JPH03249814A - Frequency error detector and circuit adjuster using this detector - Google Patents

Abstract

PURPOSE:To improve error detecting precision by sampling a driving voltage in the band of a waveform outputted from a waveform shaping means, and detecting an error between the sampled voltage and a voltage being a reference. CONSTITUTION:Signals different in frequencies are outputted from a voltage control oscillation means 2 in accordance with the change of the driving voltage, and they are inputted to circuit 3 under test. An output where the frequencies of a tuning output as against the input signal is distributed in constant can be obtained from the circuit 3 under test. The waveform shaping circuit 6 obtains the shaped waveform obtained by peak-holding the output by a prescribed output value and the driving voltage is sampled based on the shaped waveform. Thus, the error of the band width of the frequency in the output from the circuit 3 under test is obtained by comparing the sampled voltage with the voltage being the reference. Thus, error detection precision is improved.

Description

[Detailed description of the invention]

[Industrial Application Field J] The present invention relates to a frequency error detection device for detecting a frequency error in a frequency distribution output output from a tuning circuit or a filter, and a method for adjusting the tuning frequency of a tuning circuit or filtering using this error detection device. The present invention relates to a circuit adjustment device that can automatically adjust the passing frequency characteristics of a circuit. [Prior Art] FIG. 9 shows a conventional device for adjusting a variable capacitor for trimming an RF circuit of an AM tuner. This adjustment device adjusts a variable capacitor so that the AM tuner output is maximized for a predetermined receiving frequency. In this device, the AM signal input section 15 has an AM signal for adjustment.
The flaw signal is input to the AM tuner 3 to be adjusted. The output tuned by the AM tuner 3 is measured by the level meter 16, and the measurement information is input to the control section 17. In this control section 17, control information is created based on the measurement information, the driver bit and driver drive circuit 5 are driven, the variable capacitor 4 is automatically adjusted,
The tuning output of the AM tuner is automatically adjusted to the maximum for a predetermined reception frequency. [Problem to be Solved by the Invention] However, in the conventional adjustment device described above, adjustment is made such that the output is maximized at the desired reception frequency f0 shown in FIG. ), there is no problem if the passband characteristics of the AM tuner 3 ensure the same bandwidth Δf on both sides of the frequency f0, but (B) or (C) in FIG. As shown in Figure 2, when there is distortion in the characteristics of the tuning circuit, it is impossible to detect the deviation of the passband on the negative side and the positive side of the frequency with respect to the desired frequency f0, resulting in a decrease in adjustment accuracy. be. Furthermore, when determining the frequency error with respect to the output from a double-tuned circuit as shown in FIG. 7, there are multiple peak values, so it is not enough to simply measure the peak value with the device described above.
It is difficult to accurately understand the tuning characteristics. The present invention solves the above-mentioned conventional problems.The present invention obtains a waveform having a peak at a predetermined output value for the output from the circuit under test, and detects the frequency error using this as a reference, thereby determining the frequency distribution. It is an object of the present invention to provide a frequency error detection device capable of detecting an error in characteristics of a detected circuit and adjusting the circuit even when a bias occurs, and a circuit adjustment device using this error detection device. [Means for Solving the Problems] A frequency error detection device according to the present invention includes a driving voltage generating means whose voltage changes with time, and a voltage that outputs a signal of a frequency corresponding to the driving voltage to a circuit under test. a controlled oscillation means; a waveform shaping means for peak-holding and waveform-shaping the frequency distribution output output from the circuit under test at a predetermined output value; and a waveform shaping means for shaping the frequency distribution output from the circuit under test; It has means for sampling voltage and means for detecting an error between the sampled voltage and a reference voltage. Further, the circuit adjustment device according to the present invention includes a driving voltage generating means whose voltage changes with time, a voltage controlled oscillation means which outputs a signal of a frequency corresponding to the driving voltage to a circuit under test, and a circuit under test. waveform shaping means for peak-holding and waveform-shaping the frequency distribution output output from the waveform shaping means at a predetermined output value; means for sampling the drive voltage in a band of the waveform output from the waveform shaping means; The test circuit has a means for detecting an error between a reference voltage and a reference voltage, and an adjusting means for automatically adjusting the output frequency distribution of the circuit under test so as to eliminate the error in the voltage. Furthermore, the circuit adjustment device according to the present invention includes, in the above means, a waveform shaping means that peak-holds the frequency distribution output output from the circuit under test at a plurality of different output values and shapes the waveform of each, and an output from the waveform shaping means. means for sampling the driving voltage in each waveform band, means for detecting an error between each sampled voltage and a reference voltage, and means for detecting an error between each sampled voltage and a reference voltage, and It has an adjusting means for automatically adjusting the output frequency distribution of the circuit. [Operation j] In the above means, signals of different frequencies are output from the voltage controlled oscillation means in accordance with changes in the drive voltage, and these are input to the circuit under test. An output having a predetermined distribution of frequencies, such as a tuned output with respect to the input signal, is obtained from the circuit under test. A shaped waveform is obtained by peak-holding this output at a predetermined output value, and the drive voltage is sampled based on this shaped waveform. By comparing this sampled voltage with a reference voltage, the 6-circuit adjustment device obtains the error in the frequency bandwidth of the output from the circuit under test. Gilling of variable capacitors, etc. is performed. Furthermore, by comparing the shaped waveforms with peaks at a plurality of output values from the outputs of the circuit under test, the frequency error can be detected and the circuit can be adjusted with high precision. [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a frequency error detection device for an AM tuner and a circuit adjustment device using the same according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a drive voltage generation circuit, and the drive voltage generation circuit 1 outputs a sawtooth drive voltage shown in (A), which is input to the voltage controlled oscillation circuit 2. From the voltage controlled oscillation circuit 2, the drive voltage (a)
A frequency output (b) in a constant band whose oscillation frequency changes in a sweeping manner in response to changes in is obtained, and this is input to the AM tuner 3, which is the circuit under test. In the AM tuner 3, the input frequency output (b) is connected to the variable capacitor 4.
It is tuned by a tuning circuit including a tuning circuit, and its tuning output (c) is obtained. This tuned output (c) is input to the waveform shaping circuit 6. The waveform shaping circuit 6 generates a pulse output (d) obtained by shaping the tuned output (c). The error detection circuit 7 detects a frequency error from the waveform-shaped pulse output (d) and the drive voltage (a). The voltage (Q) based on this error drives the driver bit and the driver drive circuit 5, and the variable capacitor 4 of the tuning circuit of the AM tuner 3 is automatically adjusted. FIG. 2 shows a specific configuration of the waveform shaping circuit 6. The waveform shaping circuit 6 includes a peak hold circuit 8 and an attenuator 9.
and a comparator 10. This waveform shaping circuit 6
Here, the peak value (maximum output value) of the tuned output (c) from the AM tuner 3 is held by the peak hold circuit 8. *The display device 9 determines the level of the passband, and is set to an output value that is a predetermined level [-NdB] lower than the peak value. And the output of attenuator 9 and AM
The tuned output (c) from the tuner 3 is compared by the comparator 10, and a shaped pulse output having a bandwidth shown in (d) is obtained. FIG. 4 shows a specific configuration of the error detection port N7. This error detection circuit 7 includes a sample circuit 11. Integrating circuit 1
2. It has sample/hold circuits 13 and 14. In the sample circuit 11, the sawtooth drive voltage (A) is sampled by the pulse output (D) from the waveform shaping circuit 6, and a part of the drive voltage (A) corresponding to the bandwidth of the pulse output (D) is being extracted. This extracted waveform is shown as (E) in FIG. 5. This extracted waveform (E) is integrated by the integrating circuit 12. The integrated waveform in FIG. The peak value of the signal (such as α or β in FIG. 5) is sampled and held. More samples/
The hold circuit 14 holds the voltage at level α or β, and this becomes the error voltage (ch) corresponding to the frequency error.
As shown in FIG. 1, this error voltage (chi) is input to the driver bit and driver drive circuit 5,
The error voltage (chi) is a predetermined voltage (0 in the example shown)
The variable capacitor 4 in the AM tuner 3 is adjusted so that This adjustment work is performed by driving a motor provided in the driver bit and the driver drive circuit 5 in accordance with the error voltage (Q), and rotating the variable capacitor 4 by this motor. Next, the overall operation of the first embodiment will be explained. FIG. 5 shows the output signal waveforms of each part in the block diagram shown in FIG. Indicates when Also (B)
(C) shows the case where the tuned output (C) has a frequency error on the minus side, and (C) shows the case where there is a frequency error on the plus side. The driving voltage generating circuit 1 generates a sawtooth driving voltage as shown in (A), which is input to the voltage controlled oscillation circuit 2. This driving voltage (A) is a sawtooth voltage whose voltage becomes zero at the desired frequency f0 to be tuned by the tuning circuit of the AM tuner 3. The voltage controlled oscillation circuit 2 obtains an output (b) of a frequency in a certain band corresponding to each of the drive voltages (a), and this is outputted from the voltage controlled oscillation circuit 2 to the AM tuner 3. A tuned output (C) as shown in (C) is obtained by the tuning circuit of the AM tuner 3. In the waveform shaping circuit 6, the second
The peak hold circuit 8 shown in the figure holds the output value -N dB from the peak value of the tuned output (c).
A pulse output as shown by (d) in FIG. 3 is obtained from the comparator IO. In the error detection circuit 7, the sawtooth drive voltage (A) is sampled by the pulse output (D) by the sample circuit 11 shown in FIG. A waveform (e) is formed by extracting a part of the drive voltage in the bandwidth of the output pulse (d). As shown in Figure 5 (A),
When the band center of the tuned output (C) matches the desired frequency f, the output (E) has a waveform that spans negative and positive frequencies, and in (B), the output (E) has a waveform that spans the negative and positive frequencies. It becomes a negative voltage that shifts toward the frequency side. Further, in (C), the output (E) becomes a positive voltage shifted to the positive frequency side. Then, it is integrated by the integrating circuit 12, and sampled/held by the sample/hold circuits 13 and 14.
When held, the error voltage (h) shown in the bottom row of FIG. 5 is obtained. As shown in (A), when the tuning frequency matches the desired frequency f0, the error voltage (chi) becomes Ov. Also(
As shown in B), when the tuning output (C) is shifted to the negative side, the tuning voltage (H) becomes a negative voltage. Also, as in (C), when the tuning output (C) is shifted to the positive side. The output (H) becomes a positive voltage. In (B) and (C), error voltages that are shifted to the negative or positive side with respect to the voltage (Ov) in (A) are obtained. This error voltage (ch) is input to the driver bit and driver drive circuit 5, the motor is driven according to the error voltage, the motor in the AM tuner 3 is driven, the variable capacitor 4 is varied, and the tuning frequency output is is automatically adjusted so that it becomes (A) in FIG. In the above embodiment, from the peak output value of the tuning output (c) -
Peak hold is performed by the output value decreased by N dB (
A pulse output shown in (d) is obtained, a sawtooth drive voltage is extracted in that bandwidth, and the frequency error is determined based on this. Therefore, compared to an adjustment in which the maximum output value of the tuning frequency simply matches the desired frequency f0, as in the conventional example shown in Fig. 1O, the bandwidth to be sampled in the adjustment is widened, making it possible to perform highly accurate tuning adjustment. Become. Further, by using the frequency error detection device and circuit adjustment device, it becomes possible to detect frequency errors in a double-tuned circuit and adjust the circuit. This embodiment is shown in FIGS. 6 and 7. As shown in the block diagram of FIG. 6, this device is provided with two waveform shaping circuits 6a and 6b. Further, the outputs from the respective waveform shaping circuits 6a and 6b are sent to two error detection circuits 7a.
and 7b, the respective waveform shaping circuits 6a and 6
The specific circuit in b is the same as that shown in FIG. However, in the peak hold circuit of one waveform shaping circuit 6a, the pulse output is peak held at an output value that is a predetermined level lower (-N. dB) from the peak value of the tuned output (c) from the AM tuner 3. (See (knee l) in FIG. 7). In the other waveform shaping circuit 6b, a peak-held pulse output (knee 2) is obtained at an output value that is (-N, dB) lower than the peak value of the tuned output (c). Further, the specific circuits of the error detection circuits 7a and 7b&:8 are the same as those shown in FIG. In one error detection circuit 7a, a sawtooth drive voltage is sampled and extracted by a sample circuit according to the bandwidth of the waveform of the pulse output (knee l), and a waveform output shown by (ho 1) is obtained. Then, an error voltage (Chi 1) is outputted by the integrating circuit and sample/hold circuit in the error detection circuit 7a. In the other error detection circuit 7b, the drive voltage is sampled by the sampling circuit according to the bandwidth of the shaped waveform shown by the pulse output (knee 2), and a waveform output shown by (ho 2) is obtained, which is integrated and sampled. /Holded,
An error voltage (Qi 2) is output. In the driver bit and driver drive circuit 5, separate motors are driven by the two types of error voltages (Chi 1) and (Chi 2),
Variable capacitors 4a, 4 of the double tuning circuit of the AM tuner 3
b are adjusted respectively. By automatic adjustment of each variable capacitor 4a, 4b, (Chi 1) and (Chi 2)
) is adjusted so that the error voltage V becomes zero. In this embodiment, the drive voltage is sampled using a shaped waveform that holds the peak value using two output values -N, dB and -N, dB as references, and thereby obtains the error voltage. Even with a double tuning waveform having a plurality of peak values as shown in (c) in FIG. 7, it is possible to tune the tuning output of the AM tuner 3 to the desired frequency f0. Furthermore, using the frequency error detection device and circuit adjustment device, frequency error detection and circuit adjustment in circuits other than the tuning circuit can be performed. FIG. 8 illustrates a case where adjustment of a low-pass filter is performed. That is, in the apparatus shown in FIG.
A low-pass filter is used as the circuit to be tested in place of the tuner 3, and frequency error detection and adjustment of this low-pass filter are performed. The driving voltage generating circuit 1 shown in FIG. 1 generates a sawtooth driving voltage as shown in (A) in FIG. The oscillation output at a frequency of is output to a low-pass filter. The output from this low-pass filter becomes a passing waveform having the characteristics shown in (bar 3) or (bar 4) in FIG. Adjustment of this low-pass filter can be performed using the passed waveform (bar 3) or (bar 4).
) is to match the frequency at a level −N dB lower than the maximum output value of the waveform with the desired frequency f1. Peak hold circuit 8 of the waveform shaping circuit 6 shown in FIG.
, the maximum output value of the waveform that has passed through the low-pass filter is peak-held, and the attenuator 9 reduces the maximum output value to −N.
A dB lower level is set and from the comparator lO (knee 3
) or (knee 4) can be obtained. In the error detection circuit 7a or 7b, the sawtooth drive voltage (a) is sampled by pulse outputs (knee 3) and (knee 4) in the sample circuit 11 shown in FIG. As a result, as shown by (Ho 3) and (Ho 4) in FIG. 8, the driving voltage (A) is extracted in the bandwidth of the pulses (Knee 3) and (Knee 4). By integrating and sampling/holding this extracted waveform, an error voltage shown as (Chi 3) or (Chi 4) is obtained. 8th
Figure (A) shows the passing output from the low-pass filter.
The case where the frequency f+' at -N dB is shifted to the negative side, (B) is the frequency f1 at -N dB.
This shows a case where ゛ is shifted to the plus side. In the case of (A) in FIG. 8, the peak value of the sampled drive voltage is a negative voltage as shown in (Ho-3), and (
In case B), as shown in (Ho 4), the peak value of the sampled drive voltage is a positive voltage. Therefore, in case (A), a negative error voltage indicated by (Chi 3) is output from the error detection circuit 7, and in case (B), a positive error voltage indicated by (Chi 4) is obtained. The characteristics of the low-pass filter can be known from this error voltage. Furthermore, automatic adjustment of the low-pass filter becomes possible by driving the driver bit and driver drive circuit 5 shown in FIG. 1 to adjust the variable capacitor in the low-pass filter so that the error voltage becomes zero. Note that the filter is not limited to the above-mentioned low-pass filter, and error detection can be performed using various filters. In addition, in the error detection of the filter shown in Fig. 8, -N, dB and -N! from the peak value of the passed output. Two shaped waveforms whose peaks are held at two output values of dB may be formed, and the error voltage may be determined from each shaped waveform. Further, although the illustrated embodiment shows a circuit adjustment device,
By confirming the sampled drive voltage waveform (e) in the image in Fig. 5, or by showing the integrated error voltage (ch) with a voltmeter, etc.
A frequency error detection device can be constructed. This also applies to FIG. 7 or 8.

【effect】

As described above, according to the present invention, the frequency output is detected using a fixed bandwidth or the circuit is adjusted based on this, so the error detection accuracy is higher than in the conventional case where only the peak value is detected. In addition, it becomes possible to improve circuit adjustment accuracy.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a frequency error detection device according to a first embodiment of the present invention and a circuit adjustment device using the same, FIG. 2 is a block diagram specifically showing the circuit configuration of a waveform shaping circuit, and FIG. 3 (A) and (B) are waveform diagrams showing the input and output to the waveform shaping circuit, Figure 4 is a block diagram showing the specific configuration of the error detection circuit, and Figure 5 is each part of the circuit adjustment device of the first embodiment. FIG. 6 is a block diagram showing a frequency error detection device according to the second embodiment of the present invention and a circuit adjustment device using the same, and FIG. 7 shows each part of the circuit adjustment device of the second embodiment. Waveform diagram showing the output of Figure 8 (A) (
B) is a waveform diagram showing the adjustment output in the second embodiment, FIG. 9 is a block diagram showing a conventional circuit adjustment device, and FIGS. 10 (A), (B), and (C) are adjustments in the conventional circuit adjustment device. FIG. 3 is a waveform diagram illustrating the operation. DESCRIPTION OF SYMBOLS 1... Drive voltage generation circuit, 2... Voltage controlled oscillation circuit, 3... AM tuner which is a circuit to be inspected, 5... Driver bit and driver drive circuit, 6... Waveform shaping circuit, 7...Error detection circuit. Figure 6 Figure 8 (B)

Claims (1)

[Scope of Claims] 1. A means for generating a drive voltage whose voltage changes with time, a voltage controlled oscillation means for outputting a signal with a frequency corresponding to the drive voltage to a circuit under test, and a means for generating a drive voltage from which the circuit under test waveform shaping means for peak-holding and waveform-shaping the output frequency distribution output at a predetermined output value; means for sampling the drive voltage in a band of the waveform output from the waveform shaping means; A frequency error detection device 2 having means for detecting an error between a voltage and a reference voltage, a means for generating a driving voltage whose voltage changes over time, and a signal having a frequency corresponding to this driving voltage. voltage-controlled oscillation means for outputting to the circuit under test; waveform shaping means for peak-holding the frequency distribution output output from the circuit under test at a predetermined output value and shaping the waveform; means for sampling the drive voltage in a waveform band; means for detecting an error between the sampled voltage and a reference voltage; and means for automatically adjusting the output frequency distribution of the circuit under test so as to eliminate this voltage error. a circuit adjusting device 3 having an adjusting means for adjusting, a waveform shaping means for peak-holding the frequency distribution output output from the circuit under test at a plurality of different output values and shaping the respective waveforms, and this waveform shaping means. means for sampling the drive voltage in the band of each waveform output from the drive voltage; means for detecting an error between each sampled voltage and a reference voltage; 3. The circuit adjustment device according to claim 2, further comprising adjustment means for automatically adjusting the output frequency distribution of the circuit under test.