JPS6051344A - Data transmission equipment - Google Patents

Abstract

PURPOSE:To make a crystal piece or the like unnecessary and to reduce the cost detecting respective frequencies of an FSK signal independently of one another with band-pass filters to constitute a carrier collision detecting circuit. CONSTITUTION:Frequencies f1' and f2' of a down signal V2 consisting of an FSK signal Fs inputted to a receiving circuit 4b are converted to intermediate frequencies f1'' and f2'' through a front end 7, and they are extracted by band- pass filters 12a and 12b. These extracted signals are supplied to carrier detecting circuits 14a and 14b through amplifiers 13a and 13b respectively to detect whether there are carriers or not. If both carrier signals are absent, a decoding circuit 17 decides that the device is not in the data transmission state; but if both carrier signals are present, the circuit 17 discriminates that data are transmitted from plural terminals simultaneously. If only one carrier signal is detected, the circuit 17 decides that data is transmitted but collision does not occur.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a data transmission device.

[Background technology]

Conventionally, there is a one-direction data transmission system using this type of data transmission device, as shown in Fig. 1.
(1) is a coaxial cable, (2) is a branch, (3) is a converter, and (4) is an ETA transmission/reception terminal.

Here, a signal obtained by modulating a carrier wave (frequency fA) with a data signal to be transmitted is sent from the transmitting circuit of the terminal device (4) to the coaxial cable (1) as an upstream signal V1. This upstream signal V is connected to the coaxial cable (1) and the branch (2)
is received by the converter (3) via the converter (3).
) converts the frequency fA of the carrier wave of this upstream signal v1 to fB to form a downstream signal v2 and sends it to the coaxial cable (1). In the receiving circuit of the terminal (4), this downlink signal V
2 via a coaxial cable (1) and a splitter (2) to demodulate the data signal. By the way, since this data transmission system is a distributed processing system that does not have a central control unit, when one terminal device (4) is transmitting data, other terminal devices (4) do not perform data transmission. Each terminal (4) must detect +Seria on the coaxial cable (1), and when +Seria from other terminals (4) is detected, it will not transmit data. I was supposed to wait. However, when multiple terminal devices (4) start data transmission at approximately the same time, there is a problem that the data transmission is not stopped by the above-mentioned cow seria detection and interference occurs, so another collision detection means is used. It was necessary to set it up to stop ETA transmission. FIG. 2 and FIG. 5 show a transmitting circuit (4a) and a receiving circuit (4b) of a conventional terminal device (4), and the transmitting circuit (4a) is
Oscillation circuit (5a) that generates frequency f1 and one frequency f2
An oscillation circuit (5b) that generates
aX6b), and the control signal vb Niteana D Gusui Sochi (6a) (6b) based on the data signal VD consisting of a binary signal to be transmitted is turned off and becomes "1" of the data signal VD. Correspondingly, a frequency f2 is output corresponding to the frequency f1 and "0", and a so-called FSX modulation signal vF is sent out from the transmitting circuit (4a). However, when the tartar signal vD is not input, which frequency f
1 and f are also not output, and the transmission of the FSK modulated signal VF is stopped. On the other hand, the receiving circuit (4b) has a front end (
7), an FM demodulation circuit (8), a collision detection circuit (9),
It consists of a rear detection circuit nO and a waveform shaping circuit 01), and the received signal (downlink signal 2) is amplified at the front end (7) and subjected to frequency conversion (
intermediate frequency), is FM demodulated in the FM demodulation circuit (8), and this demodulated signal is extracted by DC coupling and sent to the waveform shaping circuit Q.
l) to form a data signal V that is a binary signal after waveform shaping.
It is now possible to get a D. The downlink signal V2 received by the receiving circuit (4b) is sent out from the transmitting circuit (4a) of another terminal (4) and has the frequency f, f2 of the uplink signal V1 consisting of the FSK signal VF. are respectively f'H
This is a signal converted to 1f2, and the frequency of the carrier wave is converted by a cosciverter (3). +Ceria detection circuit αO performs envelope detection of the intermediate frequency signal output from the front end (γ) to detect the presence or absence of ceria.
+Ceria detection signal Vc is output. In addition, the collision detection circuit (9) detects the beat If;-fil when the frequencies f:f; are received at the same time, and the interference detection circuit (9) detects the beat If;-fil when the frequencies f:f; Output vM. Here, the collision detection circuit (9
) performs AM detection on the intermediate frequency signal output from the front end (7), then extracts the beat component using a filter,
The collision detection signal VM is obtained by rectification and waveform shaping. By the way, in such a conventional example, in addition to the FM demodulation circuit (8), there is also an FM demodulation circuit (8). A detection circuit αO and a collision detection circuit (9) are required, making the circuit configuration complex and increasing the number of parts.In addition, since only one peat component is detected, the allowable range of frequency fluctuation of the FSK signal VF becomes smaller. , a crystal oscillation circuit must be used as the oscillation circuit (5aX5b) of the transmitter circuit (4a), which raises the problem of increased cost, and furthermore, the collision detection circuit (9)
The signal processing time of the rectification and waveform shaping section is long, so
There was a problem that it took too much time to detect a collision.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and provides a mullet-to-sun transmission device that has a simple circuit configuration, can quickly detect collisions, and has a wide tolerance range for frequency fluctuations of FSX signals. It's about doing.

[Disclosure of the invention]

(Embodiment) FIG. 4 shows a receiving circuit (4) of a terminal (4) according to an embodiment of the present invention.
FIG. 4 is a cross-sectional circuit diagram showing the configuration of FIG. In the figure, (16a) and (16b) are frequency detection units that individually detect each frequency of the FSK signal VF, and (12a) (
12b) is a band pass filter, (13a) (13b)
is an amplification circuit, and (14a) and (14b) are +seri? Detection circuit, (15a') (15b) is waveform shaping circuit, αη
are equalizer circuits that decode the outputs of the frequency detection sections (16a) and (16b), (TD) is a data signal output terminal, and (Tc) is +SER? Detection signal output terminal, (TM
) is a collision detection signal output terminal.

The operation of the embodiment will be described below. Now, the downlink signal V consisting of the FSX signal Fs input to the receiving circuit (4b)
The frequencies f'1 and fz of 2 are amplified by the front end (7) and are also converted to intermediate frequencies? ;1. /l, and the frequency, /C, f
/4 respectively, and t=t-rear detection circuit (14a
) After envelope detection is performed in (14b), the signal detection signals Vc and Vc2 are obtained via the waveform shaping circuits (15a and 15b), and the frequency f1
is received, the + ceria detection signal Vcl output from the frequency detection unit (crow) is at “H” level, and the frequency is
The signal detection signal VC! is output from the frequency detection unit (llb) when received. becomes “H” level and the frequencies f;, t; are not received, + ceria detection signal Vc
, t Vc 2 are respectively at the ``V level, and the +Yaria detection signal Vc1Vc2 becomes a 0-ji riff signal that is at the ``H'' or ``L'' level depending on the presence or absence of the frequency f; The truth table for is as shown in the table below. Now, when +Ceria detection signals vc1 and Vc2 are both at "L" level, +Ceria detection signal Vch collision detection signal VM
becomes L" level, indicating that there is no data transmission. At this time, the data signal Vn is undefined.Next, when one of the frequencies G, f; is received, +
Ceria detection signal Vc 1% Vc! Based on this, the "H" and "L" levels of the data signal vD are output, and the ceria detection signal Vc becomes "H" level to output the presence of data transmission.At this time, , the collision detection signal vM is at "L" level, indicating that there is no signal collision.Next, the +ceria detection signal Vc 1 s V
When both c 2 become 1H'' level, the collision detection signal VM becomes ``H'' level, indicating that there is a signal collision and data transmission is being performed simultaneously from multiple terminal devices (4). At this time, the +ceria detection signal Vc is at wH++ level, and the data signal VD is undefined.Here, the +ceria detection signal Vc and the collision detection signal vM are the cow ceria detection signal Vc1 k Vc, It is obtained by decoding the signal, which reduces the cost, simplifies the circuit configuration, requires almost no signal processing time, and enables quick signal collision detection. Since signal collision detection is not performed by detecting the beat component as shown in FIG. , the permissible variation range is larger than that of the conventional example, and there is no need to use expensive ice crystal oscillation circuits as the oscillation circuits (5a) and (5b), resulting in cost savings.

〔Effect of the invention〕

As described above, the present invention includes a transmitting circuit that transmits an FSX signal in which different frequencies are set corresponding to "1" and rOJ of the data signal consisting of a binary signal, and a transmitting circuit that receives the FSX signal and transmits the data signal. In a data transmission device including a receiving circuit for demodulating, a frequency detecting section detects each frequency of the FSX signal individually using a band pulse filter, and the output of the image frequency detecting section is decoded to generate a data signal, + ceria detection signal, and The receiver circuit is equipped with an equal i circuit that outputs a collision detection signal, and the frequency detector output is decoded by the ramie coater circuit. Since the detection signal and the collision signal are obtained, the circuit configuration is simplified and collision detection can be performed quickly.Furthermore, the frequency fluctuation of the FSX signal can be selectively detected. Since only the band width of the bandpass filter in the frequency detection section is allowed, the allowable range of frequency fluctuation is larger than in the conventional example, and there is no need to use a crystal oscillator circuit in the transmitter circuit, which has the effect of reducing costs. be.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a bidirectional data transmission system using a data transmission device according to the present invention, FIGS. 2 and 3 are main part pro-ref circuit diagrams of a conventional example, and FIG. FIG. 2 is a block circuit diagram of a main part of an embodiment. (4a) is a transmitting circuit, (4b) is a receiving circuit, (16a)
(16b) is a frequency detection section, and the surface is a decoder circuit. Agent Patent Attorney Ishi 1) Chief Seven Procedures Amendment (Voluntary) January 23, 1980 Patent Application No. 159629 of 1988 2, Name of invention Data transmission device 3, Relationship with the case of the person making the amendment Patent Applicant Location: 1048 Kadoma, Kadoma City, Osaka Prefecture Name (
583) Matsushita Electric Works Co., Ltd. Representative Iku Kobayashi 4, Agent 8, Contents of the amendment We will correct "band pulse filter" on page 9, line 16 of the specification of this application to "band pass filter." 275-

Claims (1)

[Claims] (1) “1” of the data signal consisting of a binary signal, rO
In a data transmission device that includes a transmitting circuit that transmits an FSK signal with different frequencies set corresponding to J, and a receiving circuit that receives the FSX signal and demodulates the data signal, each frequency of the FSK signal is divided into bands. A receiving circuit includes a frequency detection section that detects each frequency individually using a pass filter, and a dicoter circuit that decodes the output of the image frequency detection section using a dicoter circuit and outputs a ray signal, a + ceria detection signal, and a collision detection signal. A data transmission device characterized in that: