Active Mixer Bias Control for Broadband mm-Wave Linearity
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Solution Overview
Problem
Conventional active mixers face challenges in providing constant gain and linearity across a range of millimeter wave frequencies due to their dependence on the amplitude of the local oscillator (LO) signal, especially at mm-wave frequencies, where the direct current (DC) electrical current is strongly influenced by the LO amplitude, leading to inadequate performance.
Innovation Solution
The implementation of a biasing circuit and a combiner circuit electrically coupled to a voltage-biased mixer core circuit, where the biasing circuit generates a bias voltage with an inverse or direct relationship to the LO signal amplitude, resulting in a biased LO signal that is applied to switch circuits within the mixer core, thereby making the DC electrical current independent of the LO signal amplitude, ensuring constant gain and linearity across mm-wave frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional active mixer is used at mm-wave frequencies, then the mixer can operate at high frequencies, but the DC electrical current becomes strongly dependent on the LO signal amplitude, resulting in non-constant gain and poor linearity
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the bias voltage applied to the mixer core based on the detected LO signal amplitude. When the LO amplitude varies, the bias voltage is adjusted accordingly to maintain constant DC current, thereby preserving gain constancy and linearity across different operating conditions while enabling broadband mm-wave operation
Solution Approach 2:
The patent implements feedback by detecting the LO signal amplitude and using this information to control the bias voltage applied to the mixer core. The feedback mechanism ensures that when LO amplitude changes, the bias voltage is adjusted to compensate, maintaining stable DC current and consistent mixer performance across varying LO conditions
2Power
If the LO signal amplitude is increased to improve mixing performance, then the output signal strength may increase, but the DC electrical current increases proportionally, leading to non-constant gain and reduced linearity
Solution Approach 1:
The patent changes the bias voltage parameter in response to LO amplitude variations. When LO amplitude increases, the bias voltage is adjusted to maintain constant DC current, thereby preserving linearity while allowing the mixer to operate with varying LO power levels without degrading performance
Data Source
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AI summary
Methods, systems, and devices for wireless communication are described for enhanced broadband operation of an active mixer. In an example, an apparatus may include an active mixer that converts between radio frequency (RF) signals and intermediate frequency (IF) signals based at least in part on an alternating current (AC) local oscillator (LO) signal, wherein a direct current (DC) current generated within the active mixer is dependent in part on a bias voltage and the AC LO signal. The apparatus may include a mixer biasing circuit that generates the bias voltage for the active mixer, a magnitude of the bias voltage having an inverse relationship to an amplitude of the AC LO signal.