Browse Prior Art Database

Frequency Division Multiplexing and Demultiplexing Utilizing Sampled Data Filters

IP.com Disclosure Number: IPCOM000094835D
Original Publication Date: 1965-Jun-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 3 page(s) / 78K

Publishing Venue

IBM

Related People

Thrasher, PM: AUTHOR

Abstract

Drawing A shows a communication system capable of frequency division multiplexing and demultiplexing M different channels each having an arbitrary bandwidth of zero to f/2. Each channel 1... M is fed into a low-pass filter 2. Filters 2 insure the band limitation of the channel input signals to frequencies ranging between zero and f/2. The band-limited signals at 4 are then sampled by sample gates 6 at a repetition 8 is periodic with frequency and therefore contains redundant information. The spectrum comprises the baseband zero to f/2 as well as the upper and lower sidebands distributed along the frequency axis at points separated by f cycles.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 3

Frequency Division Multiplexing and Demultiplexing Utilizing Sampled Data Filters

Drawing A shows a communication system capable of frequency division multiplexing and demultiplexing M different channels each having an arbitrary bandwidth of zero to f/2. Each channel 1... M is fed into a low-pass filter 2. Filters 2 insure the band limitation of the channel input signals to frequencies ranging between zero and f/2. The band-limited signals at 4 are then sampled by sample gates 6 at a repetition 8 is periodic with frequency and therefore contains redundant information. The spectrum comprises the baseband zero to f/2 as well as the upper and lower sidebands distributed along the frequency axis at points separated by f cycles.

Following the sampling process, the signals at 8 are fed to a series of sampled data filters 10, which collectively comprise a synthesizer. In the synthesizer, the channel signals are convolved with appropriate transfer functions to effectively perform filtering operations. Filters 10 each pass a unique, but different, region of the baseband or sideband of their respective channels. The filter outputs at 12 are then combined to form a wide-band frequency multiplexed signal at 14. The information content of the M channels is now divided among the base-band and sidebands of the wide-band signal. This signal contains no redundant information within the range of zero to M(f/2). The frequency multiplexed wide-band signal at 14 is converted into a continuous wide-band signal at 16 by low-pass filter 15. The continuous wide-band signal is then transmitted to the receiving station.

At the receiving station, the received continuous wide-band signal is again filtered in low-pass filter 17 to form a filtered wide-band signal at 18. The signal at 18 is then sampled at a repetition rate of Mf by sample gate 19. This produces a signal at 20 having a baseband of zero to M(f/2) and pairs of upper and lower sidebands spaced along the frequency spectrum at points separated by M(f/2). The sampled signals at 20 are each fed into their respective sampled data filters 22 where they are convolved as in the synthesizer. Each filter 22 passes the baseband or sideband assigned to that particular channel. However, since the sampling of the wideband signal at 18 is at a rate M times greater than required for a bandwidth of f/2, the spectrums of the signals at 24 contain redundant information as well as blank bands along the frequency axis. To return the spectrums of the signals at 24 to their former spectral configurations as they appear in the synthesizer at 8, the signals 24 are re-sampled at the rate of f. Finally, the re-sampled signals at 26, which have the spectral configuration of the signals at 8, are fed into l...