BCM88335 Data Sheet
WLAN Radio Subsystem
Section 11: WLAN Radio Subsystem
The BCM88335 includes an integrated dual-band WLAN RF transceiver that has been optimized for use in
2.4 GHz and 5 GHz Wireless LAN systems. It has been designed to provide low-power, low-cost, and robust
communications for applications operating in the globally available 2.4 GHz unlicensed ISM or 5 GHz U-NII
bands. The transmit and receive sections include all on-chip filtering, mixing, and gain control functions.
Ten RF control signals are available to drive external RF switches and support optional external power amplifiers
and low-noise amplifiers for each band. See the reference board schematics for further details.
A block diagram of the radio subsystem is shown in Figure 29 on page 73. Note that integrated on-chip baluns
(not shown) convert the fully differential transmit and receive paths to single-ended signal pins.
Receiver Path
The BCM88335 has a wide dynamic range, direct conversion receiver that employs high order on-chip channel
filtering to ensure reliable operation in the noisy 2.4 GHz ISM band or the entire 5 GHz U-NII band. An on-chip
low-noise amplifier (LNA) in the 2.4 GHz path is shared between the Bluetooth and WLAN receivers, while the
5 GHz receive path has a dedicated on-chip LNA. Control signals are available that can support the use of
optional LNAs for each band, which can increase the receive sensitivity by several dB.
Transmit Path
Baseband data is modulated and upconverted to the 2.4 GHz ISM or 5-GHz U-NII bands, respectively. Linear
on-chip power amplifiers are included, which are capable of delivering high output powers while meeting
IEEE 802.11ac and IEEE 802.11a/b/g/n specifications without the need for external PAs. When using the
internal PAs, closed-loop output power control is completely integrated. As an option, external PAs can be used
for even higher output power, in which case the closed-loop output power control is provided by means of a-
band and g-band TSSI inputs from external power detectors.
Calibration
The BCM88335 features dynamic and automatic on-chip calibration to continually compensate for temperature
and process variations across components. These calibration routines are performed periodically in the course
of normal radio operation. Examples of some of the automatic calibration algorithms are baseband filter
calibration for optimum transmit and receive performance, and LOFT calibration for carrier leakage reduction.
In addition, I/Q Calibration, R Calibration, and VCO Calibration are performed on-chip. No per-board calibration
is required in manufacturing test, which helps to minimize the test time and cost in large volume production.
Broadcom®
September 23, 2015 • 88335-DS100-R
Page 72
BROADCOM CONFIDENTIAL
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