JPS6313378B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a heterodyne relay broadcasting device for amplitude modulated waves that converts a reception frequency to an intermediate frequency and then to a transmission frequency, and relates to a transmission frequency that is replaced by a television channel. The present invention also relates to a transmission frequency control method that does not require changing the transmission frequency control circuit even if the receiving station is located at a location separate from the transmitting station.

(b) Prior Art and Problems FIG. 1 is a block diagram of a conventional method for controlling a transmitting station oscillator by comparing the amplitude-modulated transmitting video frequency and the frequency of a highly stable reference oscillator.

In the figure, 1 and 7 are antennas, 2 is a high frequency amplifier,
3, 5, 16 are mixers, 4 is an intermediate frequency amplifier, 6
8 is a receiving station oscillator composed of a crystal oscillator, and 9 is a transmitting station oscillator, which is a voltage-controlled type. 10 is a circuit such as a wave device, 11 is a limiter,
12 and 14 are frequency dividers, 13 is a phase comparator, 15 is a highly stable reference oscillator, and 17 is a high-order multiplication wave generator.

The amplitude-modulated reception frequency received by the antenna 1 is amplified by the high frequency amplifier 2, mixed with the signal from the receiving station oscillator 8 by the mixer 3, and made into an intermediate frequency, which is amplified by the intermediate frequency amplifier 4. The signal is then mixed with the frequency of the transmitting station oscillator 9 in the mixer 5 to create a predetermined amplitude-modulated transmission frequency, which is amplified in power by the power amplifier 6 and transmitted via the antenna 7.

When transmitting television video signals, it is required that the deviation from a predetermined frequency be within 2.5 Hz.

For this reason, the amplitude-modulated transmitting video frequency is controlled by a circuit 10 such as a wave generator to generate a spurious-free transmitting video frequency (intermediate frequency + frequency of the transmitting station oscillator).
is taken out and inputted to the mixer 16 via the limiter 11. On the other hand, the frequency of the highly stable reference oscillator 15, for example 10MHz, is changed to 1MHz by the frequency divider 12, and the high-order multiplication wave generator 17 generates high-order multiplication waves at 1MHz intervals. Be sure to set 250KHz as low as the difference with the transmitted video frequency.
A frequency of 250KHz is output and input to the phase comparator 13. On the other hand, the frequency of the highly stable reference oscillator 15 is divided by the frequency divider 14 for the phase comparator 13.
A frequency of 250KHz is input. Here, the phase comparator 13 provides a highly stable 250K output from the frequency divider 14.
Hz and the output from the mixer 16 are compared in phase, and the frequency of the local oscillator 9 is controlled by the output. As a result, even if the intermediate frequency deviates to some extent, this is compensated for by controlling the frequency of the local oscillator 9, and the transmission frequency becomes a predetermined semi-refined value. However, the transmission video frequency is VHF and UHF bands, and there are dozens of different frequency signals depending on the TV channel, so the circuit 10 such as a wave transmitter must be changed accordingly, and the limiter 11 must also cover all frequency bands. It has the disadvantage that it cannot be obtained and must be changed depending on the frequency band.

In order to eliminate this drawback, the following method is available.

FIG. 2 is a block diagram of another conventional frequency control system for a receiving station oscillator and a transmitting station oscillator.

Components in the figure that have the same functions as those in FIG. 1 are indicated by the same symbols. 8' is a receiving station oscillator, 9' is a transmitting station oscillator, 18 is a highly stable reference oscillator, 19 is a frequency divider with a frequency division ratio of 1/5, 20 is a high-order multiplication wave generator, 21
is a mixer, 22 and 25 are phase comparators, 23 is a frequency divider with a frequency division ratio of 1/20, 24 is a frequency divider with a frequency division ratio of 1/71, and 26 is a frequency divider with a frequency division ratio of 1/40. Shows the circumference.

In the case of Figure 2, first the intermediate frequency (17.75MHz)
is extracted from the output of the intermediate frequency amplifier 4 and divided by the frequency divider 24 with a frequency division ratio of 1/71 to generate a frequency of 250 KHz.
The phase of the highly stable 250KHz frequency obtained by dividing the 10MHz frequency by the frequency divider 26 with a frequency division ratio of 1/40 is compared by the phase comparator 25, and the voltage-controlled receiving station oscillation is performed so that they match. It controls the frequency of the oscillator 8'.
On the other hand, the output frequency of the voltage-controlled transmitting station oscillator 9' is input to the mixer 21, and the frequency of the 10MHz highly stable reference oscillator 18 is divided by the frequency divider 19 with a frequency division ratio of 1/5. Then, generate 2MHz, input it to the high-order multiplication wave generator 20, generate high-order multiplication waves at 2MHz intervals, input it to the mixer 21, and make sure that the frequency is higher than N' times 2MHz.
The difference between the frequency of the transmitting station oscillator 9' which is 500KHz lower
A frequency of 500KHz is obtained and input to the phase comparator 22. On the other hand, the frequency of the 10MHz highly stable reference oscillator 18 is divided by a frequency divider 23 with a frequency division ratio of 1/20 to generate a highly stable 500KHz, and the 500KHz from the mixer 21 is generated.
The frequency of the voltage-controlled transmitting station oscillator 9' is controlled so as to match the phase of the transmitting station oscillator 9'. As a result of the above, both the intermediate frequency and the frequency of the transmitting station oscillator 9' are semi-refined, and therefore the transmission frequency is also semi-refined.

In this case, even if the frequencies of the receiving station oscillator 8' and the transmitting station oscillator 9' change depending on the relay device, the control circuit for semi-refining them does not change.

However, in order to ensure the quality of the received radio waves, the receiving station is sometimes installed at a point where the electric field of the master station's radio waves is strong, and the transmitting station is sometimes installed at a point away from the receiving station to reduce the fog of the own station's transmitted radio waves. In this case, this system has the drawback that the cable between the transmitting station and the receiving station becomes long, making it unstable and unusable. The above explanation was based on the case without offset, but in order to relay the same channel in the same area, in the case with offset which is shifted by ±10.01KHz from the channel frequency, the frequency from mixer 16 is shown in Fig. 1.
250KHz±10.01KHz and mixer 2 in Figure 2
Since the output frequency from 1 is 500KHz±10.01KHz, both are 10MHz high stability reference oscillators 15 and 1.
8 frequency to 250KHz±10.01KHz or 500KHz±
The frequency is divided to 10.01KHz and the transmitting station oscillator 9,
Although the frequency of 9' is controlled, it has the same drawback as above.

(c) Purpose of the Invention The purpose of the present invention is to eliminate the above-mentioned drawbacks and to provide a transmission frequency control system that can be used as is even if the transmitting station and receiving station are far apart and the transmitting video frequency of the relay broadcasting device is changed depending on the television channel. It is provided by.

(d) Structure of the Invention In order to achieve the above object, the present invention divides the transmitting station oscillation frequency of a television relay broadcasting device and the frequency of a highly stable reference oscillator, and calculates the difference frequency between the high-order multiplication wave of this frequency. , by utilizing the fact that the difference from the intermediate frequency (17.75MHz) must always be constant at a certain frequency, the deviation in the intermediate frequency is covered by changing the frequency of the transmitting station oscillator, and the transmitted video frequency is stabilized. Characterized by measurement.

(e) Embodiment of the invention An embodiment of the invention will be described below with reference to the drawings.

FIG. 3 shows a block diagram of a circuit of a transmitting frequency control system for controlling the frequency of the transmitting station oscillator to cover the deviation of the intermediate frequency according to the embodiment of the present invention.

Components in the figure that have the same functions as those in FIGS. 1, 2, and 2 are indicated by the same symbols.

30 is a bandpass waver that passes an intermediate frequency of 17.75MHz, 31 is a limiter, 32, 35, and 40 are mixers, 34 is a bandpass waver for a band of 17.25MHz±10.01KHz, 36 is a 9x multiplier, and 37 is a bandpass waver that passes an intermediate frequency of 17.75MHz. 750±
A low frequency filter that passes 10.01KHz, 38 is a frequency division ratio of 1/
3 is a frequency divider, 39 and 41 are phase comparators, 42 is a frequency divider with a frequency division ratio of 1/2997, SW is a switch, a,
b, c, and d indicate switching terminals.

The amplitude-modulated reception frequency received by the antenna 1 is amplified by the high frequency amplifier 2, and mixed with the frequency from the reception station oscillator 8 composed of a crystal oscillator by the mixer 3 to make it an intermediate frequency and increase the intermediate frequency. It is amplified by the amplifier 4 and mixed with the frequency of the voltage-controlled transmitting station oscillator 9' by the mixer 5 to produce a transmission video frequency modulated with a predetermined amplitude, and the power is amplified by the power amplifier 6. It is transmitting via antenna 7.

At this time, the frequency of the output of the transmitting station oscillator 9' is input to the mixer 21, and the frequency of the highly stable reference oscillator 18 of 10MHz is divided by the frequency divider 19 with a frequency division ratio of 1/5, resulting in a highly stable 2MHz. is generated and input to the high-order multiplication wave generator 20, which generates high-order multiplication waves at 2MHz intervals, and input to the mixer 21.
500K difference from the frequency of the lower transmitting station oscillator 9' in Hz
A frequency of Hz is obtained and the mixer 3 is passed through a low frequency generator 33.
Enter 2. On the other hand, the intermediate frequency (17.75 MHz) is taken out from the output of the intermediate frequency amplifier 4 and inputted to the mixer 32 via the band pass waver 30 and limiter 31, and the difference frequency 17.25 MHz is taken out through the pass band wave generator 34. , is input to the mixer 35.

On the other hand, the output of the frequency divider 19 with a frequency division ratio of 1/5 is 2M.
Hz frequency is multiplied by 9x multiplier 36 to 18MHz
Obtain the frequency of , input it to the mixer 35, take out the difference frequency of 750KHz via the low-pass wave generator 37, divide it by the frequency divider 38 with a frequency division ratio of 1/3, obtain the frequency of 250KHz, and compare the phases. input into the device 39. On the other hand
The frequency of the 10MHz highly stable reference oscillator 18 is obtained by a frequency divider 26 with a division ratio of 1/40 to obtain a highly stable 250KHz frequency, which is input to the phase comparator 39. A phase comparator 39 compares the phase with the 250 KHz frequency and controls the frequency of the voltage-controlled transmitting station oscillator 9' so that they match. As a result, the frequency of the transmitting station oscillator 9' and the frequency of the highly stable reference oscillator 18 of 10 MHz are divided, and the 500 KHz frequency obtained from this high-order multiplication wave (output of the low-frequency wave generator 33) and the intermediate frequency are divided. The difference frequency (output of the bandpass wave generator 34) becomes constant. Therefore, if the intermediate frequency becomes somewhat lower due to, for example, a frequency fluctuation of the receiving station oscillator 8, the frequency of the output of the low frequency converter 33 will also be lowered by the same amount. That is, the frequency of the transmitting station oscillator 9' increases accordingly, and the transmitting video frequency remains constant and is semi-refined. Therefore, with this method, only the transmitting station oscillator 9' is controlled, so there is no problem even if the transmitting station and receiving station are far apart, and semi-refined control is possible even if the TV channel changes and the transmitted video frequency differs. The same circuit can be used.

The above explanation is based on the case without offset, but in the case with offset, turn the switch SW to the offset side, and if the frequency is higher than 10.01KHz, connect the switching terminals a, b, c, and d as shown in the solid line.
If 10.01KHz is low, connect switching terminals a, b, c, and d as shown by dotted lines.

With offset, the difference frequency is 500KHz±
10.01KHz, so the frequency of the output of the bandpass waver 34 is either 17.25MHz±10.01KHz, and the frequency of the output of the frequency divider 38 is 250K.
Either Hz10.01KHz/3. This frequency and the highly stable frequency 250KHz output from the frequency divider 26 are input to the mixer 40, and the difference frequency is 10.01KHz/3.
and the highly stable frequency of 10.01KHz/3 obtained by dividing the frequency of the 10MHz highly stable reference oscillator 18 by the frequency divider 42 with a frequency division ratio of 1/2997. The transmitting station oscillator 9' is controlled by this output so that the phases are compared and the signals are the same.

This allows the transmission frequency to be semi-refined as in the case without offset. Here, switching terminal a,
b, c, d are the same as when the frequency is +10.01KHz.
In the case of 10.01KHz, what is switched is mixer 4 between the output frequency of frequency divider 38 and the output frequency of frequency divider 26.
Switch the input terminal to 0, and from mixer 40
This is to change the direction of increase/decrease in the output voltage of the phase comparator 41 due to an increase/decrease in the frequency of 10.01 KHz/3, thereby changing the direction of frequency control of the transmitting station oscillator 9'.

That is, in the case of +10.01KHz, as the frequency of the mixer 40 increases, the frequency of the transmitting station oscillator 9' will be lowered, and in the case of -10.01KHz, the frequency of the transmitting station oscillator 9' will decrease.
frequency is becoming higher.

As a result, as in the case without offset, the shift in the intermediate frequency can be covered by the transmitting station oscillator 9' and semi-refined.

(f) Effects of the Invention As explained in detail above, according to the present invention, even if the receiving station and transmitting station of the television relay broadcasting device are located at separate locations, even if the television channel changes and the transmitted video frequency changes, the transmission can be continued. Since there is no need to change the transmission frequency control circuit that semi-refines the video frequency, when manufacturing a television relay broadcasting device, it is possible to mass produce, reduce costs, reduce stock, and shorten delivery times.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional method for controlling the transmitting station oscillator by comparing the amplitude-modulated transmitting video frequency and the frequency of a high stability reference oscillator, and Figure 2 is another conventional system for controlling the transmitting station oscillator. FIG. 3 is a block diagram of a circuit of a transmitting frequency control method that controls the frequency of the transmitting station oscillator according to an embodiment of the present invention so as to cover the deviation of the intermediate frequency. be. In the figure, 1 and 7 are antennas, 2 is a high frequency amplifier,
3, 5, 16, 21, 32, 35, 40 are mixers, 4 is an intermediate frequency amplifier, 6 is a power amplifier, 8,
8' is a receiving station oscillator, 9, 9' is a transmitting station oscillator, 10 is a circuit such as a wave generator, 11, 31 is a limiter, 12, 14, 19, 23, 24, 26, 3
8, 42 are frequency dividers, 13, 22, 25, 39, 4
1 is a phase comparator, 15 and 18 are highly stable reference oscillators, 17 and 20 are high-order multiplication wave generators, 36 is a multiplier, 30 and 34 are band-pass wave generators, 33 and 37 are low-pass wave generators, SW indicates switch.

Claims (1)

[Claims] 1. In a heterodyne television relay broadcasting device for amplitude modulated waves that converts the reception frequency to an intermediate frequency and then to the transmission frequency, a high-order multiplication wave of the frequency obtained by dividing the frequency of the transmitting station oscillator and the frequency of the highly stable reference oscillator is used. A transmission frequency control method characterized in that the transmitting station oscillator is controlled so that the frequency obtained by mixing the intermediate frequency and the intermediate frequency become a constant frequency.