JP2010258684A - Radio frequency integrated circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently reduce a phase error in a radio frequency integrated circuit. <P>SOLUTION: The radio frequency integrated circuit includes: a transmitting part which includes a voltage-controlled oscillator for generating an oscillation frequency signal of an oscillation frequency corresponding to given voltage and generates a radio frequency signal obtained by superposing a signal wave on a carrier obtained by dividing the oscillation frequency signal; a power amplifier which amplifies the radio frequency signal from a radio frequency circuit; and a reducing means which reduces a harmonic component of the same frequency as at least the oscillation frequency that turns from the power amplifier into the transmitting part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for using a radio frequency integrated circuit together with a power amplifier.

  An example of the configuration of a general RFIC (Radio Frequency Integrated Circuit) is shown in FIG. Referring to the figure, a transmitter (RFIC Tx) of this RFIC is provided with a PLL (Phase Locked Loop) having a VCO (Voltage Control Oscillator). The transmission unit generates an RF (Radio Frequency) signal from a carrier wave generated by dividing the oscillation frequency of the VCO by a predetermined division ratio and a baseband signal. This RF signal is input from the transmitter to the power amplifier through the RF line, and is amplified by the power amplifier.

  In addition to the RF line, this power amplifier is also connected with a control line for transmitting a control signal from the transmitter.

  In the PLL described in Patent Document 1, the PLL can be started at high speed by switching the frequency division ratio inside the PLL.

JP 2007-259431 A

  However, in the PLL described in Patent Document 1, the phase error cannot be sufficiently reduced.

  Since the power output from the power amplifier connected to the RFIC is very large, leakage that cannot be ignored occurs not only from the output terminal of the power amplifier but also from the input terminal and the control terminal.

  For this reason, when the power amplifier operates, the leaked electric signal goes around to the VCO through the RF line and the control line.

  If this sneak signal includes a frequency component (harmonic component) that is an integer multiple of the oscillation frequency of the VCO inside the PLL, the VCO is shaken and a phase error occurs.

  The intensity of unnecessary harmonics generated in this way depends on the load impedance of the power amplifier, the harmonic output impedance of the transmitter, and the harmonic input impedance.

  However, in the PLL described in Patent Document 1, only the frequency division ratio inside the PLL is switched. Even if the value of the frequency division ratio is changed, there is no change in the influence of the harmonics on the VCO, so this PLL has a problem that the phase error due to the harmonic components cannot be reduced.

  An object of the present invention is to provide a technique for sufficiently reducing a phase error in a radio frequency integrated circuit.

  In order to achieve the above object, a radio frequency integrated circuit according to the present invention has a voltage controlled oscillator that generates an oscillation frequency signal having an oscillation frequency corresponding to a given voltage, and is obtained by dividing the oscillation frequency signal. A transmitter that generates a radio frequency signal in which a signal wave is placed on a carrier wave, a power amplifier that amplifies the radio frequency signal from the radio frequency circuit, and at least the oscillation frequency that wraps around from the power amplifier to the transmitter. Reducing means for reducing harmonic components of the same frequency.

  According to the present invention, since the harmonic component in the signal that wraps around from the power amplifier to the transmission unit is reduced, the phase error can be sufficiently suppressed.

It is a block diagram which shows one structural example of RFIC of the 1st Embodiment of this invention. It is a block diagram which shows the structure of general RFIC. It is a block diagram which shows one structural example of RFIC of the 2nd Embodiment of this invention. It is a block diagram which shows one structural example of RFIC of the 3rd Embodiment of this invention. It is a block diagram which shows the example of 1 structure of RFIC of the 4th Embodiment of this invention.

(First embodiment)
A first embodiment for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration example of the RFIC 1 of the present embodiment. The RFIC 1 is an integrated circuit that is incorporated in a wireless communication terminal or the like to generate and process a radio frequency signal. Referring to FIG. 1, RFIC 1 includes a transmission unit (RFIC Tx) 10, a power amplifier (PA) 20, and low-pass filters (LPF) 30 and 40. In the figure, the receiving unit of the RFIC 1 is omitted.

  The transmission unit 10 includes a PLL 101, a phase shifter 102, multipliers 103 and 104, an adder 105, an amplifier 106, and a controller 107.

  The PLL 101 includes a reference oscillator 1011, a comparator 1012, a voltage controlled oscillator (VCO) 1013, and a frequency divider 1014.

Reference oscillator 1011 generates an input signal of a predetermined reference frequency f _b. The comparator 1012 compares the frequency of the signal from the reference oscillator 1011 with the frequency of the signal from the frequency divider 1014, and controls the voltage signal for controlling the voltage controlled oscillator 1013 according to the difference between them. Output to the oscillator 1013.

The voltage controlled oscillator 1013 outputs an oscillation frequency signal having an oscillation frequency f ₀ corresponding to the voltage signal from the comparator 1012 to the frequency divider 1014. This oscillation frequency signal is used as a carrier wave in the RFIC 1.

The frequency divider 1014 outputs a signal having a frequency obtained by dividing the frequency f ₀ of the oscillation frequency signal from the voltage controlled oscillator 1013 by a predetermined frequency division number N to the comparator 1012 and the phase adjuster 102.

  The phase adjuster 102 outputs the output signal (carrier wave) from the frequency divider 1014 to the multiplier 103 without changing the phase thereof, and outputs a signal obtained by shifting the phase of the carrier wave by 90 degrees to the multiplier 104.

  Multiplier 103 multiplies the signal (carrier wave) from phase adjuster 102 by the Q signal (signal wave) and Qb signal and outputs the result to adder 105. Multiplier 104 multiplies the signal (carrier wave) from phase adjuster 102 by the I signal (signal wave) and Ib signal and outputs the result to adder 105.

  By mixing by these multipliers, the I signal and the Q signal are up-converted into an RF (radio frequency) signal.

  The adder 105 synthesizes the RF signals from the multipliers 103 and 104 and outputs them to the amplifier 106. The amplifier 106 amplifies the RF signal from the adder 105 and outputs it to the power amplifier 20.

  The controller 107 controls the entire transmission unit 10. Further, the controller 107 outputs a control signal for controlling the power amplifier 20 to the power amplifier 20.

  Here, the transmission unit 10 and the power amplifier 20 are connected by an RF line and a control (Ctrl) line.

  The RF line is a signal line that transmits an RF signal from the amplifier 106 to the power amplifier 20. The control line is a signal line that transmits a control signal from the controller 107 to the power amplifier 20.

  The power amplifier 20 further amplifies the RF signal from the amplifier 106 according to the control signal from the controller 107.

The low pass filter 30 is inserted into the RF line and removes a high frequency component equal to or greater than an integral multiple of the oscillation frequency f ₀ from the signal that passes from the power amplifier 20 to the transmission unit 10. The low-pass filter 40 is inserted into the control line, and removes a high frequency component that is an integral multiple of the oscillation frequency f ₀ or more from the signal that passes from the power amplifier 20 to the transmission unit 10.

  The RF line connects the power amplifier 20 and the PLL 101 via a phase adjuster 102, multipliers 103 and 104, an adder 105, and an amplifier 106. For this reason, when an unnecessary harmonic occurs in the power amplifier, a signal including the harmonic may wrap around the power control oscillator 1013 via the RF line. However, since the low-pass filter 30 removes high-frequency components including harmonic components from the sneak signal, the influence of unnecessary harmonics on the phase adjuster 102 is reduced.

  The control line connects the power amplifier 20 and the PLL 101 via a power line, ground (not shown), and the controller 107. For this reason, when an unnecessary harmonic is generated in the power amplifier, a signal including the harmonic may wrap around the power control oscillator 1013 through the control line. However, since the low-pass filter 40 removes high-frequency components including harmonic components from the sneak signal, the influence of unnecessary harmonics on the phase adjuster 102 is reduced.

  In this way, unnecessary harmonics are attenuated, so that the phase error in the voltage controlled oscillator 1013 is suppressed.

On the other hand, in the RFIC as shown in FIG. 2 in which no low-pass filter is inserted, the harmonic (n * f ₀ ) from the power amplifier 20 is not reduced, and a phase error is likely to occur.

  Note that the low-pass filters 30 and 40 may be tunable filters that can change the frequency band to be removed.

  Further, in the case where the influence of the harmonics that circulate through the control line is not so great as compared to the harmonics that circulate through the RF line, the control line may not be provided with a low-pass filter.

  In the present embodiment, the RFIC 1 corresponds to the radio frequency integrated circuit of the present invention, and the power amplifier (PA) 20 corresponds to the power amplifier of the present invention. The low-pass filter (LPF) 30 corresponds to the low-pass filter for wireless signal lines of the present invention, and the low-pass filter (LPF) 40 corresponds to the low-pass filter for control lines of the present invention. The RF line corresponds to the radio signal line of the present invention, and the control line corresponds to the control signal line of the present invention.

  As described above, according to the present embodiment, the radio signal line low-pass filter inserted into the radio signal line has a high frequency component including a harmonic component from the signal that has circulated to the transmission unit via the radio signal line. Therefore, unnecessary harmonics are attenuated, and the phase error in the voltage controlled oscillator is reduced.

  In addition, the control line low-pass filter inserted in the control line removes high-frequency components including harmonic components from the signal circulated to the transmission unit via the control line, thereby further reducing the phase error.

If the wireless signal line low-pass filter and the control line low-pass filter are tunable filters, the phase error can be tuned to be minimized according to the operating band.
(Second Embodiment)
A second embodiment for carrying out the present invention will be described in detail with reference to FIG. This figure is a block diagram showing an example of the configuration of the RFIC 1a of this embodiment.

  In the present embodiment, it is assumed that the intensity of the harmonic wave that wraps around the power control oscillator 1013 via the control line is negligibly small.

  The RFIC 1a has the same configuration as the RFIC 1 of the first embodiment except that an isolator 50 is inserted in the RF line instead of the low-pass filters 30 and 40.

  The isolator 50 passes an electric signal in the direction from the transmission unit 10 to the power amplifier 20, but prevents the electric signal from flowing in the direction from the power amplifier 20 to the transmission unit 10.

  The insertion of the isolator 50 prevents harmonics from flowing from the power amplifier 20 to the power control oscillator 1013 via the RF line.

  In addition, when the wraparound of the harmonic through the control line cannot be ignored, an isolator can be further inserted into the control line.

  In the present embodiment, the isolator 50 corresponds to a radio signal line isolator of the present invention.

As described above, according to the present embodiment, the radio signal line isolator prevents the signal including the harmonics from the power amplifier from wrapping around, so that the phase error is suppressed.
(Third embodiment)
A third embodiment for carrying out the present invention will be described in detail with reference to FIG. This figure is a block diagram showing a configuration example of the RFIC 1b of the present embodiment.

  The RFIC 1b has the same configuration as that of the RFIC 1 of the first embodiment except that the transmission unit 10 is provided with trap filters (TF) 108 and 109 instead of the low-pass filters 30 and 40.

  The trap filter 108 is inserted into the RF line, and removes harmonics that wrap around the voltage controlled oscillator 1013 from the power amplifier 20 via the RF line. The trap filter 109 is inserted into the control line, and removes harmonics that circulate from the power amplifier 20 to the power control oscillator 1013 via the control line.

  Since the trap filters 108 and 109 attenuate the harmonics, the phase error in the voltage controlled oscillator 1013 is suppressed.

  In this embodiment, a trap filter is inserted. However, any element that can insulate or reduce an electric signal output from the power amplifier 20 to the power control oscillator 1013 via the RF line or the control line can be used as a trap. Elements other than the filter may be inserted.

  The trap filters 108 and 109 may be filters that can change the frequency to be attenuated.

  Although the trap filter is inserted in the RF line and the control line, the trap filter may be inserted in any line other than these lines as long as the harmonic can pass therethrough. . For example, a trap filter may be inserted into any line from the amplifier 106 to the voltage controlled oscillator 1013, or a line (not shown) connecting the ground terminal or the power supply terminal to the PLL 101.

  In the case where the influence of higher harmonic waves that circulate through one of the control line and the RF line is not so great, the line may be configured without a trap filter.

In this embodiment, the trap filter (TF) 108 corresponds to the radio signal line trap filter of the present invention, and the trap filter (TF) 109 corresponds to the control line trap filter of the present invention.
As described above, according to the present embodiment, since the radio signal line trap filter and the control line trap filter remove harmonics from the power amplifier, the phase error is suppressed.

If the attenuation frequency of the trap filter for the radio signal line and the trap filter for the control line is made variable, tuning can be performed so that the decrease in the phase error is minimized according to the operating band.
(Third embodiment)
A third embodiment for carrying out the present invention will be described in detail with reference to FIG. This figure is a block diagram showing a configuration example of the RFIC 1c of the present embodiment.

  The RFIC 1c has the same configuration as the RFIC 1 of the first embodiment, except that the register 110 is provided in the transmission unit 10 instead of the low-pass filters 30 and 40.

  The register 110 stores setting values for the oscillation frequency of the voltage controlled oscillator 1013 and the frequency division number of the frequency divider 1014. The combination of these setting values is changed according to the operation band so that the voltage-controlled oscillator 1013 oscillates at a frequency that avoids high-frequency frequencies while maintaining the carrier frequency at the frequency used for communication.

For example, in harmonics of twice the frequency of the band A in the carrier frequency f _c, harmonics of 4 times the frequency of the band B in the f _c is a phase error degradation due occurs.

In this case, the band A, the register 110, four times the oscillation frequency of f _c is set, with respect to the division ratio before the change, the division number of 1/4 times are set. In zone B, 2 times the oscillation frequency of f _c is set, with respect to the division ratio before the change, the division number of 1/2-fold is set.

  The voltage controlled oscillator 1013 oscillates at a frequency set by the register 110. For example, the voltage controlled oscillator 1013 changes the oscillation frequency by changing the voltage-frequency characteristic. The frequency divider 1014 divides the oscillation frequency by the frequency division number set by the register 110.

  Thus, the influence of the harmonic component can be reduced by changing the combination of the oscillation frequency and the frequency division number according to the band.

  In the present embodiment, the PLL 101 corresponds to the phase synchronization circuit of the present invention, and the frequency divider 1014 corresponds to the frequency divider of the present invention. The register 110 corresponds to the register of the present invention. The frequency set in the register 110 corresponds to the set frequency of the present invention.

  As described above, according to the present embodiment, since the set frequency and the frequency division number that avoid the harmonic frequency are set in the register, it is unnecessary by changing the set value according to the band. It is possible to avoid oscillation of the voltage controlled oscillator at a frequency at which harmonics greatly influence. For this reason, the phase error is reduced.

1, 1a, 1b, 1c RFIC
DESCRIPTION OF SYMBOLS 10 Transmitter 20 Power amplifier 30, 40 Low pass filter 50 Isolator 101 PLL
102 Phase adjuster 103, 104 Multiplier 105 Adder 106 Amplifier 107 Controller 108, 109 Trap filter 110 Register 1011 Reference oscillator 1012 Comparator 1013 Voltage controlled oscillator 1014 Frequency divider

Claims (14)

A voltage-controlled oscillator that generates an oscillation frequency signal having an oscillation frequency corresponding to a given voltage, and a transmitter that generates a radio frequency signal obtained by dividing a signal wave on a carrier wave obtained by dividing the oscillation frequency signal; ,
A power amplifier for amplifying the radio frequency signal from the radio frequency circuit;
Reduction means for reducing harmonic components of at least the same oscillation frequency that wraps around from the power amplifier to the transmission unit;
A radio frequency integrated circuit.   The reduction means is inserted into a radio signal line for transmitting the radio frequency signal, and a high frequency component in a frequency band equal to or greater than an integral multiple of the oscillation frequency from a signal that passes from the power amplifier to the transmitter through the radio signal line. The radio frequency integrated circuit according to claim 1, further comprising a low-pass filter for a radio signal line to be removed.   The radio frequency integrated circuit according to claim 2, wherein the radio signal line low-pass filter is a filter capable of changing a frequency band of a component to be removed.   The reducing means is a control signal that is inserted into a control signal line that transmits a control signal for controlling the power amplifier, and that removes the high-frequency component from a signal that passes from the power amplifier to the transmitter through the control signal line. 4. The radio frequency integrated circuit according to claim 2, further comprising a line low pass filter.   The radio frequency integrated circuit according to claim 4, wherein the control signal line low-pass filter is a filter capable of changing a frequency band of a component to be removed.   2. The radio frequency according to claim 1, wherein the reducing unit includes a radio signal line isolator that is inserted into a radio signal line that transmits the radio frequency signal and prevents a signal from wraparound from the power amplifier to the transmission unit. Integrated circuit.   The reduction means further includes a control signal line isolator that is inserted into a control signal line that transmits a control signal for controlling the power amplifier, and prevents a signal from wrapping from the power amplifier to the transmission unit. The radio frequency integrated circuit according to claim 6.   The reduction means includes a radio signal line trap filter that is inserted into a radio signal line that transmits the radio frequency signal and removes the harmonic component from a signal that passes from the power amplifier to the transmitter through the radio signal line. The radio frequency integrated circuit according to claim 1, comprising:   9. The radio frequency integrated circuit according to claim 8, wherein the radio signal line trap filter is a filter capable of changing a frequency band of a component to be removed.   The reduction unit is inserted into a control signal line that transmits a control signal for controlling the power amplifier, and controls to remove the harmonic component from a signal that passes through the control signal line to the power amplifier or the transmission unit. The radio frequency integrated circuit according to claim 8, further comprising a signal line trap filter.   The radio frequency integrated circuit according to claim 10, wherein the control signal line trap filter is a filter capable of changing a frequency band of a component to be removed.   The reduction means controls the characteristics of the voltage controlled oscillator and the frequency division ratio of the oscillation frequency signal, so that the oscillation frequency has a small influence of the harmonic component that circulates from the power amplifier to the transmission unit. The radio frequency integrated circuit according to claim 1, wherein adjustment is performed so that   The radio according to claim 12, wherein the reducing means adjusts the characteristics of the voltage controlled oscillator so that the oscillation frequency is N times the frequency of the carrier wave when the division ratio is 1 / N. Frequency integrated circuit. A register that sets the oscillation frequency and division ratio;
A frequency divider for frequency-dividing the oscillation frequency signal generated by the voltage controlled oscillator with the frequency division ratio set in the register;
Further comprising
The radio frequency integrated circuit according to claim 12 or 13, wherein the voltage controlled oscillator generates the oscillation frequency set in the register.

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