Multi-Band LO Distribution Using Local Divide-by-Two Stages
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Solution Overview
Problem
Existing multi-band transceivers face challenges in reducing integrated circuit area and power consumption while maintaining compliance with IEEE802.11a and IEEE802.11g standards, as well as minimizing the impact of power amplifier output signals on Voltage Controlled Oscillators (VCOs) due to high frequency operation and parasitic effects.
Innovation Solution
A novel local oscillator (LO) generation and distribution architecture where a VCO outputs a differential signal at approximately 10 GHz, which is divided by two to generate quadrature signals for both IEEE802.11b/g and IEEE802.11a bands, with phase mismatch correction circuits to adjust relative phases and minimize interference from power amplifier harmonics, allowing for efficient routing and reduced power 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 is reduced, but the VCO is disturbed by injection back through power supply conductors, ground conductors, substrate, or inductive coupling
Solution Approach 1:
The VCO operates at a frequency that is an even integer multiple (2x or 4x) of the PA output signal frequency, changing the frequency parameter to avoid direct interference while maintaining a compact architecture. This frequency relationship allows the VCO to be placed close to the PA without suffering from injection locking or distortion.
2Object-affected harmful factors
If the VCO operates at high frequency (10 GHz range) to avoid PA interference, then the frequency separation is achieved, but the power consumption increases due to parasitics in routing and reliability/yield problems occur
Solution Approach 1:
The LO signal distribution is segmented into multiple paths: a first LO signal at 10 GHz is distributed to 5 GHz band transmitters/receivers, while a second LO signal at 2.5 GHz is generated locally or distributed separately to 2.5 GHz band transmitters/receivers. This segmentation allows high-frequency operation only where necessary while reducing overall power consumption and improving reliability.
Solution Approach 2:
The system uses multiple frequency dimensions simultaneously - operating at both 10 GHz and 2.5 GHz/5 GHz bands - allowing the VCO to run at high frequency for interference avoidance while derived lower frequency signals serve bands that don't require high-frequency routing.
3Reliability
If the VCO operates at 10 GHz to minimize PA harmonic impact, then signal quality is maintained, but the routing complexity and parasitic effects increase
Solution Approach 1:
The LO distribution network is segmented into high-frequency paths (10 GHz to 5 GHz band) and low-frequency paths (2.5 GHz band), with each path optimized for its frequency range. This reduces routing complexity by avoiding high-frequency signal distribution where it is not needed.
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 architecture achieves reduced integrated circuit area and current consumption compared to prior art, while maintaining signal quality and reliability, by operating the VCO at a high frequency that minimizes the impact of power amplifier harmonics and allows for efficient generation and distribution of local oscillator signals across the transceiver.
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 IEEE802.11a transmitter or receiver that transmits or receives in a second band.