Passive Mixer LLC Filter for Linearity and Harmonic Rejection
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Solution Overview
Problem
Existing RFIC transceiving circuits face challenges in achieving high linearity and wide bandwidth due to low output impedance and high power consumption, especially in high-frequency bands, which is exacerbated by the limitations of active mixer structures.
Innovation Solution
A passive mixer structure incorporating an LLC filter with a specific configuration of inductors and a capacitor, connected between the differential output of a transmission mixer and the differential input of a driving amplifier, to enhance impedance matching and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active mixer structures are used to achieve high current consumption, then mixing performance is improved, but power consumption increases and linearity deteriorates in high frequency bands
Solution Approach 1:
The patent replaces the active mixer structure with a passive mixer structure, substituting active devices (transistors) with passive devices (inductors, capacitors, resistors). This substitution eliminates the need for high current consumption while maintaining mixing performance, directly resolving the contradiction between mixing performance and power consumption in high frequency bands.
2Use of energy by moving object
If passive mixer structure is used to reduce power consumption, then power consumption decreases, but linearity and bandwidth are limited due to low output impedance
Solution Approach 1:
The patent introduces an impedance transformation network as an intermediary between the passive mixer and the subsequent stage. This network transforms the low output impedance of the passive mixer into a higher impedance level, improving linearity and bandwidth without requiring high current consumption. The intermediary network enables the passive mixer to achieve performance previously only attainable with active structures.
3Reliability
If output impedance of passive mixer is increased to improve linearity, then linearity improves, but impedance matching becomes difficult and bandwidth is restricted
Solution Approach 1:
The patent employs a dynamic impedance transformation network that can adapt its transformation ratio based on frequency. This dynamic characteristic allows the network to provide appropriate impedance transformation across a wide bandwidth while maintaining high linearity at the operating frequency. The network's ability to dynamically adjust its impedance transformation properties resolves the contradiction between linearity and bandwidth.
4Object-generated harmful factors
If conventional filter is used to reject harmonics, then harmonic rejection is achieved, but 3rd harmonic rejection ratio is insufficient and impedance is too low
Solution Approach 1:
The patent changes the fundamental parameters of the filter by using an impedance transformation network followed by a simpler filter structure. The impedance transformation network transforms the low impedance to a higher level, and the filter is designed to operate at this transformed impedance level. This parameter change approach achieves superior 3rd harmonic rejection ratio and high impedance without requiring a complex conventional filter design.
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 proposed solution improves the 3rd harmonic rejection ratio and reduces power consumption while maintaining a smaller size in higher frequency bands, achieving high impedance at the operating frequency and low impedance at harmonic frequencies, thus supporting wider bandwidths.
Implementation Method 1
the proposed solution improves the 3rd harmonic rejection ratio and reduces power consumption while maintaining a smaller size in higher frequency bands, achieving high impedance at the operating frequency and low impedance at harmonic frequencies
Implementation Method 2
the LLC filter comprising a first inductor connecting a first node of the differential output of the transmission mixer to a first intermediate node, a second inductor connecting a second node of the differential output of the transmission mixer to a second intermediate node
Implementation Method 3
a capacitor in parallel with the third inductor
Data Source
AI summary
Disclosed is a transmission radio frequency (RF) circuit including a transmission mixer configured to receive an intermediate frequency (IF) signal and up-convert the IF signal into an RF signal, a driving amplifier configured to amplify the RF signal, and an LLC filter electrically connected to a differential output of the transmission mixer and a differential input of the driving amplifier, the LLC filter comprising a first inductor connecting a first node of the differential output of the transmission mixer to a first intermediate node, a second inductor connecting a second node of the differential output of the transmission mixer to a second intermediate node, a third inductor connecting the first intermediate node to the second intermediate node, and a capacitor in parallel with the third inductor.