FCC E7E - 实用射频电路与滤波器

#E7E01🔗

Which of the following can be used to generate FM phone signals?

以下哪项可用于生成 FM 电话信号？

Balanced modulation of the audio amplifier

音频放大器的平衡调制

Reactance modulation of a local oscillator

本地振荡器的电抗调制

✓ 正确答案

Reactance modulation of the final amplifier

末级放大器的电抗调制

Balanced modulation of a local oscillator

本地振荡器的平衡调制

#E7E02🔗

What is the function of a reactance modulator?

电抗调制器的作用是什么？

Produce PM or FM signals by varying a resistance

通过改变电阻产生 PM 或 FM 信号

Produce AM signals by varying an inductance

通过改变电感产生 AM 信号

Produce AM signals by varying a resistance

通过改变电阻产生 AM 信号

Produce PM or FM signals by varying a capacitance

通过改变电容产生 PM 或 FM 信号

✓ 正确答案

#E7E03🔗

What is a frequency discriminator?

什么是鉴频器？

An FM generator circuit

FM发生器电路

A circuit for filtering closely adjacent signals

一种过滤邻近信号的电路

An automatic band-switching circuit

一种自动波段切换电路

A circuit for detecting FM signals

一种FM信号检测电路

✓ 正确答案

#E7E04🔗

What is one way to produce a single-sideband phone signal?

产生单边带电话信号的一种方法是什么？

Use a balanced modulator followed by a filter

使用平衡调制器，然后使用滤波器

✓ 正确答案

Use a reactance modulator followed by a mixer

使用电抗调制器，然后使用混频器

Use a loop modulator followed by a mixer

使用环路调制器，然后使用混频器

Use a product detector with a DSB signal

使用具有 DSB 信号的产品检测器

#E7E05🔗

What is added to an FM speech channel to boost the higher audio frequencies?

FM 语音通道中添加了什么来提升更高的音频频率？

A de-emphasis network

去加重网络

A harmonic enhancer

谐波增强器

A heterodyne enhancer

外差增强器

A pre -emphasis network

预加重网络

✓ 正确答案

#E7E06🔗

Why is de-emphasis used in FM communications receivers?

为什么在 FM 通信接收器中使用去加重？

For compatibility with transmitters using phase modulation

与使用相位调制的发射机兼容

✓ 正确答案

To reduce impulse noise reception

减少脉冲噪声接收

For higher efficiency

为了更高的效率

To remove third-order distortion products

消除三阶失真产物

#E7E07🔗

What is meant by the term “baseband” in radio communications?

无线电通信中的术语“基带”是什么意思？

The lowest frequency band that the transmitter or receiver covers

发射器或接收器覆盖的最低频段

The frequency range occupied by a message signal prior to modulation

调制前消息信号占用的频率范围

✓ 正确答案

The unmodulated bandwidth of the transmitted signal

传输信号的未调制带宽

The basic oscillator frequency in an FM transmitter that is multiplied to increase the deviation and carrier frequency

FM 发射机中的基本振荡器频率，相乘以增加偏差和载波频率

#E7E08🔗

What are the principal frequencies that appear at the output of a mixer?

混频器输出端出现的主要频率是什么？

Two and four times the input frequency

输入频率的两倍和四倍

The square root of the product of input frequencies

输入频率乘积的平方根

The two input frequencies along with their sum and difference frequencies

两个输入频率及其和频率和差频率

✓ 正确答案

1.414 and 0.707 times the input frequency

输入频率的1.414和0.707倍

#E7E09🔗

What occurs when the input signal levels to a mixer are too high?

当混音器的输入信号电平过高时会发生什么？

Spurious mixer products are generated

产生杂散混频器产物

✓ 正确答案

Mixer blanking occurs

发生混合器消隐

Automatic limiting occurs

自动限制发生

Excessive AGC voltage levels are generated

产生过高的 AGC 电压电平

#E7E10🔗

How does a diode envelope detector function?

二极管包络检波器如何工作？

By rectification and filtering of RF signals

通过对射频信号进行整流和滤波

✓ 正确答案

By breakdown of the Zener voltage

通过齐纳电压的击穿

By mixing signals with noise in the transition region of the diode

通过在二极管的过渡区域将信号与噪声混合

By sensing the change of reactance in the diode with respect to frequency

通过感测二极管电抗相对于频率的变化

#E7E11🔗

Which type of detector is used for demodulating SSB signals?

哪种类型的检波器用于解调 SSB 信号？

Discriminator

鉴别器

Phase detector

鉴相器

Product detector

产品检测仪

✓ 正确答案

Phase comparator

相位比较器

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FCC E7E - 实用射频电路与滤波器

小节 E7E：实用射频电路与滤波器