JP4166427B2 - Receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a receiving apparatus that prevents interference caused by radio waves transmitted from other broadcast stations when receiving radio waves transmitted from a specific broadcast station. More specifically, the present invention relates to a bandpass filter that passes an intermediate frequency signal. The present invention relates to a receiving apparatus that prevents interference by radio waves transmitted by other broadcasting stations by changing the frequency bandwidth of a signal.
[0002]
[Prior art]
Conventionally, when receiving radio waves transmitted by a specific broadcasting station, by changing the frequency bandwidth of the signal that is passed by the bandpass filter that passes the intermediate frequency signal, interference from radio waves transmitted by other broadcasting stations is prevented. An FM receiver as shown in FIG. 6 is known as a receiving apparatus.
[0003]
Hereinafter, the operation of the conventional FM receiver 200 will be described with reference to FIGS. 6 and 7.
[0004]
The FM receiver 200 receives a radio wave by the receiving antenna 201, and stably selects and amplifies a radio wave transmitted from a received radio wave by a broadcasting station desired to be received by the tuning circuit 202 (hereinafter referred to as a desired broadcast station). To do. The radio wave stably selected and amplified by the tuning circuit 202 is mixed by the mixer circuit 203 with a signal having a frequency 10.7 MHz higher than the frequency of the radio wave transmitted by the desired broadcast station, so that the frequency is 10.7 MHz. The frequency is converted to an intermediate frequency and converted to an intermediate frequency signal. Here, a signal having a frequency 10.7 MHz higher than the frequency of the radio wave transmitted by the desired broadcast station is oscillated by a local oscillation circuit (not shown) in the PLL circuit 207. The PLL circuit 207 is controlled by the microcontroller 208.
[0005]
The intermediate frequency signal converted by the mixer circuit 203 is reduced by an IF (Intermediate Frequency) filter circuit 204 by radio wave interference (hereinafter referred to as adjacent interference) due to radio waves transmitted by a broadcast station other than the desired broadcast station. After the amplification, the limiter amplifier 205 limits the amplitude so that only the frequency component is obtained. When the intermediate frequency signal is made only the frequency component by the limiter amplifier 205, the detection circuit 206 generates an audio signal from the intermediate frequency signal and transmits the generated audio signal to a demodulation circuit and audio not shown.
[0006]
The intermediate frequency signal that has been made to have only the frequency component by the limiter amplifier 205 is detected by the adjacent interference detection circuit 209 for the strength of the adjacent interference received, and the detected adjacent interference strength is detected by the adjacent interference detection circuit 209. It is output to the controller 208. The microcontroller 208 to which the level of the adjacent disturbance is output determines whether the intermediate frequency signal whose frequency component is made only by the limiter amplifier 205 is subjected to the adjacent disturbance according to the level of the adjacent disturbance. Is immediately subject to adjacent interference, the IF filter circuit 204 is immediately made to narrow the IF filter bandwidth to reduce adjacent interference.
[0007]
More specifically, as shown in FIG. 7, when receiving the FM broadcast, the microcontroller 208 causes the adjacent disturbance detection circuit 209 to detect the strength of the adjacent disturbance for a certain time (step S251), and for a certain time. In step S252, it is determined whether there is an adjacent disturbance.
[0008]
If it is determined that there is an adjacent disturbance for a certain time, the microcontroller 208 reduces the adjacent interference by reducing the IF filter bandwidth to the IF filter circuit 204 (step S255), and again for a certain time. Then, the adjacent disturbance detection circuit 209 is caused to detect the strength of the adjacent disturbance (step S251). If it is determined that there is no adjacent interference for a fixed time, the microcontroller 208 determines whether or not the bandwidth of the IF filter of the IF filter circuit 204 is in a maximum state (step S253).
[0009]
If the microcontroller 208 determines that the IF filter bandwidth of the IF filter circuit 204 is in the widest state, the microcontroller 208 again causes the adjacent interference detection circuit 209 to detect the strength of the adjacent interference for a predetermined time (step S251). . If the microcontroller 208 determines that the IF filter bandwidth of the IF filter circuit 204 is not maximally wide, the microcontroller 208 causes the IF filter circuit 204 to increase the IF filter bandwidth by one step (step S254), and again. For a certain period of time, the adjacent interference detection circuit 209 is caused to detect the strength of adjacent interference (step S251).
[0010]
As described above, when the FM receiver 200 receives a radio wave transmitted by a specific broadcast station, that is, a desired broadcast station, the radio wave transmitted by another broadcast station, that is, a broadcast station other than the desired broadcast station. To prevent interference.
[0011]
[Problems to be solved by the invention]
However, in the above conventional receiver, when the judgment of the strength of adjacent interference is frequently reversed or fluctuated in a short time due to a large fluctuation of the electric field strength, the bandwidth of the IF filter is not stable, so that the audibility There is a problem that the above-mentioned uncomfortable feeling is caused, or that noise is generated in the intermediate frequency signal due to adjacent interference immediately after expanding the bandwidth of the IF filter.
[0012]
SUMMARY OF THE INVENTION An object of the present invention is to provide a receiving apparatus in which the bandwidth of an IF filter is stable and noise is prevented from occurring in an intermediate frequency signal.
[0013]
[Means for Solving the Problems]
Receiving apparatus of the present invention, among a plurality of broadcast stations and transmits the converted signal to different radio wave frequencies, respectively, when the first broadcast station receives that electric waves be transmitted, among the multiple broadcast stations in the receiving apparatus to prevent interference other broadcaster according to that radio waves transmitted, and receives the electric waves, out of the received electric wave, converts the frequency of that radio waves be transmitted one broadcasting station to an intermediate frequency by a frequency conversion means for generating an intermediate frequency signal from the received radio waves, among between-frequency signal in the frequency converting means to produce, during frequency in the frequency bandwidth around the inter-frequency medium a bandpass filter for passing a signal, of between frequency signals within you pass a band pass filter, the signal level detecting means for detecting the signal level between frequency signal among the other broadcast stations corresponding to that radio waves to send If, prior to the current signal level is signal level detecting means detects And the comparison / counting means for counting the number n of times that the current signal level was low, and the number n counted by the comparison / counting means reaches a predetermined integer N (N is an integer of 2 or more). Then, bandwidth changing means for expanding the frequency bandwidth of the band filter is provided.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
[0017]
A receiving apparatus according to the first embodiment of the present invention will be described with reference to FIGS.
[0018]
First, the configuration of the receiving apparatus according to the present embodiment will be described with reference to FIG.
[0019]
In FIG. 1, among a plurality of broadcast stations that convert signals to radio waves having different frequencies, and transmit a radio wave transmitted by one broadcast station, that is, a desired broadcast station, An FM receiver 100 that prevents interference by radio waves transmitted by other broadcast stations, that is, broadcast stations other than the desired broadcast station, includes a receiving antenna 101 that receives broadcast radio waves transmitted from the broadcast station, and radio waves of the desired broadcast station. A tuning circuit 102 that stably selects and amplifies the signal, and a mixer circuit 103 that generates an intermediate frequency signal from the radio wave amplified by the tuning circuit 102 by converting the frequency of the radio wave amplified by the tuning circuit 102 into an intermediate frequency. And.
[0020]
Here, the receiving antenna 101, the tuning circuit 102, and the mixer circuit 103 receive radio waves and convert the received radio waves by converting the frequency of the radio waves transmitted by the desired broadcast station to an intermediate frequency. Constitutes a frequency converting means for generating an intermediate frequency signal.
[0021]
Further, the FM receiver 100 includes an IF filter as a band filter that passes an intermediate frequency signal centered on the intermediate frequency among the intermediate frequency signals generated by the frequency conversion means, that is, an IF filter bandwidth. The IF filter circuit 104, the limiter amplifier 105 that limits the amplitude of the intermediate frequency signal passing through the IF filter, and uses the intermediate frequency signal as a frequency component only, generates an audio signal from the intermediate frequency signal, and generates the generated audio signal. A demodulation circuit (not shown) and a detection circuit 106 for transmitting to audio.
[0022]
Further, the FM receiver 100 has a local oscillation circuit (not shown), and oscillates a signal having a frequency 10.7 MHz higher than the frequency of the radio wave transmitted by the desired broadcast station by the local oscillation circuit. Of the intermediate frequency signal corresponding to the radio wave transmitted by the broadcast station other than the desired broadcast station among the intermediate frequency signals passing through the IF filter. And an adjacent disturbance detection circuit 109 as a signal level detection means for detecting. Here, the microcontroller 108 constitutes a bandwidth changing unit that changes the IF filter bandwidth in five steps in accordance with the signal level detected by the adjacent interference detection circuit 109.
[0023]
The microcontroller 108 divides the signal level into a plurality of areas according to the value of the signal level, and corresponds to one of the IF filter bandwidths among the five stages of IF filter bandwidths according to the divided areas. When the IF filter bandwidth to which the signal level detected by the adjacent interference detection circuit 109 is made to correspond is smaller than the actual IF filter bandwidth, the actual IF filter bandwidth is detected as the adjacent interference detection. The signal level detected by the circuit 109 is changed to the corresponding IF filter bandwidth.
[0024]
In addition, the microcontroller 108 determines the actual IF filter when the IF filter bandwidth to which the signal level detected by the adjacent disturbance detection circuit 109 is associated is not narrower than the actual IF filter bandwidth for a period shorter than a predetermined time. The IF filter bandwidth to which the signal level detected by the adjacent interference detection circuit 109 is made to correspond is narrower than the actual IF filter bandwidth for a predetermined time. If not, the actual IF filter bandwidth is changed to a IF filter bandwidth that is one step wider.
[0025]
Next, the operation of the receiving apparatus according to this embodiment will be described with reference to FIGS.
[0026]
As shown in FIG. 2, when receiving the FM broadcast, the microcontroller 108 causes the adjacent disturbance detection circuit 109 to detect the strength of the adjacent disturbance for a predetermined time (step S111), and detects the adjacent interference for the predetermined time. It is determined whether it has been received (step S112). Here, the microcontroller 108 detects the average value of the signal level of the intermediate frequency signal corresponding to the radio wave transmitted by the broadcast station other than the desired broadcast station detected by the adjacent disturbance detection circuit 109 for a predetermined time (hereinafter referred to as adjacent detection). It is determined whether or not the adjacent disturbance is received. Further, as shown in FIG. 3, when the adjacent detection voltage is V1, that is, the range of Va or more and less than Vb, the microcontroller 108 determines that the adjacent detection voltage is not received, and the adjacent detection voltage is V2, V3, If it is in the range of either V4 or V5, it is determined that the adjacent disturbance has been received.
[0027]
If it is determined in step S112 that adjacent interference has been received for a certain period of time, the microcontroller 108 detects the actual IF filter bandwidth, that is, the adjacent detection voltage corresponding to the current IF filter bandwidth (hereinafter referred to as the previous detection value). ) V ′ is compared with the adjacent detection voltage (hereinafter referred to as the current detection value) V detected in the immediately preceding step S111 (step S113), and it is determined whether or not the current detection value V is equal to or lower than the previous detection value V ′. Judgment is made (step S114).
[0028]
If it is determined in step S114 that the current detection value V is not less than or equal to the previous detection value V ′, that is, the current detection value V is greater than the previous detection value V ′, the microcontroller 108 sets the IF filter bandwidth to the current detection value V ′. (Step S115), the value of the counter variable n is set to 1 (step S120), and the adjacent disturbance detection circuit 109 is again detected for a certain period of time (step S111).
[0029]
If it is determined in step S112 that no adjacent interference has been received for a certain period of time, or if it is determined in step S114 that the current detection value V is less than or equal to the previous detection value V ′, the microcontroller 108 uses the IF filter bandwidth. It is determined whether or not the width is the maximum (step S116). If it is determined in step S116 that the IF filter bandwidth is widest at the maximum, the microcontroller 108 sets the value of the counter variable n to 1 (step S120), and again causes the adjacent disturbance detection circuit 109 to adjust the adjacent disturbance strength for a certain period of time. Is detected (step S111). If it is determined in step S116 that the IF filter bandwidth is not widest at the maximum, the microcontroller 108 determines whether or not the value of the counter variable n is a predetermined integer N (step S117).
[0030]
When it is determined in step S117 that the value of the counter variable n is not the predetermined integer N, 1 is added to the value of the counter variable n (step S118), and the adjacent disturbance detection circuit 109 is again subjected to the strength of the adjacent disturbance for a certain time. Is detected (step S111).
[0031]
If it is determined in step S117 that the value of the counter variable n is a predetermined integer N, the IF filter bandwidth is increased by one level (step S119), and the microcontroller 108 sets the value of the counter variable n to 1 ( In step S120), the adjacent disturbance detection circuit 109 is again detected for a certain period of time (step S111).
[0032]
As described above, when the FM receiver 100 receives a radio wave transmitted by a specific broadcast station, that is, a desired broadcast station, the radio wave transmitted by another broadcast station, that is, a broadcast station other than the desired broadcast station. To prevent interference.
[0033]
In the present embodiment, the IF filter bandwidth can be taken in five stages. However, according to the present invention, if the IF filter bandwidth can be taken in three stages or more, There may be any number of stages. Further, the IF filter bandwidth may be two stages of wide and narrow.
[Second Embodiment]
[0034]
A receiving apparatus according to the second embodiment of the present invention will be described with reference to FIGS. 4 and 5.
[0035]
As shown in FIG. 4, the configuration of the receiving apparatus according to the present embodiment is substantially the same as the configuration of the receiving apparatus according to the first embodiment shown in FIG.
[0036]
In the FM receiver 130, the microcontroller 131 divides the signal level into a plurality of regions according to the signal level value, and selects one of the IF filter bandwidths of the five stages of IF filter bandwidths according to the divided regions. When the IF filter bandwidth to which the signal level detected by the adjacent interference detection circuit 109 is made to correspond is narrower than the actual IF filter bandwidth, the actual IF filter bandwidth is set to correspond to the bandwidth. The IF filter bandwidth corresponding to the signal level detected by the adjacent interference detection circuit 109 is changed.
[0037]
Further, in the FM receiver 130, the microcontroller 131 uses the adjacent interference detection circuit when the IF filter bandwidth to which the signal level detected by the adjacent interference detection circuit 109 corresponds is equal to the actual IF filter bandwidth. When the IF filter bandwidth to which the signal level detected by 109 is associated is wider than the actual IF filter bandwidth for a period shorter than a predetermined time, the actual IF filter bandwidth is prevented from being changed. If the IF filter bandwidth to which the signal level detected by the adjacent interference detection circuit 109 is made to correspond is larger than the actual IF filter bandwidth for a predetermined time, the actual IF filter bandwidth is It is designed to change to a wide IF filter bandwidth.
[0038]
Hereinafter, the operation of the receiving apparatus according to the present embodiment will be described with reference to FIGS. 4 and 5.
[0039]
As shown in FIG. 5, when receiving the FM broadcast, the microcontroller 131 causes the adjacent disturbance detection circuit 109 to detect the strength of the adjacent disturbance for a certain time (step S151), and detects the adjacent disturbance for the certain time. It is determined whether it has been received (step S152).
[0040]
If it is determined in step S152 that the adjacent disturbance has been received for a certain time, the microcontroller 131 compares the previous detection value V ′ with the current detection value V (step S153), and the current detection value V is the previous detection value. It is determined whether it is less than V ′ (step S154).
[0041]
If it is determined in step S154 that the current detection value V is not less than the previous detection value V ′, the microcontroller 131 determines whether or not the current detection value V is equal to the previous detection value V ′ (step S155). If it is determined in step S155 that the current detection value V is equal to the previous detection value V ′, the microcontroller 131 sets the value of the counter variable n to 1 (step S161) and again adjoins the adjacent disturbance detection circuit 109 for a fixed time. The level of interference is detected (step S151). If it is determined in step S155 that the current detection value V is not equal to the previous detection value V ′, that is, the current detection value V is greater than the previous detection value V ′, the microcontroller 131 sets the IF filter bandwidth to the current detection value V. Accordingly, the value is reduced (step S156), the value of the counter variable n is set to 1 (step S161), and the adjacent disturbance detection circuit 109 is again detected for a certain period of time (step S151).
[0042]
If it is determined in step S152 that no adjacent interference has been received for a certain period of time, or if it is determined in step S154 that the current detection value V is less than the previous detection value V ′, the microcontroller 131 It is determined whether or not the width is the maximum (step S157). If it is determined in step S157 that the IF filter bandwidth is the largest, the microcontroller 131 sets the value of the counter variable n to 1 (step S161), and again causes the adjacent disturbance detection circuit 109 to adjust the adjacent interference strength for a certain period of time. Is detected (step S151). If it is determined in step S157 that the IF filter bandwidth is not widest at the maximum, the microcontroller 131 determines whether the value of the counter variable n is a predetermined integer N (step S158).
[0043]
If it is determined in step S158 that the value of the counter variable n is not the predetermined integer N, 1 is added to the value of the counter variable n (step S159), and the adjacent disturbance detection circuit 109 is again subjected to the strength of the adjacent disturbance for a fixed time. Is detected (step S151).
[0044]
If it is determined in step S158 that the value of the counter variable n is a predetermined integer N, the IF filter bandwidth is increased by one step (step S160), and the microcontroller 131 sets the value of the counter variable n to 1 ( In step S161), the adjacent disturbance detection circuit 109 is again made to detect the strength of the adjacent disturbance for a predetermined time (step S151).
[0045]
As described above, when the FM receiver 130 receives a radio wave transmitted by a specific broadcast station, that is, a desired broadcast station, the radio wave transmitted by another broadcast station, that is, a broadcast station other than the desired broadcast station. To prevent interference.
[0046]
In the present embodiment, the IF filter bandwidth can be taken in five stages. However, according to the present invention, if the IF filter bandwidth can be taken in three stages or more, There may be any number of stages. Further, the IF filter bandwidth may be two stages of wide and narrow.
[0047]
【The invention's effect】
As described above, according to the present invention, since the receiving apparatus of the present invention can be changed not only according to the presence or absence of adjacent interference but also according to the signal level detected by the signal level detecting means, the electric field greatly fluctuates. In addition, it is possible to avoid a sense of incongruity and noise due to frequent IF filter bandwidth changes in an unstable state where the adjacent interference is received or not received.
[Brief description of the drawings]
1 is a block diagram of a receiving apparatus according to a first embodiment of the present invention. FIG. 2 is a flowchart for explaining the operation of the receiving apparatus shown in FIG. 1. FIG. 3 is an adjacent detection voltage of the receiving apparatus shown in FIG. FIG. 4 is a block diagram of a receiving apparatus according to a second embodiment of the present invention. FIG. 5 is a flowchart for explaining the operation of the receiving apparatus shown in FIG. FIG. 7 is a block diagram of a conventional receiving apparatus. FIG. 7 is a flowchart for explaining the operation of the receiving apparatus shown in FIG.
100, 130 FM receiver (receiver)
101 Receiving antenna (frequency conversion means)
102 Tuning circuit (frequency conversion means)
103 mixer circuit (frequency conversion means)
104 Filter circuit (band filter)
108, 131 Microcontroller (Bandwidth changing means)
109 Adjacent interference detection circuit (signal level detection means)

Claims (2)

Among a plurality of broadcast stations that convert signals to different radio waves and transmit the signals, when the radio waves transmitted by one broadcast station are received, the other broadcast stations transmit among the plurality of broadcast stations In a receiver that prevents interference from radio waves,
A frequency converting means for receiving the radio wave and generating an intermediate frequency signal from the received radio wave by converting the frequency of the radio wave transmitted by the one broadcasting station to the intermediate frequency among the received radio waves;
Of the intermediate frequency signal generated by the frequency conversion means, a bandpass filter that passes the intermediate frequency signal having a frequency bandwidth centered on the intermediate frequency;
Signal level detection means for detecting a signal level of the intermediate frequency signal corresponding to the radio wave transmitted by the other broadcasting station among the intermediate frequency signal passing through the band filter,
A comparison / counting unit that compares the current signal level detected by the signal level detection unit with a previous signal level and counts the number n of times that the current signal level is small;
When the number n counted by the comparison / counting means reaches a predetermined integer N (N is an integer of 2 or more), bandwidth changing means for widening the frequency bandwidth of the bandpass filter;
A receiving apparatus comprising: The pre-SL signal levels, and divided into a plurality of regions according to the value of the signal level, one of the frequency bandwidth of the frequency bandwidth change in the bandwidth changing means in accordance with the classification the said region and Make it correspond,
When the comparison / counting unit obtains a comparison result that the current signal level is large, the bandwidth changing unit changes the frequency bandwidth of the bandpass filter to the frequency bandwidth to which the signal level corresponds. When the number n counted by the comparison / counting means reaches a predetermined integer N (N is an integer of 2 or more), the frequency bandwidth of the bandpass filter is changed to a frequency bandwidth wider by one step. The receiving apparatus according to claim 1.

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