JP2012175632A - Wireless receiving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless receiving device capable of operating AGC properly by suppressing an image signal.SOLUTION: A wireless receiving device has: a quadrature demodulator 2 performing quadrature demodulation to a high-frequency signal to convert the high-frequency signal into base band signals of I/Q components; base band signal amplifiers 20 and 21 amplifying the base band signals of the I/Q components outputted from the quadrature demodulator, respectively; a phase error detector 65 detecting a phase error from the amplified base band signals of the I/Q components; an amplitude error detector 64 detecting an amplitude error from the amplified base band signals of the I/Q components; an upconversion mixer 25' converting the base band signals of the I/Q components outputted from the base band signal amplifiers into a signal having a frequency higher than frequency components of the base band signals, and performing vector correction based on the detected phase error and amplitude error; and automatic gain controllers 22, 23, and 24 controlling an attenuation amount of the base band signal amplifiers based on an output signal level of the upconversion mixer.

Description

  This description relates to a wireless reception apparatus using a direct conversion reception system.

  Conventionally, mobile communication devices such as mobile phones using a CDMA (Code Division Multiple Access) or W-CDMA (Wideband CDMA) system with a wide modulation band (about several MHz) require an image suppression filter with a high Q value. No direct conversion reception technology is used. The direct conversion reception method is a reception method in which high-frequency received signals are directly converted into orthogonal baseband I / Q signals, which are modulated signals, by an orthogonal demodulator. There is.

  In Patent Document 1, as a direct conversion system receiving apparatus using such a CDMA system, a modulated carrier wave signal is power-controlled at a constant period, and a power control period is detected from the received carrier wave signal. Disclosed is a technique that can perform stable reception without performing discontinuous control during continuous reception by performing step control of reception AGC at the switching timing.

JP 2002-261638 A

  However, in a direct conversion type receiver, as described later, an image signal is generated at the output of the upconversion mixer due to an amplitude error and a phase error generated in the quadrature demodulator and the baseband unit. There is a problem in that it is difficult to perform appropriate AGC control because an error occurs in the output of the IQ detector that is a part.

  An object of this invention is to provide the radio | wireless receiver which can operate AGC appropriately by suppressing an image signal.

One embodiment to solve the problem is:
A quadrature demodulator that quadrature-demodulates a high-frequency signal and converts it to a baseband signal of an I / Q component;
A baseband signal amplifying unit for amplifying a baseband signal of an I / Q component output from the quadrature demodulator;
A phase error detector for detecting a phase error from the baseband signal of the amplified I / Q component;
An amplitude error detector for detecting an amplitude error from the amplified baseband signal of the I / Q component;
Up-conversion in which the baseband signal of the I / Q component output from the baseband signal amplification unit is converted to a frequency higher than the frequency component of the baseband signal, and vector correction is performed based on the detected phase error and amplitude error A multiplier,
An automatic gain control unit for controlling an attenuation amount of the baseband signal amplification unit based on an output signal level of the up-conversion multiplier;
It is a radio | wireless receiver characterized by comprising.

  Even if there are quadrature errors and amplitude errors in the quadrature modulator and baseband part, the image signal can be suppressed in the upconversion output by performing amplitude correction and phase correction in the upconversion mixer. Since no error occurs in step A, appropriate AGC can be performed.

The block diagram which shows an example of a structure of the radio | wireless receiver which concerns on one Embodiment of this invention. Explanatory drawing which similarly shows the ideal spectrum of a radio | wireless receiver, and a spectrum when an image signal generate | occur | produces. Explanatory drawing which similarly shows the detection power when the ideal detection power and the image signal generate | occur | produce in the IQ detector of a radio | wireless receiver. The conceptual diagram of the radio | wireless receiving apparatus by which vector correction | amendment is carried out according to an amplitude error and a phase error. Explanatory drawing which similarly shows the operating principle of a radio | wireless receiver. The block diagram which similarly shows the whole block of a radio | wireless receiver. The 1st block diagram of an up conversion mixer with a correction function similarly. Similarly, the 2nd block diagram of the up-conversion mixer with a correction function. The block diagram which similarly shows an amplitude error detection part and a phase error detection part.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram illustrating an example of a configuration of a wireless reception device according to an embodiment of the present invention. The wireless receiver 1 includes an antenna 11, a BPF 12 provided in the subsequent stage, an RF amplifier 13 provided in the subsequent stage, an orthogonal demodulator 2 provided in the subsequent stage, LPFs 18 and 19 provided in the subsequent stage, An automatic gain control unit 3 provided in the subsequent stage, A / D converters 30 and 31 provided in the subsequent stage, and a digital demodulation processing baseband unit 32 provided in the subsequent stage are provided.

The quadrature demodulator 2 is supplied with signals from the 0/90 degree phase shifter 16 and the 0/90 degree phase shifter 16 to which a transmission signal is given from the local oscillator 14, and is given an I phase from the RF amplifier 13. It has a mixer 15 and a mixer 17 to which the Q phase is given.
The automatic gain control unit 3 is provided at a subsequent stage, a variable gain amplifier 20 to which an I phase is given, a variable gain amplifier 21 to which a Q phase is given, an upconversion mixer 25 to which I and Q phases are given. The IQ detector 22, an error amplifier 23 provided in the subsequent stage, and a lag lead filter 24 provided in the subsequent stage are provided. The up-conversion mixer 25 has a 0/90 degree phase shifter 28 to which a signal is supplied to the local transmitter 27, and a mixer 26 and a mixer 29 to which signals are respectively supplied.

  As an example, the wireless reception device 1 is configured to improve the automatic gain control (hereinafter abbreviated as AGC) function high-speed response of the narrowband wireless direct conversion method (hereinafter abbreviated as DC method). It is. In the case of this method, the quadrature error (amplitude error, phase error) generated by the quadrature demodulator 2 and the amplitude error generated by the baseband circuit (LPF, variable gain amplifier) are directly transmitted to the mixers 26 and 29 of the up-conversion mixer. As a result, the desired wave and its image signal are output to the output of the up-conversion mixer 25.

That is, since the image signal is included in the output of the up-conversion mixer, the combined power of the desired wave and the image signal appears in the IQ detector output, an error occurs in the power detection, and the AGC is detected with an incorrect power value. Will be controlled.
As an example, as shown in FIG. 2, a tone signal of “RF frequency + f _m ” is input to the antenna 11 (where f _m is a frequency within the LPF passband), and the frequency of the upconversion mixer is f _lo. The output spectrum of the up-conversion mixer when there is a phase error and amplitude error and an image signal is generated, and the output spectrum when no image signal is generated appear. FIG. 3 shows time waveforms of the IQ detector output when the image signal is generated and the IQ detector output when the image signal is not generated. However, the variable amplifier is not changed in FIGS. As shown in FIG. 3, when the image signal is included, a power value different from that when the image signal is not included is detected.

  As described above, an image signal is generated at the output of the up-conversion mixer due to the amplitude error and the phase error generated in the quadrature demodulator and the baseband unit, and an error occurs in the output of the IQ detector 22 as the power detection unit, It is difficult to control AGC appropriately. Therefore, in order to properly operate the AGC, it is necessary to suppress the image signal and obtain correct detection power.

FIG. 4 is a conceptual diagram of the radio reception device 1 ′ that is vector-corrected according to the amplitude error and the phase error. When the quadrature demodulator, LPF, variable gain amplifier, and automatic gain controller in FIG. 4 are all in an ideal state, the carrier has an angular frequency ω, and I-phase and Q-phase modulated signals are respectively I (t), When a modulated wave having Q (t) is input to the quadrature demodulator and the gain of the variable gain amplifier is Att (t), the output of the variable gain amplifier is:
Phase I: Att (t) · Amp {I (t)}
Q phase: Att (t) · Amp {Q (t)}
Is obtained.

When the up-conversion angular frequency is ω _lo and these signals are input to the up-conversion mixer 25 ′, the output of the up-conversion mixer is Att (t) · Amp {I (t) cos (ω _lo t) −Q (t ) Sin (ω _lo t)}
Can be obtained. This is a signal in which only the gain of the signal input to the quadrature demodulator is changed.

FIG. 5 is an explanatory diagram showing the operating principle of the wireless receiver. The up-conversion mixer 25 ″ includes mixers 33, 35, 36, and 38, an adder 34, and a variable phase shifter 39. A phase error θ appears in the quadrature demodulator, and an ideal gain Amp is an amplitude error. As the output of the variable gain amplifier, when the phase changes to AmpI and AmpQ, respectively,
Phase I: Att (t) · AmpI {I (t)}
Q phase: Att (t) · AmpQ {−I (t) sin (θ) + Q (t) cos (θ)}
Is output. In the up-conversion mixer 25 ″, as shown below, the processes of <Correction 1>, <Correction 2>, and <Correction 3> shown in the drawing are performed.

<Correction 1>
In the up-conversion mixer 25 ″, for the purpose of suppressing the image signal, the Q-phase signal is multiplied by AmpI / AmpQ to remove the relative amplitude deviation between the I-phase and the Q-phase.
as a result,
Phase I: Att (t) · AmpI {I (t)}
Q phase: Att (t) · AmpI {−I (t) sin (θ) + Q (t) cos (θ)}
Is obtained.

<Correction 2>
In order to suppress the image signal of the up-conversion mixer, the phase of the local frequency signal cos (ω _lo t) or −sin (ω _lo t) of the up-conversion mixer is changed using a variable phase shifter, and When it is created, mixed with the baseband signal, and added, Att (t) · AmpI · cos (θ) {I (t) cos (ω _lo t) −Q (t) sin (ω _lo t)}
Is obtained.

This is a signal in which the gain of the signal input to the quadrature demodulator is merely changed, but the amplitude is different from the ideal up-conversion mixer of FIG.
<Correction 3>
In order to obtain the same amplitude value as that of the ideal up-conversion, multiplication by Amp / AmpI · cos (θ) yields the same Att (t) · Amp {I (t) cos (ω _lo t) −Q (t) sin (ω _lo t)}
Can be obtained.

FIG. 6 is a block diagram showing an overall block of the wireless reception apparatus. FIG. 7 is a first block diagram of the up-conversion mixer with correction function. In FIG. 6, an up-conversion mixer 25 ′ with a correction function is provided.
(First embodiment)
FIG. 7 is a first configuration diagram of the up-conversion mixer with a correction function. In FIG. 7, the up-conversion mixer 25 ′ with a correction function includes an oscillator 51, a variable phase shifter 52, a 0/90 degree phase shifter 53, a variable gain amplifier 54, a mixer 55, a mixer 56, an adder 60, and a variable gain amplifier 57. have. In the up-conversion mixer 25 ′ with a correction function, the function of <Correction 1> for removing the relative amplitude deviation between the I phase and the Q phase in FIG. This amplifier is controlled by AmpIQCont to remove the relative amplitude deviation between the I phase and the Q phase.

The function of <Correction 2> to remove the phase deviation is configured by using the variable phase shifter 52 on one side of the output of the 0/90 degree phase shifter 53. This variable phase shifter is changed in phase Δθ by PhsCont and input to the multiplier to remove the phase error.
The function of <Correction 3> for obtaining an ideal up-conversion mixer amplitude value is configured by the variable gain amplifier 57. This amplifier is controlled by AmpCont.
Att (t) · Amp {I (t) cos (ω _lo t) −Q (t) sin (ω _lo t)}
Get.

(Second Embodiment)
FIG. 8 is a second configuration diagram of the up-conversion mixer with a correction function. In FIG. 8, the up-conversion mixer 25 ″ with a correction function includes an oscillator 51, a 0/90 ° phase shifter 53, a variable gain amplifier 54, a mixer 55, a mixer 56, an adder 60, a variable gain amplifier 57, and a variable delay device 58. , A variable delay device 59 is provided.

The phase correction unit of the up-conversion mixer 25 "with a correction function rotates the phase of the local signal cos and sin tone signals. Since it is not affected by the group delay characteristic, a variable delay as shown in FIG. Δθ can be created by providing a phase difference relative to each local signal by providing a unit 59. A variable delay unit 59 on the I side controls Δθ _i by PhsContI, and a variable delay on the Q side. The device 58 controls Δθ _q by PhsContQ.

  In the first embodiment and the second embodiment, AmpIQCont, AmpCont, and PhsCont (PhsContI, PhsContQ) can be controlled in an analog manner, and discrete control is performed when the image signal can be sufficiently suppressed. It is also possible to do this.

(Control value setting method example)
FIG. 9 is a block diagram showing the amplitude error detector and the phase error detector. In FIG. 9, the wireless reception device 1 includes a digital processing unit 32 ′. The digital processing unit 32 ′ includes an FFT 61, an FFT 62, a peak power detection unit 63, an amplitude error detection unit 64, and a phase error detection unit 65. Have.

A tone signal of “RF frequency + f _m ” is input from the antenna 11 (where f _m is a frequency within the LPF pass band), and updating of the variable gain amplifier of the automatic gain control unit 3-5 is stopped to obtain a fixed gain, The gain value is assumed to be known by the digital processing unit. A signal input from the antenna 11 is converted into an ADC digital value through the LPFs 18 and 19 and the automatic gain control unit 3-5. Since a tone signal is input from the antenna 11, the ADC has an I phase: Att · AmpI {cos (2πf _m t)}
Q phase: Att · AmpQ {sin (2πf _m t−θ)}
Signal is input.

The digital value, the I phase, and the Q phase are each subjected to an FFT operation, the peak power value is detected, and the frequency at which the peak power is detected (fm is detected) is detected by the amplitude error detection unit 64, the phase error detection unit Output to 65.
The phase error detector 65 calculates the phase error θ from the I-phase and Q-phase FFT results of the frequency at which the peak power is detected, controls the PhsCont based on the phase error θ, and detects the phase error θ as an amplitude error. Pass to part 64. On the other hand, the amplitude error detection unit 64 obtains amplitude errors AmpI and AmpQ from the I-phase and Q-phase FFT results of the frequencies at which the peak power is detected, and controls AmpIQCont and AmpCont based on the ideal Amp value and phase error θ. I do.

By using these control values to control the up-conversion mixer 25, the image signal can be suppressed from the output of the up-conversion mixer.
In the above setting method, the set value is detected on the assumption that a tone signal is input from the antenna 11. However, when the amplitude error and the phase error can be detected and PhsCont, AmpIQCont, and AmpCont can be calculated, there is a problem. Therefore, it is possible to suppress the image signal output from the upconversion mixer.

For example, while receiving a TDMA (Time Division Multiple Access) digital modulation signal, it is possible to detect an amplitude error and a phase error from a known pattern such as a unique word in a frame and a synchronization control signal, and calculate PhsCont, AmpIQCont, and AmpCont Is possible.
A plurality of the various embodiments described above can be implemented at the same time. With these descriptions, those skilled in the art can realize the present invention, but various modifications of these embodiments can be conceived. It is easy for a person skilled in the art and can be applied to various embodiments without inventive ability. Therefore, the present invention covers a wide range consistent with the disclosed principle and novel features, and is not limited to the above-described embodiments.

  DESCRIPTION OF SYMBOLS 1 ... Wireless receiver, 2 ... Quadrature demodulator, 3 ... Automatic gain control part, 11 ... Antenna, 12 ... BPF, 13 ... RF amplifier, 14 ... Local oscillator, 15 ... Mixer, 16 ... 0/90 degree phase shifter 17 ... Mixer.

Claims (1)

A quadrature demodulator that performs quadrature demodulation of the high-frequency signal and converts it to a baseband signal of an I / Q component;
A baseband signal amplifying unit for amplifying a baseband signal of an I / Q component output from the quadrature demodulator;
A phase error detector for detecting a phase error from the baseband signal of the amplified I / Q component;
An amplitude error detector for detecting an amplitude error from the amplified baseband signal of the I / Q component;
Up-conversion in which the baseband signal of the I / Q component output from the baseband signal amplification unit is converted to a frequency higher than the frequency component of the baseband signal, and vector correction is performed based on the detected phase error and amplitude error A multiplier,
An automatic gain control unit for controlling an attenuation amount of the baseband signal amplification unit based on an output signal level of the up-conversion multiplier;
A wireless receiver characterized by comprising:

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