Patent ID: 6487398
Filing Date: 2002-11-26
Classification: H04B

Abstract:
An apparatus for converting a baseband information signal directly to a radio frequency (RF) transmission signal for a direct conversion transmitter of a radiotelephone, comprising:a local oscillator (LO) system producing a differential input LO signal having a frequency substantially equal to a desired RF transmission frequency, a polyphase system coupled to receive the differential input LO signal, generating a first and a second phase shifted differential LO signals wherein the first and the second phase shifted differential LO signals have a frequency substantially equal to the differential input LO signal frequency and having a phase offset of a value substantially equal to ninety degrees relative to each other; and a quadrature mixer system having first inputs wherein the inputs are coupled to receive the first and the second phase shifted differential LO signals, and having second inputs coupled to receive a first and a second modulated differential baseband information signals, a first mixer for mixing the first phase shifted differential LO signal with the first filtered differential baseband information signal, a second mixer for mixing the second phase shifted differential LO signal with the second filtered differential baseband information signal, and to combine resulting signals to produce the RF transmission signal.