CAD Antenna Designer Feed Networks and Impedance Matching Flashcards
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Read the first 7 CAD Antenna Designer Feed Networks and Impedance Matching flashcards as text
What is the primary purpose of a corporate (parallel) feed network in a phased array antenna?
Answer: To distribute equal amplitude and phase to all array elements
A corporate feed network distributes equal amplitude signals to all array elements via equal path lengths, ensuring uniform illumination and consistent phase across the entire array aperture.
How does a series feed network for a linear array differ from a corporate feed network?
Answer: Series feeds use less transmission line but exhibit beam squint with frequency change
Series feed networks require less transmission line material but cause beam squint (beam direction shift) as frequency changes because elements experience different electrical path lengths.
What is the function of a diplexer in an antenna system?
Answer: To combine or separate two frequency bands through a single antenna port
A diplexer uses bandpass and bandstop filters to combine or separate two different frequency bands at a single antenna port, allowing one antenna to serve two bands.
What type of feed antenna is most commonly used at the prime focus of a parabolic reflector?
Answer: Horn antenna
Horn antennas are the most common prime focus feeds for parabolic reflectors due to their well-controlled illumination patterns, low spillover, and compatibility with standard waveguide connections.
What is a rat-race coupler (ring hybrid) primarily used for in microwave feed networks?
Answer: To combine or split power with 0° or 180° phase difference between output ports
A rat-race coupler is a 180° hybrid that combines or splits power with either 0° or 180° phase difference depending on which ports are used, making it useful in balanced mixers and antenna feed networks.
What is the main advantage of using a tapered transmission line section in an antenna feed network?
Answer: To achieve gradual impedance transformation with low reflections over a wide bandwidth
Tapered transmission lines provide gradual impedance transformation that minimizes reflections by avoiding abrupt impedance steps, resulting in wider operating bandwidth than lumped matching networks.
In a traveling-wave series feed for a linear array, how are element spacing and feed line length coordinated?
Answer: Element spacing and feed line electrical length create a specific phase progression to form the beam
In a traveling-wave feed, the element spacing and feed line electrical length are designed together to produce a specific inter-element phase progression that directs the main beam at the desired scan angle.