JP2023081171A - Direct conversion type radio receiver and control method thereof - Google Patents

Abstract

To stably receive a signal by a direct conversion type radio receiver.SOLUTION: A radio receiver (10) includes a local oscillator (4) for generating a local oscillation signal (So), a direct conversion part (1) for performing frequency conversion by mixing a radio frequency signal (RF) in which a tone signal is superposed and the local oscillation signal (So), an FM detector part (2) for detecting a center frequency of the radio frequency signal (RF), and an AFC control part (73) for controlling the frequency of the local oscillation signal (So). The AFC control part (73) controls the local oscillator (4) so that the frequency of the local oscillation signal (So) matches the center frequency detected by the FM detector part (2).SELECTED DRAWING: Figure 1

Description

The present invention relates to a direct conversion radio receiver and the like.

A direct conversion radio receiver performs demodulation by mixing a received signal with a signal of a frequency very close to that of the received signal (received frequency) generated by a local oscillator inside the receiver. However, if the frequency of the received signal and the frequency of the local oscillator completely match, demodulation will not be possible. For this reason, it is generally known to set the frequency of the signal generated by the local oscillator inside the receiver to be different from the frequency of the received signal, as described in Patent Document 1.

Japanese Patent No. 5292061

However, for example, when receiving a signal containing a low frequency binary FSK signal (superimposed) such as a tone signal used in DCS (Digital Coded Squelch) with a direct conversion receiver, the following problems such as

When receiving a signal containing a binary FSK signal by the direct conversion method, the reception frequency is controlled by AFC (Automatic Frequency Control), which is shifted from the center frequency (carrier frequency) of the reception signal by several 10 Hz to 200 Hz. set as a target. Here, if the FSK signal included in the received signal has a low frequency like a tone signal, and if "1"s continue or "0"s continue, the center frequency of the binary FSK signal is It cannot be detected accurately in AFC. Therefore, the received frequency may deviate higher or lower than the target. In such a case, if a part of the modulated wave of the received FSK signal (for example, the modulated frequency of "1") matches the frequency of the local oscillator and is located in an area where decoding is not possible, the part of the modulated wave cannot be properly received.

An object of one aspect of the present invention is to stably receive a signal in a direct conversion wireless receiver.

In order to solve the above problems, a direct conversion radio receiver according to an aspect of the present invention includes a local oscillator that generates a local oscillation signal, a radio frequency signal on which a tone signal is superimposed, and the local oscillation signal. a frequency conversion unit that mixes and converts the frequency, a frequency detection unit that detects the center frequency of the radio frequency signal, and a control unit that controls the frequency of the local oscillation signal, wherein the control unit includes the local The local oscillator is controlled so that the frequency of the oscillator matches the center frequency detected by the frequency detector.

In order to solve the above problems, a control method for a direct conversion radio receiver according to an aspect of the present invention comprises: a local oscillator for generating a local oscillation signal; a radio frequency signal on which a tone signal is superimposed; A control method for a direct conversion radio receiver comprising: a frequency conversion unit that mixes and frequency-converts a local oscillation signal; and a frequency detection unit that detects the center frequency of the radio frequency signal, the method comprising: and controlling the local oscillator to match the frequency of the signal to the center frequency detected by the frequency detector.

According to the above configuration, when receiving the radio frequency signal on which the tone signal is superimposed, the local oscillation signal is adjusted to the center frequency of the detected radio frequency signal. Thereby, a radio frequency signal can be stably received.

In order to solve the above problems, a direct conversion radio receiver according to an aspect of the present invention includes a local oscillator that generates a local oscillation signal, and a radio frequency signal and the local oscillation signal that are mixed and frequency-converted. a frequency detector that detects the center frequency of the radio frequency signal; a controller that controls the frequency of the local oscillation signal; and whether a tone signal is superimposed on the received radio frequency signal. and a storage unit for storing received signal information indicating whether or not the local oscillation is generated based on the received signal information when the tone signal is superimposed on the radio frequency signal. While controlling the local oscillator so that the frequency of the signal matches the center frequency of the radio frequency signal, when the tone signal is not superimposed on the radio frequency signal, the frequency of the local oscillation signal is adjusted to the frequency of the radio frequency signal. The local oscillator is controlled to be offset with respect to the center frequency of the radio frequency signal.

In order to solve the above problems, a control method for a direct conversion radio receiver according to one aspect of the present invention provides a local oscillator that generates a local oscillation signal, and a radio frequency signal that mixes the local oscillation signal. and a frequency detector for detecting the center frequency of the radio frequency signal, wherein the radio frequency signal being received includes the Based on received signal information indicating whether or not a tone signal is superimposed, if the tone signal is superimposed on the radio frequency signal, the frequency of the local oscillation signal is changed to the center frequency of the radio frequency signal. while controlling the local oscillator to match the frequency of the radio frequency signal, and shifting the frequency of the local oscillation signal with respect to the center frequency of the radio frequency signal when the tone signal is not superimposed on the radio frequency signal controlling the local oscillator.

According to the above configuration, when receiving the radio frequency signal on which the tone signal is superimposed, the local oscillation signal is matched with the center frequency of the radio frequency signal. On the other hand, when receiving a radio frequency signal on which no tone signal is superimposed, the local oscillation signal is shifted with respect to the center frequency of the radio frequency signal. Therefore, the radio frequency signal can be stably received regardless of whether or not the tone signal is superimposed.

According to one aspect of the present invention, it is possible to stably receive a signal in a direct conversion radio receiver.

1 is a block diagram showing the configuration of main parts of a wireless receiver according to an embodiment of the present invention; FIG. 4 is a flow chart showing a procedure for setting a reception frequency by the radio receiver; FIG. 4 is a diagram showing an example of reception frequency setting for a DCS-modulated signal by the radio receiver; FIG. 5 is a diagram showing another example of setting of reception frequencies for DCS-modulated signals by the radio receiver; FIG. 10 is a diagram showing an example of reception frequency setting for a DCS-modulated signal by a wireless receiver of a comparative example; FIG. 9 is a diagram showing another example of setting of reception frequencies for DCS-modulated signals by the wireless receiver of the comparative example;

[Embodiment]
An embodiment of the present invention will be described in detail below with reference to FIGS. 1 to 6. FIG.

<Configuration of radio receiver>
FIG. 1 is a block diagram showing the configuration of the essential parts of a radio receiver 10 according to one embodiment of the present invention.

As shown in FIG. 1, the radio receiver 10 is a direct conversion radio receiver. The radio receiver 10 includes a direct conversion section 1 (frequency conversion section), an FM detection section 2 (frequency detection section), a noise detection section 3, a local oscillator 4, a storage device 5 (storage section), and an operation section. 6 and a control device 7 .

The direct conversion unit 1 mixes (multiplies) the received radio frequency signal RF and the local oscillation signal So, thereby frequency-converting the intermediate frequency signal into an intermediate frequency signal IF (converted signal) of 0 Hz. Therefore, although not shown, the direct conversion section 1 has a 90-degree phase shifter, a first mixer, a second mixer, two low-pass filters, and two AD converters. The radio frequency signal RF may or may not have a tone signal superimposed thereon.

The 90-degree phase shifter outputs a 0-degree oscillation signal with a phase difference of 0 degrees and a 90-degree oscillation signal with a phase difference of 90 degrees based on the local oscillation signal So. A first mixer frequency converts the radio frequency signal RF to an I signal by mixing it with the 0 degree oscillating signal. A second mixer frequency converts the radio frequency signal RF to a Q signal by mixing it with the 90 degree oscillating signal. The two low-pass filters remove unnecessary frequency components from the I and Q signals and output them. The two AD converters digitally convert the signals output from the two low-pass filters, respectively, and output an I-channel intermediate frequency signal IF and a Q-channel intermediate frequency signal IF.

The FM detector 2 outputs a low-frequency demodulated signal AF by performing demodulation based on the two intermediate frequency signals IF. The FM detector 2 also detects center frequencies of the two intermediate frequency signals IF and outputs center frequency information Fc to the AFC controller 73 of the controller 7 . The FM detector 2 is configured by, for example, a DSP (Digital Signal Processor) in order to perform signal processing digitally.

The noise detector 3 detects noise components mixed in the demodulated signal AF, and outputs the detected noise components as noise pulses Pn.

The local oscillator 4 has a VCO (Voltage Controlled Oscillator) and generates a local oscillation signal So. The local oscillator 4 converts the frequency of the local oscillation signal So output by the VCO to a reference signal having a frequency represented by the reception frequency setting information Sc output from the control device 7, and synchronizes the frequency with the reference signal. match. Therefore, the local oscillator 4 is composed of a PLL (Phase Lock loop) circuit.

The storage device 5 is composed of a semiconductor memory or the like, and stores reception frequency information and reception tone setting information. The reception frequency information is information about the reception frequency set for each channel, and includes tone signal information as to whether or not a tone signal is superimposed on the radio frequency signal RF received at the reception frequency. I'm in. The reception tone setting information is information in which either a DCS signal or a CTCSS (Continuous Tone-Coded Squelch System) signal is set as a tone signal waiting to be received when tone squelch is turned on.

The operation unit 6 receives various operations for the wireless receiver 10 . The operation unit 6 has keys, a dial, a display with a touch panel, and the like. The operation unit 6 outputs a dial operation signal Sd indicating a channel selection operation using a dial. Note that tone squelch ON/OFF is defined for each channel by reception tone setting information set in advance.

The control device 7 is composed of a processor such as a CPU (Central Processing Unit) and controls the operation of the local oscillator 4 . The control device 7 has a noise squelch control section 71, an information output control section 72, and an AFC (Automatic Frequency Control) control section 73 (control section) in order to realize its control function.

When the noise squelch control unit 71 recognizes that the noise pulse Pn from the noise detection unit 3 has detected a level of noise whose output should be blocked, the noise squelch control unit 71 closes the noise squelch by not outputting the noise squelch state signal SQL. Let Also, the noise squelch control unit 71 supplies a noise squelch state signal SQL to the AFC control unit 73 .

When the dial operation signal Sd is input from the operation unit 6 , the information output control unit 72 reads the reception frequency information about the channel selected by the dial operation signal Sd from the storage device 5 and outputs it to the AFC control unit 73 . do. Further, the information output control section 72 reads the reception tone setting information from the storage device 5 and outputs it to the AFC control section 73 when the tone operation signal St is input from the operation section 6 .

When the reception frequency information is input from the information output control section 72, the AFC control section 73, when the reception tone setting information is included in the reception frequency information, based on the center frequency information Fc from the FM detection section 2. , generates reception frequency setting information Sc for matching the frequency of the local oscillation signal So with the center frequency of the intermediate frequency signal IF, and outputs it to the local oscillator 4 .

AFC control section 73 receives reception frequency information from information output control section 72, does not contain tone signal information in the reception frequency information, and does not receive reception tone setting information from information output control section 72. In this case, based on the center frequency information Fc from the FM detector 2, the reception frequency setting information Sc for shifting the frequency of the local oscillation signal So from the center frequency of the intermediate frequency signal IF is generated and output to the local oscillator 4. do.

The AFC control unit 73 adjusts the frequency of the local oscillation signal So to the center frequency of the intermediate frequency signal IF while the noise squelch state signal SQL is output from the noise squelch control unit 71 and the noise squelch is open. perform the above control. On the other hand, in the state where the noise squelch is closed because the noise squelch state signal SQL is not output, the AFC control unit 73 performs the above control to match the frequency of the local oscillation signal So with the center frequency of the intermediate frequency signal IF. do not have.

In radio receiver 10, direct conversion section 1, FM detection section 2, AFC control section 73 and local oscillator 4 constitute an AFC section.

<Operation of radio receiver>
FIG. 2 is a flowchart showing a procedure (control method) for setting the reception frequency by the radio receiver 10. As shown in FIG.

As shown in FIG. 2, the AFC control unit 73 determines whether or not the noise squelch state is acquired based on the noise squelch state signal SQL from the noise squelch control unit 71 (step S1). Next, the AFC control unit 73 determines whether or not the noise squelch is open based on the acquired noise squelch state (step S2). When the AFC control unit 73 determines in step S2 that the noise squelch is closed (NO), the process returns to step S1.

Further, if the AFC control unit 73 determines in step S2 that the noise squelch is open (YES), the AFC control unit 73 acquires the center frequency information Fc from the FM detection unit 2 (step S3), and acquires the center frequency information Fc. Then, it is determined whether or not a certain period of time (for example, 200 milliseconds) has passed (step S4). If the AFC control unit 73 does not determine that the predetermined time has elapsed in step S4 (NO), the process returns to step S3.

The AFC control section 73 performs a control operation of the local oscillator 4 based on the result of analyzing the latest center frequency information Fc acquired within a certain period of time.

When the AFC control unit 73 determines that the predetermined time has elapsed in step S4 (YES), the AFC control unit 73 acquires reception frequency information and reception tone setting information from the information output control unit 72 (step S5). Based on the tone reception information, the AFC control unit 73 determines whether or not the tone signal is included (superimposed) in the received signal (step S6).

When the AFC control unit 73 determines in step S6 that the received signal contains a tone signal (YES), the AFC control unit 73 sets the target reception frequency, that is, the frequency of the local oscillation signal So of the local oscillator 4, to the frequency of the received signal. The local oscillator 4 is controlled so as to match the center of the frequency (step S7). As a result, the local oscillator 4 sets the frequency of the local oscillation signal So (step S8), and finishes the process.

When the AFC control unit 73 determines in step S6 that the tone signal is not included in the received signal (NO), the local oscillator 4 adjusts the received frequency to near the center of the frequency of the received signal. is controlled (step S9), and the process proceeds to step S8.

<Setting the reception frequency of the wireless receiver>
An example of setting the reception frequency when the radio receiver 10 receives a signal containing a DCS signal as a tone signal will be described. FIG. 3 is a diagram showing an example of reception frequency setting for a DCS-modulated signal by the radio receiver 10. As shown in FIG. FIG. 4 is a diagram showing another example of reception frequency setting for a DCS-modulated signal by radio receiver 10. In FIG.

In FIG. 3, the modulated wave of the DCS signal (binary FSK modulated wave) corresponds to the DCS signal "1" on the right end and the DCS signal "0" on the left end. The sweep at the time of frequency transition between appears as noise and looks like a band (gray part in FIG. 3).

As shown in FIG. 3, the AFC control unit 73 controls the local oscillation signal so that the reception frequency fc1, that is, the center frequency of the passband of the radio receiver 10, matches the center frequency fc2 of the reception signal containing the modulated wave of the DCS signal. Set the frequency of So. In this state, the modulated wave of the DCS signal cannot be received at the center frequency of the passband, but the modulated wave (spectrum) of the DCS signal exists across this region. In this state, the modulated wave of the DCS signal can be received without any problem. In addition, in the example shown in FIG. 3, a frequency margin is obtained in the high and low frequencies with respect to the above spectrum.

FIG. 4 shows a case where the accuracy of the frequency control of the AFC section described above is low, and a shift amount D occurs in the direction of the reception frequency fc1 higher than the reception state of FIG. Even in this case, the center frequency region that cannot be received by the radio receiver 10 is located inside the spectrum. As a result, even in this state, the modulated wave of the DCS signal can be received without any problem.

In the example shown in FIG. 4, a case in which the reception frequency is deviated in the higher direction has been described as an example. be able to. In other words, if the AFC section has frequency accuracy to the extent that the reception frequency fc1 falls within the spectrum, the modulated wave of the DCS signal can be received without any problem.

Next, an example of setting the reception frequency when the radio receiver of the comparative example receives a signal containing a DCS signal as a tone signal will be described. FIG. 5 is a diagram showing an example of reception frequency setting for a DCS-modulated signal by a wireless receiver of a comparative example. FIG. 6 is a diagram showing another example of reception frequency setting for a DCS-modulated signal by the wireless receiver of the comparative example.

The radio receiver of the comparative example does not have the AFC control section 73 like the radio receiver 10 and has a general AFC function. In FIG. 5, the radio receiver uses the normal AFC function to shift the reception frequency fc1 from the center frequency fc2 of the reception signal containing the modulated wave of the DCS signal by the amount of deviation D, as in FIG. indicates the case. Also in this case, similarly to the case shown in FIG. 4, the modulated wave of the DCS signal can be received without any problem.

FIG. 6 shows a case where the accuracy of frequency control of the AFC function is low, and the reception frequency fc1 further deviates from the reception state shown in FIG. In this case, it can be seen that the right end of the spectrum of the modulated wave of the DCS signal overlaps the area that the radio receiver cannot receive. Therefore, it becomes impossible to normally receive the "1" level of the DCS signal.

<Effect of the embodiment>
A radio receiver 10 according to this embodiment includes a local oscillator 4 , a direct conversion section 1 , an FM detection section 2 and an AFC control section 73 . The direct conversion unit 1 mixes the radio frequency signal RF on which the tone signal is superimposed and the local oscillation signal So from the local oscillator 4 to convert the radio frequency signal RF into two intermediate frequency signals IF having mutually orthogonal phases. to frequency conversion. FM detector 2 detects the center frequencies of the two intermediate frequency signals IF. The AFC controller 73 controls the local oscillator 4 so that the frequency of the local oscillation signal So matches the detected center frequency.

As a result, when receiving the radio frequency signal RF on which the tone signal is superimposed, the local oscillation signal So is matched with the center frequency of the tone signal. Thereby, the radio frequency signal RF can be stably received.

Also, as described above, even if the frequency control accuracy of the AFC section is low, the receiver can be put to practical use. Therefore, it is not necessary to secure a long time for analyzing the frequency or averaging the received frequency, which is the time required to improve the accuracy of the frequency control of the AFC unit, and the control of the local oscillator 4 can be performed in a short time. can be done.

The storage device 5 also stores reception signal information (reception frequency information and reception tone setting information) indicating whether or not a tone signal is superimposed on the radio frequency signal RF. When the tone signal is superimposed on the radio frequency signal RF, the AFC control section 73 controls the local oscillator 4 so that the frequency of the local oscillation signal So matches the detected center frequency. The AFC control unit 73 controls the local oscillator 4 to shift the frequency of the local oscillation signal So from the detected center frequency when the tone signal is not superimposed on the radio frequency signal RF.

As a result, when receiving the radio frequency signal RF on which the tone signal is superimposed, the local oscillation signal So is matched with the center frequency of the radio frequency signal RF. On the other hand, when receiving the radio frequency signal RF on which the tone signal is not superimposed, the local oscillation signal So is shifted with respect to the center frequency of the radio frequency signal RF. Therefore, the radio frequency signal RF can be stably received regardless of whether or not the tone signal is superimposed.

Also, the tone signal may be a DCS signal. As a result, the frequency of the local oscillation signal is adjusted to the center frequency of the received signal based on the frequency information, so that the frequency of the local oscillation signal can be controlled in a short period of time for the DCS signal whose center frequency is difficult to detect.

When receiving a low-speed binary FSK signal such as a DSC signal, the binary FSK signal is received as a modulated wave that reciprocates between two frequencies, a frequency shift to the higher side and a frequency shift to the lower side. will do. In this case, since the DCS signal is modulated at a low speed, the frequency shifts to the higher side or the lower side for a certain period of time when divided by unit time. Further, since the DCS signal is modulated with logical data of "1" or "0", the duty ratio between "1" and "0" is also different.

When receiving the modulated wave of the DCS signal as described above, it is difficult to find the center frequency, and it tends to be detected on the high side or the low side. If an attempt is made to improve the frequency accuracy of the AFC unit, improvement can be expected by lengthening the frequency analysis time or lengthening the frequency averaging processing time. However, the frequency control by the AFC control unit 73 eventually takes time, so it is not practical.

Note that this embodiment is also effective in the case of digital wireless communication in which the pass band for reception is a narrow band.

Further, as described above, the ON/OFF of the tone squelch may be switched by the user's operation on the operation unit 6 without being limited to the setting in advance. In such a configuration, for example, the display with a touch panel of the operation unit 6 is provided with an operation key as a tone key for turning on/off the tone squelch. The operation unit 6 outputs tone key operations as tone operation signals. The setting of the tone squelch is sequentially switched between DCS signal selection, CTCSS signal selection, and tone squelch OFF each time the tone key is pressed.

When the tone key is operated to turn on the tone squelch, the AFC control unit 73 controls the local oscillator 4 so that the frequency of the local oscillation signal So matches the detected center frequency. Further, when the tone squelch is turned off, the AFC control section 73 controls the local oscillator 4 so as to shift the frequency of the local oscillation signal So from the detected center frequency.

[Example of realization by software]
The function of the control device 7 of the wireless receiver 10 is a program for causing a computer to function as the control device 7 , and can be realized by a program for causing the computer to function as each part of the control device 7 .

In this case, the control device 7 comprises a computer having at least one processor and at least one storage device 5 as hardware for executing the program. By executing the above program using the control device 7 and the storage device 5, each function described in each of the above embodiments is realized.

The program may be recorded on one or more computer-readable recording media, not temporary. The recording medium may or may not be included in the device. In the latter case, the program may be supplied to the device via any transmission medium, wired or wireless.

Also, part or all of the functions of the respective control units can be realized by logic circuits. For example, integrated circuits in which logic circuits functioning as the control blocks described above are formed are also included in the scope of the present invention. In addition, it is also possible to implement the functions of the control blocks described above by, for example, a quantum computer.

[Additional notes]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Further, embodiments obtained by appropriately combining technical means disclosed in the embodiments are also included in the technical scope of the present invention.

1 Direct conversion section (frequency conversion section)
2 FM detector (frequency detector)
4 local oscillator 5 storage device (storage unit)
10 wireless receiver 73 AFC control unit (control unit)
IF Intermediate frequency signal (converted signal)
RF Radio frequency signal So Local oscillation signal

Claims (5)

a local oscillator that generates a local oscillation signal;
a frequency conversion unit that mixes a radio frequency signal on which a tone signal is superimposed and the local oscillation signal and converts the frequency;
a frequency detection unit that detects the center frequency of the radio frequency signal;
a control unit that controls the frequency of the local oscillation signal,
The direct conversion radio receiver, wherein the controller controls the local oscillator so that the frequency of the local oscillator matches the center frequency detected by the frequency detector. a local oscillator that generates a local oscillation signal;
a frequency converter for mixing and frequency-converting the radio frequency signal and the local oscillation signal;
a frequency detection unit that detects the center frequency of the radio frequency signal;
a control unit that controls the frequency of the local oscillation signal;
a storage unit that stores received signal information indicating whether or not a tone signal is superimposed on the received radio frequency signal,
Based on the received signal information, the control unit adjusts the frequency of the local oscillation signal to match the center frequency of the radio frequency signal when the tone signal is superimposed on the radio frequency signal. While controlling the local oscillator, when the tone signal is not superimposed on the radio frequency signal, the local oscillator is controlled so as to shift the frequency of the local oscillation signal with respect to the center frequency of the radio frequency signal. A direct conversion radio receiver. 3. The direct conversion radio receiver according to claim 1, wherein said tone signal is a DCS (Digitally Coded Squelch) signal. a local oscillator for generating a local oscillation signal; a frequency converter for mixing and frequency-converting a radio frequency signal on which a tone signal is superimposed and the local oscillation signal; and a frequency detector for detecting the center frequency of the radio frequency signal. A control method for a direct conversion radio receiver comprising:
A control method for a direct conversion radio receiver, comprising controlling the local oscillator so that the frequency of the local oscillation signal matches the center frequency detected by the frequency detector. Direct conversion comprising: a local oscillator that generates a local oscillation signal; a frequency converter that mixes and converts a radio frequency signal and the local oscillation signal; and a frequency detector that detects the center frequency of the radio frequency signal. A method of controlling a radio receiver of the system,
Based on received signal information indicating whether or not a tone signal is superimposed on the radio frequency signal being received, if the tone signal is superimposed on the radio frequency signal, the frequency of the local oscillation signal is adjusted to match the center frequency of the radio frequency signal, and if the tone signal is not superimposed on the radio frequency signal, the frequency of the local oscillation signal is adjusted to the radio frequency signal controlling the local oscillator so as to deviate from the center frequency of the direct conversion radio receiver.

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