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Fixed-frequency beam-steerable leaky-wave microstrip antenna
| Details |
Inventors: Noujeim, Karam Michael;
Assignee: Anritsu Company (Morgan Hill, CA)
Primary Examiner: Ho; Tan
Assistant Examiner:
Attorney, Agent or Firm: Fliesler Meyer LLP
A fixed frequency continuously beam-steerable leaky-wave antenna in microstrip is disclosed. The antenna's radiating strips are loaded with identical shunt-mounted variable-reactance elements, resulting in low reverse-bias-voltage requirements. By varying the reverse-bias voltage across the variable-reactance elements, the main beam of the antenna may be scanned continuously at fixed frequency. The antenna may consist of an array of radiating strips, wherein each strip includes a variable-reactance element. Changing the element's reactance value has a similar effect as changing the length of the radiating strips. This is accompanied by a change in the phase velocity of the electromagnetic wave traveling along the antenna, and results in continuous fixed-frequency main-beam steering. Alternatively, the antenna may consist of two long radiating strips separated by a small gap, wherein identical variable-reactance elements are mounted in shunt across the gap at regular intervals. A continuous change in the reactance value has a similar effect as changing continuously the width of the radiating strips. This results in a continuous change in the phase velocity of the electromagnetic wave traveling along the antenna, thereby achieving continuous fixed-frequency main-beam steering. |
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DETAILED DESCRIPTION The present invention addresses the limitations and disadvantages of the prior art by introducing a fixed-frequency continuously beam-steerable leaky-wave antenna in microstrip.
The antenna's radiating strips are loaded with identical shunt-mounted variable-reactance elements, resulting in low reverse-bias-voltage requirements.
The microstrip antenna is excited in its first higher-order mode by means of two equal-amplitude and 180°-out-of-phase signals.
These signals are applied to the feed end of the microstrip at two ports.
The microstrip antenna length is chosen such that more than 90% of the input power is radiated by the electromagnetic wave by the time it reaches the terminated antenna end.
By varying the reverse-bias voltage across the variable-reactance elements, the main beam of the antenna may be scanned continuously at fixed frequency.
In one embodiment, the antenna consists of an array of radiating strips.
In this embodiment, each strip includes a variable-reactance element.
The variable-reactance element is generally uniform throughout the microstrip.
Changing the element's reactance value has a similar effect as changing the length of the radiating strips.
This is accompanied by a change in the phase velocity of the electromagnetic wave traveling along the antenna, and results in continuous fixed-frequency main-beam steering.
In another embodiment, the antenna consists of two long radiating strips separated by a small gap.
In this embodiment, variable-reactance elements are mounted in shunt across the gap at regular intervals.
In one embodiment, the variable-reactance elements are about the same or identical.
A continuous change in the reactance value has a similar effect as changing continuously the width of the radiating strips.
This results in a continuous change in the phase velocity of the electromagnetic wave traveling along the antenna, thereby achieving continuous fixed-frequency main-beam steering.
The variable-reactance elements can take the form of varactor diodes, ferroelectric films such as BST (Barium Strontium Titanate), or MEMS (Micro-Electro-Mechanical Systems) varactors
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