JPH0210681Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a radio receiver, and in particular, an intermediate filter having at least two different frequency bands is provided between a tuner section and an intermediate frequency amplifier, and an intermediate filter having at least two different frequency bands is provided between a receiving station and an adjacent interference. The present invention relates to a radio receiver that automatically selects a predetermined intermediate filter based on the reception level of a station and inputs the output of a tuner section to an intermediate frequency amplifier via the selected intermediate filter.

<Prior art> There are radio receivers that have only either a wideband filter or a narrowband filter installed between the tuner section and the intermediate frequency amplifier, but radio receivers that only have a wideband filter cannot receive signals when there is a fairly large station nearby. This causes interference, and in radio receivers with only a narrow band filter, distortion and separation deterioration occur during overmodulation. For this reason, an intermediate filter (referred to as a 1F filter) having at least two different frequency bands is provided between the tuner section and the intermediate frequency amplifier,
Broadband when there is no interference from neighboring stations.
Use an IF filter to receive good sound quality with little distortion, and when there is interference from adjacent stations, use a narrowband IF filter to receive interference-free reception even if the sound quality is slightly sacrificed. A radio receiver with an automatic intermediate frequency band switching function has been proposed.

<Disadvantages of the prior art> However, in conventional radio receivers with an automatic intermediate frequency band switching function, a circuit for detecting the level of an interfering signal and a discriminating circuit for determining the presence or absence of interference and the degree of interference are required for each adjacent station, which increases the cost. It is the cause of high

In addition, a detection circuit is connected to each IF filter provided between the tuner section and the intermediate frequency amplifier,
A radio receiver with an automatic intermediate frequency band switching function has also been proposed, which determines the presence or absence of interference by comparing the levels of a desired signal and an interfering signal by comparing the output levels of each detection circuit. However, such radio receivers cannot accurately determine the presence or absence of interference;
Since the configuration extracts the levels of the desired signal and interfering signal through an IF filter, the characteristics of the IF filter are limited, and furthermore, the more IF filters there are, the more complex the configuration of the level comparison circuit in the subsequent stage becomes. There are drawbacks.

<Purpose of the invention> The purpose of the invention is to provide a radio receiver with a simple configuration and an automatic intermediate frequency band switching function that eliminates the need to provide a level detection circuit or discrimination circuit for detecting the level of interfering signals for each adjacent station. It is to be.

Another object of the present invention is to provide a radio receiver with an intermediate frequency band automatic switching function that can accurately compare the levels of a desired signal and an interfering signal, and has a simple configuration even when the number of IF filters is large. It is.

Still another object of the present invention is to be able to detect the received level of the interfering signal from an adjacent interfering station without affecting the reception of the desired signal in any way, and to prevent sound interruptions and abnormal noises caused by detecting the received level. An object of the present invention is to provide a radio receiver with an automatic intermediate frequency band switching function.

<Summary of the invention> The radio receiver of the invention includes a first tuner section, a first intermediate frequency amplifier, and different frequency bands disposed between the first tuner section and the first intermediate frequency amplifier. a switching circuit for inputting the output of the first tuner section to the first intermediate frequency amplifier via a predetermined intermediate frequency filter; The first oscillation at a frequency corresponding to the frequency
a phase-locked loop, a second tuner section, a level detection circuit that detects the output level of the second tuner section, and a second tuner section that causes the local oscillator of the second tuner section to oscillate at a predetermined frequency. A phase-locked loop and a first phase-locked loop are controlled to cause the first tuner section to receive and output a desired signal from a desired station, and a second phase-locked loop is controlled to cause the second tuner section to receive and output a desired signal from a desired station. cause the unit to receive and output at least a jamming signal from a jamming station,
The reception level of the interference signal is obtained from the level detection circuit, and the switching circuit is operated based on the levels of the desired signal and the interference signal to send the output of the first tuner section to the first intermediate frequency amplifier via a predetermined intermediate filter. It has a controller that applies the voltage. This invention has a simple configuration, and since it is possible to accurately compare the levels of the desired signal and the interfering signal, it is possible to correctly select a predetermined intermediate frequency filter, and furthermore, even if the number of intermediate frequency filters is large, the configuration does not need to be complicated. It will never become. Further, when detecting the reception level of an adjacent interfering station, the audio of the desired station will not be interrupted or any abnormal noise will be generated.

<Example> As shown in Figure 2, the frequency of the desired station is ₀ , and the frequencies of the adjacent interfering stations _{are 1} (= ₀ - Δ) and ₂ , respectively.
(= ₀ + Δ), the reception level of each frequency is La, Lb,
If Lc is the following equations (k ₁ is a constant), La>k ₁・Lb …(1) La>k ₁・Lc …(2) When the following formulas hold true, in other words, the level of the desired signal is interfered with. When K is greater than ₁ times the signal level, there is no interference from the adjacent interfering station, and when at least one of equations (1) and (2) does not hold, interference from the adjacent interfering station occurs. Therefore, the present invention (a) detects the level of the interfering signal from the adjacent interfering station within a short time while receiving the desired signal, and (b) uses the levels of the desired signal and interfering signal to detect (1). Determine whether equation (2) holds true, and (c) if both equations (1) and (2) hold true, input the tuner output to an intermediate frequency amplifier via a wideband IF filter, and ( If at least one of equations 1) and (2) does not hold true, the tuner output is set to narrowband.
The intermediate frequency band is automatically switched by inputting the signal to the intermediate frequency amplifier via the IF filter.

Fig. 1 is a block diagram of the main parts of the radio receiver according to the present invention, Fig. 3 is a time chart for detecting the levels of desired signals and interfering signals, and Fig. 4 is a flowchart of processing for automatic intermediate frequency band switching according to the present invention. It is.

In FIG. 1, 11 is a first tuner section;
2 is a first intermediate frequency amplifier; 13a and 13b are IF filters disposed between the first tuner section 11 and the first intermediate frequency amplifier 12;
has a wideband IF filter, 13b has a narrowband IF filter, 14 has switches 14a and 14b,
PLLP1 is a switching circuit that inputs the output signal of the first tuner section 11 to the first intermediate frequency amplifier 12 via a predetermined IF filter.
a first phase-locked loop that causes a local oscillator to oscillate at a frequency corresponding to the frequency of the desired station;
15 is a second tuner section; 16 is a level detection circuit that detects the output level of the second tuner section;
PLLP2 is a second phase-locked loop that causes the local oscillator of the second tuner section 15 to oscillate at a predetermined frequency, and 17 is a controller.

The first and second tuner sections 11 and 15 respectively include high frequency amplification circuits 11a and 15a and local oscillators 11b and 1 which amplify input signals from the antenna AT.
5b, mixers 11c, 15c, etc., and the level detection circuit 16 includes a narrow band filter 16a,
Second intermediate frequency amplifier 16b and detector 16c
and an AD converter 16d, the intermediate frequency signal taken out from the second intermediate frequency amplifier 16b is detected by the detector 16c, and the detected output is AD converted by the AD converter 16d and output. The first phase-locked loop PLLP1 is composed of a local oscillator 11b of the first tuner section, a PLL circuit 18, and a low-pass filter 19, so that the oscillation frequency of the local oscillator 11b is always higher than the frequency ₀ of the desired station by the intermediate frequency. Control. That is, the first phase-locked loop PLLP1 controls the oscillation frequency of the local oscillator 11b based on the first reception frequency control data FCD1 corresponding to the desired frequency that the controller 17 commands the PLL circuit 18,
The oscillation frequency is controlled so that it is always higher than the frequency ₀ of the desired station by the intermediate frequency. The second phase-locked loop PLLP2 is composed of a local oscillator 15b of the second tuner section, a PLL circuit 20, and a low-pass filter 21.
The second reception frequency control data commanding the
Control the frequency according to FCD ₂ .

The controller 17 is always connected to the first tuner section 11
transmits the first reception frequency control data FCD ₁ so that it receives and outputs the desired signal (frequency ₀ ) from the desired station.
At the same time as commanding the PLL circuit 18, the desired signal (frequency ₀ ) from the desired station and the first and second interference signals (frequency ₁ , ₂ ) from the adjacent interfering stations are sent to the second tuner at the timing shown in FIG. The second reception frequency control data FCD ₂ is received and outputted by the section 15.
is commanded to the PLL circuit 20. That is, the controller 17 sequentially performs predetermined signals so that the desired signal is received and outputted by the _second tuner unit 15 during the period T ₁ shown in FIG. The second received frequency control data FCD ₂ is commanded to the PLL circuit 20.

The level detection circuit 16 detects the reception level La of the desired signal (frequency ₀ ) during T ₁ , and detects the reception level Lb or Lc of the first or second interference signal (frequency ₁ or frequency ₂ ) during T ₂ . However, each digital value is read by the controller 17 and stored in the built-in memory 17a.

Next, the operation shown in FIG. 1 will be explained with reference to the flowchart shown in FIG.

(a) When a channel selection switch (not shown) is pressed to select a channel, the controller 17 reads the channel selection information.

(b) The controller 17 transmits the desired signal from the selected station based on the channel selection information to the first tuner unit 11.
Predetermined first reception frequency control data FCD ₁ is applied to the PLL circuit 18 in order to receive the data.
As a result, the first tuner section 11 will continue to receive the desired signal from then on.

(c) Next, the controller 17 transmits the desired signal to the second tuner section 1 during the period _T1 (see FIG. 3).
5, input the predetermined second reception frequency control data FCD ₂ to the PLL circuit 20 to receive and output, read the output (reception level La) of the level detection circuit 16 at that time, and read the output (reception level La) from the built-in memory 17a.
to be memorized. Note that since the controller 17 stores in advance the correspondence between the channel selection switch and the received frequency control data in its built-in memory, it determines the reception frequency control data corresponding to the operated channel selection switch from the correspondence and calculates this data. PLL circuits 18 and 2 as the first and second receiving frequency control data.
Output to 0.

(d) Then, during period T ₂ after period T ₁ has elapsed, the controller 17 sets the second tuner unit 15 to receive and output the first interference signal (frequency ₁ ) from the first adjacent interference station. 1. Second receiving frequency control data FCD ₂ corresponding to adjacent interfering station is sent to PLL circuit 2
0, and the output (reception level Lb) of the level detection circuit 16 at that time is read and stored in the built-in memory 17a.

(e) After the controller 17 detects the reception level Lb,
Determine whether formula (1) holds true. If equation (1) does not hold, then the controller 17 switches the switching circuit 1 to
The switching signal CS is input to step 4 to select the narrow band IF filter 13b, and the processing from step c onwards is repeated. As described above, the output terminal of the first tuner section 11 is connected to the input terminal of the intermediate frequency amplifier 12 via the narrow band IF filter 13b.

On the other hand, if the equation (1) holds true, there is no interference caused by the first adjacent interfering station, so it is checked by the following process whether interference is occurring due to the second adjacent interfering station.

(f) During the next T ₁ , the controller 17 transmits predetermined second frequency control data FCD ₂ in order to cause the second tuner section 15 to receive and output the desired signal.
is input to the PLL circuit 20, and the output (reception level La) of the level detection circuit 16 at that time is read and stored in the built-in memory 17a.

(g) Then, during the period T ₂ after T ₁ has elapsed, the controller 17 transmits the interference signal (frequency
₂ ) by the second tuner unit 15, a predetermined second signal is set according to the second adjacent interfering station.
The received frequency control data FCD ₂ is sent to the PLL circuit 20
The output of the level detection circuit 16 at that time (reception level Lc) is read and stored in the built-in memory 17.
Store in a.

(h) After detecting Lc, the controller 17 determines whether equation (2) holds. If equation (2) does not hold, then interference is occurring due to the second adjacent interfering station, so the controller 17 inputs the switching signal CS to the switching circuit 14 to select the narrowband IF filter 13b, and then steps c. Repeat the following process.

(i) If equation (2) holds true, there is no interference from the second adjacent interfering station, so the controller 17 inputs the switching signal CS to the switching circuit 14, and the broadband IF
The filter 13a is selected, and the processing from step c onwards can be repeated. By the process of step i, the output terminal of the first tuner section 11 is connected to the input terminal of the first intermediate frequency amplifier 12 via the wideband IF filter 13a.

In addition, in the above, different frequency bands are used.
Although the case where two IF filters are used has been described, the present invention is not limited to two, and can be configured to include three or more. In this case, multiple discriminants with different magnitudes of the constant k ₁ in equations (1) and (2) are prepared, and a predetermined IF filter is selected depending on whether each discriminant is true or not. do.

Further, although the configuration of the switching circuit 14 has not been described in detail, each switch 14a, 14b is constituted by an electronic switch such as a switching transistor or a diode. In addition, in FIG. 1, the switching circuit 14 is connected to two switches 14a, 14.
Although shown in b, for example, the switch 14a may be removed and the input terminals of each IF filter 13a, 13b may be connected to the output terminal of the first tuner section.

Furthermore, in the above explanation, one controller 1
In this case, two controllers are provided, and the first tuner section executes PLL synthesis processing to cause the first tuner section to receive the frequency signal of the station selected by the first controller. It is also possible to configure the second controller to perform signal level detection processing of the desired station and adjacent interfering stations, automatic intermediate frequency band switching processing, and the like.

<Effects of the Invention> As explained above, according to the present invention, in addition to the first tuner section that receives and outputs the desired signal, there is a second tuner section that detects the signal levels from the desired station and the adjacent interfering station. and a level detection circuit are provided, and the IF filter is selected based on the reception levels of the desired signal and interference signal obtained from the second tuner section, so that there is no influence on the reception of the desired signal by the first tuner section. The reception level of each station can be detected without any input, and good reception can be achieved without the audio of the desired station being cut off or abnormal noise being added due to the reception level detection operation.

Further, according to the present invention, a controller for controlling the tuning frequency of the second tuner section and a level detection circuit are provided, and the controller causes the second tuner section to detect the desired signal and the interference of the first and second adjacent interfering stations. The signal is received, the received level of the desired signal and the interference signal detected by the level detection circuit are compared and judged by the controller, and a predetermined signal is detected based on the judgment result.
Since the configuration is configured to select the IF filter, there is no need to provide a detection circuit or discrimination circuit for detecting the interfering signal level for each adjacent station, and the configuration can be simplified.
Moreover, since the levels of the desired signal and the interfering signal can be accurately compared, a predetermined IF filter can be selected correctly, and furthermore, even if the number of IF filters increases, the configuration does not become complicated.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the main parts of a radio receiver according to the present invention, Fig. 2 is an explanatory diagram illustrating the presence or absence of interference,
FIG. 3 is a time chart for detecting the reception levels of the desired signal and the interfering signal, and FIG. 4 is a flowchart of the intermediate frequency band switching process according to the present invention. 11...first tuner section, 12...first intermediate frequency amplifier, 13a...wideband IF filter,
13b...Narrowband IF filter, 14...Switching circuit, 15...Second tuner section, 16...Level detection circuit, 17...Controller, PLLP1,
PLLP2...The first and second phase lock loops.

Claims (1)

[Scope of utility model registration request] a first tuner section, a first intermediate frequency amplifier, at least two intermediate frequency filters having different frequency bands disposed between the first tuner section and the first intermediate frequency amplifier; A switching circuit inputs the output of the tuner section to the first intermediate frequency amplifier via a predetermined intermediate frequency filter, and a first filter that causes the local oscillator of the first tuner section to oscillate at a frequency corresponding to the frequency of the desired station. an aerated locked loop, a second tuner section, a level detection circuit for detecting an output level of the second tuner section, and a second tuner section;
A second phase-locked loop that causes the local oscillator of the tuner section to oscillate at a predetermined frequency, and a first phase-locked loop that receives and outputs a desired signal from a desired station to the first tuner section. At the same time, the second phase-locked loop is controlled to cause the second tuner section to receive and output at least the interfering signal from the interfering station, and the reception level of the interfering signal is obtained from the level detection circuit, and the desired signal and interfering signal are detected. Based on the level of
A radio receiver characterized in that it has a controller that applies voltage to an intermediate frequency amplifier.