JPS60149223A - Temperature-frequency characteristic correcting method - Google Patents

Abstract

PURPOSE:To correct the variance of the oscillation frequency to a temperature change by controlling the generation data of a CPU stored in a pair with the temperature data after applying the generation data to a reference oscillator with D/A conversion. CONSTITUTION:When the data to be stored to a RAM8 is produced within a range of applied temperatures, an antenna 1 is connected to a receiver 2 to receive a known radio wave having an accurate frequency such as a standard radio wave, etc. Then coincidence is obtained between the display frequency of the receiver 2 and a known frequency. While the output 54 of a reference oscillator 5 is given to the receiver 2 as a standard for setting and display of the reception frequency. A voltage control variable capacity diode 53 is connected to a crystal oscillator 52 which decides an oscillation frequency. Then the control voltage 41 to be applied to the diode 53 is varied to perform the fine control of the oscillation frequency. This compensates the variance of the oscillation frequency due to a temperature change and secures a fixed frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting temperature characteristics of a reference oscillation frequency of a radio receiver that sets and displays a reception frequency using a single crystal oscillator as a reference frequency source.

As a radio receiver that sets and displays the receiving frequency using a single crystal oscillator as a reference frequency source, for example, in a Sue-G heterogain type receiver, the receiving frequency is an intermediate frequency and a local oscillation frequency. The local oscillator is controlled by PLL (Phase Locked Loop) VCO (Voltage Controlled 0).
It is possible to set up to the H2 digit as a signal generator (scillator), and it is possible to accurately read the reception frequency on a digital display, but the absolute accuracy of these frequencies depends on the reference frequency of the PLL circuit and the frequency counter. It depends on the accuracy of the clock frequency, and in the multiplex conversion method, it is also affected by the frequency accuracy of the local oscillator in each conversion stage.
In order to maintain good reception frequency accuracy, it is necessary to configure the temperature and aging stability of all oscillators well, and to precisely adjust the frequency settings, which requires a great deal of effort in design, production, and adjustment. In order to reduce the required frequency, the required frequencies are obtained by dividing, multiplying, and mixing a single reference frequency, and only one oscillator is required for accuracy. , extremely easy to adjust and maintain.

A crystal oscillator is used as a reference frequency oscillator from the viewpoint of frequency stability, but the temperature-frequency stability, which is a particular problem, is mainly determined by the crystal oscillator used. Y-cut oscillators had relatively large frequency changes due to temperature, so they were often used in a thermostat; however, later R-cut oscillators
The R' cut, or the current AT cut, GT cut, etc., have extremely good temperature-frequency characteristics near room temperature, so they can sufficiently maintain performance that exceeds the requirements of the Radio Law even without using a constant temperature oven for radio equipment. ing. However, as frequency settings and displays have become more precise in recent years, maintaining frequency accuracy commensurate with this has become a problem. Temperature-frequency changes can be completely resolved by housing the crystal oscillator or the entire oscillator in a thermostatic oven, but using a thermostatic oven increases space and mechanical parts, and also Since there is a large frequency change during the period until the machine reaches its operating temperature (approximately 40 to 60 degrees Celsius), the preheating time before actual operation is much longer than that of a non-thermal oven machine, and to avoid this, it is necessary to It is necessary to keep at least several watts of electricity flowing through the thermostatic chamber even when it is not in use, which often goes against energy conservation.

The present invention has been made in order to cope with the current situation as described in 2.The present invention will be described with reference to FIG. 1 showing an embodiment of the present invention. The radio receiver 2 that sets and displays the receiving frequency as follows: (1) means for inputting the tuning instruction output 21 to the CPU 3; and (2) means for inputting the data 31 generated by the CPU 3, which increases and decreases at step intervals, to a D/A. means for applying the control voltage 41 converted by the converter 4 to the receiver reference frequency source 5 to increase or decrease its frequency; and (3) a temperature sensing element 6 for sensing the temperature of the reference oscillator (5 or crystal oscillator 52). (4) means for inputting the temperature instruction amount 71 converted by the A/D converter 7 to the CPU; and (4) means for stopping the increase/decrease of the data 31 generated by the CPU when the tuning instruction output 21 indicates a tuning point. , (5) means for storing the generated data 31 of the CPU 3 at that time and the temperature data 71 of the temperature sensing element 6 as a pair in the RAM 8; and (6) a CPU that stores the temperature data 71 and the temperature data 71 as a pair in the RAM 8. A temperature-frequency correction method comprising means for controlling the oscillation frequency 54 of the reference oscillator 5 by D/A converting the generated data 31 of the reference oscillator 5. In this case, the RAM should be
In order to create the data to be stored in 8, connect antenna 1 to receiver 2 and receive radio waves with accurate and known frequencies, such as standard radio waves or broadcast radio waves, so that the frequency display on the receiver matches the known frequency. Do it like this. Tuning instruction output 2
1 is the zero beat point when using the beat sound output, and the zero point of the direct current output is the tuning point in the discriminator method, and in this case, the direction of detuning can be determined by the positive or negative sign of the output polarity.

The output 54 of the reference oscillator 5 is given to the receiver 2 and serves as a reference for setting and displaying the reception frequency.A voltage-controlled variable capacitance diode 53 is connected in series (as shown) or in parallel to the crystal oscillator 52 that determines the oscillation frequency. By finely adjusting the oscillation frequency by changing the control voltage 41 applied to the oscillator, it is possible to compensate for fluctuations in the oscillation frequency due to temperature changes and maintain a constant frequency. Therefore, the control voltage value is determined by the temperature change range and the corresponding frequency change amount of the crystal resonator, and it is naturally desired that the temperature-frequency change be small. Crystal resonators are generally manufactured so that the temperature-frequency change is small near the operating temperature.
Room temperature T to show an example of the characteristics of a cut vibrator. The frequency change decreases over a wide temperature range centered on s.If the frequency at the lowest temperature TL is ft, and the frequency at the highest temperature TH is fn, the amount of change in fH-fL satisfies the radio regulations. However, as mentioned above, it is within a range that does not pose any problem in practical use, but higher frequency accuracy is required for another purpose, and as a method other than a thermostatic oven, it is not possible to connect the crystal unit in series. There is a way to compensate for frequency changes by using the temperature coefficient of parallel capacitors, but it is difficult to adapt to wide temperature changes, and it is impossible to compensate for complex changes like the one shown in Figure 2. It is.

In the case of the present invention, assuming that the operating temperature range is 0 to 50°C, TL in FIG. 2 is 0°C and TH is 50°C.

T1 to Tn are intermediate temperatures equally divided between these temperatures, and 10
If the interval is 0°C, it is divided into 5 equal parts, and if the interval is 5°C, it is divided into 10 equal parts.
At each set temperature, the oscillation frequency 54 is the center frequency f. Since the control voltage 41 is applied to pull the oscillation frequency back to , the oscillation frequency change is only the change in the crystal resonator's characteristics between each set temperature, which is extremely small compared to the overall amount of change. It goes without saying that the smaller the value, the smaller the amount of change.

The control voltage 41 is controlled by the CPU (Central Process
D/A (
Since the data 31 is obtained by converting the data 31 (digital to analog), the range of the data 31 and the step interval of change are determined by back calculation.

In order to obtain compensation data of 1, it is necessary to vary the reference oscillator 5 in the temperature range from TL to TH. The reference oscillation frequency fo is automatically determined by receiving a known frequency with the temperature set to the specified center temperature state of the crystal oscillator. If data 31 (also control voltage 41) is given, the oscillation frequency automatically becomes fo, so there is no need to know fo quantitatively. Also, since the temperature of the oscillator at that time is the same, data 31 and 71 at each temperature state are stored in a RAM (Random Access Mechanism) as a pair.
(more) 8, the relationship between the oscillator temperature and the control voltage is set closely, and each set temperature does not need to be determined strictly, and CPU operation will start once the planned set temperature is reached. When button 10 is pressed, C
The PU performs an operation of increasing or decreasing the data 31 within a predetermined data value range in predetermined steps. Accordingly, the tuning frequency of the receiver increases or decreases minutely, and in the middle of this, the CPU reads the "tuning point" of the tuning instruction output 21, stops the step change of the data 31, fixes it, and combines the data 31 and temperature data at that time. are stored in RAM 8 as a pair. The above operations are performed for each set temperature, the results are stored in RAM 8, and when receiving, the CPU always monitors the temperature data 71,
It refers to the temperature data stored in the RAM 8 and outputs the frequency control data stored as a pair when the two match as 31. Therefore, as shown in FIG. 2, when the temperature of the reference oscillator increases, the frequency increases as the temperature rises from TL to T1, but returns to the original f at T1. , and then changed slightly until T2, then f. The compensation operation is repeated repeatedly, and the smaller the set temperature interval, the more f. It is clear that the deviation can also be reduced. Furthermore, the memory in the RAM 8 can be retained even when the receiver is powered off by installing a backup battery 9, so the data storage operation only needs to be performed once at the time of shipment. can be easily carried out, and since the aging of the reference oscillator is also corrected, there is an advantage that the frequency accuracy of the receiver can always be maintained at its best. It is advantageous to use the spare capacity of the CPU for the skin in the receiver as the CPU, which plays a central role in the operation, will reduce the economic burden.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of an implementation configuration of the present invention, and FIG. 2 is a diagram illustrating an example of a temperature-frequency change characteristic curve of a crystal resonator and a frequency compensation state according to the present invention. 1... Antenna, 2... Receiver, 3... CPU,
4...D/A converter, 5...Reference frequency oscillator, 6
... Temperature sensing element, 7... A/D converter, 8...
RAM, 9... Backup battery, 10... Start button, 21... Tuning instruction output, 31... Frequency control data, 41... Frequency control voltage, 52... Crystal resonator, 53...・Voltage controlled capacitance diode, 54・
...Reference oscillator output. Patent applicant Yaesu Musen Co., Ltd.

Claims (1)

[Scope of Claims] A radio receiver that sets and displays a reception frequency using a single crystal oscillator as a reference frequency source, comprising: (1) means for inputting a tuning instruction output to a CPU; (2) a means for inputting a tuning instruction output to a CPU; (3) means for increasing or decreasing the frequency by applying a control voltage obtained by D/A converting data that increases or decreases at step intervals to the receiver reference frequency source; and (3) means for increasing or decreasing the frequency of the reference oscillator. / D conversion and CPU
(4) means for stopping the increase/decrease of the data generated by the CPU in (2) when the tuning instruction output in (1) indicates a tuning point; (5) the CPU at that time; means for storing the generated data and the temperature data of the temperature sensing element as a pair in a RAM; (6) upon reception, the CPU receives the temperature instruction amount of the temperature sensing element of (3);
The temperature data of the temperature sensing element stored in the RAM in (5) above is monitored, and if the two match, the temperature data and the CPU generation data stored in the RAM as a pair are D/
and means for controlling the oscillation frequency by converting the oscillation frequency into a reference oscillator.
Frequency correction method.