JP3268882B2 - Power control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control circuit for controlling a signal level of a communication signal.

[0002]

2. Description of the Related Art TDMA (Time Division Multiple Acce
ss) The frequency band used in the digital car mobile phone system using the system is 800 MHz in Japan.
z, 1500 MHz band is planned. Further, it is stipulated that the transmission power of the mobile station can be controlled by the base station, and the maximum transmission power must not exceed a standard value.

For example, in the case of the Japanese digital car telephone system, the transmission output is determined as shown in FIG. 3 according to the type of mobile station. The output range allowed at the time of the maximum transmission output is defined as: maximum transmission output−50% <output <maximum transmission output + 20%. The control range is defined to be controlled in 4 dB steps such as 0, -4, -8,... Within the range shown in FIG. As described above, since the transmission output and the control range are determined, a power control circuit that performs high-accuracy transmission output control is required in the mobile station.

Hereinafter, a conventional power control circuit will be described. Conventionally, an APC (Auto Power Control) circuit has been used as a power control circuit. FIG. 5 is a functional block diagram showing a configuration example in which the APC circuit is used for transmission output control. 501 is an output variable circuit, 502 is a power amplifier, 503 is a transmitting antenna, 5
04 is an output detection circuit, 505 is a level comparison circuit, 506
Is a DC amplifier, and 507 is a smoothing circuit.

As the output variable circuit 501, for example, P
A voltage-controlled variable attenuator constituted by an IN diode is used, and the input transmission signal S is controlled by the control voltage V ₃ sent from the smoothing circuit 507,
Output to the power amplifier 502. As the power amplifier 502, for example, a high-frequency amplifier is used, which amplifies the output voltage of the output variable circuit 1 and outputs the amplified voltage to the transmission antenna 503.

The transmitting antenna 503 uses, for example, a whip antenna, converts an output voltage of the power amplifier 502 into a radio wave, and transmits the radio wave. As the output detection circuit 504, for example, a circuit that detects the envelope of the input voltage is used. In this output detection circuit, the input voltage have been used a diode which conducts only during the period near the maximum value, the output voltage V _B of the power amplifier 502 to envelope detection.

[0007] level comparison circuit 505, for example, operational amplifiers and comparators are used to output a predetermined voltage V ₂ by the sign of the difference between the output voltage V ₁ and the reference voltage V _REF of the output detector circuit. DC amplifier 506 amplifies the output voltage V ₂ of the level comparison circuit. The smoothing circuit 507 smoothes the voltage waveform of the output voltage V ₂ ′ of the DC amplifier 506.

Hereinafter, the operation of the APC circuit will be described with reference to the waveform diagram of FIG. First, the output variable circuit 50
1 receives the transmission signal S modulated by π / 4 shift DQPSK by TDMA transmission shown in FIG. 6A, amplifies the transmission signal S by a predetermined amount, and outputs the amplified signal to the power amplifier 502 as an output voltage _VA. . Power amplifier 502 amplifies output voltage V _A and outputs it as output voltage V _B.

The transmission antenna 503 is connected to the power amplifier 50
2 output voltage V_BTo generate and transmit radio waves. Out
The power detection circuit 504 outputs the output voltage V of the power amplifier 502.
_BIs converted to a direct current by envelope detection, and FIG.
A detection voltage V having a waveform as shown₁Is output. Level comparison
The circuit 505 detects the detection voltage V₁Is the reference voltage V_REFAnd ratio
And a predetermined output voltage V_TwoTo D
Output to C amplifier 506. This V _TwoFigure 6 shows the waveform
It is shown in (C).

[0010] DC amplifier 506 amplifies the output voltage V _2, and outputs an output voltage V ₂ '. Smoothing circuit 507
Smoothes this V ₂ ′ to obtain an output voltage V ₃ having a waveform shown in FIG. Then, this output voltage V ₃ is applied to the output variable circuit 501 as a control voltage.

As described above, in the APC circuit, the detection voltage V1 of the output Pa of the power amplifier 502 is equal to the reference voltage VRE.
The control voltage V3 changes so that the output voltage Pa becomes equal to F.
Operates so as to maintain a constant value. For this reason, if the APC circuit is used, it is possible to suppress a change in the transmission level due to a temperature drift or a variation in elements.

[0012]

However, in this configuration, when a transmission signal by burst transmission such as the TDMA method is received, the transmission signal includes no signal period (t ₂ ′).
t ₃ ′, t ₄ ′ to t ₅ ′,...), the detection voltage V ₁ during that time becomes 0 V as shown by b in FIG. The output voltage V ₂ is generated in the direction of increasing the transmission output during the entire period (FIG. 6).
(See c in (C)).

Accordingly, the output voltage V of the smoothing circuit 507
_ThreeIs the non-signal period (t_Two’-T _Three’, T_Four’~
t_Five′,...), Gradually increase its output voltage
(See d in FIG. 6D). As a result, the transmission signal S
Rising time from the signal period (t₁’, T_Three’・ ・)
The APC circuit to increase the transmission level Pa
Operates (output control voltage V_ThreeDirection to increase output
), And as shown in FIG.
At the rising edge of S, the transmission level Pa
Level V_REFHigher. One way to improve this
The time constant of the smoothing circuit 507 is
It is conceivable to make the transmission cycle sufficiently longer.

However, if the time constant is increased, the ability to follow the input of the output control by the APC circuit deteriorates. Further, if the transmission level deviates from a predetermined value at the start of the operation of the APC circuit, if the transmission level deviates from the predetermined value, The problem is that the convergence is delayed. Also, the transmission output is 0,-
4, -8,. . . As a method of controlling in 4 db steps as described above, a method of changing the reference voltage VREF is conceivable. According to this method, the transmission level can be controlled. Detection becomes impossible, and the APC circuit does not operate. For this reason, there has been a problem that a sufficient output control range cannot be obtained.

Therefore, in the present invention, in view of the above problems,
It is an object of the present invention to provide a power control circuit which can reduce the fluctuation of the transmission level with respect to a transmission signal by burst transmission, and can take a sufficient output control range even when the transmission level is lowered.

[0016]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problem, the invention of claim 1 is to detect an output signal of a variable amplifying circuit for periodically amplifying a transmission signal including a no-signal period by a detection circuit. In a power control circuit that compares the detection output with a reference voltage in a comparison circuit and feeds back a signal based on the comparison output to the variable amplifier to control the amplification, the signal is inserted between the detection circuit and the comparison circuit, and the transmission signal rises. A sample-and-hold circuit for holding the detection output, a means for receiving a set value indicating the magnitude of the output signal of the variable amplifier, and the specified set value between the comparison circuit and the variable amplifier. Switch means for turning on when the output is a transmission output, and turning off when the set value is not the maximum transmission output; and when the switch is off, an output signal of the variable amplifier. Characterized by comprising a voltage generating means for sending a control voltage such that the designated set value to the variable amplifier.

According to a second aspect of the present invention, in the power control circuit according to the first aspect, the power control circuit further includes means for receiving a set value indicating the magnitude of the output signal of the variable amplifier, and the instruction between the comparison circuit and the variable amplifier. Switch means for turning on when the set value is the maximum transmission output, and turning off when the set value is not the maximum transmission output; and when the switch is off, the output signal of the variable amplifier indicates the command. Voltage generating means for sending a control voltage having a set value to the variable amplifier.

[0018]

The sample and hold circuit holds the signal level at the time of receiving the input signal during the non-signal period. Thus, the fluctuation of the output voltage of the level comparison circuit at the start of the non-signal period is reduced, and the fluctuation of the output voltage of the smoothing circuit is reduced. For this reason, the fluctuation of the transmission level from the reference level can be reduced. In addition, a sufficient output control range can be obtained even when the transmission level decreases.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A power control circuit according to the present invention will be described below with reference to an example of use in a digital automobile cellular phone system with reference to the drawings. FIG. 1 is a configuration example of a power control circuit of the present invention. 1 is a receiving unit,
2 is a control unit, 3 is a transmission unit, 4 is an APC circuit, 101 is an output variable circuit, 102 is a power amplifier, 103 is a transmission antenna, 104 is an output detection circuit, 105 is a level comparison circuit, 106 is a DC amplifier, 107 is Smoothing circuit, 108 is a sample and hold circuit, 109 is a switch, 110 is a voltage synthesis circuit, 111 is a receiving antenna, 112 is a receiving circuit, 113 is a timing pulse generating circuit, 114 is a transmission output control circuit, and 115 is a transmission output control voltage generation Circuit, 1
Reference numeral 16 denotes a maximum output determination circuit.

The receiving unit 1 includes a receiving antenna 111 and a receiving circuit 112, receives the power control information transmitted from the base station, demodulates the received power control information into received data, and transmits the data to the control unit 2. As the receiving antenna 111, for example, a whip antenna is used and receives power control information transmitted from a base station. The receiving circuit 112 includes, for example, a circuit in which a demodulation circuit is directly connected to a radio frequency circuit. The receiving circuit 112 demodulates power control information received by the receiving antenna 111 to generate reception data, and generates a timing pulse generation circuit 113 and a transmission output signal. Output to the control circuit 114.

The control unit 2 includes a timing pulse generation circuit 1
13, a transmission output control circuit 114, a transmission output control voltage generation circuit 115, and a maximum output determination circuit 116, which receive the power control information input from the reception unit 1 and control the operation of the transmission unit 3. Timing pulse generation circuit 11
3, for example, a pulse generating circuit generates a timing pulse T _X synchronized with the transmission cycle of the transmission signal in a burst transmission, and transmits to the sample-and-hold circuit 108. Phase of the timing pulse T _X is consistent with the phase of the transmission signal S.

The transmission output control circuit 114 receives the reception data input from the reception unit 1, creates transmission level setting data for setting the transmission level of a transmission signal transmitted from the transmission antenna 103, and generates a transmission output control voltage. Circuit 115
And the maximum output determination circuit 116. When receiving the transmission level setting data transmitted from the transmission output control circuit 114, the transmission output control voltage generation circuit 115 generates a transmission output control voltage.

The maximum output determination circuit 116 uses the transmission level setting data received from the transmission output control circuit 114
To maximize the transmission level, the switch 109 is turned on, and otherwise, the switch 109 is turned off. The transmitting unit 3 includes an APC circuit 4 for keeping the output constant, a switch 109, and a voltage synthesizing unit 110. In the figure, AP
Among the components of the C circuit 4, components having the same names as the components in FIG. 5 have the same configurations as the components having the same names as the components in FIG.

The APC circuit 4 is an APC circuit described in the prior art.
The circuit 5 further includes a sample and hold circuit 108,
It has a configuration that can respond to a transmission signal by burst transmission. The switch 109 is a switch for switching between forcibly changing the transmission level and performing the APC operation. At the time of the maximum transmission output, the APC circuit 4 is operated, and otherwise, the APC circuit 4 is not operated.

The voltage synthesizing unit 110 includes resistors R ₁ and R ₂ and generates a control voltage V ₅ . Sample hold circuit 1
08 samples the detection voltage V ₁ of the transmission signal by the burst transmission detected by the output detection circuit 104 using the timing pulse T _X synchronized with the generation cycle of the transmission signal, and if the transmission signal is not received, the sampled detection voltage V ₁ is sampled. And outputs the output voltage V _SH to the level comparison circuit 105.

Hereinafter, the operation of the power control circuit will be described by taking an example of the operation in a digital automobile portable telephone system. A base station in a digital car mobile phone system transmits power control information for controlling the transmission level on the mobile station side according to the radio wave condition of the mobile station. The receiving unit 1 of the mobile station receives the power control information transmitted from the base station, demodulates the received data into reception data in the receiving circuit 112, and then controls the transmission output control circuit 11 of the control unit 2.
4 is output.

The transmission output control circuit 114 creates transmission level setting data based on the received data, and transmits it to the transmission output control voltage generation circuit 115 and the maximum output determination circuit 116. The transmission output control voltage generation circuit 115 generates an output control voltage V ₄ , and the maximum output determination circuit 116 determines whether or not to transmit at the maximum output in the transmission antenna 103 based on the transmission level setting data. When transmitting, a control signal (APC ON / OFF signal) for turning on the switch is transmitted to the switch 109, and the switch 109 is turned on.
State.

The variable output circuit 101 receives the transmission signal S modulated by π / 4 shift DQPSK by TDMA transmission shown in FIG. 2A, and the power amplifier 102 amplifies the output voltage of the variable output circuit 101. The transmission antenna 103 performs radio wave transmission using the output voltage of the power amplifier 102, and the output detection circuit performs envelope detection on the output voltage of the power amplifier 102. The output waveform after detection is as shown in FIG.

The sample and hold circuit 108 includes a switch
108a, as shown in FIG.₁~ T_Two
ON during t_Two~ T_ThreeOFF during₁
~ T _Two, The output voltage V of the output detection circuit 104₁The
Output as is, and t_Two~ T_ThreeDuring the interval to the capacitor Ca
t₁~ T_TwoAnd outputs the charged voltage. That out
Force voltage V_SH2B is shown in FIG.

The level comparison circuit 105 compares the output voltage V _SH of the sample-and-hold circuit 108 with the reference voltage V _REF and generates a difference voltage V _2. As a result, the voltage waveform of V ₂ is as shown in FIG. It becomes flat as shown in c).

The DC amplifier 106 amplifies the V _2, and outputs an output voltage V ₂ '. The smoothing circuit 107 has an output voltage V ₂ ′
The smoothed, as the output control voltage V _3, and outputs. At this time, the output control voltage V ₃ smoothes the voltage fluctuation seen in V _2, and has a flat waveform as shown in FIG. Since the switch 109 is in the ON state in the case of the maximum transmission output, the control voltages V ₃ and V ₄ are equal to the resistance R of the voltage synthesis unit 110.
₁ and R ₂ , V ₅ = V ₃ · R ₁ / (R ₁ + R ₂ ) + V ₄ · R ₂ / (R
A control voltage V ₅ represented by ( ₁ + R ₂ ) is applied to the output variable circuit 101 as a control voltage. Here, V ₄ is constant,
As shown in FIG. 2 (D), V ₃ is also substantially constant.
As shown in FIG. 2 (F), V ₅ is made approximately constant. V
_Since the fluctuation of ₅ is small, the output of the power amplifier during this period substantially matches the reference level.

When the transmission power is not the maximum, the switch 1
09 becomes OFF (V ₅ = V _4), in accordance with the power control information from the base station, the transmission power control voltage V4 generated by the control unit controls the output level. By the above operation, SW
Maximum transmission time output 109 is turned on, the output P _A, as shown in FIG. 2 (E)
Changes as shown in FIG. Also, as shown in FIG.
109 The output level of less than the maximum transmit power has been turned off, the output P _A -4, outputs controlled in 4db steps as -8 ....

Note that the present invention is not limited to the above configuration, and the switch 109 can be omitted when the detectable range of the output detection circuit 104 is wider than the range of fluctuation of the output level.

[0034]

According to the present invention, the sample-and-hold circuit can hold the signal level at the time of reception of the transmission signal during the non-signal period, so that the absolute value of the comparison output is reduced during the no-signal period. be able to. For this reason, at the start of transmission signal reception, the output voltage of the smoothing circuit maintains a value close to that at the time of transmission signal reception. For this reason, at the start of transmission signal reception, it is possible to reduce the fluctuation of the signal level from the reference level.

Further, when the signal level is out of the predetermined range, the switch means does not transmit the output voltage of the smoothing circuit to the variable amplifier, so that it is possible to prevent the detection means from operating when the signal level decreases. For this reason, even when the signal level fluctuates, the signal level can be controlled and the output control range can be increased, so that its practical utility is high.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a power control circuit according to the present invention.

FIG. 2 is a diagram illustrating an embodiment of a power control circuit according to the present invention.

FIG. 3 is a diagram illustrating a conventional technique.

FIG. 4 is a diagram illustrating a conventional technique.

FIG. 5 is a circuit diagram of a conventional power control circuit.

FIG. 6 is a diagram illustrating an operation of a power control circuit according to the related art.

[Description of Signs] 1 APC circuit 2 Transmitter 3 Controller 4 Receiver 101 Output variable circuit 102 Power amplifier 103 Transmit antenna 104 Output detector 105 Level comparator 106 DC amplifier 107 Smoothing circuit 108 Sample hold circuit 109 Switch 110 Voltage synthesis Circuit 111 Receiving antenna 112 Receiving circuit 113 Timing pulse generating circuit 114 Transmission output control circuit 115 Transmission output control voltage generating circuit 116 Maximum output judgment circuit 501 Output variable circuit 502 Power amplifier 503 Transmission antenna 504 Output detection circuit 505 Level comparison circuit 506 DC Amplifier 507 Smoothing circuit

Claims (1)

(57) [Claims] An output signal of a variable amplifier circuit for periodically amplifying a transmission signal including a non-signal period is detected by a detection circuit, and the detection output is compared with a reference voltage by a comparison circuit. A power control circuit that feeds back to the variable amplifier to control the degree of amplification; a sample and hold circuit inserted between the detection circuit and the comparison circuit to hold the detection output while the transmission signal is rising; Means for receiving a set value indicating a signal magnitude, and turning on between the comparison circuit and the variable amplifier when the specified set value is the maximum transmission output, and when the set value is not the maximum transmission output, Switch means for turning off, and when the switch is off, a control voltage such that an output signal of the variable amplifier becomes the instructed set value to the variable amplifier. Power control circuit, characterized in that it includes a voltage generation unit that.