JPH0270148A - Direct modulation circuit - Google Patents

Abstract

PURPOSE:To attain direct modulation by means of NRZ and to execute efficient transmission by modulating a carrier in accordance with the output of a switch circuit. CONSTITUTION:The moment NRZ data input changes from a high level to a low level, the switch circuit 1 opens and NRZ data is transmitted to a modulation circuit 4. A timer circuit 2 detects an input state, operates by quick action and slow recovery, and controls the switch 1. Since the output-side of the switch circuit 1 is biased in the operating mid-point of the modulation circuit by a bias circuit in a steady state where data is not inputted, modulation is executed in accordance with the change of the polarity of NRZ data.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a modulation circuit for transmitting data using wireless signals, and particularly relates to a direct modulation circuit for directly modulating wireless signals using NRZ data. .

Data transmission is performed by various means for the purpose of connecting a terminal computer and a central computer, etc., but when the terminal is a mobile object or for other reasons, it is required to use wireless signals as the transmission medium. There may be cases.

In radio equipment used in such lines, there is a need for a direct modulation circuit that can directly modulate radio signals with NRZ data.

[Conventional technology]

When transmitting data using conventional FM radios, etc.,
Generally used are an FSK method in which NRZ data is once converted into an alternating current component using a subcarrier, and a sprint phase method in which a polarity change is caused at the center of the NRZ data to convert it into alternating current.

[Problem to be solved by the invention]

In the case of the FSK method, subcarriers are used, so the transmission band of the line used is expanded based on the band for transmitting the subcarrier and the band required by the data transfer rate.
Efficient transmission cannot be performed.

Furthermore, in the split phase method, the transmission rate is twice that of the original data, so efficient transmission is still not possible.

In this way, in all conventional methods, the signal frequency is higher than the original NRZ data, so it is not only impossible to perform high-rate data transmission in the limited radio signal transmission band (for example, polyphase PSK transmission and reception). There was a problem in that a complicated circuit system such as a device had to be used.

On the other hand, it is conceivable to directly modulate the radio signal with NRZ data. However, when NRZ data is directly applied to the modulator input, the modulation input level has a DC component that is either high level or low level unless the data generation side is transmitting data, so the carrier wave output signal frequency of the wireless device is biased toward the high or low end, and the NR
As Z data is input, the center of the carrier wave frequency changes according to the time constant of the circuit.

In such a state, an error occurs in data during demodulation on the receiving side, which is not preferable.

The present invention aims to solve the problems of the prior art, and even if the carrier wave is directly modulated using NRZ data, it is possible to perform good modulation without causing bias in the carrier wave center frequency due to the DC component. Realizes a direct modulation circuit,
Therefore, it is an object of the present invention to enable efficient transmission by increasing the transmission rate.

[Means to solve the problem]

The direct modulation circuit of the present invention comprises a switch circuit, a timer circuit 2, a bias circuit 3, and a modulation circuit 4, as shown in FIG.

The switch circuit 1 generates an output signal in response to human input NRZ data in an operating state, and has a high impedance on the output side in a stopped state.

The timer circuit 2 activates the switch circuit 1 at the start of the input NRZ data, and holds the switch circuit 1 in the operation state for a certain period of time at the end of the input NRZ data, and then stops the switch circuit 1.

The bias circuit 3 is connected to the output of the switch circuit 1 and maintains the output at a central level when the switch circuit 1 is in a stopped state.

The modulation circuit 4 modulates the carrier wave according to the output of the switch circuit 1.

[For production]

In FIG. 1, a switch circuit 1 opens when input NRZ data is reversed from a steady state and outputs NRZ data.

The timer circuit 2 detects the input state and operates in a fast-acting, slow-recovery manner to control the switch 1.

In a steady state in which no data is input, the output side of the switch circuit 1 is biased by the bias circuit 3 to the operating midpoint of the steel changing circuit 4, and therefore, in the steady state, the output carrier of the modulation circuit 4 is fixed at its center frequency. It has become so.

The switch circuit 1 is opened from the moment the NRZ data input changes from high level to low level, and NRZ data is sent to the modulation circuit 4.

Therefore, the modulated wave output signal output from the modulation circuit 4 is always at the midpoint of the modulation characteristic at the start of input NRZ data, and modulation is performed in accordance with changes in the polarity of the NRZ data.

Since such a modulated wave output signal is generated, the receiving side uses a normal discrete detection type demodulation circuit to perform tl
Able to perform tuning.

If the FM modulator is directly modulated with NRZ data without the circuit of the present invention, the carrier wave will remain shifted to one side in the steady state of the data, so the center of the modulated signal will be shifted at the rising point of the data. However, according to the present invention, this problem is solved, and direct modulation using NRZ data becomes possible, making it possible to realize efficient transmission at a high transmission rate.

〔Example〕

FIG. 2 is a circuit diagram showing the configuration of an embodiment of the present invention, in which 1) is a fast-acting slow-return circuit, 12 is a 3-stall L-gate circuit, and R, , R2 are resistors.

Further, FIG. 3 is a time chart showing signals of various parts in the circuit of FIG. 2.

Now, in Figure 2, the input data is T from 0 (low level) to +5■ (high level) as shown in Figure 3.
Assume that a TL signal is input. In this case, it is assumed that the steady state of the input data is at a high level, that is, +5V.

The output of the fast-acting slow-return circuit 1) is always at a high level, but it operates when the input data rises.
As shown in FIG. 3, the output immediately becomes a low level. The output of the fast-acting slow-return circuit 1) is a 3-state gate circuit 1.
It is applied to the enable terminal E of No. 2.

The three-state gate circuit 12 operates as shown in the truth table in Figure 4, and when "1" (high level) is given to the enable terminal E, it generates an output corresponding to the input. However, when "0" (low level) is applied to the enable terminal E, the output side becomes high impedance (H).

The output side of the three-state gate circuit 12 is a resistor RI.

It is connected to the midpoint of a voltage dividing circuit made up of R2, and a bias is applied through this voltage dividing circuit.

For example, when OV (ground) and +5V are applied as the power supply to the voltage divider circuit, the bias voltage becomes +2.5■.

Therefore, when the steady state is +5■ as shown in FIG. 3 and a waveform signal that changes to OV and +5V is applied as input data, the output of the three-state gate circuit 12 is shown in FIG. So, the steady state of the input data is +2.5
(2), and the input data OV and +5 (2) are output as they are.

Therefore, if this output ■ is applied as an input to a modulator of a wireless device (not shown), in the modulated wave output signal obtained, the carrier frequency at the beginning of the data is always at the center, and the input data changes between low level and high level. Since the signal changes at both ends as the signal changes, on the demodulation side, data can be reproduced using a ti88 circuit using a normal discrete detection method.

The output of the quick-acting slow-return circuit 1) returns to high level after a certain period of time has elapsed since the input became high level.

The delay time τ is set so that when the last part of the input NRZ data continues to be at a high level, the output of the interlocking delay/return circuit 1) will not immediately go to a high level and cause a data error. is set to be longer than the possible continuous time length.

〔Effect of the invention〕

As explained above, according to the direct modulation circuit of the present invention, the carrier wave can be directly modulated by NRZ data, so it is possible to efficiently transmit the carrier wave as binary data up to a high transmission rate. It is now possible to modulate and demodulate without any additional processing, and 2
Because it is value transmission, it becomes possible to perform transmission that is advantageous in terms of error rate. Furthermore, since the direct modulation circuit of the present invention can be realized with a simple circuit configuration, it is possible to make the device smaller and lower in price.

1)--Fast-acting slow-return circuit 3 state gate circuit

Claims (1)

[Claims] A switch circuit (1) that generates an output signal according to input NRZ data in an operating state and whose output side becomes high impedance in a stopped state, and a switch circuit (1) that generates an output signal in response to input NRZ data when the input NRZ data starts. A timer circuit (1) that keeps the switch circuit (1) in the operating state for a certain period of time and then stops the switch circuit (1) when the input NRZ data ends.
2), a bias circuit (3) connected to the output of the switch circuit (1) and maintaining the output at the center level when the switch circuit (1) is in a stopped state; 1. A direct modulation circuit comprising: a modulation circuit (4) that modulates a carrier wave accordingly.