许多已有的CO(中心局)dsl调制解调器可以只支持相对较窄的接收频率范围，这会增加估计宽的多的远端环路噪声的难度。
Many existing CO DSL modems may only support a relatively narrow receive frequency range, which will increase the difficulty of estimating the much wider bandwidth far-end loop noise.
在射频电路方面，提出了频率合成器和调制解调器设计方案，并通过测试证明了该方案的可行性。
In the aspect of RF circuits, the scheme of frequency synthesizer and modem is proposed, and the feasibility of the scheme is verified by practical test.
中频部分主要由HFA3724正交调制解调器和基于MB1502的锁相频率合成电路等组成。
The intermediate frequency circuit includes QPSK modulation based on HFA3724, PLL circuit based on MB1502.
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