THE IMPROVED LEVEL CROSS RATE DOPPLER FERQUENCY ESTIMATOR FOR REMOVED POSSIBLE BIAS AT EXTREMELY LOW VELOCITY

摘要

PURPOSE: A device for estimating an improved level cross rate Doppler frequency to remove a bias at super low speed is provided to count pilot symbol signals by the first and second reference levels, respectively, and to choose a small value among outputted values to estimate a Doppler frequency, thereby preventing noise influence when a portable terminal is in very low speed motion. CONSTITUTION: A level detector(100) detects size of pilot symbol signals. A crossing portion(150) counts level crossings of the signals inputted from the level detector by dual reference levels, chooses a small value among the counted values, and outputs the small value. A dividing portion(140) receives the signal outputted from the crossing portion(150) to calculate the signal, and calculates a Doppler frequency. The crossing portion(150) comprises as follows. The first cross counter(110) detects level crossings from the signals of the level detector(100) based on the first reference level, and counts the level crossings. The second cross counter(120) detects level crossings from the signals based on the second reference level, and counts the level crossings. A minimal detector(130) detects minimal values among the inputted signals, and outputs the detected minimal values.