JPH0520034Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial application field" This invention is a FS communication receiver that shifts the carrier frequency with an on/off signal and performs frequency shifting (hereinafter referred to as FS) to communicate, especially for wireless facsimile broadcasting. The present invention relates to a tuning instructing device for instructing a tuning state of a receiver to a carrier wave in a receiver.

``Conventional technology'' In facsimile broadcasting, information is transmitted by FS modulating a carrier wave. That is, the image signal shown in FIG. 3A is waveform-shaped as shown in FIG. 3B, and the carrier wave of frequency ₀ shown in FIG. 3C is changed to a black signal as shown in FIG. _{3D .} The signal is shifted to a low frequency of ₁ , and the carrier wave is shifted to a high frequency signal of ₀ + _S = ₂ and transmitted using a white signal. Generally _S is 400Hz
Carrier wave ₀ is approximately 3 to 25 MHz.

In a receiver that receives such broadcast facsimiles, a tuning instruction device is used to display whether the tuning operation on the tuning device has been performed correctly.

In the conventional tuning instruction device, as shown in FIG. 4, an input signal from an input terminal 11 is transmitted through resistors 12 and 13 to a tuning circuit 14 tuned to frequency ₁ and a tuning circuit 15 tuned to frequency ₂ , respectively. The outputs of the tuning circuits 14 and 15 are respectively detected by diodes 16 and 17 and charged into capacitors 18 and 19.The outputs of the capacitors 18 and 19 are connected to light emitting diodes 21 and 22, respectively, and are further connected to level adjustment resistors. It will be installed through 23rd and 24th.

When the input signal is a black signal, that is, the frequency _{is 1} , there is little attenuation in the tuning circuit 14, and a large current flows to the light emitting diode 21, causing it to light up brightly. When the input signal is a white signal, the output of the tuning circuit 15 is large and a large current flows through the light emitting diode 22, causing it to light up brightly.

However, if the tuning state of the receiver is incorrect, the tuning circuits 14 and 15 will not be properly tuned to frequencies ₁ and ₂ , respectively, so when a black signal is input or a white signal is input, the light emitting diodes 21, 22
Only a small amount of current flows through the lamp, resulting in dim lighting, or in some cases, no lighting at all. Therefore, by adjusting the dial of the tuning circuit so that the light emitting diodes 21 and 22 become the brightest, correct tuning can be obtained, and in that state, the adjustment can be stopped to continue the correctly tuned reception state.

``Problems to be solved by the invention'' As described above, the conventional tuning instruction device uses tuning circuits 14 and 15, and the components of these tuning circuits generally have relatively large temperature characteristics. There was a problem that it was easily affected by changes, making it impossible to detect the correct state of synchronization. Furthermore, it is necessary to properly adjust the frequency characteristics of the tuning circuits 14 and 15 during manufacturing, and the adjustment is relatively difficult.

"Means for solving the problem" According to this invention, the received FS signal is converted to a lower frequency by a frequency converter, and the converted signal is approximately the same as the output of the frequency converter when properly tuned. The frequency is mixed with a reference signal of the same frequency by a frequency mixer, and the frequency component of the difference between the two is output. The frequency or period of the difference frequency component is digitally counted by a counter, and the counted value is supplied to a display to display the tuning state.
Further, when the counter reaches a predetermined value, its counting operation is stopped.

Embodiment FIG. 1 shows an embodiment of the tuning instruction device according to this invention, in which an input signal from an input terminal 11 is converted to a lower frequency by a local signal from a local oscillator 32 at a frequency converter 31. The frequency of this frequency-converted signal is, for example, about 50KHz or 10KHz, which is the white signal frequency of 2300 in wired facsimile.
It may be around Hz.

The output of the frequency converter 31 is supplied to the frequency mixer 33, where it is frequency mixed with the signal of the oscillator 34, and a frequency component of the difference between the two signals is output. The oscillator 34 is selected to be the correct white signal frequency at the output of the frequency converter 31, for example 50KHz+400Hz. The difference frequency component from the frequency mixer 33 is selected by a low pass filter 35 and supplied to the clock terminal ck of a counter 38 through an amplifier 36 and a gate 37 as required.

The output of the oscillator 34 is divided by a frequency divider 39 to have a frequency of, for example, 100 Hz, and is supplied to a reset pulse generator 41. Reset pulse generator 41
to period T ₁ (10 in this example) as shown in Figure 2A.
A reset pulse (milliseconds) is generated, thereby resetting the counter 38. The first stage output Q ₀ and the next stage output Q ₁ of the counter 38 are given to the NAND gate 42, and the output of the NAND gate 42 is fed to the AND gate 37.
has been entered.

The output of the frequency divider 39 is also supplied to the latch pulse 43, and as shown in _FIG. , Q ₁ output is the latch circuit 44
is latched to. The output of latch circuit 44 is decoded by decoder 45. The decoder 45 is connected to a terminal when both Q ₀ and Q ₁ outputs of the latch circuit 44 are zero.
An output is generated at Y ₀ , and the terminal Y ₀ is a light emitting diode 46,
It is installed through a resistor 47. Q ₀ output is 1,
When the _Q1 output is 0, an output is generated at the terminal _Y1 of the decoder 45. When the _Q0 output is 0 and the _Q1 output is 1, an output is generated at the terminal _Y2 of the decoder 45. Terminal Y ₀ ,
Each output of Y ₁ is supplied to a light emitting diode 49 and a resistor 51 through an OR gate 48 . Also terminal
The output of Y ₂ and the output of the OR gate 48 are supplied to a light emitting diode 53 and a resistor 54 through an OR gate 52 .

Because of this process, when the output of the frequency mixer 33 is _T2 , which is slightly longer than the period of the reset pulse as shown in FIG. 2, the _Q0 output of the counter 38 becomes high level as shown in FIG. The _Q1 output remains at a low level as shown in Figure 2E. Therefore, the counter 38
Q ₀ =1, Q ₁ =0 are latched in the latch circuit 44,
The Q ₀ and Q ₁ outputs of the latch circuit are at high and low levels as shown in _FIG . and 53 are lit to indicate that the synchronization state is relatively close.

As shown in FIG. 2C, when the output frequency of the frequency mixer 33 is considerably lower than the reset pulse and the period is _T3 , the counter 38 continues to be reset by the reset pulse, and the output frequency of the frequency mixer 33 continues to be reset. There are very few opportunities for the counter 38 to count due to the fall of the output, and the counting state of the counter
Both Q ₀ and Q ₁ are mostly 0, which is latched by the latch circuit 44. Therefore, an output is generated at the output terminal _Y0 of the decoder 45 as shown in FIG. 2I, and the three light emitting diodes 46, 49, and 53 light up, indicating that the receiver is correctly tuned to the received radio waves. be done.

On the other hand, the frequency of the output of the frequency mixer 33 is high,
If the period _T4 is much shorter than the reset period T, as shown in FIG. vessel 38
2, the Q ₀ and Q ₁ outputs of the counter 38 immediately become high level as shown in FIG. 2D and E, and in this state, the NAND gate is activated as shown in FIG. The output of 42 goes low and the input of counter 38 is blocked, so that Q ₀ ,
Q ₁ are both held at 1. Therefore, the outputs of Q ₀ and Q ₁ of the latch circuit 44 also become 0, and an output is generated at the output terminal Y ₃ of the decoder 45 as shown in FIG. Therefore, it is displayed that the receiver is considerably out of tune with respect to the received radio waves.

If the reset period T ₁ is 10 milliseconds as in this example, when the light emitting diodes 49 and 53 light up, the output of the frequency mixer 33 is supplied to the counter 38 one pulse at a time for each reset period. It can be seen that the detuning state is about 100Hz.

The detuning state can also be displayed in detail by increasing the maximum count value of the counter 38, expanding the capabilities of the latch circuit 44 and decoder 45, and increasing the number of light emitting diodes. Although the frequency components of the frequency mixer 33 are counted, the tuning state may be displayed by measuring the period of the difference frequency component.
Furthermore, the color of the emitted light may be changed instead of the number of emitted light depending on the tuning state. Furthermore, the tuning status may be indicated by a numerical display. In some cases, the meter pointer may also be displayed by waving. If you want to display the tuning state of the black signal as well, you can configure the frequency mixer and oscillator for the black signal on the output side of the frequency converter 31 in the same way, and OR-combine the output of that decoder with the output of the decoder 45 for the white signal. Then, the synchronization status will be displayed without flickering regardless of whether the signal is black or white. In addition, in facsimile, compared to the black light time,
Since the time required for a white signal is extremely long, the white signal device shown in FIG. 1 alone is sufficient. However, when used as a tuning instruction device for general wireless FS communication, it is desirable to provide a white signal and a black signal in parallel.

``Effects of the invention'' As stated above, the tuning instruction device of this invention does not use a tuning circuit for detecting the tuning state, and can be constructed almost entirely of digital circuits, and its adjustment is extremely simple. In addition, it is not easily affected by temperature fluctuations, and it is possible to always achieve correct tuning relatively easily. Although an oscillator is provided, this can be constructed more inexpensively by utilizing the output of an oscillator existing within the receiver. Furthermore, the tuning state is displayed by a digital counter, but since the counter is configured to stop counting when it reaches a predetermined value, even if the number of stages counted by the counter is small, the tuning state will be displayed within the range of the small number of stages. can be displayed correctly. In other words, without the NAND gate 42 in the example of FIG. 1, if the count output is latched to the latch circuit 44 with the counter 38 overflowing and both Q ₀ and Q ₁ becoming 0, the synchronization will shift. Despite the fact that it is, it is displayed that it is quite well synchronized. However, with this invention, such malfunctions do not occur.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a tuning instruction device for a wireless FS receiver according to this invention, Fig. 2 is a time chart for explaining its operation, and Fig. 3
The figure is a time chart showing the relationship between the image signal and the modulated wave of the FS, and FIG. 4 is a connection diagram showing a conventional tuning instruction device.

Claims (1)

[Claims for Utility Model Registration] A frequency converter that converts a received FS signal into a low frequency signal, the output of the frequency converter, and a reference signal of substantially the same frequency as the converted frequency in the case of the correct frequency. a frequency mixer that mixes frequencies and outputs a difference frequency component, a counter that digitally measures the frequency or period of the difference frequency component from the frequency mixer, and a count value of the counter that is a predetermined value. A tuning instructing device for a wireless FS receiver, comprising: means for stopping counting when the counter is reached; and a display for indicating the tuned state of the receiver by displaying the counted value of the counter.