JPS581311A - Receiver - Google Patents

Abstract

PURPOSE:To perform reception stable against variation in electric field level by using an AGC circuit and an attenuator as two systems, and operating the attenuator provided to an input circuit during large input. CONSTITUTION:In accordance with the output level of a detector 7, the 1st AGC circuit 12 operates. The 1st AGC circuit 12 controls the gains of a high frequency amplifying circuit 3 and an intermediate frequency amplifying circuit 6 to hold the output level of the detector 7 below a certain value. The 1st AGC circuit 12, however, has a limit of control, so an excessive input signal when arriving allows the intermediate frequency amplifying circuit 6 to output a signal which exceeds the certain value. Only when said case occurs, the 2nd AGC circuit 13 controls an attenuator 11 to hold the output signal below the certain value. Therefore, the operation of the receiver of a radio control system is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in receivers, particularly in radio control systems.

When remotely controlling a model airplane etc. using radio control method, 1. The electric field strength at the position of the airplane varies greatly depending on the distance between the airplane, etc. and the transmitter and the terrain. However, the receiver installed inside the device is required to operate stably regardless of the strength of the electric field. Therefore, a receiver is usually equipped with an automatic gain control circuit (hereinafter referred to as an AGC circuit). FIG. 1 is a block diagram showing an example of a conventional multi-channel digital broadcast receiver. . The output signal of the high frequency tuning circuit Hatake is mixed [I! 4, the signal is once converted to an intermediate frequency. 6 is a local oscillator. The intermediate frequency signal is amplified by an intermediate frequency amplification circuit 6 and demodulated by a wave detector 7. The obtained signal is converted into a sharp square wave through a waveform shaping circuit 8, and converted into an output for each channel by a decoder 9. Here, the AGCIK pressure is taken out from the output of the detector 7 by the original circuit lO and added to the intermediate frequency amplifier circuit 6 and the high frequency amplifier circuit. There is.

By the way, in the digital broadcasting system, there is no need to fully reproduce the amplitude component of the transmitted signal (
It is important that the distinction between @O” and “1” is completely made. Therefore, it is preferable that the output signal of the amplifier is somewhat saturated in order to eliminate interference and noise. For this reason −ζ
In order for the AGC to maintain a certain minimum gain, it is necessary to maintain the state.

FIG. 8 shows the detection l! for various electric field intensities when the AGC intensity settings are changed in the conventional example shown in FIG. It shows the output waveform of T, and the subscripts a, b-, and e are respectively I! shows the weak electric field, medium electric field, strong electric field, and extreme electric field, and the subscripts l and 2 indicate the case where AGC is strong (and the case where AGC is weak), and the fH1 diagram shows each detection output when there is noise. The waveform diagrams shown in FIG. 4 are the output waveforms of the detector 7 when there is interference from the pulse signal of the adjacent channel, and FIG. 6 is the output waveform diagram of the detector 7 when there is strong interference, and the meanings of the subscripts are the same as in FIG. w12.

Here, the AGC is set weakly so that the AGC maintains a constant minimum gain (hereinafter, the one in which the AGC is set weakly is referred to as the eighth conventional example), and @S diagram (a-1).

(b-1), (c-1) and Figure 8 (l-2 people (g2)
, (c-2), it is important to reduce the influence of noise. Also, since satay lanes occur inside the receiver, Figure 4 (b-1), (d-1) and Figure 4 (
tr-11), (d-4)-Sara 1bi is the first violent diagram (d-1)
, (・-1) and Figure 6 (d-type entry (@-○), which reduces the influence of interference. Also, Figure 2 (a)
1), (g1) and Fig. 3 (*-1), (b-11), a weak electric field can provide high sensitivity.

However, when the AGC is set weakly, extreme saturation occurs in strong electric fields as shown in Figures 11 (d-g) and (*-2), and as a result, the detection output voltage actually decreases and the desired output voltage is lowered. Is it a drawback that you can't get a pulse signal? Ta. Conversely, if the AGC is set strongly (hereinafter, the one in which the AGC is set strongly will be referred to as the 1st conventional example), there will be no drop in the output voltage due to extreme saturation, but as mentioned above, the sensitivity will be low due to the weak electric field. It had the disadvantage of being susceptible to noise and interference. In this way, when using a conventional AGC circuit,
Regardless of whether the AGC setting is made stronger or weaker, a drawback occurs in either case.

The purpose of the present invention is to eliminate all of the conflicting drawbacks of the conventional art, and to provide a two-system AG system.
It is an object of the present invention to provide a receiver capable of obtaining a highly sensitive and always stable output pulse signal using a C circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below with reference to the drawings. FIG. 6 is a block diagram of a receiver showing an embodiment of the present invention. In this figure, a high frequency tuning circuit 2 is connected to an antenna 1 as in the conventional example shown in FIG.

Attenuation W11 is connected to the output end of this high frequency tuning circuit 2. When the input signal is above a predetermined value, the attenuator 11
The output signal of the high frequency circuit i is attenuated and transmitted to the next stage high frequency amplification circuit. A high frequency amplification circuit is provided as necessary to amplify the input high frequency signal, and its output is given as a mixture 841. The mixer 114 receives the output of the local oscillator 6 and converts the input signal into an intermediate frequency signal -ζ.

The output is given to the next stage intermediate frequency amplification circuit.

In the intermediate frequency amplification circuit, when the intermediate frequency signal is amplified, the common number ζ is extracted, and the signal is extracted from the middle of the signal. AGC circuit 1
Give 1ζ. No.! The AGC circuit 1$ is a circuit for obtaining an attenuated signal that increases from a predetermined level of the intermediate frequency in accordance with an increase in the signal level, and its output is given to an attenuator H. As in the conventional example, the output of the intermediate frequency amplifying circuit is given to the detector number ζ and then regenerated, and then shaped by the waveform shaping circuit number 8.

The output of the m-shaped waveform is given to a decoder.

The decoder decodes the signal and converts it into a control signal for each channel. @I AGC-route 1 is to extract the AGCIK pressure from the 1ζ detection iIi as in Sakaki's previous example, and in the present invention, the AGCIIE pressure is added to the high frequency amplification circuit 6 and the intermediate frequency amplification circuit 6. The AGC is set to weak (as in the conventional example of @1).

FIG. 7 is an example of a different circuit diagram of the main part of the present invention, and the same reference numerals as in FIG. 6 indicate the FI-r portion.
At l#ζ, capacitor CI at attenuation @11.

A series connection body of cm is connected between the input and output terminals.

A series connection body of diodes DI and DI is connected to the midpoint. The other end of the diode-FDl is connected to the power supply, and the other end of the diode DI
The other end is connected to the fIIi GCIt line 11V.

The mixer 4 is the emitter ζ of the mixing transistor TRI.
This is an emitter injection method in which a local oscillator signal is injected into the local oscillator, and only the intermediate frequency signal is given to the intermediate frequency amplification circuit 6 at the next stage. Also, a part of the intermediate station wave signal is simple AGC.
times are given. The eighth low cost circuit 1- is a transistor T1 which converts the signal level into a voltage magnitude - ζ!
2 and is applied to the base -ζ of the intermediate frequency signal body transistor TR8. A capacitor Cs is connected between the collector of the transistor TRY and the 7th stage to smooth out fluctuations in the collector voltage. Capacitor C4 is a high frequency bypass capacitor, and is connected exclusively to one end of diode DI with attenuation 1#11. I will explain while referring to it. In each figure, the subscript 8 indicates the waveform of the receiver in this embodiment, and the meanings of the other subscripts are the same as in the previous case. The AGC is weak like the cylindrical conventional example (because it is electrically installed, it is 1 m (a-Hatake L)
(b-1) As shown in K, the sensitivity does not decrease in a weak electric field.

Also, since a moderate Sachile scene occurs in a weak electric field,
Figure (i-1), (lr-snow) k and the same simple conventional example as shown in Fig. CIII (龜-8) @ (b-1). This is IU Sushi.

When the electric field strength becomes stronger, the 1IIAGclljl becomes more active, and the gain gradually decreases to 1, keeping the receiver's power level constant.

It is preferable that this constant level is near the saturation point of the output signal.
The operating limit of path 12 is reached. However, in the present invention, the #Ih circuit 18 starts operating. That is, transistor P
T:1! The base current increases and the collector current flows,
The potential of the collector decreases. Then attenuation 91 from the power supply
Current begins to flow through the diodes DI and Dg of No. 1, and the diodes Di and DI become conductive. Therefore, a part of the high frequency signal obtained from the high frequency tuning circuit is transmitted through the diode D.
i, and also via the diode D2 and capacitor C4, the high frequency signal is attenuated. For this reason, the electric field strength is stronger than a certain level (even in the summer).

1st m1 (d-heavy), (d-1), (・-bulk), (・-
As shown in 8), unlike the 1ζ third conventional example, extreme satire reduction does not occur and the output pulse signal is kept constant.

Also, the IR reducer 11 is provided before passing through the active element, so @Figure 4, Cb-1) * (tos),
(a-1), (--1) and #ii figure (d IL
As shown in (d I)-(e-1)s(*I), 1ζ,
Easy modulation caused by the nonlinear characteristics of the active element can be effectively prevented.

As explained in detail above, in the WA issued by the present application.

g I Start the operation N#1 from the level where the AGC operation of the AGCml path ends! gI AGCml path is used for widening the range in which AGC can operate effectively. Because of C, the first AGC circuit is set to weak (-), in a weak electric field, the high degree is swept away, and the noise is reduced based on the noise, so a stable waveform can be obtained.Also, even in a strong electric field, the extreme Therefore, an output signal of a constant level can be obtained.The present invention thus has both the advantages of the conventional example of @1゜Tsutsuyuki, but %7.More sc jl M)AG
Since the C signal is given to the attenuation 911 before the increase 115WjJ path, the bulk modulation characteristic I! ! is also significantly improved. This is particularly effective in the case of strong electric fields when transmitters of several adjacent channels are operated at once, and can greatly improve malfunctions caused by wave modulation.

Although the attenuator in the embodiment shown in FIG.

Furthermore, the present invention can be applied not only to a Hethylogin type receiver but also to a homodyne receiver.

[Brief explanation of drawings]

*IB is a block ail indicating an example of a conventional receiver. Figures 3 to I are waveform diagrams of the detection output under different conditions, where the first intention is when there is no noise or interference, the S figure is when there is noise, and the fourth figure is the pulse of the adjacent channel. When the signals are interfering, number 111 indicates the case where this interference is strong. In the diagram, the subscript ash"' indicates weak electric field, weak electric field, and medium electric field, respectively. l is when strong AGC is applied in a conventional receiver (conventional example #11),
When Utomi Soe uses weak AGC in a conventional receiver (third conventional example), suffix 8 indicates the receiver of the present invention, and #I6 is a block diagram showing an embodiment of the present invention,
The fI11 map shows a variant example of the present application. l-antenna, ■-・Takane-ji tuning circuit, Hatake *** high shoulder wave amplification circuit, 4-mixing II, ・-Nakaoka frequency increase 5ili circuit,! ...Detection-110-AGCWA path, 11-attenuator, 1st AGCWA path, 11-1st AGC
ML Road Agent Patent Attorney Yoshiki Okamoto (and 1 other person) Figure 2! -1) I'-■'s -9 ■Two (to). ■=3) ((1-3) Q-ri (It-1) (e-υ Figure 4/Figure 5

Claims (3)

[Claims] (1) an attenuator that attenuates a high frequency input signal obtained from an antenna according to an externally applied attenuation signal -ζ;
an amplifier circuit that amplifies the signal that has passed through the attenuator; a detector that demodulates the amplified output of the amplifier circuit; a first automatic gain control circuit (hereinafter referred to as an AGC circuit); and an AGC circuit of I2 which receives the output signal of the amplifier circuit described in tIJ as input and provides an attenuation signal to the attenuator according to the signal level when the signal is at a predetermined level or higher; A receiver comprising: (2) The first aspect of the present invention is characterized in that it has a frequency conversion section that converts the output of the attenuator into an intermediate frequency, and the amplifier circuit is an intermediate frequency amplification circuit that amplifies the intermediate frequency.
13 [Receiver described. (3) The predetermined level in the eighth AGC circuit is the #! Receiver 0 according to claim 1 or 2, characterized in that the input signal level is set to substantially match the input signal level of the AGC operation limit of the AGC circuit of claim 1.