JPS6345546B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for generating marker signals used for frequency adjustment and measurement of various devices such as FM receivers and television receivers.

There are various ways to generate a marker signal. One of them is to use a beat signal of a sweep frequency signal and a reference signal, create a pulse with an appropriate width before and after the zero beat point of the signal, and use this pulse as a marker signal. There are some that are designed to serve as signals. However, because this marker signal has a wide pulse width, it may be difficult to know which part of the pulse is the correct marker frequency, or it may become wider or narrower as the pulse width, sweep width, or sweep speed of the marker signal changes. However, there was also the problem that it was not possible to confirm the correct marker frequency position.

The present invention relates to a method for generating a marker signal that does not have such difficulties, and involves creating a beat signal using a reference frequency signal and a sweep frequency signal, finding the zero beat point of the beat signal, and generating a marker signal at that position. This is what I did. An example of the present invention will be described in detail below based on the drawings.

The invention set forth in claim 1 is a method for generating a marker signal at only one point, and the invention set forth in claim 3 is a method for generating a marker signal at two or more points. be.

The former method is as follows.

A sawtooth wave with good linearity (Fig. 3) oscillated from the sawtooth wave oscillator 1 is input into the sweep oscillator 2, and the sweep frequency signal shown in Fig. 3 whose frequency changes in proportion to the level of the sawtooth wave (hereinafter simply referred to as a sweep signal) is generated. ) and put it into mixer 3. A reference frequency signal (hereinafter simply referred to as the reference signal) from the reference signal oscillator 4 is also input to the mixer 3, and this causes the output of the mixer 3 to be around the zero beat point f _c (this position is actually unknown). A beat signal (Figure 3) is obtained.

In the present invention, the position of the zero beat point (f _c in FIG. 3) of this beat signal is determined, and then a marker signal is generated at this zero beat point f _c .

Therefore, in the illustrated embodiment, the beat signal shown in FIG. 3 is shaped by an amplifier 5 and then input to a frequency comparator 8 consisting of a one-shot multivibrator 6 and a flip-flop circuit 7, which can be retriggered. This frequency comparator 8 can freely select the frequency f _l to be compared by adjusting the volume VR shown in _FIG . Determine whether it is low,
When the beat frequency f matches the set frequency _fl , the logic output from the output terminal Q changes as follows. The logic output is "0" in the region of the beat frequency f that is higher than the set frequency f _l of the frequency comparator 8 (f > f _l ), and the logic output is "0" in the lower frequency region f < f _l (between f _L and f _u in Figure 3). Output "1" is obtained from the output terminal, and the opposite logic output is obtained from the Q output terminal, that is, logic "1" when f > f _l , f < f _l (f _L ~ f _u in Fig. 3). A logic output of logic "0" is obtained between (between).

Therefore, the rectangular wave shown in FIG. 3 is obtained from the output terminal of the frequency comparator 8, and the rectangular wave shown in FIG. 3 is obtained from the Q output terminal.

In the present invention, these two rectangular waves are input into differentiating circuits 9 and 10 shown in FIG. 1, and the rising edges of each rectangular wave are differentiated to obtain the pulses shown in FIG. 3. Furthermore, these two pulses are input to the sample and hold circuits 11 ₁ and 12 ₁ via the switch 18, and the level E ₁ at the time when the sawtooth wave (Fig. 3) matches these two pulses (Fig. 3, ) is set. , E ₂ to obtain the hold signal shown in Figure 3. These two hold signals are input into the average value circuit 13 to obtain the average value level E ₁ +E ₂ /2 (FIG. 3) of both levels.

Furthermore, this average level signal and the sawtooth wave (Fig. 3) are input to the voltage comparator 14, the average level and the sawtooth wave level are compared, and the point at which both match (zero beat point) f _c is determined. , the logic output is "1" at this zero beat point, and a rectangular wave whose logic output is "0" is obtained when the level of the sawtooth wave becomes zero (FIG. 3). This rectangular wave is input into a differentiating circuit 15, and its rising edge (zero beat point) is differentiated to produce the pulse shown in FIG. 3, which is used as a marker signal.

Next, the invention of claim 3 is accomplished as follows.

The method of generating the marker signal itself is exactly the same as the invention of claim 1, but since two or more markers with different frequencies are generated simultaneously, the sample and hold circuits 11 and 12 and the average value circuit 13, Voltage comparator 14, differentiation circuit 15
Prepare as many markers as you want to generate, and connect them in parallel to differentiating circuits 9 and 10 as shown by imaginary lines in FIG. Furthermore, the number of marker frequency setters 16 is also increased by the increased number. Then, the marker frequency setters 16 ₁ , 16 ₂ , 16 ₃ are switched by the switch 17 every time the sweep signal is swept to change the reference signal that becomes the marker signal frequency, and the switch 18 is used to switch the reference signal shown by the virtual line in FIG. Hold circuit 11
The various circuits after ₁ and 12 ₁ are also switched, thereby generating a marker signal at the zero beat point f _c corresponding to the reference signal generated each time the switch is made.

The switchers 17 and 18 are switched at every sweep by a sawtooth wave (FIG. 3), and the marker frequency setter 16 ₁ corresponds to the sample and hold circuits 11 ₁ and 12 ₁ , and the switch 16 ₂ corresponds to the 11 _2,1
2 ₂ and 16 ₃ are linked and switched in correspondence with 11 ₃ and 12 ₃ , respectively.

In this way, each marker signal generated for each sweep is sent to the sample and hold circuits 11 ₁ , 12 ₂ ,
11 ₂ , 12 ₂ , 11 ₃ , 12 ₃ continues to be held, so once it is generated, it does not disappear. Therefore, each time the marker frequency setters 16 ₁ , 16 ₂ . . . are switched, two or more marker signals with different frequencies are generated. appear at the same time.

As described above, in the present invention, the beat signal shown in FIG. 3 is input into the frequency comparator 8, and two points before and after the zero beat point f _c of the beat signal (points f _L and f _u in FIG. ) and find the average value of the sawtooth wave level at these two points to find the zero beat point f _{c. Therefore, the zero beat point f c can} be found regardless of changes in the sweep speed or sweep width of the sweep signal. can be determined accurately.
Moreover, since the marker signal is generated at this zero beat point f _c , the generation point is always constant, and since the marker signal is sharp with almost no pulse width, the marker frequency must be adjusted when using it. This allows for accurate confirmation and, in turn, highly accurate adjustment.

Further, according to the present invention, the circuit configuration for implementing the present invention is simpler than that of conventional circuits of this type, so that the present invention is easy to implement and inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a block explanatory diagram showing an example of the present invention;
FIG. 2 is an explanatory diagram showing an example of a frequency comparator constituting the present invention, and FIG. 3 is a waveform explanatory diagram showing the operating state of the present invention. 1 is a sawtooth wave oscillator, 4 is a reference signal oscillator,
6 is a one-shot multivibrator capable of retriggering, 7 is a D-type flip-flop circuit, 8 is a frequency comparator, and 16 ₁ , 16 ₂ . . . are marker frequency setters.

Claims (1)

[Claims] 1. A beat signal consisting of a sawtooth sweep frequency signal and a reference signal is input into a frequency comparator, and a logic output of "0" or "1", logic output "1" which is opposite to the previous logic output in a frequency region higher than the set frequency
Or obtain a rectangular wave that is “0” and a rectangular wave whose logical outputs “0” and “1” are opposite to the rectangular wave,
The level of the sawtooth wave is sampled and held at two points, the rise or fall of each rectangular wave, and the average level at both points is determined. This average level is compared with the sawtooth wave to determine the level of the sawtooth wave. Marker signal generation in which a zero beat point that matches the average value level is found, a rectangular wave that rises or falls at the zero beat point is formed, and a marker signal is generated at the zero beat point by differentiating the rise or fall of this rectangular wave. Method. 2. The marker signal generation method according to claim 1, wherein the frequency comparator is composed of a retriggerable one-shot multivibrator and a D-type flip-flop circuit. 3. Put the beat signal of the sawtooth wave sweep frequency signal and the reference signal into a frequency comparator, and in the frequency region of the beat signal that is lower than the set frequency of the frequency comparator, the logic output is "0" or "1", and the set frequency is Logic output "1" which is the opposite of the previous logic output in the higher frequency range
Or obtain a rectangular wave that is “0” and a rectangular wave whose logical outputs “0” and “1” are opposite to the rectangular wave,
Sample and hold the level of the sawtooth wave at two points, the rise or fall of each square wave, find the average level at both points, and compare this average level with the sawtooth wave to find out that the level of the sawtooth wave is the average. A marker signal that determines a zero beat point that matches the level of a value, forms a rectangular wave that rises or falls at the zero beat point, and differentiates the rising or falling point of this rectangular wave to generate a marker signal at the zero beat point. In the generation method, the frequency of the reference signal is switched every time a sweep is made to generate a marker signal with a different frequency each time, and each generated marker signal is held to simultaneously generate two or more marker signals with different frequencies at multiple points. A method of generating a marker signal to obtain a marker signal. 4. The marker signal generation method according to claim 3, comprising a one-shot multivibrator whose frequency comparator can be retriggered and a D-type flip-flop circuit.