Multi-Band LO Distribution With Quadrature Division and Phase Correction
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Solution Overview
Problem
Existing multi-band transceivers face challenges in reducing integrated circuit area and power consumption while maintaining reliable operation, particularly due to interference between Power Amplifiers (PAs) and Voltage Controlled Oscillators (VCOs) in generating and distributing local oscillator signals for IEEE802.11a and IEEE802.11b/g bands.
Innovation Solution
A novel LO generation and distribution architecture where a VCO outputs a differential signal at approximately 10 GHz, divided by two to generate quadrature signals for both 2.5 GHz and 5 GHz bands, with phase mismatch correction circuits to ensure accurate phase alignment, reducing the impact of PA output signals on the VCO and minimizing circuit area and current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the VCO operates at the same frequency as the PA output signal, then the circuit area and power consumption are reduced, but the VCO is disturbed by injection from the PA output signal through power supply conductors, ground conductors, substrate, or inductive coupling
Solution Approach 1:
The patent segments the LO generation into two separate VCOs operating at different frequencies (5 GHz and 2.5 GHz), allowing each VCO to operate independently without mutual interference while maintaining integration on the same chip. This segmentation resolves the contradiction by enabling frequency separation to prevent injection disturbance while keeping the overall circuit area minimized through integrated design.
2Device complexity
If the VCO operates at 10 GHz and signals are routed to generate 5 GHz and 2.5 GHz quadrature signals, then the frequency multiplication approach is simplified, but the power consumption increases due to parasitics in the routing and reliability/yield problems occur due to high frequency operation in the LO distribution network
Solution Approach 1:
The patent dynamically selects the operating frequency of each VCO based on the required output band (2.5 GHz or 5 GHz). Each VCO can be tuned to operate at its fundamental frequency or at double that frequency, allowing the system to adapt its LO generation approach dynamically. This resolves the contradiction by enabling the system to choose the most efficient operating mode rather than being locked into a fixed high-frequency architecture that consumes excessive power.
3Reliability
If separate VCOs are used for 2.5 GHz and 5 GHz bands, then the VCO disturbance from PA injection is eliminated, but the integrated circuit area increases
Solution Approach 1:
The patent implements universal VCO structures that can serve multiple frequency bands. Each VCO is designed with multi-functionality to generate LO signals for both 2.5 GHz and 5 GHz bands through frequency doubling techniques and quadrature signal generation. This resolves the contradiction by allowing separate VCOs to be implemented with shared functional blocks and interconnections, minimizing the total area increase while maintaining the reliability benefits of frequency separation.
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 allows for efficient generation and distribution of local oscillator signals with reduced power consumption and increased reliability, achieving smaller integrated circuit area and lower current consumption compared to prior art architectures.
Implementation Method 1
a Voltage Controlled Oscillator (VCO) of a Phase-Locked Loop (PLL) outputs a first differential signal of a tunable frequency
Implementation Method 2
A first divide-by-two circuit local to the VCO divides this first differential signal of frequency FVCO by two and outputs a first quadrature signal of frequency FVCO/2
Data Source
AI summary
A VCO of a PLL outputs a first differential signal of frequency FVCO. A first divide-by-two circuit local to the VCO divides the first differential signal and outputs a first quadrature signal of frequency FVCO/2. Two of the component signals of the first quadrature signal are routed to a second divide-by-two circuit local to a first mixer of a first device. The second divide-by-two circuit outputs a second quadrature signal of frequency FVCO/4 to the first mixer. All four signals of the first quadrature signal of frequency FVCO/2 are routed through phase mismatch correction circuitry to a second mixer of a second device. In one example, FVCO is a tunable frequency of about ten gigahertz, the first device is an IEEE802.11b/g transmitter or receiver that transmits or receives in a first band, and the second device is an IEEE 802.11a transmitter or receiver that transmits or receives in a second band.