四、請以理論搭配實例說明公共組織與私人組織的異同。(本題 25 分)

(i) (2%) Analog communication is preferred over digital in long distance communication since we can decode and retransmit analog signals when the signal-to-noise ratio (SNR) is large.

(ii) (2%) As long as the sampling frequency is larger than 2 times the signal bandwidth, one can easily reconstruct the original signal from samples.

(iii) (2%) Split phase line coding can provide self-synchronization.

(iv) (2%) For sending a same signal, linear modulation typically requires a larger bandwidth than angle modulation.

(i) (5%) Pass the received signal through an ideal bandpass filter centered at \( f_{c} \) with bandwidth \( B \geq 2W \). The noise then becomes \( n_{c}(t) \cos 2\pi f_{c}t - n_{s}(t) \sin 2\pi f_{c}t \) narrowband noise. Draw \( S_{n_c}(f) \) the PSD of \( n_{c}(t) \).

(ii) (8%) The output signal now is \( y(t) = x(t) + n_c(t) \cos 2\pi f_c t - n_s(t) \sin 2\pi f_c t \). Use a coherent demodulator followed by a low-pass filter with bandwidth \( W \) to demodulate it. Derive the demodulation signal and the SNR at the demodulator output.

(iii) (8%) Suppose the signal is further corrupted by an interference \( k(t) = \text{sinc}(wt) \) and the received signal after the bandpass filter becomes \( y_2(t) = (t) + k(t) \cos 2\pi(f_c + 2W)t + n_c(t) \cos 2\pi f_c t - n_s(t) \sin 2\pi f_c t \). Design a low-pass filter for the demodulator in part ii) such that the signal-to-interference-plus-noise ratio (signal power divided by the sum of interference and noise power) is maximized.

(i) (5%) Derive the condition on \( h(t) \), in time domain, such that there will be no inter-symbol interference?

(ii) (8%) Now, derive from part i) the condition on \( H(f) \), in frequency domain, which guarantees no inter-symbol interference.

(iii) (8%) Provide an example of \( H(f) \) satisfying the condition in part ii). Show in time domain that it indeed will not result in any inter-symbol interference.

115年 - 115 國立臺北大學_碩士班一般入學考試試題_公共行政暨政策學系甲組(公共行政組)：行政學#146617

114年 - 114 中央警察大學_碩士班入學考試試題_警察政策研究所：行政法#146848

110年 - 110 國立臺北大學_碩士班一般入學考試試題_公共行政暨政策學系甲組(公共行政組)：行政學#147265

110年 - 110 國立政治大學_碩士班暨碩士在職專班招生考試試題_法律學系/公法甲組：行政法#123561

110年 - 110 中央警察大學_碩士班招生考試_警察政策研究所：行政法#102840

110年 - 110 國立臺灣大學_碩士班招生考系所_部份系所:行政法(B)#102119

110年 - 110 國立臺灣大學_碩士班招生考試_公共事務研究所:行政法(A)#100318

110年 - 110東吳大學_碩士班招生考試_法律學系︰行政法#100029

110年 - 110 國立政治大學_碩士班暨碩士在職專班招生考試_法律學系／公法甲組：行政法#99179

109年 - 109 國立高雄大學_碩士班招生考試_法律學系(丙組(公法組))、政治法律學系(公法組)：行政法#103024