JP2012191266A - Receiver and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reception quality deterioration due to a disturbing wave of an adjacent channel.SOLUTION: In a receiver 1 in which frequency conversion from RF to IF is performed by allowing a frequency conversion section 12 to mix an RF signal amplified by an RF amplifier 11 and a local frequency generated by a local oscillator 13, band property of an analog filter 14 is temporarily switched to wide band property, and it is detected whether an adjacent channel is mixed as a disturbing wave on the basis of a signal power difference before and after filtering by a digital filter 22. When the disturbing wave of the adjacent channel is detected, the local frequency generated by the local oscillator 13 is switched from upper local to lower local or from lower local to upper local. This prevents the adjacent channel from becoming an image frequency, thereby removing image disturbance due to the adjacent channel.

Description

  The present invention relates to a receiving apparatus and a program, and more particularly to a receiving apparatus and a program suitable for receiving digital broadcasts.

  In a receiving apparatus used for receiving digital broadcasting or the like, an RF circuit unit (for example, an RF tuner circuit (for example, an RF tuner circuit)) converts a received RF (Radio Frequency) signal to an intermediate frequency (IF) that is a demodulation frequency. Analog) etc.) at the front stage, and demodulation circuit units (for example, OFDM (Orthogonal Frequency Division Multiplexing) demodulation circuit (digital), etc.) that convert the frequency converted IF signal into a digital signal and demodulate it at the back stage In general, the above configuration is adopted.

  Such a receiving apparatus is generally used as a portable broadcast receiving apparatus by being incorporated in a mobile communication terminal such as a mobile phone. In the case of a portable receiving device, the reception state of a channel desired to be received (desired channel) is not always good due to changes in the surrounding environment accompanying carrying. For example, the desired channel may have a weak electric field due to the influence of multipath, and the signal power of the adjacent channel may be higher than the signal power of the desired channel. Such a signal of the adjacent channel becomes a disturbing wave, and the reception quality for receiving the desired channel is deteriorated.

  In particular, when the adjacent channel becomes an interference wave, it may be a factor of third-order distortion, and the interference component may increase abruptly, resulting in a significant decrease in reception quality. For this reason, it is desirable to effectively remove the interference wave caused by the adjacent channel.

  As a method for removing the interference wave, it is conceivable to use a filter in the RF circuit section. In order to remove the interference component of the adjacent channel, it is necessary to make the band characteristics wider than the band covering one channel. However, the role of the filter of the RF circuit section is to select the channel by filtering the received signal to the desired channel, so that the tuning accuracy is lowered if the filter has a wideband characteristic.

  In the RF circuit section, a so-called superheterodyne method is generally used in which frequency conversion is performed by multiplying a reception frequency (RF) by a local frequency. In such frequency conversion, the local frequency is determined from the frequency (RF) of the selected desired channel and the required frequency (IF) of the demodulation circuit unit. For example, when the frequency difference between the RF of the desired channel and the required IF is f, a frequency 2f away from the local frequency that is symmetric with respect to the local frequency is a frequency that is converted into the required IF together with the RF, so-called image frequency. Here, when the desired channel becomes a weak electric field due to changes in the surrounding environment, etc., the frequency of the adjacent channel tends to become the image frequency, and the adjacent channel becomes an interference wave, resulting in a reduction in reception quality such as image interference. That is, the interference wave of the adjacent channel is likely to be manifested as image interference.

  In this case, so-called image rejection (image removal) is known in which image interference is removed by switching a local frequency multiplied by RF during frequency conversion (for example, Patent Document 1). That is, when image interference occurs at a certain local frequency (for example, upper local), the frequency of the adjacent channel is changed from the image frequency by switching to another frequency (for example, lower local) within the frequency band that can be taken as the local frequency. Displacement and image interference can be eliminated.

  However, since the operation for switching the local frequency is an operation close to reset, reception is interrupted during the switching. In the case of a portable receiver that is expected to change in the surrounding environment, the reception quality will also change frequently according to the change in the reception environment. Is inconvenient.

JP 2009-206812 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a receiving apparatus and a program that can effectively improve a reduction in reception quality due to an interference wave of an adjacent channel.

In order to achieve the above object, a receiving apparatus according to the first aspect of the present invention provides:
A local frequency oscillator for generating a local frequency;
A frequency converter that performs frequency conversion by mixing the received signal and the local frequency;
A first filter for filtering the signal frequency-converted by the frequency converter;
Band switching for switching the characteristic of the first filter from the first band characteristic covering the frequency band of the desired channel to the second band characteristic covering the frequency band including a part of the desired channel and the adjacent channel. Means,
An interference wave detecting means for detecting an interference wave due to an adjacent channel by switching the characteristics of the first filter by the band switching means;
Reception quality improvement means for improving reception quality by image removal when the interference wave detection means detects an interference wave due to an adjacent channel;
It is characterized by that.

  ADVANTAGE OF THE INVENTION According to this invention, the receiver which can improve effectively the fall of the reception quality by the interference wave of an adjacent channel is realizable.

It is a block diagram which shows the structure of the receiver concerning Embodiment 1 of this invention. FIG. 2 is a diagram for explaining the characteristics of the analog filter shown in FIG. 1, where (a) shows normal filter characteristics and (b) shows broadband characteristics. It is a functional block diagram which shows the function implement | achieved by the demodulation part shown in FIG. It is a flowchart for demonstrating the "reception process" concerning embodiment of this invention. It is a figure for demonstrating frequency conversion, (a) shows the relationship of the desired channel, adjacent channel, and local frequency when an interference wave is detected, (b) shows an adjacent channel image disturbance by frequency conversion. It shows that. It is a figure for demonstrating the local frequency switching concerning embodiment of this invention, (a) shows the case where a local frequency is switched from upper local to lower local, (b) shows only a desired channel by local frequency switching. Indicates frequency conversion.

  Embodiments according to the present invention will be described below with reference to the drawings.

  A receiving apparatus 1 according to a first embodiment of the present invention will be described with reference to FIG. Here, a case where the receiving apparatus according to the present invention is configured as a receiving apparatus for use in receiving digital broadcasting such as terrestrial digital broadcasting will be described as an example. FIG. 1 is a block diagram illustrating a configuration of a receiving device 1 according to the first embodiment.

  As shown in the figure, a receiving apparatus 1 according to the present embodiment receives a broadcast wave that is a radio frequency (RF) and converts it to an RF circuit unit 10 that converts it to an intermediate frequency (IF). And a demodulation circuit unit 20 that demodulates the IF signal to obtain a broadcast content reproduction signal.

  As shown in FIG. 1, the RF circuit unit 10 includes an RF amplifier 11, a frequency converter 12, a local oscillator 13, an analog filter 14, an IF amplifier 15, and the like.

  The RF amplifier 11 is an amplifier (first amplifier) that amplifies a broadcast radio wave reception signal (RF) received by an antenna (not shown) or the like, and in this embodiment, a variable gain capable of gain (gain) control. It shall be an amplifier (VGA: Variable Gain Amplifier).

  The frequency conversion unit 12 is composed of, for example, a mixer circuit such as an analog multiplier, and mixes the frequency of the signal amplified by the RF amplifier 11 with the local frequency from the local oscillator 13. The output frequency of the amplifier 11 is converted from the RF band to the subsequent frequency band. In the present embodiment, frequency conversion to an intermediate frequency (IF) band that is a frequency (demodulation frequency) required by the demodulation operation of the demodulation circuit unit 20 is performed.

  The analog filter 14 is an analog filter such as a low-pass filter (LPF), for example, and attenuates unnecessary waves by filtering the IF output signal of the frequency converter 12. In the present embodiment, the control signal (CTRL_FL) from the demodulator 200 is sent to the analog filter 14 via the RF controller 24. In the present embodiment, a filter capable of changing the band characteristics is used as the analog filter 14. In this case, it is assumed that the filter can change the frequency band to be filtered.

  In the present embodiment, for example, as shown in FIG. 2A, a filter having a characteristic that covers a band of one desired channel (hereinafter referred to as “normal filter”), and FIG. 2B. It is assumed that a filter having a wideband characteristic (hereinafter referred to as a “wideband filter”) covering a band including one channel of a desired channel and a part of an adjacent channel is provided.

  The IF amplifier 15 is an amplifier (second amplifier) configured by, for example, the same VGA (variable gain amplifier) as the RF amplifier 11, amplifies the signal filtered by the analog filter 14, and supplies the demodulator 200. Output.

  As shown in FIG. 1, the demodulation circuit unit 20 includes an ADC 21, a digital filter 22, a storage unit 23, an RF control unit 24, a demodulation unit 200, and the like.

  The ADC 21 is an analog-digital converter (ADC), converts an analog signal in the IF band amplified by the IF amplifier 15 into a digital signal, and uses the digital signal for demodulation.

  The digital filter 22 is a digital filter that filters (filters) the digital signal converted by the ADC 21 to a desired frequency band (attenuates frequencies other than the desired frequency band). For example, the digital filter 22 may be a digital low-pass filter (DLPF). Composed.

  Since the digital filter 22 is for filtering the IF signal frequency-converted by the RF circuit unit 10 to a desired channel, the band of the digital filter 22 covers one channel of the desired channel. Therefore, the band of the normal filter of the analog filter 14 is substantially the same as the band of the digital filter 22. Therefore, the wide band filter of the analog filter 14 has a wider band characteristic than the band of the digital filter 22.

  The storage unit 23 includes, for example, a register, a ROM (Read Only Memory), or other rewritable storage device, and stores an operation program executed by the demodulation unit 200, data used by the demodulation unit 200, and the like. To do.

  In the present embodiment, for example, there is a table (hereinafter referred to as “local frequency table”) in which channels that can be selected are associated with local frequencies that should be generated by the local oscillator 13 when each channel is selected. Assume that it is stored in the storage unit 23. In this local frequency table, it is assumed that two frequencies corresponding to both ends of the local frequency band where the channel can be selected are recorded as local frequencies. “Upper local” and the lower end frequency are “lower local”.

  The RF control unit 24 controls each unit of the RF circuit unit 10 based on a control signal generated by processing (details will be described later) performed by the demodulation unit 200. In the present embodiment, the local oscillator 13 and the analog filter 14 are mainly controlled by the RF control unit 24. When an analog signal is required for the control, the RF control unit 24 includes a digital-analog converter (DAC), and the digital control signal sent from the digital demodulation unit 200 is converted into an analog signal. Convert to In the generation of such an analog control signal, for example, modulation such as PWM (Pulse Width Modulation) and PCM (Pulse Code Modulation) is performed as necessary.

  The demodulator 200 includes, for example, a digital processor (digital arithmetic circuit) such as a DSP (Digital Signal Processor) or a CPU (Central Processing Unit), and performs processing using a digital signal converted by the ADC 21. To do.

  In the present embodiment, as illustrated in FIG. 3, it is assumed that the output from the ADC 21 and the output from the digital filter 22 are input to the demodulation unit 200. The demodulator 200 implements various functions by executing an operation program recorded in the storage unit 23.

  In the present embodiment, the RF circuit unit 10 is controlled by the process performed by the demodulator 200 to detect the interference wave, and when the interference wave is detected, the reception quality is improved by image rejection. Among the functions realized by the demodulator 200, functions necessary for improving the reception quality will be described below with reference to FIG. FIG. 3 is a functional block diagram showing functions realized by the demodulator 200.

  As shown in the figure, the demodulation unit 200 implements a demodulation function 210, a filter switching function 220, a received power calculation function 230, an interference wave detection function 240, a reception quality improvement function 250, and the like. In the present embodiment, these functions are integratedly realized in a processor such as a DSP or a CPU. However, these functions are performed by dedicated hardware specialized for operations related to the above functions. May be realized.

  The demodulation function 210 demodulates the digital signal filtered to the desired frequency band by the digital filter 22 and outputs a reproduction signal indicating audio or video to a subsequent stage (not shown) related to the reproduction operation.

  The filter switching function 220 switches the band characteristics of the analog filter 14 by sending a control signal to the analog filter 14 via the RF control unit 24. As described above, the analog filter 14 according to the present embodiment includes a filter circuit capable of switching between a normal filter having substantially the same band characteristics as the digital filter 22 and a broadband filter having a band characteristic that is wider than that of the normal filter. Used. Therefore, the filter switching function 220 generates a control signal (CTRL_FL) for switching the band characteristic of the analog filter 14 to the normal filter or the broadband filter, and sends the control signal to the analog filter 14 via the RF control unit 24.

  Here, the switching method of the filter characteristics of the analog filter 14 is arbitrary. For example, when the analog filter 14 is configured by one chip and the band characteristics can be logically changed, the control signal for switching is analog. Send to filter 14 to switch filter characteristics. When two filter circuits having different characteristics are prepared, a control signal for switching is sent to a switch that switches an input to the filter circuit.

  Here, during normal operation, a normal filter as shown in FIG. 2A is used, but when detecting whether there is an interference wave, the filter switching function 220 controls the analog filter 14. The broadband filter as shown in FIG. This wideband filter covers a part of the band of the adjacent channel. Therefore, when the adjacent channel is an interference wave, the power of the adjacent channel band is also passed. Therefore, as shown in FIG. 2B, the component of the adjacent channel is caused by the power difference before and after filtering by the digital filter 22. Can be detected. For this reason, in this embodiment, as shown in FIG. 3, a signal before and after filtering by the digital filter 22 is input to the received power calculation function 230.

  The reception power calculation function 230 calculates the signal power (reception power) of the signal before and after filtering by the digital filter 22 in the digital signal converted by the ADC 21. Here, the power calculation method by the received power calculation function 230 is arbitrary. For example, the signal is converted into power and obtained by average in the section, or the ratio exceeding the threshold is obtained from the amplitude probability density distribution and converted. A known technique such as a method of performing can be used.

  The interference wave detection function 240 controls the detection operation of the interference wave, and based on the measured power by the received power calculation function 230 when the band characteristic of the analog filter 14 is switched to the wideband filter by the filter switching function 220, the desired channel The presence of jamming waves in adjacent channels is detected.

  That is, for a signal that has passed through an analog filter 14 (wideband filter) having a wider bandwidth than that of the digital filter 22, a power difference before and after filtering by the digital filter 22 that is a band characteristic covering one channel of the desired channel is obtained. The interference wave is detected with.

  For example, when the reception target of the receiving apparatus 1 according to the present embodiment is so-called full segment (full segment) broadcasting, the receiving apparatus 1 receives all the frequency bands (all bands) assigned to one channel. In such a full band reception, all the power of the desired channel exists in the desired frequency band, and therefore all the power other than the desired frequency band becomes unnecessary frequency components.

  When the analog filter 14 is a wideband filter, a signal filtered in a band including a part of an adjacent channel is input to the demodulation circuit unit 20, and the digital filter 22 filters such a signal to a desired frequency band. Therefore, the frequency component of the interference wave is mixed in the signal before being filtered by the digital filter 22. Therefore, by comparing such a pre-filtered signal with the post-filtered signal filtered to the desired frequency band by the digital filter 22, the power ratio of the interference wave can be estimated.

  That is, the power difference calculated by the jamming wave detection function 240 indicates the power ratio of such jamming waves. That is, when the ratio of the interference wave power is high, the interference wave or a lot of distortion due to the interference wave is included. In such a case, the power difference calculated by the interference wave detection function 240 becomes large. On the other hand, when the ratio of the interference wave power is low, the power difference calculated by the interference wave detection function 240 is small. Therefore, the interference wave detection function 240 compares the calculated power difference value with a threshold value, and determines that an interference wave exists when the power difference value is larger than the threshold value.

  The reception quality improvement function 250 performs control for improving a decrease in reception quality due to mixing of interference waves when the presence of interference waves is detected by the interference wave detection function 240. That is, when the receiving apparatus 1 is used for digital broadcast reception, a frequency corresponding to a channel adjacent to a desired channel may become an interference wave, and reception quality may be deteriorated by mixing such an interference wave. is there. At that time, the reception quality improvement function 250 performs control for improving the deterioration of the reception quality due to the interference wave.

  Although such an interference wave can be removed by the analog filter 14, in this case, it is necessary to have a wideband characteristic that covers not only the band of the desired channel but also the band of the adjacent channel. The analog filter 14 is used for the purpose of filtering the received signal in the band of the desired channel in order to select the desired channel. Therefore, the analog filter 14 reduces the tuning accuracy if it has wideband characteristics during normal reception operation. End up.

  For this reason, in this embodiment, interference wave removal using the analog filter 14 is not performed, but interference wave removal is performed by image rejection (image removal). In the present embodiment, the interference wave is attenuated by image rejection (image removal) by switching the local frequency of the local oscillator 13. In this case, since the attenuation effect by the image rejection is used instead of the attenuation by the analog filter 14, it is assumed that the attenuation by the image rejection is larger than the attenuation by the analog filter 14 having a wideband characteristic.

  The above is the configuration of the receiving device 1 according to the present embodiment, but each of the above configurations shows the configuration necessary for realizing the present invention, and other configurations necessary for the receiving device are described. It is assumed that it is appropriately provided as necessary.

  An example of the operation of the receiving apparatus 1 configured as described above will be described below. The “reception process” executed by the receiving apparatus 1 according to the first embodiment will be described with reference to the flowchart shown in FIG. This “reception process” is started, for example, when the reception device 1 is activated.

  Along with the start of processing, the receiving operation by the receiving device 1 is started (step S101). Here, the reception operation for the frequency band of the selected channel is performed. That is, the analog filter 14 is set to a filter characteristic (normal filter) that filters the frequency band of the selected channel, and a reception operation is performed.

  In this embodiment, it is assumed that the interference wave detection operation is performed every predetermined period after the reception operation is started. For example, an interference wave detection operation is performed immediately after the start of reception operation or immediately after channel selection, and thereafter, the detection operation is periodically performed every predetermined time. For example, the timing of the detection cycle is defined by the interference wave detection function 240 in cooperation with a timing circuit provided in a digital circuit constituting the demodulator 200.

  When the interference wave detection operation timing comes like this (step S102: Yes), the interference wave detection function 240 instructs the filter switching function 220 to switch the filter. The filter switching function 220 generates a control signal (CTRL_FL) for switching the filter characteristic of the analog filter 14 from the normal filter to the wideband filter in response to an instruction from the interference wave detection function 240, and the analog filter via the RF control unit 24. 14 to send. Thereby, the filter characteristic of the analog filter 14 is switched from the normal filter to the broadband filter (step S103).

  When the switching operation to the wideband filter is performed, the filter switching function 220 notifies the interference wave detection function 240 to that effect. When receiving the notification from the filter switching function 220, the interference wave detection function 240 instructs the reception power calculation function 230 to calculate each of the reception power before and after filtering by the digital filter 22.

  In response to an instruction from the interference wave detection function 240, the reception power calculation function 230 calculates the reception power before filtering by the digital filter 22 and the reception power after filtering by the digital filter 22, respectively. Notify the detection function 240.

  The jamming wave detection function 240 performs a jamming wave detection operation based on the received power before and after filtering by the digital filter 22 notified from the received power calculation function 230 (step S104). Here, it is determined whether or not an interfering wave is mixed based on a difference in received power before and after filtering by the digital filter 22.

  When the interference wave detection operation is performed, the interference wave detection function 240 instructs the filter switching function 220 to switch the filter characteristic of the analog filter 14 from the wideband filter to the normal filter. The filter switching function 220 generates a control signal (CTRL_FL) for switching the filter characteristics of the analog filter 14 from the wideband filter to the normal filter in response to an instruction from the interference wave detection function 240, and the analog filter via the RF control unit 24 14 to send. Thereby, the filter characteristic of the analog filter 14 is switched from the broadband filter to the normal filter. That is, the original filter characteristics are restored (step S105).

  By the operation as described above, the filter characteristic of the analog filter 14 is switched from the normal filter to the broadband filter only when the interference wave detection function 240 performs the interference wave detection operation.

  When the jamming wave detection function 240 detects mixing of jamming waves from the received power before and after filtering by the digital filter 22 (step S106: Yes), the jamming wave detection function 240 notifies the reception quality improvement function 250 to that effect. The reception quality improvement function 250 performs an operation of switching the local frequency of the local oscillator 13 in response to the notification from the interference wave detection function 240 (step S107).

  In this case, the reception quality improvement function 250 first identifies whether the local frequency generated by the local oscillator 13 for the current channel selection is the upper local or the lower local. The reception quality improvement function 250 refers to the local frequency table in the storage unit 23, specifies the corresponding lower local if the current local frequency is upper local, and if the current local frequency is lower local, Identify the corresponding upper local.

  The reception quality improvement function 250 generates a control signal (CTRL_LO) for switching the local frequency generated by the local oscillator 13 to the specified local frequency, and sends the control signal to the local oscillator 13 via the RF control unit 24. As a result, the local frequency generated by the local oscillator 13 is switched (step S107).

  That is, when an interference wave is detected by the interference wave detection function 240, the local frequency generated by the local oscillator 13 is switched. And by image rejection by switching the local frequency, the image interference generated by the adjacent channel as an interference wave is removed, and the reception quality is improved.

  For example, when an interference wave due to an adjacent channel is detected when the local frequency is upper local with respect to the desired channel, the desired channel (N), the local frequency, and the adjacent channel (N + 1) have the relationship shown in FIG. It is thought that. That is, the frequency difference between the desired channel and the local frequency (upper local to the desired channel) and the frequency difference between the adjacent channel and the local frequency (upper local to the desired channel) are both f, and the desired channel and the adjacent channel are local frequencies. When it is symmetric (upper local to the desired channel), that is, when the local frequency becomes a lower local frequency with respect to the adjacent channel, the adjacent channel becomes the image frequency and becomes an interference wave.

  In this case, as shown in FIG. 5B, the desired channel (RF) is frequency-converted to the required IF by the mixing (mixing) of the RF and the local frequency by the frequency converter 12, but it is the image frequency. The adjacent channel is also frequency-converted to the required IF. Here, in a reception environment where the desired channel is a weak electric field, image interference occurs due to the adjacent channel.

  Therefore, as shown in FIG. 6A, when the local frequency is switched from the upper local to the desired channel to the lower local to the desired channel, the desired channel and the adjacent channel are not symmetric with respect to the local frequency. Is no longer the image frequency. If frequency conversion is performed in this state, only the desired channel is frequency-converted to the required IF as shown in FIG. 6B, so that image interference due to the adjacent channel is eliminated (image rejection).

  Therefore, when an interference wave is detected in the interference wave detection operation in step S104 (FIG. 4), the local frequency is switched from upper local to lower local or lower local to upper local for the desired channel. Interference wave removal by rejection is performed, and reception quality can be improved.

  By repeating such an operation until an end event (for example, power-off, etc.) regarding the reception operation of the reception device 1 occurs (step S108: No), the local frequency is only detected when an interfering wave is detected. Switching is performed and reception quality is maintained. Then, when the end event occurs (step S108: Yes), this process ends.

  As described above, by applying the present invention as in the above embodiment, it is possible to improve the degradation of reception quality caused by the adjacent channel becoming an interference wave.

  In the above embodiment, the reception quality is improved by using image rejection by switching the local frequency. However, since the switching of the local frequency is close to the reset operation in the receiving operation, the reception is performed by switching the local frequency. Will be interrupted. For this reason, in the above-described embodiment, the local frequency is switched only when an interference wave due to an adjacent channel is detected, so that reception quality can be improved while minimizing reception interruption.

  When switching the local frequency, the upper end (upper local) and the lower end (lower local) of the frequency band that can be used as the local frequency are switched, making it easy to change the settings related to the local frequency switching. In addition, since the frequency difference in the applicable frequency band is maximized, the image rejection effect can be reliably obtained.

  Further, since the filter characteristic of the IF filter (analog filter 14) is switched to the wideband characteristic only when the interference wave due to the adjacent channel is detected, the interference wave can be detected without always using the wideband filter. The original filter characteristics can be ensured during the receiving operation.

  The said embodiment is an example and the application range of this invention is not restricted to this. That is, various applications are possible, and all embodiments are included in the scope of the present invention.

  For example, in the above embodiment, the frequency converter 12 converts the RF frequency to the IF frequency. However, the converted frequency band may be a base band (BB) band. In this case, the analog filter 14 is configured by a band-pass filter (BPF) instead of the LPF, the IF amplifier 15 is configured by BBVGA (Base Band VGA) instead of the IFVGA, and the DBPF (DBPF ( The digital filter 22 may be constituted by a digital BPF).

  In the above embodiment, each function related to the improvement of reception quality is realized by the demodulator 200. However, the demodulator 200 is configured to be realized by a digital circuit (processor) independent of the circuit responsible for the demodulation function. May be.

  Moreover, although the case where the interference wave detection operation is performed at a periodic timing is illustrated in the above embodiment, the execution timing of the interference wave detection is arbitrary and is not limited to the above-described example.

  For example, since the deterioration of reception quality due to interference waves may be improved by gain control (so-called AGC (Automatic Gain Control)), the local frequency is switched when it cannot be improved by gain control. May operate as follows. In this case, the interference wave detection operation is performed after gain control is performed, and the local frequency is switched when the interference wave of the adjacent channel is detected. At this time, a threshold value may be set for gain increase / decrease by gain control, and a condition for executing the interference wave detection operation may be provided.

  Alternatively, the reception quality may be detected as needed by monitoring various parameters, and the interference wave detection operation may be performed when a decrease in reception quality is detected.

  Note that the present invention can be realized by a receiving apparatus having the same functions and configurations as those of the receiving apparatus 1 of the above-described embodiment, and by applying a program to a digital circuit of an existing receiving apparatus, the receiving according to the present invention can be performed. It can also function as a device. In this case, by causing a computer (such as a CPU) similar to the demodulation unit 200 exemplified in the above embodiment to execute a program for realizing the same function as the above-described function, the computer functions as the receiving device according to the present invention. be able to.

  The application method of such a program is arbitrary. For example, the program can be applied by being stored in a storage medium such as a CD-ROM or a memory card, or can be applied via a communication medium such as the Internet.

  As mentioned above, although some embodiment of this invention was described, embodiment which can apply this invention is contained in the invention described in the claim, and its equality range. The invention described in the scope of claims at the beginning of the filing of the present application will be appended.

(Appendix 1)
A local frequency oscillator for generating a local frequency;
A frequency converter that performs frequency conversion by mixing the received signal and the local frequency;
A first filter for filtering the signal frequency-converted by the frequency converter;
Band switching for switching the characteristic of the first filter from the first band characteristic covering the frequency band of the desired channel to the second band characteristic covering the frequency band including a part of the desired channel and the adjacent channel. Means,
An interference wave detecting means for detecting an interference wave due to an adjacent channel by switching the characteristics of the first filter by the band switching means;
Reception quality improvement means for improving reception quality by image removal when the interference wave detection means detects an interference wave due to an adjacent channel;
A receiving apparatus.

(Appendix 2)
The reception quality improvement means further comprises a local frequency switching means for switching a local frequency generated by the local frequency oscillator,
Perform image removal by switching local frequency,
The receiving device according to Supplementary Note 1, wherein

(Appendix 3)
The local frequency oscillator generates either a local frequency band upper local or lower local as the local frequency,
The local frequency switching means switches to lower local when the local frequency generated by the local frequency oscillator is upper local, and upper local when the local frequency generated by the local frequency oscillator is lower local. Switch to
The receiving device according to Supplementary Note 2, wherein

(Appendix 4)
The band switching means switches the first band characteristic to the second band characteristic only while the interference wave detection means is performing the interference wave detection operation, and after the interference wave detection operation, Returning a second band characteristic to the first band characteristic;
The receiving device according to any one of appendices 1 to 3, wherein

(Appendix 5)
A second filter downstream from the first filter;
The jamming wave detecting means detects a jamming wave caused by an adjacent channel based on signal power before and after filtering by the second filter;
5. The receiving device according to any one of appendices 1 to 4, wherein

(Appendix 6)
A local frequency oscillator for generating a local frequency;
A frequency converter that performs frequency conversion by mixing the received signal and the local frequency;
A first filter for filtering the signal frequency-converted by the frequency converter;
A computer for controlling a receiving device comprising:
A function of switching the characteristic of the first filter from a first band characteristic covering a frequency band of a desired channel to a second band characteristic covering a frequency band including a part of the desired channel and an adjacent channel; ,
A function of detecting an interference wave due to an adjacent channel based on signal power before and after filtering by the second filter;
A function to improve the reception quality by removing the image when the interference wave by the adjacent channel is detected,
A program characterized by realizing.

DESCRIPTION OF SYMBOLS 1 ... Receiver apparatus, 10 ... RF circuit part, 11 ... RF amplifier, 12 ... Frequency converter, 13 ... Local oscillator, 14 ... Analog filter, 15 ... IF amplifier, 20 ... Demodulator circuit part, 21 ... ADC, 22 ... Digital Filter 23, storage unit 24, RF control unit 200, demodulator 210, demodulation function 220, filter switching function 230, received power calculation function 240, interference wave detection function 250, reception quality improvement function

Claims (6)

A local frequency oscillator for generating a local frequency;
A frequency converter that performs frequency conversion by mixing the received signal and the local frequency;
A first filter for filtering the signal frequency-converted by the frequency converter;
Band switching for switching the characteristic of the first filter from the first band characteristic covering the frequency band of the desired channel to the second band characteristic covering the frequency band including a part of the desired channel and the adjacent channel. Means,
An interference wave detecting means for detecting an interference wave due to an adjacent channel by switching the characteristics of the first filter by the band switching means;
Reception quality improvement means for improving reception quality by image removal when the interference wave detection means detects an interference wave due to an adjacent channel;
A receiving apparatus. The reception quality improvement means further comprises a local frequency switching means for switching a local frequency generated by the local frequency oscillator,
Perform image removal by switching local frequency,
The receiving apparatus according to claim 1. The local frequency oscillator generates either a local frequency band upper local or lower local as the local frequency,
The local frequency switching means switches to lower local when the local frequency generated by the local frequency oscillator is upper local, and upper local when the local frequency generated by the local frequency oscillator is lower local. Switch to
The receiving device according to claim 2. The band switching means switches the first band characteristic to the second band characteristic only while the interference wave detection means is performing the interference wave detection operation, and after the interference wave detection operation, Returning a second band characteristic to the first band characteristic;
The receiving apparatus according to claim 1, wherein the receiving apparatus is a receiving apparatus. A second filter downstream from the first filter;
The jamming wave detecting means detects a jamming wave caused by an adjacent channel based on signal power before and after filtering by the second filter;
The receiving device according to claim 1, wherein the receiving device is a receiving device. A local frequency oscillator for generating a local frequency;
A frequency converter that performs frequency conversion by mixing the received signal and the local frequency;
A first filter for filtering the signal frequency-converted by the frequency converter;
A computer for controlling a receiving device comprising:
A function of switching the characteristic of the first filter from a first band characteristic covering a frequency band of a desired channel to a second band characteristic covering a frequency band including a part of the desired channel and an adjacent channel; ,
A function of detecting an interference wave due to an adjacent channel based on signal power before and after filtering by the second filter;
A function to improve the reception quality by removing the image when the interference wave by the adjacent channel is detected,
A program characterized by realizing.

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