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| 型号： | SI4731-D50-GM |
| 厂商： | Silicon Laboratories Inc |
| 文件页数： | 21/34页 |
| 文件大小： | 0K |
| 描述： | IC RADIO RECEIVER AM/FM 20-QFN |
| 标准包装： | 490 |
| 频率： | 520kHz ~ 1.71MHz，64MHz ~ 108MHz |
| 调制或协议： | AM，FM |
| 应用： | 通用 |
| 数据接口： | PCB，表面贴装 |
| 天线连接器： | PCB，表面贴装 |
| 电源电压： | 2.7 V ~ 5.5 V |
| 工作温度： | -20°C ~ 85°C |
| 封装/外壳： | 20-UFQFN 裸露焊盘 |
| 供应商设备封装： | 20-QFN（3x3） |
| 包装： | 托盘 |
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Si4730/31-D50
4.6. Stereo Audio Processing
The output of the FM demodulator is a stereo
multiplexed (MPX) signal. The MPX standard was
developed in 1961, and is used worldwide. Today's
MPX signal format consists of left + right (L+R) audio,
left – right (L–R) audio, a 19 kHz pilot tone, and
RDS/RBDS data as shown in Figure 11 below.
4.7. Received Signal Qualifiers
The quality of a tuned signal can vary depending on
many factors including environmental conditions, time of
day, and position of the antenna. To adequately manage
the audio output and avoid unpleasant audible effects to
the end-user, the Si473x monitors and provides
indicators of the signal quality. The Si473x monitors
signal quality metrics including RSSI, SNR, and
multipath interference on FM signals. These metrics are
used to optimize audio and signal processing and are
Mono Audio
Left + Right
Stereo
Pilot
Stereo Audio
Left - Right
RDS/
RBDS
also reported to the host processor. The signal
processing algorithms can use either Silicon Labs'
optimized settings (recommended) or be customized to
modify performance.
0
15 19 23
38
53
57
4.8. De-emphasis
Frequency (kHz)
Figure 11. MPX Signal Spectrum
4.6.1. Stereo Decoder
The Si4730/31's integrated stereo decoder
automatically decodes the MPX signal using DSP
techniques. The 0 to 15 kHz (L+R) signal is the mono
output of the FM tuner. Stereo is generated from the
(L+R), (L–R), and a 19 kHz pilot tone. The pilot tone is
used as a reference to recover the (L–R) signal. Output
left and right channels are obtained by adding and
subtracting the (L+R) and (L–R) signals respectively.
The Si4731 uses frequency information from the 19 kHz
stereo pilot to recover the 57 kHz RDS/RBDS signal.
4.6.2. Stereo-Mono Blending
Adaptive noise suppression is employed to gradually
combine the stereo left and right audio channels to a
mono (L+R) audio signal as the signal quality degrades
to maintain optimum sound fidelity under varying
reception conditions. Three metrics, received signal
strength indicator (RSSI), signal-to-noise ratio (SNR),
and multipath interference, are monitored
simultaneously in forcing a blend from stereo to mono.
The metric which reflects the minimum signal quality
takes precedence and the signal is blended
appropriately.
All three metrics have programmable stereo/mono
thresholds and attack/release rates detailed in “AN332:
Si47xx Programming Guide.” If a metric falls below its
mono threshold, the signal is blended from stereo to full
mono. If all metrics are above their respective stereo
thresholds, then no action is taken to blend the signal. If
a metric falls between its mono and stereo thresholds,
then the signal is blended to the level proportional to the
metric’s value between its mono and stereo thresholds,
with an associated attack and release rate.
Pre-emphasis and de-emphasis is a technique used by
FM broadcasters to improve the signal-to-noise ratio of
FM receivers by reducing the effects of high-frequency
interference and noise. When the FM signal is
transmitted, a pre-emphasis filter is applied to
accentuate the high audio frequencies. The Si4730/31
incorporates a de-emphasis filter which attenuates high
frequencies to restore a flat frequency response. Two
time constants are used in various regions. The de-
emphasis time constant is programmable to 50 or
75 μs.
4.9. Volume Control
The audio output may be muted. Volume is adjusted
digitally by the RX_VOLUME property.
4.10. Stereo DAC
High-fidelity stereo digital-to-analog converters (DACs)
drive analog audio signals onto the LOUT and ROUT
pins. The audio output may be muted.
4.11. Soft Mute
The soft mute feature is available to attenuate the audio
outputs and minimize audible noise in very weak signal
conditions. The soft mute feature is triggered by the
SNR metric. The SNR threshold for activating soft mute
is programmable, as are soft mute attenuation levels
and attack and release rates.
Rev. 1.0
21
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| SI4731-D50-GMR | 制造商:Silicon Laboratories Inc 功能描述:ADVANCED AM/FM RDS RECEIVER FOR MOBILE DEVICES - Tape and Reel 制造商:Silicon Laboratories Inc 功能描述:IC RADIO RECEIVER AM/FM 20-QFN 制造商:Silicon Laboratories Inc 功能描述:MOBLE DEV AM/FM/RCVR RDS 3X3X0.55 20P |
| SI4731-D60-EVB | 功能描述:BOARD EVALUATION FOR SI473-D60 RoHS:是 类别:RF/IF 和 RFID >> RF 评估和开发套件，板 系列:- 标准包装:1 系列:- 类型:GPS 接收器 频率:1575MHz 适用于相关产品:- 已供物品:模块 其它名称:SER3796 |
| SI4731-D60-GM | 功能描述:IC RADIO RX AM/FM/AUX 20QFN RoHS:是 类别:RF/IF 和 RFID >> RF 接收器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS 产品变化通告:Product Discontinuation 09/Jan/2012 标准包装:50 系列:* 频率:850MHz ~ 2.175GHz 灵敏度:- 数据传输率 - 最大:- 调制或协议:- 应用:* 电流 - 接收:* 数据接口:PCB，表面贴装 存储容量:- 天线连接器:PCB，表面贴装 特点:- 电源电压:4.75 V ~ 5.25 V 工作温度:0°C ~ 85°C 封装/外壳:40-WFQFN 裸露焊盘 供应商设备封装:40-TQFN-EP（6x6） 包装:托盘 |
| Si4731-D60-GMR | 功能描述:射频接收器 BRDCAST AM/FM/AUXIN RADIO RECEIVER/RBDS RoHS:否 制造商:Skyworks Solutions, Inc. 类型:GPS Receiver 封装 / 箱体:QFN-24 工作频率:4.092 MHz 工作电源电压:3.3 V 封装:Reel |
| SI4731-D60-GU | 功能描述:IC RADIO RX AM/FM/AUX 24SSOP RoHS:是 类别:RF/IF 和 RFID >> RF 接收器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS 产品变化通告:Product Discontinuation 09/Jan/2012 标准包装:50 系列:* 频率:850MHz ~ 2.175GHz 灵敏度:- 数据传输率 - 最大:- 调制或协议:- 应用:* 电流 - 接收:* 数据接口:PCB，表面贴装 存储容量:- 天线连接器:PCB，表面贴装 特点:- 电源电压:4.75 V ~ 5.25 V 工作温度:0°C ~ 85°C 封装/外壳:40-WFQFN 裸露焊盘 供应商设备封装:40-TQFN-EP（6x6） 包装:托盘 |
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