JP4941165B2 - Receiver - Google Patents

Description

  The present invention relates to a receiving apparatus, and more particularly to a receiving apparatus suitable for control of reception gain in a conversion method.

  In a receiving apparatus that receives various types of broadcast radio waves such as digital broadcasting, a conversion method is widely used in which a received high frequency signal is converted into an intermediate frequency signal and then demodulated. In such a conversion type receiver, since the frequency of the received signal is normally converted to a lower frequency (down conversion), it is possible to perform stable amplification rather than amplifying the high frequency as it is.

In such a receiving apparatus, it is common to use an AGC (Automatic Gain Control) circuit that automatically adjusts the gain of the received signal (for example, Patent Document 1).
JP 7-336283 A

  In the conventional method as disclosed in Patent Document 1, gain control is performed based on the received signal strength indicator (RSSI), but control is performed using an RSSI signal based only on the desired wave. For this reason, when the RSSI value increases due to mixing of interference waves, the gain is controlled to be lower than necessary, and the signal level of the desired wave may be reduced (so-called sensitivity). Suppression effect). As a result, there arises a disadvantage that the reception quality is deteriorated.

  In addition, the bandpass filter is used to limit the received signal to the band component of the desired wave. Usually, however, the band of the desired wave is very narrow compared to the frequency of the carrier wave. If there is an interference wave, the signal of the interference wave cannot be completely removed with only the bandpass filter for the desired wave. In this case, the interference wave signal is also input to the mixer. Since the dynamic range of a mixer is usually narrow, if a signal containing an interfering wave is input to the mixer, a large distortion occurs in the signal output from the mixer, which causes a problem of signal degradation of the desired wave (so-called mixing). Modulation).

  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 that can perform good reception even when an interference wave is included in a received signal.

In order to achieve the above object, a receiving apparatus according to the present invention provides:
In a receiving apparatus that converts a received high frequency signal into an intermediate frequency signal and demodulates it,
First filter means for filtering the intermediate frequency signal with a frequency characteristic for extracting a desired wave to be demodulated;
Second filter means for filtering the intermediate frequency signal with two or more filters each having a different frequency characteristic and both having a frequency characteristic different from the frequency characteristic of the first filter means;
Difference detection means for detecting a difference between the signal power of each of the outputs from the two or more filters of the second filter means and the signal power of the output from the first filter means;
Gain control means for controlling the gain of the received high-frequency signal based on the difference detected by the difference detection means ,
Each of the two or more filters of the second filter means includes a frequency band filtered by the first filter means, and filters the intermediate frequency signal in a frequency band wider than the frequency band;
It is characterized by that.
In order to achieve the above object, a receiving apparatus according to the present invention provides:
In a receiving apparatus that converts a received high frequency signal into an intermediate frequency signal and demodulates it,
First filter means for filtering the intermediate frequency signal with a frequency characteristic for extracting a desired wave to be demodulated;
Second filter means for filtering the intermediate frequency signal with two or more filters each having a different frequency characteristic and both having a frequency characteristic different from the frequency characteristic of the first filter means;
Difference detection means for detecting a difference between the signal power of each of the outputs from the two or more filters of the second filter means and the signal power of the output from the first filter means;
Gain control means for controlling the gain of the received high-frequency signal based on the difference detected by the difference detection means,
The gain control means determines whether or not an interference wave is mixed in the received signal based on the difference detected by the difference detection means. When the interference wave is mixed, the interference wave obtained from the difference is mixed. According to the frequency difference between the frequency band and the frequency band of the desired wave, gain control is performed so as to reduce the gain of the received high-frequency signal.
It is characterized by that.

In the above receiver,
Each of the two or more filters of the second filter means desirably filters the intermediate frequency signal in a frequency band corresponding to an interference wave.

In the above receiver,
Each of the two or more filters of the second filter means preferably includes the frequency band filtered by the first filter means and filters the intermediate frequency signal in a frequency band wider than the frequency band. .

In the above receiver,
The gain control means determines whether or not an interference wave is mixed in the received signal based on the difference detected by the difference detection means, and when the interference wave is mixed, the difference and the first filter means It is desirable to perform gain control in accordance with the signal power of the output from.

in this case,
The gain control means can determine that an interference wave is mixed in the received signal when any of the plurality of difference values detected by the difference detection means is a value other than zero.

The receiving device is
A plurality of filter units each including the first filter means and the second filter means may be provided. In this case,
It is preferable that the apparatus further includes a filter selection unit that selects a filter unit to be operated from the plurality of filter units according to a reception operation of the reception device.

  According to the present invention, good reception can be performed even when an interference wave is included in the received signal.

(Embodiment 1)
Embodiments according to the present invention will be described below with reference to the drawings. In the present embodiment, a case where the receiving device according to the present invention is realized as a receiving device for digital broadcasting, for example, is illustrated.

  FIG. 1 is a block diagram schematically showing the configuration of a receiving device 1 according to an embodiment of the present invention. A receiving apparatus 1 according to the present embodiment is a so-called conversion type (heterodyne type) receiving apparatus that converts a received high-frequency signal into an intermediate frequency signal and then demodulates it. As shown in FIG. The conversion unit 100, the intermediate frequency amplification unit IA, the demodulation unit DM, and the like are schematic configurations of the reception device 1.

  The antenna AN is an antenna that resonates at the frequency of a radio wave to be received by the receiving device 1, and inputs a received high-frequency signal to the high-frequency conversion unit 100.

  The high frequency conversion unit 100 includes, for example, a high frequency amplification circuit, a frequency conversion circuit, a local oscillation circuit, and the like, and converts a high frequency signal input from the antenna AN into an intermediate frequency signal.

  The intermediate frequency amplification unit IA includes, for example, an intermediate frequency amplification circuit and a filter, and performs amplification and filtering of the intermediate frequency signal converted by the high frequency conversion unit 100.

  The demodulating unit DM is configured by, for example, a demodulating circuit corresponding to a radio wave modulation method to be received by the receiving device 1, and demodulates and outputs the signal amplified by the intermediate frequency amplifying unit IA.

  In the present embodiment, the high-frequency conversion unit 100 performs automatic gain control (AGC) of a received high-frequency signal. At that time, good reception is achieved by performing gain control in consideration of the mixed interference wave. The configuration of such a high-frequency conversion unit 100 will be described with reference to FIG. FIG. 2 is a block diagram illustrating a configuration of the high-frequency conversion unit 100 according to the present embodiment.

  As shown in the figure, the high-frequency converter 100 according to the present embodiment includes a high-frequency amplifier 110, a frequency converter 120, a desired wave filter 130, a first disturbing wave filter 140A, a second disturbing wave filter 140B, and a first It includes a difference detector 150A, a second difference detector 150B, a gain controller 160, and the like.

The high-frequency amplifier 110 takes out a desired wave from a high-frequency amplifier circuit such as an LNA (Low Noise Amplifier), a matching circuit for matching the impedance of the antenna AN and the high-frequency amplifier circuit, and the high-frequency signal RF _0. The radio frequency signal RF ₀ received from the antenna AN is amplified, and the amplified radio frequency signal RF ₁ is output to the frequency converter 120. The high-frequency amplifier 110 has an AGC function, and controls the gain (gain) of the received high-frequency signal RF ₀ based on a control signal from the gain controller 160 described later.

The frequency conversion unit 120 includes, for example, a mixer circuit (mixer), a local oscillation circuit (for example, a PLL frequency synthesizer), and the like. The high-frequency signal RF ₁ amplified by the high-frequency amplification unit 110 is received inside the reception device 1. The signal is converted into an intermediate frequency signal IF having a frequency suitable for signal processing. In this case, the high frequency signal RF ₁ input from the high frequency amplifier 110 and the output signal from the local oscillation circuit are mixed by a mixer circuit, thereby converting the frequency of the high frequency signal RF ₁ to a predetermined intermediate frequency. In the present embodiment, the so-called down-conversion, are intended to be converted to an intermediate frequency signal IF having a frequency lower than the radio frequency signal RF ₁ input.

The desired wave filter 130 is a bandpass filter configured by a filter circuit such as a ceramic filter, a crystal filter, or a SAW (Surface Acoustic Wave) filter, and is an output from the frequency converter 120. The intermediate frequency signal IF is filtered to obtain a desired wave having a desired frequency. That is, the desired wave filter 130 is a filter having a frequency characteristic that filters in the frequency band of the desired wave. In this case, the desired wave filter 130 functions as a so-called notch filter having a frequency characteristic that attenuates sharply with the frequency (f ₀ ) of the desired wave as the center frequency.

The desired wave signal IF ₀ extracted by such a desired wave filter 130 is output to the subsequent intermediate frequency amplification unit IA and also output to the gain control unit 160 to notify the signal level.

  The first interference wave filter 140A and the second interference wave filter 140B are filters that filter the intermediate frequency signal IF from the desired wave filter 130, as with the desired wave filter 130, but according to the assumed interference wave. It has a frequency characteristic that filters the frequency band.

Here, examples of frequency characteristics of the desired wave filter 130, the first interference wave filter 140A, and the second interference wave filter 140B will be described with reference to FIG. Here, all the frequency bands filtered by the filters are defined by the characteristics of the pass band as shown in FIG. 3 with a predetermined frequency as the center frequency. In this case, the frequency f ₀ of the desired wave is set as a common center frequency for each filter.

In the present embodiment, it is assumed that the desired wave filter 130, the first interference wave filter 140A, and the second interference wave filter 140B have different frequency characteristics. In this case, the frequency characteristic fw ₀ of the desired wave filter 130 is a frequency characteristic that sharply attenuates outside the band of the frequency f _{0 of the} desired wave (that is, the center frequency) as described above. This is because the desired wave filter 130 is intended to extract the desired wave from the received signal.

On the other hand, since the first interference wave filter 140A and the second interference wave filter 140B are filters having frequency characteristics corresponding to the interference wave as described above, a wider band centered on the frequency f _{0 of the} desired wave. Frequency characteristics. In addition, since various frequency components are included in the jamming wave, in this embodiment, the frequency characteristics of the first jamming wave filter 140A and the second jamming wave filter 140B so as to cope with the possible jamming wave. Also make each different.

In the present embodiment, the first disturbing wave filter 140A has a frequency characteristic of filtering a band wider than the frequency band fw ₀ filtered by the desired wave filter 130, and the second disturbing wave filter 140B is It is assumed that the filter has a frequency characteristic for filtering a wider band than the frequency band filtered by the interference wave filter 140A.

As described above, since all of the desired wave filter 130, the first interference wave filter 140A, and the second interference wave filter 140B have a common center frequency (desired wave frequency f ₀ ), the first interference Both the wave filter 140 </ b> A and the second interference wave filter 140 </ b> B include the frequency band fw ₀ of the desired wave filter 130. Hereinafter, the frequency band filtered by the first disturbance wave filter 140A is referred to as a frequency band fw _1, and the frequency band filtered by the second disturbance wave filter 140B is a frequency band fw ₂ . In this case, the magnitude relationship between the frequency bands of the filters is “fw ₀ <fw ₁ <fw ₂ ”.

  As described above, the high-frequency converter 100 according to the present embodiment includes a filter (desired wave filter 130) for extracting a desired wave from an intermediate frequency signal obtained by frequency conversion, and 2 for extracting an interference wave included in the received wave. The above filters (first interference wave filter 140A and second interference wave filter 140B) are included.

  The first difference detection unit 150A and the second difference detection unit 150B are configured by, for example, a difference circuit and detect a difference between two inputs. In the present embodiment, the difference between each of the outputs from the first interference wave filter 140A and the second interference wave filter 140B and the output from the desired wave filter 130 is taken.

In this case, an intermediate frequency signal IF ₁ that is an output from the first interference wave filter 140A and an intermediate frequency signal IF ₀ that is an output from the desired wave filter 130 are input to the first difference detection unit 150A. The

The second difference detection portion 150B, an intermediate frequency signal IF ₂ is the output from the second interference wave filter 140B, an intermediate frequency signal IF ₀ is input is the output from the desired wave filter 130.

That is, the first difference detector 150A detects a difference (D1) between the intermediate frequency signal IF ₁ and the intermediate frequency signal IF _0, the second difference detector 150B, an intermediate frequency signal IF ₂ and the intermediate detecting a difference (D2) between the frequency signal IF _0. Here, for example, a difference in signal level (power) of the input intermediate frequency signal is detected.

  The gain control unit 160 is configured by an arithmetic circuit such as an LSI, for example, and based on the output D1 from the first difference detection unit 150A and the output D2 from the second difference detection unit 150B, in the high frequency amplification unit 110 Controls the gain of the received signal. That is, by controlling the gain of the high-frequency amplifier 110 by the gain controller 160, automatic gain control (AGC) for the received high-frequency signal is realized.

  In the present embodiment, for example, the gain control unit 160 generates a control signal for controlling the operation of the high-frequency amplification unit 110 by calculation according to the difference signal D1 and / or the difference signal D2, and the high-frequency amplification unit 110 To enter. That is, the gain in the high frequency amplification unit 110 is controlled by feedback according to the difference result of the filter output.

  In the present embodiment, the high-frequency conversion unit 100 is configured by a dedicated circuit or the like corresponding to each function as described above. Among the above-described configurations, for example, the first difference detection unit 150A and the first For example, a CPU (Central Processing Unit) or a DSP (Digital Signal Processor) that controls the entire receiving device 1 has a configuration that performs arithmetic processing such as the two difference detection units 150B and the gain control unit 160. Functions related to these configurations may be realized by performing logical operations.

  The above-described configuration of the high-frequency conversion unit 100 and each configuration of the receiving device 1 are necessary for realizing the present invention, and other configurations necessary for the receiving device are appropriately determined as necessary. It shall be provided.

  The operation of the receiving apparatus 1 configured as above will be described. In the receiving apparatus according to the present invention, in order to obtain good reception quality even when an interference wave is mixed, a characteristic operation is performed at the time of gain control of the received high-frequency signal. Therefore, in the present embodiment, the following description will be focused on the operation relating to the high-frequency conversion unit 100.

  “Gain control processing” performed by the high-frequency conversion unit 100 during the reception operation of the reception device 1 will be described with reference to the flowchart shown in FIG. For example, this gain control process is started when a reception operation in the reception device 1 is started.

When the radio wave is received by the antenna AN, the high frequency signal RF ₀ is input to the high frequency amplifier 110. Received radio waves, usually because a weak signal, a high frequency amplifying unit 110, a radio frequency signal RF ₀ input is amplified to the signal level necessary for frequency conversion (step S101). The high frequency amplification unit 110 outputs the amplified high frequency signal RF ₁ to the frequency conversion unit 120.

When the high frequency signal RF ₁ amplified by the high frequency amplification unit 110 is input to the frequency conversion unit 120, the frequency conversion unit 120 mixes the oscillation frequency of the local oscillation circuit and the high frequency signal RF ₁ to obtain a predetermined intermediate signal. Conversion to a frequency signal IF (step S102).

The intermediate frequency signal IF converted by the frequency converter 120 is input to each of the desired wave filter 130, the first interference wave filter 140A, and the second interference wave filter 140B, and the filtering according to the frequency characteristics of each filter is performed. This is performed (step S103). That is, the desired wave filter 130 filters the frequency band fw ₀ close to the frequency band of the desired wave, and the first interference wave filter 140A and the second interference wave filter 140B correspond to the frequency band of the interference wave to be prevented. Filtered to different bandwidths (fw ₁ and fw ₂ ).

When filtered by each filter, the intermediate frequency signal IF ₀ after filtering by the desired wave filter 130 is input to each of the first difference detection unit 150A and the second difference detection unit 150B. The intermediate frequency signal IF ₁ after filtering by the first interference wave filter 140A is inputted to the first difference detector 150A, the intermediate frequency signal IF ₂ after filtering by the second interference wave filter 140B of the second The difference is input to the difference detector 150B.

Each of the first difference detection unit 150A and the second difference detection unit 150B detects a difference in signal level (power) of a plurality of input intermediate frequency signals. That is, in the first difference detector 150A, detects the difference of the intermediate frequency signal IF ₁ and the signal level (power) of the intermediate frequency signal IF ₀ P, the differential signal _{D1 (D1 = P (IF 1} ) -P (IF ₀ )) is output. Further, in the second difference detector 150B, detects the difference of the intermediate frequency signal IF ₂ and the signal level (power) of the intermediate frequency signal IF ₀ P, the difference signal _{D2 (D2 = P (IF 2} ) -P (IF ₀ )) is output.

That is, the signal level of each of the intermediate frequency signals filtered to a plurality of frequency bands (fw ₁ and fw ₂ ) corresponding to the assumed interference wave and the intermediate frequency signal filtered to the frequency band fw ₀ corresponding to the desired wave A difference is detected (step S104).

Outputs D1 and D2 from the first difference detection unit 150A and the second difference detection unit 150B are input to the gain control unit 160, respectively. The gain control unit 160 generates a control signal GC for performing gain control on the high-frequency signal RF ₀ in the high-frequency amplification unit 110 based on the input D1 and D2.

Here, the relationship between the differential signals D1 and D2 and the gain control in the high-frequency amplifier 110 will be described. As described above, the three filters of the desired wave filter 130, the first jamming wave filter 140A, and the second jamming wave filter 140B have different frequency bandwidths for filtering (fw ₀ ≠ fw ₁ ≠ fw ₂ ). center frequency is common at the center frequency f ₀ of the desired wave. Therefore, in the ideal reception state where only the desired wave is received without interfering waves, the intermediate frequency signal after filtering by each filter is a signal containing only the frequency component of the desired wave. Become.

Here, both the first interference wave filter 140A and the second interference wave filter 140B have frequency characteristics in a frequency band wider than the frequency band fw _{0 in} which the desired wave filter 130 filters, but only the desired wave. Can be received, both the intermediate frequency signal IF ₁ and the intermediate frequency signal IF ₂ that have been filtered by these filters are the intermediate frequency signals that have been filtered by the desired wave filter 130. it comes to substantially the same signal level as the IF _0.

In such a case, since the difference in signal level between each of the intermediate frequency signal IF ₁ and the intermediate frequency signal IF ₂ and the intermediate frequency signal IF ₀ is equal to or less than a predetermined value, each of the difference signal D1 and the difference signal D2 is The difference values shown are all “0”. In other words, when both the difference signal D1 and the difference signal D2 indicate the difference value “0”, it can be determined that no interference wave is mixed in the received signal. That is, when either of the input difference signal D1 and difference signal D2 is not “0” (“D1 ≠ 0” or “D2 ≠ 0”), an interference wave is mixed in the received signal.

Here, the differential signal D1 reflects the signal level of the intermediate frequency signal IF ₁ which is filtered by the first interference wave filter 140A, the differential signal D2 is an intermediate frequency signal filtered by the second interference wave filter 140B It reflects the signal level of the IF _2. The first interference wave filter 140A and the second interference wave filter 140B have different frequency bandwidths for filtering (fw ₁ <fw ₂ ). That is, the second interference wave filter 140B has a wider bandwidth including the band of the first interference wave filter 140A. For this reason, the frequency band of the interfering interference wave can be determined based on the combination of the difference signal whose difference value indicates other than 0 and the value thereof.

For example, when “D1 ≠ 0, D2 = D1”, the interference wave is mixed in the frequency band fw ₁ corresponding to the first interference wave filter 140A. When “D1 = 0, D2 ≠ 0”, the frequency band fw is outside the frequency band fw ₁ corresponding to the first interference wave filter 140A and corresponds to the second interference wave filter 140B. _The interference wave is mixed in the band ₂ . Further, when “D1 ≠ 0, D2> D1”, an interference wave is mixed in the frequency band fw ₁ corresponding to the first interference wave filter 140A, and also corresponds to the first interference wave filter 140A. Interference waves are also mixed in the frequency band fw ₂ outside the frequency band fw ₁ and in the frequency band fw ₂ corresponding to the second interference wave filter 140B.

Here, the influence of the mixed interference wave on the desired wave differs depending on the frequency band of the interference wave. FIG. 5A shows an example of the distortion degree characteristic that the interference wave has on the desired wave. FIG. 5A shows the relationship between the frequency of the disturbing wave and the magnitude of distortion that the disturbing wave has on the desired wave when the frequency of the desired wave is the center frequency. As shown in the figure, the closer the frequency (± Δf) of the interference wave is to the frequency f ₀ of the desired wave, the greater the distortion on the desired wave.

  Due to such characteristics, when the gain control of the received signal is performed based only on the signal level from the filter that extracts the frequency band of the desired wave as in the conventional receiver, regardless of the frequency band of the interfering wave mixed in, The feedback signal (RSSI signal) is uniformly increased. In this way, when the received signal level increases, the gain is controlled to decrease, so the gain is decreased regardless of the frequency band of the jamming wave, and the signal level of the desired wave also decreases more than necessary. May end up.

In order to avoid such an inconvenience, the receiving apparatus according to the present invention performs gain control according to the signal level applied to a plurality of frequency bands corresponding to the disturbing wave and the signal level of the desired wave. Here, the gain control unit 160, the difference value indicated by the difference signal D1 or differential signal D2, based on the signal level of the desired signal IF _0, which is converted to an intermediate frequency, and controls the gain in the high frequency amplifying unit 110 .

In this case, the gain control unit 160 generates a control signal GC for controlling the operation of the high frequency amplification unit 110 so as to obtain a gain amount as shown in FIG. 5B, for example. In FIG. 5B, when there is no interference wave (D1 = 0, D2 = 0), when there is an interference wave in the frequency band fw ₁ (D1 ≠ 0, D2 = D1), the frequency band fw ₁ , and the frequency band The signal of the intermediate frequency signal IF ₀ of the desired wave in each of the three cases when there is an interference wave outside the band of fw ₁ and within the band of the frequency band fw ₂ (D1 ≠ 0, D2> D1) A suitable gain amount according to the level (hereinafter referred to as “desired gain amount”) is shown.

Here, the purpose of gain control of the received signal is to make the signal level of the signal processed in the receiving apparatus 1 constant. Therefore, if the interference wave is not mixed (D1 = 0, D2 = 0 ) , the internal processing signals, i.e., in accordance with the signal level of the intermediate frequency signal IF _0, will control the gain of the received signal. Therefore, as indicated by a solid line in FIG. 5B, the desired gain amount DG ₀ when there is no interfering wave is higher as the signal level of the intermediate frequency signal IF ₀ is lower, and the signal level of the intermediate frequency signal IF ₀ is higher. It is set to be lower.

On the other hand, the desired gain DG ₁ when the interference wave of the frequency band fw ₁ is mixed (D 1 ≠ 0, D 2 = D 1) is equal to the intermediate frequency signal IF ₀ as shown by the dotted line in FIG. when the signal level is low, a lower amount of gain than the desired amount of gain DG ₀ when there is no interference wave, as the signal level of the intermediate frequency signal IF ₀ is high, the desired amount of gain DG ₀ when there is no interference wave It is set to approximate.

Here, since the frequency band fw ₁ is a frequency band that is relatively close to the frequency f _{0 of} the desired wave, when an interference wave in the frequency band fw ₁ is mixed, distortion on the desired wave increases (FIG. 5 (a)). )reference). Therefore, the desired gain amount DG ₁ is set to a gain amount lower than the desired gain amount DG ₀ so that distortion does not occur in the desired wave.

Further, the desired gain amount DG when interference waves are mixed in both the frequency band fw ₁ and the frequency band fw ₁ and within the frequency band fw ₂ (D1 ≠ 0, D2> D1). _{In the} case where the signal level of the intermediate frequency signal IF ₀ is low, ₂ is set to a gain amount lower than the desired gain amount DG ₁ in order to remove the generated interference wave. Here, as shown in FIG. 3, the frequency band fw ₂ is wider than the frequency bands fw ₀ and fw ₁ . Then, as shown in FIG. 5 (a), as the frequency of the interference wave is far from the frequency f ₀ of the desired wave, the interference wave is reduced effect on the desired signal. That is, when the signal level of the intermediate frequency signal IF ₀ is greater than a certain level, the influence of distortion is reduced. Therefore, as shown by the one-dot chain line in FIG. gain weight DG ₂ is not set, and shall not perform the gain control.

As described above, the gain amount of the high-frequency amplification unit 110 controlled by the gain control unit 160 is the distortion degree characteristic that the interference wave has on the desired wave as shown in FIG. 5A, and the first difference detection unit 150A. And the interfering wave frequency band determined based on the difference value detected by the second difference detector 150B, and the signal level of the intermediate frequency signal IF ₀ processed by the intermediate frequency amplifier IA and the like at the subsequent stage. It is prescribed based on.

  Therefore, the gain control unit 160 generates a control signal for causing the high-frequency amplification unit 110 to perform a gain adjustment operation based on the setting of the desired gain amount as shown in FIG. Returning to the flowchart shown in FIG. 4, the continuation of the process will be described.

  When the differences D1 and D2 detected in step S104 are input, the gain control unit 160 first determines whether “D1 ≠ 0” or “D2 ≠ 0”, thereby obtaining a received signal. It is determined whether or not an interference wave is mixed (step S105).

When it is determined that the interference signal is mixed in the received signal based on the difference signal (step S105: Yes), the gain control unit 160 prevents the sensitivity suppression effect and the cross modulation that may occur due to the influence of the mixed interference wave. Therefore, a control signal GC for performing gain control of the received high-frequency signal RF ₀ in the high-frequency amplifier 110 is generated. In this case, the gain control unit 160 specifies the frequency band of the interfering interference wave based on the combination of the difference signal whose difference value is other than 0 and the value (step S106), and is input from the desired wave filter 130. It recognizes the signal level of the intermediate frequency signal IF ₀ was (step S107).

Here, it is assumed that the gain control unit 160 in this embodiment includes a storage device such as a ROM (Read Only Memory), for example, and the storage device such as shown in FIG. It is assumed that information defining the gain amount is stored. In this case, for example, the combination of the frequency band of the interference wave and the signal level of the intermediate frequency signal IF ₀ corresponding to DG ₁ and DG ₂ shown in FIG. Assume that a correspondence table in which the numerical values shown are associated is stored. This correspondence table also includes a setting (DG _{0 in} FIG. 5B) in which there is no interfering wave in which the signal level of the intermediate frequency signal IF ₀ is associated with the desired gain amount.

The gain controller 160 refers to the correspondence table stored in the storage device based on the identified frequency band of the disturbing wave and the recognized signal level of the intermediate frequency signal IF ₀ , and obtains a desired gain under the conditions. The amount (desired gain amount) is specified (step S108).

  When the gain control unit 160 specifies the desired gain amount, the gain control unit 160 generates a control signal GC for operating the high-frequency amplification unit 110 so that the gain amount in the high-frequency amplification unit 110 becomes the desired gain amount. It is sent out (step S109). In this case, the high frequency amplification unit 110 amplifies the reception signal based on the control signal GC from the gain control unit 160, so that the reception operation is performed with the desired gain amount specified in step S108.

  The high-frequency conversion unit 100 repeats the above processing until the reception operation of the receiving device 1 is completed (step S110: No). When an interference wave is mixed, the frequency band of the interference wave, Since appropriate gain control is performed according to the signal level of the intermediate frequency signal at the time, an intermediate frequency signal having a necessary and sufficient signal level can be obtained even if an interference wave is mixed, and good reception can be performed. it can.

When there is no interference wave mixing (step S105: No), the gain control unit 160 refers to the correspondence table based only on the signal level of the intermediate frequency signal IF ₀ at that time, thereby mixing the interference wave. If there is no desired gain, the desired gain amount is specified (step S107, step S108).

  And a process is complete | finished with the completion | finish of receiving operation of the receiver 1 (step S110: Yes).

  As described above, according to the first embodiment of the present invention, in addition to the filter for extracting the desired wave, two or more filters corresponding to the frequency band of the disturbing wave are prepared, and the outputs of these filters Since the difference from the output of the desired wave is detected, it is possible to determine whether or not the interference wave is mixed, and it is possible to perform appropriate gain control depending on whether or not the interference wave is mixed.

  Moreover, since the frequency characteristics of the two or more filters corresponding to the frequency band of the disturbing wave are made different, gain control according to the frequency band of the mixed disturbing wave can be performed. As a result, it is possible to perform gain control according to the influence of different interference waves depending on the proximity to the desired wave frequency.

  As described above, appropriate gain control can be performed according to the interference wave, so that an intermediate frequency signal having a desired signal level can be obtained without generating a sensitivity suppression effect or cross modulation. As a result, good reception quality can be obtained even when interference waves are mixed.

(Embodiment 2)
In the first embodiment, an example in which the desired wave filter 130 for extracting the desired wave, the first disturbing wave filter 140A and the second disturbing wave filter 140B corresponding to the disturbing wave has been described. For example, a plurality of filter units each including a desired wave filter and two or more interference wave filters are prepared according to a plurality of desired frequencies to be selected, and the filter unit is selectively selected according to the channel selection. It may be configured to operate.

  The configuration of the high-frequency conversion unit 100 in this case is shown in FIG. Here, since the basic configuration of the high-frequency conversion unit 100 according to the present embodiment is the same as the high-frequency conversion unit 100 shown in the first embodiment, the same reference numerals are given to the same configurations, and detailed description is given. Is omitted.

  As shown in the figure, the high-frequency conversion unit 100 according to the present embodiment includes a high-frequency amplification unit 110, a frequency conversion unit 120, a first difference detection unit 150A, a second difference detection unit 150B, a gain control unit 160, and the like. In addition, a filter selection unit SW and a filter unit FL are added.

The filter unit FL includes a plurality of filter units FU (FU _{1 to} FU _n ). The configuration of each filter unit FU is shown in FIG. As shown in the figure, each filter unit FU includes the desired wave filter 130, the first interference wave filter 140A, and the second interference wave filter 140B described in the first embodiment.

  Returning to FIG. 6, the filter selection unit SW is a switch circuit positioned between the plurality of filter units FU and the frequency conversion unit 120 that constitute such a filter unit FL. A desired filter unit FU is selected by switching the signal path in the filter unit FL based on the external signal to be input, and the intermediate frequency signal IF output from the frequency conversion unit 120 is input.

In the filter unit FU selected by the operation of the filter selection unit SW, the intermediate frequency signal IF from the frequency conversion unit 120 is supplied to each of the desired wave filter 130, the first interference wave filter 140A, and the second interference wave filter 140B. The intermediate frequency signal IF ₀ , the intermediate frequency signal IF ₁ , and the intermediate frequency signal IF ₂ are output from each filter by the same operation as in the first embodiment. The filtered intermediate frequency signal is output from the filter unit FL as an output from the filter unit FU.

At this time, the intermediate frequency signal IF ₀ is output to each of the first difference detection unit 150A, the second difference detection unit 150B, the gain control unit 160, and the subsequent intermediate frequency amplification unit IA. IF ₁ is output to the first difference detector 150A, and the intermediate frequency signal IF ₂ is output to the second difference detector 150B.

The first difference detection unit 150A detects a difference between the intermediate frequency signal IF ₁ and the intermediate frequency signal IF ₀ as in the first embodiment, and the second difference detection unit 150B detects the difference between the intermediate frequency signal IF ₂ and the intermediate frequency signal IF _2. The difference from the frequency signal IF ₀ is detected. Difference signals D 1 and D 2 indicating the respective difference values are output to gain control section 160.

  The gain control unit 160 performs the same gain control as in the first embodiment by generating a control signal GC corresponding to the specified desired gain amount and sending it to the high frequency amplification unit 110 by the same method as in the first embodiment. Will be.

  As described above, the high-frequency conversion unit 100 according to the present embodiment includes a plurality of filter units each including one desired wave filter and two or more interference wave filters. The filter unit to be used is selected based on the above, so appropriate gain control can be performed even when there are many types of desired waves, and good reception quality can be obtained even if interference waves are mixed Can do.

  In the above embodiment, the operation of selecting the filter unit may be performed by, for example, a CPU or DSP that controls the entire receiving device 1.

  As described above, according to the above embodiments of the present invention, good reception quality can be obtained even when an interference wave is mixed.

  That is, in addition to a filter for extracting a desired wave as used in a normal frequency conversion circuit, two or more filters corresponding to the frequency band of the interference wave to be removed are prepared, and a difference between outputs of the filters is detected. Therefore, it is possible to determine the presence or absence of interference wave based on the detected difference, and when interference wave is mixed, the gain control different from normal is performed, so the sensitivity suppression effect and It does not cause a factor that deteriorates reception quality such as modulation.

  That is, the filter of the high frequency amplification unit normally used in the receiving device has a very narrow desired wave band compared to the frequency of the carrier wave, so if there is an interference wave near the desired wave, only the filter of the high frequency amplification unit is It is impossible to completely remove the interference signal. Therefore, the disturbing wave existing in the vicinity of the desired wave is mixed into the received signal input to the subsequent frequency conversion unit. Therefore, as in the above-described embodiment, by further adding a plurality of filters corresponding to the disturbing wave to the subsequent stage of the frequency conversion unit, it is possible to accurately detect mixing of the disturbing wave and perform appropriate gain control.

  In this case, since it is possible to determine the presence / absence of the interference wave by an extremely easy process of whether the difference from the desired wave is 0 or other than 0, it is possible to quickly determine the interference wave interference with a simple configuration. Can be done.

  In addition, since each of the two or more filters corresponding to the interference wave has different frequency characteristics, it is possible to easily determine which frequency band the interference wave is based on the difference value of each filter. Therefore, appropriate gain control according to the frequency band of the interference wave can be performed, and good reception quality can be obtained efficiently.

  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 each of the above embodiments, the number of filters corresponding to the interference wave used when receiving a desired desired wave is two, but two or more filters may be prepared. Even in this case, by taking the difference between the output of each interference wave filter and the output of the desired wave filter, it is possible to target interference waves in a wider frequency band, and to distinguish the frequency bands of interference waves in more detail. can do.

  In the high frequency conversion unit 100 of the above embodiment, the case of general down conversion is exemplified as the conversion method. However, if the gain control is to stabilize the signal level of the intermediate frequency signal, the frequency is higher than the frequency of the high frequency signal. The present invention may be applied to an up-conversion receiving device that converts to an intermediate frequency signal.

It is a block diagram which shows the structure of the receiver concerning embodiment of this invention. It is a block diagram which shows the structure of the high frequency converter concerning Embodiment 1 of this invention. It is a figure for demonstrating the frequency characteristic of the desired wave filter, the 1st disturbance wave filter, and the 2nd interference wave filter which are shown in FIG. It is a flowchart for demonstrating the "gain control process" concerning embodiment of this invention. FIG. 5 is a diagram for explaining elements when determining a desired gain amount in the gain control process shown in FIG. 4, wherein (a) shows an example of a distortion degree characteristic that an interference wave has on a desired wave, and (b) shows It is a figure which shows the example of the desired gain amount prescribed | regulated according to the signal level of the frequency band of an interference wave, or an intermediate frequency signal. It is a block diagram which shows the structure of the high frequency converter concerning Embodiment 2 of this invention. It is a block diagram which shows the structure of the filter unit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Receiver, AN ... Antenna, IA ... Intermediate frequency amplifier, DM ... Demodulator, 100 ... High frequency converter, 110 ... High frequency amplifier, 120 ... Frequency converter, 130 ... Desired wave filter, 140A ... First Interference wave filter, 140B ... second interference wave filter, 150A ... first difference detection unit, 150B ... second difference detection unit, 160 ... gain control unit, SW ... filter selection unit, FL ... filter unit, FU ... Filter unit, RF ... high frequency signal, IF ... intermediate frequency signal, D1 ... differential signal, D2 ... differential signal, DG ... desired gain amount, GC ... control signal

Claims (7)

In a receiving apparatus that converts a received high frequency signal into an intermediate frequency signal and demodulates it,
First filter means for filtering the intermediate frequency signal with a frequency characteristic for extracting a desired wave to be demodulated;
Second filter means for filtering the intermediate frequency signal with two or more filters each having a different frequency characteristic and both having a frequency characteristic different from the frequency characteristic of the first filter means;
Difference detection means for detecting a difference between the signal power of each of the outputs from the two or more filters of the second filter means and the signal power of the output from the first filter means;
Gain control means for controlling the gain of the received high-frequency signal based on the difference detected by the difference detection means ,
Each of the two or more filters of the second filter means includes a frequency band filtered by the first filter means, and filters the intermediate frequency signal in a frequency band wider than the frequency band;
A receiving apparatus. In a receiving apparatus that converts a received high frequency signal into an intermediate frequency signal and demodulates it,
First filter means for filtering the intermediate frequency signal with a frequency characteristic for extracting a desired wave to be demodulated;
Second filter means for filtering the intermediate frequency signal with two or more filters each having a different frequency characteristic and both having a frequency characteristic different from the frequency characteristic of the first filter means;
Difference detection means for detecting a difference between the signal power of each of the outputs from the two or more filters of the second filter means and the signal power of the output from the first filter means;
Gain control means for controlling the gain of the received high-frequency signal based on the difference detected by the difference detection means ,
The gain control means determines whether or not an interference wave is mixed in the received signal based on the difference detected by the difference detection means. When the interference wave is mixed, the interference wave obtained from the difference is mixed. According to the frequency difference between the frequency band and the frequency band of the desired wave, gain control is performed so as to reduce the gain of the received high-frequency signal.
A receiving apparatus. Each of the two or more filters of the second filter means filters the intermediate frequency signal in a frequency band corresponding to an interference wave;
The receiving device according to claim 2 . Each of the two or more filters of the second filter means includes a frequency band filtered by the first filter means, and filters the intermediate frequency signal in a frequency band wider than the frequency band;
The receiving apparatus according to claim 2 or 3 , wherein The gain control means determines whether or not an interference wave is mixed in the received signal based on the difference detected by the difference detection means, and when the interference wave is mixed, the difference and the first filter means Perform gain control according to the signal power of the output from
Receiving apparatus according to any one of claims 1 to 4, characterized in that. The gain control means determines that an interference wave is mixed in the received signal when any of the plurality of difference values detected by the difference detection means is a value other than 0.
The receiving apparatus according to claim 5 . A plurality of filter units each including the first filter means and the second filter means;
Further comprising a filter selection means for selecting a filter unit to be operated from the plurality of filter units in accordance with a reception operation of the reception device;
The receiving apparatus according to claim 1, wherein the receiving apparatus includes:

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