Interstage Transformer Harmonic Trapping for LO Spur Rejection
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Solution Overview
Problem
Existing wireless communication systems, particularly in 5G and beyond, face challenges with non-linearities and interference due to even-order harmonics generated by differential local oscillator signals, leading to spurs at the main channel, which affect signal quality and efficiency.
Innovation Solution
Implementing a harmonic trapping circuit, such as an L-C filter, between the matching circuitry transformer and the power amplifier's DC bias voltage source to filter out even-order harmonics, reducing their impact on the signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a harmonic trapping circuit (L-C filter) is added to filter out even-order harmonics, then noise rejection and signal quality are improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the harmful even-order harmonics from the signal path by inserting an L-C filter specifically targeted at these frequencies. The filter is placed between the power amplifier and the matching network to selectively eliminate the 2nd, 4th, and other even-order harmonics generated by the differential local oscillator, thereby improving noise rejection without affecting the main signal path
Solution Approach 2:
The L-C filter acts as an intermediary component between the power amplifier and the matching network. This mediator selectively attenuates even-order harmonics while allowing the fundamental frequency and odd-order harmonics to pass through, thus resolving the contradiction by providing noise rejection through a dedicated filtering stage that adds minimal complexity
2Productivity
If the power amplifier operates at high power levels for improved signal transmission, then transmission efficiency is improved, but non-linearities and harmonic generation increase
Solution Approach 1:
The patent converts the harmful effect of harmonic generation into a beneficial outcome by using the presence of even-order harmonics as an indicator to design a targeted filtering solution. The L-C filter is specifically tuned to reject these harmonics, and the system even utilizes the 2nd harmonic rejection to improve 1dB compression point and third-order intercept point, thereby transforming the harmonic problem into a performance enhancement opportunity
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
The harmonic trapping circuit provides significant noise rejection, exceeding 40 dB at the 4th order harmonic frequency, stabilizing the power amplifier and improving signal quality and efficiency in wireless communication systems.
Implementation Method 1
a filter arrangement coupled between the matching circuitry transformer and the power amplifier's DC bias voltage source. The filter arrangement is configured to filter out an even-order harmonic of the local oscillator (LO) signal
Data Source
AI summary
A method for harmonic trapping in a matching network of a power amplifier includes determining primary inductance and secondary inductance of a differential transformer of the matching network, based on a signal operating frequency of the power amplifier. An inductance value for an L-C filter is determined based on the secondary inductance and a harmonic frequency of a local oscillator (LO) signal. A capacitance value for the L-C filter is determined based on the inductance value and the harmonic frequency of the LO signal. The L-C filter is provided on an electric connection between a direct current (DC) bias voltage source and a secondary inductor of the differential transformer. The L-C filter is configured with the determined inductance value and the determined capacitance value.