RF Antenna Switch Biasing for Low Radiated Spurious Emission
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Solution Overview
Problem
RF antenna switches face challenges in maintaining low radiated spurious emission (RSE) levels during both active and inactive modes of operation, particularly due to unknown internal impedances during inactive modes, leading to elevated RSE beyond desired minimum levels.
Innovation Solution
The implementation of RF antenna switches with a through stack and shunt stack comprising N-type FET transistors, along with a bias signal generation circuit that generates positive and negative bias voltages, and an optional termination stack, which adjusts control voltages and impedances to manage RSE levels during active and inactive modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the RF antenna switch operates in inactive mode to reduce power consumption, then power consumption is reduced, but radiated spurious emission increases beyond desired minimum levels
Solution Approach 1:
The patent applies preliminary action by pre-configuring the switch element with specific impedance values during the inactive mode before any spurious emission can occur. The through stack and shunt stack are designed with predetermined impedance characteristics that automatically suppress RSE when the switch is inactive, without requiring active control or additional power consumption.
Solution Approach 2:
The patent utilizes parameter changes by varying the impedance values of the through stack and shunt stack based on the operational mode. During inactive mode, the impedances are set to specific values that minimize RSE, while during active mode, the impedances are adjusted to optimize signal transmission. This dynamic parameter adjustment resolves the contradiction between low power consumption and low RSE.
2Device complexity
If the internal impedances of the antenna switch are kept unknown during inactive mode to simplify control, then control complexity is reduced, but radiated spurious emission increases beyond desired minimum levels
Solution Approach 1:
The patent applies self-service by designing the switch element to automatically maintain appropriate impedance characteristics during inactive mode without requiring external control or monitoring. The through stack and shunt stack configurations inherently provide the necessary impedance values that suppress RSE, eliminating the need for complex control mechanisms while maintaining low emission levels.
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
This configuration effectively maintains RSE within desired minimum levels by controlling impedance mismatches and reducing intermodulation products, even during inactive modes with low power consumption.
Implementation Method 1
a first switch element coupled between a common port of the RF antenna switch and a first throw of the RF antenna switch, the first switch element comprising: a through stack comprising a plurality of N-type FET transistors arranged in series connection
Implementation Method 2
a bias signal generation circuit that generates positive and negative bias voltages, and an optional termination stack, which adjusts control voltages and impedances to manage RSE levels
Data Source
AI summary
Methods and devices to control radiated spurious emission (RSE) in an RF antenna switch are presented. The RF antenna switch includes a through stack that includes at least one regular N-type FET transistor and a plurality of intrinsic N-type FET transistors, and a shunt stack that includes a plurality of intrinsic N-type FET transistors. During an inactive mode of operation, the regular transistor turns OFF to present a high impedance. The RF antenna switch includes a termination stack having a plurality of regular P-type FET transistors that are activated during the inactive mode to present a termination impedance to the antenna. A bias signal generator that remains partially active during the inactive mode of operation to generate positive and negative control voltages having magnitudes that are sufficiently high to maintain ON/OFF control of the transistors of the stacks.