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Wireless laser communication PPM polarization modulation and demodulation method

A polarization modulation and demodulation method technology, applied in the field of communication, can solve the problems of short communication distance, low speed, easy to be affected by atmospheric random channels, etc., and achieve the effect of overcoming the influence and improving the code rate and transmission distance.

Inactive Publication Date: 2008-01-23
XIAN UNIV OF TECH
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Problems solved by technology

[0004] The purpose of the present invention is to provide a wireless laser communication PPM polarization modulation and demodulation method to solve the problems of low code rate, short communication distance and vulnerability to atmospheric random channels in the existing wireless laser communication

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  • Wireless laser communication PPM polarization modulation and demodulation method
  • Wireless laser communication PPM polarization modulation and demodulation method
  • Wireless laser communication PPM polarization modulation and demodulation method

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Embodiment Construction

[0019] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0020] The existing pulse position modulation (PPM) method is to map a group of binary n-bit data groups into a single pulse signal at a certain time slot on a time period consisting of 2n time slots. This modulation method is essentially is a phase modulation.

[0021] Record the n-bit data group as M=(m 1 , m 2 ,...,m n ), this mapping relationship can be expressed by the following formula:

[0022] Φ: L=m 1 +2m 2 +......+2 n-1 m n ∈(0,1,2,...,2 n-1 ) In the formula, L represents the position number of the time slot.

[0023] which is:

[0024]

[0025] where S n (t) represents the modulation signal, P C stands for pulse power, T C Represents the length of the slot.

[0026] For example for a 4-PPM:

[0027] If M=(0,0), then L=0; if M=(1,0), then L=1;

[0028] If M=(0,1), then L=2; if M=(1,1), then L=3;

[0029] 0, 1...

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Abstract

The present invention relates to a wireless laser communication PPM polarization modulation- demodulation method, which creates one-to-one correspondence between a PPM signal of an information source and an elliptic polarizing angle. Based on the correspondence, the signal of the information source is modulated into an elliptic polarized light with a corresponding elliptic polarizing angle and emits the light in the form of an optical signal. During demodulation, the polarizing angle of the received elliptic polarized light is calculated to confirm information of the information source corresponding to the polarizing angle according to the correspondence above and then complete information demodulation. The modulation-demodulation method overcomes impact of atmospheric channel on communication and effectively eliminates lower communication code rate and short communication distance of wireless laser communication.

Description

technical field [0001] The invention belongs to the technical field of communication, and in particular relates to a PPM polarization modulation and demodulation method for wireless laser communication. Background technique [0002] Modulation and demodulation is a key technology in wireless laser communication. At present, there are two main modulation and demodulation systems in wireless laser communication, one is intensity modulation / direct detection (IM / DD) system, and the other is coherent Modulation / heterodyne detection system. In the IM / DD system, the transmitting end obtains the modulated signal by directly modulating the intensity of the optical carrier, and the optical signal is directly converted into an electrical signal by using a photodetector at the receiving end. The direct detection system has the advantages of small size, light weight, simple structure, low cost, and easy implementation, but its frequency band utilization rate is low, and the receiving se...

Claims

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Application Information

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IPC IPC(8): H04B10/12G02F1/35H04B10/556
Inventor 柯熙政刘健
Owner XIAN UNIV OF TECH
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