JPH0326121A - Modulation degree control circuit when frequency modulation panel is not mounted - Google Patents

Abstract

PURPOSE:To execute a control so that the characteristic deterioration of a main signal cannot be generated when a subsignal processing panel is inserted into a device by varying the resistance of a subsignal path through the use of a control circuit. CONSTITUTION:When a subsignal processing panel 5 is pulled out from a frequency modulation panel 1, a connection from the subsignal processing panel 5 to a modulation control part 4a is disconnected at a connecting point A and a connecting point B, the resistance value of a variable resistance 41a is made into an infinite open condition, and thus, an amplification degree A of an amplifier 42a is lowered. When the subsignal processing panel 5 is inserted, the connection to the modulation control part 4a is restored, a bias current flows from a d.c. voltage to a fixed resistor R4 and a fixed resistor R3, the variable resistance 41a is made into an ordinary resistance value by a d.c. bias from a control circuit 43a, the amplification degree A of the amplifier 42a is returned to a normal value, and a signal at a normal value is outputted from the modulation control part 4a. consequently, a normal modulated signal is outputted from a main signal phase modulator 2.

Description

[Detailed Description of the Invention] [{Already required] Regarding a modulation degree control circuit of a digital multiplex radio device, particularly a level control circuit for a sub signal when a sub signal processing panel is inserted, the sub signal processing panel is inserted into the device. In order to provide a modulation degree control circuit that does not cause characteristic deterioration of the main signal when the main signal is In a frequency modulation panel that sends out a modulated signal by adding it to a main signal phase modulator along with a sub signal from the sub signal processing panel, one end applies a DC voltage and the other Connect the ends as described above. The sub-signal processing panel is grounded through a terminal, and the sub-signal processing panel outputs a bypass voltage that detects whether or not it is connected to the frequency modulation panel. a bias control means for controlling to absorb the sudden change in potential that occurs at the connection point when the is connected to a frequency modulation panel; and a bias voltage from the bias control means is applied and the resistance value is varied by A resistance variable means for performing control, and a target connected to the resistance variable means, when the sub signal processing panel is not connected to the mounting 1, the j{τ. The structure is provided with a modulation degree control means having amplification degree variable means for amplifying the signal so as to decrease the amplification degree.

(Industrial Application Field) The present invention relates to a modulation degree control circuit for a digital multiplex radio device, and particularly to a sub signal level control circuit when a sub signal processing T1 panel is inserted.

? Conventional Techniques] Figure 4 is a diagram showing the path configuration of a conventional example (-). In the figure, 1 is frequency modulation/''9, 2 f;l: , :t.{'?.i phase change #JR
3 is a voltage controlled crystal oscillator; 5 is an additional signal processing panel having a sub-signal amplifier 51;

In the digital radio system (2), the pulse-modulated so-called PCM data signal, the amplification of audio signals, etc., and the control of sub-signals (modulated frequency signals obtained in addition to the control crystal oscillator 3) are used. A main signal phase modulator 26 is added to perform phase modulation of the main signal by the sub signals 6 and ′, and a modulated signal is output.

In such a case, J′! '1 When the wave number modulation panel 1 is inserted into the digital radio device, a potential difference is generated at the connection point 8. This connection yF. Since there is a potential difference between z and 8, a transient voltage is applied to the voltage controlled crystal oscillator 3, which causes a sudden fluctuation in the output phase of the voltage controlled crystal oscillator 3.
This causes instantaneous large fluctuations in the phase of the output of the main signal phase modulator 2.

[Problem to be solved by the invention]

Therefore, since phase fluctuations occur in the modulated signal, it is affected by demodulation in the receiving system, and there is a problem that, for example, a bisoto error occurs during reception.

An object of the present invention is to provide a modulation degree control circuit that does not cause characteristic deterioration of a main signal when a frequency modulation processing panel is inserted into a device. As shown in FIG. 1, there is a sub-signal processing panel 5 that outputs a sub-signal obtained by amplifying external audio, etc., and a main signal phase modulator that outputs the main signal from the outside together with the sub-signal from the sub-signal processing panel 5. In the frequency modulation panel J, which sends out a modulated signal by adding a signal to Grounding is performed inside the sub-signal processing panel 5, and the bias voltage detected as to whether or not the sub-signal processing panel 5 is connected to the frequency modulation spring 5 is output. With,
Bias control '4? which performs control to absorb the sudden potential difference change that occurs at the connection point when the sub signal processing panel 5 is connected to the L, J wave number modulation panel 1. jJI'f- stage 43, the high-ass control means 43 is connected to the resistance variable means 41 which performs variable control of the resistance value by applying a bias voltage, and the m number of resistance variable stages 4I. ,, if the sub-signal processing panel 5 is not mounted, it has an amplification degree varying means 42 for amplifying so that the output voltage applied to the voltage-controlled crystal oscillator 3 is reduced. 7 and 4 stages of modulation depth control are provided.

[For production]

In the present invention, as shown in FIG.
In the modulation level control stage 4 provided on the input side of When the control stage 43 outputs a bias voltage that detects whether or not the sub signal processing panel 5 is connected to the frequency modulation panel 1, and the sub signal processing panel 5 is connected to the frequency modulation panel ■. Control is performed so that a sudden change in potential difference occurring at the connection point is absorbed, and this bias voltage is further controlled by the resistance variable means 41.
In addition to that, by changing the resistance of the sub signal path, a variable amplification stage of 42
I am trying to connect to.

Therefore, since the amplification degree of the variable amplification level 42 can be varied by changing the resistance of the variable resistance stage 4l, the sudden phase fluctuation that occurs when the sub signal processing panel 5 is inserted into the device is suppressed, and the reception It is possible to provide a modulation degree control circuit that does not cause signal characteristic deterioration.

〔Example〕

FIG. 2 is a diagram showing the layout of a circuit according to an embodiment of the present invention.

In the figure, 1 is a frequency modulation panel, which is a circuit consisting of a main signal phase modulator 2, a voltage controlled crystal oscillator 3, and a modulation control section 4a, which are the same as in the conventional example.

This modulation control section 4a corresponds to the 1,000-stage modulation degree control 4 of the present invention, and its circuit structure includes a variable resistor 41a as the variable resistance means 4l, a fixed resistor R1, and a 1,000-stage variable amplification level 42. This circuit has a control circuit 43a consisting of an amplifier 42a, a fixed resistor R2, a fixed resistor R3R as a bias control stage 43, and a capacitance C.

Note that 5 is a sub-signal processing panel having the same sub-signal amplifier 51 as in the conventional example. Furthermore, the connection point A is a connection point that becomes the input side for audio, etc., and the connection point B is a connection point that connects one end to the control circuit 43a and earths the other end to prevent high-ass voltage.

When the sub-signal processing panel 5 is disconnected from the frequency modulation panel 1, the connection from the sub-signal processing panel 5 to the modulation control section 4a is cut off at connection point A and connection point B. When the connection point l3 is disconnected, the bias current flowing through the fixed resistor R4 and the fixed resistor R3 stops flowing due to the DC voltage applied to the control circuit 43a, and the resistance value of the variable resistor 41a becomes infinite ozone. This causes the amplification degree A of the amplifier 42a to decrease. That is, the level of human power applied to the voltage controlled crystal oscillator 3 via the connection point A is reduced, and the generation of abnormal voltage caused by disconnecting the connection points A and B is suppressed.

On the other hand, when the sub signal processing panel 5 is inserted, the connection to the modulation control section 4a is restored, and the fixed resistor R4 is connected to the DC voltage.
A bias current flows through the fixed resistor R, and the variable resistor 41
a becomes a normal resistance value due to the direct current high-ass from the control circuit 43a, the amplification degree A of the amplifier 42a returns to the normal value, and a signal with a normal value is output from the modulation control section 4a. Therefore, the main signal phase modulator 2 outputs a normal modulated signal.

In this process, the control circuit 43a has a delay element consisting of a fixed resistor R, a fixed resistor R4, and a capacitance C1, and is designed to absorb very thin pulses. This stabilizes the circuit operation by preventing it from following instantaneous fluctuations.

Incidentally, FIG. 3 is a diagram showing a time chart of a circuit according to an embodiment of the present invention. As shown, frequency modulation panel 1
The amplification degree A1 at the time of extraction of R. On the other hand, the amplification degree A2 when inserting the frequency modulation panel l is R,
VR, that is, Az>A+ is obtained.

〔Effect of the invention〕

As explained above, according to the present invention, by varying the resistance of the sub-signal path using a control circuit, it is possible to prevent the characteristics of the main signal from deteriorating when the sub-signal processing panel is inserted into the device. Therefore, a stable frequency modulation degree control circuit can be realized.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the principle structure of the present invention, FIG. 2 is a diagram showing a circuit configuration of an embodiment of the invention, and FIG. 3 is a diagram showing a time chart of the circuit of an embodiment of the invention. FIG. 4 is a diagram showing the circuit configuration of an embodiment of the conventional example. In the figure, ■ is a frequency modulation panel, 2 is a main signal phase modulator, 3 is a voltage controlled crystal oscillator, 4 is modulation degree control means, 41 is resistance variable means, 42 is amplification degree variable means, 43 is bias control means, 5 indicates a sub-signal processing panel. Il! of one embodiment of the present invention! Figure 2 shows the structure of the circuit. Time t-p. Figure 3 shows the time chart of the circuit according to an embodiment of the present invention.
Figure 4 shows the principle structure of the present invention Figure 4 shows the circuit structure of an embodiment of the conventional example

Claims (1)

[Claims] A sub-signal processing panel (5) that outputs a sub-signal obtained by amplifying external audio, etc.; Modulator (2
), at the connection point of the sub-signal of the frequency modulation panel (1), one end applies a DC voltage and the other end applies a DC voltage via the connection point. The sub signal processing panel (5) is grounded inside, and the sub signal processing panel (5) outputs the bias voltage used to detect whether or not it is connected to the frequency modulation panel (1). a bias control means (43) that performs control to absorb a sudden potential difference change that occurs at the connection point when the signal processing panel (5) is connected to the frequency modulation panel (1); and the bias control means (43).
) is connected to the resistance variable means (41) for variable control of the resistance value by applying a bias voltage from the auxiliary signal processing panel (5). amplification degree variable means (42) for amplifying so that the output voltage applied to the voltage-controlled crystal oscillator (3) becomes small when the voltage-controlled crystal oscillator (3) is not present; and a modulation degree control means (4) having the following: Modulation degree control circuit when a modulation panel is not installed.