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DESCRIPTION

The TR-XXX-SC-PA module is a single-channel, half-duplex transceiver

designed for the wireless transmission of digital or analog information over

distances of <300 feet outside and <150 feet inside. The PA version has a lower

output power than the standard SC and has been pre-certified by the FCC which

greatly reduces the time to market and cost of product introduction. No external

components (excluding an antenna) are required. The module incorporates an

on-board switch allowing the use of a single antenna. Linx offers a wide selection

of antennas designed for use with the transceiver module.

The transceiver is half-duplex; therefore, it can only be operated in one mode at

a time: either transmit mode or receive mode. When transmitting, the receiver is

powered down. Likewise, the transmitter is powered down in receive mode.

The transmit section of the transceiver is capable of producing up to 1mW of

output power while maintaining harmonics and spurious emissions within legal

limits. The power amplifier can be adjusted over a 15dB adjustment range via

the LVLADJ pin. This is very useful for optimizing a product during FCC testing.

The transmitter directly modulates the carrier with the baseband signal present

at the TXDATA pin. If the signal is analog in nature, it will FM modulate the carrier.

If the signal is digital, the modulation method becomes FSK. In either case the

carrier’s peak deviation is determined by the modulating signal’s amplitude.

The receive section of the transceiver is capable of recovering a signal as low as

-94dBm (typical). The receiver operates in a single conversion superhet

configuration, with an IF of 10.7 MHz. A quadrature demodulator is used to

recover the baseband analog signal from the carrier. This analog signal is low-

pass filtered and then made externally available to the user via the audio pin. It

is also passed to the data slicer for squaring of digital content.

The transceiver has an on-board voltage regulator that regulates the internal

VCC to 3.0V. This allows a wide operating voltage range of 2.7V to 13V. At 2.7V,

the internal regulator acts as a saturated switch, directly passing voltage through

to the internal electronics. The PDN pin can be used to put the transceiver into

a low-current sleep mode (<50uA).

DUAL TIMEBASE

PLL

See Table 1

RX

See Table 1

TX

POWER

AMP

LVLADJ

RECEIVE

CRYSTAL

14.152813MHz

TRANSMIT

CRYSTAL

14.31818MHz

RSSI

MODULATION IN

10.7MHz

Filter

SAW Filter

10.7MHz

Filter

17KHz

Filter

DEMOD

AUDIO

DATA

IF LIMITER

IF

AMPLIFIER

DIFFERENTIAL

LO

(905.78MHz)

LNA

RF

IN

Figure 6: SC-PA Block Diagram