User Manual

ManualsBrandsCalAmp Wireless Networks ManualsElectronicsT-96SR UHF Telemetry Transceiver/Modem

PROGRAMMING

3-6

June 1997

Part No. 001-3412-002

3.3 RECEIVE TO TRANSMIT SEQUENCE

1. Synthesizer is loaded (24-bit D, B and A0). Refer

to Figure 3-6.

2. The state of the RX_EN line does not have to be

changed until the last bit is sent. However, receive

will cease as soon as it is changed.

3. The SYNTH ENABLE line should be held HIGH

for 2 to 3 milliseconds after the last word is sent.

This puts the frequency synthesizer in a SPEEDUP

MODE and slightly improves lock times.

4. After the last word is strobed in, 7 milliseconds

(worst case) should elapse before TX_EN is turned

ON. This allows the synthesizer to come within

1 kHz of the desired frequency.

Figure 3-6 RX TO TX TIMING DIAGRAM

"Ramp-Up" is the amount of time required for the

transmitter to reach full power once the TX EN has

been applied. The Ramp-Up circuitry (located on the

transceiver) minimizes adjacent channel interference

caused by spectral spreading (sinx/x) when the trans-

mitter is keyed. The Ramp-Up time is approximately

3 ms.

D0D24D0 D24 D0 D24

"D" WORD "B" WORD "A" WORD

DATA

CLOCK

t=0

SPEEDUP

RAMP-UP

LOCK

RX_EN

SYNTH_EN

9V TX

TX_EN

3.4 TRANSMIT TO RECEIVE SEQUENCE

1. TX_EN is turned OFF. This signal is shaped. Refer

to Figure 3-7.

2. The synthesizer load process could begin slightly

before, but when the last bit is strobed in the synthe-

sizer it will become unlocked.

3. The RX_EN line should switch from low to high

AFTER the TX_EN is switched. The RX_EN not

only turns the RX circuits on but also Pin Shifts the

VCO.

Figure 3-7 TX TO RX TIMING DIAGRAM

4. For quickest lock times the SYNTH ENABLE line

on the last load word should be held high for 2 to 3

milliseconds. It MUST NOT be left high as the syn-

thesizer in the SPEEDUP mode has poor noise per-

formance and would degrade the receiver

performance.

Speedup is 2 to 3 ms

Lock is approximately 7 ms

Ramp is approximately 3 ms

Dekey is approximately 3 ms

"Ramp-Down" is the amount of time required for

the transmitter output power to be reduced before

switching off the transmitter and enabling the receive

with the RX_EN. The Ramp-Down circuitry (located

on the transceiver) minimizes adjacent channel inter-

ference caused by spectral spreading (sinx/x) when the

transmitter is un-keyed. The Ramp-Down time is

approximately 3 ms.