Method for measuring modulation parameters of digital quadrature

Details Method for measuring modulation parameters of digital quadrature Method for measuring modulation parameters of digital quadrature

1997-04-25

1998-08-25

Chin, Wellington

Pulse or digital communications

Testing

375226, 375324, 370203, 370208, 455 671, H04B 346

Patent

active

057990387

ABSTRACT:
The signal to be measured is converted into digital form and read into a memory 13 using a trigger as the reference, and a signal of a length 1/5 that of the signal to be measured, in the vicinity of the trigger, is orthogonal-transformed (14). A frequency error .omega..sub.1 of the transformed output I.sub.1,Q.sub.1 is estimated (15) and is used to correct the output I.sub.I, Q.sub.I (16). The corrected output I.sub.2,Q.sub.2 is subjected to processing by a receiving filter (17), and the filtered output I.sub.3,Q.sub.3 is synchronized with a PN code to obtain an ideal signal R.sub.I,R.sub.Q and a phase difference .tau..sub.1 is calculated. The signal I.sub.3,Q.sub.3 and the ideal signal R.sub.I,R.sub.Q are used to obtain a frequency error .omega..sub.2 and a phase error .tau..sub.2 of the signal I.sub.3,Q.sub.3. All signals to be measured, stored in the memory 13, are subjected to orthogonal transformation (23) so that the frequency error .omega..sub.1 +.omega..sub.2 and the phase error .tau..sub.1 +.tau..sub.2 are removed, and the transformed output I.sub.5,Q.sub.5 and the signal R.sub.I,R.sub.Q are used to calculate modulation parameters as is the case with the prior art.

REFERENCES:
patent: 5001724 (1991-03-01), Birgenheier et al.
patent: 5187719 (1993-02-01), Birgenheier et al.
patent: 5692009 (1997-11-01), Lijima
patent: 5732105 (1995-07-01), Andren et al.

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