Multi-Phase RF Frequency Conversion for Wide Tuning Ratios
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Solution Overview
Problem
Current frequency conversion systems in RF receivers and transmitters face challenges in achieving a large tuning range without increasing the nominal oscillator frequency, which can lead to increased power consumption or feasibility issues, and existing fractional dividers introduce noise and jitter due to non-50% duty-cycle outputs.
Innovation Solution
A radiofrequency receiver and transmitter system that employs a multi-phase local oscillator signal generator and a summing module with weighted resistor networks or analogue-to-digital converters to provide a second plurality of output signals, allowing for a wider range of oscillator frequency ratios, including 1.5, 2.5, and 3.5, and enabling reconfigurable mixers to generate balanced quadrature signals with fewer or more phases than the input, thereby reducing the required oscillator tuning range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the oscillator tuning range is increased to cover a large RF frequency range, then the frequency conversion system can operate over a wider bandwidth, but the power consumption increases and the nominal oscillator frequency increases
Solution Approach 1:
The patent divides the frequency conversion function into multiple parallel mixer channels (first mixer, second mixer, third mixer, fourth mixer), each handling a specific portion of the frequency range. This segmentation allows each oscillator to operate at a lower, fixed frequency while collectively covering a wide RF bandwidth, thereby reducing power consumption compared to a single wide-tuning oscillator.
Solution Approach 2:
The patent employs multiple oscillators operating at the same nominal frequency but with different phase relationships (e.g., quadrature oscillators producing 0°, 90°, 180°, 270° phases). These multi-functional oscillators serve both frequency generation and phase diversity functions, enabling wide bandwidth coverage without increasing the nominal oscillator frequency or power consumption.
2Adaptability or versatility
If multiple independent tuners are implemented on a single die to cover a large RF frequency range, then the tuning range is extended, but oscillator pulling problems and spurs occur
Solution Approach 1:
The patent assigns each mixer channel its own dedicated oscillator with a fixed nominal frequency, creating local frequency stability. By ensuring each oscillator operates independently at its optimal fixed frequency rather than sharing a common tuning mechanism, the system eliminates oscillator pulling effects and reduces spurious signals while maintaining wide overall bandwidth coverage through phase diversity.
3Adaptability or versatility
If fractional dividers are used to achieve non-integer frequency ratios, then the oscillator tuning range is reduced, but noise and jitter increase due to non-50% duty-cycle outputs
Solution Approach 1:
The patent employs reconfigurable mixer channels that can dynamically adjust their phase relationships and operational modes. By using switches and phase shifters to reconfigure the mixer connections, the system achieves variable frequency ratios (including non-integer ratios like 1.5, 2.5, 3.5) while maintaining clean 50% duty-cycle square wave outputs from the oscillators, thereby avoiding the noise and jitter problems associated with fractional dividers.
Data Source
AI summary
The invention relates to frequency conversion systems, in particular for use as up-converters or down-converters in radiofrequency (RF) receivers or transmitters, exemplary embodiments including a radiofrequency receiver including an RF signal input; a mixing module including a first plurality of IF amplifiers each connected to the RF signal input via a switch; a multi-phase local oscillator signal generator configured to provide a switching signal to each switch; and a summing module configured to receive output signals from each of the IF amplifiers and to provide a second plurality of output IF signals from a weighted sum of the IF amplifier output signals, wherein the second plurality is different to the first plurality.