JPH01109908A - Frequency shift compensation circuit - Google Patents

Abstract

PURPOSE:To control the frequency deviation within the deviation standard over a wide range of frequencies by having only to set a maximum frequency deviation variable resistor at once only through the attenuation of a prescribed amount of an audio signal corresponding to the selected channel. CONSTITUTION:When the operating frequency channel is selected by a channel select section 5, a setting section 6 sets the frequency of a carrier to generate the carrier from a carrier generating section 4. Simultaneously, the setting section 6 sets variably the attenuation of an audio signal corresponding to the carrier frequency and an attenuation section 7 attenuates the signal by a prescribed quantity. ln setting the level by the attenuation section 7 so as to decrease a low frequency output level with respect to, e.g., the carrier frequency, the frequency deviation f is nearly constant in any channel and the maximum frequency deviation of one channel is preset within the standard of the maximum frequency to eliminate the need for the succeeding adjustment.

Description

[Detailed Description of the Invention] Overview] When a carrier wave is frequency-modulated and transmitted using an audio signal that has been attenuated by a predetermined m, by variably attenuating the audio signal according to the carrier wave frequency, the frequency can be modulated over a wide range of frequencies. The deviation can be kept within the maximum frequency deviation specification.

[Industrial application field]

The present invention relates to radio equipment, particularly frequency modulation (FM)
The present invention relates to a frequency shift compensation circuit that compensates for frequency shift of a carrier wave in a transmitter.

[Conventional technology]

In conventional radio equipment, especially FM transmitters using frequency modulation (FM), P L L (Phase Locked L
A method is widely used in which a frequency synthesizer (OOP) is used to generate channel frequencies in which frequencies in the operating range (ie, transmission frequencies) are divided at regular intervals, for example, at intervals of 10 to 25 KHz.

FIG. 6 is a block diagram showing the configuration of a conventional radio device,
In particular, the transmitter is shown. In this figure, the transmitter includes an audio signal generator 1. Modulation section 2. Transmitter 3
．． It is composed of a carrier wave generator 5 and a channel selector 5. In this transmitter, when one channel is selected from a plurality of channels by the channel selector 5, a carrier wave having a frequency corresponding to this channel is generated by the carrier wave generator 4. The modulator 2 frequency-modulates this carrier wave using the audio signal from the audio signal generator 1 and sends it to the transmitter 3. The transmitter 3 amplifies the power of the frequency-modulated carrier wave and transmits it from the antenna 8.

To explain in more detail, the audio signal generating section 1 includes:
Microphone 11. Standard modulation frequency deviation setting volume 12. Amplifier 13. Limiter 14. It consists of a maximum frequency shift setting volume and a low pass filter 16.

The carrier wave generator 4 includes a PLL synthesizer 41 and a voltage controlled oscillator (VCO) 21. Further, this voltage controlled oscillator 21 constitutes the modulation section 2. With these configurations, first, voice is converted into an audio signal by the microphone 11, and the signal is sent to the amplifier 13 via the standard modulation frequency shift setting volume I2 for amplification. This standard modulation frequency deviation setting volume 12 is used to adjust variations in components such as the sensitivity of the microphone 11.

The audio signal amplified by the amplifier 13 is sent to the limiter 1
4, the voltage amplitude of the audio signal is trimmed to a constant level, and outputted to a low-pass filter 16 via a maximum frequency shift setting volume 15.

The maximum frequency deviation setting polychrome 15 is for adjusting the level of the audio signal so that the frequency deviation, that is, the audio signal falls within a predetermined maximum frequency deviation standard. The low-pass filter 16 filters the audio signal set by the maximum frequency shift setting volume 15 and outputs it to the VCO 21 . This VCO21 is PLL
The carrier wave frequency changes according to the output from the synthesizer 41, and the frequency is modulated by the audio signal from the low-pass filter 16, and the signal is transmitted from the antenna 8 via the transmitter 3. This PLL synthesizer 41 has a frequency divider that divides the reference frequency to form a predetermined frequency, and sets the carrier wave frequency selected by the channel selector section 5.

[Problem that the invention seeks to solve]

FIG. 7 is a diagram showing frequency shift characteristics when the modulation input level is constant. In this figure, when used in adjacent channels B and C, the frequency deviation is within the maximum frequency deviation standard, so there is no interference with the adjacent channels. In addition, when using channels A and C, the frequency deviation exceeds the maximum frequency deviation standard Δf max, but the frequency deviation can be adjusted by adjusting the maximum frequency deviation setting volume 15 (curve ■ in Fig. 7). The shift can be kept within the maximum frequency shift specification 8fIIIax. However, when using channels A and C, there is a wide separation between them, so the frequency deviation in channel C does not exceed the maximum frequency deviation specification Δf wax,
The frequency deviation in channel A is the maximum frequency deviation specification Δf
l1ax is exceeded, causing problems such as interference with channels near channel A, or the modulation becomes too deep, making it difficult to hear on the receiver side. Also, adjust the maximum frequency deviation setting volume 15 to
When one frequency deviation is kept within the maximum frequency deviation standard Δf max (from curve ■ to curve ■), the frequency deviation of channel C becomes smaller and the modulation becomes shallower, so the receiver side still cannot hear it. The problem arises that it becomes difficult. These problems occur because the maximum frequency shift setting volume 15 is adjusted and the frequency shift is set depending on the channel to be used.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a frequency deviation method that compensates for frequency deviations so that even between widely separated channels, the frequency deviations fall within the maximum frequency deviation standard. The purpose of this invention is to provide a shift compensation circuit.

[Means for solving problems]

FIG. 1 is a block diagram showing the principle structure of a frequency shift compensation circuit based on the present invention. In the figure, reference numeral 1 denotes an audio signal generating section, which converts audio into an electrical signal and generates an audio signal. 2 is a modulation section, and a carrier wave generation section 4
modulates the carrier wave output from the audio signal. A transmitter 3 amplifies the power of the modulated carrier wave and transmits it from the antenna 8. Reference numeral 5 denotes a channel selector section, which selects the frequency of the carrier wave output from the carrier wave generating section 4. The configuration up to this point is the same as that of a conventional transmitter. Reference numeral 7 denotes an attenuation section, which sets the frequency of the carrier wave from the carrier wave generation section 4 according to the audio output signal, and sets the amount of attenuation of the audio signal in the attenuation section 7 in accordance with this frequency. These setting section 6 and damping section 7
form the frequency shift compensation circuit 10.

[For production]

With the above configuration, in the channel selection section 5,
When the channel of the frequency to be used is selected, the setting section 6 sets the frequency of the carrier wave from the selected channel, and causes the carrier wave generating section 4 to generate a carrier wave of the set frequency. At the same time, the setting section 6 variably sets the amount of attenuation of the audio signal in accordance with the set carrier frequency, and the attenuation section 7 attenuates the audio signal by a predetermined amount. Thus, for example, if the output level from the attenuator 7 is set with respect to the carrier frequency as shown in FIG. 2, the frequency shift characteristic at this time will be as shown in FIG. 3. From FIG. 3, it can be seen that the frequency deviation is approximately constant in all channels, and by setting the maximum frequency deviation of one channel within the maximum frequency deviation standard in advance, subsequent adjustment is unnecessary.

〔Example〕

FIG. 4 is a block diagram showing an embodiment of the present invention, and shows a radio device. In this figure, the audio signal generating section 1 includes a microphone 11 . Reference modulation frequency deviation setting volume 12.
Amplifier 13. Limiter 14. It is composed of a maximum frequency deviation setting volume 15 and a low-pass filter 16, and converts the audio signal into an electrical signal to the modulation unit 2.
Send to. The modulation section 2 consists of a VCO 21 that also constitutes the carrier wave generation section 4, and uses the audio signal to generate CO2
1 carrier wave frequency is modulated. This modulated carrier wave frequency is amplified by the power amplifier of the transmitter 3 and transmitted from the antenna 8. The carrier wave generating section 4 mentioned above is PL
It consists of an L synthesizer 41 and a VCO 21, and generates a carrier wave of a frequency determined by the channel selection section 5, for example, key selection on a keyboard. The configuration up to this point is the same as that of a conventional transmitter. The setting section 6 includes, for example, a microcomputer 61, and causes the carrier wave generation section 4 to generate a carrier wave of a predetermined frequency by selecting a key on the keyboard of the channel selector section 5, and also sets the attenuation amount of the attenuation section 7 corresponding to this predetermined frequency. Set. This microcomputer 61 is a CPU.

Consists of ROM, RAM, and Ilo. The attenuation section 7 includes a variable attenuator 71, and attenuates the audio signal according to an attenuation amount set by the microcomputer 61.

With the above configuration, when a key is selected on the keyboard of the channel selector section 5 and a selection key signal is generated, this selection key signal is sent to the CPU via Ilo of the microcomputer 61. In response to the selection key signal, the CPU reads the frequency division J'', etc. corresponding to the frequency of the channel selected by the selection key from among the frequency division number group for frequency setting stored in advance in the ROM, and reads Ilo
and send it to the PLL synthesizer 41 via
The attenuation amount corresponding to that channel is also read from the ROM and sent to the variable attenuator 71 via Ilo.

As a result, the PLL synthesizer 41 divides the carrier wave frequency by this frequency division ratio, and the VCO 21 generates a carrier wave of the key-selected frequency. On the other hand, as mentioned above, the voice is converted into an audio signal through the microphone 11, and the standard modulation frequency deviation setting volume 12. Amplifier 13° Limiter 14. The signal is output via the maximum frequency shift setting volume 15 and the low-pass filter 16 to the variable attenuator 71 as an audio signal that modulates a carrier wave. The variable attenuator 71 attenuates the audio signal according to the attenuation amount set by the microcomputer 61.
Output to VCO21. As a result, the VCO 21 modulates the attenuated audio signal according to the key-selected frequency, the transmitter 3 amplifies the power, and transmits the signal from the antenna 8 .

As shown in the functional block diagram of FIG. 4B, the microcomputer 61 determines whether the channel of the channel selector section 5 has been changed by the selection key signal reading means 6a that reads the selection key signal and the selection key signal reading means. Channel change determination means 6b, attenuation amount setting means 6c for setting the attenuation amount of the attenuation section 7 by the channel change determination means 6b, and carrier wave frequency setting means 6d for setting the carrier frequency by the channel change determination means 6b.
It has various functions. Below, microcomputer 61
The processing operation will be explained with reference to the flowchart in FIG.

First, in step 101, a selection key signal from the channel selector section 5 is read, and the process proceeds to step 102. In step 102, it is determined whether the channel has been changed. If the channel has not been changed, the process returns to step 101. If the channel has been changed, the process proceeds to step 103, where the frequency fx selected by the selection key previously stored in the ROM is read, and the process proceeds to step 104. In step 104, the set value N is calculated using the following formula, and the process proceeds to step 105.

N= (r, -re)/c Here, C is the frequency of the channel spacing, fo is the base frequency, and the minimum channel frequency among all channel frequencies is, for example, N-1 in the above equation,
This is the minimum channel frequency minus the channel spacing frequency.

In step 105, the attenuator amount corresponding to the set value N is stored in advance in the ROM (for example, the set value N
=1.2. ..., attenuator IAz3 corresponding to n
．． l aj + . In step 106, the frequency division ratio corresponding to the selected key is sent to the PLL synthesizer 41, and the process returns to step 101.

〔Effect of the invention〕

As explained above, according to the present invention, by attenuating the audio signal by a predetermined amount corresponding to the selected channel, it is possible to attenuate the audio signal by a predetermined amount in accordance with the selected channel, so that it can be applied over a wide range of frequencies by simply setting the maximum frequency deviation volume by - degrees. The frequency deviation can be kept within the maximum frequency deviation specification without interference between channels.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the principle configuration of a frequency shift compensation circuit based on the present invention, and FIG. 2 is a diagram showing carrier frequency f versus output level A from attenuator 7.
6 g 1. FIG. 3 is a relationship diagram of carrier frequency f vs. frequency deviation Δ, FIG. 4A is a block diagram showing an embodiment of the present invention, and FIG. 4B
The figure is a functional block diagram of the microcomputer 61, Figure 5 is a flowchart diagram showing the processing operation of the microcomputer 61, Figure 6 is a block diagram showing the configuration of a conventional radio, and Figure 7 is a conventional carrier wave frequency versus frequency. It is a relationship diagram of deviation Δf-. DESCRIPTION OF SYMBOLS 1... Audio signal generation part, 2... Modulation part, 3.
...Transmission section, 4...Carrier wave generation section, 5...
・Channel selection section, 6... Setting section, 7... Attenuation section, 8...
antenna, 10... frequency shift compensation circuit;

Claims (1)

[Claims] 1. The carrier wave of the frequency selected by the channel selector (5) is transmitted to the audio signal generator (1).
in a frequency shift compensation circuit that is located in a transmitter that modulates and transmits an audio signal from an audio signal, and that attenuates the audio signal so that the frequency shift of the modulated carrier wave falls within a maximum frequency shift standard; an attenuation section (7) that variably attenuates the attenuation section (7); and a variable attenuation amount in the attenuation section (7) is set in accordance with the frequency of the carrier wave set by the channel selection from the channel selection section (5). A frequency shift compensation circuit comprising a setting section (6). 2. The frequency shift compensation circuit according to claim 1, wherein the attenuation section (7) comprises a variable attenuator (71). 3. The setting section (6) includes a selection key signal reading means (6a) for reading a selection key signal, and a selection key signal reading means (6a) that reads the selection key signal into the channel selector section (5).
channel change determination means (6b) for determining whether the channel of
b) attenuation amount setting means (6c) for setting the attenuation amount of the attenuation section (7) by a selection key signal; and carrier wave frequency setting means (6c) for setting the carrier wave frequency from the selection key.
6d). The frequency shift compensation circuit according to claim 1, comprising: 4. The setting section (6) includes a microcomputer (61
) The frequency shift compensation circuit according to claim 3.