JP2004229170A - Receiver and receiving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively attenuate an IM (Inter modulation) jamming station signal level and to suppress the drop of a receiving station signal level in this case. <P>SOLUTION: This receiver is provided with a main tuner 51 and a sub-tuner 52, detects the states of broadcast radio waves by using the sub-tuner while receiving and demodulating the broadcast radio waves by using the main tuner, and controls the receiving states in the main tuner on the basis of a detection result. A tuning frequency control part 53 detects two stations which may function as mutual modulation jamming stations to a receiving station by using the sub-tuner, separates the tuning frequency of a tuning circuit from the jamming station frequency when the difference between the frequency of a jamming station nearer to the receiving station among the two stations and the frequency of the receiving station is equal to or smaller than a first setting value and brings the tuning frequency of the tuning circuit closer to the jamming station frequency when the difference is equal to or greater than a second setting value which is larger than the first setting value. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a receiver and a method of receiving the same, and in particular, comprises a main tuner and a sub-tuner, while receiving and demodulating a broadcast radio wave with the main tuner, detecting the state of the broadcast radio wave with the sub-tuner, The present invention relates to a receiver that controls a reception state in a main tuner based on the reception method and a reception method thereof.
[0002]
[Prior art]
FIG. 6 is a configuration diagram of a receiver provided with a conventional single tuner. A broadcast radio wave received by an antenna AT is tuned by a tuning unit 11, and then input to a high-frequency amplifier 12 and amplified. The output of the high-frequency amplifier 12 is input to the tuning unit 13, where the output is tuned again and then output to the mixer 14. Then, the mixer 14 is mixed with a local oscillation frequency signal output from a local oscillator 16 that is PLL-controlled by the microcomputer 10 and becomes an intermediate frequency signal IF. One of the intermediate frequency signals IF is input to the variable bandpass filter 15 and the bandwidth thereof is limited, and then detected by the detection unit 17 to become a low frequency signal. The other is input to the AGC circuit 19 and Level is detected. The signal level is fed back to the high-frequency amplifier 12 to control the gain of the high-frequency amplifier 12, and the low-frequency signal is amplified by the low-frequency amplifier 18 and then input to a speaker (not shown) via an audio circuit.
[0003]
In such a receiver, the AGC circuit 19 controls the gain of the high-frequency amplifier 12 to remove the interference signal. However, at this time, what is detected by the AGC circuit is the level of the interference signal, and the frequency relationship between the receiving station frequency and the interference signal frequency is ignored. For this reason, even if the frequency signal does not disturb the frequency signal of the receiving station in terms of frequency, if the signal level is high, the AGC operates to lower the desired signal output level.
[0004]
For this reason, Japanese Patent Laid-Open Publication No. Hei 6-291688 discloses a main tuner and a sub tuner. The main tuner receives and demodulates a broadcast wave, detects the state of the broadcast wave with the sub tuner, and based on the detected result, A receiver for controlling a reception state in a tuner has been proposed. That is, the sub-tuner checks whether adjacent interference has occurred, and if so, narrows the band of the variable bandpass filter 15 and checks whether inter-modulation (IM) interference has occurred. If so, the input level is suppressed by suppressing the AGC voltage.
[Patent Document 1] Japanese Patent Application Laid-Open No. 6-291688
[Problems to be solved by the invention]
However, the related art has the following problems when suppressing intermodulation interference (IM interference). That is,
(1) In the prior art, when a strong input is detected, the antenna input signal is attenuated by the detected voltage value, and IM interference is improved by attenuating the interfering station together with the receiving station. That is, in order to attenuate the interfering station, the signal is attenuated to the own station, and a mute operation is performed.
(2) If the attenuation operation is stopped under certain conditions in order to avoid the mute phenomenon due to attenuation of the own station, there is a problem that the anti-jamming characteristics cannot be sufficiently obtained.
(3) In the case of the single tuner of FIG. 6, as shown in FIG. 7, there may be a case where an interfering station cannot be detected due to the selection characteristics of the tuning circuit. In such a case, there is a problem that the attenuation operation is not performed. That is, there is a problem that an interfering station exceeding the selection range SFR cannot be detected, and a correct measure against intermodulation interference (IM interference) cannot be taken.
Accordingly, it is an object of the present invention to effectively attenuate the IM jammer signal level.
It is another object of the present invention to suppress a decrease in the signal level of the receiving station even if the signal level of the IM interfering station is attenuated.
It is another object of the present invention to reduce the frequency of occurrence of IM interference by detecting an interference station signal level and performing AGC operation.
[0006]
[Means for Solving the Problems]
According to the present invention, a main tuner and a sub-tuner are provided. The main tuner receives and demodulates a broadcast wave, detects a state of the broadcast wave in the sub-tuner, and receives the broadcast wave in the main tuner based on the detection result. In a receiver for controlling a state, a sub-tuner is used to detect two stations serving as intermodulation interfering stations with respect to a receiving station. When the frequency difference is equal to or less than the first set value, the tuning frequency of the tuning circuit is separated from the interference station frequency, and when the difference is equal to or greater than the second set value which is larger than the first set value, the tuning circuit is tuned. This is achieved by moving the frequency closer to the jammer frequency.
In this case, two stations having a frequency relationship with respect to the receiving station that can be an intermodulation interfering station and having a received electric field strength equal to or higher than a set value and an AGC voltage equal to or higher than the set value are set as the intermod interfering stations. By determining that the number of stations is one, it is possible to effectively reduce intermodulation interference.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
(A) Schematic diagram of the present invention FIG. 1 is a schematic explanatory diagram of the present invention. In FIG. 1 (A), a tuning characteristic 1 of the tuning circuit has a characteristic that the center frequency is fh, and is separated from the center frequency fh by a frequency A. The frequency deviated from the center frequency fh by a frequency B (> A) is denoted by fb. Assuming that the receiving station frequency is fh, the station frequencies of two stations serving as intermodulation interfering stations are f1 and f2, and the interfering station frequency close to the receiving station frequency fh is f1, the following equation | f1-fh | = | f2-f1 | (1)
Holds. However, even if the equation (1) is satisfied, if the reception strength of the intermodulation interfering station is small, the intermodulation interference does not occur. On the other hand, if the expression (1) is satisfied and the reception intensity of the intermodulation interfering station is high, intermodulation interference occurs.
[0008]
When intermod interference occurs, two stations which are to be intermod interference stations with respect to the receiving station are detected using the sub-tuner. Next, a difference Δf (= | f1−fh |) between the frequency f1 of the interfering station close to the receiving station and the receiving station frequency fh of the two stations is equal to or more than the first set value A and equal to or less than the second set value B , In other words, whether fa <f1 <fb. In the case of FIG. 1A, since it is “YES”, the center frequency of the tuning circuit is not changed. That is, in the case of FIG. 1A, nothing is performed because the signal level L1 of the interfering station frequency f1 becomes smaller due to the tuning characteristics (selection characteristics).
On the other hand, if the difference Δf (= | f1−fh |) is equal to or less than the first set value A, that is, if f1 ≦ fa, as shown in FIG. L1 increases, and the frequency of occurrence of intermodulation interference increases. Therefore, in such a case, the tuning frequency fh of the tuning circuit is shifted by the set frequency C in a direction away from the interfering station frequency f1 as shown by a dotted line 2 in FIG. By doing so, the signal level at the interfering station frequency f1 is reduced to L1 ', and intermodulation interference is reduced. Note that the shift of the tuning frequency fh also lowers the signal level of the receiving station, but the amount of reduction is much smaller than the signal level of the interfering station.
[0009]
If the difference Δf (= | f1−fh |) is equal to or greater than the second set value B, that is, if fb ≦ f1, as shown in FIG. 1C, the interference station frequency f1 is outside the tuning frequency. It becomes. However, distortion occurs in a non-linear portion (a diode, a transistor, or the like) of an amplifier or the like to generate a distortion component, and as if another wave is generated. When this wave enters the reception tuning frequency range, it becomes intermodulation noise. Therefore, the tuning frequency fh of the tuning circuit is set in a direction closer to the interfering station frequency f1 as shown by a dotted line 3 in FIG. 1C so that the frequency of occurrence of intermodulation interference is low and AGC control can be performed. Shift by frequency C. This makes it possible to detect the signal level L1 ″ at the interfering station frequency f1, thereby enabling AGC control and reducing the frequency of occurrence of intermodulation interference. In addition, by shifting the tuning frequency fh Although the signal level of the receiving station also decreases, the effect of reducing the intermodulation interference by enabling the AGC control is greater.
[0010]
(B) Configuration of Receiver FIG. 2 is a configuration diagram of a receiver according to the present invention, and includes a reception tuner (main tuner) 51, a detection tuner (sub tuner) 52 for detecting a reception state, a sub tuner and a main tuner. A tuning frequency control unit 53 provided between the tuners and having a microcomputer configuration for performing tuning frequency control is provided. The receiving tuner 51 and the detecting tuner 52 have substantially the same configuration, and only the internal configuration of the detecting tuner 52 is shown. Note that, in addition to the configuration shown in the drawing, the reception tuner 51 is provided with a detection unit that detects the intermediate frequency signal and outputs the signal to the speaker side.
The broadcast radio wave received by the antenna ATT is tuned by the first tuning unit 61 and then input to the high frequency amplifier 62 and amplified. The output of the high-frequency amplifier 62 is input to the second tuning unit 63, where the output is tuned again and then output to the mixer 64. The mixer 64 mixes the local oscillation frequency signal output from the local oscillator 66, which is PLL-controlled by the tuner control unit 60, with the output signal of the second tuning circuit, and outputs an intermediate frequency signal IF. The intermediate frequency amplifier 65 limits the bandwidth and amplifies it with a built-in intermediate frequency filter and intermediate frequency amplifier. The strong electric field detector 67 inputs the output signal of the second tuning circuit 63 to the attenuation signal generation circuit (AGC circuit) 68, compares the output signal level with the set level, and if the output signal level is equal to or higher than the set level. The strong electric field detection signal is input to the tuner unit 60. The AGC circuit 68 controls the first tuning circuit 61 and the high-frequency amplifier circuit 62 to reduce the interference level if the interference level included in the output signal of the second tuning circuit 63 is high. An electric field strength generation circuit (S meter) 69 monitors the output signal level of the intermediate frequency amplifier 65 and outputs an S meter voltage.
The tuner control unit 60 executes electronic tuning control (seek control) to detect the reception state of each broadcast station signal. That is, it instructs the tuning voltage generation circuit 70 to tune to each broadcast station frequency as appropriate, and controls the local oscillator 66 to emit at a local oscillation frequency corresponding to the broadcast station frequency. The tuning voltage generation circuit 70 generates a tuning voltage so as to have tuning characteristics having the designated broadcast station frequency as a center frequency, and inputs the tuning voltage to the first and second tuning circuits 61 and 63.
Further, the tuner control unit 60 acquires the strong electric field detection signal and the S meter voltage from the strong electric field detection circuit 67 and the electric field strength generation circuit 69 and inputs them to the tuning frequency control unit 53.
[0012]
FIG. 3 is a tuning frequency control processing flow of the tuning frequency control unit 53 of the present invention. The receiving station (receiving station frequency fh) is input to the tuning frequency control unit 53 from an operation unit (not shown), and the receiving tuner 51 transmits a broadcast radio signal of the receiving station frequency fh specified by the control of the tuning frequency control unit 53. Receiving.
The tuning frequency control unit 53 performs seek control of the sub-tuner 52 to acquire the strong electric field detection signal and the S meter voltage output from the strong electric field detection circuit 67 for each of the 76 MHz to 90 MHz FM broadcast stations, and to perform intermodulation interference. An FM broadcast station that can be a station is detected (step 101). When the S-meter voltage (reception electric field strength) is equal to or higher than a set value (= 95% of the saturation voltage) and the output signal of the second tuning circuit 63 is equal to or higher than the set level (the AGC amount is large), an intermodulation interference station can be obtained. It is determined to be an FM broadcast station.
When the search for the FM broadcast station that can be the intermodulation interfering station is completed, it is checked whether there are two stations that satisfy the IM condition (Equation (1)) (step 102). If there are two or more interfering stations, it is checked whether or not there are two stations satisfying the above conditions in all combinations of the interfering stations.
[0013]
If there are no two stations that satisfy the IM condition, the shift operation of the center frequency of the first and second tuning circuits 61 and 63 of the receiving tuner 51 is stopped or canceled (step 103), and the process ends.
If there are two stations satisfying the IM conditions, the target IM station is selected (step 104). Next, it is checked whether there is a strong input station near the target IM station (step 105). If there is, a shift operation of the center frequency of the first and second tuning circuits 61 and 63 of the receiving tuner 51 is performed. Stop or release (step 103) and end the process. This is for the purpose of avoiding suppression by a nearby interfering station. That is,
When (1) | f1-fh | <A, another strong input station exists near the opposite side to f1, and when (2) | f1-fh |> B, another strong input station exists near the f1 side. If a strong input station is present, shifting the center frequency of the tuning circuit will excessively attenuate the fh signal. For this reason, the determination in step 105 is performed, and if there is a strong input station near the target IM station, the shift operation is not performed.
[0014]
On the other hand, if there is no strong input station near the target IM station, the central frequency shift operation of the first and second tuning circuits 61 and 63 is performed by the method according to FIG. 1 (step 106). The details of step 106 are as follows. Here, the receiving station frequency is fh, the station frequencies of two stations that are intermodulation interfering stations are f1 and f2, and the interfering station frequency f1 of the two stations that is closer to the receiving station.
First, a difference Δf (= | f1−fh |) between the frequency f1 and the receiving station frequency fh is equal to or more than the first set value A and equal to or less than the second set value B, in other words, fa <f1 <fb. Check if it is. In the case of FIG. 1A, since it is “YES”, the center frequency of the tuning circuit is not changed.
On the other hand, if the difference Δf (= | f1−fh |) is equal to or less than the first set value A, the tuning frequency fh of the tuning circuit is separated from the interference station frequency f1 as shown by a dotted line 2 in FIG. To the set frequency C.
[0015]
If the difference Δf (= | f1−fh |) is equal to or greater than the second set value B, that is, if fb ≦ f1, the tuning frequency fh is disturbed as shown by a dotted line 3 in FIG. The frequency is shifted by the set frequency C in a direction approaching the station frequency f1.
As described above, in the case of FIG. 1B, the signal level at the interfering station frequency f1 is as low as L1 ′, and intermodulation interference is reduced. In this case, the signal level of the receiving station is reduced by shifting the tuning frequency fh, but the amount of reduction is much smaller than the signal level of the interfering station. 1C, the signal level L1 ″ at the interfering station frequency f1 can be detected, AGC control can be performed, and the frequency of occurrence of intermodulation interference can be reduced. In this case, the tuning frequency By shifting fh, the signal level of the receiving station is reduced, but the AGC control becomes possible, and the effect of reducing intermodulation interference is greater.
[0016]
(C) Effect FIG. 4 is an explanatory diagram of the effect when the tuning frequency is kept away when f1 ≦ fa, where the horizontal axis is Δf and the vertical axis is the mute amount of the receiving station when the disturbing station is at a certain level. is there. In the figure, a indicates a case where the tuning frequency is not shifted, b indicates a case where the tuning frequency is moved away from the interference frequency, and c indicates a case where the tuning frequency approaches the interference frequency. In FIG. 1B, A = 3.5 MHz. , B = 4.0 MHz and C = 1.0 MHz. FIG. 4 shows that the mute amount of the receiving station is reduced.
[0017]
FIG. 5 is an explanatory diagram of the effect when the tuning frequency is brought closer in the case of fb ≦ f1, where the horizontal axis is Δf, and the vertical axis is the level of the interfering station when a certain IM interference occurs in the receiving station. In the figure, a indicates a case where the tuning frequency is not shifted, and b indicates a case where the tuning frequency approaches the interference frequency. In FIG. 1C, A = 3.5 MHz, B = 4.0 MHz, and C = 1.0 MHz, respectively. And From FIG. 5, it can be seen that the level of the interfering station when a certain IM interference occurs at the receiving station is high. That is, it can be seen that IM interference is less likely to occur at the receiving station than when the tuning frequency is not shifted.
[0018]
【The invention's effect】
According to the present invention, the sub-tuner is used to detect two intermodulation interfering stations with respect to the receiving station, and the difference between the frequency of the interfering station near the receiving station and the frequency of the receiving station is detected. If the difference is less than the first set value, the tuning frequency of the tuning circuit is separated from the interfering station frequency, and if the difference is not less than the second set value which is larger than the first set value, the tuning frequency of the tuning circuit is disturbed. Since the frequency is set close to the station frequency, the IM interference station signal level can be effectively attenuated. In this case, even if the IM interfering station signal level is attenuated, a decrease in the receiving station signal level can be suppressed.
Further, according to the present invention, the frequency of IM interference can be reduced by the AGC operation by reliably detecting the interference station signal level.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram of the present invention.
FIG. 2 is a configuration diagram of a receiver according to the present invention.
FIG. 3 is a tuning frequency control processing flow of a tuning frequency control unit of the present invention.
FIG. 4 is an explanatory diagram of an effect when a tuning frequency is kept away when f1 ≦ fa.
FIG. 5 is an explanatory diagram of an effect when the tuning frequency is approximated when fb ≦ f1.
FIG. 6 is a configuration diagram of a receiver including a conventional single tuner.
FIG. 7 is an explanatory diagram in a case where an interfering station cannot be detected due to a selection characteristic of a tuning circuit.
[Explanation of symbols]
51 Tuner for reception (main tuner)
52 Tuner for detection (sub tuner)
53 Tuning frequency control unit 60 Tuner control unit 61 First tuning unit 62 High frequency amplifier 63 Second tuning unit 64 Mixer 65 Intermediate frequency amplifier 66 Local oscillator 67 Strong electric field detection unit 68 AGC circuit 69 Electric field intensity generation circuit (S meter)
70 Tuning voltage generation circuit

Claims (3)

A receiver that includes a main tuner and a sub tuner, detects the state of the broadcast wave with the sub tuner while receiving and demodulating the broadcast wave with the main tuner, and controls the reception state of the main tuner based on the detection result. A tuner is used to detect two stations that are intermodulation interfering stations for the receiving station, and the difference between the frequency of the interfering station that is closer to the receiving station and the receiving station frequency is the first set value. In the following cases, the tuning frequency of the tuning circuit is separated from the interfering station frequency, and when the difference is equal to or greater than a second set value larger than the first set value, the tuning frequency of the tuning circuit approaches the interfering station frequency. Control unit,
A receiver comprising: A reception field strength detection unit for detecting a reception field strength,
An AGC detector for detecting an AGC voltage,
The tuning frequency control unit has a frequency relationship that can be an intermodulation interfering station with respect to the receiving station, and the received electric field strength is equal to or higher than a set value and the AGC voltage is equal to or higher than the set value. Determine that the two stations are intermodulation jamming stations,
The receiver according to claim 1, wherein: A receiving method comprising a main tuner and a sub-tuner, wherein the main tuner receives and demodulates a broadcast wave, detects a state of the broadcast wave with the sub-tuner, and controls a reception state in the main tuner based on the detection result. At
The sub-tuner is used to detect two inter-modulation interfering stations with respect to the receiving station,
When the difference between the frequency of the interfering station close to the receiving station and the receiving station frequency of the two stations is equal to or less than a first set value, the tuning frequency of the tuning circuit is separated from the interfering station frequency;
When the difference is equal to or greater than a second set value larger than the first set value, the tuning frequency of the tuning circuit is brought closer to the interference station frequency;
A receiving method of a receiver, characterized in that:

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