AN4190

Antennas for low power applications

Doc ID 023812 Rev 1

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Figure 15.

Helical antenna implementation

Figure 16.

Helical antenna axial mode 3D radiation pattern

2.2

Microstrip patch antenna

Microstrip antennas became very popular in the 1970s primarily for space borne

applications. Today they are used for government and commercial applications. These

antennas consist of a metallic patch on a grounded substrate. The metallic patch can take

many different configurations; however the rectangular and circular patches are the most

popular because of ease of analysis and fabrication, and their attractive radiation

characteristics. Microstrip antennas are low profile, conformable to planar and non-planar

surfaces, simple and inexpensive to fabricate and mechanically robust when mounted on

rigid surfaces. When the particular patch shape and mode are selected they are very

versatile in terms of resonant frequency, polarization, pattern and impedance.

Major operational disadvantages of the microstrip antennas are their low efficiency, low

power, high Q (sometimes in excess of 100), poor polarization purity, poor scan

performance, spurious feed radiation and very narrow frequency bandwidth, which is

typically only a fraction of a percent or at most a few percent.

AM16439v1

AM16440v1