JPS60191521A - Multi-channel crystal oscillator - Google Patents

Abstract

PURPOSE:To obtain an optional highly stable oscillating frequency by using a high stable crystal oscillator as a reference oscillator so as to form a PLL and setting properly the frequency dividing ratio of the reference oscillator and of a voltage controlled oscillator. CONSTITUTION:The highly stable crystal oscillator 1, programmable dividers 2, 6, a phase comparator 3, an LPF6 and a voltage controlled oscillator VCXO5 form a PLL. Then the frequency dividing ratio of the dividers 2, 6 frequency dividing respectively the output frequency of the oscillator 1 and the VCXO5 is set in response to the input data from an external memory reader 11. Thus, an optional highly stable oscillating frequency is obtained as an output of the VCXO5 by setting properly the frequency dividing ratio of the divider 2, 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a highly stable crystal oscillator, and more particularly to a multichannel crystal oscillator capable of outputting various frequencies.

[Prior art]

Conventionally, highly stable crystal oscillators such as 10-7 and 10-8, which are housed in a constant temperature bath, have been aged for about one month after being manufactured and before being shipped in order to assess changes over time. However, IMHz is used as a reference for counters, for example.

It is possible to manufacture products with fixed frequencies such as 5MHz and 10MHz early in anticipation of the aging period mentioned above, but it is possible to manufacture products with fixed frequencies such as 5MHz and 10MHz in advance, but it is possible to manufacture products at a fixed frequency such as those used for emitting radio waves in general bases. must make crystal oscillators according to the frequency of each radio wave. For this reason, at present, the crystal resonator is manufactured after the frequency of the radio wave is determined, and after it is incorporated into the oscillator, the aging is checked and shipped. However, there is a tendency that the aging period is not long enough, and maintenance is required after shipment.

This maintenance involves, for example, finely adjusting the frequency using a trimmer capacitor attached to a crystal oscillator.
Such fine adjustment trimmer capacitors are attached to the main body of the thermostatic chamber, and generally the lid of the main body must be opened to make adjustments.To eliminate this hassle, for example, attach a potentiometer externally and adjust from the panel surface. You need to be able to do it. Another drawback was that the crystal oscillator itself would have to be rebuilt if adjustment using a trimmer capacitor, which has a large frequency deviation due to aging, was no longer sufficient. All of this stems from the fact that once the radio wave frequency has been determined, a highly stable crystal oscillator must be created to match it.

[Object and structure of the invention]

The present invention was made in view of these circumstances, and its purpose is to provide high stability at any frequency by using a high stability crystal resonator manufactured in advance without waiting for the desired frequency to be determined. It is an object of the present invention to provide a multichannel crystal oscillator that can obtain an oscillation output and also allows the oscillation frequency to be freely and easily changed after manufacturing.

In order to achieve such an object, the present invention configures a PLL using a highly stable crystal oscillator with a predetermined frequency as a reference oscillator, and a programmable divider that divides the output frequency of the reference oscillator and the voltage controlled oscillator. Means is provided for setting the above-mentioned division ratio in accordance with external input data so that an arbitrary oscillation frequency can be obtained with high stability by appropriately setting the frequency ratio. Hereinafter, the present invention will be explained in detail using Examples.

〔Example〕

The figure is a block diagram showing one embodiment of the present invention. In the figure, 1 is a reference oscillator consisting of a highly stable crystal oscillator using a highly stable crystal resonator 1a, and 2 is a first programmer group that divides the output frequency fref of the reference oscillator 1 by a set frequency division ratio N. divider, 3 is a phase comparator that uses the output of the first programmable divider 2 as the first manual power;
4 is a low-pass filter; 5 is a voltage-controlled oscillator using a crystal resonator 5a; the output of the phase comparator 3 is input to a control terminal via the low-pass filter 4; A second program divider 6 divides the output frequency of the voltage controlled oscillator 5 by a set frequency division ratio N2, and its output becomes the second input of the phase comparator 3. phase comparator net
Output frequency fvc of the voltage controlled oscillator 5 which outputs a difference signal voltage according to the phase difference between the first and second inputs and uses this as a control input.

is the frequency difference f, −
fB shifts in the direction of decreasing, and is eventually fixed at frequencies such as -1, -f, and -0. Note that 1b indicates a capacitor, and 1C indicates a variable capacitor.

In the above configuration, the crystal oscillator 1a of the reference oscillator 1 is manufactured in advance at an appropriate frequency such as IMHz, 5MHz, 10MHz, etc., and the frequency division ratios N 1 + N 2 of the programmable dividers 2 and 6 are set appropriately. As a result, various frequencies can be obtained as the output of the voltage controlled oscillator 5. In this case, even if the crystal resonator 5a of the voltage controlled oscillator 5 is a general type (not highly stable), a stable oscillation output similar to that of the reference oscillator 1 can be obtained due to the PLL configuration.

Here, the frequency division ratio is set as follows.

That is, in the figure, 7 is a timing controller, and 8 is a timing controller.
is a shift register, and 9 and 10 are latte circuits. Each of these circuits and both programmable dividers 2
．． 6 and the phase comparator 3 are composed of one IC. Reference numeral 11 is an external memory reader, and when an external memory such as a magnetic card 12 in which data indicating the frequency division ratio to be set is stored is inserted into a designated insertion slot, the contents are read along with other control bits. It is sent to the timing controller 7 on the clock pulse CLK as 20-bit data DIN. Further, a launch signal LAT is sent out once every 20 clock pulses, and the data input to the shift register 8 is input and stored in the silante circuit 9.10 using this launch signal, thereby completing the setting of the division ratio. In this way, once the latch circuit 9,
After storing the branch location data in 10, the magnetic card is unnecessary and can be removed and stored. If you want to change the output frequency, you can input the change data in the same way using another magnetic card that stores the corresponding division ratio data. This also applies to so-called channel changes and fine adjustments to deal with changes over time. For example, if the matching frequency fA, f is as small as 1/500,000 of the oscillation frequency of the voltage-controlled oscillator 5, the frequency change when changing the division ratio data set in the programmable divider by 1 point is 2X10' or less. This makes it possible to correct changes over time. In particular, the frequency of the reference oscillator 1 can be finely adjusted by the variable capacitor 10. If the variable width of the frequency due to this fine adjustment is ±2X10' or more, all frequencies can be synthesized without gaps, in addition to the above-mentioned minimum pinch that can be changed digitally being ±2X10' or less. In other words, the frequency is digitally changed in the pinch as input data changes, and the gap is filled with the variable width of the reference frequency.

External memory is not limited to magnetic cards; for example, non-volatile ROM in the form of perforated card memory bags (
Any device can be used as long as it can be easily attached to and detached from the external memory reader 11, such as read-only memory). Alternatively, for example, a microcomputer or the like may be connected and the frequency division ratio data may be input from its keyboard.

Of course, the configuration of the circuit that reads the data and sends it to the timing controller 7 together with clock pulses and latch signals also differs depending on each data input form.

In the PLL IC used in this embodiment, data was input in series, but it may be input in parallel, and the present invention imposes no restrictions on the structure of other data.

Incidentally, in such a PLL synthesis method, spurious waves of frequency division waves that inevitably arise from internal synthesis pose a problem. In particular, if the matching frequency is lowered, the spurious will appear near the oscillation frequency and will have a strong influence. Therefore, in this embodiment, a crystal filter 13 is used, and the output of the voltage controlled oscillator 5 is sent to the outside through this filter 13. This filter 1
3 is placed in a constant temperature bath together with the crystal oscillator 1a and the oscillation circuit constituting the reference oscillator 1. By placing it in a constant temperature bath, a filter with a narrow bandwidth can be used and nearby noise can be reduced. Of course, the filter 13 may be connected to a simple open circuit separate from the reference oscillator 1.

〔Effect of the invention〕

As explained above, according to the present invention, a high stability crystal oscillator is used as a reference oscillator to obtain a desired frequency using the PLL synthesis method. It can be made in advance with
While it is possible to create a crystal with good aging characteristics by allowing a sufficient aging period, the crystal resonator for the voltage controlled oscillator, which is manufactured to match the desired radio frequency after determining it, can be of ordinary stability. , a highly stable crystal oscillator with a desired frequency can be easily obtained in a short period of time.

In addition, by setting the division ratio of the programmable divider using external input data, the frequency can be easily changed externally, and channels can be changed or selected by, for example, replacing the magnetic card and inputting the data. By doing this, it is possible to perform various operations freely, the frequency can be easily adjusted, and it is very convenient in terms of maintenance due to changes over time. In particular, in the past, it was difficult to adjust to zero when the frequency adjustment range was wide (for example, ±IOPPM), but according to the present invention, when the frequency is changed by, for example, 2 PPM or more, the external input data can be changed by changing the external input data. Therefore, the fine adjustment width of the frequency of the reference oscillator itself can be narrowed, and zero adjustment can be performed stably. of course,
In this case, by setting the variable width of the reference frequency to at least a variable pinch of the frequency corresponding to one bit of external input data, it is possible to synthesize any frequency with gaps.

Furthermore, by inputting the division ratio that determines the frequency from outside using a magnetic card, for example, even if there is a power outage, you can continue to input data using the same magnetic card after power is restored. This has the advantage that operation can be resumed easily.

[Brief explanation of drawings]

The figure is a block diagram showing one embodiment of the present invention. 1...Reference oscillator, 1a...Highly stable crystal oscillator, 1C...Variable capacitor for fine adjustment, 2.6...
- Programmable divider, 3... Phase comparator, 4... Low pass filter, 5... Voltage controlled oscillator, 5a... Crystal resonator, γ... Timing controller, 8... ...Shift register, 9.
10@... Launch circuit, 11... External memory reader, 12... Magnetic card for inputting frequency division ratio data,
13...Crystal filter for spurious removal Patent applicant Kinseki Co., Ltd. agent Masaki Yamakawa (female or 2 people)

Claims (1)

[Claims] a reference oscillator consisting of a highly stable crystal oscillator with a predetermined frequency;
A first programmable divider that divides the output frequency according to a set division ratio, and outputs a difference signal voltage according to the phase difference between the output of the first programmable divider and the second input. a phase comparator,
a voltage-controlled oscillator that inputs the output of the phase comparator to a control terminal through a low-pass filter and oscillates at a frequency close to the first human power of the phase comparator with respect to the free-running frequency;
a second programmable divider that divides the output frequency of the voltage controlled oscillator according to a set frequency division ratio and outputs the second output frequency of the phase comparator; and means for setting the division ratio of the programmable divider.