Abstract: 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.

Abstract: A near-unity divider apparatus in a direct conversion communication device includes a reference frequency, that is not on-channel, input to a multiply-by-two circuit that doubles the reference frequency. A divide-by-three circuit divides the doubled frequency by three to provide a first fractionally-divided frequency at a transmit or receive frequency. A delay generator inputs the first fractionally-divided frequency from the divide-by-three circuit and provides a second fractionally-divided frequency delayed a predetermined time period. A gate circuit combines the first and second fractionally-divided frequencies to provide a transmit or receive frequency with an adjustable duty cycle dependant upon the predetermined time period.

Abstract: A low noise direct conversion transmitter architecture without a post-PA filter is described. A high power/low noise differential LO (110), controlled by a near unity divide ratio PLL (112) for re-modulation protection, is coupled a polyphase quadrature generator (120) generating amplitude-balanced and phase-shifted limited differential LO signals. The quadrature mixers (130 and 132) receive the limited differential LO signals and the filtered differential baseband signals to produce up-converted differential signals. The combiner (168) receives the up-converted differential signals and combines them to produce a differential RF transmission signal. A VCA (174) amplifies the differential RF transmission signal, and the resulting differential signal is converted to a single-ended RF transmission signal through a balun (180). A linear amplifier (184) is coupled to the single-ended RF transmission signal for amplification before radio transmission by an antenna (188).