JP2009188757A - Polar modulation transmitter and modulation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polar wireless transmitter and a modulation method which reduce the modulation accuracy degradation. <P>SOLUTION: A polar coordinate converter 110 inputs an in-phase component signal and a quadrature-phase component signal, and converts them to an amplitude component r and a phase component Δθ. If 90<¾Δθ¾≤180, a phase converter 120 outputs (Δθ-180)[deg] as a phase component Δθ1, and generates a digital signal which means 180[deg] shift. If 0≤¾Δθ¾≤90, the phase converter 120 outputs the phase component Δθ as a phase component Δθ1 and generates a digital signal which means 0[deg] shift. A BPSK modulator 150 performs BPSK modulation corresponding to the digital signal. A power amplifier 160 outputs a signal that is a product of a power supply voltage value corresponding to the amplitude component r and a high frequency phase modulation signal outputted from the BPSK modulator 150. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention particularly relates to a polar modulation transmission apparatus and a modulation method for performing frequency modulation using a PLL (Phase Locked Loop).

  Conventionally, a phase modulation device using a PLL is widely used to form a transmission signal by modulating a carrier signal with a baseband modulation signal (that is, upconverting a baseband modulation signal to a radio frequency). In this type of phase modulation apparatus, generally, low cost, low power consumption, good noise characteristics, and high transmission characteristics such as modulation accuracy are required. As a configuration of the phase modulation apparatus using the PLL, there are various configurations such as a configuration in which a modulation signal is input to a frequency divider and a configuration in which a modulation signal is input to a VCO. In addition, as one of the phase modulation methods, a two-point modulation method that performs modulation in two locations of modulation within the PLL band and modulation outside the PLL band has been proposed (see, for example, Patent Document 1 and Patent Document 2).

When the two-point modulation technique as described above is used, even if the PLL bandwidth is set narrower than the modulation bandwidth, it is possible to output a wide-band RF modulation signal extending beyond the PLL band. As a result, it is possible to suppress the deterioration of noise characteristics due to the PLL.
JP 2000-115264 A JP-T-2002-530917 JP 2003-101599 A

  However, in the case of two-point modulation, the amplitude and phase (phase change: instantaneous frequency) of the IQ signal change, and a large phase change (about 180 degrees) occurs when passing through the origin on the IQ plane. This will be described with reference to FIGS. 13 and 14. FIG. 13A shows an example of the transition of the IQ constellation on the IQ plane, and FIG. 13B shows the phase change when the IQ constellation transitions as shown in FIG. 13A.

  From FIG. 13A and FIG. 13B, it can be seen that when the amplitude and phase of the IQ signal change passing through the vicinity of the origin (see FIG. 13A (a)), a large phase change (about 180 degrees) occurs (FIG. 13B ( a)).

  FIG. 14 is an example in which the state of change of the phase component of the IQ signal is calculated by simulation when two-point modulation is performed. As can be seen from FIG. 14, in the case of two-point modulation, the phase changes instantaneously, that is, a sudden frequency fluctuation occurs.

  As described above, when two-point modulation using VCO / PLL is used in polar modulation, when the modulated wave passes near the origin on the IQ coordinate, a sudden phase change occurs, which makes modulation difficult.

  In particular, as the band of the modulated wave becomes wider and the peak factor of the modulated wave increases, a sudden phase change tends to occur. Therefore, polar modulation using two-point modulation is applied to CDMA, multilevel QAM, and OFDM. When applied, the phase component changes abruptly, resulting in degradation of modulation accuracy.

  The present invention has been made in view of this point, and an object thereof is to provide a polar radio transmission apparatus and a modulation method capable of reducing deterioration of modulation accuracy.

  In order to solve such a problem, one aspect of the polar modulation transmission apparatus of the present invention includes a polar coordinate conversion unit that forms an amplitude component r of an input signal and a phase component Δθ of the input signal, and the phase component Δθ is set to a predetermined phase. Phase conversion means for generating a digital signal indicating information relating to the shifted phase, and a frequency modulation means for obtaining a modulated wave by frequency-modulating a carrier wave based on the phase component Δθ1. And a digital phase modulation means for performing digital phase modulation on the modulated wave based on the digital signal, and a power amplifier for forming a vector modulated wave in which the modulated wave after the digital phase modulation is amplitude modulated by the amplitude component r The structure which comprises these is taken.

  In one aspect of the polar modulation transmission apparatus of the present invention, the digital phase modulation means performs N-value multiphase (N-phase) digital modulation, and the phase conversion means indicates that the absolute value of the phase component Δθ1 is π The phase component Δθ is shifted by 2π × i / N [rad] (i = 0,..., (N−1)) so as to be equal to or less than / N [rad].

  In one aspect of the polar modulation transmission apparatus of the present invention, when the phase difference of the phase state of the digital phase modulation means is (2π × i / N + Δp) [rad], the phase conversion means converts the phase component Δθ into (2π × i / N + Δp) [rad] shift is adopted.

  According to one aspect of the modulation method of the present invention, the step of forming the amplitude component r of the input signal and the phase component Δθ of the input signal, the phase component Δθ is shifted by a predetermined phase, and converted into the phase component Δθ1. A step of generating a digital signal indicating information relating to the shifted phase, a step of obtaining a modulated wave by frequency-modulating a carrier wave based on the phase component Δθ1, and a step of digitally converting the modulated wave based on the digital signal. A step of performing phase modulation, and a step of forming a vector-modulated wave in which the modulated wave after digital phase modulation is amplitude-modulated by the amplitude component r.

  According to the present invention, it is possible to reduce deterioration of modulation accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a main configuration of the polar modulation transmission apparatus according to the first embodiment. In FIG. 1, a polar modulation transmission apparatus 100 includes a polar coordinate conversion unit 110, a phase conversion unit 120, a VCO / PLL (Voltage Controlled Oscillator / Phase Locked Loop) circuit 130, a delay adjustment unit 140, a BPSK modulation unit 150, And a power amplifier 160.

  The polar coordinate conversion unit 110 receives the in-phase component signal and the quadrature component signal, and converts them into an amplitude component r and a phase component Δθ. Polar coordinate converter 110 inputs amplitude component r to the power supply voltage of power amplifier 160 and outputs phase component Δθ to phase converter 120.

  The phase conversion unit 120 converts the phase component Δθ into the phase component Δθ1 according to the phase component Δθ, and generates a digital signal (in this embodiment, a BPSK signal) indicating information on the conversion phase. The correspondence of the conversion from the phase component Δθ to the phase component Δθ1 will be described with reference to FIG.

  FIG. 2 shows a correspondence relationship between the phase component Δθ, the converted phase component Δθ1 and the digital signal (BPSK signal) in the phase conversion unit 120.

  As shown in the figure, when 0 [deg] ≦ | Δθ | ≦ 90 [deg], the phase converter 120 outputs Δθ to the VCO / PLL circuit 130 as the phase component Δθ1. When 0 [deg] ≦ | Δθ | ≦ 90 [deg], the phase conversion unit 120 outputs 0 (L) to the delay adjustment unit 140 as a BPSK signal.

  On the other hand, when 90 [deg] <| Δθ | ≦ 180 [deg], the phase converter 120 outputs (Δθ−180) [deg] to the VCO / PLL circuit 130 as the phase component Δθ1. When 90 [deg] <| Δθ | ≦ 180 [deg], the phase conversion unit 120 outputs 1 (H) to the delay adjustment unit 140 as a BPSK signal. In this way, Δθ1 that satisfies | Δθ1 | ≦ 90 [deg] is output from the phase converter 120 to the VCO / PLL circuit 130.

  Returning to FIG. 1, the VCO / PLL circuit 130 performs frequency conversion on the phase component Δθ1 output from the phase converter 120 to generate a PM modulated wave. The VCO / PLL circuit 130 realizes phase modulation by superimposing the phase component Δθ1 on the frequency control terminal of the VCO / PLL circuit 130.

  The delay adjustment unit 140 delays the digital signal in the subsequent BPSK modulation unit 150 so that the digital signal (BPSK signal in the present embodiment) output from the phase conversion unit 120 and the PM modulation wave are synchronized. . By doing so, the delay difference between the path of the amplitude component and the path of the phase component from the phase converter 120 to the BPSK modulator 150 is compensated.

  FIG. 3 shows a configuration example of the delay adjustment unit 140. The delay adjustment unit 140 includes a signal delay unit 141. The signal delay unit 141 delays the digital signal based on delay difference information indicating a difference between the amplitude component path and the phase component path. Since the delay is mainly due to frequency modulation processing in the VCO / PLL circuit 130, the delay amount may be a fixed value, or the delay time varies depending on the bandwidth of the PLL loop filter of the VCO / PLL circuit 130. In such a case, the delay difference information may be changed according to the loop bandwidth. A supplementary explanation will be given with reference to FIG.

  4A shows a phase modulation signal, FIG. 4B shows a PM modulation wave, and an example in which the delay difference between the phase modulation signal and the PM modulation wave is the delay time Td. At this time, the delay adjustment unit 140 delays the digital signal by the delay time Td. 4 (c) and 4 (d) show a digital signal before delay adjustment and a digital signal after delay adjustment. By doing so, the delay difference between the PM modulated wave and the digital signal after delay adjustment can be eliminated and synchronized.

  The BPSK modulation unit 150 performs BPSK modulation on the PM modulated wave according to the BPSK signal, and outputs a high-frequency phase modulation signal after BPSK modulation to the power amplifier 160.

  FIG. 5 shows a configuration example of the BPSK modulation unit 150. The PM modulated wave output from the VCO / PLL circuit 130 is branched into two, one input to the selector 152 and the other output to the inverter (NOT circuit) 151. The inverter 151 generates a 180 phase inverted signal of the PM modulated wave. The selector 152 receives a 0 (L) or 1 (H) BPSK signal, and outputs a PM modulated wave or a 180 phase inverted signal of the PM modulated wave to an LPF (Low Pass Filter) 153 in accordance with the BPSK signal. Is done. The LPF 153 reduces spurious caused by BPSK modulation. Accordingly, the LPF 153 is not necessarily provided as long as spurious is not a problem.

  Returning to FIG. 1, the power amplifier 160 outputs a signal obtained by multiplying the power supply voltage value corresponding to the amplitude component r and the high-frequency phase modulation signal output from the BPSK modulation unit 150.

  Hereinafter, the operation and characteristics of the polar modulation transmission apparatus 100 configured as described above will be described.

  First, the polar coordinate converter 110 converts the in-phase component signal and the quadrature component signal into an amplitude component r and a phase component Δθ.

  The phase conversion unit 120 converts the phase component Δθ into the phase component Δθ1 in accordance with the phase component Δθ, and the VCO / PLL circuit 130 performs frequency conversion on the phase component Δθ1 to generate a PM modulated wave. . Further, from the phase conversion unit 120, 0 (L) / 1 (H) is output to the BPSK modulation unit 150 as a BPSK signal according to Δθ. The correspondence between the conversion from the phase component Δθ to the phase component Δθ1 and the correspondence between Δθ and the BPSK signal are as shown in FIG.

  In the delay adjustment unit 140, the BPSK signal is delayed in the subsequent BPSK modulation unit 150 so that the BPSK signal output from the phase conversion unit 120 and the PM modulation wave are synchronized.

  The BPSK modulation unit 150 performs BPSK modulation on the PM modulated wave in accordance with the BPSK signal, and outputs a high-frequency phase modulation signal after BPSK modulation to the power amplifier 160.

  The power amplifier 160 outputs a signal obtained by multiplying the power supply voltage value corresponding to the amplitude component r and the high-frequency phase modulation signal output from the BPSK modulation unit 150.

  By doing so, the phase conversion unit 120 outputs to the VCO / PLL circuit 130 the phase component Δθ1 that satisfies Δθ1 ≦ 90 [deg].

  Specifically, as shown in FIG. 2, when 0 [deg] ≦ | Δθ | ≦ 90 [deg], the phase component Δθ is output to the VCO / PLL circuit 130 as it is as the phase component Δθ1. At this time, 0 (L) is output to the BPSK modulator 150 as the BPSK signal. Therefore, since the phase is not inverted in the BPSK modulation unit 150, the modulation of the phase component Δθ is performed by the VCO / PLL circuit 130 when 0 [deg] ≦ | Δθ | ≦ 90 [deg].

  On the other hand, in the case of 90 [deg] <| Δθ | ≦ 180 [deg], the phase component Δθ is converted into (180−Δθ) [deg], and (Δθ−180) [deg] is used as the phase component Δθ1 and the VCO. / PLL circuit 130. At this time, 1 (H) is output to the BPSK modulator 150 as the BPSK signal. Therefore, in the case of 90 [deg] <| Δθ | ≦ 180 [deg], the phase component Δθ is modulated by (Δθ−180) [deg] by the VCO / PLL circuit 130 and then the BPSK modulation unit. 150 is performed by phase inversion.

  As described above, the phase conversion unit 120 converts the phase component Δθ1 input to the VCO / PLL circuit 130 so that it is always 90 [deg] or less. In addition, the polar modulation transmission apparatus 100 can maintain the modulation accuracy for wideband modulation without using a VCO having a high response characteristic.

  FIG. 6A shows a change in phase component Δθ by a conventional polar modulation transmission apparatus, and FIG. 6B shows a change in phase component Δθ by a polar modulation transmission apparatus according to the present embodiment. 6A and 6B are examples in which Δθ is normalized by 2π and Δθ = ± 0.5 V (1 Vpp). As can be seen from FIGS. 6A and 6B, the required sensitivity of the VCO can be suppressed to less than half in the polar modulation transmission apparatus according to the present embodiment as compared with the conventional polar modulation transmission apparatus.

  As described above, according to the present embodiment, phase conversion section 120 shifts phase component Δθ by a predetermined phase to convert it to phase component Δθ1, and generates a BPSK signal indicating information on the shifted phase. , The VCO / PLL circuit 130 obtains a phase-modulated wave by frequency-modulating the carrier wave based on the phase component Δθ1, and the BPSK modulator 150 converts the phase-modulated wave into a digital phase-modulated (BPSK) signal according to the BPSK signal. Modulation).

  In the case of BPSK modulation, the phase conversion unit 120 performs binary BPSK digital modulation, and the phase conversion unit 120 sets the phase component Δθ so that the absolute value of the phase component Δθ1 is equal to or less than π / 2 [rad]. Shift by 2π × i / 2 [rad] (i = 0, 1).

  That is, when 90 <| Δθ | ≦ 180, the phase conversion unit 120 sets (Δθ−180) [deg] as the phase component Δθ1 and generates a BPSK signal indicating a 180 [deg] shift, and 0 ≦ | When Δθ | ≦ 90, the phase component Δθ is set as the phase component Δθ1, and a BPSK signal indicating 0 [deg] shift is generated. The BPSK modulation unit 150 performs BPSK modulation according to the BPSK signal.

  In this way, a phase change exceeding 90 [deg] is performed by inverting the phase by the BPSK modulator 150, and the VCO / PLL circuit 130 performs a phase change of 90 [deg] or less. Therefore, the polar modulation transmission apparatus 100 can maintain the modulation accuracy for wideband modulation without using a VCO having high linearity and response characteristics for the VCO / PLL circuit 130.

  In the above description, assuming that the phase of the two-phase state of the BPSK modulator 150 is an ideal 180 degrees, the case where the phase converter 120 performs the conversion as shown in FIG. 2 has been described. However, when the phase of the two-phase state of the BPSK modulator 150 is shifted by Δp from 180 degrees, and the actual phase difference of the two-phase state is (180 + Δp) [deg], as shown in FIG. Conversion may be performed.

  That is, when the phase difference of the phase state of the BPSK modulation unit 150 is (2π / N + Δp) [rad], the phase conversion unit 120 shifts the phase component Δθ by (2π × / N + Δp) [rad].

  FIG. 7 is a diagram illustrating a correspondence relationship between the phase component Δθ, the converted phase component Δθ1, and the BPSK signal in the phase conversion unit 120.

  That is, assuming that the phase difference between the two phase states of the BPSK modulation unit 150 is (180 + Δp) [deg], when 0 [deg] ≦ | Δθ | ≦ 90 [deg], the phase conversion unit 120 defines the phase component Δθ1 as Δθ is output to the VCO / PLL circuit 130. When 90 [deg] <| Δθ | ≦ 180 [deg], (Δθ−180−Δp) [deg] is output to the VCO / PLL circuit 130 as the phase component Δθ1. To do. The BPSK signal is the same as that shown in FIG.

  In this way, the phase conversion unit 120 performs phase conversion from the phase component Δθ to the phase component Δθ1, so that the phase component Δθ is shifted by (2π / N + Δp) [rad]. Therefore, the BPSK modulation unit in the subsequent stage The phase shift Δp at 150 can be compensated for by the previous phase converter 120.

(Embodiment 2)
In this embodiment, a polar modulation transmission apparatus that performs multiphase PSK modulation instead of BPSK modulation will be described. In the following, a case where QPSK modulation is performed as multiphase PSK modulation will be described as an example. Also, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

  The polar modulation transmission apparatus 200 of FIG. 8 includes a phase conversion unit 210 and a QPSK modulation unit 220 instead of the phase conversion unit 120 and the BPSK modulation unit 150, as compared with the polar modulation transmission apparatus 100 of FIG. .

  The phase conversion unit 210 converts the phase component Δθ into the phase component Δθ1 according to the phase component Δθ, and generates a digital signal (QPSK signal in the present embodiment) indicating information on the conversion phase. The correspondence of the conversion from the phase component Δθ to the phase component Δθ1 will be described with reference to FIG.

  FIG. 9 is a diagram illustrating a correspondence relationship between the phase component Δθ, the phase component Δθ1 after conversion, and the QPSK signal in the phase conversion unit 210.

  As shown in the figure, when −45 [deg] ≦ Δθ <45 [deg], the phase conversion unit 210 outputs Δθ to the VCO / PLL circuit 130 as the phase component Δθ1. When −45 [deg] ≦ Δθ <45 [deg], the phase conversion unit 210 outputs “00” indicating 0 [deg] shift to the delay adjustment unit 140 as the QPSK signal.

  When 45 [deg] ≦ Δθ <135 [deg], the phase conversion unit 210 outputs Δθ−90 [deg] to the VCO / PLL circuit 130 as the phase component Δθ1. When 45 [deg] ≦ Δθ <135 [deg], the phase conversion unit 210 outputs “01” indicating 90 [deg] shift to the delay adjustment unit 140 as a QPSK signal.

  When 135 [deg] ≦ Δθ <225 [deg], the phase conversion unit 210 outputs Δθ−180 [deg] to the VCO / PLL circuit 130 as the phase component Δθ1. When 135 [deg] ≦ Δθ <225 [deg], the phase conversion unit 210 outputs “10” indicating 180 [deg] shift to the delay adjustment unit 140 as the QPSK signal.

  When 225 [deg] ≦ Δθ <315 [deg], the phase conversion unit 210 outputs Δθ-270 [deg] to the VCO / PLL circuit 130 as the phase component Δθ1. When 225 [deg] ≦ Δθ <315 [deg], the phase conversion unit 210 outputs “11” indicating a 270 [deg] shift to the delay adjustment unit 140 as a QPSK signal.

  By performing such conversion, Δθ1 that satisfies Δ | θ1 | ≦ 45 [deg] is output from the phase conversion unit 120 to the VCO / PLL circuit 130.

  The QPSK modulation unit 220 performs QPSK modulation on the PM modulated wave according to the QPSK signal, and outputs the high-frequency phase modulation signal after QPSK modulation to the power amplifier 160. FIG. 10 shows a configuration example of the QPSK modulation unit 220 (see Patent Document 3). The QPSK modulation unit 220 in FIG. 10 includes a frequency divider 221, delay units 222-1 to 222-3, a selector 223, and an LPF 224. Note that the configuration of the QPSK modulation unit 220 is not limited to the configuration illustrated in FIG. 10, and may be another configuration.

  Hereinafter, operations and characteristics of the polar modulation transmission apparatus 200 configured as described above will be described.

  First, the polar coordinate converter 110 converts the in-phase component signal and the quadrature component signal into an amplitude component r and a phase component Δθ.

  The phase conversion unit 210 converts the phase component Δθ into the phase component Δθ1 according to the phase component Δθ, and the VCO / PLL circuit 130 performs frequency conversion on the phase component Δθ1 to generate a PM modulated wave. . Further, “00”, “01”, “10”, and “11” are output from the phase conversion unit 210 to the QPSK modulation unit 220 as QPSK signals according to Δθ. FIG. 9 shows the correspondence between the conversion from the phase component Δθ to the phase component Δθ1, and the correspondence between Δθ and the QPSK signal.

  In delay adjustment section 140, in QPSK modulation section 220 at the subsequent stage, the QPSK signal is delayed so that the digital signal (QPSK signal in the present embodiment) output from phase conversion section 210 and the PM modulated wave are synchronized. The

  The QPSK modulation unit 220 applies QPSK modulation to the PM modulated wave in accordance with the QPSK signal, and outputs a high-frequency phase modulation signal after QPSK modulation to the power amplifier 160.

  The power amplifier 160 outputs a signal obtained by multiplying the power supply voltage value corresponding to the amplitude component r and the high-frequency phase modulation signal output from the QPSK modulation unit 220.

  By doing so, the phase conversion unit 210 outputs to the VCO / PLL circuit 130 a phase component Δθ1 that satisfies −45 ≦ Δθ1 ≦ 45 [deg].

  Specifically, as shown in FIG. 9, when −45 ≦ Δθ <45 [deg], the phase component Δθ is output to the VCO / PLL circuit 130 as it is as the phase component Δθ1. At this time, “00” indicating 0 [deg] shift is output to the QPSK modulator 220 as the QPSK signal. Therefore, in the QPSK modulation unit 220, the phase component Δθ is modulated by the VCO / PLL circuit 130 in the case of −45 ≦ Δθ ≦ 45 [deg] without phase change.

  When 45 [deg] ≦ Δθ <135 [deg], the phase component Δθ is converted into (Δθ−90) [deg], and (Δθ−90) [deg] is used as the phase component Δθ1, and the VCO / PLL It is output to the circuit 130. At this time, “01” indicating 90 [deg] shift is output to the QPSK modulator 220 as the QPSK signal. Therefore, when 45 [deg] ≦ Δθ <135 [deg], the phase component Δθ is modulated by the QPSK modulation unit 220 after being phase-modulated by (Δθ−90) [deg] by the VCO / PLL circuit 130. This is done by shifting the phase by 90 degrees.

  When 135 [deg] ≦ Δθ <225 [deg], the phase component Δθ is converted into (Δθ−180) [deg], and (Δθ−180) [deg] is used as the phase component Δθ1 and the VCO / PLL It is output to the circuit 130. At this time, “10” indicating 180 [deg] shift is output to the QPSK modulator 220 as the QPSK signal. Therefore, when 135 [deg] ≦ Δθ <225 [deg], the phase component Δθ is modulated by the QPSK modulator 220 after being phase-modulated by (Δθ−180) [deg] by the VCO / PLL circuit 130. This is done by shifting the phase by 180 degrees.

  In the case of 225 [deg] ≦ Δθ <315 [deg], the phase component Δθ is converted into (Δθ-270) [deg], and (Δθ-270) [deg] is set as the phase component Δθ1, and the VCO / PLL It is output to the circuit 130. At this time, “11” indicating a 270 [deg] shift is output to the QPSK modulator 220 as the QPSK signal. Therefore, when 225 [deg] ≦ Δθ <315 [deg], the phase component Δθ is modulated by the QPSK modulation unit 220 after being phase-modulated by (Δθ-270) [deg] by the VCO / PLL circuit 130. This is done by shifting the phase by 270 degrees.

  As described above, the QPSK modulator 220 converts the phase component Δθ1 input to the VCO / PLL circuit 130 so that it is always within ± 45 [deg]. The polar modulation transmission apparatus 100 can maintain the modulation accuracy with respect to wideband modulation without using a VCO having high performance and response characteristics.

  As described above, according to the present embodiment, the phase conversion unit 210 sets the phase component Δθ to π × i / 2 [rad] so that the absolute value of the phase component Δθ1 is equal to or less than π / 4 [rad]. ] (I = 0, 1, 2, 3) and generates a QPSK signal indicating information on the shifted phase, and the VCO / PLL circuit 130 frequency-modulates the carrier wave based on the phase component Δθ1. The phase modulation wave is acquired, and the QPSK modulation unit 220 performs digital phase modulation (QPSK modulation) on the phase modulation wave in accordance with the QPSK signal.

  By doing so, in the VCO / PLL circuit 130, a phase change of 90 [deg] or less is performed. Therefore, the VCO / PLL circuit 130 does not use a VCO having high linearity and response characteristics. The polar modulation transmission apparatus 200 can maintain the modulation accuracy for wideband modulation.

  In the above description, the case where QPSK modulation is used as digital modulation has been described. However, the present invention is not limited to this, and the present invention can also be applied to the case where 8PSK modulation is used. That is, when N-value multiphase (N-phase) digital modulation is used, the phase conversion unit 210 sets the phase component Δθ to 2π × i so that the absolute value of the phase component Δθ1 is equal to or less than π / N [rad]. / N [rad] (i = 0,..., (N−1)) may be shifted. By doing so, in the VCO / PLL circuit 130, a phase change equal to or less than π / N [rad] is performed. Therefore, a VCO having high linearity and high response characteristics is used for the VCO / PLL circuit 130. The polar modulation transmission apparatus 200 can maintain the modulation accuracy for wideband modulation.

  FIG. 11A shows how the phase component Δθ varies by the polar modulation transmission apparatus 200 according to the present embodiment. FIG. 11B shows how the phase component Δθ fluctuates in a polar modulation transmission apparatus including an 8PSK modulation unit instead of the QPSK modulation unit 220 of the polar modulation transmission apparatus 200. Similar to FIG. 6, both FIG. 11A and FIG. 11B are examples in which Δθ is normalized by 2π and Δθ = ± 0.5 V (1 Vpp). As can be seen from FIGS. 11A and 11B, the polar modulation transmission apparatus according to the present embodiment can suppress the required sensitivity of the VCO to half or less compared to the conventional polar modulation transmission apparatus (see FIG. 6A).

  Further, from comparison of BPSK modulation (see FIG. 6B), QPSK modulation (see FIG. 11A), and 8PSK modulation (see FIG. 11B), the larger the modulation multi-value number, the more the phase component Δθ1 input to the VCO / PLL circuit 130 becomes. The required sensitivity of the VCO can be suppressed as the peak voltage decreases and the modulation multi-level number increases.

  In the above description, the case where the phase difference between the four phase states of the QPSK modulator 220 is assumed to be ideal and the phase converter 210 performs the conversion as shown in FIG. 9 has been described. As in the first embodiment, the phases of the four phase states of the QPSK modulator 220 are shifted by 0 pi (i = 0,..., (N−1)) from 0 degree, 90 degrees, 180 degrees, or 270 degrees. In such a case, the conversion as shown in FIG. 12 may be performed.

  In this way, the phase conversion unit 210 performs phase conversion from the phase component Δθ to the phase component Δθ1, so that the phase component Δθ is (2π × i / N + Δpi) [rad] (i = 0,..., ( N-1)) is shifted, so that the phase shift Δpi in the subsequent QPSK modulator 220 can be compensated for in the previous phase converter 210.

  The present invention is suitable for application to a mobile terminal such as a mobile phone and a wireless communication device such as a base station thereof.

The block diagram which shows the principal part structure of the polar modulation transmission apparatus which concerns on this Embodiment 1. FIG. The figure which shows the example of a conversion of the phase conversion part which concerns on Embodiment 1. The figure which shows the structural example of a delay adjustment part. Diagram for explaining the operation of the delay adjustment unit The figure which shows the structural example of a BPSK modulation part. FIG. 6A is a diagram illustrating how the phase component Δθ varies with a conventional polar modulation transmission apparatus, and FIG. 6B illustrates how the phase component Δθ varies with the polar modulation transmission apparatus according to Embodiment 1. The figure which shows another conversion example of the phase conversion part which concerns on Embodiment 1. FIG. The block diagram which shows the principal part structure of the polar modulation transmission apparatus which concerns on this Embodiment 2. FIG. The figure which shows the example of a conversion of the phase conversion part which concerns on Embodiment 2. The figure which shows the structural example of a QPSK modulation part. FIG. 11A is a diagram showing a phase component Δθ by the polar modulation transmission apparatus according to Embodiment 2 that performs QPSK modulation, and FIG. 11B is a phase component Δθ by the polar modulation transmission apparatus according to Embodiment 2 that performs 8PSK modulation. Figure showing The figure which shows another conversion example of the phase conversion part which concerns on Embodiment 2. FIG. FIG. 13A is a diagram illustrating a transition of a conventional polar modulation IQ signal, and FIG. 13B is a diagram illustrating a phase change of a conventional polar modulation IQ signal. The figure which shows the simulation result of the change of the phase component of the IQ signal of the conventional polar modulation

Explanation of symbols

DESCRIPTION OF SYMBOLS 100,200 Polar modulation transmitter 110 Polar coordinate conversion part 120,210 Phase conversion part 130 VCO / PLL circuit 140 Delay adjustment part 150 BPSK modulation part 160 Power amplifier 220 QPSK modulation part

Claims (4)

Polar coordinate conversion means for forming an amplitude component r of the input signal and a phase component Δθ of the input signal;
A phase conversion means for shifting the phase component Δθ by a predetermined phase to convert the phase component Δθ into a phase component Δθ1, and generating a digital signal indicating information on the shifted phase;
Frequency modulation means for obtaining a modulated wave by frequency modulating a carrier wave based on the phase component Δθ1,
Digital phase modulation means for applying digital phase modulation to the modulated wave according to the digital signal;
A power amplifier that forms a vector-modulated wave in which the modulated wave after digital phase modulation is amplitude-modulated by the amplitude component r;
A polar modulation transmission apparatus comprising: The digital phase modulation means performs N-phase multiphase (N-phase) digital modulation,
The phase conversion means sets the phase component Δθ to 2π × i / N [rad] (i = 0,..., (N−) so that the absolute value of the phase component Δθ1 is equal to or less than π / N [rad]. 1)) Shift
The polar modulation transmission apparatus according to claim 1. When the phase difference of the phase state of the digital phase modulation means is (2π × i / N + Δp) [rad],
The phase conversion means shifts the phase component Δθ by (2π × i / N + Δp) [rad].
The polar modulation transmission apparatus according to claim 2. Forming an amplitude component r of the input signal and a phase component Δθ of the input signal;
Shifting the phase component Δθ by a predetermined phase to convert the phase component Δθ into a phase component Δθ1, and generating a digital signal indicating information on the shifted phase;
Obtaining a modulated wave by frequency-modulating a carrier wave based on the phase component Δθ1;
Applying digital phase modulation to the modulated wave according to the digital signal;
Forming a vector modulated wave in which the modulated wave after digital phase modulation is amplitude modulated by the amplitude component r;
A modulation method.

Images