WLAN Frequency Synthesizer Using Non-Integer VCO Multiples
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Solution Overview
Problem
Frequency synthesizers in wireless communication systems generate undesirable spurious frequencies, leading to interference with other wireless communication systems and violating regulatory limits, especially when VCOs operate at integer multiples of carrier frequencies, causing pulling effects and spurious signals.
Innovation Solution
A frequency synthesizer design utilizing two VCOs operating at non-integer multiples of the carrier frequencies, with a common regulatory path, and employing divide by 3 blocks and quadrature dividers to generate in-phase and quadrature local oscillator signals, minimizing spurious emissions by reducing VCO pulling effects and phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If VCO operates at integer multiples of carrier frequency, then frequency synthesis is simplified, but spurious signals and pulling effects increase
Solution Approach 1:
The patent changes the operating frequency parameter of the VCO from integer multiples to non-integer multiples (specifically 3/2 or 5/3 times the carrier frequency) of the carrier frequency. This parameter change eliminates spurious signals and pulling effects while still enabling frequency synthesis functionality.
2Device complexity
If VCO operates at integer multiples of carrier frequency, then frequency synthesis is simplified, but interference with other wireless systems increases
Solution Approach 1:
The patent changes the VCO operating frequency from integer multiples to non-integer multiples (3/2 or 5/3 times carrier frequency) of the carrier frequency. This parameter modification prevents the generation of spurious signals that would interfere with other wireless communication systems operating in adjacent bands.
3Adaptability or versatility
If VCO operates at higher frequency to cover multiple bands, then frequency coverage is improved, but phase noise increases
Solution Approach 1:
The patent optimizes the VCO operating frequency parameter to specific non-integer multiples (3/2 or 5/3 times carrier frequency) rather than simply using higher frequencies. This optimized parameter selection achieves multi-band coverage while minimizing phase noise and spurious signal generation.
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
The design effectively minimizes spurious emissions, ensuring compliance with regulatory standards and reducing interference with other wireless systems, while also providing power savings and area efficiency through tailored VCO characteristics.
Implementation Method 1
a first voltage controlled oscillator (VCO) generating a signal having a first frequency, a second VCO generating a signal having a second frequency
Implementation Method 2
the output from the first divide block is fed to the first mixer and combined with the signal from the first VCO to generate a first synthesized signal
Data Source
AI summary
A frequency synthesizer for a WLAN transceiver is disclosed that may be used to generate 5.4 GHz and 2.4 GHz signals. The frequency synthesizer may be configured to minimize VCO pulling by using VCO operating frequencies that are not integer multiples of the RF bands. Further, the frequency synthesizer may be configured to minimize interference with other frequency bands used by existing wireless systems.