Patent ID: 6993310
Filing Date: 2006-01-31
Classification: H03D,H03H

Abstract:
1. An image frequency rejection circuit, comprising: a first polyphase filter operable to generate a first LO signal and a second LO signal that is substantially ninety degrees out of phase with the first LO signal; a first mixer operable to receive an RF signal and the first LO signal, the first mixer further operable to communicate a first IF current signal, a second IF current signal that is substantially one-hundred-eighty degrees out of phase with the first IF current signal, and at least a portion of an image frequency signal; a second mixer operable to receive the RF signal and the second LO signal, the second mixer further operable to communicate a third IF current signal that is substantially ninety degrees out of phase with the first IF current signal, a fourth IF current signal that is substantially two-hundred-seventy degrees out of phase with the first IF current signal, and at least a portion of the image frequency signal; and a second polyphase filter communicatively coupled to the first mixer and the second mixer, wherein a phase shift associated with the first polyphase filter and a phase shift associated with the second polyphase filter combine to cancel the image frequency signal such that the second polyphase filter communicates a first IF output current signal, a second IF output current signal that is substantially one-hundred-eighty degrees out of phase with the first IF output current signal, a third IF output current signal that is substantially in phase with the first IF output current signal, and a fourth IF output current signal that is substantially one-hundred-eighty degrees out of phase with the first IF output current signal.