JPH05235797A - Transmitter-receiver for ping-pong transmission - Google Patents

Abstract

PURPOSE:To increase a dynamic range of a reception signal by setting properly a prescribed voltage so as to avoid the saturation of an inverting amplifier means even when the intensity of an incident light is strong. CONSTITUTION:A voltage control means 14 is connected in parallel with a feedback resistor 132 of an inverting amplifier means 13 so that a forward direction is coincident with a feedback direction of the inverting amplifier means 13 and active when an output voltage of the inverting amplifier means 13 exceeds a prescribed voltage to limit the output voltage to the prescribed voltage. In this case, when the intensity of a light made incident on a light emitting/light receiving means 11 is weak, the output voltage of the inverting amplifier means 13 is a product between a current outputted from the light emitting/light receiving means 11 and the resistance of the feedback resistor 132. On the other hand, when the intensity of the incident light is strong and the output voltage of the inverting amplifier means 13 exceeds the prescribed voltage, the voltage control means 14 is active. Thus, the output voltage of the inverting amplifier means 13 is limited to the prescribed voltage in this case.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitter / receiver in a ping-pong transmission system which executes transmission and reception in a time-division manner so that transmission and reception timings do not overlap.

In recent years, in various communication networks,
Optical communication using optical fibers is being promoted with the increase in speed and diversification of information services.

However, in the optical communication, the cost of the light emitting element and the light receiving element is high, so that there is a drawback that the cost is higher than that of the conventional electric communication using the metallic wire.

Therefore, in order to proceed with optical communication, it is necessary to reduce the cost of the light emitting element and the light receiving element.

[0005]

2. Description of the Related Art In order to deal with this problem, the applicant of the present patent application, "The Institute of Electronics and Communication Engineers IN85-104: Prototype for optical ping-pong transmission system", "The Institute of Electronics and Communication Engineers IN84-"
38: Consideration of optical bidirectional transmission system ", a ping-pong transmission type transceiver that uses a light emitting diode as a light emitting element and a light receiving element was proposed.

FIG. 5 is a block diagram showing the configuration of the transmitting / receiving apparatus described in the above-mentioned document.

In the transmitter / receiver shown in the figure, the light emitting diode 4 is current-driven by the wide band amplifier circuit 2 and the transistor 3 based on the level of the transmission signal supplied to the input terminal 1 during transmission.

As a result, light having an intensity corresponding to the level of the transmission signal is output from the light emitting diode 4, and transmission by light is executed.

On the other hand, at the time of reception, a current having a level corresponding to the light received from the light emitting diode 4 is output.

This current is amplified by a parallel feedback parallel injection type (transfer impedance type) anti-phase amplifier circuit 5 and output from an output terminal 6.

With this structure, since the light emitting diode 4 is on a mass production level, it is possible to reduce the price of the transmitting / receiving device.

However, in this transmission / reception apparatus, the output voltage of the anti-phase amplifier circuit 5 is obtained by multiplying the current flowing through the light emitting diode 4 by the resistance value of the feedback resistor 51, so that the light incident on the light emitting diode 4 is detected. However, there is a drawback that the reverse phase amplifier circuit 5 is saturated when the strength of the signal becomes stronger.

Therefore, this transmitter / receiver has a problem that the dynamic range of the received signal cannot be made large.

[0014]

[Problems to be Solved by the Invention]

As described above, the conventional ping-pong transmission transmitter / receiver in which the light emitting diode serves as both the light emitting element and the light receiving element has a problem that the dynamic range of the received signal cannot be widened.

Therefore, an object of the present invention is to provide a ping-pong transmission transmitter / receiver capable of increasing the dynamic range of a received signal.

[0017]

FIG. 1 is a block diagram showing the principle configuration of the present invention.

In the figure, reference numeral 11 denotes a light emitting / receiving means for emitting light having an intensity corresponding to the level of a flowing current and outputting a current having a level corresponding to the intensity of the received light.

Reference numeral 12 is a transmission drive means for driving the light emitting / light receiving means 11 with a current having a level corresponding to the level of the transmission signal during transmission.

Reference numeral 13 is a parallel feedback parallel injection type anti-phase amplifying means for amplifying the current output from the light emitting / receiving means 11 according to the intensity of the received light during reception.

Reference numeral 14 is connected in parallel to the feedback resistor 132 of the anti-phase amplifying means 13 so that the forward direction matches the feedback direction of the anti-phase amplifying means 13, and the output voltage of the anti-phase amplifying means 13 is a predetermined voltage. When the voltage exceeds the threshold voltage, it becomes an operating state, and is a voltage limiting means for limiting the output voltage to the above-mentioned predetermined voltage.

Reference numeral 15 is a breaking means for forcibly setting the voltage limiting means 14 in the cutoff state during transmission.

[0023]

In the above structure, when the intensity of the light incident on the light emitting / receiving means 11 during reception is weak, the output voltage of the anti-phase amplifying means 13 is equal to the current output from the light emitting / receiving means 11. It is multiplied by the resistance value of the feedback resistor 132.

On the other hand, when the intensity of the incident light becomes strong and the output voltage of the anti-phase amplifying means 13 exceeds the predetermined voltage, the voltage limiting means 14 is activated.

As a result, in this case, the reverse phase amplification means 1
The output voltage of 3 is limited to the above predetermined voltage.

Therefore, according to the present invention, by appropriately setting the above-mentioned predetermined voltage, it is possible to prevent the anti-phase amplifying means 13 from being saturated even if the intensity of the incident light becomes strong.

Thus, according to the present invention, the dynamic range of the received signal can be widened.

Moreover, the voltage limiting means 14 is set to the cutoff state by the cutoff means 15 during transmission.

Thus, despite the provision of the voltage limiting means 14, it is possible to prevent a large leakage current from flowing from the feedback loop of the anti-phase amplifying means 13 to the transmission driving means 12 during transmission.

[0030]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention.

First, the configuration of FIG. 2 will be described.

In the figure, reference numeral 21 designates a light emitting diode which serves as both a light emitting element and a light receiving element.

Reference numeral 22 is an input terminal to which a transmission signal of a transistor transistor logic (hereinafter referred to as "TTL") level is supplied.

Reference numeral 23 is a wideband amplifier circuit for amplifying the transmission signal supplied to the input terminal 22.

Reference numeral 24 is a voltage / current conversion circuit which converts the output voltage of the wide band amplifier circuit 23 into a current and drives the light emitting diode 21 by this current.

Reference numeral 25 is a parallel feedback parallel injection type anti-phase amplifier circuit for amplifying the current output from the light emitting diode 21 according to the intensity of the received light.

Reference numeral 26 is an output terminal of the reception signal output from the anti-phase amplifier circuit 25.

The above is the basic configuration of the apparatus shown in FIG. Next, the characteristic configuration of the present invention will be described.

In the figure, 27 is a diode for limiting the output voltage of the anti-phase amplifier circuit 25 to a predetermined voltage.

The diode 27 is connected in parallel to the feedback resistor 253 of the anti-phase amplifier circuit 25 such that its forward direction coincides with the feedback direction of the anti-phase amplifier circuit 25.

The amplification section of the anti-phase amplification circuit 25 is composed of a parallel feedback parallel injection type positive phase amplification section 251 and a parallel feedback parallel injection type anti-phase amplification section 252, and is combined as a whole with a feedback resistor 253. The negative phase amplifier circuit 25 is configured.

In this case, the positive phase amplifier 251 is arranged on the front side, and the negative phase amplifier 252 is arranged on the rear side.

The positive phase amplifying section 251 is provided to secure the gain of the amplifying section, and its output terminal is connected to the output terminal 26 of the above-mentioned received signal.

On the other hand, the anti-phase amplifier 252 is provided to set the diode 27 in the cutoff state, and its gain is set to about "1".

Reference numeral 28 is a control terminal to which a control signal for controlling the output voltage of the anti-phase amplifier 252 is supplied.

The above is the characteristic configuration of the present invention.

The voltage / current conversion circuit 24 includes an operational amplifier 241, a transistor 242, an emitter resistor 243, temperature compensating diodes 244 and 245, and
It is configured by a constant voltage source 246.

Here, the non-inverting input terminal of the operational amplifier 241 is connected to the output terminal of the wide band amplifier circuit 23. The inverting input terminal is connected to the negative terminal of the constant voltage source 246. The output terminal is the transistor 2
It is connected to the base of 42.

The collector of the transistor 242 is connected to the cathode of the light emitting diode 21. Also,
The emitter is connected to one end of the emitter resistor 243.

The other end of the emitter resistor 243 is connected in the forward direction with diodes 244 and 245 connected to direct current,
It is connected to the negative terminal of the constant voltage source 246. The positive terminal of the constant voltage source 246 is grounded.

In addition, the positive phase amplifier 251 is the operational amplifier 1
A, resistors 2A and 4A, and a constant voltage source 3A.

Here, the non-inverting input terminal of the operational amplifier 1A is connected to the cathode of the light emitting diode 21.
Further, the inverting input terminal is connected to the constant voltage source 3A via the resistor 2A.
Is connected to the positive terminal of.

The negative terminal of the constant voltage source 3A is grounded. The output terminal of the operational amplifier 1A is the output terminal 2
6 and is also connected to the inverting input terminal via the feedback resistor 4A.

Further, the anti-phase amplifying section 252 has the operational amplifier 1
B and resistors 2B to 5B.

Here, the inverting input terminal of the operational amplifier 1B is connected to the output terminal of the operational amplifier 1A via the resistor 2B and to the control terminal 28 via the resistor 4B.

The non-inverting input terminal is grounded via the resistor 3B. The output terminal of the operational amplifier 1B is connected to the inverting input terminal via the feedback resistor 5B, and is also connected to the cathode of the light emitting diode 21 via the parallel circuit of the feedback resistor 253 and the diode 27.

The above is the configuration of FIG. Next, the operation of this transmission / reception device will be described.

First, the basic operation during transmission will be described.

The TTL level transmission signal supplied to the input terminal 22 is amplified by the wide band amplification circuit 23, and then,
It is supplied to the base of the transistor 242 via the operational amplifier 241.

As a result, the transistor 242 is in the ON state while the transmission signal is at the high level, and is in the OFF state during the low level.

When the transistor 242 is turned on,
The collector current I _{1 of the} transistor 242 flows through the light emitting diode 21.

As a result, a forward current flows through the light emitting diode 21, and the light emitting diode 21 emits light.

On the other hand, no forward current flows through the light emitting diode 21 while the transistor 242 is off. As a result, the light emitting diode 21 stops emitting light during this period.

From the above, during transmission, the light emitting diode 21 blinks based on the level of the transmission signal. As a result, the transmission signal is sent as an optical signal to the opposite station via an optical fiber (not shown).

Assuming that the forward voltage drop of the light emitting diode 21 is 2V, when the transistor 242 is in the ON state, the potential at point P in the figure (the cathode potential of the light emitting diode 21, in other words, the input potential of the anti-phase amplifier circuit 25). ) V _P
Is approximately −2V. In contrast, the transistor 24
When 2 is off, it is almost 0V.

This state is shown in FIG. Note that FIG.
(A) shows V _P as an eye pattern.

The above is the basic operation during transmission. Next, the basic operation during reception will be described.

In this case, the potential V _{P at the} point P shown in FIG.
As shown in (a), it is always 0V.

In this state, when the light emitting diode 21 receives light, the reverse current I flows through the light emitting diode 21.
₂ flows.

This reverse current I ₂ is applied to the reverse phase amplifier circuit 25.
Since its input impedance is large, it almost flows to the feedback resistor 253.

As a result, the potential V at the point Q in the figure_Q(Inverse phase increase
The output potential of the width circuit 25) is the current I ₂And feedback resistor 253
Resistance value R_fIt will be multiplied by. This state is shown in Figure 4.
It shows in (b).

On the other hand, the light emitting diode 21 receives light.
When it does not occur, the reverse current I is applied to the light emitting diode 21.
₂Does not flow. Therefore, in this case,
Rank V _QBecomes 0V.

When the reverse current I ₂ flows, the output voltage of the positive phase amplifier 251 becomes a negative voltage obtained by adding the voltage drop of the resistors 2A and 4A to the output voltage of the constant voltage source 3A.

On the other hand, when the reverse current I ₂ does not flow, the output voltage of the positive phase amplifier 251 becomes 0V.

As a result, the received signal is taken out from the output terminal 26 as a negative signal.

The above is the basic operation upon reception. next,
The characteristic operation of the present invention will be described.

During reception, the reverse current I ₂ flowing through the light emitting diode 21 changes according to the intensity of the received light.

That is, when the light is strong, the reverse current I ₂ becomes large, and when the light is weak, the reverse current I ₂ becomes small.

When the reverse current I ₂ is small, the voltage V _Q
Does not exceed the forward drop voltage V _D1 of the diode 27.

Accordingly, in this case, the diode 27
But since not turned on, the potential V _Q shown point Q becomes multiplied by the resistance value R _f of the feedback resistor 253 to the reverse current I _2.

On the other hand, when the reverse current I ₂ becomes large and the potential V _Q exceeds the forward drop voltage V _D1 of the diode 27, the diode 27 is turned on.

As a result, in such a case, the potential V _{Q at the} point _Q in the figure is the diode 2 as shown in FIG. 4 (c).
Limited to a forward drop voltage V _D1 of 7.

From the above, in the configuration of FIG. 2, even when the light emitting diode 21 receives strong light, the anti-phase amplifier circuit 25 does not saturate, so that the dynamic range of the received signal can be widened as compared with the conventional case. ..

However, by inserting the diode 27, the leakage current flowing from the negative feedback loop of the anti-phase amplifier circuit 25 into the transistor 242 of the drive circuit 24 during transmission becomes large.

When the leakage current becomes large, the load of the transistor 242 becomes large and a noise signal is superimposed on the transmission signal.

Therefore, when the receiving dynamic range is widened by the above configuration, it is necessary to take measures against the leakage current as described above.

Therefore, in this embodiment, the anti-phase amplifier circuit 25 is used.
The two-stage amplifying section is composed of a positive phase amplifying section 251 and a negative phase amplifying section 252, and the negative phase amplifying section 252 has a function of blocking (turning off) the diode 27.

That is, the control terminal 28 connected to the inverting input terminal of the operational amplifier 1B of the anti-phase amplifier 252 is supplied with a high level control signal during transmission and is supplied with a low level control signal during reception. It

As a result, the output potential of the anti-phase amplifier 252 (the output potential of the anti-phase amplifier circuit 25), that is, the potential V _{Q at the} point Q in the figure becomes 0 V at the time of reception and at the time of transmission, as shown in FIG.
As shown in (c), it becomes a negative potential V _Q1 .

Therefore, the circuit constant is set so that the negative potential V _Q1 becomes lower than −2 V which is the input potential (potential V _{P at the} point P in the figure) of the anti-phase amplifier circuit 25 when the transistor 242 is in the ON state. If set, during transmission, diode 2
7 can be set to the cutoff state.

When the above setting is made, Q in the figure
No current flows from the point to the point P in the figure through the feedback resistor 253.

As a result, at the time of transmission, it is possible to completely prevent the leak current flowing from the feedback loop into the transistor 242.
It is possible to prevent the increase of the load of 2 and the superposition of the noise signal on the transmission signal.

According to this embodiment described in detail above, the following effects can be obtained.

(1) Since the diode 27 limits the output voltage (V _P ) of the anti-phase amplifier circuit 25 to within the forward drop voltage V _{D1 of the} diode 27, the light emitting diode 21 receives the light when receiving. Even when the intensity of the incident light is high, it is possible to prevent the reverse phase amplifier circuit 25 from being saturated.

As a result, the dynamic range of the received signal can be widened conventionally.

(2) Further, since the diode 27 is forcibly set to the cut-off state during transmission, it is possible to prevent the load of the transistor 242 from increasing due to leakage current and the noise signal from being superimposed on the transmission signal. ..

(3) Since the diode 27 is reverse biased as a method of shutting off the diode 27, not only the leakage current flowing through the diode 27 can be blocked but also the feedback resistor 2
Leakage current flowing through 53 can also be blocked.

As a result, the leakage current flowing into the transistor 242 from the negative feedback loop of the anti-phase amplifier circuit 25 can be completely blocked.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to this embodiment.

(1) For example, in the above embodiment, the diode 27 is reverse-biased so that the diode 2
The case where 7 is set to the cutoff state has been described.

However, according to the present invention, the diode 27 may be set to the cutoff state by applying a forward bias smaller than the forward voltage drop V _D1 to the diode 27.

According to such a configuration, the feedback resistor 253
Although the leakage current flows through the leakage current, the leakage current is small, so that there is no problem in practical use when the influence of the leakage current can be allowed to some extent.

(2) In the above embodiment, the diode 2 is controlled by controlling the output voltage of the anti-phase amplifier circuit 25.
7 has been described.

However, in the present invention, the diode 27 may be set to the cutoff state by setting the feedback loop of the anti-phase amplifier circuit 25 to the open state by using a switch, for example.

(3) In the previous embodiment, the case has been described in which the positive phase amplifier 251 is arranged in the preceding stage and the negative phase amplifier 252 is arranged in the latter stage.

However, according to the present invention, conversely, the positive phase amplifying section 2
51 may be arranged in the latter stage, and the anti-phase amplifier 252 may be arranged in the former stage.

However, in the case of such a configuration, the receiving sensitivity of the anti-phase amplifier circuit 25 may decrease.

In order to solve this problem, for example, it is conceivable to insert a field effect transistor in the input stage of the anti-phase amplifier 252 arranged in the preceding stage.

That is, the gate of the field effect transistor is connected to the cathode of the light emitting diode 21, the source is connected to the inverting input terminal of the operational amplifier 1B, and the drain is grounded via a resistor to negatively bias the drain. .

According to this structure, since the noise signal is absorbed by the field effect transistor, the receiving sensitivity can be improved.

(4) In the previous embodiment, the case where the light emitting diode 21 is used as the light emitting / receiving means 11 has been described, but the present invention may use a laser diode, for example.

(5) In addition to the above, the present invention can be variously modified without departing from the scope of the invention.

[0114]

As described in detail above, according to the present invention,
A ping-pong transmission transmitter / receiver capable of expanding the dynamic range of a received signal can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a principle configuration of the present invention.

FIG. 2 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 3 is a signal waveform diagram for explaining an operation at the time of transmission in one embodiment.

FIG. 4 is a signal waveform diagram for explaining an operation at the time of reception in one embodiment.

FIG. 5 is a block diagram showing a conventional configuration.

[Explanation of symbols]

11 Light-Emitting / Light-Receiving Means 12 Transmission Driving Means 13 Reverse-Phase Amplifying Means 14 Voltage Limiting Means 15 Breaking Means 131 Amplifying Units 132 Feedback Resistors 251 Positive-Phase Amplifying Units 252 Reverse-Phase Amplifying Units (Blocking Means) 21 Light-Emitting Diodes (Light-Emitting / Receiving Means) 27 diode (voltage limiting means)

Claims (6)

[Claims] 1. A ping-pong transmission type transmitter / receiver that performs transmission and reception in a time-division manner, emits light with an intensity according to the level of a flowing current, and generates a current with a level according to the intensity of the received light. Light emitting / light receiving means (11) for outputting, transmission driving means (12) for driving this light emitting / light receiving means (11) at the time of transmission with a current having a level according to the level of the transmission signal, and light received at the time of reception The light emitting / receiving means (1
1) Parallel feedback parallel injection type anti-phase amplification means (13) for amplifying the current output from the anti-phase amplification means (13) so that the forward direction coincides with the feedback direction of the anti-phase amplification means (13). It is connected in parallel to the feedback resistor (132) of (13), and when the output voltage of the anti-phase amplifying means (13) exceeds a predetermined voltage, it becomes in the operating state, and this output voltage is limited to the predetermined voltage. A ping-pong transmission transmitter / receiver comprising: means (14); and a cutoff means (15) for forcibly setting the voltage limiting means (14) to a cutoff state during transmission. 2. The interrupting means (15) forcibly outputs the output voltage of the anti-phase amplifying means (13) during transmission.
2. The ping-pong transmission transmitter / receiver according to claim 1, wherein the voltage limiting means (14) is cut off by lowering the input voltage from the input voltage of (3). 3. The amplification section (131) of the anti-phase amplification means (13).
Are a positive phase amplification section (251) that amplifies the input signal of the negative phase amplification means (13) in a normal phase, and a negative phase amplification section (252) that amplifies the amplified output of the positive phase amplification section (251) in a reverse phase. The ping-pong transmission transmitter / receiver according to claim 1, characterized in that 4. The cutoff means (15) forcibly applies the output voltage of the negative phase amplification section (252) during transmission to the positive phase amplification section (25).
4. The ping-pong transmission transmitter / receiver according to claim 3, wherein the voltage limiting means (14) is cut off by lowering the input voltage from the input voltage of (1). 5. The ping-pong transmission transmitter / receiver according to claim 1, wherein the light emitting / receiving means (11) is a light emitting diode (21). 6. The voltage limiting means (14) comprises a diode (2
7. The ping-pong transmission transmitter / receiver according to claim 1, which is 7).