Phased Array LO Circuit for Accurate I/Q Beamforming
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Solution Overview
Problem
Existing phased array transceiver elements face challenges in generating accurate in-phase and quadrature signals, particularly at high frequencies, due to complex modulation schemes, leading to design complexity and difficulty in adjusting beamforming phase shifts.
Innovation Solution
The phased array transceiver element employs a local oscillator stage with a phase shifter and frequency multipliers to perform beamforming phase shifts and phase-splitting at lower frequencies, allowing independent adjustment of phase shifts, reducing design complexity and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase shifting is performed at the local oscillator frequency, then beamforming phase shift can be applied, but the phase shift adjustment becomes difficult and design complexity increases at high frequencies
Solution Approach 1:
The patent applies preliminary action by performing phase shifting at a lower reference frequency before frequency multiplication, rather than at the final high local oscillator frequency. The phase shifter operates on a reference signal at frequency f_ref, applying the desired beamforming phase shift φ. This phase-shifted reference signal is then multiplied by frequency factors L and M to generate the final local oscillator signals. This approach simplifies the phase shifting operation since it occurs at a lower frequency with smaller required phase adjustment range, reducing design complexity while maintaining accuracy.
2Reliability
If complex modulation schemes are used, then communication performance improves, but the requirement for accurate in-phase and quadrature signals increases design difficulty
Solution Approach 1:
The patent segments the local oscillator generation into independent in-phase and quadrature paths, each with its own frequency multiplier chain. The phase-splitting arrangement divides the phase-shifted reference signal into two paths: one path goes through frequency multiplication by L then M to generate the in-phase local oscillator signal, while the other path goes through frequency multiplication by L then M with an additional 90-degree phase shift to generate the quadrature local oscillator signal. This segmentation allows independent optimization and adjustment of each path, ensuring accurate 90-degree phase difference between I and Q signals even with complex modulation schemes.
Solution Approach 2:
The patent introduces a phase-splitting arrangement as an intermediary component between the reference frequency source and the frequency multipliers. This phase-splitting arrangement specifically generates the 90-degree phase difference between in-phase and quadrature signals by applying a second phase shift of +45 degrees to one path and a third phase shift of -45 degrees to the other path. This intermediary structure ensures precise quadrature relationship is maintained through the frequency multiplication process, enabling accurate modulation for complex communication schemes.
3Ease of operation
If frequency multiplication is performed after phase shifting, then the phase shift range required is reduced, but the phase shifts and frequency multiplications become coupled
Solution Approach 1:
The patent applies preliminary action by performing all phase shifting operations on the reference signal before frequency multiplication. The beamforming phase shift φ and the quadrature phase shifts (+45 and -45 degrees) are all applied to the reference signal at frequency f_ref before the frequency multiplication factors L and M are applied. This decouples the phase shift adjustment from the frequency multiplication process, allowing independent optimization of each function and simplifying the overall design.
Data Source
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AI summary
A phased array transceiver element (100) comprises a local oscillator stage (104) for generating beamformed in-phase and quadrature local oscillator signals, the local oscillator stage (104) comprising a phase shifter (120) connectable to a reference frequency source and applying a first phase shift; a primary frequency multiplier (122) input from said phase shifter and applying a primary frequency multiplication factor; a phase-splitting arrangement (124) input from said primary frequency multiplier (122) and having a first output (126) and a second output (128), said phase-splitting arrangement (124) applying a second phase shift at said first output (126) and a third phase shift at said second output (128); a first secondary frequency multiplier (130) input from said first output (126) of said phase-splitting arrangement (124), having an output (134) for the in-phase local oscillator signal, and applying a secondary frequency multiplication factor; and a second secondary frequency multiplier (132) input from said second output (128) of said phase-splitting arrangement (124), having an output (136) for the quadrature local oscillator signal, and applying said secondary frequency multiplication factor.