Motorola Corporation

Freescale Semiconductor,inc.

David P Kovac

Vikram B Karnani

Lawrence Edwin Connell

Dan William Nobbe

Dale Gerard Schwent

Poojan Wagh

William T Waldie

Tao Wu

Transmission of a high frequency signal is provided by a passive mixer. The passive mixer receives a low frequency signal as an input. The passive mixer includes a plurality of transistors each with a gate, a source, and a drain. The passive mixer also includes a local oscillator connected to the gates of the transistors. The gates of the transistors are also connected to a DC bias proportional to the threshold voltage of the transistors. In addition, an output of the passive mixer may be attenuated by a passive attenuator wherein both the passive attenuator and passive mixer are substantially free of quiescent current.

Higher linearity passive mixer

A low noise direct conversion transmitter architecture without a post-PA filter is described. A high power/low noise differential LO ( ), controlled by a near unity divide ratio PLL ( ) for re-modulation protection, is coupled a polyphase quadrature generator ( ) generating amplitude-balanced and phase-shifted limited differential LO signals. The quadrature mixers ( and ) receive the limited differential LO signals and the filtered differential baseband signals to produce up-converted differential signals. The combiner ( ) receives the up-converted differential signals and combines them to produce a differential RF transmission signal. A VCA ( ) amplifies the differential RF transmission signal, and the resulting differential signal is converted to a single-ended RF transmission signal through a balun ( ). A linear amplifier ( ) is coupled to the single-ended RF transmission signal for amplification before radio transmission by an antenna ( ).

Low noise architecture for a direct conversion transmitter

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Vernon Hills, IL, United States of America

David P Kovac