RF3000 datasheet(13/28 Pages) RFMD

13 / 28 page

11-333

RF3000

Rev A4 031216

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.

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.

Saturated

Demodulation

(Fine Gain)

NOT Acquired

Acquired

NOT Saturated

ANTSEL = 1

Wait 15 uS

AGC Algorithm

(Course Gain)

NOT Saturated

ANTSEL = 0

Figure 9. Diversity and AGC Algorithm

RF3000 Datasheet(PDF) 13 Page - RF Micro Devices