Low phase noise frequency converter

摘要

One aspect of the present invention is a frequency conversion circuit having a pair of local oscillators. The local oscillators are frequency synthesizers based on an external frequency reference. The frequency conversion circuit is configured to perform a frequency conversion to an input signal equal to a frequency difference of signals from the pair of local oscillators; to generate an oscillator frequency difference signal; to generate an error signal using the oscillator frequency difference signal and an internal reference signal derived from the external frequency reference; and to adjust a phase of one of the pair of oscillators using the error signal. The above-described frequency conversion circuit embodiment essentially eliminates divider phase noise such as that generated by traditional prescalers. In addition, the use of two local oscillators provides a frequency conversion circuit capable of wide-range frequency conversion and high resolution. This frequency conversion circuit embodiment is suitable for receivers as well as transmitters, and is particularly suitable for digital television systems.