AN ASSESSMENT OF THE BIT-ERROR-RATE ... - SpaceOps

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Table 2. Ground Terminal Distortion Settings Parameter Value Bandwidth, MHz 650 (3 dB BW) Roll-off, dB/MHz 6 th order Butterworth roll-off Gain Flatness (peak-to-peak), dB 1.2 over ±230 MHz Gain Slope, dB/MHz 0.1 Phase Nonlinearity (peak-to-peak), ° 30.0 over ±230 MHz AM/AM, dB/dB 0.9 AM/PM, °/dB 1.0 Spurious Outputs, dBc Not Simulated 1 Hz – 10 Hz: ≤1.4 10 Hz – 100 Hz: ≤1.4 Phase Noise, ° rms 100 Hz – 1 kHz: ≤2.7 1 kHz – 400 MHz: ≤1.0 (see notes 3 and 4) Notes: 1. TDRS H, I, J Ground Segment includes the antenna and the Interfacility Link (IFL) equipment. 2. Ka-Band Infrastructure includes equipment just after the IFL equipment and up to the IF output (includes the waveguide equalizer and downconverter). Note that the ground terminal modifications provide KaSAR 650 MHz service support up to a 1.2 GHz IF. This analysis assumed receiver equipment after the 1.2 GHz IF so that a BER analysis could be performed. 3. Phase noise amounts selected prior to finalization of KaTP Specification [2]. 4. In addition to this phase noise, additional phase noise due to the carrier tracking loop VCO was also simulated. This carrier tracking loop VCO phase noise contributed to the total untracked phase error an amount of 0.33° rms. Phase (degrees) Figure 5. Ground Terminal Phase Nonlinearity Scenarios Random Shape 1 Random Shape 2 20 15 10 5 0 -230 -184 -138 -92 -46 0 46 92 138 184 230 -5 -10 -15 -20 Frequency (MHz) -6-
2.3 Simulation Approach The Signal Processing Worksystem (SPW) software was used to develop the TDRSS KaSAR 650 MHz service simulation models. Figure 6 provides a block diagram overview of the KaSAR 650 MHz service end-to-end link simulation model. Figure 7 provides an overview of the ground terminal simulation model assumed for this analysis. Figure 6. TDRSS KaSAR 650 MHz Service End-to-End Link Simulation Model Customer Customer Transmitter Transmitter + TDRS TDRS HIJ HIJ Spacecraft Spacecraft End-to-End End-to-End Link Link AWGN AWGN Reference Data Customer Transmitter Customer Transmitter • User-configurable data rate • User-configurable data rate • User-configurable distortions • User-configurable distortions - Gain imbalance - Gain imbalance - Phase nonlinearity - Phase nonlinearity - Spurs - Spurs - AM/AM and AM/PM - AM/AM and AM/PM - Phase Noise - Phase Noise -Etc. -Etc. Input Filter Nonlinear Distortions (due to all Gnd Term H/W components) TDRS HIJ Spacecraft TDRS HIJ Spacecraft • Linear and nonlinear distortions • Linear and nonlinear distortions based upon TDRS H Spacecraft based upon TDRS H Spacecraft Thermal Vacuum (SCTV) Thermal Vacuum (SCTV) measurement data measurement data - Channel magnitude response - Channel magnitude response - Channel phase response - Channel phase response - AM/AM and AM/PM - AM/AM and AM/PM - Phase Noise - Phase Noise Figure 7. Ground Terminal Simulation Model Linear Distortions (due to all Gnd Term H/W components) 2.4 Analytical Approach For some distortions analytical methods were used to determine the impact to BER. The methods used were based upon the material presented in the NASA/GSFC report titled The Impact of TDRSS User Constraint Parameters on Bit Error Rate Performance [3]. While the methods documented in Reference [3] are directly applicable to QPSK, they can be expanded upon or used as an approximation for GMSK, 8PSK and 8PSK/TCM. The impact of an untracked phase error on QPSK was determined based upon material presented in the NASA/GSFC report titled TDRSS and TDRS II Phase Noise Analysis Final Report [4]. -7- + Demodulator (Carrier Tracking Loop) Ground Ground Terminal Terminal Ground Terminal Ground Terminal • Linear distortions • Linear distortions • Receiver model based upon • Receiver model based upon TDRSS existing high data rate TDRSS existing high data rate receiver receiver • Carrier tracking • Carrier tracking • Symbol synchronization • Symbol synchronization • Equalization • Equalization Bit Synchronizer BER BER BER Estimator Estimator BER Estimator BER Estimator Eb/No Customer Receiver Equalizer • Type: Butterworth • Gain flatness: 0.6 dB peak • Loop order: Second • Order: Sixth • Gain Slope: 0.1 dB/MHz • Loop damping: 0.707 • Bandwidth: 650 MHz • Phase nonlinearity: 30.0° p-to-p • Loop BW: 2.160 kHz (1) • Detection method selectable • Baseband equalizer between a 3 can be switched in rd order Butterworth filter (2) or integrate-and-dump detector • For QPSK, timing derived from distorted input signal. For 8PSK, 8PSK/TCM and GMSK, ideal timing assumed (3) • Type: Butterworth • AM/AM: 0.9 dB/dB • Gain flatness: 0.6 dB peak • Loop order: Second • Order: Sixth • AM/PM: 1.0°/dB • Gain Slope: 0.1 dB/MHz • Loop damping: 0.707 • Bandwidth: 650 MHz • Phase nonlinearity: 30.0° p-to-p • Loop BW: 2.160 kHz Notes: 1. Bandwidth assumed. 2. Bandwidth set for optimal detection (0.55 x symbol rate). Filter followed by a sample-and-hold. 3. For 8PSK, 8PSK/TCM and GMSK, bit synchronizer transition tracking loop not simulated. Degradations due to I/Q data skew, data asymmetry, data bit jitter and data bit jitter rate addressed analytically. (1) • Detection method selectable • Baseband equalizer between a 3 can be switched in rd order Butterworth filter (2) or integrate-and-dump detector • For QPSK, timing derived from distorted input signal. For 8PSK, 8PSK/TCM and GMSK, ideal timing assumed (3) • AM/AM: 0.9 dB/dB • AM/PM: 1.0°/dB Notes: 1. Bandwidth assumed. 2. Bandwidth set for optimal detection (0.55 x symbol rate). Filter followed by a sample-and-hold. 3. For 8PSK, 8PSK/TCM and GMSK, bit synchronizer transition tracking loop not simulated. Degradations due to I/Q data skew, data asymmetry, data bit jitter and data bit jitter rate addressed analytically.
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Page 3 and 4: for this analysis (random shapes we
Page 5: Power Out, dB Phase Change, degrees
Page 9 and 10: Table 3. Summary of Expected Implem

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