Browse Prior Art Database

PN TDMA Demodulator

IP.com Disclosure Number: IPCOM000090187D
Original Publication Date: 1969-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Blasbalg, H: AUTHOR [+3]

Abstract

The drawing diagrams the PN signal, IF carrier and data extraction operation of the demodulator in a PN-IDMA modem. The demodulator operates at an IF frequency and not at the base band frequency which is commonly used by PN demodulators.

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PN TDMA Demodulator

The drawing diagrams the PN signal, IF carrier and data extraction operation of the demodulator in a PN-IDMA modem. The demodulator operates at an IF frequency and not at the base band frequency which is commonly used by PN demodulators.

The demodulator has a double arm, double mixing section which is used to extract the desired signals. The outputs of the matched filters are multiplied and generate the clock frequency is which locks up phase lock loop 1 PLL 1 from which all data timing is derived. As long as the local IF frequency fO is sufficiently close to the received frequency, the signals pass through the matched filters. The mixing operation at the output of the matched filters cancels out the arbitrary phase which helps the PN clock lock in phase. If the referenced PN signal is out of phase with the incoming signal, the spread spectrum signal is fed into a narrow bandpass filter generating a random signal at the output of the matched filters rather than the sinusoidal component fs. Phase lock lop 2 PLL is used to track the incoming carrier. To perform this function, the signal 3fs is used which is an output of the double arm double mixing stage. The output of PLL 2 is fed back into the second mixing stage of the double arm, double mixing section and allows the demodulator to track doppler effects within the incoming signal, therefore, eliminating the effect of doppler shift in the receiver.

Sync acquisition is obtained by monitoring th...