JP2002135058A - Image rejection mixer and receiver using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image rejection mixer capable of reducing a stand-by power. SOLUTION: The image rejection mixer comprises a switch 7 for selecting a direct connection of a low-pass filter 4a to an output terminal OUT or a phase shifter 5a, a bias voltage control circuit 9 for controlling on/off the operating states of a phase shifter 3, the mixer 1b, the filter 4b, the shifter 5a, a phase shifter 5b and an adder 6, and a control circuit 8 for controlling the switch 7 and the circuit 9 so that the circuit 9 is controlled off when the filter 4a is directly connected to the terminal OUT by the switch 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image rejection mixer and a receiving device using the same.

[0002]

2. Description of the Related Art Generally, in a radio wave receiving apparatus, a super heterodyne system is used in which a received signal is mixed with a local oscillation signal oscillated by an internal local oscillation circuit to generate an IF signal, thereby performing a stable amplification operation. ing. In this superheterodyne receiving apparatus, the frequency of the local oscillation signal is set to be shifted upward (or downward) by the frequency of the IF signal with respect to the frequency of the received radio wave. If there is a radio wave at a minus position, this radio wave will also be received. This radio wave is called an image interference wave.

Since the IF signal down-converted from the received radio wave contains the desired wave component and the image interference wave component, if the IF signal is demodulated as it is, the reception quality such as the receiving sensitivity deteriorates. Would. For this reason, an image rejection mixer that can remove an image interference wave component from an IF signal is often used as a down-converting mixer.

FIG. 8 shows a typical circuit configuration of a conventional image rejection mixer, and its operation will be described below. An RF signal that is an input signal is input to an input terminal IN. After the RF signal is split into two, the mixer 1a,
1b. Then, the local oscillator 2 outputs a local oscillation signal in phase with the RF signal. This local oscillation signal is divided into two, and one of the local oscillation signals is supplied to the mixer 1a as it is. The other local oscillation signal is phase-shifted by 90 degrees in the leading direction by the phase shifter 3, and then supplied to the mixer 1b.

The mixer 1a multiplies the in-phase RF signal and the local oscillation signal by each other, and supplies the multiplied signal to the low-pass filter 4a at the next stage. Also, the mixer 1b has an RF
The signal is multiplied by a local oscillation signal phase-shifted by 90 degrees in the leading direction, and the multiplied signal is multiplied by the low-pass filter 4b at the next stage.
To supply. The IF included in the output signal of the mixer 1a
The signal is a signal whose phase is advanced by 90 degrees with respect to the IF signal included in the output signal of the mixer 1b.

These output signals pass through low-pass filters 4a and 4b, respectively, to remove high-frequency components and extract only IF signals. Low-pass filter 4
The IF signal output by a is shifted by 45 degrees in the leading direction by the phase shifter 5a. On the other hand, the IF signal output from the low-pass filter 4b is supplied to the
The phase is shifted five times. As a result, the desired wave components of these two IF signals have the same phase and the image interference wave components have the opposite phase. Therefore, the image interference wave component is removed by combining these two IF signals with the adder 6. , Only the desired wave component can be extracted at the output terminal OUT. In other words, an image rejection mixer is used to
This is a circuit that can convert to an F signal and remove an image interference wave component of the IF signal to extract only a desired wave component.

[0007]

The image rejection mixer is a single superheterodyne receiver, which receives a signal of a single frequency, has a low IF signal frequency, and has an image interference wave component which is an RF signal input signal. Often used when the filter cannot attenuate. For this reason, the image rejection mixer is often provided in an IC used in a mobile radio communication system. Since an IC used in a mobile wireless communication system often uses a battery as a power supply, it is necessary to reduce power consumption as much as possible to reduce battery consumption.

However, in preparation for the case where a signal instructing the transition from the standby state to the reception state is sent from the transmission apparatus, the reception apparatus needs to be able to receive this signal at any time in the standby state. For this reason,
The image rejection mixer must always be operated, and so-called standby power is consumed in all circuit parts of the image rejection mixer.

However, the signal transmitted from the transmitting apparatus, which instructs the transition from the standby state to the receiving state, can be sufficiently identified without removing the image interference wave component. That is, in the conventional image rejection mixer, useless standby power is consumed in a circuit portion for removing an image interference wave component in a standby state. In general, a receiver of a mobile radio communication system is much longer in a standby state than in a reception state, so this wasteful standby power is a major problem in saving energy.

[0010] In view of the above problems, an object of the present invention is to provide an image rejection mixer capable of reducing standby power and a receiving apparatus using the same.

[0011]

In order to achieve the above object, in an image rejection mixer according to the present invention, an RF signal and a local oscillation signal are each divided into two to obtain four signals. The first RF signal, the second RF signal, and the first RF signal are shifted by 90 degrees by the first phase shifting means.
Signal generating means for generating a local oscillation signal and a second local oscillation signal, a first mixer for multiplying the first RF signal and the first local oscillation signal, and a second RF signal
A second mixer for multiplying a signal by the second local oscillation signal; and a phase shifter for at least one of two signals output from the first and second mixers. Second phase shifting means for making the desired waves included in the respective signals in phase with each other, and two signals respectively output from the first and second mixers passing through the second phase shifting means are added together. Addition means for outputting to the output terminal, and a bypass means for supplying a signal output from the first mixer to the output terminal without passing through the second phase shift means and the addition means, Switch means for selecting whether the first mixer is connected to the second phase shift means or to the bypass means, and at least the second signal when the switch means selects the bypass means. of When the operation of the mixer, the second phase shifting means, and the adding means is turned off and the switch means selects the second phase shifting means, at least the second mixer, the second A phase shifter and a control circuit for turning on the operation of the adder are provided.

Further, the second RF signal or the second RF signal
When the local oscillation signal is a signal whose phase is shifted by 90 degrees by the first phase shifting means, from the viewpoint of reducing standby power,
When the control circuit causes the switch means to select the bypass means, the operation of the first phase shift means is turned off.
In the F state, when the switch means selects the second phase shift means, the operation of the first phase shift means is turned on.
It is desirable to be in a state.

In addition, a first low-pass filter is provided between the first mixer and the switch means, and a second low-pass filter is provided between the second mixer and the second phase shift means. And providing an OFF state of the operation of the second low-pass filter when the control circuit causes the switch means to select the bypass means,
When the switch means selects the second phase shift means, the operation of the second low-pass filter may be turned on.

Further, the control circuit may control the ON / OFF control of the supply of the bias voltage to the means whose operation state is controlled by the control circuit.

In order to achieve the above object, a receiving apparatus according to the present invention includes an image rejection mixer having the above-described configuration, and a judging means for judging whether or not the apparatus is in a standby state. The control circuit causes the switch means to select the bypass means in a standby state based on an output signal.

Further, the determination means may determine whether or not the apparatus is in a standby state based on the received data.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an image rejection mixer according to the present invention. Note that the same parts as those of the conventional image rejection mixer of FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted.

A switch 7 is provided between the low-pass filter 4a and the phase shifter 5a. The switch 7 controls the low-pass filter 4 based on a command signal sent from the control circuit 8.
a is connected to the phase shifter 5a or directly connected to the output terminal OUT. Then, the bias voltage control circuit 9
Are based on a command signal sent from the control circuit 8, based on the mixer 1b, the phase shifter 3, the low-pass filter 4b, the phase shifter 5a,
ON / OFF of the operation state of the phase shifter 5b and the adder 6
Control.

The switch 7 controls the low-pass filter 4a.
When the operation of the mixer 1b, the phase shifter 3, the low-pass filter 4b, the phase shifter 5a, the phase shifter 5b, and the adder 6 is turned on by the bias voltage control circuit 9, The image rejection mixer operates as a conventional image rejection mixer as shown in FIG. 8 (hereinafter, this state is referred to as “operation state”). The switch 7 connects the low-pass filter 4a to the output terminal OUT, and the bias voltage control circuit 9 controls the mixer 1b, the phase shifter 3, the low-pass filter 4b, the phase shifter 5a, the phase shifter 5b, and the adder 6. When the operation is turned off, the image rejection mixer operates as a down-converting mixer shown in FIG. 4 which cannot remove the image interference wave (hereinafter, this state is referred to as a “low power consumption state”).

Incidentally, the bias voltage control circuit 9 includes the mixer 1
b, the phase shifter 3, the low-pass filter 4b, the phase shifter 5a, the phase shifter 5b, and the adder 6 are turned off when the mixer 1b, the phase shifter 3, the low-pass filter 4b, and the phase shifter 5a are turned off. , The phase shifter 5b and the adder 6 operate to stop supplying the bias voltage to the active elements provided in the respective circuits. Thus, the mixer 1b, the phase shifter 3, the low-pass filter 4b, the phase shifter 5a, the phase shifter 5b,
The active elements provided in each circuit of the adder 6 are turned off, and the mixer 1b, the phase shifter 3, the low-pass filter 4b, the phase shifter 5a, the phase shifter 5b, and the adder 6 are driven. Even when a voltage is applied, no current flows. Therefore, in the low power consumption state, the mixer 1b, the phase shifter 3, the low-pass filter 4b, the phase shifter 5a, and the phase shifter 5
b, and the power consumption in the adder 6 is eliminated, and the power consumption can be reduced.

Next, another configuration of the image rejection mixer of the present invention is shown in FIG. The same parts as those of the image rejection mixer of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The difference from the image rejection mixer shown in FIG. 1 is that a phase shifter 5c is provided instead of the phase shifters 5a and 5b. When the image rejection mixer having this configuration is operating, the phase shifter 5c
Is the same for the IF signal output from the low-pass filter 4a,
The signal operates so as to shift the phase by 90 degrees in the leading direction. As a result, the desired wave components of these two IF signals have the same phase, and the image interference wave components have the opposite phase relationship. Therefore, by combining these two IF signals with the adder 6,
The image interference wave component is removed, and only the desired wave component can be extracted at the output terminal OUT.

FIG. 3 shows still another configuration of the image rejection mixer of the present invention. The same parts as those of the image rejection mixer of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The difference from the image rejection mixer shown in FIG. 1 is that the phase shifter 3 is connected to the local oscillator 2 and the mixer 1b.
In that the phase shifter 5a and the phase shifter 5b are provided between the input terminal IN and the mixer 1b instead of between the input terminal IN and the mixer 1b. In this case, the IF signal included in the output signal of the mixer 1a is a signal delayed by 90 degrees in phase from the IF signal included in the output signal of the mixer 1b.

When the image rejection mixer having this configuration is in the operating state, the phase shifter 5a operates so as to shift the phase of the IF signal output from the low-pass filter 4a by 45 degrees in the leading direction, and the phase shifter 5b operates in the low-pass filter. It operates so that the IF signal output from 4b is shifted by 45 degrees in the delay direction. As a result, the desired wave components of these two IF signals have the same phase, and the image interference wave components have the opposite phase relationship. Therefore, by combining these two IF signals with the adder 6,
The image interference wave component is removed, and only the desired wave component can be extracted at the output terminal OUT.

In the image rejection mixer shown in FIG. 3, the phase shifter 5c used in the image rejection mixer shown in FIG. 2 may be used instead of the phase shifters 5a and 5b. In this case, in the operating state, the phase shifter 5c outputs the I signal output from the low-pass filter 4a.
The phase shift is not changed for the F signal, and the low-pass filter 4a
May be shifted by 90 degrees in the delay direction. As a result, the desired wave components of these two IF signals have the same phase and the image interference wave components have the opposite phase. Therefore, the image interference wave component is removed by combining these two IF signals with the adder 6. , Only the desired wave component can be extracted at the output terminal OUT.

Further, it is conceivable that the phase shifter 3 is provided between the input terminal IN or the local oscillator 2 and the mixer 1a. In this case, however, since the phase shifter 3 must be always on, a bias voltage control circuit is provided. 9 does not control the operation state of the phase shifter 3. For this reason, power consumption is increased as compared with the other embodiments described above.

The above-mentioned phase shifter 5c is replaced with a 90-degree phase shifter 5 provided between the low-pass filter 4b and the adder 6.
It can be replaced by b. In the present invention, the combination of the connection line between the switch 7 and the adder 6 in this case and the 90-degree phase shifter 5b are combined with at least one of the two signals output from the two mixers 1a and 1b. It is assumed that this is included in one mode of the second phase shifting means for shifting the phase of the signal so that the desired waves included in the two signals are in phase with each other. That is, when a phase shifter is not provided between the switch 7 and the adder 6, the connection line between the switch 7 and the adder 6 is included in the second phase shift means.

Next, a receiving apparatus using the image rejection mixer shown in FIG. 1 will be described with reference to FIG. The RF signal received by the antenna 10 is amplified by the low noise amplifier 11, down-converted by the image rejection mixer 12, and output to the band-pass filter 13 as an IF signal. Unnecessary frequency components are removed from the IF signal by the band-pass filter 13, the level of the IF signal is adjusted by the limiter 14, and the IF signal passes through the FM demodulator 15 and the data slicer 16, thereby becoming reception data.

The received data is input to the judging means 17, and the judging means 17 judges whether the receiving apparatus should be in a standby state or a receiving state based on the received data. Controls the state of the rejection mixer. In other words, when the determination means 17 determines to shift to the reception state, the control circuit 8 puts the image rejection mixer 12 into an operating state, and FIG.
Operates as an image rejection mixer.
On the other hand, when the judging means 17 judges to shift to the standby state, the control circuit 8 puts the image rejection mixer 12 into a low power consumption state, and operates as a down-converting mixer shown in FIG. . In the down-converter of FIG. 4 which cannot remove the image interference wave, the same parts as those of the image rejection mixer of FIG.

Therefore, the image rejection mixer 1
2 is in the operating state, the equivalent block diagram of the receiving device is as shown in FIG. 6, and the equivalent block diagram of the receiving device when the image rejection mixer 12 is in the low power consumption state is as shown in FIG. 6 and 7, the same parts as those of the receiving apparatus of FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

The receiving device shown in FIG. 5 can be reduced in power consumption, and thus can be said to be suitable for use as an RFIC for Bluetooth. Bluetooth
In th, there are seven different modes of communication connection,
Information on which mode the receiving device should select is included in the received data. Therefore, if the determination unit 17 can determine whether the image rejection mixer should be in the operating state or the low power consumption state based on the received data, the optimal power consumption can be reduced. Become.

Further, in the present embodiment, the low-pass filters 4a and 4b are provided at the next stages of the mixers 1a and 1b, respectively. However, the present invention is not limited to this. A low-pass filter may be provided between a connection point connected to the output line from the adder 6 and the output terminal OUT, or a low-pass filter is not provided in the image rejection mixer, and the low-pass filter is provided in the next stage of the image rejection mixer. A low-pass filter may be provided.

The present invention is not limited to the phase shift setting of the phase shifters 5a, 5b and 5c used in the present embodiment. The desired wave component of the IF signal is in phase and the image interference wave component is reversed. What is necessary is just to set the phase shift so as to have a phase relationship.

[0033]

According to the present invention, the bypass means for supplying the signal output from the first mixer to the output terminal without passing through the second phase shifting means and the adding means, and the first mixer is provided with the second shifting means. Switch means for selecting whether to be connected to the phase means or the bypass means, and operation of at least the second mixer, the second phase shift means, and the adding means when the switch means selects the bypass means And a control circuit for turning on the operation of at least the second mixer, the second phase shifting means, and the adding means when the switch means selects the second phase means. Therefore, it is possible to switch between the operation state and the low power consumption state. Thereby, when it is not necessary to remove the image interference wave component, the power consumption can be reduced, and energy saving can be achieved.

Further, according to the present invention, the second RF signal or the second local oscillation signal is supplied to the first phase means by 90%.
If the signal is phase-shifted, the control circuit turns off the operation of the first phase-shift means when the switch means selects the bypass means, and selects the second phase-shift means for the switch means. When the first phase shifting means is operating,
Since the state is set to the N state, the operation of the first phase shift means can be set to the OFF state in the low power consumption state. Thereby, energy saving can be further achieved.

According to the present invention, a first low-pass filter is provided between the first mixer and the switch means, and a second low-pass filter is provided between the second mixer and the second phase shift means. Since each low-pass filter is provided, the signal output from the image rejection mixer can be an IF signal only. This facilitates signal processing in a circuit connected to the next stage of the image rejection mixer.

According to the present invention, the supply of the bias voltage to the means whose operation state is controlled by the control circuit is
Since the control circuit performs ON / OFF control, it is possible to perform ON / OFF control of an active element provided in a unit whose operation state is controlled by the control circuit. Thus, even if a drive voltage is applied to the unit whose operation state is controlled by the control circuit, the active element is controlled to be OFF, thereby reducing the power consumption of the unit whose operation state is controlled by the control circuit to zero. Can be.

Further, according to the present invention, the receiving apparatus includes the image rejection mixer that can switch between the operating state and the low power consumption state, and the determination unit that determines whether the apparatus is in the standby state. When the receiving device is in a standby state, the image rejection mixer can be set to a low power consumption state. Thus, power consumption of the receiving device can be reduced, and energy saving can be achieved.

Further, according to the present invention, since the determination means determines whether or not the apparatus is in the standby state based on the received data, it is possible to reliably determine whether or not the apparatus is in the standby state.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an image rejection mixer according to the present invention.

FIG. 2 is a circuit diagram showing another configuration of the image rejection mixer of the present invention.

FIG. 3 is a circuit diagram showing still another configuration of the image rejection mixer of the present invention.

FIG. 4 is a circuit diagram of a down-converting mixer.

FIG. 5 is a circuit diagram of a receiving device of the present invention.

FIG. 6 is an equivalent circuit diagram of the receiving device of FIG. 5 in a receiving state.

FIG. 7 is an equivalent circuit diagram of the receiving device of FIG. 5 in a standby state.

FIG. 8 is a circuit diagram of a conventional image rejection mixer.

[Explanation of symbols]

 1a, 1b mixer 3 phase shifter 4a, 4b low-pass filter 5a-5c phase shifter 6 adder 7 switch 8 control circuit 9 bias voltage control circuit 12 image rejection mixer 17 judgment means IN input terminal OUT output terminal

Claims (6)

[Claims] An RF signal and a local oscillation signal are respectively divided into two signals to obtain four signals, and any one of the four signals is shifted by 90 degrees by a first phase shifting means. Signal generating means for generating a first RF signal, a second RF signal, a first local oscillation signal, and a second local oscillation signal; and the first RF signal, the first local oscillation signal, And a second mixer for multiplying the second R
A second mixer for multiplying an F signal by the second local oscillation signal; and a phase shifter for at least one of two signals output from the first and second mixers, respectively. Second phase shifting means for making the desired waves included in each of the two signals in phase with each other, and two signals respectively output from the first and second mixers passing through the second phase shifting means. An image rejection mixer comprising: an output unit that outputs a signal output from the first mixer to the output terminal without passing through the second phase shift unit and the addition unit. Bypass means; switch means for selecting whether the first mixer is connected to the second phase shift means or the bypass means; and causing the switch means to select the bypass means. At least, the operations of the second mixer, the second phase shifting means, and the adding means are turned off, and when the switch means selects the second phase shifting means, at least the second phase shifting means is selected. And a control circuit for turning on the operations of the second mixer, the second phase shifter, and the adder. 2. The control circuit according to claim 2, wherein said second RF signal or said second local oscillation signal is a signal whose phase has been shifted by 90 degrees by said first phase shift means, and said control circuit has said switch means and said bypass means. Is selected, the operation of the first phase shift means is turned off.
In the F state, when the switch means selects the second phase shift means, the operation of the first phase shift means is turned on.
The image rejection mixer according to claim 1, wherein the mixer is in a state. 3. A first low-pass filter between said first mixer and said switch means, a second low-pass filter between said second mixer and said second phase shift means,
When the control circuit is causing the switch means to select the bypass means, the operation of the second low-pass filter is turned off, and the switch means selects the second phase shift means. 3. The image rejection mixer according to claim 1, wherein the operation of the second low-pass filter is turned on when the signal is present. 4. 4. A supply of a bias voltage to a unit whose operation state is controlled by the control circuit, the control circuit turning on the supply of the bias voltage.
The image rejection mixer according to any one of claims 1 to 3, wherein the image rejection mixer performs / OFF control. 5. A receiving device comprising the image rejection mixer according to claim 1, further comprising: a judging means for judging whether or not the apparatus is in a standby state. The receiving device according to claim 1, wherein said control circuit causes said switch means to select said bypass means in a standby state based on an output signal. 6. The receiving apparatus according to claim 5, wherein said determining means determines whether or not the apparatus is in a standby state based on received data.