A frequency synthesizer with at least two main Phase Locked Loops (PLLs) and a signal combiner, where each PLL's input is driven by a reference source of frequency F.sub.refj, and each PLL has programmable dividers in both its input path (M and P) and its feedback path (N and Q). The synthesizer utilizes a method to produce an output frequency F.sub. out that is a close approximation to a requested frequency F.sub.req. The method includes making a series of rational fraction approximations .sup. X i/Y.sub.i to the ratio .sup.F req/F.sub.refj, factoring the resulting Y. sub.i 's into several factors M.sub.i and P.sub.i, picking a pair X.sub. k, Y.sub.k that is a good approximation, but where neither M.sub.k nor P. sub.k is too large for the dividers, and then using diophantine calculation methods and a further equation relating to the way the PLL's signals are combined, to calculate N.sub.k and Q.sub.k. The integers M. sub.k, N.sub.k, P.sub.k, and Q.sub.k are then used to program the four dividers. Several forms of the invention further use a controlled reference source, and by varying F.sub.refj, allow more than one approximation to be made, and the error for each to be determined. After several such calculations, a low error one is chosen, and its M.sub.i, N. sub.i, P.sub.i and Q.sub.i values used. The invention works with synthesizers where the PLL's signals are combined to produce F.sub.out, and with synthesizers where the combined signal is used as a feedback signal for the PLL's.
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机译:一种具有至少两个主锁相环(PLL)和信号组合器的频率合成器,其中每个PLL的输入由频率为Fref的参考源驱动,并且每个PLL在其两个输入路径中均具有可编程分频器(M和P)及其反馈路径(N和Q)。合成器利用一种方法来产生输出频率F。输出与请求频率Freq非常接近。该方法包括进行一系列有理分数逼近。 X i / Yi与比率f req / Frefj的比值,将得到的Y sub分解为M i和P i的几个因子,对X.sub。 k,Yk是一个很好的近似值,但是Mk和P.k都不对分频器太大,然后使用双色元计算方法和与PLL的方式有关的其他方程式信号被组合,以计算Nk和Qk。然后使用整数Mk,Nk,Pk和Qk对四个分频器进行编程。本发明的几种形式还使用受控参考源,并且通过改变F refj,可以进行多个近似,并且可以确定每种近似的误差。经过几次这样的计算之后,选择低误差的一个,并使用其Mi,N.i,P.i和Q.i值。本发明与合成器(其中PLL的信号被组合以产生Fout)一起工作,并且与合成器一起使用,其中该组合的信号被用作PLL的反馈信号。
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