JP2013143606A - Radio communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to eliminate a harmful effect on a radio transmission signal by a frequency drift due to an output side load fluctuation of a local oscillation unit without increasing cost.SOLUTION: A radio communication device is comprised of: a local oscillation unit 13 whose oscillation frequency fis influenced by a load fluctuation; a local oscillation unit 26 whose oscillation frequency fis higher than that of the local oscillation unit 13; a mixer 23 connected between the output side connected to a load of the local oscillation unit 13 and the output side of the local oscillation unit 26; a mixer 21 for multiplying a differential signal LO3a by difference between both signals of the local oscillation units 13, 26 obtained by the mixer 23, by an IF modulation signal S1; a mixer 14 for multiplying a differential signal L4a which is difference between the differential signal LO3a obtained by the multiplication of the mixer 21 and the IF modulation signal S1 by the signal with the oscillation frequency fof the local oscillation unit 13; and a power amplifier 15 for power amplifying a transmission modulation signal S2 from the mixer 14.

Description

  The present invention relates to a wireless communication apparatus in which a local oscillator is affected by load fluctuation when performing TDD (Time Division Duplex) wireless communication in a PHS (Personal Handy-phone System) or a mobile phone system.

  A configuration example of a wireless communication apparatus that performs conventional TDD wireless communication is shown in FIG. 2 and will be described. A radio communication apparatus 10 shown in FIG. 2 includes a DAC (Digital to Analog Converter) 11 that performs digital / analog conversion (D / A conversion), a BPF (Band-pass filter) 12 that passes only a predetermined frequency signal, A local oscillating unit 13 that includes a PLL (Phase Locked Loop) synthesizer and oscillates a signal having a constant frequency, a mixer 14 that multiplies the two signals, a power amplifier 15 that amplifies the signal power, and a wireless signal And an antenna 16 for performing transmission and reception.

  In such a configuration, the harmonic generated by the D / A conversion is removed by the BPF 12 from the IF (Intermediate Frequency) modulation signal S1 generated by the D / A conversion of the DAC 11, and this is removed to the mixer 14 as the IF modulation signal S1a. Is output. The local oscillation unit 13 oscillates a local frequency signal LO1 locked to a constant carrier frequency by a PLL synthesizer, and the mixer 14 multiplies the local frequency signal LO1 and the IF modulation signal S1a to generate a transmission modulation signal S2. Generated. The transmission modulation signal S2 is amplified to a predetermined transmission power by the power amplifier 15, and then wirelessly transmitted from the antenna 16 after passing through a low-pass filter (not shown).

  In the wireless communication device 10, the power amplifier 15 is turned off at the reception timing in the TDD operation for power saving, and the power is turned on again at the transmission timing. This on / off operation is repeated in a short time to transmit the transmission modulation signal S2 in bursts when the power is turned on. There exists a thing of patent document 1 as this type of prior art.

JP 2009-135615 A

  However, since the TDD wireless communication is performed in the conventional wireless communication apparatus 10 shown in FIG. 2, transmission (TX) and reception (RX) are performed at time t1-t2 as shown in FIG. It repeats alternately like TX between time t2-t3, RX between time t3-t4. As shown in (b), the power (PA power) of the power amplifier 15 is turned on (TX) at time t1-0 immediately before switching to TX, and turned off at time t2-1 immediately after the end of TX. ) Is repeated by repeating the operation of RX. Thereafter, the operation in which the PA power source is turned on at time t3-0 immediately before TX and turned off at time t4-1 immediately after the TX ends is repeated.

  When the PA power source is turned from OFF to ON at times t1-0 and t3-0, the load impedance when the local oscillation unit 13 sees the mixer 14 side which is the load side is shown as LO load impedance in (c). Thus, it changes from Z0 to Z1. However, the relationship is Z0 ≠ Z1. Further, when the PA power source is turned from ON to OFF at times t2-1 and t4-1, the LO load impedance changes from Z1 to Z0.

When this impedance changes from Z0 to Z1 or from Z1 to Z0, the oscillation frequency of the local oscillating unit 13 rapidly changes (drifts) from a constant value indicated by f _LO1 in FIG. This is because the input impedance of the power amplifier 15 changes suddenly at the moment when the power supply of the power amplifier 15 is switched ON or OFF, and the local oscillation unit 13 receives the influence of the load fluctuation via the mixer 14. More specifically, since a PLL synthesizer is used for the local oscillating unit 13, if there is a sudden load change, the frequency lock is temporarily released by the PLL synthesizer, and the frequency until the re-retraction is performed. It drifts.

  When the frequency drift occurs in this way, the carrier phase of the transmission modulation signal S2 fluctuates. Therefore, when a modulation scheme such as PSK, multilevel QAM, or OFDM is employed in the TDD wireless communication of the wireless communication device 10. There arises a problem that the quality of the transmission modulation signal S2 is adversely affected.

  In order to solve this problem, as shown in FIG. 4, an isolator 18 is connected between the local oscillation unit 13 and the mixer 14, in other words, on the load side of the local oscillation unit 13 to suppress the influence of load fluctuation. There is. However, with this configuration, since the isolator 18 is an expensive component, there is a problem that the cost of the wireless communication device 10 increases.

  The present invention has been made to solve the above-described problems, and can eliminate the adverse effect of the frequency drift due to the output side load fluctuation of the local oscillation unit on the wireless transmission signal so as not to increase the cost. An object is to provide an apparatus.

  In order to solve the above-described problems, the present invention provides a first oscillation unit whose oscillation frequency is affected by load fluctuations, a second oscillation unit having an oscillation frequency higher than that of the first oscillation unit, and the first oscillation unit. An active device connected between an output side connected to a load of the oscillation unit and an output side of the second oscillation unit, and obtaining an oscillation frequency difference between at least the first and second oscillation units; A cancel unit that cancels the frequency drift component by a reverse frequency drift component obtained by inverting the frequency drift component when the difference includes a frequency drift component generated by the influence of load fluctuation in the first oscillation unit. It is characterized by providing.

  In the present invention, the cancel unit includes a first mixer that multiplies a first difference signal based on a difference obtained by the active device and a predetermined frequency signal, and the first difference obtained by multiplication of the first mixer. And a second mixer for multiplying a second difference signal, which is a difference between the signal and the predetermined frequency signal, by a signal having an oscillation frequency of the first oscillation unit.

  In the present invention, the active device includes a mixer that multiplies a plurality of signals, or at least an amplifier in addition to the mixer.

  ADVANTAGE OF THE INVENTION According to this invention, the radio | wireless communication apparatus which can eliminate the bad influence which the frequency drift by the output side load fluctuation | variation of a local oscillating part exerts on a radio transmission signal without becoming high-cost can be provided.

It is a block diagram which shows the structure of the radio | wireless communication apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the conventional radio | wireless communication apparatus. 6 is a timing chart for explaining an operation in which a frequency drift occurs in a local oscillation unit of a wireless communication device. It is a block diagram which shows the other structure of the conventional radio | wireless communication apparatus.

Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as the present embodiment) will be described in detail with reference to the accompanying drawings.
(Configuration of the embodiment)
FIG. 1 is a block diagram illustrating a configuration of a wireless communication device 20 according to the present embodiment. The radio communication apparatus 20 according to the present embodiment further connects a mixer 21 between the DAC 11 and the BPF 12 based on the configuration of the conventional radio communication apparatus 10 shown in FIG. 13 and the connecting portion of the mixer 14 are further connected to a BPF 22, a mixer 23, an amplifier 24, and a BPF 25, and a local oscillation unit 26 is further connected to the mixer 23. However, in FIG. 2, the BPF 12 is supposed to remove harmonics generated by the D / A conversion of the DAC 11, but in the present embodiment of FIG. 1, the BPF 12 includes the mixer signal L4 from the mixer 21 as described later. It also includes a function of passing only the difference signal L4a obtained by subtracting the frequency f1 of the IF modulation signal S1 from the frequency f _{LO2-1 of} the difference signal LO3a.

The wireless communication device 20 includes a local oscillation unit 26 that outputs a local frequency signal LO2 having an oscillation frequency f _LO2 higher than the oscillation frequency f _LO1 of the local oscillation unit 13. The local oscillation unit 26 and the mixer 14 are connected to each other. The amplifier 24 and the mixer 23 as active devices (active devices) are connected between the power amplifier 15 via the power amplifier 15. However, the active device may be only the mixer 23.

  The mixer 23 multiplies the local frequency signal LO1a output from the local oscillating unit 13 and then via the BPF 25 and the amplifier 24 by the local frequency signal LO2 output from the local oscillating unit 26, and the mixer obtained by this multiplication The signal LO3 is output.

BPF22 passes only the difference signal LO3a minus the oscillation frequency _{f LO1} from the oscillation frequency _{f LO2} of the mixer signal LO3. The frequency of the difference signal LO3a is assumed to be _fLO2-1 .

  The mixer 21 multiplies the IF modulation signal S1 from the DAC 11 and the difference signal LO3a, and outputs a mixer signal L4 obtained by this multiplication. The frequency of the mixer signal L4 is f2, and the frequency of the IF modulation signal S1 is f1.

BPF12, of the mixer signals L4, passing from the frequency _{f LO2-1} differential signal LO3a only the difference signal L4a obtained by subtracting the frequency f1 of the IF modulated signal S1. Therefore, the frequency f2 of the difference signal L4a is f _{LO2-1 -f1} .

  The mixer 14 multiplies the difference signal L4a and the local frequency signal LO1, and outputs this as a transmission modulation signal S2 as a radio transmission signal. The transmission modulation signal S2 is amplified to a predetermined transmission power by the power amplifier 15, and then wirelessly transmitted from the antenna 16 after passing through a low-pass filter (not shown).

Here, it is assumed that a frequency drift (or a frequency drift component) Δf is generated in the local oscillation unit 13 as described above with reference to FIG. Since this frequency drift Δf is added to the oscillation frequency f _LO1 of the local oscillating unit 13, the frequency of the local frequency signal LO1 is f _LO1 + Δf.

This frequency f _LO1 + Δf passes through the BPF 25 and the amplifier 24, and then is multiplied by the frequency f _LO2 of the local frequency signal LO2 by the mixer 23. Of these, only the difference frequency component f _LO2 − (f _LO1 + Δf) has the BPF 22 It passes through and becomes differential signal LO3a. Therefore, the frequency f _LO2-1 of the difference signal LO3a is f _LO2 − (f _LO1 + Δf) = f _LO2 −f _LO1 −Δf.

This frequency f _LO2-1 = f _LO2 -f _LO1 -Δf is multiplied by the frequency f1 of the IF modulation signal S1 by the mixer 21, and only the difference frequency component (f _LO2 -f _LO1 -Δf) -f1 is included. It passes through the BPF 12 and becomes the differential signal L4a. Accordingly, the frequency f2 of the difference signal L4a _becomes f LO2 _{-f LO1} -Δf-f1.

This frequency f2 = f _LO2 −f _LO1 −Δf−f1 is multiplied by the frequency f _LO1 + Δf of the local frequency signal LO1 in the mixer 14. Of the multiplication results, the frequency component of the sum is (f _LO2 −f _LO1 −Δf−f1) + (f _LO1 + Δf) = f _LO2 −f1, and this frequency f _LO2 −f1 is the frequency of the transmission modulation signal S2. f _RF .

That is, the radio communication device 20 is configured to feed back the frequency drift component Δf generated in the local oscillating unit 13 and eliminate the frequency drift component Δf with the inverse frequency drift component −Δf obtained by inverting the frequency drift component Δf in this feedback. It is. This canceling operation is performed by a cancel unit configured to include the BPF 22, the mixer 21, the BPF 12, and the mixer 14.
(Operation of the embodiment)
Hereinafter, the canceling operation of the frequency drift component Δf in the wireless communication apparatus 20 according to the present embodiment shown in FIG. 1 will be described with reference to specific frequency values shown in FIG. However, it is assumed that the oscillation frequency f _LO1 of the local oscillation unit 13 is 2 GHz, the oscillation frequency f _LO2 of the local oscillation unit 26 is 2.6 GHz, and the frequency f1 of the IF modulation signal S1 from the DAC 11 is 0.1 GHz.

First, at the moment when the power of the power amplifier 15 is switched from OFF to ON, the input impedance of the power amplifier 15 changes suddenly. The local oscillation unit 13 is affected by this load fluctuation and drifts to the oscillation frequency Δf (eg, 0.01 GHz) ) Occurs. Since this frequency drift component Δf = 0.01 GHz is added to the oscillation frequency f _LO1 = 2 GHz of the local oscillating unit 13, the frequency of the local frequency signal LO1 is 2.01 GHz as shown.

After passing through the BPF 25 and the amplifier 24, the local frequency signal LO1 of 2.01 Hz is multiplied by the frequency f _LO2 = 2.6 GHz of the local frequency signal LO2 from the local oscillation unit 26 by the mixer 23. Here, the frequency 2.6 GHz of the local frequency signal LO2 does not drift. This is because the local oscillating unit 26 is connected to the power amplifier 15 via the mixer 23 and the amplifier 24 as active devices, so that even if the power of the power amplifier 15 is switched from OFF to ON as described above, the load This is because the influence of the fluctuation is absorbed by the active device, so that the oscillation frequency does not change.

Of the signals multiplied by the mixer 23, only the difference frequency component 2.6 GHz−2.01 GHz = 0.59 GHz passes through the BPF 22 and becomes the difference signal LO3a. Therefore, the frequency f _LO2-1 of the difference signal LO3a is 0.59 GHz. If there is no frequency drift Δf, 2.6 GHz-2 GHz = 0.6 GHz.

  The frequency 0.59 GHz of the difference signal LO3a is multiplied by the frequency f1 of the IF modulation signal S1 by the mixer 21, and among these, only the difference frequency component 0.59 GHz-0.1 GHz passes through the BPF 12 and the difference signal L4a. Therefore, the frequency f2 of the difference signal L4a is 0.59 GHz−0.1 GHz = 0.49 GHz. If there is no frequency drift Δf, 0.6 GHz−0.1 GHz = 0.5 GHz.

The frequency f2 = 0.49 GHz is multiplied by the frequency f _LO1 = 2.01 GHz of the local frequency signal LO1 in the mixer 14. Among the multiplication results, the sum frequency component f _LO2 −f1 is 2.01 GHz + 0.49 GHz = 2.5 GHz, and this is the frequency component f _RF of the transmission modulation signal S2 output from the mixer 14 = 2.5 GHz. . That is, the frequency drift component Δf = 0.01 GHz generated in the local oscillation unit 13 is canceled by the cancel unit with the inverse frequency drift component −Δf = −0.01 GHz obtained by inverting the frequency drift component Δf.
(Effect of embodiment)
As described above, the wireless communication device 1 according to the present embodiment includes the local oscillation unit 13 as the first oscillation unit whose oscillation frequency f _LO1 is affected by the load fluctuation, and the oscillation frequency f higher than that of the local oscillation unit 13. The local oscillation unit 26 as a second oscillation unit of _LO2 , an output side connected to the load of the local oscillation unit 13, and an output side of the local oscillation unit 26, and at least each local oscillation unit 13, When the mixer 23 as an active device for _obtaining the difference f _LO2-1 of the oscillation frequency of 26 and the frequency drift component Δf generated by the influence of the load fluctuation in the local oscillation unit 13 is included in the difference f _LO2-1 , A reverse frequency drift component −Δf obtained by inverting the frequency drift component Δf, and a cancel unit that cancels the frequency drift component Δf.

Accordingly, since the frequency drift component Δf is canceled, it is possible to output a radio transmission signal having a frequency f _RF = f _LO2 −f1 with no drift.

  Such a wireless communication device 20 does not require a special expensive device for canceling the frequency drift component Δf. Therefore, the adverse effect of the frequency drift due to the output side load fluctuation of the local oscillation unit 13 on the wireless transmission signal is increased. It can be eliminated so as not to cost.

The cancel unit also includes a mixer 21 as a first mixer that multiplies the difference signal LO3a as the first difference signal by the difference obtained by the mixer 23 and the IF modulation signal S1 as the predetermined frequency signal, and the mixer As a second mixer that multiplies the difference signal L4a as the second difference signal, which is the difference between the difference signal LO3a obtained by multiplication of 21 and the IF modulation signal S1, and the signal of the oscillation frequency f _LO1 of the local oscillation unit 13. The mixer 14 is configured.

According to this configuration, when the local oscillation unit 13 is affected by the load fluctuation and the oscillation frequency f _LO1 drifts Δf, the signal (f _LO1 + Δf) in which the frequency drift component Δf is added to the oscillation frequency f _LO1 and The signal of the oscillation frequency f _LO2 of the local oscillating unit 26 is multiplied by the mixer 23, and the difference signal LO3a that is the difference f _LO2 − (f _LO1 + Δf) of both of the multiplication results and the IF modulation signal S1 of the frequency f1 Are multiplied by the mixer 21. The difference signal L4a obtained by this multiplication {f _LO2 − (f _LO1 + Δf)} − f1 = f _LO2 −f _LO1 −Δf−f1 and the oscillation frequency including the drift component from the local oscillation unit 13 ( f _LO1 + Δf) is multiplied by the mixer 14.

Among the multiplication results, the frequency component corresponding to the sum is (f _LO2 −f _LO1 −Δf−f1) + (f _LO1 + Δf) = f _LO2 −f1. That is, the frequency drift component Δf generated in the local oscillation unit 13 is canceled by the inverse frequency drift component −Δf obtained by inverting the frequency drift component Δf. This cancellation does not require any special expensive equipment.

  The above active device includes at least an amplifier 24 in addition to the mixer 23. In this configuration, the local frequency signal LO1 including the frequency drift component Δf is appropriately amplified and multiplied with the other local frequency signal LO2, so that the frequency drift component Δf can be appropriately extracted. Thereby, as described above, the frequency drift component Δf generated in the local oscillating unit 13 can be accurately canceled by the inverse frequency drift component −Δf.

  Note that the wireless communication device 20 of the present embodiment is applicable at least when a load fluctuation occurs in the local oscillator in a PHS or a mobile phone system using TDD. Further, the present invention is also applicable when there are a plurality of local oscillators and load fluctuation occurs when switching them by switching.

  As mentioned above, although preferred embodiment of this invention was explained in full detail, it cannot be overemphasized that the technical range prediction of this invention is not limited to the range prediction as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiments. In addition, it is apparent from the description of the scope of claims that embodiments to which such changes or improvements are added can also be included in the scope of prediction of the present invention.

11: DAC, 12, 22, 25 ... BPF, 13, 26 ... local oscillator, 14, 21, 23 ... mixer, 15 ... power amplifier, 16 ... antenna, 24 ... Amplifier, 20 ... Wireless communication device.

Claims (3)

A first oscillation unit whose oscillation frequency is affected by load fluctuations;
A second oscillation unit having an oscillation frequency higher than that of the first oscillation unit;
An active circuit connected between an output side connected to the load of the first oscillating unit and an output side of the second oscillating unit, and for obtaining a difference between at least the oscillation frequencies of the first and second oscillating units. The device,
A cancel unit that cancels the frequency drift component by a reverse frequency drift component obtained by inverting the frequency drift component when the difference includes a frequency drift component generated by the influence of load fluctuation in the first oscillation unit. A wireless communication apparatus comprising: The cancellation unit is
A first mixer for multiplying a first difference signal by a difference obtained by the active device and a predetermined frequency signal;
A second mixer that multiplies a second difference signal, which is a difference between the first difference signal and the predetermined frequency signal obtained by multiplication of the first mixer, and a signal of the oscillation frequency of the first oscillation unit. The wireless communication apparatus according to claim 1, further comprising: The wireless communication apparatus according to claim 1, wherein the active device includes a mixer that multiplies a plurality of signals, or at least an amplifier in addition to the mixer.

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