WO2000014880A1

WO2000014880A1 - Method of adjusting voltage-controlled oscillator

Info

Publication number: WO2000014880A1
Application number: PCT/JP1999/004696
Authority: WO
Inventors: Hiroshi Miyagi
Original assignee: T.I.F. Co., Ltd.
Priority date: 1998-09-04
Filing date: 1999-08-31
Publication date: 2000-03-16
Also published as: JP2000082957A

Abstract

A method is provided for facilitating adjustment of the oscillation frequency of a voltage-controlled oscillator. A CPU (60) sets the ratio of a frequency divider (30) so that the oscillation frequency of a VCO (10) may become the lower limit (fmin) of a desired range, and then measures the value (Vc) of a control voltage applied by an LPF (50) to the VCO (10). The voltage (Vs) applied to a varactor (20) connected in series to an inductor (12) in an LC resonance circuit of the VCO (10) can be adjusted if the measured control voltage (Vc) is out of a predetermined range.

Description

Description Voltage controlled oscillator adjustment method Technical field

The present invention relates to a voltage controlled oscillator adjustment method for adjusting a variable frequency range of a voltage controlled oscillator. Background art

For various communication devices such as mobile phones, available frequency bands are determined in advance according to their uses. On the radio wave transmitting side, a carrier signal included in an available frequency band is generated, and a signal obtained by modulating the carrier signal with an information signal such as voice is transmitted. On the radio wave receiving side, a predetermined demodulation process is performed on the received signal to remove the carrier signal, thereby extracting an information signal such as voice. In these modulation and demodulation processes, an oscillation signal output from a voltage controlled oscillator (VCO) is often used to generate and remove a carrier signal, which is required for the VCO. It is necessary to output the oscillation frequency signal correctly.

FIG. 5 is a diagram showing a configuration of a conventional frequency synthesizer using a VCO. The frequency synthesizer 200 shown in the figure includes a VCO 202 in which an oscillation frequency is set based on an applied control voltage, a frequency divider 204 having a predetermined frequency division ratio, a phase comparator 206, A phase locked loop (P LL: Phase Locked Loop) is formed by including a pass filter (LPF) 208. VC0202 is, for example, an LC oscillation circuit including a variable capacitance diode.

Assuming that the frequency division ratio of frequency divider 204 is N and the frequency of the reference signal input to one input terminal of phase comparator 206 is fr, the frequency f osc of the oscillation signal output from VC 0202 is Nx fr The voltage Vc applied from the LPF 208 to the VCO 202 is controlled so that

By the way, in mobile phones, radio receivers, television receivers, etc., A predetermined communication operation is performed by selecting one of a plurality of communication channels included in a predetermined frequency range set in advance. Therefore, when trying to generate a carrier signal corresponding to each communication channel by the frequency synthesizer 200 shown in FIG. 5, the variable frequency range of the oscillation signal output from the VC 0202 includes the plurality of communication channels described above. Must be set to be equal to or wider than the frequency range.

FIG. 6 is a diagram showing a relationship between the control voltage Vc applied to the VCO 202 and the oscillation frequency: fosc. For example, the variable range of the carrier frequency in a communication device using the frequency synthesizer 200 shown in FIG. When the control voltage Vc applied to the VCQ 202 changes from 0 to Vcc, the variable range of the oscillation signal output from the VCO 202 becomes the variable range of the carrier frequency (f min ~: fmax) must be included. The control voltage-oscillation frequency characteristic line A shown in Fig. 6 satisfies this condition, and by using the VCO 202 having such characteristics, communication using a communication channel having the required carrier frequency is possible. become. For example, when considering a frequency synthesizer used in a mobile phone and configuring the VCO 202 with an LC oscillator circuit, the inductor, capacity, variable Capacitance diode is selected.

However, since various elements actually used and wiring patterns for connecting the elements have variations, even in the case of V C 0202 manufactured through the same process, the characteristics are often different. Therefore, even if the VCO 202 is manufactured so as to satisfy the ideal characteristic line A shown in FIG. 6, in many cases, the VC 0202 actually has the characteristic lines B and C shown in FIG. . Of course, for the characteristic lines B and C, even if the control voltage Vc of the VC 0202 is set to its lower limit or upper limit, the required carrier frequency cannot be obtained, so communication via some communication channels is not possible. C In particular, since mobile phones use high-frequency bands such as 800 MHz and 1.5 GHz, the oscillation frequency of VC0202 varies due to variations in elements. There are few that meet the ideal characteristic line A without adjustment.

Therefore, when a VCO 202 having characteristic lines B and C is actually manufactured, The variable range of the oscillation frequency is adjusted so as to satisfy the characteristic line A by adjusting the element constant of one of the elements included in CO 202. For example, when an inductance is formed by the pattern wiring, the oscillation frequency of the VC0 202 is obtained by removing a part of the pattern by a method such as laser trimming while displaying the oscillation frequency on a monitor screen or the like. Is changed so that the characteristic line A is satisfied. Alternatively, include a trimmer capacitor for frequency adjustment in VC〇202, and adjust the capacitance value of this trimmer capacitor while displaying the oscillation frequency on a monitor screen or the like so that the characteristic line A is satisfied. I have to.

As described above, in the conventional VCO 202, in order to adjust the variable range of the oscillation frequency, the inductance value is adjusted by laser trimming, or the capacitance value of the trimmer capacitor is adjusted. In any case, it is necessary for a specific worker to perform the adjustment work while monitoring the oscillation frequency of the VCO 202, and there is a problem in that the adjustment work is time-consuming. Disclosure of the invention

The present invention has been made in view of the above points, and an object of the present invention is to provide a voltage controlled oscillator adjustment method which can easily adjust the variable range of the oscillation frequency of the voltage controlled oscillator. .

In the voltage controlled oscillator adjustment method of the present invention, the variable range of the oscillation frequency of the voltage controlled oscillator is adjusted based on the value of the control voltage applied to the voltage controlled oscillator when the voltage controlled oscillator is oscillated at a predetermined frequency. Since the variable range adjusting means is provided, the variable range can be automatically adjusted, and the labor required for the adjustment can be saved.

Further, the above-described voltage-controlled oscillator includes a first element constant variable element whose element constant can be changed according to an applied control voltage, and a second element constant variable element whose element constant can be changed according to an applied adjustment voltage. It is preferable that the variable element adjuster adjusts the value of the adjustment voltage applied to the second element constant variable element by using a variable range adjuster. By changing the value of the adjustment voltage applied to one of the two element constant variable elements, the oscillation frequency changes when the value of the control voltage applied to the other is changed. The range to be formed can be easily adjusted.

In particular, the above-mentioned voltage controlled oscillator is configured to include an LC resonance circuit, and in the LC resonance circuit, the first variable capacitance diode connected in parallel with the inductor is used as the above-described first element constant variable element, It is preferable that the second variable capacitance diode connected in series with the inductor is a second element constant variable element. By applying the adjustment voltage to the second variable capacitance diode connected in series with the inductor, the variable range of the oscillation frequency of the voltage controlled oscillator set according to the adjustment voltage can be largely changed.

In addition, the variable range adjusting means described above allows the value of the control voltage to be included in the predetermined range when the value of the control voltage when the voltage controlled oscillator is oscillated at the predetermined frequency is out of the predetermined range. It is preferable to change the adjustment voltage until it is. By performing the adjusting operation so that the value of the control voltage corresponding to the predetermined frequency is included in the predetermined range, the variable range of the oscillation frequency can be set to a desired value.

Further, it is preferable that the value of the adjustment voltage set at the start of the adjustment operation by the variable range adjustment means is approximately / of the power supply voltage. By setting the adjustment voltage to approximately one-half of the power supply voltage, the adjustment voltage can be changed in any direction in the subsequent adjustment operation, so that the variable range of the oscillation frequency that is shifted at the start of the adjustment operation is ensured. It can be set to a desired value.

Further, it is preferable that the value of the adjusted voltage adjusted by the variable range adjusting means is stored in the voltage value storage means. By storing the value of the adjusted voltage after the adjustment, the optimum adjusted voltage can be set each time the power is turned on.

It is preferable that a frequency synthesizer is configured by combining a frequency divider, a phase comparator, and a low-pass filter with the above-described voltage-controlled oscillator. The voltage control oscillator can be oscillated at a predetermined frequency only by setting the frequency division ratio of the frequency divider to a predetermined value by the variable range adjusting means, so that the above-described adjustment operation is facilitated. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram illustrating a configuration of a frequency adjustment mechanism according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a relationship between an adjustment voltage V s applied to a variable capacitance diode and a capacitance C s. Figure,

FIG. 3 is a flowchart of an operation procedure for adjusting the variable range of the oscillation frequency of V C0 by the frequency adjustment mechanism of the present embodiment,

FIG. 4 is a diagram showing the relationship between the lower limit value fmin of the variable range of the oscillation frequency and the control voltage Vc applied to V C0,

FIG. 5 is a diagram illustrating a configuration of a conventional frequency synthesizer using V C0, and FIG. 6 is a diagram illustrating a relationship between a control voltage Vc applied to a VCO and an oscillation frequency fosc. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment to which the present invention is applied will be specifically described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a frequency adjustment mechanism according to an embodiment to which the present invention is applied. The frequency adjustment mechanism shown in FIG. 1 includes a VC010 forming a frequency synthesizer, a frequency divider 30, a phase comparator 40, It is configured to include an LPF 50, a CPU 60 for adjusting a variable range of the oscillation frequency of the VCO 10 by executing a predetermined adjustment program, and a memory 70.

VCO 10 is a clap oscillation circuit that performs a predetermined oscillation operation using LC resonance. In the LC resonance circuit, a reverse bias voltage applied to a variable capacitance diode 14 connected in parallel to the inductor 12 in the LC resonance circuit is determined. , The variable oscillation frequency fosc is set by changing the control voltage Vc applied from the LPF 50. Further, a variable capacitance diode 20 is connected in series with the inductor 12 included in the LC resonance circuit in order to adjust the variable range of the oscillation frequency. The reverse bias voltage of the variable capacitance diode 20 is set by the adjustment voltage Vs applied from the CPU 60, and by varying the adjustment voltage Vs, the variable range of the oscillation frequency of VC〇10 is adjusted. You.

Next, the oscillation frequency of the VCO 10 will be considered. Assuming that the inductance of the inductor 12 is L and the capacitance of the variable capacitance diode 20 is Cs, the total combined impedance L ′ of the inductor 12 and the variable capacitance diode 20 connected in series is [Equation 1]

Becomes Further, assuming that the capacitance of the variable capacitance diode 14 is Cd and the capacitance of the peripheral element appearing in parallel with this is △ C, the oscillation frequency of V C 〇10 determined by each element constant of the LC resonance circuit: fosc is

[Equation 2]

Becomes That is, the oscillation frequency f osc of the VCO 10 varies not only when the capacitance Cd of the variable capacitance diode 14 connected in parallel with the inductor 12 is changed, but also when the capacitance of the variable capacitance diode 20 connected in series with the inductor 12. It can be varied by changing Cs. Therefore, by setting the reverse bias voltage applied to one variable capacitance diode 14 by the control voltage Vc applied from the LPF 50, the oscillation frequency of the VCO 10 is variably controlled, and the other variable voltage is set. By setting the reverse bias voltage applied to the capacitance diode 2 ° by the adjustment voltage Vs applied from the CPU 6 °, the variable range of the oscillation frequency of VC010 can be adjusted.

For example, if the adjustment voltage Vs applied from the CPU 60 to the variable capacitance diode 20 is set to a certain value, and the VCO 10 has the characteristic lines B and C shown in FIG. By adjusting the value of the adjustment voltage Vs applied to the variable capacitance diode 20 to change the capacitance Cs of the variable capacitance diode 20, the characteristic can be made to match the optimum one (characteristic line A).

FIG. 2 is a diagram showing the relationship between the adjustment voltage Vs applied to the variable capacitance diode 20 and the capacitance Cs. As shown in the figure, the variable capacitance diode 20 has a reverse bias voltage. The characteristic shows that the capacitance Cs appearing at both ends decreases as the adjustment voltage Vs applied to both ends as the voltage increases.

For example, when the VCO 10 has the characteristic B shown in FIG. 6, it is necessary to lower the oscillation frequency f osc corresponding to the control voltage Vc applied from the LPF 50. In this case, the capacitance Cs of the variable capacitance diode 20 must be increased from the above-described equation (2). Therefore, as shown in FIG. 2, the adjustment voltage Vs applied to the variable capacitance diode 20 may be reduced.

Conversely, when the VCO 10 has the characteristic C shown in FIG. 6, it is necessary to increase the oscillation frequency f osc corresponding to the control voltage Vc applied from the LPF 50. In this case, the capacitance Cs of the varactor diode 20 must be reduced from the above equation (2). Therefore, as shown in FIG. 2, the adjustment voltage Vs applied to the variable capacitance diode 20 may be increased.

Divider 30 divides frequency f osc of the signal output from VC〇10 to 1 / N (N is an integer). The dividing ratio N can be changed, and its value is set by the CPU 10. The phase comparator 40 compares the phase of the signal of frequency fosc / N output from the frequency divider 30 with the reference signal of frequency fr, and outputs a signal having a duty ratio according to the comparison result. The LPF 50 removes high-frequency components from the signal output from the phase comparator 40 to generate a DC control voltage Vc applied to the VCO 10.

The CPU 60 has an A / D converter and a D / A converter (both not shown), and converts the control voltage Vc applied from the LPF 50 into digital data by the A / D converter. During the conversion, the adjustment voltage V s applied to the variable capacitance diode 20 is generated by the D / A converter. The CPU 60 sets the value of the variable frequency division ratio N of the frequency divider 40 in order to output an oscillation signal having a desired frequency from the VCO 10. For example, if the required oscillation frequency is 1.5 GHz and the reference frequency input to the phase comparator 40: r is 100 kHz, set the division ratio N to 15000. .

The memory 70 stores data corresponding to the adjustment voltage Vs set by the CPU 60.

(Adjustment voltage data). Once the adjustment voltage data is stored in the memory 70, Then, every time the power is turned on, the adjustment voltage data is read from the memory 70 by the CPU 60, the adjustment voltage Vs is generated by the D / A converter in the CPU 60, and applied to the variable capacitance diode 20. Is done. Most of recent mobile phones and other communication devices are equipped with a general-purpose CPU and a memory for storing the operation program of the CPU and various data in order to control the display of the liquid crystal display device. These can be used as the CPU 60 and the memory 70 described above.c The CPU 60 described above is used as the variable range adjusting means, the variable capacitance diode 14 is used as the first element constant variable element, and the variable capacitance diode 20 is used as the second element constant variable element. The memory 70 corresponds to the voltage value storage means.

The frequency adjustment mechanism of the present embodiment has such a configuration, and the operation will be described next. FIG. 3 is a flowchart of an operation procedure for adjusting the variable range of the oscillation frequency of the VCO 10 by the frequency adjustment mechanism of the present embodiment.

When the power is turned on, first, the CPU 60 sets the adjustment voltage Vs applied to the variable capacitance diode 20 to 1/2 of the power supply voltage Vcc (step 100). Here, the adjustment voltage Vs which is 1/2 of the power supply voltage Vcc is applied to the variable capacitance diode 20 in the control operation of the adjustment voltage Vs performed later, in the direction of increasing or decreasing the adjustment voltage Vs. This is because it is unclear whether the characteristic is changed or not. The characteristic of the VCO 10 corresponding to such an adjustment voltage Vs can be adjusted with respect to either of the curves B and C shown in FIG.

Next, the CPU 60 sets the frequency division ratio N of the frequency divider 30 to a value corresponding to the lower limit value fmin of the required variable range of the oscillation frequency (step 101). For example, when the lower limit value fmin of the frequency is 1.45 GHz and the frequency of the reference signal input to the phase comparator 40 is 100 kHz, the division ratio N is 14500.

Next, the CPU 60 converts the control voltage Vc applied from the LPF 50 to the VCO 10 into digital data by the A / D converter and reads it (step 102), and determines whether the value is within a predetermined range. Is determined (step 103).

FIG. 4 is a diagram showing the relationship between the lower limit value fmin of the variable range of the oscillation frequency and the control voltage Vc applied to VC010. As shown by the characteristic line D in the figure, when the control voltage Vc is varied, the frequency range of the oscillation frequency fosc of VCO 10 becomes fmi When the entire range from n to fmax is included, the control voltage Vc corresponding to the lower limit value fmin of the oscillation frequency of the VCO 10 is included in the predetermined range V1 to V2 shown in FIG. Should be. In step 103 described above, the CPU 60 determines whether or not the read control voltage Vc is included in the predetermined range V1 to V2.

When the control voltage Vc is within the predetermined range, there is no need to change the adjustment voltage Vs. Therefore, the adjustment voltage data corresponding to the value of the adjustment voltage Vs at this time is stored in the memory 70 ( Step 104) End the adjustment operation of the variable range of the oscillation frequency. If the control voltage Vc is not included in the predetermined range, the CPU 60 determines whether or not the control voltage Vc has exceeded the upper limit value V2 of the predetermined range (step 105). The case where the control voltage Vc exceeds the upper limit V2 corresponds to the case corresponding to the characteristic line C shown in FIG. 6, and it is necessary to increase the oscillation frequency of the VCO 10 with respect to the control voltage Vc. is there. Therefore, when the control voltage Vc exceeds the upper limit value V2 of the predetermined range, the CPU 60 performs control to increase the adjustment voltage Vs applied to the variable capacitance diode 20 by a predetermined amount (step 106). . As a result, the capacitance Cs of the variable capacitance diode 20 decreases, and the oscillation frequency fosc operates to change to a higher value by a predetermined amount. However, in practice, the oscillation frequency f osc of the VCO 10 is fixed to the lower limit value fmin of the variable range, so that the control voltage Vc applied to the VCO 10 becomes lower. Then, returning to step 102, the adjustment operation is repeated.

Conversely, if the control voltage Vc is lower than the lower limit value V1 of the predetermined range, a negative determination is made in step 105 described above, and then the CPU 60 determines the adjustment voltage Vs to be applied to the variable capacitance diode 20. Perform control to lower only by a fixed amount (Step 107). C As a result, since the capacitance Cs of the variable capacitance diode 20 increases, the oscillation frequency f osc operates to change to a higher value, and as a result, the VCO 10 decreases. The lower limit of the variable range; the control voltage Vc corresponding to fmin increases. Then, returning to step 102, the adjustment operation is repeated. In this manner, when the control voltage Vc corresponding to the lower limit value fmin of the variable range of the oscillation frequency of VCO 10 falls outside the predetermined range V1 to V2, the control voltage Vc is included in the predetermined range. The value of the adjustment voltage Vs is adjusted The adjustment voltage data at this time is stored in the memory 70, and a series of adjustment operations ends.

As described above, the frequency adjustment mechanism of the present embodiment is configured such that when the variable range of the oscillation frequency of the VCO 10 does not include the entire range from the lower limit value of the required oscillation frequency: min to the upper limit value fmax, The variable range of the oscillation frequency of the VCO 10 is changed by automatically adjusting the value of the adjustment voltage Vs applied to the variable capacitance diode 20. Therefore, when the VCO 10 is manufactured, if the operator adjusts the variable range of the oscillation frequency of the VCO 10 while looking at the monitor screen or the like displaying the oscillation frequency characteristics, there is no need to perform complicated work. The variable range of the oscillation frequency of VCO 10 can be easily adjusted.

In addition, the adjustment voltage data corresponding to the value of the adjustment voltage Vs applied to the variable capacitance diode 20 when the variable range of the oscillation frequency of the VCO 10 is adjusted is stored in the memory Ί0. For example, it is only necessary to read this adjustment voltage data from the memory 70 and apply the corresponding adjustment voltage Vs to the variable capacitance diode 20.Therefore, the processing load when the adjustment voltage Vs is automatically adjusted Can be reduced.

Also, in the initial state of the adjustment operation, the variable range of the oscillation frequency of the VCO 10 is changed in an arbitrary direction by setting the adjustment voltage Vs applied to the variable capacitance diode 20 to 1/2 of the power supply voltage Vcc. It is possible to reliably secure a predetermined variable range even when the variation in the oscillation frequency of the VCO 10 is large.The present invention is not limited to the above-described embodiment. Various modifications can be made within the scope of the gist. For example, in the above-described embodiment, a clap oscillation circuit, which is a kind of LC oscillation circuit, is used as the VCO 10. Thus, the variable range of the oscillation frequency may be automatically adjusted.

In the above-described embodiment, the oscillation frequency of the VCO 10 is set to the lower limit value fmin of the required variable range, and the control voltage Vc applied to VC01 0 at this time falls within the predetermined range V1 to V2. Although it was determined whether or not it was included, the oscillation frequency of VC010 was set to the upper limit value fmax of the required variable range, and the control applied to VCO10 at this time was set. It may be determined whether the voltage Vc is included in the predetermined range VI ′ to V2 ′. Alternatively, instead of reading the value of the control voltage Vc corresponding to the lower limit value: min or the upper limit value f max and performing the predetermined adjustment operation, read the value of the control voltage Vc corresponding to the intermediate value: f mid. Is also good. Industrial applicability

As described above, according to the present invention, the variable range of the oscillation frequency of the voltage-controlled oscillator is determined based on the value of the control voltage applied to the voltage-controlled voltage when the voltage-controlled oscillator is oscillated at the predetermined frequency. It is adjusted automatically, and the variable range of the oscillation frequency can be easily adjusted.

Claims

The scope of the claims

1. A voltage-controlled oscillator that performs a predetermined oscillating operation according to the applied control voltage, and based on a value of the control voltage corresponding to the predetermined frequency when the voltage-controlled oscillator is oscillated at a predetermined frequency. A variable range adjusting means for adjusting a variable range of the oscillation frequency of the voltage controlled oscillator;

A voltage-controlled oscillator adjustment method comprising:

2. The voltage controlled oscillator includes a first element constant variable element whose element constant can be changed according to the applied control voltage, and a second element constant variable element whose element constant can be changed according to the applied adjustment voltage. And an element constant variable element of

2. The voltage controlled oscillator adjustment method according to claim 1, wherein the value of the adjustment voltage is adjusted by the variable range adjustment means.

3. The voltage controlled oscillator includes an LC resonance circuit,

The first element constant variable element is a first variable capacitance diode connected in parallel with the inductor in the LC resonance circuit, and the second element constant variable element is connected in series with the inductor in the LC resonance circuit. 3. The voltage-controlled oscillator adjusting method according to claim 2, wherein the voltage-controlled oscillator is a second variable capacitance diode connected to the voltage-controlled oscillator.

4. The variable range adjusting means, when the voltage controlled oscillator is oscillated at the predetermined frequency, when the value of the control voltage applied to the control voltage oscillator is out of a predetermined range, 3. The voltage-controlled oscillator adjusting method according to claim 2, wherein the adjusting voltage is changed until the value of the control voltage falls within the predetermined range.

5. The voltage controlled oscillator adjustment method according to claim 2, wherein said variable range adjustment means sets said adjustment voltage to approximately 1/2 of a power supply voltage at the start of an adjustment operation.

6. The voltage-controlled oscillator adjustment method according to claim 2, further comprising a voltage value storage means for storing the value of the adjustment voltage adjusted by the variable range adjustment means.

7. A frequency divider that performs a predetermined frequency division operation on an output signal of the voltage controlled oscillator, A phase comparator that performs a phase comparison between the frequency-divided signal output from the frequency divider and a reference signal having a predetermined frequency;

A low-pass filter that generates the control voltage based on an output signal of the phase comparator;

Further comprising: setting the frequency division ratio of the frequency divider to a predetermined value by the variable range adjusting means, so that the voltage controlled oscillator oscillates at the predetermined frequency. The voltage-controlled oscillator adjustment method according to item 1.

8. The voltage-controlled oscillator adjusting method according to claim 1, wherein the variable range adjusting means is configured by a CPU which performs an adjusting operation by executing a predetermined adjusting program.