Low Spurious Signal Homodyne Digital Receiver

Digital superheterodyne receivers employing two or more frequency conversion stages have been successfully employed in radars and communication equipment for many years. More recently, less complex single frequency conversion receivers, termed "homodyne receivers," have been revived and employed in lower performance equipment. The most significant problem limiting the performance in single frequency conversion directly to baseband is that of spurious signals due to the non-linear effects in the components. This paper describes a simple means in which second-order spurious signals that are generated from out-of-band signals can be cancelled while maintaining the signal of interest. Given that these fairly low, yet significant, spurious signals are cancelled and the in-band signal of interest is not to large, this new homodyne receiver does not have the issues with images that are present in superheterodyne receivers and furthermore, it may be smaller, less expensive, less complex, and should draw less power than the superheterodyne receivers. This receiver concept, if proven to be successful, might be employed in digital array radars (DAR). In this DAR application, ones own echo signals would only be of modest power levels but the out-of-band interfering signals that can be present could be of very large power levels. Furthermore, there may be similar applications in communications.