JP2000174558A - Image rejection reception circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image rejection reception circuit that realizes a high image rejection reception ratio in the image rejection reception circuit used for a reception section of a radio equipment. SOLUTION: The image rejection reception circuit consists of an image detection circuit 22 that detects a frequency for an image signal band and a signal level, a control signal generating circuit 23 that generates a proper control signal based on the detected result, IF signal amplitude phase control circuits 32, 33 that control the phase and the amplitude of an IF signal by the control signal, and a synthesizer 36 that synthesizes the IF signals. Since a peak frequency for image rejection is coincident with a frequency of an image signal with a highest level, the image rejection reception circuit difficult accepting image disturbance at all times and a radio equipment having the circuit can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image rejection receiving circuit used in a receiving section of a wireless device.

[0002]

2. Description of the Related Art A conventional image rejection receiving circuit is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-218361. FIG. 10 is a block diagram showing a configuration of a conventional image rejection receiving circuit.

[0003] A received signal 1 is received by a distributor 2 into a received signal 3,
4 and input to mixers 5 and 6, respectively. The local oscillator signal 7 is divided into two by the hybrid phase shifter 15 into a local oscillator signal 8 and a local oscillator signal 9 having a phase difference of 90 ° with respect to the local oscillator signal 8, and is input to the mixers 5 and 6. The IF signal 1 is output from the mixer 5 to which the reception signal 3 and the local oscillation signal 8 are input.
1 is output, and an IF signal 10 orthogonal to the IF signal 11 is output from the mixer 6 to which the received signal 4 and the local oscillation signal 9 are input.

At this time, FIG. 11 shows a vector diagram of each signal when, for example, a desired signal and an image signal are input in the received signal in the same phase as the local oscillation signal. When the desired signal and the image signal are mixed with the local signal 8 by the mixer 5, the IF signal 1
As 1, a signal in which the desired wave and the image signal are in phase with each other is output. On the other hand, when the desired wave and the image signal are mixed with the local oscillation signal 9 by the mixer 6, the IF signal 10 has a phase orthogonal to that of the IF signal 11 and the desired wave and the image signal have opposite phases. A signal is output.

[0005] By providing a phase of ± 45 ° to these signals by using an IF phase shifter 13, the IF signal 11 and the IF
The phase of the desired wave of the signal 10 is in phase, and conversely, the image signal is in opposite phase. If these two signals are combined and taken out by the IF combiner 14, the image signal is canceled and can be removed.

As described above, in the image rejection receiving circuit in which the signal is divided into two and only the image signal is inverted by 180 ° to cancel each other, the amplitude difference and the phase difference of the IF signals to be combined determine the image rejection ratio. . For example, in order to secure an image rejection ratio of 40 dB or more, when the phase difference of the IF signals to be combined is set to 0, the amplitude difference is within 0.17 dB, and when the amplitude difference is set to 0, the phase difference is 1. It must be kept within 2 °. This relationship is shown in FIG.

[0007]

However, since each element constituting a wireless device generally has a frequency characteristic with respect to amplitude and phase, even in a reception occupied frequency band,
It is extremely difficult to suppress the amplitude difference and the phase difference of the IF signal to be combined within the above range. For this reason, if the phase shifter is designed so that the image rejection ratio peaks at the center frequency of the reception occupied frequency band, the phase difference and / or the amplitude difference of the IF signal to be synthesized at both ends of the reception occupation frequency band may be reduced. As a result, the image rejection ratio degrades. For example, the occupied frequency bandwidth is 4 MHz, and the phase deviation and the amplitude deviation within the occupied frequency bandwidth are each 0.1%.
FIG. 13 shows the image rejection ratio in the case of 1.7 dB.

An object of the present invention is to provide an image rejection receiving circuit that realizes a high image rejection ratio by changing the peak frequency of image rejection according to the frequency of a received image signal.

[0009]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides at least one detection circuit for detecting the frequency and signal level of a signal in an image frequency band, and the level of the plurality of detected signal levels. A control circuit that compares the difference and issues a control signal based on the comparison result, a divider that distributes the received signal, and a hybrid phase shifter that splits the local signal into two and outputs the signal with a phase difference of 90 degrees. A plurality of mixers for receiving respective received signals distributed by the distributor and a local oscillation signal having a phase difference of 90 degrees output from the hybrid phase shifter to generate IF signals, respectively; Controlling the phase and amplitude of each IF signal output from the control signal based on the control signal
A signal amplitude / phase control circuit; and a synthesizer for synthesizing an output of the IF signal amplitude / phase control circuit. Based on information from a circuit for detecting a signal in the image frequency band, a peak frequency for removing an image is determined. It is configured to automatically optimize according to external circumstances.

Alternatively, according to the present invention, one or more detection circuits for detecting the frequency and signal level of a signal in an image frequency band are compared with a level difference between the plurality of detected signal levels, and control is performed based on the comparison result. A control circuit that emits a signal, a distributor that distributes a received signal, a hybrid phaser that divides the local oscillation signal into two and outputs them with a phase difference of 90 degrees, and a 90 degree output from the hybrid phaser. A local oscillation signal amplitude and phase control circuit that controls the phase and amplitude of the local oscillation signal having a phase difference based on the control signal,
A plurality of mixers that receive the respective received signals distributed by the distributor and the respective outputs of the local oscillation signal amplitude / phase control circuit to generate respective IF signals, and change the phases of the respective IF signals; A phase shifter for synthesizing an output signal of the phase shifter, and based on information from a circuit for detecting a signal in the image frequency band, adjusts a peak frequency for removing an image according to an external situation. It is configured to optimize automatically.

Alternatively, according to the present invention, one or more detection circuits for detecting the frequency and signal level of a signal in an image frequency band, a level difference between the detected signal levels is compared, and control is performed based on the comparison result. A control circuit that emits a signal, a distributor that distributes a received signal, a received signal amplitude control circuit that controls the amplitude of each signal distributed by the distributor based on the control signal, and distributes a local oscillation signal And a hybrid phase shifter that outputs a signal having a phase difference of 90 degrees, and a local oscillation signal having a phase difference of 90 degrees output from the hybrid phase shifter and the output of the reception signal amplitude control circuit. It has a plurality of mixers for respectively generating IF signals, a phase shifter for changing the phase of each IF signal, and a synthesizer for synthesizing an output signal of the phase shifter. , Based on information from the circuit for detecting the signal of the image frequency band, which is constituted to automatically optimized according to the peak frequency of removing the image to an external situation.

As a result, it is possible to provide an image rejection receiving circuit realizing a high image rejection ratio.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, there is provided one or more detection circuits for detecting the frequency and signal level of a signal in an image frequency band, and a level difference between the detected signal levels. And a control circuit that issues a control signal based on the comparison result, a distributor that distributes the received signal, a hybrid phase shifter that distributes the local oscillation signal into two and outputs it with a phase difference of 90 degrees, A plurality of mixers for receiving the respective reception signals distributed by the distributor and the local oscillation signal having a phase difference of 90 degrees output from the hybrid phase shifter and generating an IF signal, respectively; An IF signal amplitude / phase control circuit for controlling the phase and amplitude of each output IF signal based on the control signal; and a combiner for combining the outputs of the IF signal amplitude / phase control circuit. An image rejection receiving circuit, characterized in that, based on information from a circuit for detecting a signal in the image frequency band, a peak frequency for removing an image is automatically optimized according to an external situation. In addition, since the peak frequency at which an image is removed can be automatically changed in accordance with the frequency of an image signal, an effect of always achieving a high image rejection ratio can be obtained.

According to a second aspect of the present invention, there is provided the image rejection receiving circuit according to the first aspect, wherein at least one notch filter for removing an image signal is provided, and the image is removed by the notch filter. And
In addition, since the peak frequency at which an image is removed can be automatically changed in accordance with the frequency of an image signal that cannot be sufficiently removed by the notch filter, a high image rejection ratio can always be realized.

According to a third aspect of the present invention, the image signal detecting circuit is constituted by using a plurality of notch filters having different trap frequencies and a level detecting circuit of a signal extracted from each notch filter. 2. The image rejection receiving circuit according to claim 1, wherein the peak frequency for removing the image can be automatically changed according to the frequency of the image signal, so that a high image rejection ratio can always be realized. Having.

According to a fourth aspect of the present invention, the IF signal amplitude / phase control circuit is configured using a phase shifter and an amplifier whose gain is variable by a control signal.
The image rejection receiving circuit described above has an effect that a peak frequency at which an image is removed can be automatically changed according to the frequency of an image signal, so that a high image rejection ratio can always be realized.

The invention according to claim 5 is characterized in that the IF signal amplitude / phase control circuit is constituted by using a varactor diode whose resistance is variable by a control signal and a resistor. Since it is an application receiving circuit, it can automatically change the peak frequency for removing the image according to the frequency of the image signal,
This has the effect that a high image rejection ratio can always be realized.

According to a sixth aspect of the present invention, at least one detection circuit for detecting a frequency and a signal level of a signal in an image frequency band is compared with a level difference between the plurality of detected signal levels, and the comparison result is provided. A control circuit that issues a control signal based on the received signal, a distributor that distributes the received signal, a hybrid phaser that distributes the local signal into two and outputs them with a phase difference of 90 degrees, and an output from the hybrid phaser. A local oscillation signal amplitude / phase control circuit for controlling the phase and amplitude of the local oscillation signal having a phase difference of 90 degrees based on the control signal, and the respective reception signals and the local oscillation signal amplitude distributed by the distributor. A plurality of mixers which receive respective outputs of the phase control circuit and generate respective IF signals;
A phase shifter for changing the phase of each of the IF signals;
A synthesizer for synthesizing the output signal of the phase shifter, based on information from a circuit for detecting a signal in the image frequency band, automatically optimizing a peak frequency for removing an image according to an external situation. This is an image rejection receiver circuit that removes the image with a notch filter and automatically changes the peak frequency at which the image is removed according to the frequency of the image signal that the notch filter cannot completely remove. Therefore, there is an effect that a high image rejection ratio can always be realized.

According to an eighth aspect of the present invention, the image signal detecting circuit is constituted by using a plurality of notch filters having different trap frequencies and a level detecting circuit of a signal extracted from each notch filter. 7. The image rejection receiving circuit according to claim 6, wherein a peak frequency for removing an image can be automatically changed according to a frequency of an image signal, so that a high image rejection ratio can always be realized. Having.

According to a ninth aspect of the present invention, the local oscillation signal amplitude / phase control circuit is configured using a phase shifter and an amplifier whose gain is variable by a control signal.
The image rejection receiving circuit described above has an effect that a peak frequency at which an image is removed can be automatically changed according to the frequency of an image signal, so that a high image rejection ratio can always be realized.

According to a tenth aspect of the present invention, the local signal amplitude / phase control circuit is constituted by using a varactor diode having a variable capacity by a control signal and a resistor. This is a rejection receiving circuit, which can automatically change the peak frequency at which an image is removed in accordance with the frequency of an image signal, and thus has the effect of always realizing a high image rejection ratio.

According to the present invention, at least one detection circuit for detecting the frequency and signal level of a signal in an image frequency band is compared with a level difference between the plurality of detected signal levels, and the comparison result is provided. A control circuit that issues a control signal based on the received signal; a distributor that distributes the received signal; a received signal amplitude control circuit that controls the amplitude of each signal distributed by the distributor based on the control signal; A hybrid phase shifter for distributing signals and outputting the signals with a phase difference of 90 degrees, the respective outputs of the reception signal amplitude control circuit and the 90 output from the hybrid phase shifter.
A plurality of mixers each receiving a local oscillation signal having a phase difference of two degrees to generate an IF signal,
A phase shifter for changing the phase of the signal, and a synthesizer for synthesizing an output signal of the phase shifter, and based on information from a circuit for detecting a signal in the image frequency band, a peak frequency for removing an image, This is an image rejection receiving circuit that automatically optimizes according to external conditions, and can automatically change the peak frequency at which the image is removed according to the frequency of the image signal. This has the effect of realizing an image rejection ratio.

According to a twelfth aspect of the present invention, there is provided the image rejection receiving circuit according to the eleventh aspect, comprising at least one notch filter for removing an image signal. In addition, since the peak frequency at which the image is removed can be automatically changed in accordance with the frequency of the image signal that cannot be completely removed by the notch filter, a high image rejection ratio can always be realized.

According to a thirteenth aspect of the present invention, the image signal detecting circuit is constituted by using a plurality of notch filters having different trap frequencies and a level detecting circuit of a signal extracted from each notch filter. The image rejection receiving circuit according to claim 11, wherein
Since the peak frequency at which the image is removed can be automatically changed in accordance with the frequency of the image signal, there is an effect that a high image rejection ratio can always be realized.

According to a fifteenth aspect of the present invention, there is provided a wireless device having the image rejection receiving circuit according to any one of the first to fourteenth aspects, wherein the reliability using the receiving circuit always having a high image rejection ratio is provided. Wireless device having a high reliability.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a block diagram showing a configuration of an image rejection receiving circuit according to an embodiment of the present invention. In FIG. 1, 21 is a received signal, 22 is an image signal detecting circuit, 23 is a control signal generating circuit, 25 is a distributor, 28 and 29 are mixers, 31 is an input local oscillator signal which is divided into two parts and has a 90 degree position. A hybrid phase shifter for giving a phase difference and outputting the IF signal;
Reference numerals 4 and 35 are IF signals, and 36 is an IF signal synthesizer.

FIG. 2 is a schematic diagram showing the configuration of the image signal detection circuit 22. In FIG. 2, reference numeral 41 denotes a reception signal input end, reference numeral 42 denotes a reception signal output end, reference numerals 43, 44, and 45 denote dielectric resonators having resonance frequencies within an image frequency band and having different resonance frequencies. It is a conceptual diagram which shows the resonance frequency characteristic of these dielectric resonators. 46, 4
Reference numerals 7 and 48 denote extraction lines for extracting signals from the dielectric resonators 43, 44 and 45, reference numerals 49, 50 and 51 denote Schottky diodes as detectors for DC-converting the extracted signals, and reference numerals 52, 53 and 54 denote detection lines. This is the signal output terminal.

FIG. 4 is a schematic diagram showing the configuration of the control signal generation circuit. 4, reference numerals 61, 62, and 63 denote input terminals for inputting signals from the image signal detection circuit 22, 64 denotes a CPU, 65 denotes a D / A converter, and 66 and 67 denote control signal output terminals.

Now, the signal of the image frequency band is received signal 2
When the signal is received as 1, the image signals are output from the resonators 43 and 4 in the image signal detection circuit 22 having different resonance frequencies.
4 and 45, each signal is converted into a detection signal by detectors 49, 50 and 51 in accordance with the signal level, and is output from detection signal output terminals 52, 53 and 54 and is output from the control signal generation circuit 23. Input to CPU 64 and CPU 6
Reference numeral 4 compares the detection signal levels and specifies the frequency of the image signal. Further, the CPU 64 sends to the D / A converter 65 a predetermined control signal for converting the peak frequency of image rejection into a received image signal. The D / A converter 65 sends a predetermined analog signal to the phase and amplitude control circuits 32 and 33 based on the control signal.

On the other hand, the received signal input to the splitter 25 via the image signal detection circuit 22 and split into two is split into two by the hybrid phase shifter 31 in the mixers 28 and 29 and has a phase difference of 90 degrees. IF signals 34 and 35 mixed with each of the two local oscillation signals and orthogonal to each other.
And input to the phase and amplitude control circuits 32 and 33.

At this time, for example, when the desired wave, the image signal, and the local oscillation signal are input in the same phase, the IF signal 34 outputs the image signal and the desired wave in the same phase, and the IF signal 35 outputs the I signal.
An image signal that is orthogonal to the F signal 34 and that is in phase opposite to the desired wave is output.

The mutually orthogonal IF signals 34 and 35
Is changed by the phase and amplitude control circuits 32 and 33 so that the desired signal is in phase, that is, the image signal is in opposite phase, and then synthesized by the IF signal synthesizer 36 to obtain the image signal. Is removed, and only the desired wave can be extracted.

FIG. 5 is a schematic diagram showing an example of a specific configuration of the phase and amplitude control circuit. Phase amplitude control circuit 3 of FIG.
2 and 33 correspond to 130 and 133 in FIG. 5, respectively. Resistors 131 and 135, capacitors 132 and 134,
It comprises amplifiers 136 and 137 whose gains are variable by control signals.

FIG. 6 is a conceptual diagram showing an image rejection characteristic of an occupied frequency band by the amplitude control. The frequency configuration includes a reception frequency of 2.4 GHz and a local oscillation frequency of 2.44 GH.
z, IF frequency 40 MHz, image signal frequency 2.4
Assuming that the frequency is 8 GHz and the reception occupied frequency bandwidth is 4 MHz, the image rejection within the reception occupied frequency bandwidth when the amplitude of the 40 MHz IF signal output from the phase amplitude control circuits 32 and 33 has a difference of ± 1.5 dB. It shows the change of the action ratio.

As shown in FIG. 6, by controlling the amplitude, the frequency at which the image rejection ratio reaches a peak can be arbitrarily changed. Therefore, by matching the peak frequency at which the image is removed with the frequency at which the received signal level is the highest, it is possible to realize a receiving circuit that is less susceptible to image disturbance.

Similar results can be obtained by providing a phase difference or providing a phase difference and an amplitude difference at the same time instead of simply providing a difference in amplitude.

Although a configuration in which a resistor, a capacitor, and a variable gain amplifier are combined as shown in FIG. 5 is shown as the phase and amplitude control circuit, a configuration using a resistor and a varactor diode as shown in FIG. 7 can also be realized.

Although the resonator used in the image signal detection circuit uses a dielectric resonator, it can be realized by a resonator using a half-wavelength line.

(Embodiment 2) FIG. 8 is a block diagram showing a configuration of an image rejection receiving circuit according to an embodiment of the present invention. 8, reference numeral 91 denotes a received signal;
92 is an image signal detection circuit, 93 is a control signal generation circuit, 94 is a distributor, 95 and 96 are mixers, 98 is a hybrid phase shifter that divides an input local oscillation signal into two and gives a phase difference of 90 degrees to output. , 99, and 100 are local oscillation signal phase and amplitude control circuits; 101 and 102 are IF signal phase shifters;
3 is an IF signal synthesizer, and 104 and 105 are IF signals.

The image signal detection circuit 92 is the same as that described with reference to 22 in FIG. 2 of the first embodiment. In FIG. 2, reference numeral 41 denotes a reception signal input terminal, 42 denotes a reception signal output terminal, and 43 and 44. , 45 are dielectric resonators having resonance frequencies within the image frequency band and having different resonance frequencies, and 46, 47, 48 are dielectric resonators 43, 44,
45, a 50Ω extraction line for extracting a signal from each; 49, 50, and 51, Schottky diodes as detectors for DC-converting the extracted signal;
Reference numerals 3 and 54 are detection signal output terminals.

The control signal generation circuit 93 (Embodiment 1)
In FIG. 4, reference numerals 61, 62, and 63 denote input terminals for inputting a signal from the image signal detection circuit 92, 64 denotes a CPU, and 65 denotes a D / A.
Converters 66 and 67 are control signal output terminals.

Now, the image frequency band signal is
When received as 1, the image signal is transmitted to the resonators 43, 4, 4 having different resonance frequencies in the image signal detection circuit 92.
4 and 45, each signal is converted into a detection signal by detectors 49, 50 and 51 in accordance with the signal level, and is output from detection signal output terminals 52, 53 and 54 and is output from control signal generation circuit 93. Input to CPU 64 and CPU 6
Reference numeral 4 compares the detection signal levels and specifies the frequency of the image signal. Further, the CPU 64 sends to the D / A converter 65 a predetermined control signal for converting the peak frequency of the image removal into a received image signal. The D / A converter 65 sends a predetermined analog signal to the local oscillation signal phase and amplitude control circuits 99 and 100 based on the control signal.

On the other hand, the received signal input to splitter 94 via image signal detecting circuit 92 and split into two is mixed in mixers 28 and 29 by hybrid phase shifter 98 and sent to stations having a phase difference of 90 degrees. The generated signal is mixed with each of the signals input through the phase and amplitude control circuit, and becomes IF signals 104 and 105 orthogonal to each other.
Input to 01 and 102.

At this time, for example, if the desired signal, the image signal and the local signal are input in the same phase, the image signal and the desired signal are output in the same phase as the IF signal 104, and the IF signal 105 is orthogonal to the IF signal 104 and , An image signal having a phase opposite to that of the desired wave is output.

The mutually orthogonal IF signals 104, 10
5 is changed by the phase shifters 101 and 102 so that the desired wave is in phase, that is, the image signal is in opposite phase, and then synthesized by the IF signal synthesizer 103. It is removed and only the desired wave can be extracted. However, the local oscillation signal 97 is supplied to the mixers 95 and 9
6 is used in a region where the input level is not saturated.

Local signal phase and amplitude control circuits 99 and 100
Have the same configuration as that shown in FIG. 5 of the first embodiment, and reference numerals 99 and 100 denote 130 and 133 in FIG.
Corresponding to Resistors 131 and 135, a capacitor 132,
134, an amplifier 136 whose gain is variable by a control signal,
37.

Since the mixers 95 and 96 are used at a level at which the local oscillation signal does not saturate, when the amplitude of the local oscillation signal phase and amplitude control circuits 99 and 100 is changed, the amplitude of each IF signal also increases. Change. FIG. 6 is a conceptual diagram showing image rejection characteristics of an occupied frequency band by amplitude control, as in (Embodiment 1). The frequency configuration includes a reception frequency of 2.4 GHz, a local oscillation frequency of 2.44 GHz,
IF frequency 40MHz, image signal frequency 2.48G
Hz, and a reception occupied frequency bandwidth of 4 MHz, image rejection within the reception occupied frequency bandwidth when a difference of ± 1.5 dB occurs in the amplitude of the 40 MHz IF signal output from the phase shifters 101 and 102. It shows a change in the ratio.

As shown in FIG. 6, by controlling the amplitude, the frequency at which the image rejection ratio peaks can be arbitrarily changed. Therefore, by matching the peak frequency at which the image is removed with the frequency at which the received signal level is the highest, it is possible to realize a receiving circuit that is less susceptible to image disturbance.

The same result can be obtained by providing a phase difference or providing a phase difference and an amplitude difference at the same time instead of simply providing a difference in amplitude.

Although the phase and amplitude control circuit has a configuration in which a resistor, a capacitor, and a variable gain amplifier are combined as shown in FIG. 5, it can also be realized by a configuration with a resistor and a varactor diode as shown in FIG.

Although the resonator used in the image signal detection circuit uses a dielectric resonator, it can be realized by a resonator using a half-wavelength line.

(Embodiment 3) FIG. 9 is a block diagram showing a configuration of an image rejection receiving circuit according to an embodiment of the present invention. In FIG. 9, 111 is a received signal, 112 is an image signal detection circuit, 113 is a control signal generation circuit, 114 is a distributor, 115 and 116 are received signal amplitude control circuits, 117 and 118 are mixers, and 120 is an input station transmission. A hybrid phase shifter that divides the signal into two and gives a phase difference of 90 degrees to output the signals; 121 and 122 are IF phase shifters; 123 is an IF signal synthesizer; and 124 and 125 are IF signals.

The image signal detection circuit 112 is the same as that described with reference to 22 in FIG.
In the figure, 41 is a reception signal input terminal, 42 is a reception signal output terminal, 43, 44 and 45 are dielectric resonators having resonance frequencies within an image frequency band and having different resonance frequencies, and 46, 47 and 48. Are the dielectric resonators 43, 44,
45, a 50Ω extraction line for extracting a signal from each; 49, 50, and 51, Schottky diodes as detectors for DC-converting the extracted signal;
Reference numerals 3 and 54 are detection signal output terminals.

The control signal generation circuit 113 is the same as that described with reference to 23 in FIG. 4 of the first embodiment, and in FIG.
2, an input terminal for inputting a signal from 2; 64, a CPU; 65, a D / A converter; and 66, 67, control signal output terminals.

Now, the signal in the image frequency band is received signal 1
11, the image signal is transmitted to the resonator 43 having a different resonance frequency in the image signal detection circuit 112.
Each signal is trapped by 44 and 45, and each signal is converted into a detection signal by detectors 49, 50 and 51 in accordance with the signal level, and is output from detection signal output terminals 52, 53 and 54 and is output from control signal generation circuit 113. Input to the CPU 64 and the CPU
Reference numeral 64 compares the detection signal levels and specifies the frequency of the image signal. Further, the CPU 64 sends to the D / A converter 65 a predetermined control signal for converting the peak frequency of the image removal into a received image signal. D / A
Converter 65 sends a predetermined analog signal to reception signal amplitude control circuits 115 and 116 based on the control signal.

On the other hand, the received signal input to the distributor 114 via the image signal detecting circuit 112 and divided into two is transmitted to the mixer 11 via the received signal amplitude control circuits 115 and 116.
7 and 118, which are bi-divided by the hybrid phase shifter 120 and mixed with the respective local oscillation signals having a phase difference of 90 degrees by the mixers 117 and 118 to become IF signals 124 and 125 orthogonal to each other. 12
Enter 2

At this time, for example, if the desired signal, the image signal, and the local signal are input in the same phase, the IF signal 124 outputs the image signal and the desired signal in the same phase, and the IF signal 125 is orthogonal to the IF signal 124 and , An image signal having a phase opposite to that of the desired wave is output.

The mutually orthogonal IF signals 124 and 12
5 is changed by the phase shifters 121 and 122 so that the desired signal has the same phase, that is, the image signal has the opposite phase, and then synthesized by the IF signal synthesizer 123. It is removed and only the desired wave can be extracted. However, the reception signal 111 is
7, 118 are used in a region where the input level is not saturated.

The received signal amplitude control circuits 115 and 116
The configuration is the same as that shown in FIG. 5 of the first embodiment, and 115 and 116 correspond to 130 and 133 in FIG. 5, respectively. Resistors 131 and 135, capacitors 132 and 1
34, amplifiers 136 and 13 whose gains are variable according to control signals
7.

Since the received signals are used at a level that does not saturate the mixers 117 and 118, if the amplitude is changed by the received signal amplitude control circuits 115 and 116, the amplitude of each IF signal also changes. (Embodiment 1)
Similarly to FIG. 6, FIG. 6 is a conceptual diagram showing image rejection characteristics of an occupied frequency band by amplitude control. The frequency configuration is a receiving frequency of 2.4 GHz and a local oscillation frequency of 2.44 GH.
z, IF frequency 40 MHz, image signal frequency 2.4
Image rejection within the reception occupied bandwidth when the amplitude of the 40 MHz IF signal output from the phase shifters 121 and 122 is set to ± 1.5 dB when the frequency is 8 GHz and the reception occupied frequency bandwidth is 4 MHz. It shows a change in the ratio.

As shown in FIG. 6, by controlling the amplitude, the frequency at which the image rejection ratio peaks can be arbitrarily changed. Therefore, by matching the peak frequency at which the image is removed with the frequency at which the received signal level is the highest, it is possible to realize a receiving circuit that is less susceptible to image disturbance.

The same result can be obtained by providing a phase difference or providing a phase difference and an amplitude difference at the same time instead of simply providing a difference in amplitude.

Although the configuration in which the resistor, the capacitor, and the variable gain amplifier are combined as shown in FIG. 5 is shown as the reception signal amplitude control circuit, it can also be realized with the configuration using the resistor and varactor diode as shown in FIG.

Although the resonator used in the image signal detection circuit is a dielectric resonator, it can be realized by a resonator using a half-wavelength line.

[0065]

As described above, according to the present invention, the image rejection receiving circuit used in the receiving section of the radio apparatus changes the peak frequency of image rejection according to the frequency of the received image signal. ,
An image rejection receiving circuit that realizes a high image rejection ratio can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an image rejection receiving circuit according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of an image signal detection circuit according to one embodiment of the present invention;

FIG. 3 is a conceptual diagram showing a resonance frequency characteristic of the dielectric resonator according to one embodiment of the present invention.

FIG. 4 is a schematic diagram showing a configuration of a control signal generation circuit according to one embodiment of the present invention;

FIG. 5 is a schematic diagram showing a configuration of a phase and amplitude control circuit according to an embodiment of the present invention.

FIG. 6 is a conceptual diagram showing image rejection characteristics of an occupied frequency band by amplitude control according to one embodiment of the present invention.

FIG. 7 is a schematic diagram showing a configuration of a phase and amplitude control circuit according to one embodiment of the present invention;

FIG. 8 is a block diagram showing a configuration of an image rejection receiving circuit according to one embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of an image rejection receiving circuit according to one embodiment of the present invention;

FIG. 10 is a block diagram showing a configuration of a conventional image rejection receiving circuit.

FIG. 11 is a conceptual diagram showing a vector change of a signal by a conventional image rejection receiving circuit.

FIG. 12 is a conceptual diagram showing a relationship between a phase difference, an amplitude difference, and an image rejection ratio by a conventional image rejection receiving circuit.

FIG. 13 is a conceptual diagram showing image rejection characteristics in an occupied frequency band by a conventional image rejection receiving circuit.

[Explanation of symbols]

 22, 92, 112 Image signal detection circuit 23, 93, 113 Control signal generation circuit 25, 94, 114 Distributor 28, 29, 95, 96, 117, 118 Mixer 31, 98, 120 Hybrid phaser 32, 33 IF signal Phase amplitude control circuit 99, 100 Local oscillator signal phase amplitude control circuit 36, 103, 123 IF signal synthesizer 41 Received signal input end 42 Received signal output end 43, 44, 45 Dielectric resonator 49, 50, 51 Detector ( Schottky diode) 64 CPU 65 D / A converter 101, 102, 121, 122 Phase shifter 115, 116 Received signal amplitude control circuit 131, 135 Resistor 132, 134 Capacitor 133, 134 Phase amplitude control circuit 136, 137 Amplifier

Claims (15)

[Claims] 1. A circuit for detecting a frequency and a signal level of a signal in an image frequency band, and comparing a level difference between the plurality of detected signal levels and issuing a control signal based on the comparison result. A control circuit, a splitter for splitting the received signal, a hybrid phase shifter for splitting the local oscillation signal into two and outputting them with a phase difference of 90 degrees, each of the received signals split by the splitter and the hybrid A plurality of mixers, each receiving a local oscillation signal having a phase difference of 90 degrees output from the phase shifter and generating an IF signal, and each IF output from the mixer
I for controlling the phase and amplitude of the signal based on the control signal
An F signal amplitude / phase control circuit, and a synthesizer for synthesizing the output of the IF signal amplitude / phase control circuit, based on information from a circuit for detecting a signal in the image frequency band,
An image rejection receiving circuit for automatically optimizing a peak frequency for removing an image according to an external situation. 2. The apparatus according to claim 1, further comprising at least one notch filter for removing an image signal.
An image rejection receiving circuit as described. 3. The image signal detecting circuit according to claim 1, wherein the image signal detecting circuit includes a plurality of notch filters having different trap frequencies and a signal level detecting circuit extracted from each notch filter. Image rejection receiving circuit. 4. The image rejection reception circuit according to claim 1, wherein the IF signal amplitude / phase control circuit is configured using a phase shifter and an amplifier whose gain is variable by a control signal. 5. The image rejection reception circuit according to claim 1, wherein the IF signal amplitude / phase control circuit is constituted by using a varactor diode having a variable capacitance according to a control signal and a resistor. 6. One or more detection circuits for detecting the frequency and signal level of a signal in an image frequency band, comparing a level difference between the plurality of detected signal levels, and issuing a control signal based on the comparison result. A control circuit, a splitter for splitting the received signal, a hybrid phase shifter for splitting the local oscillation signal into two and outputting with a phase difference of 90 degrees, and a phase difference of 90 degrees output from the hybrid phase shifter. A local oscillation signal amplitude / phase control circuit for controlling the phase and amplitude of the local oscillation signal based on the control signal, and respective reception signals distributed by the distributor and respective outputs of the local oscillation signal amplitude / phase control circuit , A plurality of mixers for respectively generating IF signals, a phase shifter for changing the phase of each IF signal, and a synthesizer for synthesizing an output signal of the phase shifter. And an image rejection receiving circuit for automatically optimizing a peak frequency for removing an image in accordance with an external situation, based on information from a circuit for detecting a signal in the image frequency band. 7. The apparatus according to claim 6, wherein at least one notch filter for removing an image signal is provided.
An image rejection receiving circuit as described. 8. The image signal detecting circuit according to claim 6, wherein the image signal detecting circuit is constituted by using a plurality of notch filters having different trap frequencies and a signal level detecting circuit extracted from each notch filter. Image rejection receiving circuit. 9. The image rejection receiving circuit according to claim 6, wherein the local signal amplitude / phase control circuit is configured using a phase shifter and an amplifier whose gain is variable by a control signal. 10. The image rejection reception circuit according to claim 6, wherein the local signal amplitude / phase control circuit is configured using a varactor diode having a variable capacitance according to a control signal and a resistor. 11. One or more detection circuits for detecting a frequency and a signal level of a signal in an image frequency band, comparing a level difference between the plurality of detected signal levels, and issuing a control signal based on the comparison result. A control circuit, a distributor for distributing the received signal, a received signal amplitude control circuit for controlling the amplitude of each signal distributed by the distributor based on the control signal, And a local phase signal having a phase difference of 90 degrees output from the hybrid phase shifter and the output of the reception signal amplitude control circuit, respectively, and an IF signal And a phase shifter for changing the phase of each IF signal; and a synthesizer for synthesizing an output signal of the phase shifter. An image rejection receiving circuit for automatically optimizing a peak frequency for removing an image in accordance with an external situation based on information from a circuit for detecting a signal in a frequency band. 12. The image rejection receiving circuit according to claim 11, further comprising at least one notch filter for removing an image signal. 13. The image signal detecting circuit according to claim 11, wherein the image signal detecting circuit is constituted by using a plurality of notch filters having different trap frequencies and a signal level detecting circuit extracted from each notch filter. Image rejection receiving circuit. 14. The image rejection reception circuit according to claim 11, wherein the reception signal amplitude control circuit is configured using an amplifier whose gain is variable by a control signal. 15. A wireless device having the image rejection receiving circuit according to claim 1.