JPH02256340A - Time division 2-way transmission equipment - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a signal by connecting a transmission circuit and a reception circuit to a couple of transmission lines via a transformer, applying variable gain amplifier to an output of the reception circuit applying time division transmission reception, A/D-converting the signal so as to control a gate section. CONSTITUTION:A couple of transmission lines 3 are connected to a transmission circuit 1 and a reception circuit 7 via a transformer 2 to apply time division for the transmission reception in 2-way. A transmission signal is sent (3) via the transformer 2 at the transmission, part of the signal is subject to A/D conversion 8 through a variable gain amplifier 4 and the result is sent to a gate circuit 9. The gate circuit 9 outputs a code whose output indicates a zero level by a transmission reception control signal. On the other hand, the reception signal from the transmission line 3 is subject to variable gain amplification (4) at the reception, A/D-converted (8) and fed to the gate circuit 9. An automatic gain control section 6 controls the output of the gate circuit 9 to approach the level to a desired level. Thus, the deterioration in the reception signal due to a transient phenomenon at the changeover of the transmission reception is prevented.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a time-division bidirectional transmission device.

[Prior Art] FIG. 2 is a block diagram showing a conventional time-division bidirectional transmission device disclosed in, for example, Japanese Patent Publication No. 63-54260. In the figure, (1) indicates a transmitting circuit for transmitting a signal; (
2) is a transformer that receives the signal from the transmitting circuit (1); (3)
is the transmission line connected to the transformer (2), (4) is the variable gain amplifier that receives the signal from the transformer (2), and (5) is the transmission line connected to the transformer (2).
is a human power selection amplifier that inputs the output of the variable gain amplifier (4) and the τ level and selects and outputs the human power according to the transmission/reception control signal, and (6) observes the output of the human power selection amplifier (5) and outputs the gain control signal. (7) is a receiving circuit that combines the variable gain amplifier (4), the input selection amplifier (5), and the automatic gain control unit (6). It is.

Next, the operation will be explained. In time-division bidirectional transmission, 1
A set of transmission paths is used repeatedly for transmission and reception in a time-division manner.

During transmission, a transmission signal is sent from the transmission circuit (1) to the transmission line (3) via the transformer (2). At this time, the transmission signal is also received in the receiving circuit (7) and sent to the input selection amplifier (5) through the variable gain amplifier (4). However, the human power selection type #M device (5) selects and outputs the zero level human power of the +2 input terminal according to the transmission/reception control signal, so the output of the receiving circuit (7) becomes zero level, and the transmitted signal is transmitted to the receiving side. will not affect.

On the other hand, during reception, the output of the transmitting circuit (1) is at zero level, and the received signal from the transmission line (3) is passed through the variable gain amplifier (
4) and further sent to the input selection amplifier (5). The manual power selection amplifier (5) selects and outputs the output of the variable gain amplifier (4) which is +1 manual power according to the transmission/reception control signal. The output of the manually selected amplifier (5) is observed by an automatic gain control section (6), and the gain of the variable gain amplifier (4) is controlled by a gain control signal so as to approach a desired level.

[Problems to be Solved by the Invention] Since the conventional time-division bidirectional transmission device is configured as described above, the transient phenomenon of the input selection amplifier (5), which is an analog element, occurs when switching from transmission to reception. There was a problem that the received signal deteriorated due to this.

This invention was made to solve the above-mentioned problems, and its purpose is to provide a time-division bidirectional transmission device that can significantly reduce the deterioration of the received signal when switching from transmitting to receiving. shall be.

[Means to solve the problem]

A time-division bidirectional transmission device according to the present invention includes a transmission circuit that sends a signal to a transmission path via a transformer, and a reception circuit that receives a signal from the transformer. In a time-division bidirectional transmission device that repeatedly uses transmission and reception, the receiving circuit includes a variable gain amplifier that receives a signal from the transformer, and an A/D converter that converts the output signal of the variable gain amplifier into A/D. A conversion section;
a gate section that controls the output signal of the A/[1 conversion section by a transmission/reception control signal; and an automatic gain control section that outputs a gain control signal based on the level of the output signal of the gate section to control the gain of the variable gain amplifier. It is equipped with the following.

[Effect]

In this invention, the output of the variable gain amplifier is
After being converted, the output is controlled in the gate section. That is, switching between transmission and reception is performed by digital signals. Therefore, it is possible to suppress deterioration of the received signal due to transient phenomena at the time of switching.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In Figure 1, (1) is a transmission circuit that transmits a signal, (2) is a transformer that receives the signal from the transmission circuit (1), (3) is a transmission line connected to transformer (2), and (4) is Trance (2
), (8) is an A/D converter that A/D converts the output signal of variable gain amplifier (4), and (9) is an A/D converter that converts the output signal of A/D converter (8). a gate circuit controlled by a transmission/reception control signal; (6) an automatic gain control unit which monitors the output of the gate circuit (9) and controls the gain of the variable gain amplifier (4) by a gain control signal; (7)
are variable gain amplifier (4), A/D converter (8)
Gate circuit (9) This is a receiving circuit combined with an automatic gain control section (6).

Next, the operation will be explained. In time-division bidirectional transmission, 1
A set of transmission paths is used repeatedly for transmission and reception in a time-division manner.

During transmission, a transmission signal is sent from the transmission circuit (1) to the transmission line (3) via the transformer (2). This truncated transmission signal is also received by the receiving circuit (7), passes through the variable gain amplifier (4), and is input to the A/D converter (8). The A/D converter (8) converts the input analog signal into a digital code and sends it to the gate circuit (9), and the gate circuit (9) outputs a code indicating that the output is at zero level according to the transmission/reception control signal. do.

On the other hand, during reception, the output of the transmitting circuit (1) is at zero level, and the received signal from the transmission line (3) is passed through the variable gain amplifier (
4) and then further processed by the A/D converter (8)^
/D converted. The A/D converted reception signal is input to the gate circuit (9) and is A/D converted by the transmission/reception control signal.
The output signal of the D converter (8) is output as is. The output signal of the gate circuit (9) is observed by an automatic gain control section (6), and the gain of the variable gain amplifier (4) is controlled by the gain control signal so as to approach a desired level.

As mentioned above, the gate circuit (9) is at zero level during transmission,
At the time of reception, the output signals of the A/D converters (8) are respectively output, but since they are all digital signals, they can be constructed with simple gate elements.

Further, since a digital circuit is used, it is possible to instantly switch the output signal using the transmission/reception control signal without causing a transient phenomenon when switching between transmission and reception. In particular, when switching from transmission to reception, there is no possibility that the received signal will be degraded by transient phenomena, unlike in conventional analog elements.

In addition, in the above embodiment, the A/D conversion section and the gate section are
Although the case is shown in which the A/D converter (8) and the gate circuit (9) are configured, if the A/D converter (8) itself has a control input terminal for switching the output to a zero level code, this can be used. may be used instead of the gate circuit (9).

(Effects of the Invention) As explained above, the present invention converts the output of the receiving circuit for time-division bidirectional transmission into a digital signal through A/D conversion, and switches between transmission and reception using the digital circuit. Therefore, there are effects such as being able to suppress deterioration of the received signal due to transient phenomena when switching from the transmission time to the reception time.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a time-division bidirectional transmission device showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional time-division bidirectional transmission device. DESCRIPTION OF SYMBOLS 1... Transmission circuit, 2... Transformer, 3... Transmission line, 4... Variable gain amplifier, 6... Automatic gain control unit, 7... Receiving circuit, 8... A/ D converter, 9...gate circuit. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A time-division bidirectional system that includes a transmitting circuit that sends a signal to a transmission path via a transformer, and a receiving circuit that receives a signal from the transformer, and uses a set of transmission paths repeatedly for transmission and reception in a time-division manner. In the directional transmission device, the receiving circuit includes a variable gain amplifier that receives a signal from the transformer, and an A/D converter that converts the output signal of the variable gain amplifier.
a D conversion section, a gate section that controls the output signal of the A/D conversion section using a transmission/reception control signal, and an automatic controller that outputs a gain control signal based on the level of the output signal of the gate section to control the gain of the variable gain amplifier. A time division bidirectional transmission device comprising: a gain control section.