JPS6042966A - Data signal demodulating circuit - Google Patents

Abstract

PURPOSE:To eliminate completely noise generated when a received carrier signal is interrupted by adding a circuit generating a pulse masking noise during the period of noise generation generated at the interruption of carrier signal after the end of data through the detection of the end of data. CONSTITUTION:It is required that a noise erase pulse 4-18 is turned off already at the head of noise component 4-16 in order to erase completely the noise component 4-16 of a demodulated data signal 4-12 with a noise erasing pulse 4-18 and the noise erase pulse 4-18 continues the OFF state until end of the noise componene 64-16. Thus, the following limit conditions are required; T4<T2, T4+ T5>T2+T3, T3+T4+T5<T6+T1, where T1 and T2 are respectively a carrier transmission start time and a carrier transmission stop time. The noise component 4-16 is erased completely by satisfying the limiting conditions above.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a data signal demodulation circuit to which a carrier signal is input in a transmission system for carrier signals that are generated intermittently and at intervals longer than a certain time. .

[Background of the invention]

Conventionally, when demodulating a received data signal from a received carrier signal, a configuration shown in FIG. 1 has been used. In FIG. 1, when a carrier signal 1-6 is input to a demodulator input terminal 1-4, a demodulated signal 1-7 is outputted by a demodulation circuit 1-1. This demodulated signal 1-7 is a carrier signal 1-
Noise is occurring during the period when 6 is disconnected.

Further, the carrier signal 1-6 is connected to the carrier sense circuit 1-2.
, and carrier sense signals 1-8 are output.

This carrier sense signal 1-8 is a carrier signal 1-6.
This is a signal that turns off with a delay of the carrier disconnection detection time Ta from the end of the period.

The above demodulated signal 1-7 and carrier sense signal 1-8 are ANDed by an AND gate 1-3, and a received data signal 1-9 is outputted to an output terminal 1-5.

This reception data signal 1-9 contains a noise component 1 for a period of carrier interruption detection time Ta after carrier signal 1-6 is interrupted.
-10 remains. The carrier disconnection detection time Ta is determined by the time constant of the carrier sense circuit 1-2. The noise 1-10 in the received data signal 1-9 is the noise 1-10 in the received data signal 1-9.
It may have an adverse effect on the device (such as a computer) that outputs the information.

In order to compensate for the drawbacks of the demodulator shown in FIG. 1, a demodulator shown in FIG. 2 has been proposed.

In FIG. 2, when a carrier signal 2-7 is input to an input terminal 2-5, a demodulated signal 2-8 is outputted by a demodulation circuit 2-1. This demodulated signal 2-8 includes a carrier signal 2
-7 Noise is occurring during the disconnection period.

Further, the carrier signal 2-7 is transmitted to the carrier sense circuit 2-
2, and carrier sense signals 2-9 are output. This carrier sense signal 2-9 is a carrier signal 2-9.
This signal is turned off after a delay of carrier disconnection detection time T with respect to the time of disconnection. Furthermore, the carrier signal 2-7 has a shorter carrier disconnection detection time Tb than the carrier sense circuit 2-2. There is a big sword in the second carrier sense circuit,
A second carrier sense signal 2-10 is output.

This second carrier sense signal 2-1o is a signal that turns off after a delay of carrier disconnection detection time T with respect to the time point when the carrier signal 2-7 is disconnected.

The above demodulated signal 2-8, carrier sense signal 2-9 and second carrier sense signal 2-10 are connected to the AND gate 2-
4, and the received data signal 2-11 is output as a logical product to the output terminal 2-6. This received data signal 2-
11, a noise component 2-12 remains in the carrier signal 2-7 for a period of Tb. This noise 2-12 is shorter than the noise 1-10 shown in Figure 1, but
Remaining in received data signal 2-11, received data signal 2-1
1 may have an adverse effect on the device (such as a computer) that outputs it.

[Purpose of the invention]

It is an object of the present invention to solve the problem of noise 1-
The object of the present invention is to provide a data signal demodulation circuit that reliably eliminates the signals 10 and 2-12 and eliminates any adverse effects on the device to which the received data signal is output.

[Summary of the invention]

In conventional circuits that demodulate carrier signals that are input in bursts, the noise generated when the carrier signal is cut off is canceled by the carrier sense signal.
Noise remained during the period (detection time) from when the carrier signal was cut off to when the carrier sense signal was turned off.

Therefore, in the present invention, a data sense circuit that eliminates noise using a carrier sense signal, and determines the presence or absence of data from the demodulated data signal detects the end of data, and detects the noise that occurs when the carrier signal is cut off after the end of data. During the noise generation period ζ, the noise generated when the received carrier signal is interrupted is completely erased by adding a circuit that generates a pulse that masks the noise. [Embodiments of the Invention] An embodiment in which the present invention is applied to the received data signal shown in FIG. 3 will be described in detail with reference to the drawings.

As shown in FIG. 3(a), the received data signal used in this embodiment has no level change for data 11'', and alternates between positive and negative polarities of 1 for data 0. This is a data signal that causes a level change for the first half bit.

Further, as shown in FIG. 3(b), there is an idle period in which the signal does not change by 17 bells, and an active period in which the signal level changes.

The active period is divided into two sections (8 bits: 01111110) shown in FIG. 3(C).

Start flag 3-1. The data 3-2 sandwiched between the g completion flag 3-3 and the flag ζ is the L gnome (see Figure 2 (d).
)).

The pregnancy data 3-2 between the flags has 5 bits, 1, and a zero is inserted to add data “0” next to consecutive “1” data, and in the frame, continuous data “1” is inserted into the hook. 6 bits is the maximum.

In contrast to the above data signals, the gear rear signal is as shown in Fig. 3 (e
), the carrier signal is turned on by To before the start of the received data signal, and the carrier signal is turned off after T2 from the end of the frame.

FIG. 4 shows a block diagram and a time chart of a demodulation circuit when a carrier signal having the above signal waveform is applied to this Suimei.

In FIG. 4, when a carrier signal 4-9 is input to the input terminal 4-7 of the demodulator, the demodulation circuit 4-1 receives the demodulated signal 4.
Outputs -10. Noise is generated in this demodulated signal 4-10 while the carrier signal 4-9 is off.

At the same time, the carrier signals 4-9 are transmitted to the carrier sense circuit 4.
-2, and a carrier sense signal 4-11 is output. This carrier sense circuit 4-2 has a carrier signal 4
This is a circuit that turns off the output after a delay of carrier disconnection detection time T3 after the disconnection of -9.

The above demodulated signal 4-10 and carrier sense signal 4-1
1 is input to the ungate 4-3, and the demodulated data signal 4
-12 is output. - This demodulated data signal 4-12 has a carrier disconnection detection time T3 after the carrier signal 4-9 is disconnected.
A noise component of 4'-16 remains for a period of .

This demodulated data signal 4-12 is input to a data sense circuit 4-4 which determines whether it is an idle period or an active period. In the data sense circuit, the data sense signal 4- turns off after the idle detection time T4 after the end of the frame.
Outputs 13.

The data sense signal 4-13 is further input to a timer circuit 4-5, which outputs a noise erasing pulse 4-14 that remains off for 16 hours from the time the data sense signal turns off.

Noise canceling pulse 4-14 and demodulated data signals 4-12
is input to the AND date 4-6, and the received data signal 4-Li2°\ from which the noise component 4-16 has been removed is output to the output terminal 4-8 of the demodulator.

Here, the data sense circuit and the timer circuit are circuits composed of a counter or a retrigger type single multivibrator, etc., and have an idle detection time T4 and a noise cancellation pulse width T5.
Make the following settings.

Demodulated data signal 4-1 by noise canceling pulse 4-18
In order to completely erase the noise component 4-16 of No. 2, the noise canceling pulse 4-18 is already turned off at the beginning of the noise component 4-16, and the noise canceling pulse 4 continues until the end of the noise component 4-16. -18 must remain off. Therefore, the following constraint conditions are required.

T4〈T2...Four circles...Song F song...(
1) T4+T5〉T2+T3 ・・・・・・Song (2
) Furthermore, the data sense signal 4-12 is a noise component G4-1.
6, it is turned on again and turned off after the idle detection time T4. A second noise canceling pulse 4-19 is generated by this change of the data sense signal 4-12 from on to off.

In order to prevent the leading portion 4-17 of the next received frame from being erased by the second noise-eliminating pulse 4-19, the following constraints are required for the carrier reception interval T6.

'l 3+T a +T s (T a + T s
Town (3) where T1 and T2 are respectively shown in Figure 3(e)
The carrier transmission start time T1 and the carrier transmission stop time T2 are shown in FIG.

Idle detection time T4 and noise cancellation pulse @ that satisfy the above constraints (1), (21, (3))
By setting T5, it is possible to configure a demodulation circuit that completely eliminates noise components 4-16 and does not adversely affect the data of the next frame.

The operation of the data sense circuit 3-3 will now be explained with reference to FIG.

In the data sense circuit, the data sense signal is turned on from time point 5-1 when the transmission data signal changes from the idle state to the active state. After turning on the data sense signal, the time t1 from the first data 0" to the next data "0" is monitored.

If this to is shorter than the preset time T4,
Keep the data sense signal on and press the next data “0”
The interval t2 is monitored. If t is longer than T4, the data sense signal is turned off after T4 hours from the start of time monitoring, and remains off until data 007# of the next transmission data signal. Time monitoring 11.12...
..., tn to obtain a data sense signal.

Here, during the active period, as shown in Figure 3, the maximum value of the interval between data "0" and the next data "0" is
This is the 7-bit time of the flag. Therefore, if T4>7 bit time, the data sense signal will not turn off during the active period of the transmission data signal.

As described above, the data sense signal is turned on from time 5-1 when the transmission data signal becomes active from idle, turns off 14 hours after the last "o" data 52 of the active period, and then turns off at the beginning of the next active period 5-1. At 3, the signal turns on and roars again.

〔Effect of the invention〕

As explained above, according to the present invention, in a circuit that demodulates a carrier signal that is input in bursts, the noise after the carrier signal is cut off, which could not be completely erased by the conventional circuit, can be completely erased, and the noise that can be transmitted to the next data It is possible to realize a data signal demodulation circuit that does not adversely affect the data signal demodulation circuit.

Further, in this embodiment, the received data signal and the carrier signal have been described as the signals shown in FIG. 2, but the present invention is not limited thereto, and the received data signal 5 whose idle period and active period can be distinguished, for example, Only active periods are coded (Manchester coding, CMI
The present invention can be applied by setting the frame end detection time T4 and the noise erasing pulse width T5 for the signal obtained by the following methods.

[Brief explanation of drawings]

Figure 1(a) is a block diagram of a conventional demodulation circuit;
b) is a time chart showing the operation of a conventional demodulating circuit, FIG. 2 is a block diagram of the demodulating circuit in FIG.
b) is a time chart showing the operation of the demodulation circuit in Fig. 2(a), Fig. 3(a), (b), (c), (
dl and (e) are time charts showing the signal form, signal state, flag pattern, frame structure, and relationship with the carrier signal of the received data explained in detail according to the present invention, and FIG. 4a is a block diagram of the demodulation circuit according to the present invention. Figure, Figure 4 (
bl is a time chart showing the operation of the demodulation circuit according to the present invention, and FIG. 5 is a time chart showing the operation of the data sense circuit.

Claims (1)

[Claims] In a data signal demodulation circuit for a data carrier signal that is input in bursts, a demodulation signal obtained by taking the logical product of the output of the demodulation circuit using the carrier signal and the output of the carrier sense circuit is used. . A data signal demodulation circuit further comprises performing an AND operation with a pulse signal output from a data sense circuit and a timer circuit that determine the presence or absence of data.