Single-double-path modulation and demodulation method, and singl-double-path modem thereof
A technology of modem and modulation method, which is applied in transmission systems, electrical components, distribution line transmission systems, etc., and can solve problems such as complex circuits, high hardware costs, and complex software
Inactive Publication Date: 2006-03-15
XUJI GRP
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Problems solved by technology
[0002] At present, the Weaver modulation technology adopted by domestic counterparts and German Siemens company only transfers the audio signal to the intermediate frequency signal through Weaver modulation, and then uses analog devices and phase-locked loop technology for high-frequency modulation. This high-frequency modulation requires an expensive Crystal bandpass filter, at the same time, due to the need for a phase-locked loop, the requirements for the power supply are relatively high, and the anti-interference ability is poor. This method has complex circuits, high cost, and low reliability.
When performing dual-channel modulation, domestic manufacturers and Siemens generally use two intermediate frequency carrier frequencies for Weaver modulation and demodulation, and use two sets of identical plug-ins to complete dual-channel modulation and demodulation (such as figure 1 shown), this method has high hardware cost and complicated software
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[0099] Modulation part of single channel:
[0100] Voice and telecontrol signals are converted into digital signals after being sampled at a rate of 8kHz, unnecessary frequency components are filtered out by digital filters, and then added to the pilot signal generated inside the digital signal processor DSP to obtain a composite signal, and then processed Orthogonal subcarrier modulation (subcarrier frequency is 2kHz), the modulated signal is filtered through a pair of digital low-pass filters with the same amplitude and phase to filter out frequency components above 2.3kHz, and then two interpolation filters are performed, one is 16 times, one time is 12 times, the sampling rate is changed from 8kHz to 1536kHz, and finally the signal is modulated into the required working frequency band by the method of direct digital frequency synthesis.
[0101] Two-way modulation part:
[0102] The voice, telecontrol, and pilot of each channel are added to obtain a composite signal, and ...
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The method and the modem are applicable to the power line carrier communication. The modem comprises two routes of A / D and D / A converters, the digital signal processor DSP1, the digital signal modulation processor DSP3 the digital signal demodulation processor DSP2, the high speed D / A converter and the high speed A / D converter. The A / D and D / A converters are connected to DSP1. The digital signal transferred from the analog signal to be modulated by the two route A / D converters is sent to the DSP1 for filtering and mixing process. The processed two route signals through DSP3 and the high speed D / A converter are modulated to the working frequency band desired. The signal to be demodulated through the high-speed A / D converter, DSP2 is connected to the DSP1.
Description
technical field [0001] The present invention relates to a modulation and demodulation method and its modem, in particular to a modulation and demodulation method and its modem for power line carrier communication. Background technique [0002] At present, the Weaver modulation technology adopted by domestic counterparts and German Siemens company only transfers the audio signal to the intermediate frequency signal through Weaver modulation, and then uses analog devices and phase-locked loop technology for high-frequency modulation. This high-frequency modulation requires an expensive Crystal band-pass filter, at the same time, requires a phase-locked loop, has relatively high requirements on the power supply, and has poor anti-interference ability. This method has complex circuits, high cost, and low reliability. When performing dual-channel modulation, domestic manufacturers and Siemens generally use two intermediate frequency carrier frequencies for Weaver modulation and d...
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IPC IPC(8): H04B3/54H04B1/04
Inventor 王奎甫黄芝平王跃科薛民
Owner XUJI GRP