图1. 利用直接变频收发器MAX2837构建的WiBro参考设计。
关键设计特性
- 完整的RF至基带WiBro方案
- +23dBm发射功率时，EVM为5%，满足频谱模板要求
- -79dBm接收灵敏度时，EVM为10%
- 60dB发射增益控制范围
- 94dB接收增益控制范围
- 优化于低电流模式
图2. MAX2837参考设计框图。
实验室测试
Supply Current Summary
VBATT = +3.6V, VCC = +2.85V, TA = +25°C
| Parameter | Test Conditions | Measured | Units |
| Shutdown Supply Current | MAX2837 and PA in shutdown; regulators and VCTCXO still active | 1.8 | mA |
| Idle Supply Current | MAX2837 in idle mode; PA in shutdown; regulators and VCTCXO active | 34.8 | mA |
| Transmit Supply Current | 16 QAM, ¾ FEC coding rate, POUT = +24dBm, EVM = 5% | 392.6 | mA |
| Receive Supply Current In | Low-current mode | 79 | mA |
| Receive Supply Current In | Nominal current mode | 96.2 | mA |
Receive Summary
VBATT = +3.6V, VCC = +2.85V, fRF = 2347MHz, VOUT = 90mVRMS, WiBro signal, RF specs are antenna referred, TA = +25°C
| Parameter | Test Conditions | Measured | Units | |
|---|---|---|---|---|
| DC Offset | I channels | 6.8 | mV | |
| Q channels | 4.5 | |||
| VGA Gain Step Size | 2 | dB | ||
| Receive Gain-Control Range | Max to min VGA gain | 61.7 | dB | |
| Receive LNA Gain Step | Attenuation from 0dB to -16dB | -15.9 | dB | |
| Attenuation from 0dB to -32dB | 32.1 | |||
| Gain Variation over Temperature | TA = -40°C to +85°C | LNA gain = 0dB | -5.2 | dB |
| LNA gain = -16dB | -5.3 | |||
| LNA gain = -32dB | -3 | |||
| Gain Variation over Frequency | fLO = 2304MHz to fLO = 2396MHz | 0.2 | dB | |
| Sensitivity at Low Supply Current¹ | 64 QAM, ¾ FEC coding rate, 10% EVM at sensitivity | -79.8 | dBm | |
| 16 QAM, ¾ FEC coding rate, 20% EVM at sensitivity | -90.7 | |||
| Sensitivity at Nominal Supply Current¹ | 64 QAM, ¾ FEC coding rate, 10% EVM at sensitivity | -80.4 | dBm | |
| 16 QAM, ¾ FEC coding rate, 20% EVM at sensitivity | -91.3 | |||
¹Rx EVM limits are at BB I/Q Rx outputs, and are given in the IEEE® 802.16e specification Table 338, "Receiver SNR Assumptions." The assumption is that this EVM for this modulation rate is sufficient to meet 1e-6 BER.
Transmit Summary
VBATT = +3.6V, VCC = +2.85V, fRF = 2347MHz, VIN = 90mVRMS, WiBro signal, RF specs are antenna referred, TA = +25°C
| Parameter | Test Conditions | Measured | Units |
| LO Leakage | Q = 640/352µA, I = 576/416µA | -39.6 | dBc |
| Sideband Suppression | I/Q phase = -0.5° | -52.5 | dBc |
| Transmit Power-Control Range | Including PA Gain Step | 64.5 | dB |
| Gain Variation over Frequency | fLO = 2304MHz to fLO = 2396MHz | 1.9 | dB |
| Transit EVM | 16 QAM, ¾ FEC coding rate, POUT = +24dBm, meeting spectral mask | 4.1 | % |
| Transit EVM | 16 QAM, ¾ FEC coding rate, POUT = +23dBm, meeting spectral mask | 3.5 | % |
发送链路工作特性
图3. 参考设计的输出EVM，WiBro参考设计在天线端的输出功率大于23dBm，在整个2.3GHz至2.4GHz频段范围内EVM满足规范要求，并留有5.5%的裕量。
图5. 2.35GHz，10MHz频谱模板，采用ETSI-EN-301-021F模板。该图显示WiBro参考设计在天线端输出功率为23dBm时能够满足ETSI-EN-301-021F的频谱摸板要求。
图6. 2.3GHz至2.4GHz带宽内的接收增益特性，整个频段增益变化小于0.2dB。增益控制范围为62dB (不包括LNA增益级)，步长大约为2dB。
图7. 三级LNA增益衰减在不同温度下的特性，在整个温度变化范围内，0dB和-16dB的LNA衰减的变化大约为5dB，-32dB增益衰减时的变化量约为3dB。
详细说明
WiBro参考设计包含以下元件：MAX2837直接变频收发器、Micro Mobio的MMPA372X PA、MAX8510稳压器、Murata的平衡至非平衡转换SAW带通滤波器、Hexawave的HWS466 SPDT Tx/Rx开关和Vishay的Si1563DH负载开关。
MAX2837为单芯片、宽带、直接变频收发器，适用于2.3GHz至2.7GHz的WiBro和WiMax无线收发系统。该收发器内置宽带VCO、可快速建立的Σ-Δ RF频率合成器、晶振、可编程低通滤波器、独特的消直流失调电路、I/Q误差和载波泄露检测电路，提供完备的功能支持。MAX2837在-3dBm驱动器输出时，能够提供小于1.4%的EVM，接收灵敏度优于-79dBm。配合MMPA372X PA和Murata的BPF使用时，参考设计在天线端的输出功率至少可以达到23dBm，完全满足WiBro EVM和频谱模板的要求，并留有裕量。
关联至此文章
产品
{{modalTitle}}
{{modalDescription}}
{{dropdownTitle}}
- {{defaultSelectedText}} {{#each projectNames}}
- {{name}} {{/each}} {{#if newProjectText}}
-
{{newProjectText}}
{{/if}}
{{newProjectTitle}}
{{projectNameErrorText}}
最新视频 20
