HT82K75REW datasheet(47/103 Pages) HOLTEK

47 / 103 page

HT82M75REW/HT82K75REW

Rev. 1.00

June 11, 2010

RF Transceiver PHY Block

The key features and the block diagram of the PHY layer

in RF Transceiver are listed as below.

Operating frequency range is from 2400MHz to

2495MHz.

It uses Offset QPSK (OQPSK) modulation to transmit

data at 250k/1M bps.

Direct Sequence Spreading Spectrum (DSSS) is used

in baseband algorithm to increase the SNR.

The RF Transceiver uses a fractional-N Phase-Locked

Loop (PLL) as frequency synthesizer. Therefore, 1MHz

channel spacing is supported and any integer carrier

frequency between 2400MHz to 2495MHz can be used.

The loop filters of PLL are integrated into the RF Trans-

ceiver except one external capacitor which should be

connected between the PLL loop filter external pin and

the ground. In order to keep the PLL stable, the board

layout around the PLL loop filter external capacitor pin

should be carefully designed to avoid EMI. The recom-

mended value of this external capacitor is 47pF.

Under 1M bps turbo mode, user can use the same pro-

gram settings of MAC and all MAC functions are re-

mained the same. Compare with 250k bps mode, in 1M

bps mode, signal bandwidth is extended to 8MHz.

The packet includes a 6 bytes PHY header and a 7~63

bytes PHY payload. The 6 bytes PHY header includes 4

bytes of preamble, 1 byte of start-of-frame delimiter

(SFD) and 1 byte of payload length. Preamble and SFD

are used for receiver packet detection and synchroniza-

tion. The Frame Length field specifies the length of the

PHY payload field. The valid length can be from 7 to 63

bytes. The frame format is shown as below:

T o L o w

M A C B l o c k

T o L o w e r

M A C B l o c k

B a s e b a n d

C i r c u i t

A D C

D A C

A D C

P L L

L N A

P A

M i x e r

P o l y p h a s e

F i l t e r

L i m i t i n g

A m p l i f i e r

R F I O

PHY Block architecture

P r e a m b l e

P H Y P a y l o a d

4 b y t e s

1 b y t e

7 ~ 6 3 b y t e s

S t a r t o f F r a m e

D e l i m i t e r

F r a m e

L e n g t h

P H Y H e a d e r

PHY Layer Frame Format

HT82K75REW Datasheet(PDF) 47 Page - Holtek Semiconductor Inc

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