图1. 参考设计电路板显示了802.11b/g RF前端模块中的MAX2830

关键设计特性

• 级联接收噪声系数为6dB
• 10kHz偏移时，具有-95dBc/Hz的低相位噪声
• 802.11g 54Mbps OFDM信号下，接收灵敏度为-74.5dBm时的Rx EVM < 9%
• 接收增益控制范围为95dB (32dB RF和63dB BB VGA)
• 以15dBm输出功率传输802.11g 54Mbps OFDM信号时，Tx EVM < 5.6%
• 发送增益控制范围为25dB
• 支持满量程802.11b/g数据输率
• 小尺寸11mm x 16mm
• 低BOM成本

图2. 802.11b/g RF模块方框图

实验室测试

直流特性
V_BATT = +3.3V, V_CC = +2.85V, T_A = +25°C

Parameter	Test Condition	Meas.	Unit
Shutdown Supply Current		10	µA
Standby Supply Current	PLL, VCO, LO Generator ON	28	mA
Receive Supply Current		65	mA
Transmit Supply Current	POUT = 15dBm	289	mA

接收概述
V_BATT = +3.3V, V_CC = +2.85V, f_RF = 2437MHz, RF输入 = 802.11a, 64QAM, 54MBps (天线端), V_OUT = 112mV_RMS (RXI和RXQ基带输出), RXHP = 0, T_A = +25°C

Parameter	Test Condition		Meas.	Unit
Frequency Range			2.4 to 2.5	GHz
Receive EVM	Max Gain, VGA adjusted for VOUT = 112mVRMS, PIN = -65dBm		3.9	%
	Mid Gain, VGA adjusted for VOUT = 112mVRMS, PIN = -45dBm		2.5
	Min Gain, VGA adjusted for VOUT = 112mVRMS, PIN = -10dBm		2.7
Sensitivity	Receive EVM = 9%	Antenna 1	-73	dBm
		Antenna 2	-74.5

发送概述
V_BATT = +3.3V, V_CC = +2.85V, f_RF = 2437MHz, 基带输入 = 110mV_RMS, 802.11a, 64QAM, 54MBps, 在天线1处测量Tx输出, RXHP = 0, T_A = +25°C

Parameter	Test Condition		Meas.	Unit
Maximum Transmit Output	Tx VGA adjusted for EVM = 5.6%, Tx VGA = -4dB		15	dBm
ACPR	Tx VGA set for EVM < 5.6%, channel BW = 20MHz	fOFFSET = 20MHz	36	dBc
		fOFFSET = 40MHz	55
		fOFFSET = 60MHz	60

图3. 参考设计的相位噪声图

详细说明

MAX2830是单芯片、单频、Dual Mode™直接变频收发器，设计用于2.4GHz 802.11b/g (OFDM和CCK) WLAN应用。器件集成了实现RF收发器功能所需的全部电路：PA、T/R开关、天线切换开关、LNA、50Ω匹配元件、Σ-Δ分数合成器、晶体振荡器以及独特的I/Q幅度和相位误差校准电路。器件为接收器和发送器集成了完整的片上滤波器，从而省去了外部SAW滤波器。基带Tx和Rx滤波器经过优化，能够满足802.11g IEEE标准。仅需一个额外RF滤波器和少量无源器件即可构建完整的802.11b/g WLAN RF前端方案，以较小的外型尺寸和较低的成本，提供优异的性能。

应用笔记链接
应用笔记3630： "WIFI收发器的电源和接地设计" 

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