Gilbert mixer with negative gm to increase nmos mixer conversion

Abstract

A cross coupled NMOS transistors providing a negative gm transistor feedback allows a mixer to saturate at a reduced input signal swing voltage when compared to a conventional mixer allowing the mixer to enter into the current mode operation at a reduced signal input voltage range. The linearity of the baseband signal path can be traded against the mixer gain and is improved if the signal swing in the baseband signal path is reduced. The input mixer transistors operate in the saturated mode at a reduced input signal swing voltage causing the power efficiency of the system to increase since the transmit chain operates at a class-D power efficient. Efficiency is very important in mobile applications to save and extend the battery power of a mobile phone providing a better utilization of the available power since most of that power is supplied to the energy of the outgoing modulated signal.

Description

[0001]The present application is related to the co-filed U.S. application Ser. No. ______ entitled “______” filed on Mar. 8, 2013, which is assigned to the same assignee as the present application and incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]The Federal Communications Commission (FCC) has allotted a spectrum of bandwidth in the 60 GHz frequency range (57 to 64 GHz). The Wireless Gigabit Alliance (WiGig) targets the standardization of this frequency band that will support data transmission rates up to 7 Gbps. Integrated circuits, formed in semiconductor die, offer high frequency operation in this millimeter wavelength range of frequencies. Some of these integrated circuits utilize Complementary Metal Oxide Semiconductor (CMOS), Silicon-Germanium (SiGe) or GaAs (Gallium Arsenide) technology to form the dice in these designs.[0003]CMOS (Complementary Metal Oxide Semiconductor) is the primary technology used to construct integrated circuits. N-ch...

AI Technical Summary

Benefits of technology

The invention describes a technique using cross-coupled negative gm feedback and cross coupled NMOS transistors to improve the performance of a Gilbert mixer. The technique allows the mixer to saturate at a lower input signal swing voltage and enter into current mode operation at a reduced signal input voltage range. By trading off linearity in the baseband signal path, the mixer can improve its efficiency. The technique also allows for higher efficiency in the transmit chain, which is important in mobile applications to save battery power and extend usage time. Additionally, a special feature of the cross-coupled NMOS transistors prevents saturation of the input chain of the baseband while still providing better linearity and power efficiency. The invention also describes a method of up-converting a differential in-phase and differential quadrature signal using cross coupled MOS transistors and a differential capacitance adjustment circuit to adjust the frequency of the up-converted signal. The method includes steps to reduce saturation voltage and improve power usage in the power amplifier stage.

Problems solved by technology

The reduced swing from the baseband, however, has only a limited swing of 300 mV and must be of sufficient magnitude to place the drive the gates of the driven transistors into saturation.

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