DLL Phase-Shifted LO Signals for Linear Transmitter Feedback
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Solution Overview
Problem
Existing Cartesian feedback transmitters face challenges in maintaining linearity across a broad range of frequencies due to the need for extensive filtering to mitigate harmonics from phase shifting circuitry, which increases complexity and power consumption.
Innovation Solution
A method and apparatus utilizing a delay locked loop (DLL) and programmable divider to generate phase shifted local oscillator signals, allowing for adjustable phase shifts within the feedback loop, thereby maintaining transmitter linearity without the need for extensive filtering across multiple frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency domain technique with complex frequency mixers and quadrature generators is used to generate phase shifted LO signal, then loop phase adjustment is achieved, but harmonics are created requiring extensive filtering
Solution Approach 1:
The patent extracts and eliminates the harmful harmonics generation mechanism by replacing the frequency domain phase shifting approach with a time domain delay-based approach. The DLL generates phase shifted LO signals through controlled time delays rather than frequency mixing, thereby taking out the source of harmonics that would require filtering.
Solution Approach 2:
The patent substitutes the mechanical/electronic frequency mixing system with a time delay system. Instead of using mixers and quadrature generators that create harmonics, the invention uses delay elements within the DLL to achieve phase shifting in the time domain, replacing the complex frequency domain mechanism with a simpler time domain approach.
2Reliability
If extensive filtering is applied to mitigate harmonics from phase shifting circuitry, then stable operation is achieved, but power consumption and device complexity increase
Solution Approach 1:
The patent converts the harmful effect of phase shifting circuitry into a benefit by using delay elements that inherently provide phase shifting without generating harmful harmonics. The time delay mechanism transforms the potential harm of frequency mixing into a beneficial harmonic-free phase shifting approach, eliminating the need for power-consuming filters.
3Adaptability or versatility
If the transmitter operates over a wide frequency range, then versatility is improved, but more filter components are required consuming space and current
Solution Approach 1:
The patent implements a universal phase shifting mechanism through the DLL that functions across multiple frequency bands without requiring band-specific filter components. The delay-based phase shifting approach is frequency-agnostic, allowing the same circuitry to serve multiple frequency ranges, thereby achieving multi-functionality without increasing circuit space.
Data Source
AI summary
A transmitter is provided with a local oscillator (LO) processing unit to maintain stability in the transmitter's feedback loop. The LO processing unit includes at least one delay locked loop (DLL) and a programmable divider to generate phase shifted LO signals for adjusting a loop phase of the feedback loop in the transmitter. The generated phase shifted LO signals are of both a coarse and fine phase shifted nature. The adjustability and control of the coarse and fine phase shifting of the LO signals maintains linearity in the transmitter feedback loop.