Dual RF Receiver Noise Reduction via Local Oscillator Frequency Separation
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Solution Overview
Problem
Dual RF receiver circuits face noise and instability issues due to local oscillators being tuned to similar frequencies, which de-sensitize the receivers and reduce their effectiveness in wireless communication systems.
Innovation Solution
The implementation of a dual RF receiver circuit with separate local oscillators for each RF mixer, where the frequency of one local oscillator is either less than or greater than the frequency of its respective RF channel, to maximize frequency separation and reduce noise and instability, or to separate frequencies from interfering or spurious signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If two separate local oscillators are used in a dual RF receiver circuit, then data reception capability is improved, but noise and instability increase due to circuit parasitics
Solution Approach 1:
The patent divides the local oscillator functionality into two separate oscillators (LO1 and LO2) operating at different frequencies, allowing each to be independently tuned. This segmentation enables simultaneous operation without mutual interference while maintaining the dual receiver capability, thus improving productivity without excessive noise generation.
Solution Approach 2:
The patent changes the frequency parameter of the local oscillators by introducing an offset frequency (FO1 and FO2) that separates the operating frequencies of LO1 and LO2. This parameter change ensures that the oscillators operate at sufficiently different frequencies to avoid parasitic interference while still enabling dual channel reception, thereby reducing noise and instability.
2Device complexity
If local oscillators are tuned to the same or nearly the same frequency, then device complexity is reduced, but sensitivity decreases due to noise and instability
Solution Approach 1:
The patent modifies the frequency parameter by introducing offset frequencies (FO1 and FO2) that separate the local oscillator frequencies. This allows the system to maintain relatively simple dual-oscillator hardware while achieving sufficient frequency separation to prevent parasitic interactions, thus preserving sensitivity without significantly increasing complexity.
Solution Approach 2:
The patent introduces frequency offset as an intermediary parameter that mediates between the simplicity of using identical frequencies and the sensitivity requirements of using separated frequencies. By applying a controlled offset, the system achieves a compromise that maintains both simplicity and performance.
3Ease of operation
If local oscillators are tuned to the same frequency, then ease of operation is improved, but harmful noise factors increase
Solution Approach 1:
The patent automatically adjusts the frequency parameter of the local oscillators by applying offset frequencies (FO1 and FO2) based on the received signal frequency. This parameter change is transparent to the operator, maintaining ease of operation while effectively separating the oscillator frequencies to minimize parasitic noise generation.
Data Source
AI summary
The present invention relates to a dual radio frequency (RF) receiver circuit that includes a first RF mixer and a second RF mixer. The first and second RF mixers may be fed from a common local oscillator or from two separate local oscillators. When fed from two separate local oscillators and when the first and second RF mixers are receiving the same or nearly the same RF channel, the frequency of the RF channel is less than the frequency of one local oscillator and is greater than the frequency of the other local oscillator. This arrangement separates the frequencies of the local oscillators, thereby reducing noise, instability, or both, which may otherwise de-sensitize the dual RF receiver circuit.