JPH04175016A - Radio communication equipment - Google Patents

Abstract

PURPOSE:To set a transmission frequency quickly to a specified frequency, to avoid the effect of fading during communication and to keep the transmission frequency stable by setting a smaller 1st time constant at the start of transmission and setting a larger 2nd time constant for a communication period. CONSTITUTION:A control voltage from a D/A converter 41 during AFC operation is fed to a VCXO 42 via an LPF 62 with a small time constant. Thus, since the control voltage is fed to the VCXO 42 without a large delay, quick AFC operation is attained. When a reception channel frequency is tentatively changed due to the effect of fading during talking, a frequency comparator circuit 22 detects a frequency difference between a reception channel frequency and an oscillating frequency of the VCXO 42. A control voltage to correct the frequency difference to zero is outputted from a main body 21. Control voltage information is processed into an analog signal and a change component is obtained an LPF 61 having a large time constant and the result is fed to the VCXO 42. Thus, even when the reception channel frequency is tentatively changed due to fading, the transmission channel frequency receives no effect and is made stable.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to wireless communication devices such as car telephone devices, mobile phone devices, and cordless telephone devices, and particularly relates to radio communication devices such as car telephone devices, mobile phone devices, cordless telephone devices, etc. The present invention relates to a wireless communication device having means for detecting a received frequency and controlling a transmitting frequency based on the detected receiving frequency.

(Prior Art) In recent years, a system employing a digital system has been proposed as one type of wireless telephone system.

This type of system digitizes and transmits not only control signals but also communication content such as voice calls between base stations and mobile stations, ensuring confidentiality, improving compatibility with data, and transmitting radio frequency It becomes possible to make effective use of

By the way, in the wireless communication device used in the mobile station of this type of system, a method of controlling the transmitting channel frequency of the own device according to the receiving channel frequency from the base station is adopted as a wireless channel control method. . In this method, for example, a comparison circuit compares the frequency corresponding to the transmission channel frequency generated by a voltage controlled oscillator (VCO) with the frequency of the received intermediate frequency signal obtained by the receiving system, and detects the frequency difference. . Then, a control circuit generates a digital signal controlled to reduce this frequency difference, and converts this digital signal into a digital/analog (D/analog) signal.
A) After converting to analog control voltage with a converter, the above v
CO and is configured to variably control the transmission channel frequency. According to such a system, the transmission channel frequency can be controlled in accordance with the generally highly accurate reception channel frequency generated by the base station, so the transmission channel frequency can be stably set.

(Question 8 to be solved by the invention) However, in order to implement such a system, there were the following problems that needed to be improved. That is, in mobile radio systems, mobile stations often communicate while moving, and therefore the receiving channel frequency may change temporarily due to fading or the like. When the receiving channel frequency changes in this way, this change is immediately reflected in the transmitting channel frequency, causing the problem that the transmitting channel frequency deviates significantly from the specified frequency.

Therefore, in order to prevent this problem, it has been considered to provide a time constant to the transmission frequency control system so that even if the reception channel frequency changes temporarily, the transmission channel frequency does not immediately change in response to this change. There is. However, if you do this, for example, if you want to set the transmission channel frequency to the specified frequency as soon as possible immediately after transmission has started, the transmission channel frequency will gradually change due to the time constant mentioned above, so the wireless Another undesirable problem occurred in that channels could not be set quickly.

The present invention focuses on the above-mentioned circumstances, and makes it possible to prevent this change from being immediately reflected in the transmission frequency even if the reception frequency changes temporarily due to the influence of fading etc. during communication, and to quickly change the transmission frequency to the specified value at the start of transmission. This allows for both stability and responsiveness of the transmit frequency to be set to zero! lj! The purpose is to provide communication equipment.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention detects the reception frequency of each wireless channel and controls the transmission frequency based on the detected reception frequency. In a wireless communication device that
The transmission frequency control system has a time constant, and further includes a time constant control means. The time constant control means sets the time constant to a predetermined first time constant when setting a wireless channel, and sets it to a second time constant larger than the first time constant during other periods. It was designed to do so.

Further, the present invention provides the time constant control means by generating a control voltage that changes without a time constant from the control voltage generation means,
The control voltage is configured to be smoothed according to a predetermined time constant by a variable time constant circuit and supplied to the voltage controlled oscillator,
The time constant of the variable time constant circuit described above is set to the first time constant when setting a wireless channel, and is set to the second time constant during other periods.
It is characterized in that it is controlled so that the time constant is set to .

Furthermore, the present invention provides a time constant control means! The control voltage generating means generates a control voltage that changes according to a first time constant when setting a wireless channel, and generates a control voltage that changes according to a second time constant during other periods, and generates a control voltage that changes according to a second time constant to generate a voltage controlled oscillator. It is also characterized by being configured to supply.

(Function) As a result, according to the present invention, at the start of transmission, a small first time constant is set in the transmission frequency control system, so the transmission frequency is quickly set to the specified frequency. Therefore, the time required to set up a wireless channel is reduced,
The speaker can quickly start communication. Also, during the communication period, a large second time constant is set in the transmission frequency control system, so even if the reception frequency changes temporarily in this state, for example due to the influence of fading, the transmission frequency will not change due to this change. It remains stable without being significantly affected. Therefore, it is possible to perform stable communication without causing interference between adjacent channels with other wireless communication devices during communication.

(Embodiment) FIG. 2 shows the configuration of a mobile station device in an embodiment of the present invention.

In the same figure, a wireless communication signal sent from a base station (not shown) in a predetermined time slot is input to a receiving circuit (RX) 3 via an antenna 1 and a duplexer (DIP) 2, where it is input to a frequency synthesizer (SYN). ) 4 and is combined with the local oscillation signal output from 4 and converted into an intermediate frequency signal. This received intermediate frequency signal is then digitally demodulated by a digital code decoding circuit (MOD) 6 after establishing frame synchronization and bit synchronization. Note that the synchronization signal obtained by the frame synchronization and bit synchronization described above is supplied to the control circuit (CONT) 20. The digital demodulated signal output from the digital code decoding circuit 6 includes a digital speech signal and a digital control signal, of which the digital control signal is supplied to the control circuit 20 for identification. On the other hand, the digital speech signal is supplied to an equalizer (EQL) 7, where signal equalization of the demodulated waveform is performed, and then an error correction code decoding circuit (CH-CO
D) Error correction decoding is performed at 8. After being decoded by a speech code decoding circuit (SP-COD) 9 and returned to an analog call signal, the signal is supplied to a receiver 11 via an audio switch 10, and the receiver 11 outputs audio.

On the other hand, the transmission signal output from the transmitter 12 is input to the voice code/decoder circuit 9 via the voice switch 13 and encoded there. The digital transmission signal obtained by this encoding is subjected to error correction encoding together with the digital control signal outputted from the control circuit 20 in an error correction code decoding circuit 8, and then input to the digital code decoding circuit 6.

This digital code decoding circuit 6 generates an intermediate frequency modulation signal according to the digital transmission signal supplied from the error correction code decoding circuit 8, and transmits the modulated signal to the transmitting circuit (TX) 5.
is input. In the transmission circuit 5, the modulated signal is combined with the local oscillation signal output from the frequency synthesizer 4 and converted into a high frequency signal, and this high frequency signal is high frequency amplified and then transmitted from the antenna 1 to the base station via the duplexer 2. sent to.

Furthermore, the mobile station device of this embodiment has a configuration that can be applied to a system in which a digital system and a current analog system coexist, that is, a dual-mode LS-less telephone system. That is, when performing a wireless call using an analog system instead of a digital system, the audio switch 10.13 is switched from the audio code/decoding circuit 9 side to the analog audio processing circuit (A-AUD) 14 side under the control of the control circuit 20. .

The demodulated signal output from the receiving circuit 3 is converted into an audio signal by an analog audio processing circuit 14, and then supplied to a receiver 11 via an audio switch 10, from which audio is output. On the other hand, the transmission signal output from the transmitter 12 is input to the analog audio processing circuit 14 via the audio switch 13, where it is converted into an intermediate frequency signal, and then converted into a high frequency signal by the transmission circuit 5. and transmitted from antenna 1.

In addition, 15 is an input display section having switches such as a dial key and a call switch, and a display, and 16 is a power supply circuit.

FIG. 1 shows the configuration of a receiving circuit 3, a frequency synthesizer 4, and a transmitting circuit 5 of the mobile station device shown in FIG.

In the figure, when a received high frequency signal is input to a receiving circuit 3, it is first high frequency amplified by a high frequency amplifier 31, then converted to a first intermediate frequency signal by a first mixer circuit 32, and then converted to a first intermediate frequency signal by a second mixer circuit 33. 2 intermediate frequency signals. This second intermediate frequency signal is then supplied to the digital code decoding circuit 6, as well as the frequency comparison circuit 22 in the control circuit 20 and the discriminator 18 in the analog audio processing circuit 14.

On the other hand, when the digital transmission signal output from the digital code decoding circuit 6 is input to the transmission circuit 5, it is first
The mixer circuit 51 combines the transmitted local oscillation signal output from the frequency synthesizer 4 and converts it into a first intermediate frequency signal, which is then converted into a transmitted high frequency signal by the second mixer circuit 53 via the buffer amplifier 52. Ru. This transmission high frequency signal is then amplified by a power amplifier (PA) 54 and then transmitted.

Incidentally, the frequency synthesizer 4 and the control circuit 20 have an automatic frequency control (AFC) function for controlling the transmission frequency according to the reception frequency from the base station.

That is, the second intermediate frequency signal output from the receiving circuit 3 is input to the frequency comparison circuit 22. The frequency comparison circuit 22 also receives a frequency generated from a voltage controlled crystal oscillator (VCXO) 4'2 in the frequency synthesizer 4. The frequency comparator 22 compares the frequency of the second intermediate frequency signal and the frequency of the fS signal generated from the VCXO 42 after performing predetermined signal processing, and sends a signal representing the frequency difference to the control circuit 20. It is supplied to the control circuit main body (CONT) 21 inside. Control circuit main body 21
outputs a digital value of the control voltage corrected to make the frequency difference zero. This digital value is the D/A
After being converted into an analog value by a converter 41, it is converted to an analog value by a voltage controlled crystal oscillator circuit (VCXO) 4 via a time constant circuit, which will be described later.
2. Then, this VCXO 42 generates a frequency corresponding to the above analog value, and this frequency is used as a reference frequency in the receiving PLL circuit (RXPLL) 4.
3. Multiplier circuit (XN) 44, Modulation PLL circuit (MODP
LL) 45 and a transmission PLL circuit (TXPLL) 46, respectively. As a result, a first local oscillation frequency and a second local oscillation frequency are generated from the reception PLL circuit 43 axis and the multiplier circuit 44, respectively, and these local oscillation frequencies are transmitted to the first local oscillation frequency of the reception circuit 3 via buffer amplifiers 47 and 48, respectively. 1 mixer circuit 32 and 2nd mixer circuit 3
3.

In addition, a variable 11 PLL circuit 45 and a transmission PLL circuit 46
A transmit intermediate frequency and a transmit local oscillation frequency are respectively generated from buffer amplifiers 49 .
The signal is supplied to the first mixer circuit 51 and the second mixer circuit 53 of the transmitting circuit 5 via 40 . Therefore, the transmitting circuit 5 generates a transmitting frequency corresponding to the receiving frequency in the receiving circuit 3.

Now, the D/A converter 41 in the frequency synthesizer 4 and the V
A time constant circuit is inserted between the CXO 42 and the CXO 42.

This time constant circuit includes a first low-pass filter (LPFl
) 61, a second low-pass filter (LPF2) 62, and a changeover switch 63. The first low-pass filter 61 has a relatively large first time constant necessary to absorb temporary changes in the receiving channel frequency due to fading or the like. On the other hand, the second low-pass filter 62 has a small second time constant necessary for setting the transmission f:channel frequency to a specified value at a high speed when setting a wireless channel. One side changeover switch 6
3 is a switching control signal S output from the control circuit main body 21
The low-pass filter 62 selects either the first low-pass filter 61 or the low-pass filter 62 of 7B2 according to the level of the switching control signal SS.

The control circuit main body 21 is composed of, for example, a microcomputer, and includes time constant control means in addition to normal control means such as wireless channel setting control means. This time constant control means generates a switching control signal SS for selectively selecting the first and second low-pass filters 61, 62 depending on the operating state of the device.

Next, the operation of the apparatus configured as described above will be explained according to the control procedure of the control circuit main body 21.

In the standby state, for example, suppose that the user presses the call switch in the input display section 15 to make a call.

Then, as shown in FIG. 3, the control circuit main body 21 first outputs a switching control signal SS for selecting the second low-pass filter 62 in step 3a. Therefore, the selector switch 63 is switched to the second low-pass filter 62 side, and thereby the second low-pass filter 62 is inserted into the radio channel frequency control system. In other words, the small second time constant by the second low-pass filter 62 is inserted as a loop time constant in the radio channel control system.

In this state, the control circuit main body 21 outputs control voltage information for setting a wireless channel for communication to the frequency synthesizer 4 in step 3b. Then, the control voltage information, that is, the digital value of the control voltage is transferred to the D/A converter 41.
After being converted into an analog value, the signal is supplied to the VCXO 42 via the second low-pass filter 62. For this reason,
Each PLL circuit of the frequency synthesizer 4 starts an operation for generating a local oscillation frequency according to the control voltage. Also, at this time, the frequency comparison circuit 22
The frequency generated from the XO 42 and the received intermediate frequency are compared, and the frequency difference is detected. Then, in the control circuit main body 21, correction is performed on the control voltage information in order to make the frequency difference zero, and this corrected control voltage is supplied to the frequency synthesizer 4. That is, the control circuit and frequency synthesizer perform AFC operation on the radio channel frequency.

By the way, during the AFC operation, the control voltage output from the D/A converter 41 is supplied to the VCXO 42 via the second low-pass filter 62 as described above. However, since the time constant of the second low-pass filter 62 is set to a small value as described above, the D/A converter 41
The control voltage outputted from the VCXO 42 is supplied to the VCXO 42 without causing a large delay, as shown in FIG. 4(a), for example. Therefore, quick AFC operation is possible.

Meanwhile, during the AFC operation, the control circuit main body 21 determines in step 3d whether the transmission channel frequency has converged within ±50 II z. Then, when it is detected that it has converged within ±5011 z, the switching control signal S for selecting the first low-pass filter 61 is sent in step 3e.
Output S. Therefore, the changeover switch 63 switches from the second low-pass filter 62 side to the first low-pass filter 61 side.
As a result, the first low-pass filter 61 is inserted into the radio channel frequency control system. That is, from now on, a large time constant will be inserted into the radio channel frequency control system.

When the switching of the low-pass filter is completed, the control circuit main body 21 next determines whether synchronization has been established for the received data in step 3f, and when synchronization is established, performs short burst burst in step 3g. Send. The shortened burst is used to measure the propagation delay between the base station and the base station, and consists of a pattern that is a combination of several types of frame patterns and a "0° bit pattern."

The base station measures the propagation delay time from the reception result of the shortened burst, inserts time alignment information into the response signal, and sends it back. When the control circuit body 21 of the mobile station device detects in step 3h that the response signal has been returned from the base station, it sets the transmission timing of the transmission time slot in accordance with the time alignment information in step 31. Then, in step 3j, speech data is transmitted using this transmission time slot, and thereafter the communication control state is established.

By the way, suppose that during this call, the receiving channel frequency changes temporarily due to the influence of fading, for example. Then, the frequency comparison circuit 22 detects the frequency difference between the reception channel frequency and the oscillation frequency of the VCXO 42, and the control circuit main body 21 outputs control voltage information for correcting this frequency difference to zero. In other words, control voltage information that includes the change in the reception channel frequency as is is output. However, after the control voltage information is converted into an analog value by the D/A converter 41, it is supplied to the VCXO 42 through the first low-pass filter 61. Here, a large time constant is set for the first low-pass filter 61. For this reason, the control voltage is supplied to the VCXO 42 by passing through the first low-pass filter 61, with the variation substantially absorbed, for example, as shown in FIG. 4(b). Therefore, even if the reception channel frequency changes temporarily due to fading,
This eliminates the problem of the transmission channel frequency changing instantly and greatly, thereby keeping the transmission channel frequency stable.

In this embodiment, the first low-pass filter 61 having a large time constant and the second low-pass filter 62 having a small time constant are prepared, and these low-pass filters 61 Since .62 is selectively inserted into the radio channel frequency control system using the changeover switch 63, high-speed AFC operation is possible when setting the radio channel. can be done. In other words, it is possible to set a wireless channel with high responsiveness. Additionally, even if the reception channel frequency changes temporarily during a call due to effects such as fading, this change will no longer be immediately reflected in the transmission channel frequency, making it possible to maintain a stable wireless channel frequency. .

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, the D/A converter 41 and the VCXO 42
By selectively inserting low-pass filters 61, 62 between the You may also have Figure 5 shows the D/A in this case.
An example of the output voltage waveform of the converter 41 is shown. Further, the D/A converter and the VCXO may have a time constant.

Furthermore, in the above embodiment, two types of time constants are prepared and these time constants are used by switching, but three or more types of time constants are prepared and these can be changed depending on the type and content of the operation of the device. The optimum time constant may be selected and used from among the time constants.

In addition, the configuration of the time constant control means, control procedure, switching timing, configuration of the wireless communication device, etc. may be modified in various ways without departing from the gist of the present invention.

[Effects of the Invention] As described in detail above, according to the present invention, the transmission frequency control system has a time constant, and the time constant is controlled by the time constant control means to a predetermined first value when setting a wireless channel. By setting the time constant to , and setting the second time constant larger than the first time constant for other periods,
Even if the reception frequency changes temporarily due to fading or other factors during communication, this change can be prevented from being immediately reflected in the transmission frequency, and the transmission frequency can be quickly set to the specified value when transmission starts. This makes it possible to provide a wireless communication device that has both transmission frequency stability and responsiveness.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing the main configuration of a wireless communication device according to an embodiment of the present invention, FIG. 2 is a circuit block diagram showing the overall configuration of the same device, and FIG. 3 is the same as shown in FIG. 1. A flowchart showing the control procedure and control contents of the control circuit main body of the device, FIG. 4 is a signal waveform diagram used to explain the operation of the device shown in FIG. 1, and FIG. 5 explains another embodiment of the present invention. FIG. 3 is a signal waveform diagram for 1... Antenna, 2... Dual unit (DIU), 3
... Receiving circuit (RX), 4... Frequency synthesizer (SYN), 5... Transmitting circuit (TX), 6...
Digital code decoding circuit (MOD), 7... Equalizer (EQL), 8... Error correction code decoding circuit (CH-
COD), 9...Speech code decoding circuit (SP-COD)
), 10.13... Audio switch, 11... Receiver, 12... Transmitter, 14... Analog signal processing circuit (A-AUD), 15... Input operation unit, 16...・
Power supply circuit, 18... Discriminator, 20...
Control circuit, 21... Control circuit main body, 22... Frequency comparison circuit, 31... High frequency amplifier, 32.51...
1st mixer circuit, 33.53... 2nd mixer circuit, 4
1... Digital-to-analog converter, 42... Voltage control original oscillator (VCXO), 43... Receiving PLL
Circuit (RXPLL), 44... Multiplier circuit, 45...
・Modulation PLL circuit (MODPLL), 46... Transmission PLLL circuit (TXPLL), 40.47°48.4
9.52... Buffer amplifier, 54... Power amplifier (PA), 61... First low pass filter (LP
FI), 62... second low-pass filter (LPF
2) , 63... Changeover switch, SS... Changeover control signal. Applicant's representative Patent attorney Takehiko Suzue J-62゜Figure 3Figure 4 0V
---=-Figure 5

Claims (3)

[Claims] (1) In a wireless communication device that detects the reception frequency of each wireless channel and controls the transmission frequency based on the detected reception frequency, the transmission frequency control system has a time constant, and The present invention further includes a time constant control means that sets the constant to a predetermined first time constant when setting the wireless channel, and sets the constant to a second time constant that is larger than the first time constant during other periods. Characteristic wireless communication device. (2) The time constant control means includes a control voltage generation means that generates a control voltage that changes without a time constant, and a control voltage generation means that smoothes the control voltage generated from the control voltage generation means according to a set time constant. A variable time constant circuit for supplying a voltage controlled oscillator, and a circuit for setting a first time constant when setting a wireless channel to the variable time constant circuit, and a second time constant for other periods. 2. The wireless communication device according to claim 1, further comprising variable time constant setting means. (3) The time constant control means generates a control voltage that changes according to a first time constant when setting a wireless channel, and generates a control voltage that changes according to a second time constant during other periods, and generates a control voltage that changes according to a second time constant. The wireless communication device according to claim 1, further comprising control voltage generation means for supplying a control oscillator.