Radio Front-End Charge Generator Circuit for Out-of-Band Noise Reduction
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Solution Overview
Problem
Current radio transmitter architectures face challenges in achieving low out-of-band noise levels, particularly in Frequency Division Duplex mode, due to the generation of high-frequency noise components that are difficult to filter, and existing solutions either require bulky and expensive inductors or struggle with noise levels in modern cost-effective designs.
Innovation Solution
A digital-intensive front-end system for radio devices that converts digital baseband signals into electrical charges using a charge generator circuit, comprising a first converter circuit for calculating charge values and a second converter circuit for converting these values into electrical charges, which are then used to generate radio frequency signals, thereby avoiding the need for linear voltage amplifiers and introducing filtering to achieve the required noise specifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a low-pass filter is used in the current domain to filter out out-of-band baseband noise, then the out-of-band noise is reduced, but the filter requires bulky and expensive inductors
Solution Approach 1:
The patent replaces the traditional current-domain low-pass filter (which requires inductors) with a voltage-domain filtering approach. By converting the baseband current to voltage before filtering, the system eliminates the need for bulky inductors while achieving the same noise filtering function through simpler RC circuits in the voltage domain.
Solution Approach 2:
The patent changes the domain parameter from current to voltage. By performing the filtering operation in the voltage domain rather than the current domain, the system achieves equivalent noise attenuation without requiring inductive components, thus reducing device complexity and cost.
2Measurement precision
If buffer circuits are used to drive the baseband inputs of the mixer with large signal swing, then the signal-to-noise ratio is improved, but the linearity requirements become very stringent and power consumption increases
Solution Approach 1:
The patent replaces the complex buffer circuit approach with a direct voltage sampling method. Instead of using buffer circuits to drive the mixer inputs with large signal swings, the system directly samples the baseband voltage and feeds it to the mixer, eliminating the need for high-performance buffer circuits with stringent linearity requirements.
Solution Approach 2:
The patent inverts the traditional approach by sampling the voltage directly rather than switching the current. This inversion of the sampling method eliminates the need for complex buffer circuits and reduces the linearity requirements while maintaining adequate signal-to-noise ratio.
3Reliability
If high oversampling ratios are used in DDRM-based architectures to move aliases to far-away locations, then the filtering effect is improved, but the out-of-band noise level rises above required specifications
Solution Approach 1:
The patent applies preliminary filtering in the voltage domain before the upconversion process. By filtering out-of-band noise components before they are upconverted to RF frequencies, the system prevents these noise components from appearing in the final output, avoiding the out-of-band noise problem that occurs when filtering is applied after upconversion in DDRM architectures.
4Ease of manufacture
If a switched-capacitor power amplifier is used to generate RF waveform with reasonable accuracy, then the signal generation is simplified, but a large amount of output noise is generated in adjacent and far-out channels
Solution Approach 1:
The patent applies preliminary out-of-band filtering in the voltage domain before the power amplification stage. By removing noise components before they are amplified and radiated, the system prevents the generation of excessive output noise in adjacent and far-out channels while maintaining the simplicity of switched-capacitor power amplifier-based signal generation.
Data Source
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AI summary
The present disclosure relates to a front-end system for a radio device (100) comprising: a charge generator circuit (10) arranged for receiving a digital baseband signal (BB) and comprising a first converter circuit (11) arranged for calculating at least one charge value (q) based on said digital baseband signal (BB) and a second converter circuit (12) arranged for converting said at least one charge value (q) into at least one electrical charge (Q), and a modulator circuit (20) arranged for generating a radio frequency signal (RF) based on said at least one electrical charge (Q) and at least one local oscillator signal (LO).