Datasheet AT48810-RB, AT48810-LH, AT48810-LB, AT48810-CH, AT48810-CB Datasheet (ATMEL)

900 MHz
Spread­Spectrum RF
Module

Preliminary

Features

0625A

Designed for use with Atmel ’s AT 48 80 2 Spre ad -Spectrum Signal Processo r

•

FCC Part 15, Unlicensed Operati on

•

RF Despreading and Narro wba nd IF for Hig he st Ja mming Margin

•

1 mW Narrowband Operation, or 1 and 50 mW Spread-Spectru m Operation

•

Description

The AT48810 RF module is intended for time domain duplex spread-spectrum com­munications under FCC Part 15, 902-928 MHz unlicensed operations. This module
features RF despreading and narrowband IF for powerful interference rejection.
Spreading is via direct sequence. The unit can also be operated in a narrow-band
configuration (FCC limits power to 1 mW in narrow band) by restricting the DC voltage
to the power amplifier so that the transmit power is less than 0 dBm per FCC regula­tions. The unit can also be run in slow half duplex or simplex mode.

AT48810

Pin Diagram

15.36 MHz Clock Out
Ground

V

Synthesizer Data Clock Input

Synthesizer Data Input

Synthesizer Data Latch Input

Modulation Input

No Connection

PN Spreading Enable Input

PN Input

Note: 1. Connector on modu le is Dup on t/ Berg part number 87814-610.

Mating connector is 87409-110.

1

2

Audio Out

3

4

Ground

5

6

CC

7
9
11
13
15
17
19

RSSI Out

8

T/R Switch

10

LNA Gain Hi/Low

12

V

CC

14

No Connection

16

Transmit PowerOn/Off Input

18

PowerAmp V Input

20

PowerAmp V Input

CC

CC

3-1

Block Diagram

GAIN

PA V

ON/OFF

AMP

ON/OFF

CC

f = 83.16 MHz

C

Bw = 30 kHz

DOWN
CONVERTER

XTAL OSC

83.16 ± 1.23 MHz

HANDSET OR BASE

UPCONVERTER SPREAD

f = 915 MHz

C

OTHER CIRCUITS

V

CC

ON/OFF

f = 1.23 MHz

C

PN ENABLEPN

RSSI

SYNTHESIZER

TX PWR

LNA IF AMP

ANTENNA

PORT

T/R

SWITCH

902-

928 MHz

TR SW

TX PWR

Note: 1. Th e modu le canno t le gall y be cert if ied wit ho ut an ante nna; thi s is an FCC requi remen t.

DISCRIMINATOR

3

TCXO

15.36 MHz

AUDIO

DATA

CLOCK

TDD Rate

7.5 kHz max

Operating Frequenc ies

Table 1. Version “B”

Channel N

1 1334 825.7536 910.1424 908.9136
2 1350 829.4400 913.8288 912.6000
3 1356 833.1264 917.5152 916.2864
4 1363 837.4272 921.8160 920.5872

Note: 1. Second LO = 84.3888 MHz

2. Reference Divider = 25

3. Phase Detector = 614.4 kHz

4. First IF = 83.160 MHz

5. Second IF = 1. 229 MHz

3-2 AT48810

(1, 2, 3, 4, 5, 6, 7, 8)

End B

First LO, MHz TX, MHz RX, MHz

6. Synthesizer PLL Bandwidth = 80 kHz nominal

7. Frequency Accuracy = ± 3.5 ppm
(including temperature 0° to 50°C)

8. Switching Time = 2.2 ms nominal, Ch 1 to Ch 4

AT48810

Table 2. Version “H”

Channel N First LO, MHz TX, MHz RX, MHz

1 1346 826.9842 908.9136 910.1424
2 1352 830.6688 912.6000 913.8288
3 1358 834.3552 916.2864 917.5152
4 1365 838.6560 920.5872 921.8160

Note: 1. Second LO = 81.9312 MHz

2. Reference Divider = 25

3. Phase Detector = 614.4 kHz

4. First IF = 83.160 MHz

5. Second IF = 1. 229 MHz

(1, 2, 3, 4, 5, 6, 7, 8)

6. Synthesizer PLL Bandwidth = 80 kHz nominal

7. Frequency Accuracy = ± 3.5 ppm
(including temperature 0° to 50°C)

8. Switching Time = 2.2 ms nominal, Ch 1 to Ch 4

Transmit Modulation Input

Type PM, inside the phase lock loop
Bandwidth 200 Hz to 70 kHz, -3 dB
Sensitivity 20 cycles/V nominal
Distortion -30 dBC max. for 10 cycle peak deviation at 1 kHz rate

Spreading Input

Type BPSK
Bandwidth 30 MHz
Sensitivity 2.5 V
PN Enable Input +5V = spread, high Z = CW
Carrier Suppression -15 dBc max.
Code Leakage -30 dB max. (for baseband modulation signal of better quality)
PN Input Load Resistance 1K nominal

for BPSK

PP

Antenna Port

Zo 50 ohms nominal
VSWR 2.5:1 max., 902-928 MHz
T/R Switch Low = transmit, CMOS compatible. Isolation 35 dB nominal

3-3

Transmit Power

Power Output +17 dBm at VCC = 5.0 VDC,

VPA = 4.0 VDC

On/Off Control TX PWR input pin 16, CMOS

compatible, low = power on

RF power amp VCC is on a separate pin
from the other circuits V

CC

.

Receive

Sensitivity -105 dBm max. at 12 dB SINAD (C-weighted)
IF Bandwidth 30 kHz at -3 dB nominal
Signal-to-Noise 30 dB min. C-weighted at -80 dBm
Post Detection Net Bandwidth 15 kHz, limited by IF filter
RSSI Output Log compressed. Slope 0.24 uA/dB nominal into a zero ohm load. Rout =

58K nominal. Bandwidth 15 kHz, limited by IF filter. Noise floor - 110 dBm
equivalent input.

Attenuators T/R switch → T gives 35 dB nominal, low = transmit. GAIN control gives

17 dB nominal in LNA low = high gain. (binary controls: on/off only, CMOS
compatible.)

Audio Output Sensitivity 0.4 uA/kHz nominal into a zero ohm load. Rout = 58K nominal.

This output must be lowpass filtered (-3 dB at 200 Hz, 6 dB/octave) to give
net link frequency response which is flat.

Interface Rejection Out of Band

Antenna filter is -6 dB at fo ±32.5 MHz and approx. -30 dB at fo ±100 MHz.
A cellular phone with 1 watt power at a distance of 5 feet produces no
noticeable SNR degradation in the receiver for the mating transmitter at a
distance of 10 feet, running spread spectrum R13 code.

In Band

Processing gain depends on code length. The use of RF despreading
assures that the high processing gain can be maximally effective by
allowing narrow IF bandwidth thus significantly reducing IF jamming
induced desensitization.

Clock Output

15.360 MHz buffered from TCXO, CMOS compatible, one
standard load.

Data Port

SPI/3-wire, 3 lines. Synthesizer device is National Semi­conductor LMX1501 or equal.

3-4 AT48810

Power Supply

Voltage +4.5 VDC min., +5.5 VDC max.
Current Transmit only 185 mA nominal

TDD 50/50 130 mA nominal
Receive only 85 mA nominal

AT48810

Turn-On Time

for 1 ppm error from final frequency
Power Amp +4.0 VDC full power, +0.6 VDC for Pout < 0 dBm

Note: 1. It is allowable to program th e synt he si zer before the TCXO is fully stabilized

1. TCXO, from V

2. Synthesizer, V

edge = 3 ms max.

CC

stabilized, from data latch edge = 3 ms max.

CC

Adjustments

There are no user adjustments. The three adjustments
are discriminator frequency adjust, TCXO nominal fre­quency, and transmit upconverter filter tuning.

Environment

Temperature 0° to 55°C
Humidity 10% to 90% non-condensing
Vibration
Shock

(1)

Physical

(Dimensional Drawings)

Antenna Port Options Center, Left, Right
Weight

Ordering Informati o n

Ordering Code Antenna Frequency Plan Second LO

AT48810-RB Right B 84.3888 MHz
AT48810-RH Right H 81.9312 MHz

AT48810-CB Center B 84.3888 MHz
AT48810-CH Center H 81.9312 MHz

AT48810-LB Left B 84.3888 MHz
AT48810-LH Left H 81.9312 MHz

3-5