Variable Gain Amplifier With Inductive Phase Calibration
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Solution Overview
Problem
Conventional variable gain amplifiers (VGAs) in phased array systems face challenges in maintaining constant phase and stable gain steps across different frequencies, leading to inconsistent performance and beam direction issues, particularly in 5G millimeter wave frequency bands and in-vehicle millimeter wave radar systems.
Innovation Solution
A variable gain amplifier design incorporating an amplification circuit, a control circuit, and an inductive load coupled with an inductive adjustment circuit, which uses mutual inductance to calibrate and stabilize the phase and gain step of the output signal, ensuring consistent performance across frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a common-gate transistor is switched to change gain, then the gain of the VGA is adjusted, but the phase of the output signal becomes inconstant and gain steps become unstable at different frequencies
Solution Approach 1:
An inductive adjustment circuit is introduced as an intermediary between the switching transistor and the output matching network. This inductive circuit mediates the effect of switching on the output phase by providing a frequency-dependent impedance that compensates for phase variations, thereby maintaining constant phase across different gain states while still allowing gain adjustment through the switching transistor.
Solution Approach 2:
The inductive adjustment circuit changes its effective impedance parameters based on frequency to compensate for the phase variations introduced by the switching transistor. By adjusting the inductive reactance parameter XL to match the frequency-dependent characteristics of the switching transistor, the circuit maintains constant output phase across different frequencies and gain states.
2Adaptability or versatility
If the M1 transistor is turned on to reduce gain, then the gain decreases, but the load capacitances of the output matching network become different causing output phases to be inconstant
Solution Approach 1:
The inductive adjustment circuit serves as a mediator between the gain-control transistor M1 and the output matching network. When M1 switches to change gain, the inductive circuit provides a compensating reactance that offsets the phase changes caused by varying load capacitances, thereby maintaining stable output phase despite gain transitions.
Solution Approach 2:
The inductive reactance XL acts as an electrical counterweight to the capacitive effects introduced by the switching transistor and output matching network. By setting XL to have an inductive reactance that counterbalances the capacitive reactance at the operating frequency, the circuit compensates for phase variations and maintains constant phase output during gain switching.
3Adaptability or versatility
If the M1 transistor introduces alternating current to the power supply voltage, then the gain is reduced, but the proportions of current introduced are different for signals at different frequencies causing unstable gain steps
Solution Approach 1:
The inductive adjustment circuit changes its impedance parameter XL with frequency to compensate for the frequency-dependent current division caused by the switching transistor. By making XL frequency-dependent, the circuit ensures that the effective gain step remains consistent across different signal frequencies, stabilizing the gain switching characteristic.
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 solution enables the variable gain amplifier to maintain a constant phase and stable gain step, improving beam precision and directionality in phased array systems, particularly in high-frequency applications like 5G and in-vehicle radar systems.
Implementation Method 1
an inductive load and an inductive adjustment circuit, where the inductive load is coupled to a signal output end of the amplification circuit, and the inductive adjustment circuit and the inductive load are inductively coupled
Data Source
AI summary
This application provides example variable gain amplifiers and example phased array transceivers. One example variable gain amplifier includes an amplification circuit, configured to amplify an input signal; a control circuit, configured to control a gain of the amplification circuit by adjusting an output current of the amplification circuit; an inductive load, where the inductive load is coupled to a signal output end of the amplification circuit; and an inductive adjustment circuit, where the inductive adjustment circuit and the inductive load are inductively coupled, and where the inductive adjustment circuit is adjustable.