Motorola M3097 Service Manual download pdf (Page 85)

TDMA M3090/M3097: Antenna Circuit

RF Connector

Antenna

TX_2.75

800*_1900

800MHz

1900MHZ

U704 RF Switch

U104

Q104

Q105

Description

Two RF ports are designed in this transceiver; internal antenna port and RF connector port. The RF switch (U704) controls which antenna path is going to be used during

operation. Since this transceiver operates in two frequency bands (800MHz and 1900MHz), U704 also controls the RF frequency paths. U704 has two control inputs which

are used to control the RF port that will be used and frequency band routing.

The antenna will be used only when there is no 50 Ω load detected by U104 at the RF Connector port.

The output of U104 is determined by the input states of 800*_1900 line, 800_1900* line and the RF Connector load detect line. Refer to the Band Select and Antenna

Select chart on page B3 for a detailed description on how the d ifferent input states affect the outputs of both U104 and U704.

800*_1900 and 800_1900* determines the desired frequency band. A high (2.75V) state at 800*_1900 designates 800M Hz mode while a low (0V) state designates

1900MHz. The opposite holds true for 800_1900* .

Having a high state at V2 and a low state at V1 will configure U704 to route the antenna port to the 1900MHz RF path and the RF Connector port to the 800MHz RF path.

A low state at V2 and a high state at V1 will configure U704 to route the antenna port to the 800MHz RF path and the RF Connector port to the 1900M Hz RF path.

Only one RF port and frequency band is used at a time, therefore, only one RF switch con figuration is used while the other is irrev elent.

800_1900*

FL930

FL931

-5V