Control device, frequency control method, and receiving device

A control device of a receiving device includes an interference wave detector that detects an interference wave within an intermediate frequency band in a signal converted by a mixer that converts a reception signal of a radio frequency band with a certain radio frequency as a center into an intermediate signal of the intermediate frequency band based on a signal of a local oscillation frequency different from the radio frequency. The control device further includes a frequency controller that changes the local oscillation frequency so that the intermediate frequency band gets away from a band of the interference wave when the interference wave is detected.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent application No. 2013-58519, filed on Mar. 21, 2013, the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates to a control device, a frequency control method, and a receiving device.

BACKGROUND

Receiving devices that receive a radio signal of a radio frequency band with a radio frequency received through an antenna as a center have been known. For example, this type of receiving device includes a local oscillator that generates a local signal of a local frequency different from a radio frequency and a mixer that converts a radio signal received through an antenna into an intermediate signal of an intermediate frequency band based on the local signal. The receiving device further includes a filter that attenuates a signal outside the intermediate frequency band in the signal converted by the mixer at a stage subsequent to the mixer.

There are cases in which the antenna receives an interference wave of a band near the radio signal together with the radio signal. In this case, the mixer converts the radio signal into an intermediate signal IS1, and converts the interference wave into an interference wave IW1of a band near the intermediate frequency band as illustrated inFIG. 1(A). However, the filter gradually decreases in transmissivity as it gets away from the intermediate frequency band as indicated by an alternate long and short dash line FL1. Here, the transmissivity refers to a ratio of a level of a signal output from the filter to a level of a signal input to the filter.

Thus, it is difficult for the filter to sufficiently attenuate a signal of a band FW1which is outside the intermediate frequency band but near the intermediate frequency band. As a result, the intermediate interference wave IW1passes through the filter without being sufficiently attenuated.

In this regard, for example, a technique in which a receiving device detects a band of an intermediate interference wave, and changes a local frequency based on the detected band so that an intermediate interference wave IW1has a band FW2which is sufficiently attenuated by the filter as illustrated inFIG. 1(B) (e.g., see Japanese Laid-open Patent Publication No. 11-186923). As a result, the intermediate interference wave IW1can be sufficiently attenuated by the filter.

Further, notch filters that attenuate a signal within a certain removal band have been known (e.g., see Japanese Laid-open Patent Publication No. 04-360441 and Japanese Laid-open Patent Publication No. 2004-336715).

Meanwhile, for example, there are cases in which the interference wave within the intermediate frequency band received by the antenna reaches the side subsequent to the mixer without undergoing frequency conversion by the mixer, or cases in which the interference wave within the intermediate frequency band comes into the receiving device at the side subsequent to the mixer, for example, due to an insufficient separation (isolation) between two signals input to the mixer or characteristics of circuit elements. In this case, it is difficult to change the band of the interference wave even when the local frequency is changed as in the above-described receiving device. Particularly, when a housing made of a material such as synthetic resin is used in order to lighten the receiving device, the interference wave is hardly attenuated due to the housing, and thus this problem becomes more remarkable.

In this regard, the interference wave is considered to be sufficiently attenuated using the notch filter. In this case, however, since the intermediate signal as well as the interference wave is attenuated, the quality of a reception signal deteriorates. In this manner, the above-described receiving device has a problem in that the quality of a reception signal deteriorates.

SUMMARY

According to an aspect of an embodiment, a control device includes an interference wave detector that detects an interference wave within an intermediate frequency band in a signal converted by a mixer that converts a reception signal of a radio frequency band with a certain radio frequency as a center into an intermediate signal of the intermediate frequency band based on a signal of a local oscillation frequency different from the radio frequency. The control device further includes a frequency controller that changes the local oscillation frequency so that the intermediate frequency band gets away from a band of the interference wave when the interference wave is detected.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, in order to solve at least one of the above-mentioned problems, exemplary embodiments of a control device, a frequency control method, and a receiving device according to the present invention will be described with reference toFIGS. 2 to 12.

A transceiving device according to a first embodiment includes an oscillator and a mixer. The oscillator generates a local signal of a local oscillation frequency different from a certain radio frequency. The mixer converts a reception signal of a radio frequency band with a radio frequency as a center into an intermediate signal of an intermediate frequency band based on the generated local signal.

Further, the transceiving device includes an interference wave detector that detects an interference wave within the intermediate frequency band in the signal converted by the mixer and a frequency controller that changes the local oscillation frequency so that the intermediate frequency band gets away from a band of the interference wave when the interference wave is detected.

According to the above configuration, it is possible to cause the intermediate frequency band to get away from the band of the interference wave. Through this operation, it is possible to easily separate the signal within the intermediate frequency band from the interference wave. As a result, the quality of a reception signal can be increased.

Hereinafter, the transceiving device according to the first embodiment will be described in detail.

A transceiving device1according to the first embodiment includes an antenna11, a duplexer12, a transmitting unit13, and a receiving unit14as illustrated inFIG. 2. The transceiving device1is connected to a base band (BB) device2. The transceiving device1is an example of a receiving device.

The BB device2generates a base band signal, and outputs the generated base band signal to the transceiving device1. The base band signal is a signal of a certain base band. The BB device2receives the base band signal output from the transceiving device1, and performs a certain base band process based on the received base band signal.

The antenna11receives a radio signal of a radio frequency band with a radio frequency FRFas a center. In the present example, the radio signal is transmitted from a wireless terminal (not illustrated). In the present example, the radio frequency band is a band having a frequency higher than the base band. The antenna11outputs the received radio signal to the receiving unit14through the duplexer12.

Further, the antenna11receives a radio signal output from the transmitting unit13through the duplexer12, and transmits the received radio signal.

The duplexer12is also called a duplexer. The duplexer12performs switching between a function of transmitting the radio signal and the function of receiving the radio signal. The duplexer12may have a function of removing a signal of a band other than the radio frequency band.

The transmitting unit13generates a radio signal based on the base band signal input from the BB device2, and outputs the generated radio signal to the antenna11through the duplexer12.

The receiving unit14includes a first amplifier101, a local oscillator102, a mixer103, a second amplifier104, a first filter105, an analog to digital converter (ADC)106, a digital down converter (DDC)107, a second filter108, a digital gain controller (DGC)109, an interface (IF)110, an interference wave detector111, and a frequency controller112. The interference wave detector111, the frequency controller112, the DDC107, and the second filter108are an example of a control device.

In the present example, the DDC107, the second filter108, the DGC109, the interference wave detector111, and the frequency controller112may be configured with a field-programmable gate array (FPGA). Alternatively, the DDC107, the second filter108, the DGC109, the interference wave detector111, and the frequency controller112may be configured with a programmable logic device (PLD) rather than the FPGA.

Further, the DDC107, the second filter108, the DGC109, the interference wave detector111, and the frequency controller112may be configured with a logic device which cannot be programmable (e.g., an application specific integrated circuit (ASIC)). Further, the transceiving device1may be configured to include a computer provided with a processing device and a storage device storing a program (software), and the respective functions of the DDC107, the second filter108, the DGC109, the interference wave detector111, and the frequency controller112may be implemented as the program is executed by the processing device.

The first amplifier101amplifies the radio signal received through the antenna11. In the present example, the first amplifier101is a low noise amplifier (LNA).

The local oscillator102generates a local signal of a local frequency (local oscillation frequency) FLOdifferent from the radio frequency FRF. In the present example, the local signal is an alternating current (AC) signal of a continuous wave. In the present example, the local frequency FLOis a frequency lower than the radio frequency FRF. For example, the local oscillator102generates a local signal of a frequency represented by a first frequency control signal output from the frequency controller112as the local frequency FLO.

The mixer103is also called a mixer. The mixer103converts the radio signal amplified by the first amplifier101into an intermediate signal of an intermediate frequency band based on the local signal generated by the local oscillator102. In the present example, the mixer103is a mixer of a heterodyne type. In the present example, the intermediate frequency band is a frequency band which is higher than the base band but lower than the radio frequency band. In the present example, the mixer103converts the signal amplified by the first amplifier101so that the frequency thereof is lowered by the local frequency FLO.

The second amplifier104amplifies the signal converted by the mixer103, and outputs the amplified signal to the first filter105.

The first filter105is configured to attenuate a signal outside a first passband among the signals which are output from the second amplifier104(i.e., the signals converted by the mixer103). The first passband has a band width larger than the width of the intermediate frequency band (the intermediate frequency band width). For example, the width of the first passband (the first passband width) WFP1is preferably set to satisfy a condition represented by Mathematical Formula 1:
WIS+WIW≦WFP1≦2WIS+WIW(Mathematical Formula 1)

Here, WISrepresents the intermediate frequency band width. WIWrepresents a width of a band (band width) of the interference wave.

In the present example, the first passband width WFP1is set to a value (i.e., 2WIS) which is twice as large as the intermediate frequency band width as illustrated inFIG. 3. A lower limit of the first passband is set to a value (i.e., FIS0−WIS/2) obtained by subtracting a value which is half the intermediate frequency band width WISfrom a basic intermediate frequency FIS0. The basic intermediate frequency FIS0is a basic value of an intermediate frequency FIS. The intermediate frequency FISis the center frequency of the intermediate frequency band.

In this specification, in the receiving unit14, a direction from the first amplifier101to the IF110is referred to as a backward direction, and a direction from the IF110to the first amplifier101is referred to as a forward direction. In other words, the first filter105is arranged at the side subsequent to (behind) the mixer103.

The ADC106converts the signal that has passed through the first filter105from an analog signal into a digital signal, and outputs the converted signal to the DDC107.

The DDC107converts the signal output from the ADC106(i.e., the signal that has passed through the first filter105) so that the frequency thereof is lowered by a frequency reduction amount ΔFRD(i.e., performs down conversion). In the present example, the DDC107includes a numerical controlled oscillator (NCO).

The frequency reduction amount ΔFRDis set to the difference (in the present example, a value (=FIS−FBB) obtained by subtracting a base frequency FBBfrom the intermediate frequency FIS) between the intermediate frequency FISand the base frequency FBB. The base frequency FBBis the center frequency of the base band. In other words, the DDC107converts the signal that has passed through the first filter105so that the intermediate signal of the intermediate frequency band is converted into the base band signal of the base band.

For example, the DDC107converts the signal so that the frequency thereof is lowered by the frequency reduction amount ΔFRDrepresented by a second frequency control signal output from the frequency controller112. As will be described later, the frequency reduction amount ΔFRDis set to a value (=FRF−FLO−FBB) obtained by subtracting the base frequency FBBfrom a value obtained by subtracting the local frequency FLOfrom the radio frequency FRF. Meanwhile, the value obtained by subtracting the local frequency FLOfrom the radio frequency FRFis equal to the intermediate frequency FIS. Thus, the frequency reduction amount ΔFRDis set to a value (=FIS−FBB) obtained by subtracting the base frequency FBBfrom the intermediate frequency FIS.

The DDC107outputs the converted signal to the second filter108.

As described above, the DDC107converts the signal that has passed through the first filter105based on the local frequency FLOso that the frequency thereof changes by the difference between the intermediate frequency FISand the base frequency FBB.

In the present example, the DDC107is an example of a frequency converter.

The second filter108is configured to attenuate a signal outside a second passband in the signal output from the DDC107(i.e., the signal converted by the DDC107). The second passband is approximately identical to the base band. In other words, the second passband has the band width approximately equal to the width of the base band (the base band width). Further, the center frequency of the second passband is approximately identical to the base frequency FBB. The second filter108is arranged at the side subsequent to (behind) the DDC107.

The DGC109adjust a level of the signal that has passed through the second filter108to have a level within a previously set level range, and outputs the adjusted signal to the IF110.

The IF110converts the signal output from the DGC109to have a certain format (in the present example, a common packet radio interface (CPRI) format), and outputs the converted signal (the base band signal) to the BB device2.

The interference wave detector111detects the interference wave within the intermediate frequency band in the signal that has passed through the second filter108(i.e., the signal converted by the mixer103). For example, the interference wave detector111includes a window function processor201, an FFT processor202, a power calculator203, an average power calculator204, a threshold power calculator205, and an interference wave specifier206as illustrated inFIG. 4.

The window function processor201performs a process of multiplying the signal that has passed through the second filter108by a window function in units of certain signal blocks. The signal blocks are generated by dividing the signal in units of certain time intervals (in units of certain time frames).

The FFT processor202performs Fourier transform (in the present example, fast Fourier transform (FFT)) on the signal processed by the window function processor201in units of signal blocks.

The power calculator203calculates power of each frequency for each signal block based on data of a real part and data of an imaginary part (IQ data) of the signal which has been subjected to Fourier transform by the FFT processor202.

The average power calculator204calculates an average power value of each frequency obtained by averaging the powers of frequencies calculated by the power calculator203for a plurality of signal blocks (in the present example, 16 signal blocks).

The threshold power calculator205calculates a reference value by averaging average power values obtained by excluding a certain exclusion number (in the present example, 64) from the average power values of the respective frequencies calculated by the average power calculator204in the descending order of the values. Further, the threshold power calculator205calculates a value obtained by adding a certain marginal value to the calculated reference value as interference wave threshold power.

The interference wave specifier206determines whether at least one of the average power values of the respective frequencies calculated by the average power calculator204is larger than the threshold power calculated by the threshold power calculator205. In the present example, when at least one of the average power values of the respective frequencies is larger than the threshold power, for example, it means that the interference wave within the intermediate frequency band is detected in the signal.

When the interference wave within the intermediate frequency band is detected in the signal, the interference wave specifier206outputs interference wave information representing an average power value (interference wave power) larger than the threshold power among the calculated average power values of the respective frequencies and the frequency (interference wave frequency) corresponding to the average power value to the frequency controller112. In the present example, the interference wave specifier206does not output the interference wave information when the interference wave within the intermediate frequency band is not detected in the signal. Further, when the interference wave within the intermediate frequency band is not detected in the signal, the interference wave specifier206may output null information or information representing that the interference wave has not been detected to the frequency controller112as the interference wave information.

When the interference wave is detected by the interference wave detector111, the frequency controller112changes the local frequency FLOso that the intermediate frequency band gets away from the band of the interference wave. For example, the frequency controller112changes the local frequency FLOso that the intermediate frequency band is arranged outside the band of the interference wave.

Further, in the present example, the frequency controller112changes the local frequency FLOso that the intermediate frequency band gets away from the band of the interference wave within the first passband.

For example, the frequency controller112selects the local frequency FLOin a range from a lower limit value Fthto a basic local frequency FLO0based on the interference wave information output from the interference wave detector111. In the present example, the basic local frequency FLO0is a value (=FRF−FIS0) obtained by subtracting the basic intermediate frequency FIS0from the radio frequency FRF.

The lower limit value Fthis preferably set so that the frequency band (i.e., the intermediate frequency band) of the intermediate signal converted by the mixer103be included within the first passband of the first filter105. In the present example, the lower limit value Fthis a local frequency with which the intermediate frequency of the intermediate signal converted by the mixer103becomes the upper limit frequency FIS1. Here, the upper limit frequency FIS1is a value (=FIS0+WIS) obtained by adding the intermediate frequency band width WISto the basic intermediate frequency FIS0as illustrated inFIG. 3. In other words, the lower limit value Fthis a value (=FLO0−WIS) obtained subtracting the intermediate frequency band width WISfrom the basic local frequency FLO0.

When there is a local frequency with which a representative interference wave power is smaller than a certain permissible power, the frequency controller112selects the corresponding local frequency. The representative interference wave power is a representative value of the interference wave power. In the present example, the representative interference wave power is a maximum value of the interference wave power. Alternatively, the representative interference wave power may be an average value of the interference wave power.

Meanwhile, when there is no local frequency with which a representative interference wave power is smaller than the permissible power, the frequency controller112selects the local frequency which minimizes the representative interference wave power.

The frequency controller112outputs the first frequency control signal representing the selected local frequency FLOto the local oscillator102.

Further, the frequency controller112calculates a value (=FRF−FLO−FBB) obtained by subtracting the base frequency FBBfrom a value obtained from subtracting the selected local frequency FLOfrom the radio frequency FRFas the frequency reduction amount ΔFRD. In addition, the frequency controller112outputs the second frequency control signal representing the calculated frequency reduction amount ΔFRDto the DDC107.

Next, an operation of the transceiving device1will be described with reference toFIGS. 5 and 6.

The frequency controller112performs a frequency control process illustrated inFIG. 5at a certain timing. In the present example, the frequency controller112performs the frequency control process when the transceiving device1is activated. Further, the frequency controller112may perform the frequency control process each time when a certain execution period elapses or when the representative interference wave power is larger than a certain execution threshold value.

First of all, when execution of the frequency control process starts, the frequency controller112sets (selects) the basic local frequency FLO0as the local frequency FLO(step S101ofFIG. 5). Then, the frequency controller112outputs the first frequency control signal representing the selected local frequency FLOto the local oscillator102, and outputs the second frequency control signal representing the frequency reduction amount ΔFRD(=FRF−FLO0−FBB) to the DDC107(step S102ofFIG. 5).

Through this operation, the local oscillator102generates the local signal of the local frequency FLO(=FLO0) represented by the first frequency control signal. Further, the DDC107changes the signal so that the frequency thereof is lowered by the frequency reduction amount ΔFRD(=FRF−FLO0−FBB) represented by the second frequency control signal.

Thereafter, the mixer103converts the radio signal received by the antenna11into the intermediate signal based on the local signal generated by the local oscillator102. In other words, the mixer103changes a signal SRF amplified by the first amplifier101so that the frequency thereof is lowered by the local frequency FLO(=FLO0) as illustrated inFIG. 6A. Through this operation, the signal SRF of the radio frequency band is converted into an intermediate signal SIS of an intermediate frequency band with the intermediate frequency FIS(=FRF−FLO0) as the center.

Then, the DDC107converts the signal so that the frequency thereof is lowered by the frequency reduction amount ΔFRD(=FRF−FLO0−FBB) represented by the second frequency control signal. Through this operation, the intermediate signal SIS of the intermediate frequency band is converted into a base band signal SBB of a base band with the base frequency FBBas the center.

Further, the interference wave detector111detects the interference wave within the intermediate frequency band in the signal converted by the mixer103.

When the interference wave information is output from the interference wave detector111, the frequency controller112acquires the representative interference wave power based on the interference wave information. Meanwhile, when the interference wave information is not output from the interference wave detector111, the frequency controller112acquires “0” as the representative interference wave power (step S103ofFIG. 5).

In the present example, the interference wave SIW within the intermediate frequency band is assumed to be detected in the signal converted by the mixer103as illustrated inFIG. 6A.

The frequency controller112stores the acquired representative interference wave power and the local frequency FLOat the current point in time in association with each other (step S104ofFIG. 5). Next, the frequency controller112determines whether the acquired representative interference wave power is larger than the permissible power (step S105ofFIG. 5).

Here, the representative interference wave power is assumed to be larger than the permissible power. In this case, the frequency controller112determines “Yes,” and updates the local frequency FLObased on a value obtained by subtracting a certain frequency change amount α from the local frequency FLOat the current point in time (step S106ofFIG. 5). In the present example, the frequency change amount α has a positive value.

Then, the frequency controller112outputs the first frequency control signal representing the updated local frequency FLO(=FLO0−α) to the local oscillator102, and outputs the second frequency control signal representing the frequency reduction amount ΔFRD(=FR−FLO0+α−FBB) to the DDC107(step S107ofFIG. 5).

Through this operation, the local oscillator102generates the local signal of the local frequency FLO(=FLO0−α) represented by the first frequency control signal. Further, the DDC107converts the signal so that the frequency thereof is lowered by the frequency reduction amount ΔFRD(=FRF−FLO0+α−FBB) represented by the second frequency control signal.

Thereafter, the mixer103converts the radio signal received by the antenna11into the intermediate signal based on the local signal generated by the local oscillator102. In other words, the mixer103converts the signal SRF amplified by the first amplifier101so that the frequency thereof is lowered by the local frequency FLO(=FLO0−α) as illustrated inFIG. 6B. Through this operation, the signal SRF of the radio frequency band is converted into the intermediate signal SIS of the intermediate frequency band with the intermediate frequency FIS(=FRF−FLO0+α) as the center.

In this way, the frequency controller112changes the local frequency FLOso that the intermediate frequency band of the intermediate signal SIS gets away from the band of the interference wave SIW within the first passband PB1as illustrated inFIGS. 6A and 6B. In other words, a phenomenon that the state in which the intermediate frequency band of the intermediate signal SIS overlaps the band of the interference wave SIW changes to the state in which the intermediate frequency band does not overlap the band of the interference wave SIW is an example in which the intermediate frequency band gets away from the band of the interference wave SIW.

Then, the DDC107converts the signal so that the frequency is lowered by the frequency reduction amount ΔFRD(=FRFFLO0+α−FBB) represented by the second frequency control signal. Through this operation, the intermediate signal SIS of the intermediate frequency band is converted into the base band signal SBB of the base band with the base frequency FBBas the center.

Thereafter, the frequency controller112determines whether the local frequency FLOat the current point in time is smaller than the lower limit value Fth(step S108ofFIG. 5). Here, the local frequency FLOis assumed to be equal to or larger than the lower limit value Fth. In this case, the frequency controller112determines “No,” returns to step S103, and repeatedly performs the process of steps S103to S108.

Through this operation, the case in which the representative interference wave power becomes equal to or lower than the permissible power before the local frequency FLObecomes smaller than the lower limit value Fthis considered. In this case, when the frequency controller112proceeds to step S105ofFIG. 5, the frequency controller112determines “No,” and ends the frequency control process ofFIG. 5.

Next, the case in which the local frequency FLObecomes smaller than the lower limit value Fthbefore the representative interference wave power becomes equal to or lower than the permissible power is considered. In this case, when the process proceeds to step S108ofFIG. 5, the frequency controller112determines “Yes,” and acquires a minimum interference wave frequency FLOminfrom the local frequency stored in step S104(step S109ofFIG. 5). The minimum interference wave frequency FLOminis a local frequency stored in association with the minimum representative interference wave power.

Then, the frequency controller112sets (selects) the acquired minimum interference wave frequency FLOminas the local frequency FLO(step S110ofFIG. 5). Next, the frequency controller112outputs the first frequency control signal representing the selected local frequency FLO(=FLOmin) to the local oscillator102, and outputs the second frequency control signal representing the frequency reduction amount ΔFRD(=FRF−FLOmin−FBB) to the DDC107(step S111ofFIG. 5).

Through this operation, the local oscillator102generates the local signal of the local frequency FLO(=FLOmin) represented by the first frequency control signal. Further, the DDC107converts the signal so that the frequency is lowered by the frequency reduction amount ΔFRD(=FRF−FLOmin−FBB) represented by the second frequency control signal.

Thereafter, the frequency controller112ends the frequency control process ofFIG. 5.

As described above, the transceiving device1according to the first embodiment includes the interference wave detector111that detects the interference wave within the intermediate frequency band in the signal converted by the mixer103. The transceiving device1further includes the frequency controller112that changes the local frequency so that the intermediate frequency band gets away from the band of the interference wave when the interference wave is detected.

Through this configuration, it is possible to cause the intermediate frequency band to get away from the band of the interference wave. Thus, it is possible to easily separate the signal within the intermediate frequency band from the interference wave. As a result, the quality of a reception signal can be improved.

The transceiving device1according to the first embodiment further includes the first filter105that is configured to attenuate the signal outside the first passband having the band width larger than the width of the intermediate frequency band in the signal converted by the mixer103. Further, the frequency controller112is configured to change the local frequency so that the intermediate frequency band gets away from the band of the interference wave within the first passband.

Through this configuration, it is possible to cause the intermediate frequency band to get away from the band of the interference wave within the range which is not attenuated by the first filter105. As a result, the quality of the reception signal can be further improved.

In addition, the transceiving device1according to the first embodiment includes the DDC107that converts the signal that has passed through the first filter105based on the local frequency so that the frequency changes by the difference between the intermediate frequency and the base frequency.

Through this operation, even when the intermediate frequency band changes as the local frequency changes, the intermediate signal can be converted into the base band signal of the base band with a certain base frequency as the center.

Furthermore, the transceiving device1according to the first embodiment includes the second filter108which is configured to attenuate the signal outside the base band in the signal converted by the DDC107.

Through this configuration, the signal can be attenuated based on the interference wave. As a result, the quality of the reception signal can be further improved.

In addition, in the transceiving device1according to the first embodiment, the interference wave detector111is configured to acquire the interference wave power which is the power of the interference wave. Further, the frequency controller112changes the local frequency FLOto minimize the acquired interference wave power when the interference wave is detected.

Through this configuration, the power of the interference wave can be reduced. As a result, the quality of the reception signal can be further improved.

Further, the transceiving device1according to the first embodiment is configured to change the local frequency FLOby the frequency change amount α, but may be configured to store a plurality of different candidate values in advance and sequentially change the local frequency FLOto the respective candidate values.

Next, a transceiving device according to a second embodiment of the present invention will be described. The transceiving device according to the second embodiment has the same configuration as the transceiving device according to the first embodiment except that the local frequency is decided based on the band of the interference wave so that the intermediate frequency band does not overlap the band of the interference wave. The following description will proceed focusing on the different point. In the description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals.

A transceiving device1A according to the second embodiment includes a receiving unit14A instead of the receiving unit14as illustrated inFIG. 7. The receiving unit14A according to the second embodiment has the same configuration as the receiving unit14except that the frequency controller112A is provided instead of the frequency controller112.

In the present example, the width (the first passband width) WFP1of the first passband of the first filter105is set to a value (2WIS+WIW) obtained by adding the band of the interference wave width WIWto the value 2WISwhich is twice as large as the intermediate frequency band width WIS. The center of the first passband is set to the basic intermediate frequency FIS0.

When the interference wave is detected by the interference wave detector111, the frequency controller112A changes the local frequency FLOso that the intermediate frequency band gets away from the band of the interference wave. In the present example, the frequency controller112A changes the local frequency FLOso that the intermediate frequency band gets away from the band of the interference wave within the first passband.

For example, the frequency controller112A selects the local frequency FLOfrom three local frequency candidate values (a first local frequency candidate FLO0, a second local frequency candidate FLO1, and a third local frequency candidate FLO2) based on the interference wave information output from the interference wave detector111. In the present example, the first local frequency candidate FLO0is the basic local frequency FLO0.

The second local frequency candidate FLO1is preferably set so that the upper limit value of the frequency band (i.e., the intermediate frequency band) of the intermediate signal converted by the mixer103is identical to the upper limit value of the first passband of the first filter105. Further, the third local frequency candidate FLO2is preferably set so that the lower limit value of the frequency band (i.e., the intermediate frequency band) of the intermediate signal converted by the mixer103is identical to the lower limit value of the first passband of the first filter105.

In the present example, the second local frequency candidate FLO1, and the third local frequency candidate FLO2are represented by Mathematical Formulas 2 and 3:
FLO1=FLO0−(WIS+WIW)/2  (Mathematical Formula 2)
FLO2=FLO0+(WIS+WIW)/2  (Mathematical Formula 3)

Further, in the present example, the frequency controller112A selects the local frequency FLOfrom the three local frequency candidate values, but may select the local frequency FLOfrom the two local frequency candidate values, that is, the second local frequency candidate FLO1and the third local frequency candidate FLO2.

When the representative interference wave power is equal to or lower than the certain permissible power, the frequency controller112selects the first local frequency candidate FLO0as the local frequency FLO.

Further, in the case where the representative interference wave power is larger than the certain permissible power, the frequency controller112selects the second local frequency candidate FLO1as the local frequency FLOwhen the representative interference wave frequency is smaller than the basic intermediate frequency FIS0.

Further, in the case where the representative interference wave power is larger than the certain permissible power, the frequency controller112selects the third local frequency candidate FLO2as the local frequency FLOwhen the representative interference wave frequency is equal to or larger than the basic intermediate frequency FIS0.

In the present example, the representative interference wave power is the maximum value of the interference wave power. Alternatively, the representative interference wave power may be an average value of the interference wave power. Further, the representative interference wave frequency is a representative value of the interference wave frequency. In the present example, the representative interference wave frequency is an average value of the interference wave frequency. Further, the representative interference wave frequency may be a value obtained by weighted-averaging the interference wave frequency based on the interference wave power. Further, the representative interference wave frequency may be a frequency corresponding to the maximum interference wave power.

The frequency controller112A outputs the first frequency control signal representing the selected local frequency FLOto the local oscillator102.

Further, the frequency controller112A calculates a value (FRF−FLO−FBB) obtained by subtracting the base frequency FBBfrom a value obtained by subtracting the selected local frequency FLOfrom the radio frequency FRF, as the frequency reduction amount ΔFRD. In addition, the frequency controller112A outputs the second frequency control signal representing the calculated frequency reduction amount ΔFRDto the DDC107.

Next, an operation of the transceiving device1A will be described with reference toFIGS. 8 to 11.

The frequency controller112A performs a frequency control process illustrated inFIG. 8at a certain timing instead of the frequency control process illustrated inFIG. 5. In the present example, the frequency controller112A performs the frequency control process when the transceiving device1A is activated. The frequency controller112A may perform the frequency control process each time a certain execution period elapses or when the representative interference wave power is larger than a certain execution threshold value.

First of all, when execution of the frequency control process starts, the frequency controller112A sets (selects) the basic local frequency FLO0as the local frequency FLO(step S201ofFIG. 8). Then, the frequency controller112A outputs the first frequency control signal representing the selected local frequency FLOto the local oscillator102, and outputs the second frequency control signal representing the frequency reduction amount ΔFRD(=FRF−FLO0−FBB) to the DDC107(step S202ofFIG. 8).

Through this operation, the local oscillator102generates the local signal of the local frequency FLO(=FLO0) represented by the first frequency control signal. Further, the DDC107changes the signal so that the frequency thereof is lowered by the frequency reduction amount ΔFRD(=FRF−FLO0−FBB) represented by the second frequency control signal.

Thereafter, the mixer103converts the radio signal received by the antenna11into the intermediate signal based on the local signal generated by the local oscillator102. In other words, the mixer103changes the signal SRF amplified by the first amplifier101so that the frequency thereof is lowered by the local frequency FLO(=FLO0) as illustrated inFIG. 9A. Through this operation, the signal SRF of the radio frequency band is converted into the intermediate signal SIS of the intermediate frequency band with the intermediate frequency FIS(=FRF−FLO0) as the center.

Then, the DDC107converts the signal so that the frequency thereof is lowered by the frequency reduction amount ΔFRD(=FRF−FLO0−FBB) represented by the second frequency control signal. Through this operation, the intermediate signal SIS of the intermediate frequency band is converted into the base band signal SBB of the base band with the base frequency FBBas the center.

Further, the interference wave detector111detects the interference wave within the intermediate frequency band in the signal converted by the mixer103.

When the interference wave information is output from the interference wave detector111, the frequency controller112A acquires the representative interference wave power based on the interference wave information. However, when the interference wave information is not output from the interference wave detector111, the frequency controller112A acquires “0” as the representative interference wave power (step S203ofFIG. 8).

In the present example, the interference wave SIW of the band which is within the intermediate frequency band and lower than the basic intermediate frequency FIS0is assumed to be detected in the signal converted by the mixer103as illustrated inFIG. 9A.

Further, when the interference wave information is output from the interference wave detector111, the frequency controller112A acquires the representative interference wave frequency FIWbased on the interference wave information. However, when the interference wave information is not output from the interference wave detector111, the frequency controller112A acquires “0” as the representative interference wave frequency FIW(step S204ofFIG. 8).

The frequency controller112A determines whether the acquired representative interference wave power is larger than the permissible power (step S205ofFIG. 8).

Here, the representative interference wave power is assumed to be larger than the permissible power. In this case, the frequency controller112A determines “Yes,” and determines whether the acquired representative interference wave frequency FIWis smaller than the basic intermediate frequency FIS0(step S206ofFIG. 8).

According to the above assumption, the representative interference wave frequency FIWis smaller than the basic intermediate frequency FIS0and thus the frequency controller112A determines “Yes,” selects the second local frequency candidate FLO1(=FLO0)−(WIS+WIW)/2) as the local frequency FLO(step S207ofFIG. 8).

Then, the frequency controller112A outputs the first frequency control signal representing the selected local frequency FLO(=FLO1) to the local oscillator102, and outputs the second frequency control signal representing the frequency reduction amount ΔFRD(=FRF−FLO1−FBB) to the DDC107(step S209ofFIG. 8).

Through this operation, the local oscillator102generates the local signal of the local frequency FLO(=FLO1) represented by the first frequency control signal. Further, the DDC107converts the signal so that the frequency thereof is lowered by the frequency reduction amount ΔFRD(=FRF−FLO1−FBB) represented by the second frequency control signal.

Thereafter, the mixer103converts the radio signal received by the antenna11into the intermediate signal based on the local signal generated by the local oscillator102. In other words, the mixer103converts the signal SRF amplified by the first amplifier101so that the frequency thereof is lowered by the local frequency FLO(=FLO1) as illustrated inFIG. 9B. Through this operation, the signal SRF of the radio frequency band is converted into the intermediate signal SIS of the intermediate frequency band with the intermediate frequency FIS(=FRF−FLO1) as the center.

In this way, the frequency controller112A changes the local frequency FLOso that the intermediate frequency band of the intermediate signal SIS does not overlap the band of the interference wave SIW within the first passband PB1as illustrated inFIGS. 9A and 9B.

Then, the DDC107converts the signal so that the frequency thereof is lowered by the frequency reduction amount ΔFRO(=FRF−FLO1−FBB) represented by the second frequency control signal. Through this operation, the intermediate signal SIS of the intermediate frequency band is converted into the base band signal SBB of the base band with the base frequency FBBas the center.

Thereafter, the frequency controller112A ends the frequency control process ofFIG. 8.

Next, the case in which the interference wave SIW of the band which is within the intermediate frequency band and higher than the basic intermediate frequency FIS0is detected in the signal converted by the mixer103as illustrated inFIG. 10Ais considered.

In this case, when the frequency controller112A proceeds to step S206ofFIG. 8, the frequency controller112A determines “No,” and selects the third local frequency candidate FLO2(=FLO0+(WIS+WIW)/2) as the local frequency FLO(step S208ofFIG. 8).

Then, the frequency controller112A outputs the first frequency control signal representing the selected local frequency FLO(=FLO2) to the local oscillator102, and outputs the second frequency control signal representing the frequency reduction amount ΔFRD(=FRF−FLO2−FBB) to the DDC107(step S209ofFIG. 8).

Through this operation, the local oscillator102generates the local signal of the local frequency FLO(=FLO2) represented by the first frequency control signal. Further, the DDC107converts the signal so that the frequency thereof is lowered by the frequency reduction amount ΔFRD(=FRF−FLO2−FBB) represented by the second frequency control signal.

Thereafter, the mixer103converts the radio signal received by the antenna11into the intermediate signal based on the local signal generated by the local oscillator102. In other words, the mixer103converts the signal SRF amplified by the first amplifier101so that the frequency thereof is lowered by the local frequency FLO(=FLO2) as illustrated inFIG. 10B. Through this operation, the signal SRF of the radio frequency band is converted into the intermediate signal SIS of the intermediate frequency band with the intermediate frequency FIS(=FRF−FLO2) as the center.

In this way, the frequency controller112A changes the local frequency FLOso that the intermediate frequency band of the intermediate signal SIS does not overlap the band of the interference wave SIW within the first passband PB1as illustrated inFIGS. 10A and 10B.

Then, the DDC107converts the signal so that the frequency is lowered by the frequency reduction amount ΔFRD(=FRF−FLO2−FBB) represented by the second frequency control signal. Through this operation, the intermediate signal SIS of the intermediate frequency band is converted into the base band signal SBB of the base band with the base frequency FBBas the center.

Thereafter, the frequency controller112A ends the frequency control process ofFIG. 8.

Next, the case in which the interference wave SIW is outside the intermediate frequency band in the signal converted by the mixer103as illustrated inFIG. 11is considered.

In this case, when the process proceeds to step S205ofFIG. 8, the frequency controller112A determines “No,” outputs the first frequency control signal representing the local frequency FLO(=FLO0) selected in step S201to the local oscillator102, and outputs the second frequency control signal representing the frequency reduction amount ΔFRD(=FRF−FLO0−FBB) to the DDC107(step S209ofFIG. 8). In other words, in this case, the local frequency FLOremains with no change.

Thereafter, the frequency controller112A ends the frequency control process ofFIG. 8.

As described above, the transceiving device1A according to the second embodiment can obtain the same operation and effects as in the transceiving device1according to the first embodiment.

In the transceiving device1A according to the second embodiment, the width of the first passband of the first filter105is set to the width obtained by adding the band width WIWof the interference wave to the width which is twice as large as the width WISof the intermediate frequency band.

Through this configuration, in the range which is not attenuated by the first filter105, the intermediate frequency band can reliably be arranged as the band other than the band of the interference wave. As a result, the quality of the reception signal can be further reliably improved.

In addition, in the transceiving device1A according to the second embodiment, when the frequency controller112A detects the interference wave, the local frequency FLOis changed so that the intermediate frequency band does not overlap the band of the interference wave within the first passband.

Through this configuration, in the range which is not attenuated by the first filter105, the intermediate frequency band can be prevented from overlapping the band of the interference wave. As a result, the quality of the reception signal can be further reliably improved.

The present invention has been described with reference to the exemplary embodiments, but the present invention is not limited to the above embodiments. In the configuration and details of the present invention, various changes which can be understood by a person skilled in the art can be made within the scope of the present invention.

In the above embodiments, the transceiving device may be a receiving device including no transmitting unit. Further, in the above embodiments, the transceiving device may include a first antenna for transmitting a radio signal and a second antenna for receiving a radio signal.

Further, in the above embodiments, the receiving unit may be mounted in a radio base station or a wireless terminal (e.g., a mobile station) as a receiving device.

Further, in the above embodiments, the interference wave detector111is configured to detect the interference wave in the signal that has passed through the second filter108but may be configured to detect the interference wave in a signal that does not pass through the second filter108(i.e., the signal output from the DDC107). In this case, the interference wave detector111may be configured to detect the interference wave based on a relation between the frequency corresponding to the average power value higher than the threshold power and the intermediate frequency band.

Further, in the above embodiments, each of the mixer103and the DDC107converts the signal to lower the frequency, but at least one of the mixer103and the DDC107may convert the signal to increase the frequency.

Further, in the above embodiments, the respective functions of the receiving device may be implemented by hardware such as a field programmable gate array (FPGA). The respective functions of the receiving device may be implemented using hardware including a processing device (e.g., a central processing unit (CPU), or a digital signal processor (DSP)) and a storage device (e.g., a read only memory (ROM) or a random access memory (RAM)).

In this case, for example, the transceiving device1or1A includes a processing device152and a storage device153as illustrated inFIG. 12. The processing device152is connected with the storage device153via a bus BS. The processing device152is configured to implement the respective functions of the DDC107, the second filter108, the DGC109, the interference wave detector111, and the frequency controller112or the frequency controller112A in collaboration with the storage device153.

Further, arbitrary combinations of the above embodiments and the modification may be employed as other modifications of the above embodiments within the scope not departing from the gist of the present invention.

According to the control device of the present disclosure, the quality of a reception signal can be improved.