阅读说明：本技术 可变周期调制系统的脉宽调制调光方法 (Pulse width modulation dimming method of variable period modulation system ) 是由 孙哲 何胜阳 吴芝路 赵雅琴 任广辉 于 2019-11-13 设计创作，主要内容包括：可变周期调制系统的脉宽调制调光方法,本发明涉及一种脉宽调制的调光方法，是为了实现根据发送信号时间长度的不同来判别不同的信息，提高了带宽利用率，本发明是一种DCF?MVPM调制的基于脉宽调制的明暗控制方法，本发明根据发送信号时间长度的不同来判别不同的信息，提高了带宽利用率，同时具有抑制光源闪烁和调节明暗的功能。(The invention relates to a pulse width modulation dimming method of a variable period modulation system, in particular to a dimming method of pulse width modulation, which aims to realize the discrimination of different information according to the difference of the time length of a sending signal and improve the bandwidth utilization rate.)

1. The pulse width modulation dimming method for the fixed duty ratio variable period modulation system in visible light communication is characterized by comprising the following steps: the signal transmitting method comprises the following specific steps:

step one, carrying out DCF-MVPM modulation on original information by using a DCF-MVPM modulation system to obtain a signal after the DCF-MVPM modulation;

step two, performing pulse width modulation on the signal obtained in the step one after the DCF-MVPM modulation to obtain a signal after the pulse width modulation;

thirdly, performing analog/digital conversion on the pulse width modulated signal obtained in the second step to obtain a digital pulse width modulated signal;

step four, converting the digital pulse width modulated signal obtained in the step three into an optical signal and then transmitting the optical signal;

the signal receiving method comprises the following specific steps:

step five, the transmitting end receives the optical signal in the step four, and performs photoelectric conversion on the received optical signal to obtain an electric signal of the received signal;

step six, conditioning the electric signals of the received signals obtained in the step five to obtain conditioned signals;

seventhly, performing digital/analog conversion on the conditioned signal obtained in the sixth step to obtain an analog signal of a received signal;

and step eight, carrying out DCF-MVPM demodulation on the analog signal of the received signal obtained in the step six to obtain transmitted original information, and finishing a communication process.

2. The PWM dimming method according to claim 1, wherein in the first step of performing DCF-MVPM modulation on the original information by using the DCF-MVPM modulation system, the pulse duration modulation factor η is selected to be different_DCF-MVPMAnd controlling the brightness of the room.

3. The pwm dimming method for a fixed duty cycle variable period modulation system in visible light communication according to claim 2, wherein:

in the process of performing DCF-MVPM modulation on the original information by using the DCF-MVPM modulation system in the first step, the waveform pulse duration modulation coefficient η_DCF-MVPMThe value range is as follows:

wherein, t_H0Is the basic pulse duration, t, in the DCF-MVPM modulation waveform_L0For a substantially low level duration, t, in the DCF-MVPM modulation waveform_H0minIs the minimum duration of the high level in the DCF-MVPM modulation waveform, t_L0minIs the minimum duration of the low level in the DCF-MVPM modulation waveform.

4. The pwm dimming method for a fixed duty cycle variable period modulation system in visible light communication according to claim 3, wherein: high-level minimum duration t in DCF-MVPM modulation waveform_H0minAnd a low level minimum duration t in the DCF-MVPM modulation waveform_L0minThe specific selection method comprises the following steps:

high level duration t in DCF-MVPM modulation waveform_H0minAnd low level duration t in the DCF-MVPM modulation waveform_L0minBoth are determined by the signal bandwidth, i.e.:

wherein W is the bandwidth of DCF-MVPM modulation.

5. The pwm dimming method for a fixed duty cycle variable period modulation system in visible light communication according to claim 3, wherein:

basic pulse duration t in DCF-MVPM modulation waveform_H0Duration t of the basic low level in the DCF-MVPM modulation waveform_L0The specific method for selecting comprises the following steps:

basic pulse duration t in DCF-MVPM modulation waveform_H0And a substantially low level duration t in the DCF-MVPM modulation waveform_L0Both and LED rise time t_rAnd a falling time t_fIn connection with, the t_H0And t_L0According to the formula:

obtaining; wherein f is_cIs the cut-off frequency, t, of the LED_rFor LED rise time, t_fIs the LED fall time;

if t is_H0＝t_L0Then t_H0And t_L0Expressed as:

Technical Field

The invention relates to a dimming method of pulse width modulation.

Background

In recent years, due to the characteristics of low cost, no harm to human bodies, no need of frequency band application, electromagnetic interference resistance and the like of the visible light communication based on the LED, the visible light communication has attracted extensive attention of researchers along with the popularization of the LED.

Unlike conventional communication, visible light communication requires communication to be first achieved under conditions that satisfy lighting. Currently, it is one of the hot spots to study how to adjust the light in the process of ensuring the data transmission rate. Conventional modulation schemes, such as OOK, PPM, etc., used for visible light communication, may cause a low level or a high level state to continue for a certain period of time during data transmission. The problem of flickering of the light source occurs in the application. Run-length limited coding or modified modulation schemes are commonly used to address this problem, such as manchester coding, 4B6B coding, 8B10B coding, and VPPM. For the dimming support of visible light communication, methods such as Continuous Current Reduction (CCR), Pulse Width Modulation (PWM), idle mode or compensation time insertion (ID/CTI) are generally used. However, since the response speed of the LED is limited by long rise and fall times, the data transmission rate in the visible light communication system is limited. Using run-length limited coding for flicker mitigation, inserting a back-off time to support dimming control, dimming control range for varying duty cycle, etc. will reduce the maximum achievable data transfer rate. For bandwidth limited systems, the impact of this rate of reduction is very large.

Disclosure of Invention

The invention provides a pulse width modulation dimming method for a fixed duty ratio variable period modulation system in visible light communication, aiming at solving the problem that the bandwidth utilization rate is low because different information cannot be distinguished according to different time lengths of sending signals under the condition of fixed duty ratio in visible light communication.

The pulse width modulation dimming method for a fixed duty ratio variable period modulation system in visible light communication changes the pulse duration under the condition of keeping the transmission time of a symbol unchanged so as to control the brightness change, and the signal emission method comprises the following specific steps:

step one, carrying out DCF-MVPM modulation on original information by using a DCF-MVPM modulation system to obtain a signal after the DCF-MVPM modulation;

step two, performing pulse width modulation on the signal obtained in the step one after the DCF-MVPM modulation to obtain a signal after the pulse width modulation;

thirdly, performing analog/digital conversion on the pulse width modulated signal obtained in the second step to obtain a digital pulse width modulated signal;

step four, converting the digital pulse width modulated signal obtained in the step three into an optical signal and then transmitting the optical signal;

the signal receiving method comprises the following specific steps:

step five, the transmitting end receives the optical signal in the step four, and performs photoelectric conversion on the received optical signal to obtain an electric signal of the received signal;

step six, conditioning the electric signals of the received signals obtained in the step five to obtain conditioned signals;

seventhly, performing digital/analog conversion on the conditioned signal obtained in the sixth step to obtain an analog signal of a received signal;

and step eight, carrying out DCF-MVPM demodulation on the analog signal of the received signal obtained in the step six to obtain transmitted original information, and finishing a communication process.

The invention relates to a brightness control method based on pulse width modulation of DCF-MVPM modulation, which judges different information according to different time lengths of sending signals, improves the bandwidth utilization rate, and has the functions of inhibiting light source flicker and adjusting brightness.

Drawings

FIG. 1 is a flow chart of a dimmable DCF-MVPM modulation system.

Fig. 2 is a diagram of the dimming range of the present invention.

Detailed Description