JP4334421B2 - Filter shared decoder and wireless communication device incorporating the same - Google Patents

Description

  The present invention relates to a decoder for a wireless communication apparatus having a voice transmission / reception function and a minimum shift keying modem (MSK modem) for transmitting and receiving voice and data, and more particularly, to co-channel rejection. The present invention relates to an MSK decoder that improves the rejection ratio indicating the characteristics of the above and a wireless communication device incorporating the same.

  FIG. 2 is a hardware block diagram showing the configuration of a conventional wireless communication device. The audio signal input from the microphone 1 is amplified by the microphone amplifier 2. Further, this audio signal is enhanced by +6 dB / oct in the high frequency range of the audio signal in order to improve S / N in the pre-emphasis circuit 4. The audio signal with the high frequency emphasized is input to the splatter filter 6 by the first switch 5 and passes through a 3 kHz low-pass filter to prevent leakage to an adjacent channel. The audio signal that has passed through the splatter filter 6 is frequency-modulated by the modulator 7, amplified by high-frequency power by the transmission circuit 8, and connected to the antenna 10 by the second switch 9, and is connected to the partner radio communication device or base station. Sent to.

  The transmitted audio signal passes through the antenna 10 and the second switch 9 of the counterpart wireless communication device and is amplified by the receiving circuit 11. The amplified signal is demodulated into an audio signal by the demodulator 12. Thereafter, the demodulated audio signal is returned to the original audio signal at −6 dB / oct by the de-emphasis circuit 13 and is amplified by the audio power amplifier 15 to drive the speaker. The power-amplified audio signal drives the speaker and conveys information to the receiver.

  By the way, as an application of the MSK modem, as a data transmission, an ID is transmitted at the start / end of transmission and an individual call is performed, and coordinate data from a GPS connected to a radio is notified to a communication destination, and linked to a trunking system. In some cases, the terminal ID is transmitted and data for handshaking is transmitted and received. Here, a case where an ID is transmitted at the start / end of transmission and an individual call is performed will be described as an example. An ID input at the start / end of transmission is encoded by the MSK encoder 3, converted into an MSK data signal of 1200 bps or 2400 bps, and connected to the splatter filter 6 by the first switch 5. Thereafter, the encoded ID is transmitted from the antenna 10 as an MSK data signal, as in the case of the voice input signal.

The transmitted MSK data signal passes through the same process as that of the transmitted audio signal from the antenna 10 to the demodulator 12 of the counterpart wireless communication device, and is demodulated into the MSK data signal by the demodulator 12. The demodulated MSK data signal is input to the MSK decoder 14 and restored to the original ID. As an application example of such an MSK signal, in a call control device of a wireless communication device that can be called by individual call information, group call information, and first simultaneous call information, a second simultaneous call described in Patent Document 1 is provided. There is known a control device that switches a wireless device in communication to a second simultaneous call when there is a call.
JP 2000-315979 A

  In order to transmit and receive voice and data, wireless communication devices equipped with a voice transmission / reception function and an MSK modem have become widespread, and their use has also expanded in Europe. However, in Europe, the European Standard (ETSI EN300 113-1) shows a cochannel rejection ratio as a European standard. According to this, the rejection ratio is defined as 0 dB to −8.0 dB at a channel separation of 20 kHz or 25 kHz, and 0 dB to −12 dB at 12.5 kHz.

  However, although the conventional wireless communication device described with reference to FIG. 1 clears this standard value, from the viewpoint of device design, the operation margin is not sufficient depending on the condition of channel separation. Therefore, there has been a demand for a method for improving the operation margin without causing a significant design change and without adding expensive parts.

  The present invention has been made to solve such a problem, and the object of the present invention is to prevent a significant change in design and to add a co-channel rejection ratio without adding expensive parts. The MSK decoder that improves the operational margin and the wireless communication incorporating the same are provided.

The filter shared decoder according to the present invention includes a pre-emphasis circuit that emphasizes a high frequency in order to improve S / N of a transmitted audio signal in a wireless communication device for transmitting and receiving audio and data, and a received signal. A demodulator that demodulates an audio signal or a received MSK data signal, an MSK encoder that encodes an ID input at the start and end of transmission, a first output that selects an output of the pre-emphasis circuit and an output of the demodulator Switching means, and second switching means for selecting the output of the first switching means and the output of the MSK encoder, and the output of the second switching means leaks a transmission signal to an adjacent channel Is connected to the input of a splatter filter, and the output of the splatter filter includes a modulator for modulating the transmission signal and a high frequency band. Wherein the de-emphasis circuit to return the output of the tone has been demodulator in the original audio signal, the MSK decoder for restoring the received MSK data signal to the original data, to be connected to.

The shared filter type decoder is configured such that the received MSK data signal demodulated by the demodulator of the wireless communication device is input to the splatter filter by the first switching unit and the second switching unit, and the splatter filter The received MSK data signal output from is input to the MSK decoder.

In the filter shared decoder, the first switching means and the second switching means are switched in conjunction with a PTT (Push To Talk) switch of the wireless communication device, and the MSK data signal is input to the splatter filter. It is characterized by that.

  The wireless communication apparatus of the present invention is characterized by incorporating the filter shared decoder.

  According to the shared filter type decoder of the present invention, an MSK decoder that improves the co-channel rejection ratio and improves the operation margin without causing a significant design change and without adding expensive parts. Wireless communication incorporating this can be provided.

  An embodiment of a shared filter decoder according to the present invention will be described with reference to FIG. FIG. 1 is a hardware block diagram showing a device configuration of a wireless communication device in which a filter sharing type decoder of the present invention is mounted. The same names and numbers are assigned to the same blocks as the operations described in FIG.

  The audio signal input from the microphone 1 is amplified by the microphone amplifier 2. Further, this audio signal is enhanced by +6 dB / oct in the high frequency range of the audio signal in order to improve S / N in the pre-emphasis circuit 4. The audio signal in which the high frequency is emphasized is input to the splatter filter 6 by the third switch 17 and the first switch 5 and passes through a 3 kHz low-pass filter in order to prevent leakage to an adjacent channel. The operations of the third switch 17 and the first switch 5 operate in conjunction with a PTT (Push To Talk) switch of the wireless communication device. When the PTT switch is pressed during transmission, the third switch 17 and the first switch 5 operate. The switch 5 has a circuit configuration for connecting the MSK encoder 3 and the splatter filter 6. The audio signal that has passed through the splatter filter 6 is frequency-modulated by the modulator 7, amplified by high-frequency power by the transmission circuit 8, and connected to the antenna 10 by the second switch 9, and is connected to the partner radio communication device or base station. Sent to.

  The transmitted audio signal passes through the antenna 10 and the second switch 9 of the counterpart wireless communication device and is amplified by the receiving circuit 11. The amplified signal is demodulated into an audio signal by the demodulator 12. After that, the demodulated audio signal is connected to the demodulator 12 and the splatter filter 6 by the third switch 17 and the first switch 5 interlocked with the PTT switch, so that the connection circuit is switched and input to the splatter filter 6. The The audio signal from which the interference wave noise has been removed by the splatter filter 6 is returned to the original audio signal at −6 dB / oct in the de-emphasis circuit 13, and the audio power amplifier 15 drives the speaker. Power amplification. The power-amplified audio signal drives the speaker and conveys information to the receiver.

  As in the case of FIG. 1, data transmission using an MSK data signal will be described by taking as an example a case where an ID (call number) is transmitted and individual calls are made at the start / end of transmission. The ID input at the start / end of transmission is encoded by the MSK encoder 3 and converted into an MSK data signal of 1200 bps or 2400 bps. Connected to the filter 6. Thereafter, the encoded ID is transmitted from the antenna 10 as an MSK data signal, as in the case of the voice input signal.

  The transmitted MSK data signal passes through the same process as that of the transmitted audio signal from the antenna 10 to the demodulator 12 of the counterpart wireless communication device, and is demodulated into the MSK data signal by the demodulator 12. The demodulated MSK data signal is input to the splatter filter 6 because the demodulator 12 and the splatter filter 6 are connected by the third switch 17 and the first switch 5 interlocked with the PTT switch. Is done. The MSK data signal from which the interference wave noise has been removed by the splatter filter 6 is input to the MSK decoder 14 and restored to the calling number which is the original data. This call number is checked whether it is the number of the own station on the receiving side, and if it is determined that it is the number of the own station, an operation during an individual call is performed (not shown).

  FIG. 3 is a frequency vs. gain characteristic diagram showing the overall reception characteristics of a wireless communication device equipped with a filter sharing type decoder according to the present invention. By cutting the interference wave component outside the frequency band from 300 Hz to 3 kHz, the overall performance of reception performance such as reception sensitivity and distortion is improved, and the overall performance of MSK decoding is improved. The conventional wireless communication device shown in FIG. An average improvement of 2 dB was achieved for the co-channel rejection ratio. This effect also leads to improvement of S / N in voice reception.

  As described above, according to the present invention, the MSK that does not cause a significant design change, improves the cochannel rejection ratio without adding expensive parts, and improves the operation margin. Decoder can be provided. Further, the first switch 5 in FIG. 1 may be always connected in a circuit without switching the connection in conjunction with the PTT switch due to the difference in the processing method of the audio signal and the data signal and the difference in the transmission timing. .

FIG. 3 is a hardware block diagram of a device configuration of a wireless communication device in which a filter shared decoder according to the present invention is mounted. The apparatus structure of the conventional radio | wireless communication apparatus is shown. The frequency versus gain figure which shows the reception comprehensive characteristic of the radio | wireless communication apparatus which mounted the filter sharing type decoder of this invention.

Explanation of symbols

1 microphone
2 Microphone amplifier
3 MSK encoder
4 Pre-emphasis circuit
5 Second switch (S1)
6 Splatter filter
7 Modulator
8 Transmitter circuit
9 Second switch (S2)
DESCRIPTION OF SYMBOLS 10 Antenna 11 Reception circuit 12 Demodulation circuit 13 De-emphasis circuit 14 MSK decoder 15 Audio | voice power amplifier 16 Speaker 17 3rd switch (S3)

Claims (4)

In a wireless communication device for sending and receiving voice and data,
Pre-emphasis circuit that emphasizes high frequency to improve S / N of transmitted audio signal, demodulator that demodulates received signal into audio signal or received MSK data signal, and input at start / end of transmission An MSK encoder that encodes the ID;
First switching means for selecting an output of the pre-emphasis circuit and an output of the demodulator; a second switching means for selecting an output of the first switching means and an output of the MSK encoder;
With
The output of the second switching means is connected to the input of a splatter filter that prevents the transmission signal from leaking to the adjacent channel;
The output of the splatter filter is a modulator that modulates the transmission signal, a de-emphasis circuit that returns the output of the demodulator with high frequency emphasis back to the original audio signal, and the received MSK data signal is restored to the original data. A filter shared decoder connected to an MSK decoder . 2. The shared filter type decoder according to claim 1, wherein the received MSK data signal demodulated by the demodulator of the wireless communication device is input to the splatter filter by the first switching unit and the second switching unit. The filter-shared decoder, wherein the received MSK data signal output from the splatter filter is input to the MSK decoder. 3. The filter sharing type decoder according to claim 2, wherein the first switching means and the second switching means are switched in conjunction with a PTT (Push To Talk) switch of the wireless communication device, and the MSK data signal is Filter shared decoder characterized by being input to splatter filter.   A wireless communication device comprising the filter shared decoder according to any one of claims 1 to 3.

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