JP4521959B2 - Mixer circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mixer circuit used in a frequency converter of a wireless communication device.
[0002]
[Prior art]
FIG. 5 is a block diagram showing a configuration example of a main part of a receiving circuit in a wireless communication apparatus provided with a conventional high frequency mixer. The high-frequency mixer 101 receives the reception signal as the input signal F1 and the frequency conversion local signal F2, and the high-frequency (RF) input signal is frequency-converted to an intermediate frequency (IF). A variable gain amplifier 102 and a quadrature demodulator 103 are provided at the subsequent stage of the high frequency mixer 101. After the signal level is adjusted by the variable gain amplifier 102, the signal is demodulated by the quadrature demodulator 103 to be quadrature signal components of Iout and Qout. An output signal of a baseband frequency consisting of The quadrature demodulator 103 is connected to a quadrature modulator 104 that functions as a phase adjusting unit.
[0003]
A high-frequency mixer 101 generally used in such a wireless communication apparatus uses a distortion characteristic of a single transistor called a down converter or the like, and a standard transistor composite circuit such as a Gilbert cell is mainly used. . This type of mixer basically uses a local (local transmitter in the apparatus) side input level in a saturated state, and obtains an output that matches the input signal.
[0004]
The quadrature modulator 104 receives the frequency conversion local signal F3 and also receives phase control signals PI and PQ such as DC signals. The frequency conversion local signal F3 is doubled by the multiplier 111 and separated into phase components of 0 degrees and 90 degrees by the phase divider 112, and multiplied by the phase control signals PI and PQ by the low frequency mixers 113 and 114, respectively. Are then synthesized by the synthesis adder circuit 115 and output as a local signal having a desired phase. A local signal having a predetermined phase from the quadrature modulator 104 is doubled by the multiplier 116 of the quadrature demodulator 103 and separated into phase components of 0 degrees and 90 degrees by the phase divider 117, and demodulating mixers 118 and 119, respectively. Is input. In the demodulating mixers 118 and 119, the phase components of 0 degrees and 90 degrees and the received signal of the intermediate frequency are multiplied to generate Iout and Qout of the output signal.
[0005]
In the receiving circuit having such a configuration, when phase adjustment is performed, a signal having a predetermined value is input to the phase control signals PI and PQ, and the phase of the local signal input to the quadrature demodulator 103 is changed. In this case, since the phase and amplitude of the signal influence each other, it is necessary to change the phase while adjusting the gain by the variable gain amplifier 102. Further, on the IQ plane as shown in FIG. 6, assuming that the bias voltage point is zero, when the coordinates of the phase control signals PI and PQ pass the zero point, the output of the quadrature modulator 104 becomes zero and quadrature modulation is performed. Since the phase is changed to an unintended value by the device 104, the phase control signals PI and PQ must be moved at a point equidistant from the bias voltage point. In this case, for example, if the phase adjustment is performed by changing the phase control signals PI and PQ in units of 5 degrees, a total of 72 commands are given to control from the A point to the opposite phase, such as the B point. The signal needs to be changed. Further, if an N-fold frequency input type element is used for the quadrature modulator 104 or the quadrature demodulator 103, the phase adjustment range is limited to 90 to 180 degrees. Don't be.
[0006]
[Problems to be solved by the invention]
As described above, in a receiving circuit using a conventional high-frequency mixer, it is necessary to change the control signal in multiple steps and gradually bring it closer to the target value when adjusting the phase, which requires time and effort. . Further, since the phase changes with changes in the amplitude of the signal, it is necessary to adjust the gain of the circuit in accordance with the change in the signal level caused by this phase change after using a variable gain amplifier or the like. By providing such a gain adjusting means, there is a problem that the circuit scale becomes large.
[0007]
The present invention has been made in view of the above circumstances, and can easily control the phase and amplitude of a signal to a desired value, can omit a variable gain amplifier and the like, and can reduce the circuit scale. An object of the present invention is to provide a mixer circuit capable of performing the above.
[0008]
[Means for Solving the Problems]
A first aspect of the present invention is a mixer circuit that performs frequency conversion of an input signal based on a local signal having a predetermined frequency, and has a characteristic that includes at least one of the level and phase of the local signal by a DC or AC control signal. And a characteristic control circuit that adjusts characteristics including at least one of a level and a phase of the output signal that has been changed and subjected to the frequency conversion.
[0009]
Second, the characteristic control circuit is provided in a stage preceding a mixer that performs frequency conversion by mixing the local signal and the input signal.
[0010]
Third, a mixer circuit for performing frequency conversion of an input signal based on a local signal having a predetermined frequency, wherein at least one of a level and a phase of the local signal is changed by a DC or AC control signal, and the frequency conversion is performed. An amplitude / phase control circuit for adjusting at least one of a level and a phase of the output signal performed is provided.
[0011]
Fourth, the amplitude / phase control circuit is provided in a stage preceding a mixer that performs frequency conversion by mixing the local signal and the input signal.
[0012]
Further, fifthly, the phase component generating means for generating a predetermined phase component for the local signal, the phase component and the control signal corresponding to the phase component are mixed, and the adjusted predetermined phase component and amplitude component are mixed. And a second mixer that generates a frequency-converted output signal by mixing the output of the first mixer and the input signal. To do.
[0013]
Alternatively, sixth, phase component generating means for generating a predetermined plurality of phase components for the local signal, and a first mixer for respectively mixing the plurality of phase components and a plurality of control signals corresponding thereto Combining a plurality of the mixed phase component signals and outputting a local signal having the adjusted predetermined phase component and amplitude component, and mixing the output of the combining means and the input signal And a second mixer for generating a frequency-converted output signal.
[0014]
Seventh, the amplitude / phase control circuit includes a quadrature modulator configured to include the phase component generation means, the first mixer, and the synthesis circuit.
[0015]
Eighth, the phase component generation means includes a multiplier that multiplies a local signal having a predetermined frequency, and a phase divider that divides the multiplied signal and outputs a local signal having a predetermined phase component. It is characterized by becoming.
[0016]
Further, as the phase component generation means, means for generating local signals of a plurality of phases, input terminals for inputting local signals of a plurality of phases, and the like can be provided. The above-described configuration can be formed on a semiconductor chip and incorporated into a single element. It should be noted that the accuracy can be further improved by increasing the number of control signals, that is, the number of dimensions of parameters for controlling the phase and amplitude.
[0017]
With the above configuration, the phase and amplitude of the signal can be easily controlled to desired values, and the variable gain amplifier and the like can be omitted, so that the circuit scale can be reduced.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a mixer circuit according to the first embodiment of the present invention.
[0019]
The mixer circuit of this embodiment is a configuration example of a multi-dimensional high-frequency mixer 11 having a phase / amplitude adjustment function for adjusting a phase and an amplitude by a control signal for controlling a plurality of dimensional values in an IQ plane of an input signal. It is. The multidimensional high-frequency mixer 11 includes a high-frequency mixer 12, a quadrature modulator 13 including a component surrounded by a wavy line in FIG. 1, and a multiplier 14. The quadrature modulator 13 includes a synthesis adder 15, low frequency mixers 16 and 17, a phase divider 18, and buffer amplifiers 19 and 20.
[0020]
The operation of this multidimensional high frequency mixer 11 will be described. A local signal F2 for frequency conversion of a predetermined frequency output from a local oscillator in the apparatus is input to the multiplier 14 and multiplied, and input to the phase divider 18 to be divided. Here, for example, the local signal F2 is doubled to generate two phase components of 0 degree and 90 degrees. In order to generate phase components of 0 degrees and 90 degrees orthogonal to each other, it is possible to generate a signal shifted by a half cycle by multiplying the local signal by two. It is also possible to supply a plurality of phase local signals having corresponding phase components without providing the multiplier and the phase divider.
[0021]
Further, after phase gain control signals P1 and P2 of a DC signal having a predetermined magnitude are input and filtered by buffer amplifiers 19 and 20, respectively, unnecessary noise components are removed, and then low frequency mixers 16 and 17 are used. Is input. In the low frequency mixers 16 and 17, the amplitudes of the phase gain control signals P1 and P2 are multiplied by the phase components of 0 degrees and 90 degrees of the local signal from the phase divider 18, respectively, and the magnitudes of the respective phase gain control signals are obtained. An output signal converted to a level suitable for this is input to the synthesis adder 15. Note that the phase gain control signals P1 and P2 can be low-frequency AC signals (AC signals) in addition to DC signals (DC signals).
[0022]
In the synthesis adder 15, the local signals having the respective phases and amplitudes from the low frequency mixers 16 and 17 are added and input to the high frequency mixer 12 as local signals having desired phase change characteristics and amplitude characteristics. In the high frequency mixer 12, the high frequency (RF) input signal F1 is multiplied by the local signal whose phase and amplitude are adjusted as described above, and the output level is adjusted by the local signal based on the signal level of the input signal F1. As a signal having phase characteristics corresponding to the phase of the local signal, an output signal S1 frequency-converted to an intermediate frequency (IF) is obtained.
[0023]
Next, the configuration and operation when the above mixer circuit is used in a receiving circuit of a wireless communication device will be described. FIG. 2 is a block diagram showing a configuration of a receiving circuit using the mixer circuit of this embodiment.
[0024]
A quadrature demodulator 21 is provided at the subsequent stage of the multi-dimensional high-frequency mixer 11, and the output signal S1 of the multi-dimensional high-frequency mixer 11 is demodulated by the quadrature demodulator 21 to output a baseband frequency composed of quadrature signal components Iout and Qout. A signal S2 is output. The quadrature demodulator 21 includes demodulating mixers 22 and 23, a multiplier 24, and a phase divider 25.
[0025]
The orthogonal demodulator 21 receives the local signal F3 for frequency conversion, is multiplied by a multiplier 24 (here, multiplied by 2), and is separated into phase components of 0 degrees and 90 degrees by a phase divider 25, respectively. Input to mixers 22 and 23. In the demodulating mixers 22 and 23, the phase components of 0 degree and 90 degrees of the local signal and the output signal S1 of the intermediate frequency are respectively multiplied and converted to output the baseband frequency having the signal components of Iout and Qout. A signal S2 is generated and output. Here, the relationship among the frequencies of the input signal F1, the local signal F2 for frequency conversion from the high frequency to the intermediate frequency, and the local signal F3 for frequency conversion from the intermediate frequency to the baseband frequency is F1-F2 = F3 or F2- F1 = F3 is set.
[0026]
In the configuration of the present embodiment as described above, by setting the phase gain control signals P1 and P2 in the multidimensional high-frequency mixer 11, the levels of the I component and Q component of the local signal for frequency conversion are made independent of each other. Phase adjustment and amplitude adjustment can be easily performed so that a local signal having a desired phase and amplitude can be obtained. In this case, in the IQ plane as shown in FIG. 3, even when adjusting from the point A to the opposite phase like the point B, the phase adjustment can be performed by linearly changing the phase control signal. Therefore, it is possible to control so as to obtain a desired phase only by giving one command while maintaining the stability. Therefore, it is possible to save the trouble of performing the phase adjustment by changing the control signal in multiple stages, which has been necessary in the past. Further, since the quadrature demodulator 21 provided in the receiving unit can be a general-purpose one, it is not limited to the one with a built-in input synchronous multiplication circuit as in the conventional example shown in FIG. Improve and reduce costs.
[0027]
FIG. 4 is a block diagram showing a configuration of a mixer circuit according to the second embodiment of the present invention. The second embodiment is a configuration example in which the phase and amplitude are adjusted using three phase gain control signals P1, P2, and P3.
[0028]
In the second embodiment, in addition to the configuration of the first embodiment shown in FIG. 1, a buffer amplifier 34 and a low frequency mixer 35 corresponding to the third phase gain control signal P3 are provided, and this phase gain control signal P3. A phase divider 32 that generates 60 degree phase components for multiplying by 0 and 90 degrees, and a frequency conversion local signal F2 multiplied by 2 and 3 to generate a 60 degree phase component And a multiplier 33.
[0029]
According to the configuration of the second embodiment, similarly to the first embodiment, the phase and gain of the receiving circuit can be adjusted by arbitrarily setting the phase and amplitude of the local signal by a simple procedure, and control can be performed. By increasing the number of signals, more precise control becomes possible, so that the adjustment accuracy of the phase and gain can be improved.
[0030]
In this embodiment, three or more control signals for controlling the phase and gain of the circuit can be used to further improve the accuracy. Conversely, even if only one control signal is used, the adjustment range is limited. It is possible to control the phase and the like to a desired value.
[0031]
As described above, in this embodiment, the phase / amplitude adjusting means configured by a circuit such as a quadrature modulator is provided on the local (local transmitter in the apparatus) side, and this is controlled by a single or a plurality of control signals. Therefore, the mixer output signal level, phase, time variation, orthogonal axis displacement, etc. can be easily adjusted to the desired value. realizable.
[0032]
The configuration of the present embodiment can be configured by forming a circuit including the multi-dimensional high-frequency mixers 11 and 31 having a phase / amplitude adjustment function on a semiconductor chip or the like and incorporating the circuit into a single element. Further downsizing of the apparatus can be achieved.
[0033]
According to this embodiment, a signal characteristic adjustment function by changing the level of a local signal is added to a mixer that has conventionally only had a single frequency conversion function, so that a desired phase, amplitude, etc. can be obtained. The value can be easily controlled, the variable gain control circuit usually provided in the subsequent stage can be eliminated, and the configuration of the phase adjustment circuit can be simplified. Further, when there is an orthogonal distortion in the input signal, the distortion can be eliminated by giving reverse characteristics in the same procedure. In this case, a plurality of parameters such as phase and amplitude can be controlled simultaneously and independently by a small number of control signals input to a quadrature modulator or the like. Furthermore, it is possible to improve the adjustment accuracy by increasing the number of control signals.
[0034]
【The invention's effect】
As described above, according to the present invention, the phase and amplitude of a signal can be easily controlled to desired values, and a variable gain amplifier and the like can be omitted, so that the circuit scale can be reduced. An effect of providing a mixer circuit is obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a mixer circuit according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a receiving circuit using the mixer circuit of the present embodiment.
FIG. 3 is an explanatory diagram of an IQ plane for explaining an example of phase and amplitude adjustment operation in the present embodiment;
FIG. 4 is a block diagram showing a configuration of a mixer circuit according to a second embodiment of the present invention.
FIG. 5 is a block diagram illustrating a configuration example of a main part of a receiving circuit including a conventional high-frequency mixer.
FIG. 6 is an explanatory diagram of an IQ plane for explaining an example of a phase and amplitude adjustment operation in a conventional example.
[Explanation of symbols]
11, 31 Multi-dimensional high frequency mixer 12 High frequency mixer 13 Quadrature modulator 14 Multiplier 15 Synthetic adder 16, 17, 35 Low frequency mixer 18 Phase divider 19, 20, 34 Buffer amplifier 21 Quadrature demodulator 22, 23 Demodulation mixer 24 multiplier 25 phase divider

Claims (3)

A mixer circuit that performs frequency conversion of an input signal based on a local signal of a predetermined frequency,
The phase and amplitude of the local signal are changed by a DC or AC control signal for controlling a plurality of dimension values on the IQ plane of the input signal, and the phase and amplitude of the output signal subjected to the frequency conversion are adjusted. with an amplitude-phase control circuit,
As the amplitude / phase control circuit, phase component generating means for generating a predetermined phase component for the local signal, the phase component and a control signal corresponding to the phase component are mixed, and the adjusted predetermined phase component A quadrature modulator configured to include a first mixer that outputs a local signal having an amplitude component;
A second mixer that mixes the output of the first mixer and the input signal to generate a frequency-converted output signal;
A mixer circuit in which the amplitude / phase control circuit is provided in front of the second mixer. As the amplitude / phase control circuit, phase component generation means for generating a plurality of predetermined phase components for the local signal, and a plurality of phase components and a plurality of control signals corresponding thereto are respectively mixed. A quadrature modulator configured to synthesize a mixed signal of a plurality of phase components and to output a local signal having a predetermined phase component and amplitude component adjusted. Prepared,
The second mixer, the mixer circuit according output by mixing the input signal to claim 1 that generates a frequency-converted output signal of said combining means. The phase component generation unit includes a multiplier that multiplies a local signal having a predetermined frequency, and a phase divider that divides the multiplied signal and outputs a local signal having a predetermined phase component. Item 3. The mixer circuit according to Item 1 or 2 .

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