RF3000PCBA RFMD [RF Micro Devices], RF3000PCBA Datasheet - Page 13

• Manufacturer Part Number: RF3000PCBA
• Description: SPREAD-SPECTRUM BASEBAND MODEM
• Manufacturer: RFMD [RF Micro Devices]

RF3000
IEEE802.11b Receive Mode
The RF3000 receiver has an interface similar to the transmit port, and provides link support data through the control port.
The user drives RX PE High to enable the receiver circuitry. The RF3000 then begins to watch the incoming data stream
for a valid Barker code PN sequence.
The RF3000 contains logic to perform AGC when used in conjunction with the RF2948 and RF2494 as in the RF031X
reference designs for IEEE802.11b. The following sections will explain the method of AGC and the calibration hooks that
exist inside the RF3000 to compensate for manufacturing tolerances in total system gain of an IEEE802.11b radio.
Diversity
The RF3000 makes diversity decisions every 1mS while looking for A/D saturation according to the state machine in Fig-
ure 9.
NOT Saturated
ANTSEL = 0
ANTSEL = 1
NOT Saturated
Saturated
Saturated
AGC Algorithm
NOT Acquired
(Course Gain)
Wait 15 uS
Acquired
Demodulation
(Fine Gain)
Figure 9. Diversity and AGC Algorithm
AGC Algorithm
The RF3000 AGC algorithm is implemented to automatically control both the RXVGC of the RF2948 and the LNAGS pin
of the RF2494. The RF3000 is programmed to search the possible gain settings of LNAGS and RXVGC in a binary fash-
ion to quickly determine the final gain setting needed to optimize the inputs to the A/D converters for demodulation. The
AGC algorithm is completely controlled by detection of saturation of the A/D converters.
Rev A4 031216
11-333