Time-Varying Phase Control for Frequency Translation

Frequency conversion is typically achieved by mixing a signal with a local oscillator. However, mixing typically generates an image frequency, in addition to other unwanted harmonics. Here, we achieve X-band frequency translation without image frequency suppression using a device capable of 360° phase modulation. The device is realized in microstrip technology, and varactor diodes are used for phase control in a serrodyne translator topology. The design could be used as a building block for the development of nonreciprocal devices such as isolators and circulators.