| 摘要 |
PURPOSE: A demodulator in a digital television receiver is provided to down-convert a frequency band without using a down-converter by sampling directly IF(intermediate frequency) signal with 1.5fs and subtracting a baseband signal effectively by a match filter. CONSTITUTION: The demodulator in a digital television receiver includes a first and second multipliers, a first and second match filter, a coefficient memory(48), a complex multiplier(50) and an address generator. The first and second multipliers receives digital television signal samples which are sampled at a sampling frequency corresponding to a one and half of a symbol frequency, multiples a cosine function and a sine function at a first frequency, respectively, and outputs an in-phase and a quad-phase signal including a baseband signal, respectively. Each of the first and second match filters includes M filter taps and base band filters the outputs of the first and the second multipliers, respectively. Each of the coefficient memory(48) includes M memories storing N filter coefficients, and supplies M filter coefficients corresponding to the address in the M memories to a filter taps corresponding to the first and the second match filters. The complex multiplier(50) multiplies the output of the first and second match filters with the complex signal at the second frequency and outputs a real demodulation signal and an imaginary demodulation signal. The address generator detects a sample timing error and generates the address corresponding to the sample timing error.
|
