FCC E8D - 信号处理与发射

#E8D01🔗

Why are received spread spectrum signals resistant to interference?

为什么接收到的扩频信号具有抗干扰性？

Signals not using the spread spectrum algorithm are suppressed in the receiver

不使用扩频算法的信号在接收器中被抑制

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The high power used by a spread spectrum transmitter keeps its signal from being easily overpowered

扩频发射机使用的高功率可防止其信号被轻易压倒

Built-in error correction codes minimize interference

内置纠错码最大限度地减少干扰

If the receiver detects interference, it will signal the transmitter to change frequencies

如果接收器检测到干扰，它会向发射器发出信号以改变频率

#E8D02🔗

What spread spectrum communications technique uses a high-speed binary bit stream to shift the phase of an RF carrier?

什么扩频通信技术使用高速二进制比特流来移动射频载波的相位？

Frequency hopping

跳频

Direct sequence

直接序列

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Binary phase-shift keying

二进制相移键控

Phase compandored spread spectrum

相位压扩扩频

#E8D03🔗

Which describes spread spectrum frequency hopping?

哪项描述了扩频跳频？

If interference is detected by the receiver, it will signal the transmitter to change frequencies

如果接收器检测到干扰，它会向发射器发出信号以改变频率

RF signals are clipped to generate a wide band of harmonics which provides redundancy to correct errors

RF 信号被削波以生成宽带谐波，从而提供冗余以纠正错误

A binary bit stream is used to shift the phase of an RF carrier very rapidly in a pseudorandom sequence

二进制比特流用于以伪随机序列快速移动射频载波的相位

Rapidly varying the frequency of a transmitted signal according to a pseudorandom sequence

根据伪随机序列快速改变传输信号的频率

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#E8D04🔗

What is the primary effect of extremely short rise or fall time on a CW signal?

极短的上升或下降时间对 CW 信号的主要影响是什么？

More difficult to copy

更难复制

The generation of RF harmonics

射频谐波的产生

The generation of key clicks

按键点击的生成

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More difficult to tune

更难调

#E8D05🔗

What is the most common method of reducing key clicks?

减少按键点击的最常见方法是什么？

Increase keying waveform rise and fall times

增加键控波形上升和下降时间

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Insert low-pass filters at the transmitter output

在发射机输出处插入低通滤波器

Reduce keying waveform rise and fall times

减少键控波形上升和下降时间

Insert high-pass filters at the transmitter output

在发射器输出处插入高通滤波器

#E8D06🔗

What is the advantage of including parity bits in ASCII characters?

在 ASCII 字符中包含奇偶校验位有什么好处？

Faster transmission rate

更快的传输速率

Signal-to-noise ratio is improved

信噪比提高

A larger character set is available

有更大的字符集可用

Some types of errors can be detected

可以检测到某些类型的错误

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#E8D07🔗

What is a common cause of overmodulation of AFSK signals?

AFSK 信号过调制的常见原因是什么？

Excessive numbers of retries

重试次数过多

Excessive frequency deviation

频率偏差过大

Bit errors in the modem

调制解调器中的位错误

Excessive transmit audio levels

传输音频电平过高

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#E8D08🔗

What parameter evaluates distortion of an AFSK signal caused by excessive input audio levels?

什么参数可以评估由于输入音频电平过高而导致的 AFSK 信号失真？

Signal-to-noise ratio

信噪比

Baud error rate

波特率误码率

Repeat Request Rate (RRR)

重复请求率 (RRR)

Intermodulation Distortion ( IMD )

互调失真 (IMD)

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#E8D09🔗

What is considered an acceptable maximum IMD level for an idling PSK signal?

对于空闲 PSK 信号，可接受的最大 IMD 电平是多少？

+5 dB

+5分贝

+10 dB

+10分贝

+15 dB

+15分贝

- 30 dB

- 30分贝

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#E8D10🔗

What are some of the differences between the Baudot digital code and ASCII?

Baudot 数字代码和 ASCII 之间有哪些区别？

Baudot uses 4 data bits per character, ASCII uses 7 or 8; Baudot uses 1 character as a letters/figures shift code, ASCII has no letters/figures code

Baudot 每个字符使用 4 个数据位，ASCII 使用 7 或 8 个数据位； Baudot使用1个字符作为字母/数字移位码，ASCII没有字母/数字代码

Baudot uses 5 data bits per character, ASCII uses 7 or 8; Baudot uses 2 characters as letters/figures shift codes, ASCII has no letters/figures shift code

Baudot 每个字符使用 5 个数据位，ASCII 使用 7 或 8 个数据位； Baudot使用2个字符作为字母/数字移位码，ASCII没有字母/数字移位码

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Baudot uses 6 data bits per character, ASCII uses 7 or 8; Baudot has no letters/figures shift code, ASCII uses 2 letters/figures shift codes

Baudot 每个字符使用 6 个数据位，ASCII 使用 7 或 8 个数据位； Baudot没有字母/数字移位码，ASCII使用2个字母/数字移位码

Baudot uses 7 data bits per character, ASCII uses 8; Baudot has no letters/figures shift code, ASCII uses 2 letters/figures shift codes

Baudot 每个字符使用 7 个数据位，ASCII 使用 8 个； Baudot没有字母/数字移位码，ASCII使用2个字母/数字移位码

#E8D11🔗

What is one advantage of using ASCII code for data communications?

使用 ASCII 代码进行数据通信的优点是什么？

It includes built-in error correction features

它包括内置纠错功能

It contains fewer information bits per character than any other code

它每个字符包含的信息位比任何其他代码都少

It is possible to transmit both uppercase and lowercase text

可以传输大写和小写文本

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It uses one character as a shift code to send numeric and special characters

它使用一个字符作为班次代码来发送数字和特殊字符

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FCC E8D - 信号处理与发射

小节 E8D：信号处理与发射