Thingmagic M5e-Compact Bedienungsanleitung PDF herunterladen (Seite 35)

RF Power Setting

Functionality of the Embedded Modules 35

RF Power Setting

The power setting is calibrated at the factory and parameters are stored in flash memory

to ensure the power output is within +/– 1 dB of the desired setting. The power limits are

set by both hardware limitations and enforced by the firmware.

Power Units

All power values are reported in centi-dBm. Therefore, a power setting of 2500

corresponds to 25 dBm. All power values in the serial interface are specified as unsigned

16-bit integers. A dBm means power referenced to 1mW. Therefore, the conversion from

watts to dBm is:

dBm = 10 log

(power in mW)

For example: 0.1W = 100mW = 20dBm and 1W = 1000mW = 30dBm.

Power Calibration

A power calibration event occurs when the Power set point is changed, the Frequency is

changed, or the RF field is turned on. The power calibration routine calibrates the power

within 10 ms.

Note

Power calibration only occurs once when the RF power is turned on. It does

not occur periodically when the RF field is on.

This is not an issue during normal operation, since a frequency hop occurs at least every

400 ms and thermal drift does not affect the power level significantly. However, in CW

waveform mode (Transmit CW Signal), no power calibration occurs unless the power or

frequency is changed. Thus, it is possible to experience thermal drift in this usage if the

unit is left to transmit continuously for a significant period of time.

TX Read Power

The TX read power is used for all non-write commands to tags. This may include, but is

not limited to, commands to read a tag ID and read tag data.The TX Read Power can be

set in two ways:

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Thingmagic M5e-Compact Bedienungsanleitung Seite 35