JPH066182A - Frequency sweep range controller - Google Patents

Abstract

PURPOSE:To measure the oscillating frequency of a frequency variable oscillator with high accuracy through the use of a low frequency low accuracy frequency measurement device by measuring only a frequency difference between the frequency variable oscillator and a high accuracy frequency oscillator. CONSTITUTION:The oscillating frequency of a frequency variable oscillator 1 is letted be 100MHz+ or -100kHz and the oscillating frequency of a high accurate frequency oscillator 5 is letted be 100MHz+ or -10Hz. When a frequency difference between the oscillators 1, 5 is measured, a frequency as low as nearly 50kHz being the frequency difference of the two oscillators may be measured. Furthermore, the accuracy of the frequency measurement device required for this measurement is enough to be 10Hz/50kHz=200ppm through the measurement with the equal accuracy to that of the oscillator 5. The value 200ppm is easily attained. Moreover, the frequency difference between the oscillators 1, 5 is measured by using frequency dividers 4, 6 as required to attain sweep range control with high accuracy even by a low frequency low accuracy frequency measurement device 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency sweep range control device, and more particularly, to a frequency sweep range control of a local oscillator with high accuracy when sweeping a local oscillator for inputting an intermediate frequency signal to a demodulator for demodulation. The present invention relates to a frequency sweep range control device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, a frequency sweep range control device of this type inputs a received IF signal to a demodulator 2 and controls a frequency variable oscillator 1 which is a crystal oscillation type voltage controlled oscillator (VCXO). The output is phase-detected as a local oscillation signal. The sync signal detector 3 extracts the sync signal from the demodulated signal. If the synchronization is lost, the frequency of the variable frequency oscillator 1 is varied by the frequency controller 20 in order to perform the synchronization pull-in, and the frequency is controlled to be the synchronization pull-in frequency. In this conventional example, the frequency controller 20 controls the oscillation frequency of the variable frequency oscillator 1 without providing an oscillation frequency measuring device for monitoring the frequency of the variable frequency oscillator 1. As another conventional example, as shown in FIG. 3, a frequency divider 4 for dividing an oscillation signal of a frequency variable oscillator 1 by 1 / N (N is an integer of 2 or more) and a highly accurate frequency measuring device 3 are provided.
0 and a sweep range determiner 10 for inputting this frequency measurement information and determining whether or not it is within a predetermined sweep range (see, for example, Japanese Patent Application No. 404033).
Now, as shown in the explanatory diagram defining the sweep range shown in FIG. 4, if f0 ± 50 KHz is the sweep range with respect to the center frequency f0 (for example, 100 MHz), (f0-5
1) KHz or less or (f0 + 51) KHz or more is the sweep prohibited range. The conventional frequency measuring device 30 of FIG.
Is 1 kHz, which is the frequency difference between 50 kHz and 51 kHz
It is necessary to recognize the difference in z, and this 1 kHz is 10
1 kHz / 100 MHz = 10 pp for 0 MHz
Therefore, the measurement accuracy of the frequency measuring device 30 is 10
About twice as high as 1 ppm is required.

[0003]

In the conventional frequency sweep range control device shown in FIG. 2 described above, a VCXO normally used as a local oscillator of a demodulator has a prescribed sweep range A as shown in FIG. , The oscillation frequency can be changed by changing the voltage to which the control voltage of the VCXO is applied from the outside, but the accuracy for changing the frequency is poor, and the temperature change and the secular change of the oscillation frequency are large (B1 in FIG. 5). ~ B2), input voltage (control voltage)
It is technically impossible to make the relationship between the output and the oscillation frequency as the output unique. Furthermore, since there is no frequency measuring means for recognizing frequency changes due to temperature changes and aging changes, the frequency control voltage of the variable frequency oscillator will be swung within a certain range, while the exact oscillation frequency remains unknown.
It is impossible to accurately determine the actual frequency sweep range.

Next, in the frequency controller as shown in FIG. 3, the frequency sweep range can be accurately determined, but for that purpose, there is a drawback that the frequency measuring device is required to have high accuracy.

An object of the present invention is not to directly measure the frequency of the variable frequency oscillator, but to control the frequency sweep range of the demodulator accurately even with a low frequency and low precision frequency measuring instrument. To provide a device.

[0006]

A frequency sweep range control device of the present invention comprises a demodulator for receiving and demodulating a received IF signal, a variable frequency oscillator capable of moving or sweeping a frequency by a control voltage from a control terminal, A synchronization signal detector that detects a synchronization signal in the received IF signal from the demodulator output, a high-precision frequency oscillator with high frequency accuracy, and the frequency variable oscillator output and the output of the high-precision frequency oscillator are mixed to obtain a difference. A mixer that outputs a frequency signal, a low-frequency filter that extracts the difference frequency signal, a low-frequency frequency measuring device that measures the output frequency of the low-frequency filter, and a low-frequency frequency measuring device The measured value is a sweep range determiner for determining whether it is within the sweep frequency range, the determination result of the sweep range determiner, and the output based on the output of the synchronization signal detector. And a frequency controller for supplying a control voltage to the control terminal of the wave number variable oscillator.

[0007]

According to the present invention, instead of directly measuring the oscillation frequency of the variable frequency oscillator with the frequency measuring instrument, by measuring only the frequency difference between the variable frequency oscillator and the highly accurate frequency variable oscillator, the low frequency low precision Even if the frequency measuring device is used, it is possible to realize accurate control of the sweep frequency of the demodulator with the same accuracy as that of the high-precision frequency oscillator.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention. Figure 1
In the embodiment, a frequency variable oscillator 1 such as a VCXO, a demodulator 2 that demodulates a received IF signal by using the output of the frequency variable oscillator 1 as a local frequency, and a synchronization signal that detects a synchronization signal from the received signal that is the output of the demodulator 2 The detector 3, the frequency divider 4 for dividing the output of the variable frequency oscillator 1 by 1 / N, the high precision frequency oscillator 5 with high frequency precision, and the output of the high precision frequency oscillator 5 are 1 / M (M is an integer of 2 or more). ) Dividing frequency divider 6,
The mixer 7 that multiplies the outputs of the frequency divider 4 and the frequency divider 6 and outputs the result to the low-pass filter 8, the frequency divider 4 of the outputs of the mixer 7.
Low-pass filter (LPF) 8 for extracting only a component that is an output difference between the frequency divider 6 and the frequency divider 6, a low-frequency low-precision frequency measuring instrument 9 for measuring the frequency of the output of the LPF 8, a low-frequency low-precision frequency measuring instrument 9 The sweep range determiner 10 that determines whether the oscillation frequency of the variable frequency oscillator 1 is within the sweep range based on the measured value of 1 and the sync signal detector 3 does not detect the sync signal. The frequency controller 11 controls the frequency of the variable frequency oscillator 1 based on the result of the frequency controller 10. The frequency divider 4 and the frequency divider 6 may be inserted only when necessary.

Next, the operation of this embodiment will be described. The oscillation frequency of the variable frequency oscillator 1 is 100 MHz ± 100 kHz
And the oscillation frequency of the high precision frequency oscillator 5 is 100 MHz.
When the sweep range is set to z ± 10 Hz and the sweep range is set to ± 50 kHz or more and 51 kHz or less as described in FIG. 4, the frequency measuring device needs to recognize the difference between 100.050 MHz and 100.051 MHz as described above. Therefore, the accuracy of the frequency measuring device is required to be about 1 ppm. Now, when measuring the frequency difference between the variable frequency oscillator 1 and the high-precision frequency oscillator 5, the frequency measuring device only needs to be able to measure a low frequency of about 50 kHz, which is the frequency difference between the two oscillators. Further, the accuracy of the frequency measuring device required at that time is 10 Hz / 50 kHz = 200 even if it is measured with the same accuracy as the high accuracy frequency oscillator 5 exemplified in the conventional example.
ppm is sufficient. This value of 200 ppm can be easily achieved, considering that even the most inaccurate crystal oscillator is usually ± 100 ppm. By measuring the frequency difference between the variable frequency oscillator 1 and the high-precision frequency oscillator 5 using the frequency dividers 4 and 6 as necessary, the low-frequency low-precision frequency measuring instrument 9 can also perform highly accurate sweep range control. Becomes

[0010]

As described above, according to the present invention, by measuring only the frequency difference between the variable frequency oscillator and the high precision frequency oscillator with the frequency measuring instrument, the high precision frequency can be obtained even if the measurement accuracy of the frequency measuring instrument is low. It is possible to perform measurement with the same measurement accuracy as that of the oscillator, and it is possible to perform accurate frequency sweep range control using the measurement result.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional frequency sweep range control device.

FIG. 3 is a block diagram showing another example of a conventional example.

FIG. 4 is an explanatory diagram of a sweep range common to this embodiment and a conventional example.

FIG. 5 is an explanatory diagram showing characteristics of a conventional example.

[Explanation of symbols]

 1 frequency variable oscillator 2 demodulator 3 synchronization signal detector 4, 6 frequency divider 5 high precision frequency oscillator 7 mixer 8 low pass filter (LPF) 9 low frequency low precision frequency measuring instrument 10 sweep range determiner 11, 20 Frequency controller 30 Frequency measuring instrument

Claims (3)

[Claims] 1. A demodulator for receiving and demodulating a received IF signal, a frequency variable oscillator capable of moving or sweeping a frequency by a control voltage from a control terminal, and a sync signal in the received IF signal detected from the output of the demodulator. A synchronization signal detector, a high-precision frequency oscillator with high frequency accuracy, a mixer for mixing the output of the variable frequency oscillator and the output of the high-precision frequency oscillator to output a difference frequency signal, and extracting the difference frequency signal A low-frequency filter, a low-frequency frequency measuring device that measures the output frequency of the low-frequency filter, and a measurement value of the low-frequency frequency measuring device, it is determined whether or not within the sweep frequency range A sweep range determiner, and a frequency control that supplies a control voltage to the control terminal of the frequency variable oscillator based on the determination result of the sweep range determiner and the output of the synchronization signal detector. A frequency sweep range control device having a controller. 2. A frequency divider that divides the oscillation frequency of the variable frequency oscillator before the mixer input, and a divider that divides the oscillation frequency of the high-precision frequency oscillator. The frequency sweep range control device according to claim 1. 3. The sweep frequency swing width is Δf, and the sweep output frequency of the variable frequency oscillator is f1 ± Δf.
And the frequency of the high-precision frequency oscillator output is f2, the measurement accuracy of the frequency measuring device for measuring the difference frequency between (f1 ± Δf) and f2 is 200 ppm with respect to Δf.
The frequency sweep range control device according to claim 1, wherein the frequency sweep range control device is set within the range.