Switched-Capacitor Radio Receiver for Low-Voltage Dynamic Range
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Solution Overview
Problem
Conventional radio receiver architectures face challenges in small feature size integrated circuit fabrication technologies, such as limited dynamic range, high flicker noise, and difficulty in cascoding transistors, due to low supply voltage and intrinsic voltage gain limitations.
Innovation Solution
The proposed radio receiver architecture incorporates a passive matching network, low-noise buffer, and switched-capacitor charge pumps to enhance signal processing, reducing noise figure and improving dynamic range by increasing voltage gain and using differential and quadrature-phase components, along with chopper stabilization for noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional radio receiver architectures are used in small feature size integrated circuit fabrication technologies, then device complexity is reduced, but dynamic range is limited due to low supply voltage and low intrinsic voltage gain from transistors
Solution Approach 1:
The receiver architecture is segmented into multiple functional blocks: antenna interface circuit, first mixer, first charge pump, buffer, second charge pump, and output stage. Each block performs a specific function and can be independently optimized. The segmentation allows the use of passive mixing in the first mixer while using active charge pumps for signal regeneration and amplification, thereby maintaining low complexity while improving dynamic range through staged signal processing
Solution Approach 2:
Charge pumps are introduced as intermediary devices between the passive mixer and the output stage. The first charge pump regenerates the downconverted signal from the first mixer, and the second charge pump further processes the signal before the output stage. These intermediaries enable signal amplification and regeneration without requiring high-voltage transistors, thus improving dynamic range while maintaining compatibility with low-voltage small feature size technologies
2Manufacturing precision
If conventional transistors are used in small feature size technologies, then manufacturing precision is improved, but flicker noise increases due to high flicker noise corner
Solution Approach 1:
The harmful flicker noise generated by conventional transistors is extracted and removed through the use of passive mixing. The passive mixer converts the RF signal to baseband without using noisy active transistors at the RF stage. Additionally, the charge pumps operate at lower frequencies where flicker noise is less problematic, effectively extracting the noise generation from the critical signal path
Solution Approach 2:
The charge pumps employ periodic switching action to regenerate and amplify the signal. By operating the charge pumps at specific switching frequencies and using correlated double sampling techniques, periodic noise components including flicker noise can be pushed to frequencies outside the signal bandwidth or cancelled through differential processing
3Device complexity
If cascoding transistors is attempted in small feature size technologies, then voltage gain is improved, but ease of operation deteriorates due to headroom issues
Solution Approach 1:
The mechanical transistor-based amplification system is replaced with a hybrid system combining passive mixing and charge pump-based signal regeneration. Instead of relying on cascoded transistors for voltage gain, the system uses passive mixers for frequency conversion and charge pumps for signal amplification, eliminating the need for complex transistor biasing and headroom management while achieving the desired voltage gain
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3C
AI summary
A baseband signal-conditioning architecture applicable to radio receivers uses switched-capacitor techniques to provide high-performance signal conditioning in low-voltage, deep-submicron processes (e.g., 65nm and below). In the architecture, a first mixer is coupled to an antenna receiving the signal, and outputs a first mixer output signal based on the signal received by the antenna. A buffer coupled to an output of the first mixer outputs a buffer signal based on the first mixer output signal. A first charge pump is coupled to an output of the buffer, and produces a first charge pump output signal based on the buffer signal. In some examples, a second charge pump is coupled to the output of the first mixer and produces a second charge pump output signal based on the first mixer output signal, and the buffer input is coupled to an output of the second charge pump.