Browse Prior Art Database

Method for a low flicker noise mixer

IP.com Disclosure Number: IPCOM000124274D
Publication Date: 2005-Apr-14
Document File: 8 page(s) / 139K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a low flicker noise mixer. Benefits include improved functionality and improved power performance.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 45% of the total text.

Method for a low flicker noise mixer

Disclosed is a method for a low flicker noise mixer. Benefits include improved functionality and improved power performance.

Background

              A mixer is required for complementary metal oxide semiconductor (CMOS) technology that has low flicker noise output. CMOS transistors conventionally have relatively large flicker noise. Some of that noise moves to baseband in conventional Gilbert/Jones mixers. For very large intermediate frequency (VLIF) and direct conversion receivers, mixer flicker noise typically degrades the noise figure (NF).

              Conventionally, flicker noise is reduced using two mixer circuit topologies. However, the reduction occurs at the expense of increased complexity, die area, and power consumption. Bipolar transistors are used in more expensive bipolar CMOS or silicon geranium technology because bipolar transistors have lower flicker noise than CMOS. However, this solution increases cost and has a lower level of integration.

General description

              The disclosed method is a passive, low flicker noise mixer. It is suitable for a variety of high-sensitivity narrow-band receivers for radios and cell phones. The method may also improve the NF of wireless local area network (WLAN) receivers.

Advantages

The disclosed method provides advantages, including:

•             Improved functionality due to providing a low flicker noise passive mixer

•             Improved functionality due to enabling integrated receivers and transceivers for WLAN and cell phone handsets

•             Improved power performance due to using mixing transistors without DC power

•             Improved power performance due to eliminating the requirement for additional gain and/or amplifiers

Detailed description

              The disclosed method is a passive mixer that provides gain and linearity similar to a conventional Gilbert/Jones mixer. When the transistor is on, the drain-source voltage Vds ~ 0V. When operating in the triode region, the drain bias current Id(dc) ~ 0. As a result, the region of operation greatly reduces flicker noise in metal oxide semiconductor field effect transistors (MOSFETs) by supplying a current to the mixer. Additionally, the method eliminates the requirement for additional gain and/or amplifiers, which consume additional power and/or degrade linearity (see Figure 1).

              The disclosed method can be implemented in a single-balanced mixer. It is comprised of the following components (see Figure 2):

•             Input transconductor

•             Transistors M1-M2
•             Bias current I1

•             Load resistors R1-R2

•             Passive mixing transistors M5-M6

•             Direct current (DC) blocking capacitors C1-C2

              Two current sources, I1 and I2, provide the DC current for M1-M2 and M3-M4 to keep them saturated. In practice, a DC negative feedback loop is included to set the voltage at the drains of M3 and M4 (omitted for simplicity).

              The...