JPS6062712A - Noise blanker circuit - Google Patents

Abstract

PURPOSE:To decrease a noise pulse of a large amplitude at a noise amplifier stage from being detoured to signal circuits after a noise gate by providing the 2nd AGC which decreases an output of the noise pulse having an amplitude of a set value or over. CONSTITUTION:The noise gate 2 provided at a signal passing stage of a radio receiver is controlled by a noise blanker circuit so as to eliminate a pulse noise mixed in a reception signal. A noise amplifier stage 5B of the noise blanker circuit is controlled by the 2nd AGC9 of a type decreasing an output of the noise pulse of the amplitude of the set value or over in addition to the 1st AGC7 to make a noise signal component output constant thereby uniforming the noise pulse output and also preventing generation of a noise pulse with a large amplitude to the noise amplifier stage 5B and succeeding stages.

Description

Detailed Description of the Invention The present invention controls the noise f-) provided in the signal passing stage (mainly the first intermediate frequency stage) of a radio receiver to remove noise noise mixed in the received signal. In the desired noise blanker circuit, the large-amplitude noise pulses amplified by the noise amplification stage will inject into the signal circuit after the noise dart, thereby degrading the performance as a noise blanker. The goal is to improve.

Noise blanker circuits are commonly used in high-sensitivity radio receivers, and are particularly effective at removing pulse noise.Recently, similar circuits have been used in the AF stage of FM receivers. However, here, we will refer to the circuit that originally removes pulse noise in the front stage, and an example of its general configuration is shown in FIG. It is desirable to remove unnecessary components other than the signal in the front stage as much as possible.The first reason is that the more circuits (especially active circuits) are stacked, and the more the amplitude is amplified, the more unnecessary components such as adjacent signals and noise will be removed from the received signal. Separation becomes impossible due to cross-modulation and intermodulation between the two components.Secondly, the elapsed time of the Norse wave increases as it passes through a filter with a narrow band, making removal by blanking difficult. There is. Therefore, basically, as shown in the circuit configuration example in Figure 1, the noise (r-) is placed at the front end of the intermediate frequency stage, at the output of the first mixer, and the noise is branched from the input side of the dart. The noise/noise obtained by rectifying the noise through the amplification stage is used for waveform shaping and other operations in the dart control section (in cases where the pulse is simply amplified to the polarity and level required for control, and when controlled with a Schmitt trigger, etc.) ), and during the period when the noise noculus passes through the dirt, the dirt is closed to prevent the noise noculus from passing through. ff-) After passing through, adjacent signals are removed through an IF filter with as narrow a band as possible, which is necessary for signal passage. The main purpose of the IF filter before the gate is to provide a slight time delay to the signal circuit to match the timing with the dart control signal.
In order to reduce the blunting of the pulse waveform, the bandwidth is set to be several times or more that of the main filter in the subsequent stage.

When the noise blanker is placed in the front stage of the IF in this way, the signal level is on the order of several tens of μV to mV.

The noise pulses to be removed are those whose peak value is several times that of the signal or more, but the noise amplification stage that amplifies this to the level of about 1V required for noise rectification is a thousand or several thousand times higher. It is necessary to increase the amplification level, especially when a strong noise noise is input, the output of the noise amplification stage is
I'm excited to reach even more than OV. Such high-level noise tends to be transmitted to other circuits, and if it enters after the noise dirt, it will destroy the effect of the noise blanker, so the noise amplification/rectification section must be strictly shielded. Also, be careful not to get close to dirt or IF circuits in terms of layout.
You will be subject to restrictions such as having to do the following.

Figure 2 is a diagram of a conventional circuit example of a noise blanker, in which 1 is a wideband IF filter, 2 is a noise dirt, 3 is a narrowband IF filter, and 4 is an IP amplification stage. The configuration is similar to that of . Also, 5A is a noise amplification stage, and 6A is a noise amplification stage.
is a rectifier; 7 is an AGC voltage amplifier for amplifying the DC component of the rectified output and applying AGC to the noise amplification stage;
(5) Similar to AGC in general AM receivers, an AGC control voltage proportional to the average amplitude value is applied to the noise amplification stage, regardless of the amplitude modulation degree of the signal.
The configuration is such that the signal output is as constant as possible, and the threshold level is set near the maximum value of the signal output. There is. An example of the operation of this circuit is illustrated in FIG. In the figure, ■ is the IF multiplied signal input to the noise amplifier 5A, and ■ is the AGC (1) that operates with the rectified average value of the input signal, which applies the AGC voltage sufficiently amplified by the AGO voltage amplifier 7 to the noise amplification stage 5A. Therefore, large amplitude signals are suppressed and their outputs are made uniform as shown in (a) to (b).

On the other hand, noise noise has a very short duration, so
Even if the amplitude is several times as large as the signal, the average value will be extremely small, so it will hardly appear in the AGC (1) output in (2), so the noise noise will be fully amplified and will be transmitted to the rear stage of the noise amplification stage. A large-amplitude noise appears at the noise rectification output section. The output of the dart control section 8A is ■. In this way, AGC is an average value type or a function close to an average value type (6). Therefore, for very short-duration inputs such as noise pulses, it has almost no full (AGC effect), so large amplitude (noise pulses are repeated in stages after the noise date)
The filling effect is the same as that described with respect to FIG.

The present invention has been made in order to deal with such problems, and the present invention has been made to address such problems.
Noise and 7 Lus are separated by multiplying the noise amplification stage of the noise blanker circuit, which controls dirt and eliminates 9 Lus noise mixed in the received signal, by applying AGC that keeps the signal output constant. In addition to the first AGC that keeps the output of the signal constant, the circuit that controls the noise and noise r-t controls the circuit that reduces the output of noise noise having an amplitude greater than a set value. By providing No. 2 AGC, large-amplitude noise in the noise amplification stage and pulses can be reduced to noise. -) This is a noise blanker circuit designed to reduce the noise that goes around to subsequent signal circuits.

FIG. 3 is a basic circuit block diagram explaining the present invention in detail, in which 1 is a wideband IF filter, 2 is a noise r-)
, 3 is a narrow band IF filter, and 4 is an IF amplification stage, which has the same structure as in FIGS. 1 and 2. Further, 5B is a noise amplification stage, 6 is a rectifier, 7 is an AGC voltage amplifier for amplifying the DC component of the rectified output and multiplied by the first AGC (1) on the noise amplification stage 5B, and 8B is an ff-) control section. There it is,
At the same time, the noise pulse detected and rectified in step 6 is subjected to waveform shaping and other operations necessary for noise/dart control.
By obtaining the output of the second AGO (2) that operates with a noise pulse of a certain amplitude or more, and adding this to the second AGC of the noise amplification stage 5BK through the AGC voltage amplifier 9, it is possible to generate a large output after the noise amplification stage. This configuration prevents amplitude noise from occurring. In the figure, AGC (1)
and AGC(2) are added separately to the noise amplification stage 5B, but both AGCs may be combined and added to one location. An example of the operation of this circuit is illustrated in FIG. 4(B). In the figure, the noise amplification stage 5B is shown in Fig. 4 (B).
When inputting an IF multiplied signal containing noise and noise as shown in ■, the average value type AGC (1) becomes as shown in ■, and AGC (2) with noise and noise separated by r-to control unit 8B.
is ■. The noise amplification stage has signals AGC (1) and No.
? As a result of the operation of the Lux AGC (2), the noise and Lux output are also made uniform as shown in (2).

Claim 2 of the present invention presents a configuration of an AGC circuit that is effective in implementing the present invention. That is, the fifth
In the figure, the rectified output ■ of the noise amplification stage is added to the pace of the transistor Ql (AGC) through an integral time constant circuit consisting of a resistor R and a capacitor C, and the change in the collector potential ■ is supplied as the AGC of the noise amplification stage. Is the configuration and Emi, Rini/iode D1 connected in series? −) Add the rectified output ■ of the noise amplification stage to the pace of the control transistor Qt, and
By configuring the collector of l and the collector of Ql to be connected by diode D2, 9.1'-) control pulse ■
This is a noise blanker circuit characterized by obtaining an AGC voltage ■ that operates on both signals and noise pulses at the collector of the AGC amplification transistor Ql when 0 occurs. 9) In the constant circuit, for example, if R1 = 10Ω, C = 10 μF, and time constant = 0.1 seconds, then #'! Since the noise of 100 Hz or more is averaged, the output amplified by Ql becomes as shown in FIG. 6, and noise noise with high frequency components is removed. A rectified output is applied to the dirt control transistor Q through a resistor R2, but the initial voltage of the diode D1 (silicon) connected in series with its emitter is
(For a diode, it is around 0.6V) is added as a reverse bias, so when combined with the initial value of Qz pace bias (also around 0.6V), if the input is about 1.2V or less, Q
Since l is not conductive, the peak of the signal output in ■ is 1.2
If it is suppressed below v by AGC (1), Ql will not operate, and the output of Q3 will appear only due to noise noise with a larger amplitude. For the resistor R2, a small resistor of Ω or less is used to prevent parasitic vibration, but if the rectified output (2) is too large, a resistor value necessary for adjusting the input level may be adopted. When Ql is off, noise -f flows from the power supply Vcc through the resistor FL5.
A conductive current flows through the Dart Da (10) iode in the -) section as shown by the broken arrow. (
The noise/dirt section in the figure is shown in principle with the simplest configuration.) When a noise pulse is input to Q2 and Qx becomes conductive, the voltage drop caused by resistor R11 causes the collector potential to drop as shown in ■.During that period, the dart diode becomes non-conductive and acts as a noise dart. There is. In the present invention, when utilizing the voltage change (2) for noise noise AGC, a diode D! is connected between the collectors of Ql and Q3.
The feature is that it is configured to connect with. D! The voltage change on the Ql side is applied to the Ql side, but the polarity is such that the voltage change on the Ql side does not affect the Q3 side, and the potential difference between the two circuits V
To keep D reasonable, a Zener diode, diode forward voltage drop, and the like are used in series. As a result of the AGC voltage O synthesized in this way being applied to the noise amplification stage, the input pulses with large amplitudes as shown in the top row of Figure 6 are also suppressed and are made uniform as shown in ■. . In Figure 5, QtsQs is originally a circuit required for each application, and by simply adding D8 to it, not only can the desired AGC operation be obtained, but also the AGC
There is an advantage that there is no need to consider mutual interference in a configuration in which (1) and AGC (2) are added separately to the noise amplification stage.

Claim 3 of the present invention presents another configuration example of the AGC circuit that is effective in implementing the present invention. That is, in Fig. 7, the rectified output ■ of the noise amplification stage is connected to the resistor R1.
AGC through an integral type time constant circuit with a large capacity C)
The time constant resistor R1 of the integral time constant circuit of the first AGC amplifier Q1 is configured to supply the pace of the transistor Q1 as well as the change in its collector potential as the AGC of the noise amplification stage.
By connecting a diode PDl in parallel with the input signal, this noise blanker circuit can be used as a second AGC that operates with a noise pulse having a large amplitude equal to or higher than the initial conduction voltage of the diode. .

The operation of the first AGC, which has an integral time constant circuit including a resistor R1 and a capacitor C on the input side, is as described in detail in the second claim. In the present invention, the simple configuration is that the diode D3 is connected in parallel with the time constant resistor R1 (J), and the collector of the AGC amplifier Q1 is connected to the first AGC (1) that operates with the average value of the signal and the signal that has a large amplitude. It is possible to obtain a composite AGC and voltage of the second AGC (2) that operates only with noise pulses.

D3 used here can be an ordinary small signal diode,
As is well known, silicon diodes have extremely low forward resistance, but they hardly conduct (equivalent to extremely high resistance) below the initial conduction voltage (o, about 6 V), so a small amplitude of 0.6 V or less peaks. D for input
You can think of it as a circuit without 3. Therefore, AGC (1) is sufficiently effective and the rectified output of the signal is adjusted to the initial bias of Ql of 0.6V.
If the voltage is suppressed to 1 or 2 V or less, the operation for AGCQ) will be performed normally. Large amplitude inputs such as noise and i4 pulses pass through D3 and are added to the base of Qs, but if the capacitance of C is large, the rise of the waveform will be delayed, so insert a small resistor R in series with C. There is. In this case, the value of R is within the h range (13) that does not significantly affect the time constant, and is often selected within 1/10 or less of R1. In such a circuit configuration, the operation of Ql is such that the collector potential of Ql becomes the AGC voltage ■ as shown in Figure 8, so the large-amplitude noise in the noise amplification stage can be easily detected without any other changes or processing. The goal of oppression can be achieved. Note that in FIG. 7, Ql is dedicated to controlling noise/ff-), so there is an advantage that there is a large degree of freedom in the configuration of the r-) control circuit.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a noise blanker in a radio receiver, Fig. 2 is a block diagram of a configuration example of a noise blanker circuit, Fig. 3 is a block diagram showing the configuration of a noise blanker circuit of the present invention, and Fig. 4 The figures are operation waveform diagrams of each part of the circuit in Figures 2 and 3, Figure 5 is an example of an AGC circuit applied to the present invention, Figure 6 is an operation waveform of each part of the circuit in Figure 5, and Figure 7 is a diagram of the present invention. Another example of an AGC circuit applied to the circuit, Fig. 8 shows the operating waveforms of each part of the circuit shown in Fig. 7. 1, 3... IF filter, 2... Noise gate,
(14) 5A/5B... Noise amplification stage, 6... Rectifier, 7...
9... AGC amplifier, 8A/8B... Gate control section, C... Capacitance, D-Dl -D ・D3... Diode, R・R1・R2@R3°R4@R5 °°°Resistance 1Q1 @Q2...Transistor. Patent applicant Yaesu Musen Co., Ltd. (15) Figure 1 Figure 2 ■■ @ 0 ■@○ Procedural amendment (method) % formula % ) 1. Indication of the case Patent Application No. 170867 of 1982 2. Invention Name: Noise blanker circuit 3, Contact number of person making the correction: Telephone: 03-759-71114, Date of correction order: 7 Figure I, Rectifier section, 717 Yotsu;)

Claims (3)

[Claims] (1) A form in which the signal output is kept constant at the noise amplification stage of a noise blanker circuit that controls the noise dirt provided in the signal passing stage of a radio receiver and removes pulse noise mixed in the received signal. In a circuit that performs noise/dirt control by separating noise and normal pulses by multiplying them by AGC, in addition to the first AGC that keeps the output of the signal constant, noise with an amplitude greater than a set value By providing a second AGC that reduces the output of Noyalus, it is possible to reduce the large amplitude noise/t4us from the noise amplification stage from entering the signal circuit after the noise gate. A noise blanker circuit featuring: (2) Adding the rectified output of the noise amplification stage to the pace of the AGC amplification transistor through an integral time constant circuit,
The configuration is such that the change in the collector potential is supplied as the AGC of the noise amplification stage, and the rectified output of the noise amplification stage is added to the pace of the r-) control transistor whose emitter is connected in series with a diode, and the collector of that collector and the collector of the AGC amplification transistor are connected. A patent claim characterized in that an AGC control voltage that operates on both signal noise and pulse is obtained at the collector of the AGC amplification transistor when a gate control noise occurs by connecting the two with a diode. The noise blanker circuit described in item 1. (3) Adding the rectified output of the noise amplification stage to the pace of the AGC amplification transistor through an integral time constant circuit,
By connecting a diode in parallel with the time constant resistor of the integral time constant circuit of the first AGC amplifier configured to supply the change in collector potential as the AGC of the noise amplification stage)
, the second AG operates with a noise noise whose amplitude is greater than the initial conduction voltage of the diode than the amplitude of the input signal.
2. The noise blanker circuit according to claim 1, having a configuration that can be shared as a noise blanker circuit.