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METHOD FOR SUPPRESSING SPUR INTERFERENCE IN MULTI-SUB-CHANNEL RECEIVERS USING FREQUENCY-INTERPOLATED PILOTS

IP.com Disclosure Number: IPCOM000007574D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2002-Apr-08
Document File: 2 page(s) / 97K

Publishing Venue

Motorola

Related People

Gregory W. Cox: AUTHOR

Abstract

Portable computing devices such as notebook computers, personal digital assistants (PDA), and the like produce electromagnetic interference (EMI). These emissions are due to internal electrical sig- nals such as clocks, data busses, and control lines changing state and radiating. These signals which are radiated can have spectra1 components which may interfere in frequency bands used for data trans- mission. The following method provides a means to suppress the effects of narrow-band emissions or spurs for receivers of multi-subchannel modulation sys- terns employing time and frequency interpolated pilots (a form of Pilot Symbol Assisted Modulation or PSAM) as a means of carrier recovery. These receivers may act as a peripheral device to such port- able computing equipment and thus be subject to spur interference. In most cases, the compactness dictated by the portable computer market forces the receive antenna to be physically close to the com- puter, compounding the spur interference problem.

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MOlVROLA Technical Developments

METHOD FOR SUPPRESSING SPUR INTERFERENCE IN MULTI-SUB-CHANNEL RECEIVERS USING FREQUENCY-INTERPOLATED PILOTS

by Gregory W. Cox

BACKGROUND or PSAM) as a means of carrier recovery. These receivers may act as a peripheral device to such port- Portable computing devices such as notebook able computing equipment and thus be subject to computers, personal digital assistants (PDA), and the spur interference. In most cases, the compactness like produce electromagnetic interference (EMI). dictated by the portable computer market forces the These emissions are due to internal electrical sig- receive antenna to be physically close to the com- nals such as clocks, data busses, and control lines puter, compounding the spur interference problem. changing state and radiating. These signals which
are radiated can have spectra1 components which Figure 1 below show an example pilot and data may interfere in frequency bands used for data trans- symbol placement scheme for frequency-interpolated mission. The following method provides a means to pilots. Note that all symbols, pilots and constants in suppress the effects of narrow-band emissions or spurs this discussion are complex-valued. In this exam- for receivers of multi-subchannel modulation sys- pie, pilots can be shared between subchannels (inter- terns employing time and frequency interpolated polation in frequency) to increase the effective sam- pilots (a form of Pilot Symbol Assisted Modulation pling rates for channel effects such as flat fading.

INCREASING

FREQUENCY

I

INCREASING TIYE *

Fig. 1 Example Data and Pilot Symbol Placement

An estimate of channel effects is obtained by interpolating channel gain at known pilot symbol

instants to form a channel gain estimate &, for each data symbol Dk, , as follows:

'k,l = f f OLi,j,k,l (5) i=O j...