JPH0754907B2 - Microwave broadband oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A microwave oscillator using a YIG oscillator is provided with a fine / coarse frequency control circuit, and by comparing with identification data corresponding to a set oscillation frequency, a wide band of 9 to 15 GHz is obtained. 1MHz
The oscillation frequency accuracy within is obtained.

[Industrial application field]

The present invention relates to an oscillator that generates electronic vibration, and more particularly to a control circuit for controlling an oscillation frequency of a microwave broadband.

[Conventional technology]

FIG. 3 shows a block diagram of a conventional microwave oscillator circuit. In the figure, reference numeral 1 is a common bus, and a designation instruction of a frequency Fin to be oscillated from an upper command system is an oscillation frequency data section 2
Is transmitted to. Reference numeral 3 converts a digital value of the frequency Fin to be oscillated by the D / A converter into an analog value and inputs the analog value to one comparison terminal of the phase comparator 4. A low-pass filter 5 cuts unnecessary high-frequency components included in the DC voltage output from the phase comparator 4 and outputs a control voltage necessary for controlling the oscillation frequency.

6 is a voltage-controlled variable frequency oscillator, and the Gunn (Gunn is the name of the discoverer) oscillator is well known as a device that oscillates microwaves. Using a Gunn diode,
It is an oscillator that uses the Gunn effect. What is the cancer effect? N type Ga
Attaching parallel electrodes on both sides of As single crystal thin plate, number [KV / cm]
When the above DC electric field is applied, the current flowing through the sample oscillates at the microwave frequency, and the period of this current oscillation is proportional to the thickness of the sample, that is, the distance between the electrodes on both sides of the single crystal thin plate.

It is known that a high Q cavity resonator having a small temperature coefficient is added to this solid-state oscillator, and the output of the solid-state oscillator is pulled into this resonator to achieve frequency stabilization and noise reduction.

Reference numeral 7 denotes a so-called PLL circuit which divides the output of the variable frequency oscillator 6 into 1 / N and feeds it back to the other comparison terminal of the phase comparator 4 by the 1 / N frequency divider. It stabilizes to N × Fin.

[Problems to be solved by the invention]

The frequency stability of the gun oscillator is about ± 5 × 10 ^-5, which is close to that of a crystal oscillator, but it has a drawback that the frequency accuracy is 2-3 MHz due to temperature changes and control voltage setting errors.

Also, the range of oscillation frequency is only several hundred MHz,
There is a drawback that many oscillators have to be switched and used to cover a wide band of about 5 GHz.

The present invention was created in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a microwave broadband oscillation circuit capable of covering a microwave broadband using one oscillator and capable of maintaining high frequency accuracy. To do.

[Means for solving problems]

As shown in FIG. 1, the microwave broadband oscillation circuit of the present invention includes an oscillation frequency data section 11 for receiving a microwave oscillation frequency of a specific interval and an output of the oscillation frequency data section.
Variable frequency oscillator for voltage or current control by D / A conversion 20
In addition to controlling the oscillation frequency of the variable frequency oscillator and the specified oscillation frequency, the oscillation circuit comprising a frequency control loop for feeding back by detecting the difference, Corresponding frequency data 12, band information 13 that determines the search direction of the output frequency of the variable frequency oscillator by distinguishing between the high frequency band and the low frequency band of the specified oscillation frequency, and make it correspond to each specified oscillation frequency of the specific interval. Converted identification data
14 is provided with a conversion table respectively storing the variable frequency oscillator is composed of a YIG oscillator, and a coarse adjustment coil 18 and a fine adjustment coil 19 for finely / coarsely controlling the oscillation frequency, and an output of the variable frequency oscillator. The first highly stable oscillator for mixing to obtain the first intermediate frequency within several tens of MHz
23, and a specific frequency f _{2 in the} vicinity of the fundamental oscillation frequency f ₁ of the first highly stable oscillator for identifying the designated oscillation frequency, and mixed with the output of the variable frequency oscillator to produce a second frequency.
A second high-stability oscillator 41 for obtaining an intermediate frequency of, a frequency counter 31 for measuring an A / D converted value by cutting an unnecessary high frequency component of the first or second intermediate frequency, A coarse adjustment circuit that controls the coarse adjustment coil until the absolute value of the measured value of the frequency counter corresponding to the intermediate frequency of 1 reaches the required frequency band; and the coarse adjustment circuit when the absolute value reaches the required frequency band. A fine adjustment circuit that switches the adjustment coil to the fine adjustment coil and controls the fine adjustment coil until the measured value of the frequency counter converges to a predetermined threshold value that is determined in advance in correspondence with the band information; and a fine adjustment circuit that converges to the threshold value. In this case, the first highly stable oscillator is switched to the second highly stable oscillator, and the frequency counter corresponding to the second intermediate frequency obtained by the second highly stable oscillator is measured. Is provided with the identification determination unit 42 for comparing the converted identification data with each other, and if the comparison result of the identification determination unit matches, control by the fine adjustment circuit that drives the second highly stable oscillator is continued, and In this case, the identification determination unit is configured to return to the control for driving the rough adjustment circuit in a desired search direction in accordance with the measured value at that time.

[Action]

The oscillation frequency data unit 11 receiving the oscillation command of the predetermined microwave oscillation frequency f converts the frequency data 12 corresponding to the oscillation frequency f into the frequency control voltage by the D / A converter 16, and controls the coarse adjustment coil 18. To do. This makes the variable frequency oscillator
20 can be roughly adjusted to the oscillation frequency f. First highly stable oscillator
The output frequency f _{1 of} 23 mixes a number of harmonics nf ₁ (n is a positive integer) generated via the multiplier 26 with the output frequency of the variable frequency oscillator 20 to create a first intermediate frequency, The low-pass filter 28 extracts a component of ± 30 MHz or less, and after the A / D conversion, the frequency is measured by the counter 31, and the measured frequency is compared with 5 MHz set in the band setting memory 32 and the comparison unit 33.
Compare the size with.

If the absolute value of the measured frequency is greater than 5MHz, coarse /
The fine determination switch 34 is on the coarse adjustment side and controls the coarse adjustment coil 18, and controls the fine adjustment coil 19 when it is less than 5 MHz. In this case, when the band information 13 is in the high band, a search is performed from the low band to the high band, and when the band information 13 is in the low band, the search is performed in the opposite direction, thereby widening the band of the oscillator circuit of the present invention. .

If the result of the search is less than 5 MHz, if the band information 13 is in the high frequency band, the measurement frequency is set to -5 MHz, and if the band information 13 is in the low frequency band, the measurement frequency is set to +5 MHz. Set, and the output of the comparator 33 is UP / D so that it converges.
The N switching device 36 is controlled, and when the comparison unit 33 confirms the convergence, the identification transition detection unit 40 is driven, and the second highly stable oscillator 41
And the determination function of the identification determination unit 42 is driven.

The identification determination unit 42 inputs the conversion identification data 14 from the table of the oscillation frequency data unit 11 and also outputs the variable frequency oscillator 20.
Of comparing the output frequency and the second intermediate frequency obtained by mixing the harmonic nf ₂ of the output frequency f ₂ of the second high-stability oscillator 41, the A match coarse / fine determination switcher 34 Switching to the direction of maintaining fine adjustment to the matching frequency, and if not matching, switching to the driving direction of the coarse adjustment coil 18 according to the search direction of the band information 13 and performing the search as described above until matching the frequency at the next fixed interval. Repeat.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings. In addition, in order to make the description of the configuration and the operation easy to understand, the same reference numerals are given to the same portions throughout the drawings, and the duplicated description will be omitted.

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a μ-wave spectrum diagram. FIG. 1 will be described below with reference to FIG. In this embodiment, an example in which microwaves are applied to a wide band of 9 to 15 GHz is shown, and the designated oscillation frequency is set at 11.95 GHz, which is a substantially middle portion, as shown in FIG. Starting from 11.905 GHz, 100 MHz intervals (1
1.9−0.1 × n + 0.005GHz), and in the frequency increasing direction (high frequency direction), starting from 11.995GHz, 100MHz intervals (12.00
+ 0.1 × n−0.005 GHz, where n is a positive integer), and therefore the interval between 11.905 GHz and 11.995 GHz in the middle is 90 MHz. The specified oscillation frequency is set to a predetermined convergence-side frequency with a threshold value described later. In the figure, 11 is an oscillation frequency data part, which is frequency data 12 (for example, the last digit is the lowest digit) corresponding to the μ wave oscillation frequency at a constant interval (for example, 100 MHz) as shown in FIG.
Frequency range data composed of a 12-bit binary code corresponding to 1.8 MHz) and band information that distinguishes between the high range and low range of the specified oscillation frequency band (11.95 GHz in this example)
(The following is distinguished from the low range and above is the high range) 13 and a conversion table of conversion identification data 14 that corresponds to each specified oscillation frequency at a fixed interval is attached, and a conversion table corresponding to the input specified oscillation frequency The data of the contents of is output.

Reference numeral 15 is a coarse adjustment counter, and when the frequency data 12 is input, the frequency data 12 is initially loaded, converted into an analog control voltage by the D / A converter 16, and the coarse adjustment coil 18 is adjusted via the amplifier 17. The variable frequency oscillator 20 has its oscillation frequency controlled by the voltage control of the coarse adjustment coil 18 and the current control of the fine adjustment coil 19.

The variable frequency oscillator 20 is an element having a garnet composition of yttrium and iron (Yttrium Iron Garnet
It is known as an element having a wide band oscillation function in an oscillator, but since the oscillation frequency accuracy is low as it is, the present invention uses auxiliary high stability oscillators 23 and 41 together to achieve an oscillation frequency accuracy of 1 MHz. It will be raised within.

21 is a directional coupler, which extracts part of the oscillation output and is a mixer
Enter in 22. Reference numeral 23 is the first highly stable oscillator, 41 is the second highly stable oscillator, and the fundamental oscillation frequencies thereof are f ₁ = 100 MHz, respectively.
And f ₂ = 100.833MHz. Where 100.83
The 3MHz number is a multiplier that generates many integer multiple harmonics.
If you create a harmonic through 26, for example 100.833MHz x 11
9 = 99912GHz, that is, with the value set for the purpose of obtaining a highly stable identification signal with a difference of 4.217MHz in the vicinity of the specified oscillation frequency 11.995GHz, and before and after the identification signal at intervals of 100.833MHz. is there. 24 is a highly stable oscillator 23
Switching control is performed by the output of the identification shift detection unit 40, which will be described later, by the changeover switch for switching the outputs of the switch 41 and the switch 41.

Normally, the highly stable oscillator 23 operates, the output of the changeover switch 24 is input to the multiplier 26 via the amplifier 25, and its output is cut to 9 GHz or less by the high-pass filter 27 and input to the mixer 22. The output of the mixer 22 is 30 by the low-pass filter 28.
It becomes a signal of MHz or less and is input to the A / D converter 30 via the amplifier 29, and the digital value thereof is measured by the frequency counter 31. Since this measurement frequency is the output of the mixer 22, ± 30
It is in the MHz range.

Assuming that the variable frequency oscillator 20 outputs, for example, 12.08 GHz, in the low-pass filter 28, 12.08 GHz and the 121st harmonic 12.1 GHz of the oscillation frequency 100 MHz of the highly stable oscillator 23 (a large number output by the multiplier 26 (One of the integer multiple harmonics, the first intermediate frequency mixed with the output of the variable frequency oscillator 20 is the only signal that can pass through the low pass filter 28 below 30 MHz)
Only the difference of 20MHz is output.

A band setting memory 32 is set to 5 MHz in this embodiment. That is, it is possible to determine whether or not the measured frequency is within the ± 5 MHz band by comparing the absolute value of the measured frequency with the preset band of 5 MHz in the band setting memory 32 in the comparison unit 33.

When the output of the comparison unit 33 is higher than 5 MHz, the coarse / fine determination switch 34 is switched to the coarse adjustment side, and the UP / DN selection circuit 35, the coarse adjustment counter 15, the D / A converter 16, the amplifier 17, the coarse adjustment Adjusting coil 1
The coarse adjustment circuit composed of 8 is driven. That is, the UP / DN selection circuit 35 searches in the high frequency direction from the output frequency of the variable frequency oscillator decreasing in the high frequency range corresponding to the division of the band information 13, and vice versa when the band information 13 is the low frequency range. The coarse adjustment counter 15 is counted so as to search.
This search means realizes a broad band of the oscillator circuit of the present invention.

If the output of the comparator 33 is less than 5 MHz, the coarse / fine judgment switch 34 is switched to the fine adjustment side, and the UP / DN switch 36, the fine adjustment counter 37, the D / A converter 38, the amplifier 39, the fine adjustment are made. Coil 19
The fine adjustment circuit composed of is driven. That is, the UP / DN switch 36 searches the output frequency of the variable frequency oscillator from the low frequency band toward the high frequency band in the case of the high frequency band corresponding to the distinction of the band data 13, and when the band data 13 is the low frequency band, On the contrary, the fine adjustment counter 37 counts like searching,
At the same time, when the output of the comparison unit 33 changes from 5 MHz or less to 5 MHz or more, the UP / DN switch 36 is switched to operate so as to converge to a predetermined threshold value.

Predetermined threshold is the value of the frequency counter 31 output is -5MHz when the band information 13 is in the high band, + 5M when it is in the low band.
The value is set to Hz.

The first half of how the oscillation frequency of the variable frequency oscillator 20 converges to the target value when the command oscillation frequency is, for example, 12.095 GHz will be described with reference to FIG.

When the designated oscillation frequency is designated as 12.095 GHz (band information 13 is high band), the offset preset in the coarse adjustment counter 15 in correspondence with the frequency data 12 input from the frequency data section 11 to the coarse adjustment counter 15 is set. Initially load up to the value (for example, 45MHz) added in the opposite direction to the search direction,
As a result, it is set near the point P (12.05 GHz) shown in FIG. Therefore, the specified oscillation frequency is 11.805 GHz (low range), 11.9
The initial load results for 95 GHz (high range) are around 11.85 GHz and 11.95 GHz, respectively. In this way, the initial load result is always set with a margin before the target oscillation frequency in the search direction. Next, the UP / DN selection circuit 35 selects the UP side according to the band information 13, the coarse adjustment counter 15 counts to the UP side, and the coarse adjustment coil 18 is controlled in the direction of increasing the oscillation frequency. When the frequency of the P point gradually increases and reaches a frequency slightly higher than 12.95 GHz, the P point is compared with the absolute value of 5 MHz set in the band setting memory 32, and the P point is within the range of 12.1 GHz ± 5 MHz. It detects that it has reached. Therefore, the coarse / fine determination switch 34 is switched to the fine adjustment side.

As the fine adjustment circuit is driven, the UP / DN switch 36 is switched to the DN side, the fine adjustment counter 37 is counted in the decreasing direction, and the frequency at point P gradually decreases to 12.095 GHz (specified oscillation on the high frequency side). Frequency and this value becomes lower than the threshold value frequency on the −5 MHz side in the count value of the first intermediate frequency obtained by mixing with the 121st harmonic 12.1 GHz of the first highly stable oscillator). Comparison unit 33 is 12.1 GHz ± 5 MHz
When it detects that the value exceeds the range of, the UP / DN switch 36 is switched to the UP side, the fine adjustment counter 37 is counted in the increasing direction, and the measured frequency of the frequency counter 31 is -5MHz side 12.095GH.
Acts to converge on z.

The comparison unit 33 monitors the number of times of passing through the convergence position, and when the required value is reached, the identification transition detection unit 40 is driven, whereby the output of the identification transition detection unit 40 causes the changeover switch 24 to be a highly stable oscillator.
The switching to the 41 side is performed and the identification determination section 42 is driven.

The oscillating frequency of the high-stability oscillator 41 generates a large number of harmonics by the multiplier 26, and as one of the harmonics, the point Q (121-1) f ₂ = 12.09996 GHz appears in the spectrum diagram of FIG. As a result, the frequency counter 31 is 12.09996-12.095 = 4.96MHz
To measure.

On the other hand, with respect to previously stored values specified oscillation frequency 12.095GHz conversion woven another data 14 corresponding to the command oscillation frequency table of the oscillation frequency data unit 11 (121-1) f ₂ -
12.095 = 4.96MHz, and the specified oscillation frequency corresponds to the distinction of the oscillation frequency band, and it is 83 every 100MHZ in ± direction.
If the identification data is set with a difference of 3 KHz, the target command frequency can be confirmed by the frequency comparison of the identification determination unit 42.

However, for frequencies below 19.95 GHz (low frequency), the convergence value (specified oscillation frequency) of the output frequency of the variable frequency oscillator 20 is set to 5 MHz of the output harmonic of the first high-stability oscillator 23 due to the search direction. Since it is UP, the value of conversion identification data 14 is 11.905GHz- (119
-1) f ₂ = 6.706MHz is set, and a difference of 833KHz is provided every 100MHz in the frequency decreasing direction. FIG. 2 shows a part of a setting example of the conversion identification data 14 corresponding to the designated oscillation frequency f.

If the output frequency of the variable frequency oscillator 20 that is initially loaded and started for some reason oscillates in the vicinity of the middle of 11.9 GHz and 12.0 GHz, as a result of searching in the frequency increasing direction, the first convergence position becomes 11.995 GHz, The output of the frequency counter 31 when switched to the high-stability oscillator 41 is (120-1) f ₂ -11.995 GHz = 4.127 MHz, which does not match the set value 4.96 MHz of the conversion identification data 14. Identification determination unit 42
When the comparison result of No. 1 does not match, the judgment output causes the coarse / fine judgment switch 34 to be switched to the coarse adjustment side, the coarse adjustment circuit is repeatedly driven, and the next position is moved in accordance with the search direction instructed by the band information 13. Search for frequencies 100MHz away. If the collation result is a match, the judgment output will be rough /
The fine determination switch 34 is switched to the fine adjustment side, and the fine adjustment coil 19 is controlled so as to maintain the current oscillation frequency.
Next, as another embodiment, the operation when the designated oscillation frequency is 12.098 GHz will be described. In this case, if the fundamental oscillation frequencies of the first and second highly stable oscillators are used without being changed, the preset value of the band setting memory 32 is set to 2 MHz and the conversion identification for the oscillation frequency 12.098 GHz specified in the oscillation frequency data section 11 is made. Set [(121-1) f ₂ -12.098 = 1.96 MHz] as the data 14.

The variable frequency oscillator 20 is searched in the frequency increasing direction by driving the first highly stable oscillator 23 and the coarse adjustment circuit, and the comparator 33 detects that the variable frequency oscillator 20 has reached within the range of 12.1 GHz ± 2 MHz. Switching, frequency counter 31
When the comparison unit 33 confirms that the measured value of the value is converged to the threshold value of −2 MHz, the second highly stable oscillator is detected through the identification transition detection unit 40.
In addition to switching to 41, conversion identification data 1.96 MHz preset in the oscillation frequency data section 11 is stored in the identification determination section 42. The purpose is achieved by driving the fine adjustment circuit so as to maintain the output of the variable frequency oscillator 20 at the position where the measured value of the frequency counter 31 coincides with this 1.96 MHz.

〔The invention's effect〕

As described in detail above, according to the microwave broadband oscillator circuit of the present invention, it is possible to generate a stable microwave frequency over a wide band, and the accuracy of the oscillation frequency is approximately ±.
The effect is that it can be set within the range of 1 MHz.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a microwave spectrum diagram, and FIG. 3 is a block diagram of a conventional microwave oscillation circuit. In the figure, 11 is an oscillation frequency data section, 12 is frequency data, 13 is band information, 14 is conversion identification data, 18 is a coarse adjustment coil, 19 is a fine adjustment coil, and 20 is a variable frequency oscillator.

Claims (1)

[Claims] 1. An oscillating frequency data section (11) which receives designation of a microwave oscillating frequency at specific intervals, and a variable frequency oscillator (20) for voltage or current control by D / A converting the output of the oscillating frequency data section. In addition to controlling the oscillation frequency of the variable frequency oscillator and the specified oscillation frequency, the oscillation circuit comprising a frequency control loop for feeding back by detecting the difference, Corresponding frequency data (12), band information (13) that determines the search direction of the output frequency of the variable frequency oscillator by distinguishing the high frequency band and the low frequency band of the specified oscillation frequency,
A conversion table for storing conversion identification data (14) corresponding to each specified oscillation frequency of the specific interval is attached, and the variable frequency oscillator is a YIG oscillator, and a coarse / fine control for controlling the oscillation frequency is provided. An adjusting coil (18), a fine adjusting coil (19), a first highly stable oscillator (23) for obtaining a first intermediate frequency within several tens of MHz by mixing with the output of the variable frequency oscillator, and A specific frequency in the vicinity of the fundamental oscillation frequency f _{1 of} the first highly stable oscillator for identifying the designated oscillation frequency
A _second highly stable oscillator (4) for outputting f ₂ and mixing it with the output of the variable frequency oscillator to obtain a second intermediate frequency.
1) and a frequency counter (31) for measuring the A / D converted value by cutting the unnecessary high frequency component of the first or second intermediate frequency
And a coarse adjustment circuit that controls the coarse adjustment coil until the absolute value of the measured value of the frequency counter corresponding to the first intermediate frequency reaches within the required frequency band, and the coarse adjustment circuit reaches within the required frequency band. In this case, the coarse adjustment coil is switched to the fine adjustment coil, and a fine adjustment circuit that controls the fine adjustment coil until the measured value of the frequency counter converges to a required threshold value that is determined in advance in correspondence with the band information, The first highly stable oscillator is switched to the second highly stable oscillator when the value converges to the threshold value, and the measured value of the frequency counter corresponding to the second intermediate frequency obtained by the second highly stable oscillator. Is provided with the identification determination unit (42) for comparing the converted identification data with each other, and if the comparison result of the identification determination unit matches, the fine adjustment circuit that drives the second highly stable oscillator. Microwave wideband oscillation characterized by continuing the control by the control, and in the case of disagreement, the discrimination / determination unit returns to the control for driving the rough adjustment circuit in a desired search direction in accordance with the measured value at that time. circuit.