| 摘要 |
A repeating polyphase sequence - i.e. a sequence of complex numbers representing (preferably) points in the phase plane at equally spaced phase angles - is generated (11) and frequency shifted by multiplying (4, 6) by phase and quadrature components of a modulating signal to produce (7) a sum representing the real part of the complex product of the original and modulating signals. The arrangement can be used to produce a test signal having uniform spectral lines at desired frequency spacing which is useful for echo canceller training, line testing for modem start-up and the like. |
