level control),
FIG. 5 is a block diagram of another embodiment of the first and second inventions (ATPC
In case of three-level control).

The same reference numerals denote the same objects throughout the drawings, and the two variable attenuators in the drawings are the first and second ones in FIG.
Corresponds to the level control part of. The operation of FIGS. 2 to 5 will be described below, but the portions described in detail above will be briefly described, and the portions of the present invention will be described in detail.

Here, the time constants τ ₁ , τ ₂ , and τ ₃ satisfy the conditions of τ ₂ ≧ τ ₃ and τ ₂ > τ ₁ as in the conventional example, and are applied.
In ATPC binary level control, selectors SEL ₁ and SEL ₂ are V _ref3 and V
_{Suppose ref1} is selected. The time constant circuit uses capacitors C ₁ , C ₂ , and C ₃ , and the reference level is generated by dividing the reference voltage V by the variable resistors RV _{1 to} RV ₁₀ .

As shown in FIG. 2, the mixer 12 frequency-converts the input intermediate frequency band signal into a microwave band signal by using the local oscillation signal from the local oscillator 13, and then the variable attenuator 14a. Add to.

The variable attenuator 14a _{applies the} amount of attenuation corresponding to V _ref3 to the input microwave band signal, and then
15a transmits to the outside through a power amplifier (not shown) and adds a part of the transmission power to the detector 16.

Therefore, the detector 16 adds the detection output obtained by detecting the input microwave power to the (−) terminal of the operational amplifier 111 having an output characteristic having a time constant of τ ₂ .
The reference voltage V _ref1 is applied to the (+) terminal via the selector SEL ₂ and the time constant part of the time constant τ ₃ .

Therefore, the operational amplifier 111 amplifies the difference between the reference voltage and the detector output, extracts the amplified output, and adds the amplified output to the variable attenuator 15a, so that the detected output matches the reference voltage V _ref1 . Control the amount of attenuation.

Since this method controls the level after frequency conversion, it is effective against leakage of the local frequency of the transmission output. In FIG. 3, the variable attenuators 14b and 15b are provided in the intermediate frequency band to control the signal level in the intermediate frequency band. Since this method controls the level before the mixer for frequency conversion, it is disadvantageous for leakage of the local oscillation frequency of the transmission output, but can be implemented with relatively inexpensive parts. The level control method is the same as in FIG.

FIG. 4 shows the variable attenuator 14b in the intermediate frequency band,
The variable attenuator 15a is provided in the microwave band, and the level control is performed before and after the frequency conversion mixer.
The leakage of the local frequency of the transmission output and the parts price are between those of FIGS. 2 and 3.

The variable attenuator 14b is placed in the microwave band,
The variable attenuator 15a may be provided in the intermediate frequency band. Also,
The level control method is the same as in FIG. In the above explanation of operation, ATPC was high / low binary level control.
Shows the case of ATPC high / middle / low ternary level control.

Therefore, the selectors SEL ₃ and SEL ₄ are each 3
It is designed so that any one of the reference levels of the types can be selected, and four types of placement locations of the variable attenuators 14a and 15a can be considered as in the above, but in the case of FIG. The case where it is provided in the belt is shown. The level control method is the same as in FIG.

That is, since the control speed of ALC and the control speed of ATPC can be set independently, the signal is not deteriorated during the transmission of the multilevel QAM modulated wave which is sensitive to the deterioration of the peak level, and the AT is controlled.
The control speed of the PC can be increased.

Therefore, the ATPC can follow the flat fading that changes more rapidly, which contributes to the improvement of the quality of the wireless line.

[0039]

As described above in detail, according to the present invention, there is an effect that the control speeds of ALC and ATPC can be independently set.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention, in which (a) is a principle configuration diagram,
(b) is a control state explanatory diagram.

FIG. 2 is a configuration diagram of the first and second embodiments of the present invention (in the case of ATPC binary level control).

FIG. 3 is a configuration diagram of a third embodiment of the present invention (part 1) (AT
In the case of PC binary level control).

FIG. 4 is a configuration diagram of a third embodiment of the present invention (part 2) (AT
In the case of PC binary level control).

FIG. 5 is a block diagram of another embodiment of the first and second inventions (AT
In the case of PC three-level control).

FIG. 6 is a configuration diagram of a conventional example.

[Explanation of symbols]

11 Operational amplifier 12 Mixer 13 Local oscillator 14 First level control part 15 Second level control part 16 Detector SEL ₁ and SEL ₂ selector

Claims (4)

[Claims] 1. A circuit for controlling an output level of a signal to be transmitted in accordance with applied level control information, comprising first level control means for controlling and outputting an input signal level at a first control speed. , The second level of the signal transmitted by the first level control means is slower than the first control speed.
Second level control means for controlling and outputting at the control speed of, the first level control means and the second level control means are respectively set by preset amounts corresponding to the level control information, An output level control circuit, which is configured to control a signal level. 2. The output level control circuit according to claim 1, wherein the first level control means and the second level control means are provided in a radio frequency band of a transmitter. 3. The output level control circuit according to claim 1, wherein the first level control means and the second level control means are provided in an intermediate frequency band of the transmitter. 4. The output level according to claim 1, wherein the first level control means is provided in one of the intermediate frequency band and the radio frequency band, and the second level control means is provided in the other. Control circuit.