JPH0543528Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention is a variable control oscillator (VCO) for audio signals due to the nonlinearity of the voltage/capacitance curve, which is a characteristic unique to electronic volumes.
In wireless communication equipment, the variable control oscillator (VCO) has been devised to operate optimally by expanding the usable frequency band by correcting the output of the electronic volume to the optimal value so that the change in the modulation value is within the standard range. Variable
Regarding control oscillator (VCO) modulation depth correction circuit.

[Conventional technology]

As shown in FIG. 2A, the output of the microphone amplifier 2 is inputted via an electronic volume 3 to the VCO of a phase lock (PLL) circuit that determines the modulation frequency of the radio, and the VCO 5 is modulated with an audio signal.

However, when using a wide frequency band due to the nonlinearity of the voltage/capacitance curve of the electronic volume 3, a mismatch between the voltage-frequency relationship and the degree of change of the electronic volume 3 arises, and the VCO modulation value of the audio signal changes. Therefore, as a countermeasure, the frequency band of each radio device is narrowly limited to 20MHz, etc., and the frequency specifications for each radio device are varied.

Therefore, it has been essential to produce a wide variety of equipment so that suitable radio equipment can be selected depending on the intended frequency.

[Problem that the invention attempts to solve]

As an improvement measure when using the wide range of frequency bands mentioned above, the electronic volume 3 shown in Figure 2B and
A method is adopted in which the FET attenuator 12 is interposed between the VCO 5, but since the dynamic range of the FET attenuator 12 is narrow, the nonlinearity of the electronic volume 3 is still not sufficiently improved and the effect is not improved.

For example, if the modulation depth condition is ±4KHz at a frequency of 430MHz, it will become 460MHz±5K if the frequency used is extended to a wide band.
It changes up to Hz.

Therefore, there is a demand for the development of a VCO correction circuit that divides the characteristic voltage-capacitance curve of the electronic volume 3 into smaller parts and controls the VCO modulation degree of the audio signal so that the angle between the tangents of each part of the curve is constant.

[Means for solving problems]

In this invention, in order to overcome the above problems, the first
As shown in the figure, the audio input circuit connected to the VCO 5 of the phase lock circuit in the radio includes a microphone 1, a microphone amplifier 2, an electronic volume 3,
It consists of a 1/N attenuator 4.

A modulation adjustment volume 6 is connected to the electronic volume 3, and a circuit consisting of an analog/digital converter 7, a memory section 8, an address control section 9, and a digital/analog converter 10 is connected to the modulation adjustment volume 6. do.

By changing the voltage of the modulation adjustment volume 6,
Add modulation to VCO5 and confirm in a plot that the modulation degree of VCO is within the standard.

The optimal operating conditions for the electronic volume 3 thus determined are stored in the memory unit 8 via the analog/digital converter 7 and plotted in correspondence with the frequency used by the VCO 5.

Each piece of plotted data receives a signal from the address control section 9 and is applied from the memory section 8 to the electronic volume 3 via the digital/analog converter 10 to keep the modulation degree of the VCO 5 within the standard.

The set switch 11 is used to input plot values into the memory section 8, and is turned off when the communication device is used.

The operating conditions of the electronic volume 3 are determined in accordance with the frequency used by the VCO 5, and the frequency signal input from the microphone 1 can be optimally modulated to the VCO 5.

The electronic volume 3, which operates under optimal conditions over a wide frequency band of the VCO 5, always keeps the modulation degree of the VCO 5 within the standard.

That is, the audio input from the microphone 1 is amplified by the microphone amplifier 2, then attenuated by the electronic volume 3, and then 1/N by the 1/N attenuator 4.
The attenuation is fixed to N, and the VCO 5 is subjected to specified modulation corresponding to the frequency in use.

[Function and Examples]

FIG. 1 is a block diagram showing a modulation degree correction circuit within the VCO band of the present invention.

Modulation adjustment volume 6 for electronic volume 3
Apply more various voltages, check the degree of modulation that the corresponding electronic volume 3 gives to the VCO 5, record the degree of attenuation, plot the data, and send it to the memory section 8, and output the electronic volume corresponding to the frequency used by the VCO 5. The optimum conditions for volume 3 can be extracted.

The modulation adjustment volume 6, which makes the most of the variation range, scans the appropriate output voltage of the electronic volume 3, and then stores it in the memory unit 8 together with the signal from the address control unit 9 via the analog/digital converter 7. This storage condition is sent to the electronic volume 3 from the digital/analog converter 10, and the modulation value of the VCO 5 of the audio signal input from the microphone 1 can be held constant.

The frequency band used by the wireless device in this example is 400-500MHz in the general market, and the frequency band covered by one conventional wireless communication device is 10-20MHz.
Expanding wireless communication to 100MHz,
This overcomes the instability of the modulation depth corresponding to this wide band.

The audio signal input from the microphone 1 is amplified to, for example, 5V by the microphone amplifier 2, then attenuated to 2V by the electronic volume 3, further fixedly attenuated to 1V by the 1/2 attenuator 4, and then sent to VCO 5 for specified modulation. is added.

The output characteristics of the electronic volume 3 are nonlinear as seen in a variable capacitor.

The electronic volume 3 has an output range of, for example, 0 to 5 V in response to an audio signal input, but the degree of modulation of the VCO 5 changes due to its nonlinear characteristics.

Therefore, in order to keep the VCO modulation degree within the standard,
This electronic volume 3 according to the VCO modulation frequency
control the output voltage to the optimum value.

Modulation adjustment volume 6 is set switch 11
By turning on and applying a voltage varying between 0 and 5V, it is possible to give the electronic volume of the electronic volume 3 a prescribed degree of attenuation.

In addition, the voltage of the modulation adjustment volume 6 is set so that the resolution of the analog/digital converter is wide.
It is preferable to set it as high as possible.

The attenuation of the electronic volume 3 varies depending on the input voltage, but the attenuation is adjusted to within an optimum value by the voltage of the modulation adjustment volume 6.

Here, the modulation adjustment volume 6 is used only when accumulating data for adding an appropriate degree of modulation to the VCO, and after determining the appropriate voltage to be applied to the electronic volume 3, the set switch 11 is always
Turn off.

To correct the modulation depth, first set switch 1.
1 is turned on, a voltage of 0 to 5V is applied to the electronic volume 3 from the modulation adjustment volume 6, and a prescribed modulation is applied to the VCO 5.

Using the same operation, change the voltage applied to the electronic volume 3 from the modulation adjustment volume 6, track the change in the degree of modulation of the VCO 5, and adjust the voltage of the modulation adjustment volume 6 while checking that the degree of modulation is within the standard. - Storing the modulation degree relationship in the memory section 8 through the analog/digital converter 7 and by the memory switch.

The above operation is repeated to plot the voltage-frequency modulation degree relationship of the modulation adjustment volume 6 within the frequency band used, and the optimum output range of the electronic volume 3 is determined.

The plot width in this case is the covered frequency band 100M.
For example, Hz is divided into 20 MHz widths, the 20 MHz is further divided into 1/5, and data of Δ every 4 MHz is accumulated.

As a result, individual plot data for selecting the optimum voltage between 0 and 5 V to be input from the modulation adjustment volume 6 to the electronic volume 3 are stored in separate addresses by the address control section 9, and linked to the frequency within the band used. and it works.

The addressed data is set to switch 11.
By turning OFF, a voltage giving an appropriate corrected modulation degree to the VCO 5 is applied to the electronic volume 3 through the digital/analog converter 10,
The optimum audio level is always applied to the VCO 5, and the radio can be used under good modulation conditions that cover a wide range of frequency bands and correspond to the frequency bands within the range.

[Effect of the invention]

With the modulation depth correction circuit within the VCO band of this invention,
It becomes easier to design radio equipment that covers a wide range of frequencies, eliminates variations in functionality between equipment sets, and eliminates high costs due to the use of micro-process units. This eliminates the complexity and high cost of narrowly limiting the band and requiring multiple devices depending on the intended frequency, so it can be expected to be used in a wide range of applications.

[Brief explanation of the drawing]

FIG. 1 shows a block diagram of a modulation degree correction circuit within the VCO band according to the present invention, and FIG. 2 shows a conventional example thereof. 1... Microphone, 2... Microphone amplifier,
3...Electronic volume, 4...1/N attenuator, 5
...VCO, 6...Modulation adjustment volume, 7...
Analog/digital converter, 8...memory section,
9...Address control section, 10...Digital/analog converter, 11...Set switch, 12...FET attenuator.

Claims (1)

[Scope of utility model registration request] An audio input circuit having an electronic volume is connected to a variable control oscillator of a phase lock circuit that determines the modulation frequency of the radio, a memory section is connected to a modulation adjustment volume connected to the electronic volume via a switch, and the modulation adjustment is performed. The variable control oscillator is modulated within the standard by changing the voltage of the volume, and the optimum operating conditions of the electronic volume obtained at this time are stored in the memory section, and the electronic volume corresponding to the frequency used by the variable control oscillator is stored. A modulation degree correction circuit within a VCO band, characterized in that the optimum operating condition of the variable control oscillator is obtained from the memory section signal to operate the variable control oscillator.