User guide

CM52 Integrators’ Manual
WI_DEV_CM52_UGD_001-001
Page 37 of 53
CM52 Integrators’ Manual
Figure 19: Antenna Diagnostic Circuit
The current antenna status is based on a comparison between the voltage measured at the antenna
connector and the limits set by the application for OPEN and SHORT.
Because of the tolerances associated with Wireless CPU
®
power supply, ADC power supply and the
ADC itself, there will be a correction factor in the ADC reading as listed below in
Table 25.
Lower Limit Nominal Higher Limit
ADC Reading Correction (%) -5 4 11
ADC Correction (Multiplying Factor) 0.95 1.04 1.1
Table 25: Range of ADC readings for an external antenna
Example: The multiplying factors shown above are used to establish the ADC limits values for an
antenna OPEN, SHORT and nominal conditions of a known antenna resistance value. These limits
can be calculated using the formula below:
ADC Reading = 255 * Multiplying Factor * RL/(R+ RL)
The following example shows calculation using internal resistance (R) = 49.9K and antenna
resistance (RL) = 10K.
Lower Limit of ADC Reading = 255 * 0.95 * 10k/ (49.9k + 10k) = 41
Nominal Value of ADC Reading = 255 * 1.04 * 10k/ (49.9k + 10k) = 45
Upper Limit of ADC Reading = 255 * 1.1 * 10k/ (49.9k + 10k) = 47
Note: All ADC values should be rounded up to next integer value.
This document is the sole and exclusive property of WAVECOM. Not to be distributed or divulged without prior written agreement.
Ce document est la propriété exclusive de WAVECOM. Il ne peut être communiqué ou divulgué à des tiers sans son autorisation préalable