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Orthogonal Function Modem Receiver

IP.com Disclosure Number: IPCOM000095357D
Original Publication Date: 1965-Dec-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 39K

Publishing Venue

IBM

Related People

Zappe, H: AUTHOR

Abstract

The modem is of the type in which several bits are transmitted in parallel. Each bit is characterized by one function taken out of an orthogonal function set. Two functions f (t) and g (t) are orthogonal if they satisfy the condition (Image Omitted)

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Orthogonal Function Modem Receiver

The modem is of the type in which several bits are transmitted in parallel. Each bit is characterized by one function taken out of an orthogonal function set. Two functions f (t) and g (t) are orthogonal if they satisfy the condition

(Image Omitted)

Across the transmission line output the filter being considered a part of the line there is collected a substantially elongated function of duration T + Delta. Owing to the fact the received functions are of finite duration T + Delta a Fourier analysis can be sufficient within the interval. The analysis functions are then sine and cosine functions of the same frequency as the transmit functions and go to 0 outside time interval T+Delta.

The receiver is composed of a delay line of duration T + Delta provided with some number of taps. Parallel weighting resistor sets representing each analysis function are connected to the taps. Currents flowing into resistors of each group are added into a current adder.

The message is reassembled from the adders' outputs at the very moment the received function through the transmission line completely enters the delay line. The receiver can be used directly as transmitter in the case of half-duplex transmission.

As the transmission line transfer function is a priori arbitrary it results in phase and amplitude distortion of the overall spectrum transmitted. This appears as amplitude variation and phase shift of the frequencies analyzed by the receiver. Owing to this fact, equalization is effected at the output of each channel.

If the channel C(i...