RF3000 Просмотр технического описания (PDF) - RF Micro Devices

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RF3000

SPREAD-SPECTRUM BASEBAND MODEM

RF Micro Devices 

RF3000

Block Diagram Breakout

The following sections describe each of the blocks, as indicated in the block diagram, that comprise the RF3000.

Modulator

PSK Modes

The RF3000 uses a proprietary architecture that allows the modulation of PSK signals by simply reprogramming the part

via the control port. The transmitted data stream is first spread and the resulting data stream is modulated.

CCK Mode

IEEE802.11b Preamble/Header Creation and Assembly

The RF3000 provides circuitry to generate and assemble a preamble and header as specified in the IEEE802.11b spec-

ification. The short preamble option for 2Mbps, 5.5Mbps and 11Mbps, as specified in IEEE802.11b, is selectable in the

mode control register. The RF3000 will transmit these fields along with a protective CRC-16 for error detection. For other

protocols, the preamble/header circuitry is disabled, and packet structures should be generated externally.

Demodulator

PSK Modes

The RF3000 uses a proprietary architecture that allows the demodulation of PSK signals by simply reprogramming the

part via the control port. The received signal is first de-spread and the PSK signal is recovered.

CCK Mode

In order to perform CCK demodulation, circuitry is provided to pass the output of the A/D converters to a fast Walsh

transform (FWT). The output of the FWT is then passed to decision circuitry to determine the received signal.

IEEE802.11b Preamble/Header Detection and Extraction

Circuitry is provided to search the incoming data for start frame delimiter (SFD) and to obtain length field information as

well as modulation type. In 802.11 modes, this circuitry is always active since the preamble and header tells the PHY

which modulation type the data packet is using. The RF3000 will also check the preamble/header field for errors by

checking the CRC-16 field for errors.

Data Converters

The RF3000 contains all A/D converters and D/A converters required to implement a transceiver.

A/D Converters

I/Q A/Ds - These are 4-bit analog-to-digital converters used to sample the data according to the mode of the RF3000.

D/A Converters

Four (4) digital-to-analog converters are present for transmitter VGC, receiver VGC, I Out, and Q Out.

RSSI, CCA and AGC

Scramblers

Scramblers for whitening the spectrum are provided, as specified in IEEE802.11b.

SCRAMBLER NOTE: The data scrambler defined by IEEE802.11b has a probability of 1/128, to lock up scrambling

when random data is followed by a repetitive pattern. The patterns identified are: all 0's; all 1’s; repetitive 01's; repeated

0011's; and, repeated 000111's. Once the pattern ceases the scrambler will resume its normal operation.

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Rev A4 031216

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