CC1021-RTR1 datasheet(59/91 Pages) TI1

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7125

Not Recommended for New Designs NRND

CC1021

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SWRS045D – JANUARY 2006 – REVISED JANUARY 2015

5.21 Antenna Considerations

CC1021 can be used together with various types of antennas. The most common antennas for short-

range communication are monopole, helical and loop antennas.

Monopole antennas are resonant antennas with a length corresponding to one quarter of the electrical

wavelength (

). They are very easy to design and can be implemented simply as a “piece of wire” or

even integrated onto the PCB.

Non-resonant monopole antennas shorter than

can also be used, but at the expense of range. In size

and cost critical applications such an antenna may very well be integrated onto the PCB.

Helical antennas can be thought of as a combination of a monopole and a loop antenna. They are a good

compromise in size critical applications. But helical antennas tend to be more difficult to optimize than the

simple monopole.

Loop antennas are easy to integrate into the PCB, but are less effective due to difficult impedance

matching because of their very low radiation resistance.

For low-power applications, the

monopole antenna is recommended due to its simplicity as well as

providing the best range.

The length of the

monopole antenna is given by:

(34)

Where:

f is in MHz, giving the length in cm.

An antenna for 868 MHz should be 8.2 cm, and 16.4 cm for 433 MHz.

The antenna should be connected as close as possible to the IC. If the antenna is located away from the

input pin the antenna should be matched to the feeding transmission line (50

Ω).

For a more thorough background on antennas, please refer to Application Note AN003 SRD Antennas

(SWRA088).

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