TDMA T2290/T2297:
PA Circuit
B16
Description
The final s tage PA circuit provides the n ecessary amount of power for RF trasmissi on through an antenna . U801 is a PA module that is capable of operating in the
800MHz band under anal og or digital mode.
In analog mode line arity of the PA is not as critical as when operating in digital m ode. For this reason, effeiciency is a more important factor than linearit y when operat-
ing in analog mode. In digital mode, because of its IQ modulation scheme, PA lin earity is a more important factor than efficie ncy.
Efficiency and lineari ty is controlled by varying the biasing of the PA(U801). In 1900MHz mode only one bias ing method is needed since 1900M Hz mode only operates
in digital mode .
Q1807 controls the supply voltage to U801. The PA supply is sourced from the B+ li ne. In 800MHz mode, 800KEY is held low ca using Q1807 to switc h on. When
800KEY is pulled high, Q1807 is turned off and the supply to U801 is cut off.
Q901 controls the supply voltage to U901. The PA supply is sourced from the B+ line. In 800MHz mode, 1900KEY is held low causing Q901 t o switch on. When
1900KEY is pulled high, Q901 is turned off and the supply to U901 is cut off.
After the TX carrier is ampli fied it's sent to the duplex filter for final tr ansmission through the antenn a.
U801
800BIAS
B+
800KEY
Q1807
800_PA_IN
TX_800
B+
Q901
TX_800
1900_PA_IN
1900BIAS
1900KEY
U901
Содержание T2290
Страница 1: ...DIGITAL WIRELESS TELEPHONE Service Manual Level 3 Release 1 TDMA T2290 T2297 ...
Страница 26: ... 2000 Motorola Inc TDMA T2290 T2297 Cellular Overview 16 ...
Страница 40: ...Motorola Confidential Proprietary TDMA T2290 T2297 TDMA Test Mode NAM Programming 30 ...
Страница 68: ...Disassembly TDMA T2290 T2297 Keypad Removal Motorola Confidential Proprietary 58 ...