23 Quadrature Modulator Hardware carrier filter filter Asin φ x sin θ Acos φ x

23 quadrature modulator hardware carrier filter

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23 Quadrature Modulator Hardware carrier filter filter Asin φ x sin θ Acos φ x cos θ Acos φ x cos θ - Asin φ x sin θ = Acos( φ + θ )
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 24 Quadrature Demodulation The receiver can recover the two independently modulated signals, even though they share the same carrier frequency. Q I
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 25 Vector Signal Analyzer Measurements Modulation Quality Analysis Input Signal Analyzer Display Measurement Analysis I Q I Q Q I QPSK 8PSK 16QAM etc… RF Input Mixer Local Oscillator IQ Demod Digital IF Error Vector Magnitude Ratio of Measured Amplitude to Intended Amplitude (%) Magnitude Error = “IQ Error Magnitude” Measured Signal Intended Signal Phase Error = “IQ Error Phase” Q I φ Unit Circle RCE (dB) = 20 log(EVM in %/100)
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 26 I/Q Modulator Impairments Contributions to EVM I offset Q offset LO I Q RF Baseband generator G I 90°+ θ e Modulator imbalance Origin Offset Quadrature Error φ c
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 27 Origin Offset Example 16-QAM Constellation I Q
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 28 Quadrature Error Examples QPSK Constellations
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 29 Modulator Imbalance Examples QPSK Constellations Excess I gain and reduced Q gain relative to ideal constellation Ideal Excess I Gain Excess Q Gain
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 30 Power Amplifier Nonlinearity Another Contributor to EVM
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 31 ISI – Inter Symbol Interference 1100 1101 1110 1111 1000 1001 1010 1011 0100 0101 0110 0111 0000 0001 Noise Expected Symbol Position Delayed Received Symbol Q +1V 0011 0010 Symbol Boundary I +1V -1V -1V
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 32 Constellation Display Is a Composite of all OFDM Sub-carrier Symbols …f n Individual Sub-carriers f 5 f 4 f 3 f 2 f 1 QPSK Constellation Display at T = t 0 Q I 16QAM BPSK
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 33 Constellation Display Is a Composite of all OFDM Sub-carrier Symbols… and time t 2 t 0 Q I Q I Q I Q I Q I Q I Q I Q I Q I Q I Q I Q I Symbols vs. Time …t n t 4 t 3 t 2 t 1 Constellation Display Q I t 1
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc.
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