原标题：Semtech SX1231低功耗UHF RF收发器解决方案

　　Semtech 公司的SX1231是低功耗集成的UHF RF收发器, 工作频率包括433, 868 和 915 MHz无许可证的ISM频段,所有主要的RF通信参数是可编程的,大多数可动态设定. SX1231在1.2kbps是的灵敏度高达-120dBm,采用16节的FIR通路滤波器,因而有好的选择性,可编程输出,从-18dBm 到+17dBm, FSK, GFSK, MSK, GMSK 和OOK调制,主要用在自动读表, 无线传感器网络,家庭和建筑物自动化,无线告警和安全系统,工业监视和控制等.本文介绍了SX1231主要特性,方框图, 接收器和发送器方框图, 应用电路图以及+13dBm和+17dBm应用电路图, 评估板电路图和915MHz频率材料清单(BOM)与PCB布局图.

　　The SX1231 is a highly integrated RF transceiver capable of operation over a wide frequency range, including the 433, 868 and 915 MHz license-free ISM (Industry Scientific and Medical) frequency bands. Its highly integrated architecture allows for a minimum of external components whilst maintaining maximum design flexibility. All major RF communication parameters are programmable and most of them can be dynamically set. The SX1231 offers the unique advantage of programmable narrow-band and wide-band

　　communication modes without the need to modify external components. The SX1231 is optimized for low power consumption while offering high RF output power and channelized operation. TrueRF™ technology enables a lowcost external component count (elimination of the SAW filter) whilst still satisfying ETSI and FCC regulations.

　　SX1231主要特性:

　　High Sensitivity: down to -120 dBm at 1.2 kbps

　　High Selectivity: 16-tap FIR Channel Filter

　　Bullet-proof front end: IIP3 = -18 dBm, IIP2 = +35 dBm, 80 dB Blocking Immunity, no Image Frequency response

　　Low current: Rx = 16 mA, 100nA register retention

　　Programmable Pout: -18 to +17 dBm in 1dB steps

　　Constant RF performance over voltage range of chip

　　FSK Bit rates up to 300 kb/s

　　Fully integrated synthesizer with a resolution of 61 Hz

　　FSK, GFSK, MSK, GMSK and OOK modulations

　　Built-in Bit Synchronizer performing Clock Recovery

　　Incoming Sync Word Recognition

　　115 dB+ Dynamic Range RSSI

　　Automatic RF Sense with ultra-fast AFC

　　Packet engine with CRC, AES-128 encryption and 66-byte FIFO

　　Built-in temperature sensor and Low Battery indicator

　　SX1231应用:

　　Automated Meter Reading

　　Wireless Sensor Networks

　　Home and Building Automation

　　Wireless Alarm and Security Systems

　　Industrial Monitoring and Control

　　图1.SX1231简化方框图

　　图2.SX1231接收器方框图

　　图3.SX1231发送器方框图

　　图TX 匹配网络

　　The matching network is comprised of the following stages:

　　LT1, CT1: Together with both PCB and device (packaging) parasitics forms a resonant load at the required output frequency.

　　LT2, CT2: For applications that need to comply with the requirements of ETSI EN 300 220, this network forms a band stop filter resonant at the second harmonic.

　　CT3 provides a DC block.

　　CT4, CT5, LT3: Form a low-pass harmonic filter.

　　图8.LNA 匹配网络

　　SX1231评估板 915MHz材料清单(BOM):