Current-Mode Blixer Noise Cancellation for Linearity and Gain
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Solution Overview
Problem
Conventional blixers are noisy and have limited signal swing headroom due to transistor stacking, which restricts achievable gain and linearity.
Innovation Solution
A transconductance circuit generating amplified signals is coupled with a mixing circuit that includes impedance networks and differential amplifiers, using passive mixers and adjustable impedance to improve noise cancellation and linearity, with a dummy path for RF filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transistor stacking is used in conventional blixer architecture, then the circuit integration is achieved, but the headroom for signal swing is severely limited
Solution Approach 1:
The patent divides the conventional stacked blixer architecture into separate functional blocks: a balun-LNA stage and an I/Q mixer stage, connected through coupling capacitors. This segmentation removes the direct transistor stacking, allowing each stage to operate with adequate voltage headroom while maintaining the integrated functionality of the blixer.
Solution Approach 2:
Coupling capacitors are introduced as intermediary elements between the balun-LNA stage and the I/Q mixer stage. These capacitors enable signal transfer between stages without requiring direct transistor stacking, thus preserving signal swing headroom while maintaining circuit functionality.
2Device complexity
If transistor stacking is used in conventional blixer, then the circuit is compact, but the achievable gain is limited
Solution Approach 1:
By segmenting the circuit into separate balun-LNA and I/Q mixer stages with coupling capacitors, the patent enables higher gain in each stage without the constraints of transistor stacking. The balun-LNA can provide initial amplification, and the I/Q mixer can provide additional gain, achieving overall higher gain while maintaining compactness.
3Device complexity
If transistor stacking is used in conventional blixer, then the circuit structure is simplified, but the linearity is limited
Solution Approach 1:
The patent separates the balun-LNA and I/Q mixer functions into distinct stages, allowing each stage to be optimized for linearity independently. This segmentation enables better control of nonlinear effects that occur in stacked transistor configurations, thereby improving overall linearity while maintaining structural simplicity.
4Device complexity
If conventional blixer architecture is used, then the circuit is straightforward, but the noise performance is poor
Solution Approach 1:
By dividing the circuit into separate balun-LNA and I/Q mixer stages with coupling capacitors, the patent enables better noise management. Each stage can be independently optimized for noise performance, and the coupling capacitors help isolate noise between stages, improving overall noise performance while keeping the circuit straightforward.
Data Source
AI summary
Blixers, which are a relatively recent development, have not be studied as extensively as many older circuit designs. Here, a blixer is provided that improves linearity and reduces noise over other conventional blixer designs. To accomplish this, the blixer provided here uses a differential amplifier and/or a dummy path within its mixing circuit to perform noise reduction (and improve linearity).