Ericsson LBI-31629B manual System Analysis, Radio Board, Transmit Circuits

LBI-31629

2.	Use the DTMF keypad or use the Recall Telephone
	Number key (RCL) to enter the digits of the tele-
	phone number.
3.	Press the secondary key	and then press the
	SEND key. An optional tone (sidetone) may be
	heard as each digit is transmitted.
4.	When someone answers, press the PTT bar and
	speak directly into the grille on the radio, or across
	the face of an external microphone. Release the
	PTT bar as soon as you stop talking. Messages can
	not be received when the PTT bar is pressed.
5.	When the conversation is completed, press the (#)
	key to disconnect from the telephone system.

To Recall a Telephone Number:
The RCL button is used to recall the last number dialed
or to recall one of the ten 16-digit numbers that can be stored
in memory.
To Recall the Last Number Dialed:
1.	Press the secondary key	and then the RCL
	button.
2.	Then press the secondary key and then the SEND
	key as in Step 3 of To Make a Telephone Call.
To Recall a Telephone Number Stored in Memory:
1.	Press the key number of the memory location (1
	through 9).
2.	Press the secondary key	and then the RCL
	key.
3.	Press the secondary key and the SEND key as in
	Step 3 of To Make a Telephone Call.

SYSTEM ANALYSIS

Ericsson GE M-PD Personal radios are two-way, FM ra- dios designed for public communications. The M-PD Sys-

	tem radio consists of four printed wire boards as follows:
	∙ Radio Board: carries the transmit, receive and fre-
	quency synthesizer circuits
	∙ Control Board: supports logic, control and audio
	processor circuits
Figure 2 - Block Diagram	∙ Display Board: carries LCD displays

∙Signaling Board: provides additional software con- trolled signaling functions

Interconnection of the control board with other boards and control circuits is made with flexible circuit boards and connectors. All control leads which are "barred", such as PTT, mean that the function indicated occurs when the lead is in a low voltage condition.

Circuit illustrations shown in the following text are sim- plified representatives of actual circuits. They are intended only to illustrate basic circuit functions.

RADIO BOARD

Transmit Circuits

The M-PD transmit circuit, as shown in Figure 2 - Block Diagram, consists of the following integrated circuit mod- ules:

∙	Amplifier	(TX-Amp)
∙	Power Amplifier	(PA)
∙	Power Controller	(PC)
∙	Antenna Switch	(AS)
∙	Filter Network	(FN)

Amplifier Module (A201):

Amplifier module (TX-Amp) A201 is a single stage RF amplifier hybrid IC. A 0 dBm RF signal on the input will produce a +23 dBm signal on the output (refer to Figure 3). This module is broadband and does not require tuning.

Figure 3 - Amplifier Module (TX-Amp)

Power Amplifier Module (A202):

Power Amplifier (PA) A202 is a three stage, wide band amplifier module with an input and an output impedance of 50 ohms (refer to Figure 4). The first stage of the PA mod- ule has the DC power supplied by power control transistor

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