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DEVIATION MONITORING AND FEEDBACK TO IMPROVE COVERAGE

IP.com Disclosure Number: IPCOM000006556D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2002-Jan-14
Document File: 2 page(s) / 94K

Publishing Venue

Motorola

Related People

Bob Stengel: AUTHOR [+2]

Abstract

For a Frequency Modulated (FM) signal the range or coverage. However, when the transmitter car- recovered message signal amplitude is directly related rier is 60 dB or higher than the noise (C/N), adjacent to the modulation index or deviation of the transmitted channel noise is reduced with a reduction in the FM signal. Thus, keeping the modulation signal at the maxi- deviation. The optimum system would decrease trans- mum designed deviation value would result in the highest mitter deviation to the minimum for strong C/N condi- received signal to noise (S/N) ratio. When a transmit- tions (C/N > 60 dB), and increase transmitter deviation ter is at the threshold range of a communications sys- to the maximum for weak C/N conditions. tern, maximum deviation is desirable to provide the most Sinad = signal + noise + distortion noise + distortion Figure 1 is a measurement of receiver Sinad versus levels close to the noise sensitivity limit (Sinad = 12 dB). a trunking transmitter signal deviation for three carrier The inbound trunked deviation limits are noted in figure Deviation vs SINAD 20.00 C/N - 7 dB C = -115 dBm DELTA -120 dBm -125 dBm 0.

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MOTOROLA INC. Technical Developments Volume 16 August 1992

DEVIATION MONITORING AND FEEDBACK TO IMPROVE COVERAGE

by Bob Stengel and Roger Davenport

  For a Frequency Modulated (FM) signal the range or coverage. However, when the transmitter car- recovered message signal amplitude is directly related rier is 60 dB or higher than the noise (C/N), adjacent to the modulation index or deviation of the transmitted channel noise is reduced with a reduction in the FM signal. Thus, keeping the modulation signal at the maxi- deviation. The optimum system would decrease trans- mum designed deviation value would result in the highest mitter deviation to the minimum for strong C/N condi- received signal to noise (S/N) ratio. When a transmit- tions (C/N > 60 dB), and increase transmitter deviation ter is at the threshold range of a communications sys- to the maximum for weak C/N conditions.
tern, maximum deviation is desirable to provide the most

Sinad =

signal + noise + distortion

noise + distortion

Figure 1 is a measurement of receiver Sinad versus levels close to the noise sensitivity limit (Sinad = 12 dB). a trunking transmitter signal deviation for three carrier The inbound trunked deviation limits are noted in figure

Deviation vs SINAD

20.00

C/N - 7 dB

C = -115 dBm

DELTA

-120 dBm

-125 dBm

0.

1 1.4 1.B 2.2 2.6 3 3.4 3.8 4.2 4.8

( S/N = signal/(noise+distortion) -3.52 dB 0 dB 2.85 dB delta for C = -115 de,,,

Deviation in KHz

FIGURE 11

112

0 Motorola. 1°C. 1992

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MOTOROLA INC. Technical Developments Volume 16 August 1992

1, at 2.4 to 3.6 KHz. For these deviation limits the receiver is a significant improvement in the recovered signal level recovered Sinad variation was measured from 2 to 3.5 that would result in extended coverage. The S/N can be dB dependent on the received carrier level or C/N. This determined from Sinad using the following relation:

signal

=S/N=Sinad-1

n...