Multi-Stage LNA Tuning Using Multi-Tone FFT Calibration
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Solution Overview
Problem
Calibrating on-chip band-pass filters (BPFs) or Low-Noise Amplifiers (LNAs) with BPF capability in modern reconfigurable transceivers is time-consuming and power-intensive, especially when achieving a desired frequency response, which is a challenge in reducing calibration time in certain applications.
Innovation Solution
A method using a multi-tone signal to tune multi-stage low-noise amplifiers, where a wideband test signal with multiple tones is used in conjunction with an FFT module to calibrate the frequency response of cascaded band-pass filters, allowing for simultaneous adjustment of quality factor and resonant frequency to achieve a desired frequency response efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional single-tone calibration methods are used for on-chip BPFs and LNAs, then calibration accuracy can be achieved, but calibration time and power consumption increase significantly
Solution Approach 1:
The patent combines multiple calibration tones into a single multi-tone test signal that is applied simultaneously to the BPF/LNA under test. This merging of multiple calibration operations into one unified signal reduces the total calibration time while maintaining measurement accuracy through FFT-based frequency response analysis.
Solution Approach 2:
The patent enables continuous calibration across multiple frequency points by using a multi-tone signal that excites all calibration frequencies simultaneously. The FFT processor continuously analyzes the frequency response at all tone frequencies, eliminating the need for sequential single-tone measurements and maintaining continuous useful calibration action.
2Measurement precision
If traditional single-tone calibration methods are used for on-chip BPFs and LNAs, then calibration accuracy can be achieved, but power consumption increases
Solution Approach 1:
The patent merges multiple calibration measurements into a single multi-tone excitation event, reducing the total number of calibration cycles required. This consolidation decreases the cumulative power consumption while achieving the same frequency response characterization accuracy that would require multiple sequential single-tone measurements.
Solution Approach 2:
The continuous multi-tone calibration approach maintains steady-state operation at all calibration frequencies simultaneously, avoiding the repeated ramp-up and stabilization cycles required by sequential single-tone methods. This continuous operation reduces overall power consumption while maintaining measurement precision.
3Adaptability or versatility
If multi-stage LNAs with BPF capability are used, then filter selectivity and amplification are improved, but calibration complexity increases
Solution Approach 1:
The patent develops a universal multi-tone calibration methodology that can be applied to any multi-stage LNA with BPF capability, regardless of the specific number of stages or frequency specifications. This universal approach simplifies calibration complexity by providing a standardized procedure that works across different device configurations while maintaining the adaptability and versatility of the multi-stage architecture.
Solution Approach 2:
The patent implements feedback-based calibration where the FFT processor measures the actual frequency response at multiple tone frequencies, and this measurement feedback is used to adjust and optimize the performance of each BPF stage. This systematic feedback approach manages calibration complexity by providing clear guidance for tuning multiple stages simultaneously.
Data Source
AI summary
An example process includes reducing a quality factor of a first tunable bandpass filter, used, for example, in a low-noise amplifier stage of a polar receiver. A first wideband test signal centered at a desired center frequency of a second tunable bandpass filter is received. A frequency response of the second tunable bandpass filter to the first wideband test signal is estimated using a Fast Fourier Transform (FFT) signal processor. At least a resonant frequency or a quality factor of the second tunable bandpass filter are calibrated based at least in part on a portion of the estimated frequency response of the second tunable bandpass filter obtained from the FFT signal processor. Frequency response characteristics of the first tunable bandpass filter may be similarly tuned in accordance with the example process.