Multiband Antenna Arrangement Using Switched Impedance Matching
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Solution Overview
Problem
Conventional small antennas face challenges in providing multiband operation across noncontiguous frequency bands without significant radiation losses, and they must also comply with specific absorption rate (SAR) standards for safe human exposure to RF radiation.
Innovation Solution
A diplexer with a switching circuit is used to create a dual radiator antenna arrangement, where reactances or impedances are selectively added between antennas and an RF ground using RF switches to shift operating bandwidths, allowing for dual-frequency band operation while maintaining efficient radiation and compliance with SAR standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the antenna is reduced, then the antenna becomes suitable for portable electronic devices, but the bandwidth decreases and Q-value increases, reducing the number of frequency bands the antenna can operate on
Solution Approach 1:
The antenna is divided into two separate radiator elements (first and second radiators) with different lengths. The first radiator is optimized for lower frequency bands while the second radiator is optimized for higher frequency bands. By segmenting the antenna into multiple specialized elements, the system achieves multiband operation capability that would be impossible with a single small antenna element.
Solution Approach 2:
The antenna system is designed to perform multiple functions across different frequency bands using a unified structure. The first and second radiators, along with their respective impedance matching networks, enable the antenna to operate across multiple noncontiguous frequency bands (including GSM 850/900/1800/1900 and UMTS bands) while maintaining adequate radiation efficiency in each band.
2Adaptability or versatility
If conventional matching components and RF switches are used to increase antenna bandwidth, then the antenna can operate on multiple frequency bands, but significant radiation losses occur when the antenna size is decreased below a certain level
Solution Approach 1:
Different impedance matching networks are designed for each radiator element based on its specific electrical characteristics. The first impedance matching network is optimized for the first radiator's lower frequency operation, while the second impedance matching network is optimized for the second radiator's higher frequency operation. This localized optimization ensures maximum power transfer and minimum reflection losses for each frequency band without requiring excessive antenna size.
Solution Approach 2:
The antenna system employs RF switches to dynamically reconfigure the impedance matching networks based on the operating frequency band. When transitioning between frequency bands, the switches redirect the RF signal to the appropriate radiator and matching network combination, enabling the antenna to maintain optimal performance across multiple bands while minimizing radiation losses in each specific band.
3Device complexity
If a single antenna element is used to operate on various frequency bands, then the antenna structure is simple, but the bandwidth properties are insufficient to achieve adequate radiation efficiency across all bands
Solution Approach 1:
The antenna system transitions from a single-dimensional (single element) structure to a two-dimensional (multiple elements with different orientations and lengths) structure. The first radiator extends in one direction while the second radiator extends in a different direction, creating a planar configuration that enables operation across multiple frequency bands. This dimensional expansion allows the antenna to achieve the necessary electrical length for lower frequencies while maintaining a compact physical footprint suitable for portable devices.
Data Source
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AI summary
An antenna arrangement includes a switch having an open state and a closed state, a first antenna that operates as a first active driven element in a first frequency band in response to the switch being in the open state, and a second antenna that operates as a second active driven element in a first frequency band in response to the switch being in the open state. The closed state configures the first antenna and the second antenna to operate in a second frequency band different from the first frequency band by operatively coupling a first impedance multiband antenna arrangementbetween the first antenna and a radio frequency ground, and by operatively coupling a second impedance between the second antenna and the radio frequency ground. The first antenna functions as a parasitic element in the second frequency band and the second antenna functions as an active driven element in the second frequency band.