US 5,974,087 AGranted

Waveform quality measuring method and apparatus

AssigneeAdvantest Corporation

InventorKenji Nowara

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Abstract

A complex base band signal b of a send signal from a mobile station of the CDMA system is obtained, then a portion of the complex base band signal is normalized in amplitude, and the normalized signal is synchronized with a PN code and the time reference is estimated. A frequency error is estimated from a complex correlation value used for the estimation of the time reference. The normalized signal is corrected corresponding to the estimated frequency error, and the corrected signal is used to estimate and correct the initial phase. The corrected signal and the time reference are used to estimate a time lag between a symbol point and the sample point nearest thereto and a reference signal displaced by the time lag is generated. The reference signal and the corrected signal are used to estimate the remaining frequency error and initial phase by the least squares method. All the estimated values are used to correct the signal b, and the corrected signal and the reference signal are used to calculate the waveform quality.

Claims6

Dependent claims

A waveform quality measuring method in which an input signal is converted to a digital signal, said digital signal is converted to a first complex base band signal, an error parameter in said first complex base band signal is corrected to obtain a corrected complex base band signal, and said corrected complex base band signal and a reference signal are used to measure the waveform quality of said input signal, said method comprising:

(a) a time reference extracting/frequency error estimating step of synchronizing said first complex base band signal and a local code sequence to obtain a first signal delay value and a first frequency error;
(b) a first correcting step of correcting said first complex base band signal based on said first frequency error to obtain a second complex base band signal;
(c) an initial phase estimating step of estimating a first initial phase of a carrier from said second complex base band signal;
(d) a second correcting step of correcting said second complex base band signal based on said first initial phase to obtain a third complex base band signal;
(e) a symbol point estimating step of calculating a second signal delay value, which is a time lag between a symbol point and a sample point nearest thereto, from said third complex base band signal, said first signal delay value and said local code sequence;
(f) a reference signal generating step of generating a reference signal, which has a time lag of said second signal delay value relative to said sample point, from said first signal delay value, said second signal delay value and said local code sequence;
(g) a frequency/initial phase estimating step of estimating a second frequency error and a second initial phase of said carrier from said reference signal and said third complex base band signal;
and
(h) a third correcting step of correcting said first complex base band signal based on said first and second frequency errors and said first and second initial phases of said carrier to obtain said corrected complex base band signal.

6 more elements

A waveform quality measuring apparatus in which an input signal is converted to a digital signal, said digital signal is converted to a first complex base band signal, an error parameter in said first complex base band signal is corrected to obtain a corrected complex base band signal, and said corrected complex base band signal and a reference signal are used to measure the waveform quality of said input signal, said apparatus comprising:

time reference extracting/frequency error estimating means for synchronizing said first complex base band signal and a local code sequence to obtain a first signal delay value and a first frequency error;
frequency correcting means for correcting said first complex base band signal based on the first frequency error to obtain a second complex base band signal;
initial phase estimating means for estimating a first initial phase of a carrier from said second complex base band signal;
phase correcting means for correcting said second complex base band signal based on said first initial phase to obtain a third complex base band signal;
symbol point estimating means for estimating a second signal delay value, which is a time lag between a symbol point and a sample point nearest thereto, from said third complex base band signal, said first signal delay value and said local code sequence;
reference signal generating means for a reference signal, which has a time lag of said second signal delay value relative to said sample point, from said first signal delay value, said second signal delay value and said local code sequence;
frequency/initial phase estimating means for estimating a second frequency error and a second initial phase of said carrier from said reference signal and said third complex base band signal;
and
frequency error/initial phase correcting means for correcting said first complex base band signal based on said first and second frequency errors and said first and second initial phases to obtain said corrected complex base band. signal.

6 more elements

Dependencies are inferred from the claim text.