h******v
发帖数: 30 | 1 示波器灵敏度大约在mV/格。频谱仪幅度范围-100dbm~+13dbm, 即大约2.24uV~1V。示波
器频谱仪灵敏度差距如此大有何技术上的原因? 示波器灵敏度做到uV/格很困难吗? 多几
级前置放大器行吗? 我有一台50MHz示波器, 灵敏度2mV/格, 打算测一0.1mV的信号(不超
过30MHz)。我的方案是用一增益带宽积1.5GHz的高速运放自制一个放大40倍的前放,加到
信号源和示波器之间。可行吗? | s**g
发帖数: 66 | 2 Sensitivity is determined by system noise, i.e. noise spectrum density
integrated over noise bandwidth.
Oscilloscope is a broadband system,500MHz in your case; while spectrum
analyzer is a narrowband system, realized by mixer + high Q filter (BPF),
resolution bw (noise bandwidth) typically between 100Hz and 1MHz. Although
the two systems may have comparable noise spectrum density by design, the
rms noise you mentioned above could be significantly different due to the
noise bw.
This difference co | s****y
发帖数: 104 | 3 great answer, very helpful.
【在 s**g 的大作中提到】
: Sensitivity is determined by system noise, i.e. noise spectrum density
: integrated over noise bandwidth.
: Oscilloscope is a broadband system,500MHz in your case; while spectrum
: analyzer is a narrowband system, realized by mixer + high Q filter (BPF),
: resolution bw (noise bandwidth) typically between 100Hz and 1MHz. Although
: the two systems may have comparable noise spectrum density by design, the
: rms noise you mentioned above could be significantly different due to the
: noise bw.
: This difference co
| h******v
发帖数: 30 | 4 多谢苏门兄指教。我很想知道你所用的16 bits高速ADC的型号。Jim Williams文章中将
几路LNA并联使用, 是否就相当于求平均?
我其实想确定一载频不超过30 MHz, 载波幅度约0.1 mV的语音调幅信号载频的实际值(当
然如果有频谱仪就很简单了)。我手头只有一实时采样
率达1G Sa/s的数字存储示波器, 带宽50 MHz, 带FFT及求平均功能, 垂直分辨率8 bits
, 垂直灵敏度2mv/格。1.5GHz LNA其Input Voltage
Noise为4 nV/Hz^(1/2) (在f=1MHz测得的结果), 以30 MHz的信号而言, 输入噪声为 4*
(30*1000000)^(1/2) = 24 uV, 不超过0.1 mV。如果使
用求平均及FFT的功能, 是否应能测出该语音调幅信号载频频率? 这FFT功能是否可理解
为连续可调的窄带滤波器?
【在 s**g 的大作中提到】
: Sensitivity is determined by system noise, i.e. noise spectrum density
: integrated over noise bandwidth.
: Oscilloscope is a broadband system,500MHz in your case; while spectrum
: analyzer is a narrowband system, realized by mixer + high Q filter (BPF),
: resolution bw (noise bandwidth) typically between 100Hz and 1MHz. Although
: the two systems may have comparable noise spectrum density by design, the
: rms noise you mentioned above could be significantly different due to the
: noise bw.
: This difference co
| h******v
发帖数: 30 | 5 如果用手机接收电路中LNA所用的LDO电源供电, 电源纹波造成的噪声应该较为理想.
(当
bits
4*
【在 h******v 的大作中提到】
: 多谢苏门兄指教。我很想知道你所用的16 bits高速ADC的型号。Jim Williams文章中将
: 几路LNA并联使用, 是否就相当于求平均?
: 我其实想确定一载频不超过30 MHz, 载波幅度约0.1 mV的语音调幅信号载频的实际值(当
: 然如果有频谱仪就很简单了)。我手头只有一实时采样
: 率达1G Sa/s的数字存储示波器, 带宽50 MHz, 带FFT及求平均功能, 垂直分辨率8 bits
: , 垂直灵敏度2mv/格。1.5GHz LNA其Input Voltage
: Noise为4 nV/Hz^(1/2) (在f=1MHz测得的结果), 以30 MHz的信号而言, 输入噪声为 4*
: (30*1000000)^(1/2) = 24 uV, 不超过0.1 mV。如果使
: 用求平均及FFT的功能, 是否应能测出该语音调幅信号载频频率? 这FFT功能是否可理解
: 为连续可调的窄带滤波器?
| s**g
发帖数: 66 | 6 You can find 16bit high speed ADC from ADI or TI or LTC. Normally these ADCs
require differential input and their input common mode range is not very
wide. Therefore you may consider adding a single-ended to differential
converter + common mode voltage shifter+buffer, i.e. ADC driver. Major ADC
providers also offer opamp based drivers. LTC Driver+ADC combo module comes
in handy. You can build your own scope or spectrum analyzer based on it. An
interface ckt is necessary - you may ask for their e
【在 h******v 的大作中提到】
: 多谢苏门兄指教。我很想知道你所用的16 bits高速ADC的型号。Jim Williams文章中将
: 几路LNA并联使用, 是否就相当于求平均?
: 我其实想确定一载频不超过30 MHz, 载波幅度约0.1 mV的语音调幅信号载频的实际值(当
: 然如果有频谱仪就很简单了)。我手头只有一实时采样
: 率达1G Sa/s的数字存储示波器, 带宽50 MHz, 带FFT及求平均功能, 垂直分辨率8 bits
: , 垂直灵敏度2mv/格。1.5GHz LNA其Input Voltage
: Noise为4 nV/Hz^(1/2) (在f=1MHz测得的结果), 以30 MHz的信号而言, 输入噪声为 4*
: (30*1000000)^(1/2) = 24 uV, 不超过0.1 mV。如果使
: 用求平均及FFT的功能, 是否应能测出该语音调幅信号载频频率? 这FFT功能是否可理解
: 为连续可调的窄带滤波器?
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