JPH0645924A - Sweep frequency generating device and tuner adjusting method using the same - Google Patents

Abstract

PURPOSE:To highly accurately output plural kinds of adjusting sweep frequency signals. CONSTITUTION:A sweep frequency oscillation part 20 oscillates variation frequency (fr) to be changed with prescribed width by sweep voltage Vs impressed from a sweep control part 21 and plural oscillation parts 30, 40, 50 output mutually different reference frequency f1, f2, f3. These outputs are mixed by a frequency mixing part 27 and an output fs3 to be changed at its frequency is obtained based upon respective reference frequency f1, f2, f3. The output fs3 is inputted to a tuner 4 and the receiving frequency of the tuner 4 is switched in the order of f1, f2 and f3, so that receiving outputs corresponding to respective reference frequency values f1, f2, f3 can be adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sweep frequency generator that outputs a frequency signal that fluctuates around a predetermined frequency in order to adjust the tuning output of the tuner, and a tuner using this sweep frequency generator. Adjustment method.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram showing an example of tuner adjustment work. In the adjustment work of various tuners such as an FM radio tuner, an AM radio tuner, and a television tuner, the sweep frequency generator shown by reference numeral 1 in FIG. 9 is used. FIG. 10 shows the configuration of a conventional sweep frequency generator 1. The sweep frequency generator 1 is composed of a voltage controlled oscillator (VCO) 2, a sweep controller 3 for applying a control voltage Vc to the voltage controlled oscillator 2, and the like.

The sweep controller 3 intermittently generates a continuously changing saw-tooth-shaped control voltage Vc (see FIG. 11), which is supplied to the voltage controlled oscillator 2 and, as a result, the voltage controlled oscillator 2. From, a signal having a sweep frequency fs0 whose frequency continuously changes in accordance with the change of the control voltage Vc is obtained from FIG. When the tuner 4 to be adjusted is, for example, an FM radio tuner, the sweep frequency f
s0 changes continuously from 76 to 90 MHz.

In the adjustment work, the reception tuning frequency of the tuner 4 is fixed to a predetermined value, and the signal of the sweep frequency fs0 from the sweep frequency generator 1 is input to the antenna input section of the tuner 4. The IF output at this time is monitored by the monitor 5. Looking at the output intensity of the IF frequency (10.7 MHz) displayed on the screen 5a of the monitor 5, the tuning part of the tuner 4 and the like are adjusted so that this output intensity has an optimum value. In the actual FM radio tuner adjustment work, the tuning frequency of the tuner 4 is, for example, 76, 93, 90.
Switching is performed in three stages such as MHz, and adjustment is performed so that the output intensity of the IF frequency is optimized at each of the three stages.

[0005]

The conventional sweep frequency generator 1 and the tuner adjusting method using this device have the following problems. First, in the sweep frequency generator 1 shown in FIG. 10, since the sawtooth control voltage Vc is output from the sweep controller 3 to control the voltage controlled oscillator 2, the output sweep frequency fs0 is not stable. There is.

Further, since the frequency band of the signal having the sweep frequency fs0 is limited to the height width A of the saw blade voltage of the control voltage Vt shown in FIG. 11, the frequency fluctuation band may not be obtained with a sufficient width. . Further, since the frequency is swept in a constant frequency range, the sweep frequency cannot be changed stepwise from one frequency band to another frequency band.

Further, in the conventional tuning method of the tuner 4 using the sweep frequency generator 1, the received output is adjusted with respect to the tuning frequency by changing the time, for example, every three stages of frequency, so that the adjusting work takes time. In addition, it is not possible to compare the adjustment results adjusted by each of the three frequencies.

The present invention solves the above-mentioned conventional problems, and provides a sweep frequency generator capable of stabilizing the sweep frequency and obtaining a signal of the sweep frequency with reference to a plurality of frequencies. Is intended.

A further object of the present invention is to provide a tuner adjustment method that enables efficient tuner adjustment using a plurality of sweep frequency signals.

[0010]

In the sweep frequency generator according to the present invention, a voltage controlled oscillator whose frequency is controlled by a voltage and a control voltage for stabilizing the oscillation frequency from the voltage controlled oscillator are used for the voltage control. A phase control unit that feeds back to the oscillation unit, a sweep control unit that generates a sweep voltage that changes positively and negatively around a predetermined voltage, and an addition unit that adds the sweep voltage to a feedback path to the voltage control oscillation unit. It is characterized by being provided.

In the above means, the control voltage immediately before the sweep voltage is output from the sweep control unit is held in the feedback path to the voltage controlled oscillator and before the adder, and the sweep voltage is output. There is provided a control voltage holding unit that releases this holding immediately after the stop.

Further, a plurality of oscillators for generating signals having different reference frequencies, the sweep frequency generator, and fluctuations from the sweep frequency generator in the respective reference frequency signals emitted from the oscillators. And a frequency mixing section for mixing frequencies to obtain sweep frequencies of a plurality of components centered on the reference frequency from each of the oscillating sections.

The tuner adjusting method according to the present invention is
The sweep frequencies of a plurality of components emitted from the sweep frequency generator are input to the antenna input section of the tuner, and the tuning frequency of the tuner is sequentially switched so as to match the reference frequencies from the plurality of oscillator sections. The tuning output of the tuner is adjusted based on the sweep frequency.

[0014]

In the above means, a phase control section such as a loop lock section for stabilizing the oscillation frequency from the voltage controlled oscillation section is provided so that a stable frequency output can always be obtained. By adding the sweep voltage to the feedback path of, a sweep frequency signal centered on a stable reference frequency can be obtained.

In the second means, the control voltage fed back from the phase controller is held immediately before the sweep voltage is added, and the hold of the control voltage is released after the sweep voltage is added. Therefore, when the sweep voltage is not added, a stable reference frequency is generated by the phase control unit, and when the sweep voltage is added, the phase control is canceled so that a highly accurate frequency sweep according to the sweep voltage is performed. Become.

In the third means, the fluctuating frequency generated by the sweep frequency generator is frequency-mixed with a plurality of reference frequency signals to obtain a sweep frequency signal centered on the plurality of reference frequencies.

In the fourth means, the sweep frequency signals centering on the above-mentioned plurality of reference frequencies are input to the tuner, and the reception frequency of the tuner is sequentially switched so as to become the reference frequency. It is possible to simultaneously adjust tuning outputs and compare tuning outputs for a plurality of reference frequencies.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a circuit configuration of a sweep frequency generator according to a first embodiment of the present invention. The sweep frequency generator S1 shown in FIG. 1 has a sweep oscillator 10 and a sweep controller 11. The sweep oscillator 10 is provided with a voltage controlled oscillator (VCO) 12, and the oscillation output from the voltage controlled oscillator 12 is a PLL as a phase controller.
(Phase Lock Loop) is input to the circuit 13, and this PLL
The control voltage Vc from the circuit 13 is fed back to the VCO 12, and the VCO 12 can perform stable frequency oscillation by this loop lock. PLL circuit 13
An adder 14 is provided in the feedback path of the control voltage Vc from the VCO to the VCO 12. The adder 14 adds the sweep voltage Vs to the control voltage Vt.

The sweep voltage Vs is output from the sweep controller 11. FIG. 2 shows the sweep voltage Vs generated by the sweep controller 11. The sweep voltage Vs is a voltage that intermittently linearly changes from -V1 to + V1 around a predetermined reference voltage, for example, 0 volt, and the potential difference B from -V1 to + V1 causes
The sweep width is determined.

In the sweep frequency generator S1 shown in FIG.
The sweep voltage Vs shown in FIG. 2 output from the sweep controller 11 is added to the control voltage Vc by the adder 14. In the VCO 12, a voltage swinging with a potential difference of B around the control voltage Vc from the PLL circuit 13 is applied, and oscillation is performed at a frequency based on this voltage. Therefore, a signal having the sweep frequency fs1 whose frequency fluctuates within a predetermined range around the reference frequency is obtained from the output unit 15.

In the adjustment work of the tuner 4, the signal of the sweep frequency fs1 is input to the antenna input section 4a of the tuner 4, and the tuner 4 receives the frequency that changes linearly around the reference frequency. Therefore, the IF output from the tuner 4 is monitored by the monitor 5 as shown in FIG.
The output of the reception frequency is adjusted, for example, by monitoring at.

FIG. 3 is a block diagram showing a sweep frequency generator S2 according to a second embodiment of the present invention. This second
The sweep frequency generator S2 according to the embodiment includes the sweep oscillator 2
0, a sweep control section 21, a gate circuit 22, a reference clock generation section 23 and the like.

The sweep oscillator 20 has a VCO 12 and a PLL circuit 13 for stabilizing the oscillation frequency of the VCO 12.
A low pass filter (LPF) 24 and an adder 14 are provided, and a sample and hold circuit 25 is provided before the adder 14. The adder 14
Then, the sweep voltage Vs from the sweep controller 21 is added to the sampled and held control voltage Vc. The gate circuit 22 has a holding time indicated by T1 in FIG.
The PLL lock time indicated by T2 is set.

Next, the operation will be described. The frequency output oscillated by the VCO 12 is input to the PLL circuit 13,
The control voltage Vc output from the PLL circuit 13 and passed through the LPF 24 is fed back to the VCO 12, and the VCO 12 oscillates with a stable frequency due to the loop lock. In the gate circuit 22, based on the reference clock from the reference clock generator 23, as shown in FIG.
The high level command signal G is applied to the sweep control section 21 and the sample and hold circuit 25 for the holding time of. The times T1 and T2 other than the above may be the same time width or different time widths.

In the sweep control section 21, a sweep that linearly changes from -V1 to + V1 around a predetermined voltage, for example, 0 volt, for a time T1 when the high level command signal G from the gate circuit 22 is given. The voltage Vs is generated, and this is added to the control voltage Vc by the adder 14. Further, the high level command signal G from the gate circuit 22.
At the time T1 when is given, the sample and hold circuit 25 starts the hold operation. That is, the control voltage Vc immediately before T1 is sampled, and the sampled control voltage Vc is held for the time T1. The hold is released after the time T1 has elapsed.

Accordingly, when the sweep voltage Vs is being output from the sweep controller 21 at the time T1 by the command signal from the gate circuit 22, the sample and hold circuit 25 puts the control voltage Vc in the hold state, and the PLL circuit. The loop lock by 13 is released. Then, the hold of the sample and hold circuit 25 is released only during the time T2 when the sweep voltage Vs is not output, and P
The loop lock by the LL circuit 13 comes to work.

That is, in the PLL circuit 13, the VCO 12
The control voltage Vc that suppresses the fluctuation of the oscillation frequency of the VCO 12 is generated, but in this embodiment, when the sweep voltage Vs is added to the control voltage Vc by the adder 14 and the oscillation frequency of the VCO 12 changes, the PLL The loop lock via circuit 13 is disabled. Therefore, during this period, the sweep voltage Vs whose voltage changes linearly is added as it is to the constant control voltage Vc, and the VCO 12
As shown in FIG. 4B, the VCO 12 outputs a signal having a sweep frequency fs2 whose frequency changes from + f1 to -f1 around the reference frequency f0.

However, the time T1 during which the sweep voltage Vs is added
The control voltage Vc at is a value obtained by sampling and holding the control voltage Vc when the immediately preceding loop lock is operating. Therefore, the control voltage Vc to which the sweep voltage Vs is added stabilizes the oscillation of the reference frequency f0. Therefore, the reference frequency f0 of the sweep frequency fs2 is always stable.

FIG. 5 is a circuit block diagram showing a sweep frequency generator S3 according to a third embodiment of the present invention, and FIG.
It is a circuit block diagram which shows the tuning method of the tuner using the sweep frequency generator S3 by an Example. The sweep frequency generator S3 shown in FIG. 5 is provided with one set of the same sweep oscillating units 20 as shown in FIG. 3, and further includes first to third oscillating units 30, which oscillate different reference frequency signals,
40 and 50 are provided for each set.

The sweep oscillating section 20 has the same structure as in FIG.
A voltage controlled oscillator (VCO) 12, a PLL circuit 13,
An LPF 24, a sample and hold circuit 25, and an adder 14 are provided. The oscillation output from the VCO 12 is P
A control voltage V that is input to the LL circuit 13 and stabilizes the oscillation frequency of the VCO 12 by phase comparison inside the PLL circuit 13.
c is generated and is fed back to the VCO 12 via the sample and hold circuit 25 and the adder 14.

As shown in FIG. 6, the sweep control unit 2
The sweep voltage Vs generated at 1 is added to the control voltage Vc by the adder 14. The gate command signal G generated by the clock signal from the reference clock generator 23 is used to operate the sample and hold circuit 25. The first oscillator 30 is provided with a VCO 31, whose oscillation output is input to the PLL circuit 32, and L
The control voltage Vc1 passed through the PF33 is fed back to the VCO 31,
A loop lock that stabilizes the oscillation frequency of the VCO 31 is formed. Similarly, the second oscillator 40 has a VCO 41
And a PLL circuit 42 and an LPF 43, and the third oscillator 50 includes a VCO 51, a PLL circuit 52, and an LPF 53.
Is provided.

The three oscillating units 30, 40 and 50 have the same circuit configuration, but the respective oscillating units 30 and 4 are
The reference frequency signals f1, f2, and f3 that are stably oscillated by loop lock at 0 and 50 have different frequencies. In the case of a sweep frequency generator used for adjusting an FM radio tuner, for example, f1 = 76 MHz, f2 = 83 MHz, f3 = 90 MH
z.

As shown in FIG. 5, the fluctuating frequency fr output from the sweep oscillator 20 and the oscillators 30, 40 and 50 are shown.
The reference frequency signals f1, f2, and f3 oscillated from are frequency-mixed by the frequency mixer 27. Frequency mixing unit 27
First, the reference frequency f1 emitted from the first oscillating unit 30 and the fluctuating frequency fr are mixed to obtain F1.
A frequency signal of = (f1−fr) is generated. Similarly second
F2 with respect to the reference frequency f2 emitted from the oscillator 40 of
= (F2-fr) is generated, and F3 = (f3-fr) is generated for the reference frequency f3 emitted from the third oscillator 50. Then, the frequency signal on which the frequency components of F1, F2 and F3 are superimposed is output as the signal of the sweep frequency fs3.

FIG. 6 shows an FM which is adjusted by the sweep frequency fs3 from the sweep frequency generator S3 shown in FIG.
Radio tuner 4 is shown. The front end of the FM radio tuner 4 is provided with an antenna tuning unit 4b connected to the antenna input unit 4a, and the RF following the antenna tuning unit 4b is provided.
An amplifier 4c, a mixer (frequency mixer) 4d, a local oscillator 4e, an IF amplifier 4f, an IF detector 4g, etc. are provided. Further, the PLL circuit 4 is provided in the frequency selecting section 4i for selecting the oscillation frequency of the local oscillator 4e and the antenna tuning section 4b.
The tuning voltage Vt from h is given. In this tuner 4, the tuning voltage V output from the PLL circuit 4h
By t, the antenna tuning unit 4b can tune a predetermined frequency, and the tuning voltage Vt changes the tuning voltage Vt.
By being input to i, the oscillation frequency of the local oscillator 4e is determined, and the IF frequency of 10.7 MHz is generated from the mixer 4d.

Next, the sweep frequency generator S shown in FIG.
The operation of 3 and the adjusting method of the tuner 4 using this sweep frequency generator will be described. The gate circuit 22 generates a gate command signal G which is at a high level in the T1 time width by the clock generated from the reference clock generation unit 23 shown in FIG. 6 as shown in FIG. 7D. The interval at which the gate command signal G is generated is T2 hours.

The operation of the sweep oscillating section 20 is the same as that shown in FIGS. 3 and 4, and while the gate command signal G is being output for T1 time, the sample and hold circuit 25 outputs the control voltage immediately before it. Vc is sampled and held for T1 time. During this T1 time, the loop lock fed back from the PLL circuit 13 is released. Then, while the gate command signal G is being output, the sweep control unit 21
Outputs the sweep voltage Vs shown in FIG. 7 (A).
This sweep voltage Vs has a voltage that changes linearly from -V to + V with 0 V as the center, and this is added to the control voltage Vc by the adder 14. Therefore, the sweep oscillation unit 20 outputs the fluctuating frequency fr whose frequency fluctuates within a certain range.

Further, each of the first to third oscillators 3
From 0, 40, and 50, stable reference frequencies of f1, f2, and f3 are always output by the loop lock using the PLL circuit, and the frequency mixing unit 27 performs frequency mixing,
The signals of the frequencies of F1, F2, and F3 whose frequencies fluctuate within a certain width with respect to f1, f2, and f3, respectively, are superimposed and output as the sweep frequency fs3. As shown in FIG. 7B, the signal of the sweep frequency fs3 is output every time T1 when the gate command signal G is output. In the time zone of T2, the superposed reference frequencies f1, f2, and f3 are continuously output.

A frequency switching unit 28 is connected to the PLL circuit 4h of the tuner 4, and a gate command signal G from the gate circuit 22 is applied to the frequency switching unit 28. In the frequency switching unit 28, the reception tuning frequency of the tuner 4 is f1 at the time T1 when the gate command signal G is input.
The reception tuning frequency is changed to f2 at the next T1, and the reception tuning frequency is changed to f3 at the next T1, and this is repeated (see FIG. 7C). ).

As described above, the sweep frequency fs3 is a superposition of the frequencies F1, F2, F3 whose frequencies fluctuate within a predetermined width around the respective reference frequencies f1, f2, f3. And the tuner 4 has an interval of time T2,
The reception tuning frequency is switched in the order of f1, f2, f3. Therefore, the IF output of the tuner 4 is displayed on the screen 5a of the monitor 5.
The IF outputs (a), (b), and (c) when the respective frequencies of f1, f2, and f3 are received are displayed in order. By displaying the display in this order by dividing the screen, for example, the tuning IF outputs for the three frequencies f1, f2, and f3 can be displayed simultaneously. Based on the IF output simultaneously displayed, the antenna tuning unit 4b
And the frequency selection unit 4i are adjusted.

In the embodiments of FIGS. 5 and 6, the frequency mixing section 27 is shown as one circuit block, but frequency mixers are individually provided for the outputs of the respective frequencies f1, f2 and f3, F1 by each frequency mixer,
The fluctuating frequency fr may be mixed into each of f2 and f3. Further, in the embodiment shown in the figure,
Although 50 and 3 sets are provided, 4 or more sets may be provided.

[0041]

As described above, according to the invention of claim 1,
Since a phase control unit such as a PLL is provided as the oscillation unit of the sweep frequency generator, a stable sweep frequency signal can be obtained.

According to the second aspect of the present invention, the sweep voltage is added in a state where the phase control of the PLL or the like is released, and a signal whose frequency fluctuates is obtained. Therefore, the reference frequency is stable, and the frequency is accurately adjusted. A varying sweep frequency signal can be obtained.

According to the third aspect of the present invention, a swept frequency output in which the frequency fluctuates around a plurality of reference frequencies is obtained, so that it is highly useful when adjusting with a plurality of frequency components.

According to the fourth aspect of the present invention, since the IF output from the tuner is output as the reception frequency is changed in sequence, the tuning outputs for a plurality of frequencies can be displayed at the same time. The reception adjustment for the frequency can be easily performed.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a sweep frequency generator according to a first embodiment of the present invention,

FIG. 2 is a waveform diagram showing a sweep voltage added to an adder in the sweep frequency generator shown in FIG.

FIG. 3 is a circuit block diagram showing a sweep frequency generator according to a second embodiment of the present invention,

4 (A), (B) and (C) are waveform charts showing waveforms of respective parts of the sweep frequency generator of FIG.

FIG. 5 is a circuit block diagram of a sweep frequency generator according to a third embodiment of the present invention,

FIG. 6 is a circuit block diagram showing a sweep frequency generator according to a third embodiment and a tuner adjusting operation using the same.

7 (A), (B), (C), and (D) are waveform diagrams showing the waveforms of the respective portions of FIG.

FIG. 8 is an explanatory diagram of a monitor,

FIG. 9 is a circuit block diagram showing a state in which a tuner is adjusted by a conventional sweep frequency generator.

FIG. 10 is a circuit block diagram of a conventional sweep frequency generator,

11 is a waveform diagram showing a control voltage from the controller shown in FIG.

FIG. 12 is a diagram showing the relationship between control voltage and oscillation frequency,

[Explanation of Codes] 4 Tuner 10 Sweep Oscillator 11 Sweep Control Unit 12 Voltage Controlled Oscillator (VCO) 13 PLL Circuit as Phase Control Unit 14 Adder 20 Sweep Oscillator 21 Sweep Control Unit 22 Gate Circuit 24 Low Pass Filter 25 Samples・ Hold circuit 27 Frequency mixing section 30, 40, 50 Reference frequency oscillation section Vc Control voltage Vs Sweep voltage fr Fluctuation frequency f1, f2, f3 Reference frequency fs1, fs2, fs3 Sweep frequency signal

Claims (4)

[Claims] 1. A voltage controlled oscillator whose frequency is controlled by a voltage, a phase controller which feeds back a control voltage for stabilizing the oscillation frequency from the voltage controlled oscillator to the voltage controlled oscillator, and a predetermined voltage. A sweep frequency generating device comprising: a sweep control unit that generates a sweep voltage that changes positively and negatively around the center; and an adder unit that adds the sweep voltage to a feedback path to the voltage controlled oscillator. . 2. The feedback path to the voltage controlled oscillator and the previous stage of the adder holds the control voltage immediately before the sweep voltage is output from the sweep controller and stops the output of the sweep voltage. 2. The sweep frequency generator according to claim 1, further comprising a control voltage holding unit for releasing the holding immediately after. 3. A plurality of oscillators for respectively generating different reference frequency signals, the sweep frequency generator according to claim 2, and the sweep frequency generator for each of the reference frequency signals emitted from the plurality of oscillators. And a frequency mixer for obtaining a sweep frequency of a plurality of components around the reference frequency from each of the oscillators. 4. A sweep frequency of a plurality of components emitted from the sweep frequency generator according to claim 3 is input to an antenna input section of a tuner, and a tuning frequency of the tuner is adjusted to a reference frequency from the plurality of oscillating sections. Switching in sequence,
Tuner tuning method that adjusts the tuner tuning output based on the sweep frequency centered on each reference frequency.