Passive RF Downconverter With Current Buffer Noise Isolation
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Solution Overview
Problem
Current radio frequency mixing apparatus in communication devices face challenges with high noise figures, size, weight, and power consumption, necessitating improved designs for cellular and GPS receivers.
Innovation Solution
The proposed solution involves a mixing apparatus with a mixing core, current buffer, and transimpedance amplifier (TIA) configuration that receives radio frequency signals, downconverts them to intermediate frequency, and buffers the signals for processing, utilizing a current buffer with increased output impedance to reduce noise contribution from the TIA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional mixing apparatus are used for downconverting RF signals, then the mixing function is achieved, but the noise figure is high
Solution Approach 1:
The mixing apparatus is divided into separate functional blocks: a mixing core for downconversion, a current buffer for impedance transformation, and a transimpedance amplifier for signal processing. This segmentation allows each block to be optimized independently, with the current buffer specifically designed to isolate the mixing core from noise introduced by the TIA.
Solution Approach 2:
A current buffer is introduced as an intermediary component between the mixing core and the transimpedance amplifier. This buffer presents a low input impedance to the mixing core and a high output impedance to the TIA, acting as an impedance transformer that prevents the TIA from loading the mixing core and introducing noise.
2Use of energy by moving object
If conventional mixing apparatus are used, then the mixing function is achieved, but the power consumption is high
Solution Approach 1:
The current buffer transforms the impedance parameters between stages, presenting a low input impedance to minimize loading effects and a high output impedance to drive the TIA efficiently. This parameter transformation optimizes power transfer and reduces overall power consumption.
3Weight of moving object
If conventional mixing apparatus are used, then the mixing function is achieved, but the size and weight are large
Solution Approach 1:
The mixing core, current buffer, and transimpedance amplifier are integrated into a single compact apparatus, combining multiple functions into one unified structure. This merging reduces the overall size and weight while maintaining the necessary functional complexity through efficient circuit design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces noise figures, decreases power consumption, and minimizes size and weight, enhancing the performance of radio frequency mixing in communication devices.
Implementation Method 1
mix the RF signal with the LO signal to obtain an intermediate frequency (IF) signal at IF frequency, the IF signal being the RF signal downconverted using the LO signal
Implementation Method 2
Each current buffer input presents no more than a first input impedance, and each current buffer output presents at least a first output impedance. The first output impedance is greater than the first input impedance.
Implementation Method 3
the current buffer output corresponding to said each phase of the IF signal is coupled to the TIA input corresponding to said each phase of the IF signal
Data Source
AI summary
A noise isolation passive mixing apparatus is designed to mitigate noise contribution from intermediate frequency (IF) filters and amplifiers in a radio frequency translation stage. Common-gate configuration devices are inserted between passive mixer output and input of a transimpedance amplifier. In this way, circulation of the input-referred noise of the transimpedance amplifier is decreased, because of the relatively high output impedance of the common-gate devices, and the noise figure of the mixing apparatus can be improved. Since the radio frequency signal still sees low impedance, a radio frequency transconductance (RF gm) stage can be removed from the mixing apparatus, reducing current consumption. A double-balanced mixing apparatus with this general architecture may be implemented in a 0.18 micrometer CMOS technology and used in a low-IF global positioning system operating at 1.575 GHz, in an access terminal of a cellular communication system, and in other systems.