Multi-Stage Microstrip Directional Coupler for Ultra-Wideband Directivity
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Solution Overview
Problem
Existing directional couplers face a trade-off between bandwidth, directivity, and compactness, making it difficult to achieve high directivity and ultra-high bandwidth while maintaining a compact size, especially in wideband applications.
Innovation Solution
A compact microstrip directional coupler is designed with two stages, one operating from 0.4 GHz to 1 GHz and the other from 1 GHz to 6 GHz, connected via an RF switch, allowing for high directivity and ultra-high bandwidth operation from 0.4 GHz to 6 GHz, achieving a compact structure suitable for MMIC integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a single-stage directional coupler is designed for wide bandwidth operation, then the bandwidth increases, but the directivity deteriorates
Solution Approach 1:
The directional coupler is divided into multiple stages, each optimized for specific frequency ranges. The first stage handles 0.4-1 GHz with one coupling structure, while the second stage handles 1-6 GHz with a different coupling structure. This segmentation allows each stage to maintain high directivity in its designated band while collectively achieving ultra-wide bandwidth coverage.
2Measurement precision
If the directional coupler is designed for high directivity, then the directivity improves, but the bandwidth is limited
Solution Approach 1:
The multi-stage directional coupler system performs multiple functions: the first stage coupler handles lower frequencies (0.4-1 GHz) with optimized coupling for that band, while the second stage coupler handles higher frequencies (1-6 GHz). The RF switch dynamically selects which stage is active based on input frequency, making the system universally applicable across the entire 0.4-6 GHz range while maintaining high directivity at any given frequency.
3Duration of action of stationary object
If multiple stages are used to achieve wide bandwidth, then the bandwidth increases, but the device complexity increases
Solution Approach 1:
Multiple directional coupler stages are merged into a single integrated structure with common input and output ports. The stages are coupled through shared transmission lines and grounded via common ground connections, creating a unified device that operates across ultra-wide bandwidth while maintaining a compact form factor suitable for MMIC integration.
4Ease of manufacture
If the directional coupler is made compact, then the ease of integration improves, but the bandwidth is restricted
Solution Approach 1:
The directional coupler achieves compactness by utilizing vertical stacking and multi-layer microstrip architecture. Transmission lines are routed in different physical layers and dimensions, allowing multiple coupling stages to be integrated in a compact footprint while maintaining the electrical performance required for ultra-wide bandwidth operation across 0.4-6 GHz.
Data Source
AI summary
The directional coupler supports ultra high bandwidth of 5600 MHz (from 400 MHz to 6 GHz) in compact structure and also provides high directivity of (>15 dB). The coupler uses a two stage micro-strip directional coupler for a frequency range of 400 MHz to 6 GHz, where the first stage supports a frequency of operation from 0.4 GHz to 1 GHz and the second stage supports a frequency of operation from 1 GHz to 6 GHz and the required coupled port can be chosen using a radio frequency switch as required by the application used in.