JP2013243748A - Semiconductor device and radio communication instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device and a radio communication instrument which can reduce interference to a local oscillator caused by second harmonic of a transmission output.SOLUTION: A semiconductor device includes: first and second transmission paths including first and second transmission amplifiers, respectively; a local oscillator for outputting a carrier signal; a phase shifter for dividing a frequency of the carrier signal into halves to output a plurality of local signals having a phase difference of 90 degrees from one another; and first and second mixer circuits for multiplying the first and second baseband signals by the local signals having phases shifted by 90 degrees from each other. The semiconductor device comprises: a quadrature modulator for combining outputs from the first and second mixer circuits and outputting the resultant; and a 90 degree phase shifter to which the output from the quadrature modulator is input and which obtains 90 degree phase difference outputs each having a phase difference of 90 degrees from each other. The 90 degree phase difference outputs are input to first and second transmission amplifiers and transmission outputs from the first and second transmission paths have a phase difference of 90 degrees from each other and the transmission outputs are combined to generate a radio frequency signal.

Description

  The present application relates to a semiconductor device and a wireless communication device for transmitting a radio frequency signal.

  An RF transceiver LSI is a semiconductor device that transmits a radio frequency signal (RF signal). In recent years, RF transceiver LSIs have been made into one chip, and RF signal transmission, reception, preprocessing of received signals, and the like are integrated into an RF transceiver LSI integrated on a single semiconductor chip. There may be. An example of a transmission configuration in a wireless communication device including such an RF transceiver LSI is shown in FIG.

  The RF transceiver LSI 20 includes a local oscillator 1, a phase shifter 2, mixer circuits 31 and 32, and a transmission amplifier 4. The local oscillator 1 outputs a carrier wave signal. The phase shifter 2 divides the carrier signal by two and outputs local signals that are 90 degrees out of phase with each other. The mixer circuits 31 and 32 multiply the baseband signals BB-I and BB-Q input from the baseband signal processing unit 10 with the local signals, respectively. The outputs of the mixer circuits 31 and 32 are combined and output from the RF transceiver LSI 20 via the transmission amplifier 4. The transmission output of the RF transceiver LSI 20 is radiated from the antenna 40 after the frequency component of the fundamental wave is extracted by the filter 30.

  A configuration that performs modulation including the mixer circuits 31 and 32 as in the RF transceiver LSI 20 is called a quadrature modulator. In relation to such a quadrature modulator, Patent Documents 1, 2, and 3 are disclosed.

JP 2007-49514 A JP 2005-184141 A Japanese Patent Laid-Open No. 10-145103

  In FIG. 6, the RF transceiver LSI 20 divides the carrier signal output from the local oscillator 1 by 2 by the phase shifter 2 to obtain a local signal. That is, the local oscillator 1 outputs a carrier wave signal having a frequency 2fLO that is twice the frequency fLO of the local signal. As a result, the frequency fout of the transmission output equal to the frequency fLO of the local signal is separated from the frequency 2fLO of the local oscillator 1 to suppress interference of the transmission output with the local oscillator 1.

  However, due to the non-linearity of the transmission amplifier 4, a second harmonic of frequency 2fLO is generated at the transmission output of the RF transceiver LSI 20. The generated second harmonic interferes with the local oscillator 1 as shown by a broken line in FIG. 6 and degrades the transmission signal quality.

  The present invention has been proposed in view of the above problems, and provides a semiconductor device capable of reducing interference with a local oscillator due to second harmonics of a transmission output, and a radio communication device including the semiconductor device. With the goal.

  A semiconductor device disclosed in the present application is a semiconductor device that transmits a radio frequency signal, and includes a first transmission path including a first transmission amplifier, and a second transmission path including a second transmission amplifier. A local oscillator that outputs a carrier wave signal, a phase shifter that divides the carrier wave signal by two and outputs a plurality of local signals having a phase difference of 90 degrees, and first and second baseband signals Are combined with the local signals that are 90 degrees out of phase with each other, and the output of the first mixer circuit and the output of the second mixer circuit are combined and output. And a 90-degree phase shifter that receives the output of the quadrature modulator and obtains a 90-degree phase difference output having a 90-degree phase difference. Input to one transmission amplifier and the second transmission amplifier The transmission output of the first transmission path and the transmission output of the second transmission path have a phase difference of 90 degrees, and the transmission output of the first transmission path and the transmission output of the second transmission path Are combined to obtain the radio frequency signal. Further, the wireless communication device disclosed in the present application includes the semiconductor device, a baseband signal processing unit, a filter that extracts a frequency component of a fundamental wave included in the radio frequency signal, and an antenna that radiates the radio frequency signal. And comprising.

  According to the disclosed semiconductor device and wireless communication device, two transmission paths having a phase difference of 90 degrees are provided, the outputs are combined to cancel the second harmonic, and the transmission output second harmonic. Can reduce interference with the local oscillator.

It is a circuit block diagram of a 1st embodiment. It is a circuit block diagram of a 2nd embodiment. It is a circuit block diagram of a 3rd embodiment. It is a circuit block diagram of a 4th embodiment. It is an example of RC polyphase filter. It is a circuit block diagram which shows a prior art example.

  FIG. 1 shows a circuit block diagram of the first embodiment. The RF transceiver LSI 21 includes a local oscillator 1, a phase shifter 2, mixer circuits 31, 32, 33, 34, transmission amplifiers 41, 42, and an LC series resonance circuit 5. The local oscillator 1 outputs a carrier wave signal. The phase shifter 2 divides the carrier signal by two and outputs local signals LO0, LO90, and LO180 having a phase difference of 90 degrees. Here, the phase shifter 2 is, for example, an MS-T-FF (master / slave / toggle flip-flop) type 1/2 frequency divider. When the MS-T-FF ½ frequency divider is used for the phase shifter 2, it is efficient because it can generate local signals that are orthogonal to each other at the same time. 4-phase output is possible. The mixer circuits 31 and 32 multiply the baseband signals BB-I and BB-Q input from the baseband signal processing unit 10 with local signals LO0 and LO90 that are 90 degrees out of phase with each other. Further, the mixer circuits 33 and 34 multiply the baseband signals BB-I and BB-Q input from the baseband signal processing unit 10 with local signals LO90 and LO180, respectively, that are 90 degrees out of phase with each other. The outputs of the mixer circuits 31 and 32 and the outputs of the mixer circuits 33 and 34 are combined, and the combined outputs are input to the transmission amplifiers 41 and 42, respectively. In the LSI chip, the output of the transmission amplifier 41 and the output of the transmission amplifier 42 are connected by the LC series resonance circuit 5, and the output of the transmission amplifier 41 is connected to the output of the transmission amplifier 42 via the 90-degree phase shifter 6 outside the LSI. The output is combined. Here, the LC series resonance circuit 5 has a resonance frequency at a frequency 2fLO that is twice the frequency fLO of the local signal. The 90-degree phase shifter 6 is, for example, a substrate pattern or a discrete component. The synthesized transmission output of the RF transceiver LSI 21 is radiated from the antenna 40 after the frequency component of the fundamental wave is extracted by the filter 30.

  As described above, the RF transceiver LSI 21 includes two quadrature modulators, that is, the first quadrature modulator including the mixer circuits 31 and 32 and the second quadrature modulator including the mixer circuits 33 and 34. . Then, the first quadrature modulator has a phase difference of 90 degrees relative to the local signal input to the second quadrature modulator. Are inputted with local signals LO0 and LO90 of 0 degree phase and 90 degree phase, and local signals LO90 and LO180 of 90 degree phase and 180 degree phase are inputted to the second quadrature modulator. Thus, the transmission output of the first transmission path on the side of the transmission amplifier 41 connected to the first quadrature modulator, and the transmission output of the second transmission path on the side of the transmission amplifier 42 connected to the second quadrature modulator Can have a phase difference of 90 degrees.

Subsequently, the synthesis of the transmission outputs of the first and second transmission paths having a phase difference of 90 degrees will be described. The output Vout when the input signal Vin is input to the nonlinear circuit is
^{Vout = A · Vin + B ·} Vin 2 + C · Vin 3 + D · Vin 4 + ···
It is expressed. Here, the second and subsequent items are distortion components. An input signal having a phase difference of 90 degrees input to the transmission amplifiers 41 and 42 which are nonlinear circuits is applied to the above equation as sin (ωt) and cos (ωt), and a combined output is calculated. Ignoring the higher-order components and ignoring them, and calculating up to the fourth-order term, the combined output is
Vout = A (sin (ωt) + cos (ωt)) + B (sin ² (ωt) + cos ² (ωt)) + C (sin ³ (ωt) + cos ³ (ωt)) + D (sin ⁴ (ωt) + cos ⁴ (ωt) ))
It becomes. here,
sin ² (ωt) = (1−cos (2ωt)) / 2
cos ² (ωt) = (1 + cos (2ωt)) / 2
sin ³ (ωt) = ( ³ sin (ωt) −sin (3ωt)) / 4
cos ³ (ωt) = ( ³ cos (ωt) + cos (3ωt)) / 4
sin ⁴ (ωt) = (3-4cos (2ωt) + cos (4ωt)) / 8
cos ⁴ (ωt) = (3 + ⁴ cos (2ωt) + cos (4ωt)) / 8
Therefore, the 2ωt component, that is, the second harmonic is canceled. In this way, since the second harmonics included in the transmission outputs of the first and second transmission paths having a phase difference of 90 degrees are opposite to each other, the second harmonics can be canceled when they are combined. it can. Therefore, interference with the local oscillator 1 due to the second harmonic of the transmission output can be reduced.

  In the present embodiment, only the second harmonic is generated by the LC series resonance circuit 5 having a resonance frequency at twice the frequency fLO of the local signal, that is, a frequency 2fLO equal to the second harmonic in the LSI chip. It is the composition which cancels by combining. The fundamental wave is synthesized outside the LSI by aligning the phases by the 90-degree phase shifter 6. When the transmission output of the first transmission path and the transmission output of the second transmission path are combined with the phase shifted by 90 degrees, a power loss of about 1.5 dB occurs. On the other hand, in this embodiment, after canceling the second harmonic in the LSI chip, the extracted fundamental wave is combined with the same phase to reduce power loss. Further, the LC series resonance circuit 5 in this case does not need to have a high Q value, and can be downsized.

  FIG. 2 shows a circuit block diagram of the second embodiment. The RF transceiver LSI 22 of the second embodiment is an embodiment in which the RF transceiver LSI 21 of the first embodiment has a differential configuration. In FIG. 2, the same reference numerals are given to the respective parts corresponding to FIG. The phase shifter 2 divides the carrier signal by 2 and outputs local signals LO0, LO90, LO180, and LO270 having a phase difference of 90 degrees. The mixer circuit 31 multiplies the baseband signal BB-I input from the baseband signal processing unit 10 and its inverted signal BB-XI by the local signals LO0 and LO180, respectively. The mixer circuit 32 multiplies the baseband signal BB-Q input from the baseband signal processing unit 10 and its inverted signal BB-XQ by the local signals LO90 and LO270, respectively. The mixer circuit 33 multiplies the baseband signal BB-I input from the baseband signal processing unit 10 and its inverted signal BB-XI by the local signals LO90 and LO270, respectively. The mixer circuit 34 multiplies the baseband signal BB-Q input from the baseband signal processing unit 10 and its inverted signal BB-XQ by the local signals LO180 and LO0, respectively. The outputs of the mixer circuits 31 and 32 and the outputs of the mixer circuits 33 and 34 are combined with the non-inverted signal and the inverted signal, respectively, and the combined outputs are input to the transmission amplifiers 41 and 42, respectively. The output of the transmission amplifier 41 and the output of the transmission amplifier 42 are synthesized by a non-inverted signal and an inverted signal. The differential transmission output of the RF transceiver LSI 22 is converted into a single-ended output by the transformer 7, and the fundamental frequency component is extracted by the filter 30 and then radiated from the antenna 40.

  With the above configuration, in the differentially configured RF transceiver LSI 22, the transmission output of the first transmission path on the side of the transmission amplifier 41 connected to the first quadrature modulator including the mixer circuits 31 and 32, and the mixer circuits 33 and 34. The transmission output of the second transmission path on the side of the transmission amplifier 42 connected to the second quadrature modulator including the phase difference of 90 degrees can be provided. Therefore, as described in the first embodiment, it is possible to cancel the second harmonic generated in the transmission amplifiers 41 and 42 and reduce interference with the local oscillator 1 due to the second harmonic of the transmission output. it can.

  FIG. 3 shows a circuit block diagram of the third embodiment. The RF transceiver LSI 23 of the third embodiment is an embodiment in which a baseband signal input from the baseband signal processing unit 10 has a phase difference of 90 degrees. In FIG. 3, each part corresponding to FIG. The same reference numerals are given. In the baseband signal surrounded by a broken line, the baseband signals BB-I (0) and BB-I (90) have a phase difference of 90 degrees, and the baseband signals BB-Q (0) and BB-Q ( 90) have a phase difference of 90 degrees. The phase shifter 2 divides the carrier signal by two and outputs local signals LO0 and LO90 that are 90 degrees out of phase with each other. The mixer circuits 31 and 32 multiply the baseband signals BB-I (0) and BB-Q (0) by the local signals LO0 and LO90, respectively. The mixer circuits 33 and 34 multiply the baseband signals BB-I (90) and BB-Q (90) by the local signals LO0 and LO90, respectively. The outputs of the mixer circuits 31 and 32 and the outputs of the mixer circuits 33 and 34 are combined, and the combined outputs are input to the transmission amplifiers 41 and 42, respectively. The output of the transmission amplifier 41 and the output of the transmission amplifier 42 are combined and become the transmission output of the RF transceiver LSI 23. The transmission output of the RF transceiver LSI 23 is radiated from the antenna 40 after the frequency component of the fundamental wave is extracted by the filter 30.

  Even with the configuration of the present embodiment in which the input baseband signal has a phase difference of 90 degrees, the RF transceiver LSI 23 can have a phase difference of 90 degrees between the two transmission paths. That is, the transmission output of the first transmission path on the side of the transmission amplifier 41 connected to the first quadrature modulator including the mixer circuits 31 and 32 and the transmission connected to the second quadrature modulator including the mixer circuits 33 and 34 A phase difference of 90 degrees can be given to the transmission output of the second transmission path on the amplifier 42 side. Therefore, the effect of canceling the second harmonic generated in the transmission amplifiers 41 and 42 can be obtained, and interference with the local oscillator 1 due to the second harmonic of the transmission output can be reduced.

  FIG. 4 shows a circuit block diagram of the fourth embodiment. The RF transceiver LSI 24 includes a local oscillator 1, a phase shifter 2, mixer circuits 31 and 32, a 90-degree phase shifter 8, and transmission amplifiers 41 and 42. The local oscillator 1 outputs a carrier wave signal. The phase shifter 2 divides the carrier signal by 2 and outputs local signals LO0, LO90, LO180, and LO270 having a phase difference of 90 degrees. The mixer circuit 31 multiplies the baseband signal BB-I input from the baseband signal processing unit 10 and its inverted signal BB-XI by the local signals LO0 and LO180, respectively. The mixer circuit 32 multiplies the baseband signal BB-Q input from the baseband signal processing unit 10 and its inverted signal BB-XQ by the local signals LO90 and LO270, respectively. The outputs of the mixer circuits 31 and 32 are combined with the non-inverted signal and the inverted signal, and the combined outputs are respectively input to the + Iin terminal and the −Iin terminal of the 90 ° phase shifter 8. Further, the + Qin terminal and the −Qin terminal of the 90-degree phase shifter 8 are grounded.

  The 90 degree phase shifter 8 is, for example, an RC polyphase filter. FIG. 5 shows an example of a second-order RC polyphase filter. When the RC polyphase filter illustrated in FIG. 5 is used for the 90-degree phase shifter 8, an output having a phase difference of 90 degrees from the + Iout terminal can be obtained at the + Qout terminal, and the −Iout terminal at the −Qout terminal. And an output having a phase difference of 90 degrees. Outputs from the + Iout terminal and −Iout terminal and outputs from the + Qout terminal and −Qout terminal are input to the transmission amplifiers 41 and 42, respectively. The configuration after the transmission amplifiers 41 and 42 is the same as that of the second embodiment in FIG.

  Even in the configuration of this embodiment in which the 90-degree phase shifter 8 is provided at the output of the quadrature modulator including the mixer circuits 31 and 32 and an output having a phase difference of 90 degrees is obtained, the RF transceiver LSI 24 can also provide an output between two transmission paths. Can have a phase difference of 90 degrees. In other words, the transmission output of the first transmission path on the transmission amplifier 41 side and the transmission output of the second transmission path on the transmission amplifier 42 side can have a phase difference of 90 degrees. Therefore, the effect of canceling the second harmonic generated in the transmission amplifiers 41 and 42 can be obtained, and interference with the local oscillator 1 due to the second harmonic of the transmission output can be reduced.

Here, the correspondence with the claims is as follows.
The transmission amplifiers 41 and 42 are examples of the first and second transmission amplifiers described in the claims, respectively. The mixer circuits 31 and 32 are examples of the first and second mixer circuits described in the claims, respectively, and the mixer circuits 33 and 34 are examples of the third and fourth mixer circuits described in the claims, respectively. is there. The RC polyphase filter is an example of a 90-degree phase shifter recited in the claims. The LC series resonance circuit 5 is an example of a series resonance circuit described in the claims.

  As described above in detail, according to the first to fourth embodiments, the second harmonic is provided by providing two transmission paths having a phase difference of 90 degrees and combining the outputs. And the interference to the local oscillator 1 due to the second harmonic of the transmission output can be reduced. In the above-described embodiment, the influence of the reflected wave returning into the LSI chip due to the mismatch of the filter 30 that extracts the frequency component of the fundamental wave outside the RF transceiver LSIs 21 to 24 can be suppressed. Since the second harmonic can be canceled, it is more effective in constant amplitude modulation such as FSK (frequency shift keying) where a certain amount of distortion is allowed. In RF transceiver LSIs that are becoming one-chip, a large isolation area is secured to ensure isolation between the transmission amplifier and the local oscillator, and extra power is consumed to improve the linearity of the transmission amplifier. Therefore, a simple configuration can be adopted. Therefore, the cost and size of the RF transceiver LSI can be reduced.

  Needless to say, the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the spirit of the present invention.

  For example, in the embodiment, the baseband signal processing unit 10 may be configured to be incorporated in the RF transceiver LSIs 21 to 24.

  In the above-described embodiment, the case of the direct modulation method in which the local signal is directly modulated has been described. However, the present invention is not limited to this and may be applied to an indirect modulation method.

  In the fourth embodiment, the 90-degree phase shifter 8 is not limited to the RC polyphase filter illustrated in FIG. Any phase shifter that operates linearly may be used.

  In addition, it goes without saying that the embodiments may be appropriately combined and used. For example, the configuration in which the transmission output is synthesized using the LC series resonance circuit 5 and the 90-degree phase shifter 6 in the first embodiment may be applied to other embodiments.

DESCRIPTION OF SYMBOLS 1 Local oscillator 2 Phase shifter 5 LC series resonance circuit 6 90 degree phase shifter 7 Transformer 8 90 degree phase shifter 10 Baseband signal processing part 21-24 RF transceiver LSI
30 Filter 31-34 Mixer circuit 40 Antenna 41, 42 Transmitting amplifier

Claims (4)

A semiconductor device for transmitting radio frequency signals,
A first transmission path including a first transmission amplifier;
A second transmission path including a second transmission amplifier;
A local oscillator that outputs a carrier wave signal;
A phase shifter that divides the carrier wave signal by 2 and outputs a plurality of local signals having a phase difference of 90 degrees;
First, first, it includes a second mixer circuit, wherein an output of the first mixer circuit a second mixer and the second baseband signal, multiplies the local signal and each shifted in phase by 90 degrees from each other A quadrature modulator that combines and outputs the output of the circuit;
A 90 degree phase shifter which receives the output of the quadrature modulator and obtains a 90 degree phase difference output having a 90 degree phase difference;
With
The 90-degree phase difference output is input to the first transmission amplifier and the second transmission amplifier,
The transmission output of the first transmission path and the transmission output of the second transmission path have a phase difference of 90 degrees, and the transmission output of the first transmission path and the transmission output of the second transmission path To obtain the radio frequency signal. The semiconductor device according to claim 1, wherein the 90-degree phase shifter is an RC polyphase filter. A semiconductor device for transmitting radio frequency signals;
A baseband signal processing unit for generating the first and second baseband signals;
A filter for extracting a frequency component of a fundamental wave contained in the radio frequency signal;
An antenna for radiating the radio frequency signal;
With
The semiconductor device includes:
A first transmission path including a first transmission amplifier;
A second transmission path including a second transmission amplifier;
A local oscillator that outputs a carrier wave signal;
A phase shifter that divides the carrier wave signal by 2 and outputs a plurality of local signals having a phase difference of 90 degrees;
First, first, it includes a second mixer circuit, wherein an output of the first mixer circuit a second mixer and the second baseband signal, multiplies the local signal and each shifted in phase by 90 degrees from each other A quadrature modulator that combines and outputs the output of the circuit;
A 90 degree phase shifter which receives the output of the quadrature modulator and obtains a 90 degree phase difference output having a 90 degree phase difference;
With
The 90-degree phase difference output is input to the first transmission amplifier and the second transmission amplifier,
The transmission output of the first transmission path and the transmission output of the second transmission path have a phase difference of 90 degrees, and the transmission output of the first transmission path and the transmission output of the second transmission path To obtain the radio frequency signal. A series resonance circuit having a resonance frequency at twice the frequency of the local signal and inserted between outputs of the first transmission amplifier and the second transmission amplifier in the semiconductor device;
Second harmonic wave generated by the transmission output of the first transmission power and the second transmission path of the transmission path and combined by the series resonant circuit, the transmission output and the second of said first transmission path The wireless communication device according to claim 3, wherein the fundamental wave included in the transmission output of the transmission path is synthesized by aligning the phases.

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