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    Audio periodicity squelch system
    3.
    发明授权
    Audio periodicity squelch system 失效
    音频周期性静噪系统

    公开(公告)号：US3904969A

    公开(公告)日：1975-09-09

    申请号：US44918474

    申请日：1974-03-07

    Applicant: MOTOROLA INC

    Inventor： EASTMOND BRUCE C

    IPC: H03G3/34 ,  H04B1/12

    CPC classification number: H03G3/342

    Abstract: Squelch circuit responsive to the periodicity of a voice signal for controlling the output of a radio receiver to provide transmission of speech and reject noise. The audio signal from the receiver is amplitude limited and the transitions in the limited wave control a bistable multivibrator having first and second out-of-phase outputs. The outputs are used to activate circuits which produce voltage samples proportional to the time period between zero crossings, with the alternate periods producing voltages across two capacitors. The difference between the successive voltage samples is derived and compared with a reference voltage to provide a control voltage. The control voltage, which is produced as long as the difference between the samples is less than the reference, is applied to a gate circuit which controls the charging of a squelch control capacitor. A control voltage which continues through a plurality of samples causes the voltage across the squelch control capacitor to raise to a level which operates a squelch switch to allow transmission of the audio signal.

    Abstract translation: 响应于语音信号的周期性的静噪电路，用于控制无线电接收机的输出以提供语音和拒绝噪声的传输。 来自接收机的音频信号受到幅度限制，并且受限波中的转换控制具有第一和第二异相输出的双稳态多谐振荡器。 输出用于激活产生与过零点之间的时间段成比例的电压采样的电路，交替周期产生两个电容器两端的电压。 导出连续电压样本之间的差异，并与参考电压进行比较以提供控制电压。 只要样本之间的差小于参考值就产生的控制电压被施加到控制静噪控制电容器的充电的门电路。 继续通过多个采样的控制电压使得静噪控制电容器两端的电压升高到操作静噪开关以允许音频信号传输的电平。

    Audio frequency squelch system
    4.
    发明授权
    Audio frequency squelch system 失效
    音频静噪系统

    公开(公告)号：US3873925A

    公开(公告)日：1975-03-25

    申请号：US44911974

    申请日：1974-03-07

    Applicant: MOTOROLA INC

    Inventor： EASTMOND BRUCE C

    IPC: H04B1/10 ,  H03G3/34

    CPC classification number: H03G3/342

    Abstract: An audio frequency squelch circuit responsive to a signal including voice signals in the presence of noise includes a limiter for receiving the signal and a monostable multivibrator coupled to the limiter and triggered by negative (or positive) transitions in the limiter output. The multivibrator produces pulses of fixed amplitude and time duration to provide an output wave having a duty cycle which varies with frequency. The pulse wave is passed through a low pass filter having a bandwidth sufficiently wide to allow coherent variations in frequency at a voice syllabic rate, and which removes random noise inputs, with opposite phases being applied to high pass filters which reject signals varying slowly in frequency. The opposite phase signals are applied separately to comparators operating against a fixed voltage reference, one of which provides an output in response to voice frequency peaks which are sufficiently above the mean frequency and the other provides an output in response to voice frequency peaks which are sufficiently below the mean frequency. The comparator outputs are applied to an OR gate which controls an integrator and timer to actuate the squelch. In an alternate embodiment, the multivibrator output is applied to the short time constant, low pass filter, as in the prior embodiment, and also to a long time constant, low pass filter, the output of which is proportional to the mean audio frequency and provides a floating voltage reference. The floating reference is shifted in positive and negative directions, and the two resulting, level shifted, floating references are each applied to a comparator, to which the output of the short time constant filter is also applied. The two comparators provide outputs in response to the voice frequency peaks which are sufficiently above and below the mean frequency, and signals varying slowly in frequency are removed by common mode rejection in the comparators. The two comparator outputs are applied to an OR gate which controls an integrator and timer to actuate the squelch, as in the prior embodiment.

    Abstract translation: 在存在噪声的情况下响应于包括语音信号的信号的音频静噪电路包括用于接收信号的限幅器和耦合到限幅器并由限幅器输出中的负（或正）转换触发的单稳态多谐振荡器。 多谐振荡器产生固定幅度和持续时间的脉冲，以提供具有随频率变化的占空比的输出波。 脉冲波通过具有足够宽的带宽的低通滤波器，以允许以语音音速进行频率的相干变化，并且其消除随机噪声输入，相反的相位被施加到高通滤波器，其抑制频率变化缓慢的信号 。 相反的相位信号分别施加于与固定参考电压相对应的比较器，其中一个输出响应于足够高于平均频率的语音频率峰值而提供输出，另一个提供响应于足够高的语音频率峰值的输出 低于平均频率。 比较器输出被施加到OR门，其控制积分器和定时器来驱动静噪。

    5.
    发明专利
    未知

    公开(公告)号：FI884273A0

    公开(公告)日：1988-09-16

    申请号：FI884273

    申请日：1988-09-16

    Applicant: MOTOROLA INC

    Inventor： EASTMOND BRUCE C

    IPC: H04B1/10 ,  H03G3/20 ,  H03G3/34 ,  H04H20/67 ,  H04B

    Abstract: An improved FM communication system is disclosed in which noise bursts and pops in the audio output of the receiver, due to weak and Rayleigh-faded signals, are minimized by selectively attenuating the audio signal in the receiver. The amount and rate of attenuation for the receiver noise reduction circuits is determined by a control signal derived form either the average discriminator noise at frequencies above 3 kHz, or from a received RF signal strength indicator, or a combination of both. The audio output is attenuated during weak signals or Rayleigh fades only when the attenuation control signal increases above a predetermined signal-to-noise ratio threshold. Also described are further improvements to noise attenuation devices used in combination with the receiver noise reduction circuits to enhance audio quality in particular applications, e.g., FM repeater systems which may incorporate multiple transmitters in a simulcast configuration.

    FM RECEIVER WITH NOISE SUPPRESSION DURING RAYLEIGH FADED RECEIVER SIGNALS
    9.
    发明专利
    FM RECEIVER WITH NOISE SUPPRESSION DURING RAYLEIGH FADED RECEIVER SIGNALS 未知

    公开(公告)号：AU6623186A

    公开(公告)日：1987-10-20

    申请号：AU6623186

    申请日：1986-11-03

    Applicant: MOTOROLA INC

    Inventor： EASTMOND BRUCE C

    IPC: H04B1/10 ,  H03G3/20 ,  H03G3/34 ,  H04H20/67

    Abstract: An improved FM communication system is disclosed in which noise bursts and pops in the audio output of the receiver, due to weak and Rayleigh-faded signals, are minimized by selectively attenuating the audio signal in the receiver. The amount and rate of attenuation for the receiver noise reduction circuits is determined by a control signal derived form either the average discriminator noise at frequencies above 3 kHz, or from a received RF signal strength indicator, or a combination of both. The audio output is attenuated during weak signals or Rayleigh fades only when the attenuation control signal increases above a predetermined signal-to-noise ratio threshold. Also described are further improvements to noise attenuation devices used in combination with the receiver noise reduction circuits to enhance audio quality in particular applications, e.g., FM repeater systems which may incorporate multiple transmitters in a simulcast configuration.

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