| 摘要 |
<p>A radio frequency (rf) receiver adapted to receive a number of different digitally modulated rf input signals such as quadrature amplitude modulated (QAM) and vestigial side band (VSB) rf input signals includes circuitry (11-18) for down converting the rf input signals to an intermediate frequency (IF) range having a centre frequency fc2 and a bandwidth of Bhz and converter circuitry (50) for sampling the IF signals and then producing corresponding baseband signals. In a preferred embodiment, the intermediate frequency signals are applied to a sample and hold circuit (51) which is sampled at a frequency fs and whose output is coupled via a low pass filter (53) to an analog-to-digital converter (52) whose output is then applied to a Hilbert filter (328) for demodulating the sampled signals and producing baseband signals. In-phase (I) and quadrature (Q) signals are produced whose phase and amplitude are not a function of different components and their tolerance of different conduction paths. <IMAGE></p> |
