Patent ID: 7164901

Claim:
A DC offset-free direct conversion receiver RF front end, comprising: an I/Q splitting network receiving a radio-frequency signal X(t) and producing a first output signal Y_I(t) and a second output signal Y_Q(t), where said Y_Q(t) signal is 90 degrees out of phase from said Y_I(t) signal; a polyphase filter receiving a local oscillator signal X_LO(t), said polyphase filter having outputs producing output signals with 0 degree, 90 degree, and 180 degree phase differences relative to said local oscillator signal; mixers receiving said output signals of said I/Q splitting network and said output signals of said polyphase filter, said mixers having outputs producing intermediate-frequency signals with I and Q components; and combiner and buffer means having inputs and outputs, each of said inputs coupled to the output of one of said mixers, where at one output of said combiner and buffer means the I component intermediate-frequency signals are added, and the I component intermediate-frequency signal DC terms are subtracted, and where at another output of said combiner and buffer means the Q component intermediate-frequency signals are added and the Q component intermediate-frequency signal DC terms are subtracted.