JPH08228182A - Tdma wave output circuit and tdma communication equipment using same - Google Patents

Abstract

PURPOSE: To suppress modulation output signals without using a PIN switch by interrupting the bias current of the final output stage of the modulation output signals. CONSTITUTION: The final output stage of the modulation output signals is a differential circuit constituted of transistors Q1 and Q2 and the primary winding of a transformer T is connected between the collector terminals in the two transistors Q1 and Q2. A power source is connected to the middle point tap of the primary winding of the transformer T and time bias current is supplied through the middle point tap and the primary winding to the respective transistors Q1 and Q2. Thus, magnetic fluxes by the bias current are cancelled inside the transistor T and the magnetic fluxes are not generated. Thus, even when bias power is rapidly turned to 0, a spike voltage is not generated and unrequired radio waves are prevented from being outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TDMA wave output circuit. In particular, the present invention relates to a TDMA wave output circuit that outputs a TDMA wave with a small leak signal to the side band without using a PIN switch.

[0002]

2. Description of the Related Art TDMA (Time Domain M)
The multiple access communication system is widely used in the field of CATV as well as mobile communication and satellite communication. The TDMA communication system is a communication system in which each station outputs a signal compressed into a high-speed burst so as not to overlap in time, and a plurality of stations share one band. The time when one burst wave is output is called a time slot, and each station outputs a burst wave in the time slot assigned to itself.

FIG. 5 is an explanatory diagram showing the state of burst waves in one time slot in such a TDMA communication system. As shown in FIG. 5, this burst wave has a sinusoidal envelope. This is to reduce unnecessary radiation to the sideband. For example, in CATV or the like, the bandwidth of the communication channel is the center frequency ± 3 Mhz. Therefore, the maximum frequency of the burst wave envelope in one time slot shown in FIG.
Must be less than or equal to Mhz.

Next, the structure of the output stage of the communication device used in such a TDMA communication system will be described. Figure 6
Shows a block diagram of the configuration of the output stage of such a communication device. As shown in FIG. 6, the final modulated signal is supplied to the bandpass filter 12 via the PIN switch 10. The bandpass filter has a passband width set in accordance with the above-described bandwidth.

The reason why the PIN switch 10 is used is to set the output signal to zero in a time slot other than the time slot assigned to the own station. That is, at times other than the time slot assigned to the own station, the signal output is normally set to zero by setting the modulation signal to zero, but it is set to zero completely due to variations in each component. Is difficult. Therefore, the PIN switch 10 is used to prevent the modulated signal from being sent to the bandpass filter 12.

As a result, the waveform of one burst wave does not actually have the shape shown in FIG. 5 but has the shape shown in FIG. As shown in FIG. 7, the amplitude of the burst wave is forced to zero outside the time slot.

[0007]

However, the PIN switch 10 cannot be incorporated in an IC because of its structure. Therefore, the modulation signal must be supplied to the external PIN switch 10 after being generated by the balanced modulation circuit inside the IC.

Therefore, since a means equivalent to the switch means such as the PIN switch 10 is incorporated in the IC, a configuration as shown in FIG. 8 is also conceivable.
FIG. 8 shows an example in which an inductance is provided on the collector side of the output transistor, and the output is forcibly set to zero by setting the bias current of the output transistor to zero. However, at the time of normal output, a bias current is flowing in the transistor shown in FIG. 8, and abruptly cutting off this bias current causes a large spike voltage in the inductance shown in FIG. Signals of frequency components other than the frequency band assigned to the station will leak to the outside.

Therefore, generally, as described above, the output signal is cut off by the external PIN switch 10 without changing the bias current of the transistor inside the IC (shown in FIG. 8).

As a result, the bias current of the transistor in the output stage continues to flow in the period other than the time slot assigned to the local station. This is a portable communication device such as a pager, mobile phone or C
In a communication device driven or backed up by a battery such as a telephone using an empty channel of ATV, it means an increase in power consumption. As a result, the operating time of portable communication devices and the like is reduced, which hinders the utilization of communication devices.

The present invention has been made in view of the above problems, and an object thereof is to provide a communication device which satisfies the following requirements.

(1) To provide a communication device that suppresses modulation output without using a PIN switch.

(2) To provide a communication device capable of suppressing a residual output by cutting off a bias current of a transistor in an output stage without causing unnecessary leakage of a signal in a side band.

According to such a communication device, it is possible to obtain a communication device having a small size and a simple structure, reduce the power consumption of the battery-driven communication device, and expect an increase in continuous operation time.

[0015]

In order to achieve the above-mentioned object, a first invention of the present invention is a TDMA for amplifying a TDMA wave signal.
A wave output circuit is a TDMA wave output circuit having the following configuration.

That is, a primary amplifier is provided between a differential amplifier circuit which has two differentially connected transistors and amplifies an input signal, and the output terminals of the two transistors which form the differential amplifier circuit. Bias currents of the two transistors forming the differential amplifier circuit and the transformer connected to the winding and having a power source connected to the center tap of the primary winding are converted into signals from the outside. And a bias current cutoff circuit that cuts off based on the above. A bias current flows from the power supply connected to the center tap of the transformer to the two transistors forming the differential amplifier circuit via the primary winding, and the secondary winding of the transformer is formed. The output signal is taken out from.

In order to achieve the above object, a second invention of the present invention is a TDMA communication device which employs the TDMA wave output circuit of the first invention of the present invention as a final output stage, and has the following configuration. .

That is, the bias current cut-off circuit is controlled so that a bias current is caused to flow through the two transistors forming the differential amplifier circuit only in a time slot for transmitting a burst wave which is a TDMA wave, and other than that. In the time slot of, a bias current switching circuit for interrupting the bias current is provided.

[0019]

In the transformer of the first aspect of the present invention, the bias currents flow in the opposite directions via the center tap. Therefore, the magnetic flux in the transformer due to the bias current is zero. Therefore, even if the bias current cutoff circuit cuts off the bias current, the magnetic flux in the transformer does not change, and the spike voltage is not generated.

The bias current switching circuit according to the second aspect of the present invention causes the bias current to flow only in the time slot in which the communication device transmits the burst wave. for that reason,
Conventionally, the bias current was flowed during the entire communication period, whereas the bias current flow was 1
It can be suppressed to about / 25 to 1/30.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows T which is a preferred embodiment of the present invention.
A partial block diagram of the output block of the DMA communication device is shown. As shown in FIG. 1, the characteristic feature of this embodiment is that the output stage is composed of a differential circuit. Furthermore, the primary winding of the transformer T is connected to the collector terminals of the two transistors Q1 and Q2 that form the differential circuit. The power supply voltage V is applied to the center tap of the primary winding of the transformer T.
cc has been supplied. That is, the transistor Q1,
The bias currents I1 and I2 of Q2 are supplied through the center tap of the transformer T and the primary winding, respectively.

The transformer T according to this embodiment is a bifilar winding transformer, and a bias current I is applied to the primary winding.
Since 1 and I2 respectively flow in opposite directions, a DC magnetic flux due to this bias current does not occur. Therefore, even if the bias current is suddenly cut off, the RF output spectrum is not affected. Thus, in this embodiment,
Since the bias current is supplied through the primary winding of the transformer, the bias current can be rapidly turned on / off.
As a result, it is possible to configure a communication device with low power consumption without using a PIN switch which has been conventionally required.

As shown in FIG. 1, in this embodiment, the output signal is taken out from the secondary winding of the transformer T. Two transistors Q that make up a differential circuit
The emitter terminals of 1 and Q2 are commonly connected, and are connected to the collector terminal of a transistor Q3 for current control. Also, the two transistors Q that make up the differential circuit
Between the input terminals of 1 and Q2, that is, between the base terminals, a frequency selection circuit for cutting harmonics generated in the modulation circuit is provided.

As shown in FIG. 1, the emitter terminal of the transistor Q3 for controlling the current is grounded via the resistor R3. The base terminal of the transistor Q3 is connected to the anode terminal of the diode D1.
The cathode terminal of the diode D1 is grounded via the resistor R2. That is, the diode D1 and the transistor Q3 form a so-called current mirror circuit, and a substantially constant current I0 flows through the transistor Q3 and the resistor R3.

The current flowing through the transistor 3 is proportional to the current flowing through the diode D1.
By controlling the current flowing through 1, it is possible to control the bias current of the differential circuit. As shown in FIG. 1, the circuit including the resistor R1, the capacitor C1, and the variable resistor Rv controls the bias current of the differential circuit by changing the current flowing through the diode D1.

For example, as shown in FIG. 1, when the control input signal is grounded, no current flows through the diode D1 and no current flows through the transistor Q3. Therefore, the bias current in the differential circuit becomes 0, and the output signal becomes 0 completely.

Next, when a signal having an appropriate voltage is applied as the control input signal, the resistor R1 and the capacitor C1 are applied.
The voltage signal that rises smoothly by the diode D
1 is applied. This applies a bias with a rising CR charge curve to transistor Q3,
The collector current I0 of the transistor Q3 is 0 to 1-e
^{-Increase to τ / t} . Since the gain of the differential circuit shown in FIG. 1 is proportional to its bias current I0, the RF signals applied to the input 1 and the input 2 shown in FIG. 1 are almost similar to the waveform of I0. The signal having the above envelope is output via the transformer T.

When the control input signal is grounded again, the bias current I0 decreases like a CR discharge curve due to the time constants of the resistor R1 and the capacitor C1. Along with this, the final output RF signal also decreases.

As described above, even if the control input signal is changed and the bias current I0 of the differential circuit is changed, the magnetic flux due to the bias current is not generated in the core of the transformer T of the bifilar winding as described above. Unnecessary power due to the change of is not output. In this way, even if the bias current I0 changes, no unnecessary power is output, so the bias current I0 can be freely changed. Therefore, it is possible to significantly reduce the power consumption by causing the bias current I0 to flow only in the time slot assigned to the own station.

Further, since the maximum value of the bias current I0 can be set by adjusting the variable resistor Rv, the output power can be easily adjusted. An explanatory diagram showing the envelope of the burst wave by the final output stage shown in FIG. 1 is shown in FIG.
It is shown in (a). FIG. 3A shows a time chart showing the state of the envelope of the control input signal and the output signal corresponding to the control input signal. For example, if the control input signal is a signal that rises from 0 V to 5 V, the envelope of the output signal rises smoothly according to the time constant determined by the resistor R1 and the capacitor C1, as shown in FIG. 3 (a). And, it will fall smoothly.

It is also preferable that the change in the envelope of the output signal with respect to the control input signal has another characteristic. The case where the characteristics are different will be described below.

FIG. 2 is a circuit diagram showing the structure of the output stage of the differential circuit which is almost the same as that shown in FIG. Also in the circuit shown in FIG. 2, the final output stage is composed of a differential circuit including transistors Q1 and Q2, and a primary winding is connected between the collector terminals of the transistors Q1 and Q2 that form the differential circuit. It is equipped with a transformer T. Further, since the bias current is supplied through the middle point tap of the transformer T, even if the bias current is changed, unnecessary power does not appear in the output signal, and the same effect is obtained.

The circuit shown in FIG. 2 is different from the circuit shown in FIG. 1 because of the control input signal.
3 is a circuit configuration of a portion that controls a bias current.

When the control input signal is, for example, 5 volts, the transistor Q5 is turned on and only a low applied voltage appears in the diode D1. As a result, the bias current becomes almost zero. Next, when the control input signal changes from 5 V to 0 V, the electric charge stored in the capacitor C1 is discharged through the resistors R4, R5 and R6. Therefore, the transistor Q5 gradually shifts to the OFF differential, and the bias current also changes to the capacitor C.
1, and gradually increases according to the time constant determined by the resistors R4, R5, and R6. Then, when the control input signal changes from 0 volt to 5 volt next time, the transistor Q5 smoothly shifts to the ON operation with a constant time constant by the action of the capacitor C2, the resistor R6 and the diode D2. As a result, the bias current of the differential circuit can be smoothly reduced.

The operational difference between the circuit shown in FIG. 1 and the circuit shown in FIG. 2 is apparent from the time charts shown in FIGS. 3 (a) and 3 (b). Let's do it. That is, FIG. 3A (operation of the circuit shown in FIG. 1)
As you can see, when the burst wave disappears,
The amplitude decreases sharply from the maximum amplitude and then gradually decreases to gradually decrease to zero.
On the other hand, as understood from FIG. 3B (which represents the operation of the circuit shown in FIG. 2), when the amplitude of the burst wave decreases, the burst wave starts slowly from the position of the maximum amplitude. When the amplitude is close to 0, the degree of decrease in the amplitude value becomes stronger. As described above, the difference between the circuit shown in FIG. 1 and the circuit shown in FIG. 2 is that the change in the amplitude of the burst wave is large in the portion close to the maximum amplitude, or the amplitude value is close to zero. Sometimes it's a big difference. Generally, it is considered that unnecessary power is less likely to appear in the output signal by smoothing the amplitude change when the amplitude of the burst wave is large. Therefore, the circuit shown in FIG. 2, that is, shown in FIG. It can be said that the circuit that performs the operation described above does not output unnecessary power.

As described above, in any of the circuits shown in FIGS. 1 and 2, the bias current in the final output stage can be changed without outputting unnecessary radio waves.
It is not necessary to provide a PIN switch or the like outside the IC package, and unnecessary radio waves are not output. As a result, the size and weight of the device can be reduced and the power consumption can be reduced.

In the above-mentioned configuration, FIG. 1 and FIG.
The bias current was cut off by turning off the transistor Q3 at. However, even in this case, the input modulated wave signal may leak to the output. For this reason, it is preferable to employ a circuit configuration as shown in FIG. 4, for example, in order to complete the interruption. The circuit shown in FIG. 4 uses the differential circuit constituted by the transistors Q1 and Q2 as the final output stage similarly to the circuits shown in FIGS. In the circuit shown in FIG. 4, a characteristic is that when the bias current is cut off, that is, the transistor Q3 is turned off,
When the X point shown in FIG. 4 becomes floating,
That is, the transistor Q6 that is turned on is provided. As shown in FIG. 4, a resistor R7 is provided between the X point and the power supply, and the X point side of the resistor R7 is connected to the transistor Q6 base terminal. The emitter terminal of the transistor Q6 is connected to the base terminal of the transistor Q1, and the modulated wave signal is applied to the emitter terminal of the transistor Q6 together with the base terminal of the transistor Q1 which is one of the transistors forming the differential circuit. To be done. The collector terminal of the transistor Q6 is a resistor R8.
And is grounded via a capacitor C3. With such a configuration, when the transistor Q3 is turned off by the control input signal and the point X in FIG. 4 is in a floating state to cut off the signal, the transistor R6 is turned on by the resistor R7 at the same time. By doing so, it becomes possible to lead the input signal to the ground via the capacitor C3. This makes it possible to more completely prevent the input signal from appearing in the output signal.

On the other hand, when the transistor Q3 is conductive and the differential circuit composed of the transistors Q1 and Q2 operates as an amplifier, the transistor Q6.
Between the base-emitter terminals of
Since it is reverse-biased by (base rising voltage), it does not affect the amplifying operation of the differential circuit at all.

As described above, according to the present embodiment, the final output stage of the modulation signal is constituted by the differential circuit, and the bias current is supplied to the two transistors constituting them through the primary winding of the transformer. . As a result, it became possible to change the bias current without outputting unnecessary power to the output signal. As a result, since the PIN switch is not used, the size and weight of the device can be reduced and the power consumption of the device can be reduced.

[0041]

As described above, according to the first aspect of the present invention, since the bias current supplied to the differential amplifier circuit is supplied through the primary winding of the transformer, unnecessary power is not leaked to the output. , It is possible to change the magnitude of the bias current. As a result, it is possible to obtain a TDMA wave output circuit that realizes a simple configuration and can reduce power consumption.

According to the second aspect of the present invention, since the bias current is flown only in the time slot in which the burst wave is to be transmitted, it is possible to obtain the TDMA wave communication device capable of achieving higher power consumption.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a TDMA wave output circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a TDMA wave output circuit according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing waveforms of control input signals and output signals of the TDMA wave output circuit shown in FIGS. 1 and 2.

FIG. 4 is a circuit diagram of a TDMA wave output circuit according to another embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a state of a burst wave in one time slot in the TDMA wave communication system.

FIG. 6 is an explanatory diagram of a configuration of an output stage of a communication device used in the TDMA wave communication system.

FIG. 7 is an explanatory diagram showing a waveform of a burst wave in an actual communication device.

FIG. 8 is a circuit diagram in the case where an inductance is provided on the collector side of the output transistor and the modulation signal is set to 0 to force the output signal to 0.

[Explanation of symbols]

Q1, Q2, Q3 transistors, I1, I2, I0
Bias current, R1, R2, R3 resistors, T transformer, C1 capacitor, D1 diode, Rv variable resistor.

Claims (2)

[Claims] 1. A TDMA wave output circuit for amplifying a TDMA wave signal, the differential amplifier circuit having two differentially connected transistors for amplifying an input signal, and 2 constituting the differential amplifier circuit. A primary winding is connected between the output terminals of the transistors, and a transformer in which a power source is connected to the center tap of the primary winding, and two transformers forming the differential amplifier circuit. A bias current cutoff circuit that cuts off the bias current of the transistor based on a signal from the outside; and, from the power supply connected to the midpoint tap of the transformer, through the primary winding of the transformer. A TDMA wave output circuit, wherein a bias current flows through the two transistors forming the differential amplifier circuit, and an output signal is taken out from the secondary winding of the transformer. 2. A TDMA communication device that employs the TDMA wave output circuit according to claim 1 as a final output stage, wherein the bias current cutoff circuit is controlled and the burst wave that is a TDMA wave is transmitted only in the time slot. A TDMA communication device, comprising: a bias current switching circuit that causes a bias current to flow through the two transistors that form a differential amplifier circuit, and that shuts off the bias current in other time slots.