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本文討論了射頻滤波器带寬比信息带寬大得多的二元制及多元制非相干移頻键控系統。假定射頻滤波器带寬至少是基带匹配滤波器带寬的十倍。得出了作为信道輸入(检波前)信噪比函数的綫性包絡检波器及平方律包絡检波器的信息碼元誤差槪率的表达式。本文第一部分討論了寬带二元制移頻鍵控系統。証明了低信噪比(小于0分貝)时,平方律检波器最好,高信噪此时綫性检波器最好。初步的实驗数据与理論分析相符,在誤差槪率为10~(-4)时两者之差在1/2分貝內。本文第二部分討論了多元制寬带移頻鍵控系統。分析結果表明,对于采用射頻匹配滤波器的多元制移頻鍵控系統来說,也有与上述相同的趋势。証明了在錯字率相同的情况下,所要求的信道信噪比随每个所合信息量的增加而下降。例如,把一个32元制寬带非相干移頻鍵控系統的一个五比特的字与一个二元制寬带非相干移頻鍵控系統的一个五比特的字进行比較,結果表明,在誤差槪率相同的情况下,32元制系統要求的信噪比比二元制系統要求的信噪比小6分貝左右。
This paper discusses binary and multivariate incoherent shift keying systems with much larger RF filter bandwidth than the information bandwidth. It is assumed that the RF filter bandwidth is at least ten times the baseband matched filter bandwidth. The expression of information symbol error rate of linear envelope detector and square-law envelope detector as a function of signal-to-noise ratio of channel input (before detection) is obtained. The first part of this article discusses a wideband binary system frequency shift keying system. Proved low signal to noise ratio (less than 0 dB), the square law detector best, high signal noise at this time the best linear detector. The preliminary experimental data are consistent with the theoretical analysis. The difference between the two is within 1/2 decibel when the error rate is 10 ~ (-4). The second part of this article discusses the multivariate wideband frequency shift keying system. The analysis results show that the same trend as above is also observed for a multivariate FSK system using a RF matched filter. It is proved that the required signal-to-noise ratio of channel decreases with the increase of each combined amount of information under the same typo rate. For example, comparing a five-bit word of a 32-band wideband incoherent shift keying system with a five-bit word of a two-element wideband incoherent shift keying system shows that the error In the same case, the signal to noise ratio required by a 32-element system is about 6 dB less than the signal-to-noise ratio required by a binary system.