rfw102 ETC-unknow, rfw102 Datasheet - Page 8

• Manufacturer Part Number: rfw102
• Description: Rfw102 Transceiver Chipset Shortrang
• Manufacturer: ETC-unknow

Datasheet
October 2002
Rev. 1.03
Theory of Operation
The RF Waves modem is based on a SAW correlator that functions as a spreading/de-spreading element in
the system. The SAW correaltor is a 3-port passive device (described in this chapter).
Along with the SAW correlator, two other devices are embedded in the system: A 488MHz 1-port SAW
resonator – provides the source of frequency for the system, and a Silicon RFIC – functions as the active
part of the system. The silicon RFIC is an On Off Keying transceiver, which operates with an IF of 488MHz
and a LO of 1952MHz. The SAW resonator generates both frequencies.
System overview
The chipset includes three chips:
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•
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SAW Correlator Theory
The SAW correlator is a linear passive 3-port device. It can be represented as a series of delay lines with
band pass filters and phase inverters threaded between them. The current SAW correlator is a matched
filter, designed to match a 13-bit BPSK – modulated Barker code.
Impedance: All 3 ports of the SAW correlators are matched by external passive elements to 200Ω. The
matching circuit is presented in the schematic diagram.
Frequency of Operation: The central frequency of operation is 488MHz.
Spreading Chip Rate: The chip rate is 21 cycles/chip = 43ns/chip = 23Mcps.
Interrogation: In order to produce the spread sequence (in the transmitting side of the module) the SAW is
interrogated by a 488MHz 76ns RF pulse. The pulse is characterized by a rise/fall time of 30ns and a flat
time of 16ns as shown in Figure 4.
© 2002, RFWaves LTD.
Resonator
488MHz
SAW
RFW24 – The silicon chip (RFIC) whose specification is the ‘active’ part of the system. It performs all
the timing, amplifying, switching, transmitting and receiving functionality.
RFW488C – A 4-pin SAW correlator, realized on a Quartz substrate. This chip is completely non-
differential passive device used as a direct sequence spread spectrum spreading/de-spreading
element. It functions as a transversal 13-bit BPSK Barker code correlator (a matched filter).
RFW488R – A 1-port SAW resonator, with resonance frequency of 488MHz, serving as the system’s
CW oscillation source.
External
Inductor
23@RFW24-A1
22@RFW24-A1
DataIO
ACT
Tx/Rx
9@RFW24-A1
8@RFW24-A1
Comparator
19@RFW24-A1
16@RFW24-A1
7@RFW24-A1
Frequency Generation
Peak Detector sub-system
-
+
sub-system
488MHz
X4
Detector
'Fast' Peak
Peak
Detector
17@RFW24-A1
Capacitor
External
Figure 3: Detailed Block Diagram
1952MHz
11@RFW24-A1
SAW Amp
RSSI
RFW24-A1
20@
Matching
Network
RFW488C-A
1@
State Machine
Correlator
Matching
External
Network
SAW
RFW488C-A
RFW488C-A
3@
7@
Matching
Network
14@RFW24-A1
RFW102 ISM Transceiver Chipset
IF Amplifier
IF LNA
RF Front End
Low Noise Block
1952MHz
PA
LNA1
3@RFW24-A1
Interface
4@RFW24-A1
Antenna
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