JP2005197918A - Receiver of cordless telephone set - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver of a cordless telephone set that can precisely control an attenuation rate and a band-removed component in a reception frequency band according to the intensity of a received wave signal and frequency components of disturbance waves and properly suppress influence of disturbance waves even when used in an environment where many disturbance waves are present. <P>SOLUTION: A control part 20 has a level decision means 20b, an error decision means 20c, a switch control means 20a, and a signal processing means 20d of performing processing based upon decision results of the level decision means 20b and error decision means 20c and sends out a switch control signal to a switch control means 20a according to the processing result, and the signal processing means 20d selects an attenuator 4a through the switch control means 20a when the level of the received wave signal exceeds a specified level and a band-removing filter 6a is selected through the switch control means 20a when error information is sent out as a result of a decision on received data although the attenuator 4a is operated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a receiver for a cordless telephone in which many interference waves such as an ISM frequency band exist and the frequency band to be used is easily affected by a nearby frequency band.

  In general, in a receiver used in a digital radio communication system employing GMSK modulation or the like, distortion due to nonlinearity of the reception system becomes a factor that increases the error rate. For example, if a radio frequency signal of a large level exceeding the dynamic range of a high frequency amplifier or frequency converter is input, the high frequency amplifier and the frequency converter are saturated and become an interference wave due to the generation of undesired waves called so-called intermodulation. This causes an increase in the error rate of received data, that is, a cause of a decrease in call quality, resulting in an uncomfortable call.

  Therefore, as a most commonly used measure for a conventional cordless telephone receiver, for example, the deterioration of the error rate is prevented as follows.

  FIG. 4 is a block diagram showing a conventional cordless telephone receiver (see, for example, Patent Document 2). In FIG. 4, 1 is an antenna, 2 is an antenna switch for switching antennas by transmission and reception, 3a and 3b are attenuator switching switches for selecting a later-described attenuator 4a or a later-described bypass circuit 4, and 4 is a bypass circuit for the attenuator 4a. 4a is an attenuator whose attenuation factor is controlled by the level of the received signal, 8a is a broadband band-pass filter (hereinafter referred to as "wideband filter"), and 9 is a low noise amplifier (LNA) that amplifies the received wave signal. ) 10 is a frequency converter (hereinafter also referred to as “reception mixer”) that converts a received wave signal into an intermediate frequency signal, 11 is a local oscillator that generates a local oscillation signal, and 12 is an intermediate frequency amplifier that amplifies the intermediate frequency signal. , 13 is a demodulator for demodulating the modulated signal of the received wave signal, and 15 is the received radio wave based on the intermediate frequency signal from the intermediate frequency amplifier 12. Field strength detector 16 for detecting the degree (that is, the level of the received wave signal), 16 is a receiving decoder for extracting received data from the demodulated signal 14 (baseband signal) demodulated and converted, and 20 controls the whole. A control unit (CPU). The control unit 20 includes a switch control unit 20a that controls the attenuation changeover switches 3a and 3b, a level determination unit 20b that performs determination based on the level of the received wave signal detected by the electric field strength detector 15, and a An error determination unit 20c that determines the presence or absence of an error based on received data, and a signal processing unit 20d that performs processing based on the determination results of the level determination unit 20b and the error determination unit 20c. An intermediate frequency filter that removes unnecessary components from the output signal of the frequency converter 10 is not shown.

  The operation of the receiver of the cordless telephone configured as described above will be described. A received wave signal output from the antenna 1 by receiving an incoming radio wave by the antenna 1 is amplified by a low noise amplifier 9 as a high frequency amplifier and then input to a frequency converter 10. The signal is mixed with the local oscillation signal generated from the oscillator 11 and converted into an intermediate frequency signal. From this intermediate frequency signal, only a predetermined band component is extracted by a band filter (not shown), then amplified by the intermediate frequency amplifier 12 and supplied to the demodulator 13. Up to this point, the configuration of a receiving circuit called superheterodyne is generally used.

In order to prevent the low noise amplifier 9 and the frequency converter 10 from being saturated in the receiver having such a configuration, an attenuator 4a and a bypass path of the attenuator 4a are formed in front of the wideband filter 8a that passes the reception band. Attenuation switching switches 3a and 3b are provided (see, for example, Patent Document 1), and in order to examine the electric field strength of the received wave signal, a signal is extracted from the middle of the intermediate frequency amplifier 12, An electric field strength detector 15 for detecting the level of the received wave signal based on the intermediate frequency signal is provided, and the control unit 20 includes level determining means 20b for determining the level of the received wave signal from the electric field strength detector 15. The attenuation changeover switches 3a and 3b are controlled by the linkage between the signal processing means 20d for performing a predetermined determination process based on the level and the signal processing means 20d. And a switch control means 20a for the switch control means 20a is either received wave signal from the antenna 1 passes through the attenuator 4a, or to pass through the bypass circuit 4 of the attenuator 4a.

  The operation of such a conventional receiver is such that the attenuator 4a becomes effective when the level determination means 20b determines that the level of the received wave signal exceeds a predetermined threshold (the received wave signal is attenuated). By performing switching control (passing 4a), the reception level of the radio frequency signal does not increase more than necessary.

For the receiver of a conventional cordless telephone having such a function, in an environment where there are a large number of jamming waves, in order to prevent a decrease in reception quality due to jamming waves, when the reception level is high and the level of jamming waves is also high, The gain of the high frequency stage is adjusted to attenuate the input signal level, thereby suppressing the generation of intermodulation interference waves due to the distortion of the high frequency stage.
JP-A-10-28066 JP-A-10-336068

  However, conventional cordless telephone receivers can only change the attenuation of the received wave signal, and ensure a large amount of attenuation for specific strong interference waves and interference waves in unnecessary bands. Therefore, when the level of the signal wave is large and the level of the disturbing wave is also large (for example, the disturbing wave from a microwave oven in the 2.4 GHz frequency band called ISM band), the interference input to the frequency converter 10 The wave level is increased, and the signal-to-interference wave ratio (C / IM ratio) is extremely deteriorated due to the generation of intermodulation distortion (IM) in the frequency converter 10.

  In this cordless telephone receiver, even when used in an environment with many jamming waves, the attenuation rate and band elimination component of the received frequency band are finely controlled according to the intensity of the received wave signal and the frequency component of the jamming wave, There is a demand to appropriately suppress the effects of interference.

  In order to satisfy this requirement, the present invention can finely control the attenuation rate and band elimination component of the reception frequency band according to the intensity of the reception wave signal and the frequency component of the interference wave, and is used in an environment where there are many interference waves. It is an object of the present invention to provide a receiver for a cordless telephone that can appropriately suppress the influence of an interfering wave even in the case of failure.

The receiver of the cordless telephone according to the present invention includes an attenuator switch that selects an attenuator or an attenuator bypass path disposed in front of a low-noise amplifier that amplifies a received wave signal from an antenna, a low-frequency amplifier, and an attenuation A band elimination filter for selecting a band elimination filter or a bypass path of the band elimination filter, a reception decoder for generating reception data from the demodulated signal, and an electric field for detecting the level of the reception wave signal. An intensity detector and a control unit that controls the whole; the control unit determines the level detected by the electric field intensity detector; and the received data from the reception decoder to determine the error. Error determination means for determining presence / absence, switch control means for controlling each changeover switch, processing based on determination results in the level determination means and the error determination means. And a signal processing means for sending a switch control signal to the switch control means based on the processing result. When the level of the received wave signal exceeds a predetermined level, the signal processing means passes through the switch control means. In the case where error information is transmitted in the determination of received data even though the attenuator is selected by the attenuation changeover switch and the attenuator is operated, the band removal filter is supplied to the band removal changeover switch via the switch control means. It has a configuration to select.

  This makes it possible to finely control the attenuation rate and band rejection component of the received frequency band according to the intensity of the received wave signal and the frequency component of the jamming wave, and the influence of the jamming wave even when used in an environment with many jamming waves. As a result, a cordless telephone receiver can be obtained.

  The cordless telephone of the present invention includes an attenuator switching switch that selects an attenuator disposed in front of a low-noise amplifier that amplifies a received wave signal from an antenna or a bypass path of the attenuator, and a low-frequency amplifier and an attenuator. A band elimination switch for selecting a band elimination filter or a bypass path of the band elimination filter disposed between, a reception decoder for generating reception data from the demodulated signal, and an electric field strength detector for detecting the level of the reception wave signal And a control unit that controls the whole. The control unit determines the level detected by the electric field strength detector and the received data from the receiving decoder to determine whether there is an error. Processing based on the determination results of the error determination means, the switch control means for controlling each changeover switch, the level determination means and the error determination means Both of them have signal processing means for sending a switch control signal to the switch control means based on the processing result, and the signal processing means attenuates via the switch control means when the level of the received wave signal exceeds a predetermined level. When the attenuator is selected by the changeover switch and error information is transmitted in the determination of received data even though the attenuator is operated, the band removal filter is selected for the band removal changeover switch via the switch control means. By doing so, not only the attenuation of the received wave signal is switched only by the signal strength (electric field strength) of the received wave signal, but also the attenuator is switched and the band elimination filter is switched even if there is an error in the received data. Therefore, the attenuation rate and band elimination component of the reception frequency band can be refined according to the intensity of the reception wave signal and the frequency component of the interference wave. It can be controlled, advantageous effect that the influence of the interference wave even when used on high interference wave environment can be properly suppressed can be obtained.

  In addition, a band changeover switch for selecting either the wideband filter or the plurality of narrowband filters is disposed between the low noise amplification and the band elimination filter, and the plurality of narrowband filters are arranged in the entire frequency band of the wideband filter. If the attenuator cannot obtain sufficient attenuation of the interfering wave by complementing the characteristic equivalent to that of the wideband filter by having a frequency characteristic obtained by dividing the characteristic into at least two parts, the bandpass filter can be removed along with the removal of the interfering wave by band elimination. Since the interference wave can be removed by changing the frequency characteristic, an advantageous effect that the band removal according to the frequency component of the interference wave can be precisely performed is obtained.

  Furthermore, the attenuator is composed of a plurality of attenuators selected by an attenuation switch, and the band elimination filter is composed of a plurality of band elimination filters selected by a band elimination switch, and each of the attenuators has an attenuation factor. In addition, different band elimination filters have different center frequencies for band elimination, so that the attenuation rate and band elimination component of the received frequency band can be controlled more precisely according to the intensity of the received wave signal and the frequency component of the interference wave. Therefore, even when used in an environment with many interference waves, an advantageous effect that the influence of the interference waves can be suppressed more appropriately can be obtained.

The present invention precisely controls the attenuation rate and band elimination component of the received frequency band according to the intensity of the received wave signal and the frequency component of the jamming wave, so that the influence of the jamming wave is adequate even when used in an environment with many jamming waves. If the level of the received wave signal exceeds the specified level, the attenuation changeover switch is selected via the switch control means, and the received data is judged regardless of the operation of the attenuator. In the case where error information is sent out, the band removal switching switch is made to select the band removal filter via the switch control means.

  A first invention made to solve the above-described problems is an attenuation switch that selects an attenuator or a bypass path of an attenuator arranged in a stage preceding a low-noise amplifier that amplifies a received wave signal from an antenna; A band elimination switch for selecting a band elimination filter or a bypass path of the band elimination filter disposed between the low frequency amplifier and the attenuator, a reception decoder for generating reception data from the demodulated signal, and a reception wave signal It has a field strength detector for detecting the level and a control unit for controlling the whole, and the control unit receives the level judgment means for judging the level detected by the field strength detector, and the received data from the reception decoder. Error determination means for determining whether there is an error, switch control means for controlling each changeover switch, level determination means, and error determination means And a signal processing means for sending a switch control signal to the switch control means based on the processing result, and the signal processing means performs switch control when the level of the received wave signal exceeds a predetermined level. In the case where error information is transmitted in the determination of received data even though the attenuator is selected via the means and the attenuator is operated, the band removal changeover switch is switched via the switch control means. The band elimination filter is selected and not only the attenuation of the received wave signal is switched only by the signal strength (electric field strength) of the received wave signal but also the presence or absence of an error in the received data. Since the switching and switching of the band elimination filter can be performed, the reception frequency band depends on the intensity of the received wave signal and the frequency component of the interference wave. The decay rate and bandwidth component removed can be controlled finely, having operations and effects of the influence of the interference wave even when used on high interference wave environment can be properly suppressed.

  A second invention made to solve the above-mentioned problem is that a band changeover switch for selecting either a wideband filter or a plurality of narrowband filters is disposed between the low noise amplification and the band elimination filter, The narrow-band filter has a frequency characteristic obtained by dividing the entire characteristic of the frequency band of the wide-band filter by at least two, and complements the characteristic equivalent to the wide-band filter. Cannot be obtained, the interference wave can be removed by changing the frequency characteristics of the band filter together with the removal of the interference wave by removing the band, so that the band removal according to the frequency component of the interference wave can be performed finely. It has the action and effect.

  According to a third aspect of the present invention, the attenuator is composed of a plurality of attenuators selected by an attenuation switching switch, and the band elimination filter is a plurality of band eliminations selected by a band elimination switching switch. The filter is composed of a plurality of attenuators having different attenuation rates and a plurality of band elimination filters having different band elimination center frequencies, depending on the intensity of the received wave signal and the frequency component of the interference wave. Since the attenuation rate and band elimination component of the reception frequency band can be controlled more precisely, even when used in an environment where there are many interference waves, the effect of the interference waves can be suppressed more appropriately.

(Embodiment 1)
FIG. 1 is a block diagram showing a receiver of a cordless telephone according to Embodiment 1 of the present invention.

In FIG. 1, antenna 1, antenna switch 2, attenuation switch 3a, 3b, bypass circuit 4, attenuator 4a, broadband filter 8a, low noise amplifier 9, frequency converter (receiver mixer) 10, local oscillator 11, intermediate The frequency amplifier 12, the demodulator 13, the electric field strength detector 15, the reception decoder 16, the control unit 20, the switch control unit 20a, the level determination unit 20b, the error determination unit 20c, and the signal processing unit 20d have the same configuration as in FIG. The description is omitted. Reference numerals 5a and 5b denote band elimination filters for selecting a later-described band elimination filter 6a or a later-described bypass circuit 6 as a receiving system, 6a is a band elimination filter for removing a frequency component of a certain band from the input signal, and 6 is a band. This is a bypass circuit that bypasses the removal filter 6a.

  The operation of the receiver of the cordless telephone configured as described above will be described.

  The received wave signal transmitted and received from the communication partner (master unit or slave unit) passes through the antenna 1 and the antenna switch 2 (the operation to the transmitting side opposite to the antenna switch 2 needs to be explained in particular). Therefore, when the attenuation changeover switches 3a and 3b select the bypass circuit 4 that bypasses the attenuator 4a, the received wave signal is not attenuated and proceeds to the next stage. When the bypass circuit 6 to be bypassed is selected and the bypass circuit 6 to be bypassed is selected, the received wave signal is similarly guided to the next stage without being attenuated, and necessary reception is performed according to the characteristics of the wideband filter 8a. After the received wave signal of the bandwidth passes, it is amplified by the low noise amplifier 9. The received wave signal amplified by the low noise amplifier 9 is converted into an intermediate frequency signal by the reception mixer 10, then amplified by the intermediate frequency amplifier 12, demodulated by the demodulator 13, and a demodulated signal 14 is obtained. The demodulated signal 14 is reproduced by the reception decoder 16 into the same reception data 18 as the transmission data transmitted from the communication partner. The intensity of the received wave signal passing through the intermediate frequency amplifier 12 is detected by an electric field intensity detector (RSSI) 15, and the detection signal of the electric field intensity detector 15 is sent to the level determining means 20b, and the level is determined according to the signal intensity. The means 20b performs signal strength determination. When the signal level exceeds a predetermined level, the signal processing means 20d switches the attenuation changeover switches 3a and 3b to the attenuator 4a to operate the attenuator 4a, and the received wave signal Is attenuated by a predetermined amount, and the level of the received wave signal input to the frequency converter 10 is lowered.

  By lowering the level of the received wave signal in this way, the level of the disturbing wave input to the frequency converter 10 is similarly lowered. Therefore, by setting in this way, when the level of the received wave signal is large and the level of the disturbing wave is also large, the receiving mixer 10 does not increase the output saturation distortion point (called the intercept point) of the receiving mixer 10. The generated intermodulation distortion (IM) component can be reduced, and the signal-to-interference ratio can be reduced.

  Further, the CRC data included in the received data 18 reproduced by the receiving decoder 16 is determined by the error determining means 20c in the control unit 20 in spite of the operation of the attenuator 4a. When it is determined that the signal is being transmitted, the signal processing means 20d in the control unit 20 links the switch control means 20a so that the band removal switching switches 5a and 5b are switched to the band removal filter 6a. Powerful interference waves (for example, interference waves having a microwave frequency in the 2.4 GHz band) can be eliminated.

  As described above, the receiver of the cordless telephone according to the present embodiment can reduce the gain at the high frequency stage of the received wave signal by attenuating the interfered wave signal together with the received received wave signal. Gain can be reduced.

  If the received electric field strength level is lower than the predetermined level and the CRC data included in the received data 18 is determined by the error determination means 20c in the control unit 20 and error information is transmitted, the attenuator The error can be minimized by switching to a narrow band filter first without operating 4a.

As described above, according to the present embodiment, when the level of the received wave signal exceeds the predetermined level, the signal processing unit 20d is connected to the attenuation changeover switch 3a via the switch control unit 20a.
If error information is transmitted in the determination of received data even though the attenuator 4a is selected by 3b and the attenuator 4a is operated, the band removal change-over switches 5a and 5b are switched via the switch control means 20a. By selecting the band elimination filter 6a, not only the attenuation amount of the received wave signal is switched only by the signal strength (electric field strength) of the received wave signal, but also the attenuator switching and the band depending on whether there is an error in the received data. Since the removal filter can be switched, the attenuation rate and band rejection component of the reception frequency band can be finely controlled according to the intensity of the reception wave signal and the frequency component of the interference wave. Even when it is used, the influence of the interference wave can be appropriately suppressed.

(Embodiment 2)
FIG. 2 is a block diagram showing a receiver of a cordless telephone according to Embodiment 2 of the present invention.

  In FIG. 2, antenna 1, antenna switch 2, attenuation switch 3a, 3b, bypass circuit 4, attenuator 4a, band rejection switch 5a, 5b, band rejection filter 6a, bypass circuit 6, broadband filter 8a, low noise Amplifier 9, frequency converter 10, local oscillator 11, intermediate frequency amplifier 12, demodulator 13, field strength detector 15, reception decoder 16, control unit 20, switch control means 20a, level determination means 20b, error determination means 20c, The signal processing means 20d has the same configuration as that shown in FIG. 7a and 7b are band changeover switches for switching between the wideband filter 8a and the narrowband filters 8b and 8c described later. "Narrowband filter").

  The operation of the receiver of the cordless telephone configured as described above will be described.

  The frequency band of the wideband filter 8a has all the characteristics of the reception frequency range necessary for communication, and the narrowband filters 8b and 8c have characteristics that can divide and supplement all the characteristics of the wideband filter 8a. By using 7a and 7b, narrow band filters 8b and 8c are selected instead of the normally selected wide band filter 8a, so that a characteristic equivalent to that of the wide band filter 8a is obtained.

  In the receiver having this configuration, the reception data reproduced by the reception decoder 16 is selected by the band changeover switches 7a and 7b in spite of the selection of the band removal filter 6a by the band removal changeover switches 5a and 5b in the operation shown in the first embodiment. 18 is determined by the error determination unit 20c in the control unit 20 and when it is determined that the error information is transmitted, the switch control unit 20a is linked by the signal processing unit 20d in the control unit 20. By selecting the narrow band filter 8b or 8c that is closest to the frequency band of the received wave signal for the band changeover switches 7a and 7b, interference waves other than the designated narrow band filter can be eliminated. As in the first embodiment, the intermodulation distortion (IM) component generated in the receiving mixer 10 is reduced. Bets can be, it is possible to reduce the signal-to-interference wave ratio.

  As described above, according to the present embodiment, the band changeover switches 7a and 7b for selecting either the wideband filter 8a or the plurality of narrowband filters 8b and 8c are provided between the low noise amplifier 9 and the band elimination filter 6a. The plurality of narrowband filters 8b and 8c have a frequency characteristic obtained by dividing the entire characteristic of the frequency band of the wideband filter 8a by at least two, and complement the characteristic equivalent to the wideband filter 8a, thereby attenuating the attenuator 4a. If sufficient attenuation of the interference wave cannot be obtained, the interference wave can be removed by changing the frequency characteristics of the band filter along with the removal of the interference wave by removing the band. Can be performed in detail.

(Embodiment 3)
FIG. 3 is a block diagram showing a receiver of a cordless telephone according to Embodiment 3 of the present invention.

  In FIG. 3, antenna 1, antenna switch 2, attenuation switch 3a, 3b, bypass circuit 4, attenuator 4a, band removal switch 5a, 5b, band removal filter 6a, bypass circuit 6, band switch 7a, 7b , Wideband filter 8a, narrowband filters 8b and 8c, low noise amplifier 9, frequency converter 10, local oscillator 11, intermediate frequency amplifier 12, demodulator 13, field strength detector 15, reception decoder 16, control unit 20, switch The control unit 20a, the level determination unit 20b, the error determination unit 20c, and the signal processing unit 20d have the same configuration as that shown in FIG. 4b is an attenuator having a multistage configuration with the attenuator 4a, and 6b is a band rejection filter having a multistage configuration with the band elimination filter 6a. The changeover switches 3a, 3b, 5a, and 5b are two-stage switching in FIGS. 1 and 2, but are three-stage switching in the present embodiment. That is, in FIG. 3, the attenuators 4a and 4b are used to make the attenuators multistage, and the attenuation changeover switches 3a and 3b for selecting the bypass circuit 4 of the attenuators 4a and 4b are different from the center frequency of the band elimination filter. Band elimination filters 6a and 6b are provided so that the filter can be selected, and band elimination switching switches 5a and 5b for selecting the bypass circuit 6 are provided.

  The attenuators 4a and 4b can be further multi-staged. The number of the attenuators 4a and 4b can be increased to 4c, 4d, 4n, etc., and the number of switching stages of the attenuation changeover switches 3a and 3b can be increased accordingly. The amount of attenuation is such that the insertion loss can be increased in the order of A1 <A2 <A3... <An if the attenuator 4a is A1, the attenuator 4b is A2, and the attenuator 4c is A3. Set to be. The band elimination filters 6a and 6b can be further multistaged, and the band elimination filters 6c... 6n having different center frequencies can be used, and the number of switching stages of the band elimination switching switches 5a and 5b can be increased accordingly. Like that. Thereby, for example, powerful interference waves such as microwave ovens having different oscillation frequencies can be reduced. In the present embodiment, as a representative example, an example in which one stage of bypass, an attenuator, and a band elimination filter are switched in two stages, and each of the changeover switches 3a, 3b, 5a, and 5b is in three stages is illustrated. .

  The operation of the receiver of the cordless telephone configured as described above will be described.

  In the receiver having this configuration, thresholds (predetermined levels) in the level determination means 20b are provided as A, B, and C, and have a determination level according to switching of the attenuation changeover switches 3a and 3b of the attenuators 4a and 4b. The operation is the same as in the first embodiment, the level of the received wave signal can be finely reduced according to the strength of the received wave signal, and the intermodulation distortion (IM) component generated in the frequency converter 10 is made smaller. Will be able to.

  Even when the attenuator is switched, the CRC data included in the received data 18 reproduced by the receiving decoder 16 is determined by the error determining means 20c in the control unit 20 and it is determined that the error information is transmitted. The signal processing means 20d in the control unit 20 links the switch control means 20a, and the narrow band filter 8b or 8c closest to the band of the received wave signal frequency by the band changeover switches 7a and 7b as in the second embodiment. By selecting, it is possible to eliminate interfering waves other than the designated narrowband filter, and to reduce the intermodulation distortion (IM) component generated in the frequency converter 10 as in the first embodiment. And the signal-to-interference ratio can be reduced.

Further, although the attenuator and the band filter are switched, the CRC data included in the reception data 18 reproduced by the reception decoder 16 is converted into error determination means 20 in the control unit 20.
When it is determined by c that it is determined that the error information is transmitted, the signal processing means 20d in the control unit 20 links the switch control means 20a, and the band removal changeover switch 5a and The band elimination filter can be selected by switching 5b. At this time, the number of switching stages is the same as the number of band elimination filters, and an appropriate band elimination filter 6a or 6b is selected according to the frequency at which the error of the received wave signal occurs. Since this embodiment is an example having two different types of band elimination filters 6a and 6b, if there is a predicted frequency of a strong jamming radio wave at any other frequency, the band elimination filter according to that frequency. It is possible to easily reduce the jamming radio wave simply by additionally arranging.

  As described above, according to the present embodiment, the attenuator is composed of a plurality of attenuators selected by the attenuation changeover switches 3a and 3b, and the band elimination filter is selected by the plurality of band elimination changeover switches 5a and 5b. The multiple attenuators have different attenuation factors, and the multiple band-reject filters have different band-removal center frequencies, so that they can be received according to the intensity of the received wave signal and the frequency component of the interference wave. Since the attenuation factor and the band removal component of the frequency band can be controlled more precisely, even when used in an environment with a lot of interference waves, the influence of the interference waves can be suppressed more appropriately.

  The present invention relates to a receiver of a cordless telephone in which there are many interference waves such as an ISM frequency band and the frequency band to be used is easily affected by a nearby frequency band. Accordingly, it is possible to finely control the attenuation rate and band removal component of the reception frequency band according to the above, and even when used in an environment with many jamming waves, the influence of the jamming waves can be appropriately suppressed.

1 is a block diagram showing a receiver of a cordless telephone according to Embodiment 1 of the present invention. Block diagram showing a receiver of a cordless telephone according to a second embodiment of the present invention Block diagram showing a receiver of a cordless telephone according to a third embodiment of the present invention Block diagram showing a conventional cordless telephone receiver

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Antenna switching device 3a, 3b Attenuation switching switch 4, 6 Bypass circuit 4a, 4b Attenuator 5a, 5b Band elimination switching switch 6a, 6b Band elimination filter 7a, 7b Band switching switch 8a Wide band filter 8b, 8c Narrow band filter DESCRIPTION OF SYMBOLS 9 Low noise amplifier 10 Frequency converter 11 Local oscillator 12 Intermediate frequency amplifier 13 Demodulator 15 Electric field strength detector 16 Reception decoder 20 Control part 20a Switch control means 20b Level judgment means 20c Error judgment means 20d Signal processing means

Claims (3)

An attenuator disposed in front of a low noise amplifier for amplifying a received wave signal from an antenna or an attenuation changeover switch for selecting a bypass path of the attenuator, and disposed between the low frequency amplifier and the attenuator A band elimination changeover switch that selects a bypass path of the band elimination filter that has been performed, a reception decoder that generates reception data from a demodulated signal, an electric field strength detector that senses a level of the reception wave signal, A control unit for controlling the whole,
The control unit includes a level determination unit that determines a level detected by the electric field strength detector, an error determination unit that determines reception data from the reception decoder and determines whether there is an error, and each of the changeover switches. And a signal processing means for performing a process based on the determination results of the level determination means and the error determination means and sending a switch control signal to the switch control means based on the processing results. ,
When the level of the received wave signal exceeds a predetermined level, the signal processing means causes the attenuation changeover switch to select the attenuator via the switch control means and operates the attenuator. A receiver for a cordless telephone, characterized in that, when error information is transmitted in the determination of the received data, the band elimination filter is selected by the band elimination switching switch via the switch control means. A band changeover switch for selecting either a wideband filter or a plurality of narrowband filters is disposed between the low noise amplification and the band elimination filter, and the plurality of narrowband filters includes a frequency band of the wideband filter. The receiver of a cordless telephone according to claim 1, wherein the receiver has a frequency characteristic obtained by dividing at least two of said characteristics, and complements a characteristic equivalent to the broadband filter. The attenuator is composed of a plurality of attenuators selected by the attenuation switching switch, and the band elimination filter is composed of a plurality of band elimination filters selected by the band elimination switching switch, and the plurality of attenuators are The cordless telephone receiver according to claim 1 or 2, wherein the attenuation factor is different, and the plurality of band elimination filters have different band elimination center frequencies.

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