RF Bandpass Delta-Sigma ADC Receiver Without Mixers or IQ Mismatch
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Solution Overview
Problem
Existing radio-frequency (RF) receivers based on bandpass analog-to-digital converters (ADCs) face challenges in achieving low noise and low power consumption while maintaining high image rejection ratios (IRR), as they are often noisy and power-hungry due to the use of local oscillators and mixers.
Innovation Solution
The implementation of delta-sigma ADCs that digitize RF signals directly in the RF domain, utilizing n-th order resonant bandpass filters and digital generation of in-phase (I) and quadrature (Q) signals, which eliminates the need for local oscillators and mixers, and includes a low noise amplifier directly connected to the ADC, along with sub-sampling and up-conversion techniques to enhance noise immunity and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If local oscillators and mixers are used in RF receivers, then frequency conversion and signal processing can be achieved, but noise and power consumption increase
Solution Approach 1:
The patent extracts and removes the local oscillator and mixer components from the RF receiver architecture. By directly digitizing the RF signal using a bandpass ADC, the system eliminates the need for frequency conversion stages, thereby removing the sources of additional noise and power consumption associated with local oscillators and mixers while preserving signal processing capability through digital domain operations.
2Measurement precision
If local oscillators and mixers are used in RF receivers, then frequency conversion can be achieved, but noise and power consumption increase
Solution Approach 1:
The patent extracts and removes the local oscillator and mixer components from the RF receiver architecture. By directly digitizing the RF signal using a bandpass ADC, the system eliminates the need for frequency conversion stages, thereby removing the sources of additional noise and power consumption associated with local oscillators and mixers while preserving signal processing capability through digital domain operations.
3Measurement precision
If traditional RF receiver architecture with local oscillators is used, then signal processing is achieved, but device size and power consumption increase
Solution Approach 1:
The patent extracts and removes the local oscillator and mixer components from the RF receiver architecture. By directly digitizing the RF signal using a bandpass ADC, the system eliminates the need for frequency conversion stages, thereby removing the sources of additional noise and power consumption associated with local oscillators and mixers while preserving signal processing capability through digital domain operations.
Solution Approach 2:
The patent merges the RF signal amplification and digitization functions into a single integrated stage by directly connecting the low noise amplifier to the bandpass ADC. This consolidation eliminates intermediate frequency conversion stages and their associated components, reducing device complexity and size while maintaining signal processing capability through the unified analog-to-digital conversion path.
4Device complexity
If bandpass ADC is used to digitize RF signal directly, then local oscillators and mixers are eliminated, but filtering requirements become more stringent
Solution Approach 1:
The patent segments the filtering function into multiple stages: an analog bandpass filter that performs preliminary frequency selection before the ADC, and digital signal processing that performs additional filtering and image rejection after digitization. This segmentation allows the analog filter to operate with relaxed requirements compared to a single-stage solution, while the digital stage handles remaining filtering needs with precise control over the sampled RF signal.
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 approach results in compact, low-power, and low-noise RF receivers with image rejection ratios exceeding 95dB and reduced power consumption by eliminating IQ mismatch and relaxing sampling frequency, thereby achieving improved signal-to-noise ratios and smaller form factors.
Implementation Method 1
Amplifying the RF signal may comprise amplifying the RF signal with a low noise amplifier directly connected to the ADC
Implementation Method 2
utilizing n-th order resonant bandpass filters
Implementation Method 3
filtering the RF signal with an n th order resonant bandpass filter
Implementation Method 4
digitizing, with a delta-sigma analog-to-digital converter (ADC), the RF signal in an RF domain
Implementation Method 5
sampling the RF signal in an i th cycle of the sampling signal
Implementation Method 6
Up-converting the frequency of the output of the quantizer may comprise up-converting the frequency from 2-4GHz to 6-12GHz
Data Source
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AI summary
Radio-frequency, RF, receivers having bandpass sigma-delta analog-to-digital converters, ADC, designed to digitize signals in the RF domain are described. Such bandpass ADCs utilize one or more of the following techniques to enhance noise immunity and reduce power consumption: generation of in-phase (I) and quadrature (Q) paths in the digital domain, nth order resonant bandpass filtering with n>1, and signal subsampling in an ith Nyquist zone with i>1. Compared to RF receivers in which the I and Q paths are generated in the analog domain, these RF receivers exhibit higher IRRs because they are not susceptible to in-phase/quadrature (IQ) mismatch. Using nth order resonant bandpass filtering with n>1 attenuates unwanted image tones. The bandpass ADC-based RF receivers described herein exhibit enhanced immunity to noise, achieving for example image rejection ratios (IRR) in excess of 95dB.