Because of wide temperature range and poor cooling of the RF block, it is neccessary to compensate the effect of temperature on the output power. To monitor this environment change, temperature measurement is done by using NTC resistor. Factor table is used for temperature compensation,. The table contains common values for all power levels and operating modes. Table values are defined without factory measurements. Temperature is measured and right compensation value is added to TXC-val-ue. Requirement for compensation update is for every 1 minutes or after every 5 degrees C of temperature change. This means, that during analog mode transmission there will be a need for temperature reading and TXC compensation update. Because of poor cooling of RF block and insufficient linearity in high temperatures, output power is reduced from level 2 to level 2.5 when temperature inside the phone is above +55 C in analog mode and above +60 C in digital mode.
Duplexer frequency response ripple is compensated by software. Power levels are calibrated on four channels in production. Values for channels between these tuned channels are calculated by using linear interpolation.
For saving battery capacity and because of insufficient linearity in digital mode, output power is decreased from level 2 to level 2.5, when battery voltage drops below 3.3V. (tbd.). The power reduction is done linearly as a function of battery voltage. Vcc 3.3V ... 3.1V -> PL2 ... PL2.5.
Transmitter output power up/down ramps are controlled by SW. A special ramp tables are used for that. Requirement is for nine different ramps in digital mode for both operating bands and one ramp for analog mode. Separate ramps are used in power up and power down ramps.
For optimum linerity and efficiency the output level of the modulator is adjusted in the production. AGC amplifier is used as 2 dB step attenuator to define power levels. The 0 dB level is the production tuned reference level.
Digital mode RSSI vs. input signal is calibrated in production, but RSSI vs. temperature and RSSI vs. channel are compensated by software.
Was this article helpful?
You can now recondition your old batteries at home and bring them back to 100 percent of their working condition. This guide will enable you to revive All NiCd batteries regardless of brand and battery volt. It will give you the required information on how to re-energize and revive your NiCd batteries through the RVD process, charging method and charging guidelines.