JPH0122278Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-stage variable transmission output circuit which is a circuit that changes the output of a transmitter in multiple stages and is suitable for an output circuit of a radio device such as a car telephone system.

In a car telephone system, when mobile radio terminals move freely within a service area, there is a method to reduce the transmission output of the terminal radio equipment in order to ensure efficient or smooth operation of the system. What is needed is something that can change across the board. Conventionally, as a multi-stage variable transmission output circuit that satisfies this requirement, there are circuits as shown in FIGS. 1 and 2.

FIG. 1 is a circuit diagram showing a four-stage variable transmission output circuit. The output power P ₀ of the transmission output amplifier 10 is branched by a coupling detection circuit 1 having a certain degree of coupling. After passing through a rectifying and smoothing circuit 2 using a diode, this signal is compared with an output voltage V ₀ of a reference voltage generating circuit 4 in a differential amplifier 3. Power supply current control circuit 9 is controlled by the output voltage of differential amplifier 3, negative feedback is applied to transmission output amplifier 10, and transmission output power P ₀ is stabilized. In the above operation, the reference voltages V ₁ , V ₂ , V ₃ and V ₄ determined by the resistor group 6, the variable resistor group 7 and the power supply 8 are connected to the terminal T ₀ and the terminal T ₁ by the signal from the control signal input D. , T ₂ , T ₃
Or an analog switch circuit (e.g. equivalent to NEC KK's μPD4051B) that connects each _T4 .
, and is configured to be the reference voltage V ₀ . Therefore, by changing the reference voltage V ₀ using a control signal and changing the equilibrium point of the closed loop of the coupling detection circuit 1, rectification and smoothing circuit 2, differential amplifier 3, power supply current control circuit 9 and transmission output amplifier 10, The output power P ₀ can be changed. The output power P ₀ at each stage can be adjusted by each variable resistor 7. However, in this operation, the variable resistor must be adjusted for each stage of the transmission output, and the same number of variable resistors as the number of transmission output stages are required.

FIG. 2 shows an example of a four-stage variable transmission output circuit that has improved this drawback. 11, 12, 13, 14, 2
Reference numerals 5 and 26 indicate a coupling detection circuit, a rectifying and smoothing circuit, a differential amplifier, an analog switch, a power supply current control circuit, and a transmission output circuit, respectively, and the configurations are the same as the circuits with the same names in FIG. The reference voltage generation circuit 15 is composed of seven resistors 18 to 24, one variable resistor 17, and a DC power supply 16, and is different from the reference voltage generation circuit shown in FIG. 1 in terms of the number of variable resistors and adjustment points. It has decreased significantly. The relative ratio of the reference voltages V ₁ to _{V 4} of this reference voltage generation circuit 15 is determined by the resistance R ₁₉
~ R ₂₄ is constant. The absolute value of V ₁ to _{V 2} can be set by a variable resistor 17.
The variable resistor 17 also has the function of adjusting the coupling degree of the coupling detection circuit 11 or the variation in the loss of a circuit that may be connected to the subsequent stage of the transmission output terminal C. However, as in Figure 1, the detection voltage
The relationship between Vd and √ ₀ is not proportional due to the nonlinearity of the diode used in the rectifier and smoothing circuit 12. Therefore, in the reference voltage generation circuit 15 of this example, all of the reference voltages V ₁ to V ₄ can be accurately adjusted by adjusting one variable resistor, no matter how the values of the resistor groups 19 to 20 are combined. The disadvantage is that it is difficult to correct.

The purpose of this invention is to solve the above drawbacks by applying a bias voltage to the diode of the rectifying and smoothing circuit and detecting a DC voltage proportional to the square root of the transmitting output power. An object of the present invention is to provide a multi-stage variable transmission output circuit that can be set in multiple stages.

In order to achieve the above object, the multi-stage transmission output variable circuit according to the present invention is a multi-stage transmission output variable circuit that changes the transmission output in multiple stages, and includes a transmission output detection circuit that detects the transmission output, and an output of the transmission output detection circuit. a rectifying and smoothing circuit that rectifies and smoothes the signal using a diode, and biasing the diode by superimposing a DC voltage on the output of the transmitting output detecting circuit, and biasing the diode in a region with a good rise characteristic of the V-I characteristic. A DC power supply to be operated, a voltage generation circuit that generates a voltage obtained by subtracting the voltage drop of the diode from the voltage of the DC power supply, and a differential circuit that subtracts the output voltage of the voltage generation circuit from the output voltage of the rectification and smoothing circuit. , a reference voltage generation circuit that generates at least two or more reference voltages, and one of the reference voltages of this reference voltage generation circuit.
A selection circuit that selects the output voltage, a comparison circuit that compares the reference voltage selected by the selection circuit with the output voltage of the differential circuit, and a circuit that controls the transmission output using the output of the comparison circuit. There is.

According to the above configuration, since a DC voltage proportional to the square root of the transmission output power is output from the differential circuit, all multi-stage transmission outputs can be set accurately with one variable resistor, and the purpose of the present invention is completely achieved. can.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 3 is a circuit diagram showing an embodiment of a multi-stage variable transmission output circuit according to the present invention, in which the number of variables is 4.
This is an example of stages. Output P ₀ of transmission output amplifier 50
is detected by the coupling detection circuit 27, and the rectification and smoothing circuit 2
After passing through 9, the signal is input to the positive input terminal of a differential amplifier 32 composed of resistors 35 and 36 and a differential amplifier 51. The DC voltage of the DC power supply 30 is applied to the rectifying and smoothing circuit 29 via the low-pass filter 28 . Furthermore, a resistor 3 is connected through a diode 53 of the same type as the diode used in the rectifying and smoothing circuit 29.
It is also applied to the positive input terminal of a differential amplifier 31 composed of a differential amplifier 3, 34 and a differential amplifier 52. The output of the differential amplifier 31 is input to the inverting input terminal of the differential amplifier 51 through the resistor 35. DC power supply 4
0, a variable resistor 41, and resistor groups 42 to 48 constitute a reference voltage generating circuit 39. The output of this reference voltage generation circuit 39 is inputted to a differential amplifier 37 through an analog switch selection circuit 38. The analog switch 38 is a selection circuit that connects one of the terminals T ₁ , T ₂ , T ₃ and T ₄ to the terminal T ₀ according to the control data D, and uses a circuit equivalent to μPD40518, for example. The output voltage V ₀ of the terminal T ₀ and the output Vd' of the differential amplifier 32 are compared and amplified by the differential amplifier 37, and the output thereof is input to the power supply current control circuit 49 of the transmission output amplifier 50. The diode 54 of the rectifying and smoothing circuit 29 to which the bias voltage V _B is applied by the DC power supply 30 operates in a region with good rising characteristics among the V-I characteristics of the diode, and its output has a voltage portion proportional to √ ₀ . Contains. On the other hand, the voltage Vc output from the diode 53 is V _B
The voltage is obtained by subtracting the voltage drop of the diode 53 from the voltage. The output voltage of the output P ₀ of the transmitting output amplifier 50 is jointly detected and passed through the rectifying and smoothing circuit 29.
Vd is the sum of the part proportional to √ ₀ and the voltage equal to Vc.

Now, the values of resistors 33, 34, 35, and 36 are
When R ₃₃ , R ₃₄ , R ₃₅ , and R ₃₆ are set so that the relationship R ₃₄ /R ₃₃ = R ₃₆ /R ₃₅ holds, the difference between Vd, Vc and the output Vd' of the differential amplifier 32 is Vd' The following relationship holds: = (1+R ₃₄ /R ₃₃ ) (Vd-Vc), and the previous equation Vd' becomes a voltage proportional to √ ₀ . The comparison output of this voltage Vd' and the reference voltage V ₀ selected by certain control data becomes the negative feedback signal of the transmission output amplifier 50, so P ₀ is Vd'V ₀
It becomes stable at a value of . Therefore, there is a nearly proportional relationship between √ ₀ and the reference voltage V ₀ . on the other hand,
Reference voltage generated by reference voltage generation circuit 39
The ratio of V ₁ , V ₂ , V ₃ and V ₄ is the resistance group 42-48
Determined by the value of . Therefore, the coupling detection circuit 27
Even after adjusting the degree of coupling or the variation in loss in the circuit that may be connected after point C using the variable resistor 41, the rate of change in P ₀ when the reference voltage is switched by the analog switch 38 is does not change. According to this circuit, regardless of the number of output variable stages, accurate setting of each stage's output is possible with only one adjustment point.

As explained in detail above, according to the present invention,
By using a transmission output detection circuit that detects a DC voltage proportional to the square root of the transmission output power and a differential circuit that reduces the DC voltage applied to the detection circuit, it is possible to accurately set several levels of transmission output with one adjustment. There are effects that can be done.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing a conventionally used multi-stage transmission output variable circuit, and FIG. 3 is a circuit diagram showing an embodiment of the multi-stage transmission output control circuit according to the present invention. A...Power input, B...Transmission signal input, C...
Transmission signal output, D...Transmission output control signal, P ₀ ...
…Transmission output, V _B …Bias DC voltage, Vc…
... Output voltage of diode 53, Vd ... Output voltage of rectifier and smoothing circuit, Vd' ... Output voltage of differential amplifier 32, V ₀ ... Output voltage of analog switch 38,
V ₁ , V ₂ , V ₃ , V ₄ ... Reference voltage generated by the reference voltage generation circuit, T ₀ ... Output terminal of analog switch 38, T ₁ , T ₂ , T ₃ , T ₄ ... Analog switch 38
input terminals, 1, 11, 27...coupling detection circuit (transmission output detection circuit), 2, 12, 29... rectifying and smoothing circuit, 3, 13, 31, 32... differential amplifier,
4, 15, 39...Reference voltage generation circuit, 5, 1
4, 38...Analog switch (selection circuit), 6
...Resistance group, 7...Variable resistance group, 8, 16, 3
0,40...DC power supply, 9,25,49...Power supply current control circuit, 10,26,50...Transmission output amplifier, 17,41...Variable resistor, 18-24,3
3, 34, 35, 36, 42 to 48, 51...Resistor, 28...Low pass filter, 37...Comparison circuit.

Claims (1)

[Scope of utility model registration request] A multi-step transmission output variable circuit that changes transmission output in multiple steps includes a transmission output detection circuit that detects transmission output, a rectification and smoothing circuit that rectifies and smoothes the output of the transmission output detection circuit using a diode, and the transmission output detection circuit. A DC power supply that biases the diode by superimposing a DC voltage on the output of the circuit and operates the diode in a region with good rising characteristics among the V-I characteristics, and a voltage drop of the diode from the voltage of this DC power supply. a voltage generation circuit that generates a voltage obtained by subtracting the voltage, a differential circuit that subtracts the output voltage of the voltage generation circuit from the output voltage of the rectification and smoothing circuit, and a reference voltage generation circuit that generates at least two or more reference voltages; a selection circuit that selects one of the reference voltages of the reference voltage generation circuit; a comparison circuit that compares the reference voltage selected by the selection circuit with the output voltage of the differential circuit; 1. A multi-stage transmission output variable circuit comprising: a circuit for controlling transmission output using the output.