Texas Instruments TCM4300 manual Transmit I And Q Output Level, Wide-Band Data Demodulator

Dibit

In

D Q

BST Offset	Channel Delay	TXI,
Delay	(15.5 SINT Periods)	TXQ

TXGO

SINT

CLK

DQ

CLK

Delay = 0, 1/4, 1/2, 3/4

BST Offset

Delay

SYNOL

MPAEN

Transmit Channel Delay + d(T/8)

Occurs from last symbol (2 SINT periods) before TXGO goes low

PAEN Delay
9.5	PAEN
19.5

PAEN Delay + d(T/8)

TXGO high: 9.5 SINT periods + d(T/8): PAEN high

TXGO low: 19.5 SINT periods + d(T/8): PAEN low

Figure 4±2. Transmit Power Ramp-Up/Ramp-Down Functional Diagram

4.5Transmit I And Q Output Level

In the digital mode, the output level at TXI and TXQ is controlled by the TCM4300. During the burst, but not including ramp-up or ramp-down periods, the average output level (I2 + Q2)1/2 should approximate the specified value. There is no variable level control for TXI and TXQ within the TCM4300 other than the fixed ramping. In the analog mode, the output of the TCM4300 depends only on the sample values written to the TXI and TXQ registers.

There are small differences in the average output power levels between the digital and the analog modes. These differences require compensation at the system level by a small attenuation in the sample values of the analog output.

When a change in transmit power is necessary, the microcontroller can change the value sent to the PWRCONT DAC, the output of which can be connected to a voltage-controlled attenuator in the transmit path of the RF section.

4.6Wide-Band Data Demodulator

The wide-band data demodulator (WBDD) module demodulates the FM signal and outputs a Manchester-decoded data stream. The WBDD is used for receiving the analog control channels of the forward control channel (FOCC) and the forward voice channel (FVC). The bit error rate (BER) performance requirements are listed in Table 4±8.

4±7