KR940007040B1 - Voltage controlled-temperature compensated x-tal oscillater - Google Patents

Abstract

The circuit and method for stabilizing a voltage controlled-temperature compensated oscillator (VC-TCXO) of a radio telephone comprises a multiplier for 6-multiplying an oscillating frequency generated from the VC-TCXO, a first divider for 1/9-demultiplying an output of the multiplier to be supplied as a reference clock signal of a custom IC, and a second divider for dividing the oscillating frequency of the VC-TCXO to be supplied as the reference clock signal of an audio processor, thereby obtaining good receiving sensitivity.

Description

Stabilization Circuit and Method of Voltage Controlled Temperature Compensation Oscillator in Wireless Telephone

1 is a conventional circuit diagram.

2 is a circuit diagram according to the present invention.

3 is a general characteristic diagram of direct current voltage and ppm of VC-TCXO.

4 is a flowchart of an embodiment according to the present invention.

The present invention relates to a stabilization circuit of a voltage controlled temperature compensated oscillator (Voltage Controlled-Temperatare Conpensated X-Tal Oscillater (hereinafter referred to as "VC-TCXO") of a cordless telephone, particularly in digital cellular or GSM (Group Special Mobile). The present invention relates to a stabilization circuit and a method of a voltage controlled temperature compensated oscillator of a wireless telephone that can maintain the stability of transmission frequency within ± 0.23ppm (Part Per Million) by reducing the frequency deviation of VC-TCXO.

In the mobile radiotelephone, the VC-TC * XO is used, and the error of the second intermediate frequency signal is fed back to the frequency synthesizer to control the oscillation frequency of the VC-TCXO to automatically reduce the variation in the transmission frequency.

Looking at the prior art with reference to Figure 1, as follows.

When a signal transmitted from a base station or cellsite (not shown) is input to the duplexer 2 through the antenna 1, the received signal is amplified by a low noise amplifier (LNA) 3. Through the band pass filter (4). At this time, the frequency synthesizer 100 (composed of the prescaler 10, the voltage controlled oscillator 11, the phase comparator 12, the low pass filter 13, the divider 14 and the voltage controlled temperature compensation crystal oscillator 15] The signal output from and passed through the band pass filter 9 is mixed with the output of the band pass filter 4 in the first mixer 5 and then passed through the amplifier 6. The signal is a second local oscillation frequency signal half-resonated in the X-TAL (17) is mixed in the second mixer (7), the second intermediate frequency passed through the second mixer (7) is generally 455 KHz, Some hit the detection circuit (8), while another divides the divider (18) into 1/2 ⁴ (16384) values so that a signal of about 27.771 Hz (455 KHz ÷ 16384) is input to the counter in the central control unit 19. The counter is configured in the central control unit 19, and one cycle of the signal of 27.771 Hz (T = That is, the counted clock signal inputted through the clock signal input terminal for 0.036 seconds is inputted to the comparator. At this time, the clock signal is generated in a predetermined clock signal generation circuit, and the clock frequency is 10.24 KHz.

The comparator is stored in the coefficient data and the reference data storage to compare the reference data to obtain a difference signal and send it to the compensator. In this case, the reference data becomes 368730 (10.24 MHz ÷ 27.771 Hz) which counts the 10.24 MHz clock signal in 0.036 seconds. Therefore, the difference signal represented by the difference between the coefficient data according to the deviation of the second intermediate frequency signal and the reference data set to 368730 is input to the compensator. The compensator is also configured in the central controller 19. The compensator sets a compensated value and outputs the D / A converter 16 to an analog compensation voltage to control the frequency of the voltage controlled temperature compensation crystal oscillator 15. It is supposed to be.

However, in the conventional mobile radiotelephone, the transmission frequency stability is set to ± 2.5ppm for the analog method and the transmission frequency stability to ± 0.23ppm for the digital method.

In general, if the second local oscillation frequency oscillated at X-TAL (17) is, for example, 90MHz, the frequency stability is ± 7ppm. Therefore, X-TAL (17) at extreme conditions [temperature (-30 ℃ ~ + 60 ℃), humidity, etc.] ) It is possible to satisfy up to ± 630Hz, which can satisfy the stability of the transmission frequency when the frequency stability of the voltage-controlled temperature compensated crystal oscillator 15 is included in the analog and digital mobile phone. There is no technical problem. The frequency deviation of the X-TAL 17 itself is generated as follows (1).

Accordingly, an object of the present invention is to provide a circuit and method that is advantageous for reception sensitivity and noise since the stability of transmission frequency is maintained within ± 0.33 ppm in any environmental condition to stabilize the first and second intermediate and clock frequencies.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram according to an embodiment of the present invention, in which the oscillation signal of the VC-TCXO is multiplied by six times to the output terminal of the voltage controlled temperature compensation crystal oscillator 15 of the frequency synthesizer 100 of the second mixer 7. A multiplier 17 providing a second local oscillation signal for making 2n IF, and divides the output of the multiplier 17 into 1/9 to provide a reference clock signal (10.24MHz) of the custom IC 21. A first divider 20 and a second divider 22 for dividing the oscillation frequency of the VC-TCXO by 1/20 and providing it as a reference clock signal of the audio processor 23.

In addition, the low pass filter 24, the D / A converter 16, and the frequency control circuit 190, which control the oscillation of the voltage controlled temperature compensated crystal oscillator 15, are filed by a patent applicant (Patent Application No. 90-7460). As a result, detailed descriptions will be omitted.

3 is a characteristic diagram in direct current voltage and ppm of VC-TCXO.

4 is a flow chart according to the present invention.

Therefore, a specific embodiment of the present invention will be described in detail with reference to FIGS.

The present invention uses a voltage-controlled temperature compensated crystal oscillator 15 pole, VC-TCXO, and a multiplier 17 that multiplies the oscillation frequency of the VC-TCXO by 6 times, and the oscillation frequency multiplied by the 6 times to 1/9. The first divider 20 for dividing and the second divider 22 for dividing the oscillation frequency of the VC-TCXO by 1/20, and divide the oscillation frequency of the VC-TCXO in the divider 18 as shown in the flowchart of FIG. When there is no initial deviation (Fo) by dividing and comparing the output of the counter 25 with the output value of the reference data storage part 32 in the comparator 31, the divider 14, 18 is set. ) And a value of Fo ± Δ4f is generated when a deviation from the value of the reference data storage unit 32 occurs by inputting the value calculated by the counter 25 as the comparison coefficient 31. If a value larger than + Fo occurs, the negative control value, which can reduce the output value, is output from the compensator 30. When a value smaller than Fo is generated, the positive control value, which can be increased, is output from the compensator 30.

In other words, the divider 18 divides the value calculated by the counter 25 and the comparator 31 sets the compensation value in the compensator 30 according to the comparison result with the value of the reference data storage unit 32. The compensation value is output to the D / A converter 16 and input to the voltage controlled temperature compensation crystal oscillator 15. As a result, stabilization of the oscillation frequency of the VC-TCXO 15 is always maintained at the value in the reference data storage unit 32.

When a signal of a frequency (869 .040-893.970 MHz) transmitted from a base station not shown in Figs. 2, 3, and 4 is received through the antenna 1 and input to the duplexer 2, The desired received signal is properly amplified by the low noise amplifier 3 to generate a desired frequency that has passed through the bandpass filter 4.

In the frequency synthesizer 100 [prescaler 10, voltage controlled oscillator 11, phase comparator 12, low pass filter 13, divider 14, voltage controlled temperature compensation crystal 15] The generated first local oscillation frequency (961.655-986.585MHz) output signal is passed through the bandpass filter (9). Both signals are amplified by the first intermediate frequency amplifier 6 by generating a first intermediate frequency (first local oscillation frequency-receive frequency = 92.615 MHz) of the output signal by the first mixer 5. This is input to the second mixer 7. This is generated by the VC-TCXO 15, and the second local oscillation frequency multiplied by 6 times in the multiplier 17 (15.36 MHz x 6 = 92.160 MHz) is mixed in the second mixer 7 to obtain a second intermediate frequency ( The first intermediate frequency-second local oscillation frequency = 455 MHz) is outputted through the detection circuit 8 and then output as an audio signal.

In addition, the second local oscillation frequency is divided by 1/9 from the first divider 20 to 10.24 MHz (92.160 MHz ÷ 9) and provided as the clock frequency of the custom IC 21 or the central controller 19. When the oscillation frequency of the VC-TCXO 15 is divided into 1/20 by the second divider 22, 768 kHz (15.36 MHz / 20) can be used as the clock frequency of the audio process 23.

The frequency stability of the VC-TCXO 15 is described in detail by referring to FIG. 3 with reference to FIG. 3. When the oscillation frequency of the VC-TCXO 15 is 15.36 MHz, the divider 14 inside the PLL 14 is used. 30 KHz (15.36 MHz ÷ 512) divided by 1/512 is divided by the divider 18 (14.648 Hz (30 KHz ÷ 2048)) and counted by the counter 25. The counter 25 outputs the 14.648 Hz signal in one cycle, i.e. , Which is a counting clock signal input for 68.3 ms, which is input to the comparator 31.

The clock frequency generated by the first divider 200 is 10.24 MHz, and a value of 699072 (10.24 MHz ÷ 14.64 Hz), which is a coefficient of a 10.24 MHz clock signal corresponding to 68.3 ms, is stored in the reference data storage unit 32. It is. Therefore, if the oscillation frequency of the VC-TCXO (15) is a deviation in temperature or any environment, conditions, the 699072 and the coefficient value of the deviation is compared in the comparator 31 and the value of 졀 and the value is sent to the compensator 30, The compensator 30 sets a compensation value according to the comparison result of the comparator 31. If there is no difference between the coefficient data and the reference data, the output of the first compensation data generator 27 is selected to be kept in the previous state, and if the difference is greater than the coefficient data and the reference data, the second direction is used to reduce the difference by the difference. The output of the compensation data generator 28 is selected, and if it is less than the coefficient data and the reference data, the output of the third compensation data generator 29 is selected to go up by the difference, which is then used as a control signal. Are respectively converted into analog compensation voltage via D / A converter 16 and passed through low pass filter 24 for power supply noise removal to finally control voltage controlled temperature compensated crystal oscillator 15 automatically. As a result, the entire frequency is stabilized (maintained at a stability equivalent to 2.5 ppm with zero ball in FIG. 3).

As described above, the stability of the transmission frequency can be maintained within ± 0.23ppm under any environmental conditions, and as the second intermediate frequency is stabilized, there is an advantage in reception sensitivity noise.

Claims (3)

Frequency synthesizer 100, central controller 19, frequency control circuit 190, including second mixer 7, custom IC 21 and audio processor 23, voltage controlled temperature compensation crystal oscillator 15 In the stabilization circuit of the voltage controlled temperature compensating crystal oscillator 15 of a mobile telephone having a D / A converter 16, the oscillation signal output from the voltage controlled temperature compensating crystal oscillator 15 is multiplied by six times. A multiplier 17 which provides a second local oscillation signal for making 2nIF of the second mixer 7 and the output of the multiplier 17 are divided by 1/9 to thereby reference the clock of the custom IC 21. A second divider 22 which divides an oscillation frequency of the voltage-controlled temperature compensated crystal oscillator 15 and provides a reference clock signal of the audio processor 23 as a signal (10.24 MHz). Voltage control on a wireless telephone, comprising Stabilization of compensated oscillator circuit. In the method of stabilizing the reference data storage unit 32, the counter 25, the comparator 31, the compensator 30, and the voltage controlled temperature compensation crystal oscillator 15 in the mobile radiotelephone, the digital values required for the initial compensation are determined. The first step of setting the frequency control median of the voltage control temperature compensation crystal oscillator 15 to the value converted into an analog signal and counting it in the counter 25 so as to divide a predetermined frequency, and the counting value in the first step A second process of checking whether a value within the compensation range is compared by comparing the value of the reference data storage unit 32 in the comparator 31; and when the value is within the compensation range in the second process, the timer is adjusted by the compensator 30. Reset and set the compensation value in the compensator 30 when the value is out of the compensation method, and convert the analog signal for temperature compensation control in the D / A converter 24 to convert the voltage controlled temperature compensation crystal oscillator 15. Method of stabilizing the voltage-controlled temperature-compensated oscillator of a wireless telephone, characterized in that consisting of a third step of controlling. 3. The method of claim 2, wherein the third process reduces the frequency generation by a difference when the generated division value of the voltage controlled temperature compensated crystal oscillator 15 is greater than the reference data storage unit 32. When the frequency division value is smaller than the value of the reference data storage unit 32, the frequency generation temperature stabilization method of a voltage controlled temperature compensated oscillator, characterized in that for increasing the frequency generation by a difference.