UHF Satcom Adjacent Channel Emissions and Modem Implemention Loss: Predictions/Measurements for the Linear Phase SBPSK Modulation Waveform Family

Belkerdid, M.A.; Mears, T.J.; Weeter, H.T.

doi:10.1109/milcom.2005.1605960

Cited by 2 publications

(2 citation statements)

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“…It was reported [5] that 50% SBPSK has a theoretical ACE margin of 1.7 dB in the 10 kHz offset adjacent channel at 2400 bps in the narrow band mode. For 9600 bps in the wideband mode, this theoretical margin is 1.6 dB in the 50 kHz offset channel.…”

Section: Piece-wise-linear Sbpskmentioning

confidence: 99%

“…SBPSK signals with higher shape factors yield better ACE performance, but suffer higher implementation loss in terms of BER performance. It was reported [5] that 75 % SBPSK yields a minimum of 5 dB of ACE margin over 50% SBPSK at the expense of 1 dB over the 50% DBPSK implementation loss. The shape factor effect on the ACE margin is well described by the plots in Figure 2.…”

Section: Introductionmentioning

confidence: 99%

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New Piece-Wise-Linear SBPSK Modulation Waveform with Robust Adjacent Channel Emissions for UHF SATCOM Channels

Belkerdid

Mears

2006

Milcom 2006

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The MIL-STD-188-181A dictates that all transmissions over US-owned UHF SATCOM channels be adjacent channel emissions (ACE) compliant. The ACE requirements are specified for both the 5 kHz and 25 kHz channels, in terms of relative energy spilling out in adjacent channels above and below the main transmitting channel. The two main modulations recommended by the mil standard are 50% SBPSK and 50% SOQPSK. The SOQPSK technique offers outstanding side lobe suppression such that the ACE requirements are readily met with the standard 50% SOQPSK waveform.. The 50% shaped SBPSK waveform as recommended in MIL-STD-188-181A, however does not offer much ACE margin in the first two 5 kHz offset channels, nor for 9600 bps in the first two 25 kHz offset channels. Hardware limitations may further degrade ACE performance. This paper introduces new phase shaping methods that have far superior ACE suppressions with little or no additional modem implementation loss when the transmitted waveform is demodulated by a coherent BPSK demodulator. The new shaping waveforms introduced in this paper use a piece-wise-linear approach to generate the phase transitions. The phase transitions from zero to π are achieved by using different straight lines with different slopes. There is no phase discontinuity in the transition phase trajectory thus translating to continuous M-ary frequency shift keying type of waveform. The choice of these slopes can predictably reshape the RF modulated power spectral density, thus the slopes control the ACE characteristics of the transmitted RF signal. The transition time can vary from zero to the full baud time, thus achieving the zero to 100 % shaping. The ACE characteristics are predicted by a computer model, then verified via spectral measurement of the transmitted RF signal. This transmitted RF signal is fed to an off-the-shelf RF receiver/demodulator and BER measurements are obtained. Computer simulation results show good agreement with measured experimental results in terms of both ACE characteristics and modem implementation loss.

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Section: Piece-wise-linear Sbpskmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%