JP2013131960A - Calibration control device, calibration signal generation device, orthogonal conversion device and demodulation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calibration control device, a calibration signal generation device, an orthogonal conversion device and a demodulation device which can be flexibly adapted to various input signals and stably maintain suitable performance and characteristics at high levels without significantly changing configurations.SOLUTION: A calibration control device for obtaining a frequency of a calibration signal to be overlapped on or alternative to two signals as a reference of compensation for deviation of both or one of orthogonality and a level of the two signals which are orthogonal to each other, includes frequency setting means for setting the frequency of the calibration signal for a frequency in a band in which a noise level is less than a predetermined value among bands to be occupied bands of the two signals.

Description

  The present invention relates to a calibration control device for obtaining a frequency of a calibration signal which is a reference for compensation of deviation of either or both of the orthogonality and level of two signals orthogonal to each other, and a calibration signal generation for generating the calibration signal. An orthogonal transform device that converts an input signal into two signals orthogonal to each other and compensates for deviations in the degree of orthogonality and / or level, and a demodulator that demodulates these two signals .

In transmission systems and communication systems to which heterodyne detection or homodyne detection is applied, filters that eliminate image interference waves prior to frequency conversion of received waves and simplification of characteristics under various needs and restrictions At the receiving end where the image signal is received, an image rejection mixer that can set a high suppression ratio of the image wave is often used for the frequency conversion.
FIG. 3 is a diagram illustrating a configuration example of a conventional image rejection mixer.

  In the figure, the received wave is applied to the break contact of the switch 31, and the common contact of the switch 31 is connected to the first inputs of the multipliers 32i and 32q. The output of the multiplier 32i is connected to one input of the orthogonality correction unit 35 via a cascaded low-pass filter 33i and an A / D converter 34i. The output of the multiplier 32q is connected to the other input of the orthogonality correction unit 35 via the cascaded low-pass filter 33q and the A / D converter 34q. One output of the orthogonality correction unit 35 is connected to the first input of the adder 38 and the first input of the demodulation control unit 39 via the phase shifter 36 and the variable gain amplifier 37 connected in cascade. The other output of the orthogonality correction unit 35 is connected to the second input of the adder 38 and the second input of the demodulation control unit 39 via the delay unit 40. The output of the adder 38 is connected to the third input of the demodulation control unit 39. The first to third output ports of the demodulation control unit 39 are connected to the variable gain amplifier 37, the orthogonality correction component 35, and the control terminal of the switch 31, respectively. The digital output port of the demodulation control unit 39 is connected to the make contact of the switch 31 via the cascaded D / A converter 41 and the low-pass filter 42. On the other hand, the corresponding output of the phase shifter 43 is connected to the second input of the multipliers 32 i and 32 q, and the output of the local oscillator 44 is connected to the input of the phase shifter 43.

In the image rejection mixer having such a configuration, the local oscillator 44 generates a local oscillation signal having a frequency f _L set in advance to a value suitable for the frequency fr of the received wave. The phase shifter 43 converts the local oscillation signal into local oscillation signals Li and Lq having phases orthogonal to each other, and supplies the signals to the multipliers 32i and 32q, respectively.

  The switch 31 delivers the received wave to the multipliers 32 i and 32 q under the control of the demodulation control unit 39.

  These multipliers 32i and 32q convert the received waves delivered in this way into intermediate frequency signals IFi and IFq by down-converting them based on the local signals Li and Lq, respectively.

  These intermediate frequency signals IFi and IFq are delivered to the orthogonality correction unit 35 via (low-pass filter 33i, A / D converter 34i) and (low-pass filter 33q, A / D converter 34q), respectively. As will be described later, the orthogonality correction unit 35 compensates for the orthogonality of these intermediate frequency signals IFi and IFq to generate intermediate frequency signals IFi ′ and IFq ′.

  The intermediate frequency signal IFi ′ is phase-shifted by (π / 2) radians by the phase shifter 36 and then delivered to the adder 38 and the demodulation control unit 39 via the variable gain amplifier 37. Further, the intermediate frequency signal IFq ′ is given a delay (equal to the sum of propagation delay times of the phase shifter 36 and the variable gain amplifier 37) by the delay device 40, and then to the adder 38 and the demodulation control unit 39. Delivered.

  The demodulation control unit 39 performs reception by performing quadrature demodulation (hereinafter referred to as “demodulation processing”) of the two intermediate frequency signals respectively given from the output of the variable gain amplifier 37 and the output of the delay device 40 in this way. Restore the transmission information contained in the wave.

  Further, the demodulation control unit 39 is determined based on the procedure of communication control (channel control and call setting may be included) to be performed by the communication apparatus provided with the image rejection mixer shown in FIG. The following processing (hereinafter referred to as “calibration processing”) is performed during the period.

(1) Stop the demodulation process.
(2) For calibration to compress the orthogonality and level deviation of the intermediate frequency signals IFi and IFq, a calibration signal to be applied instead of the received wave is generated, and the D / A converter 41 and the low frequency The signal is applied to the make contact of the switch 31 through the pass filter 42.

(3) The calibration signal is supplied to the multipliers 32i and 32q by connecting the common contact of the switch 31 to the make contact instead of the break contact. Such a calibration signal is converted into two signals orthogonal to each other in the same manner as the received wave described above, and further, via the orthogonality correction unit 35, and further to the phase shifter 36 and the variable gain amplifier 37, respectively. The calibration signals Smi and Smq are delivered to the demodulation control unit 39 and the adder 38 via the delay unit 40.

(4) Frequency analysis of the sum of calibration signals Sci and Scq (hereinafter referred to as “sum signal”) obtained by the adder 38 is performed.

(5) Based on automatic control or an adaptive algorithm that minimizes the level of the frequency component of the calibration signal included in the result of the frequency analysis, the orthogonality correction unit 35 and the variable gain amplifier 37 perform these calibrations. A phase shift amount Δφ and a gain deviation Δa to be applied to correct each of the phase difference and the level difference between the signals Sci and Scq are given.

(6) After performing the above-described processes (1) to (5) at a predetermined frequency (cycle) over the above period, these processes are interrupted, and the common contact of the switch 31 is connected to the break contact. Thus, normal demodulation processing is resumed.

  That is, the demodulation processing performed by the demodulation control unit 39 is demodulated from the input of the multiplier 32 i via the low-pass filter 33 i, the A / D converter 34 i, the orthogonality correction unit 35, the phase shifter 36, and the variable gain amplifier 37. The interval leading to the first input of the control unit 39 and the second input of the demodulation control unit 39 from the input of the multiplier 32q via the low-pass filter 33q, the A / D converter 34q, the orthogonality correction unit 35, and the delay unit 40. The deviation of the amount of phase shift and the gain in the section leading to the input is performed while being compressed.

  Therefore, even when the band limitation on the received wave is not always sufficiently performed in the previous stage of the multipliers 32i and 32q, the image suppression ratio is stably maintained at a high value of, for example, 70 dB or more.

In addition, there existed patent document 1 and patent document 2 which are listed below as prior art relevant to this invention.
(1) “a first mixer circuit that multiplies a high-frequency reception signal by a first local oscillation signal and converts the first and second signals contained in the high-frequency reception signal into an intermediate frequency signal; A second mixer circuit that multiplies the first local oscillation signal by a second local oscillation signal having a phase difference of 90 ° with respect to a signal and frequency-converts the first and second signals into an intermediate frequency signal; and An intermediate frequency signal is input from the first and second mixer circuits, and for the first signal included in the intermediate frequency signal, the intermediate frequency signals from the first and second mixer circuits are shifted in phase. For the second signal, the intermediate frequency signal from the first and second mixer circuits is phase-shifted, and the phase-shifted first and second signals are added to cancel the second signal. And an intermediate frequency filter for extracting the first signal, and the first and first filters When the image rejection characteristic is calibrated, an inversion circuit that inverts one of the local oscillation signals is input to the first or second mixer circuit during normal reception operation, and the local oscillation signal that has not been inverted is input to the first or second mixer circuit. Is output from the intermediate frequency filter when calibrating the image rejection characteristic and a switch circuit that is controlled to input the local oscillation signal inverted by the inverting circuit to the corresponding first or second mixer circuit. And a control circuit that adjusts the phase and gain of the local oscillation signal or the intermediate frequency signal according to the signal level of the intermediate frequency signal. Receiving device characterized in that "area is suppressed" ... Patent Document 1

(2) In an image rejection mixer that cancels an image signal that becomes an interference wave when down-converting an RF signal received from a communication partner station and extracts a desired signal that has been down-converted, the RF signal is converted into two RF signals. RF distribution means for distributing the signals RF1 and RF2, local phase shift distribution means for distributing the local signal to two local signals Lo1 and Lo2 having a phase difference of 90 °, the RF signal RF1, and the local signal Lo1 First multiplying means for multiplying the RF signal RF2 and the local signal Lo2, and first for advancing the phase of the multiplication result of the first multiplying means by α °. Phase shifting means, second phase shifting means for delaying the phase of the multiplication result of the second multiplying means by 90 ° -α °, and phase shifting of the first phase shifting means An addition means for adding and combining the result and the phase shift result of the second phase shift means; and subtracting and combining the phase shift result of the second phase shift means from the phase shift result of the first phase shift means And a subtracting means for selecting and outputting the addition result of the adding means when the frequency of the desired signal included in the RF signal is higher than the frequency of the local signal, while the frequency of the desired signal included in the RF signal If the frequency is lower than the frequency of the local signal, the signal switching means for selectively outputting the subtraction result of the subtraction means is provided. However, the image rejection mixer is characterized in that an IF signal from which the image signal is removed is obtained ... Patent Document 2

JP 2009-177392 A Japanese Patent Laid-Open No. 11-355168

By the way, in the conventional image rejection mixer shown in FIG. 3, during the communication in which the received wave is demodulated by the demodulation control unit 39, the above-described phase shift amount and gain deviation are not compressed even if they fluctuate. It was. Furthermore, since the frequencies of the calibration signals Sci and Scq are constant, these deviations are not compressed with sufficient accuracy in a state where disturbances and noises are superimposed on the calibration signals Sci and Scq at a large level. The possibility was high.
Further, such compression of the amount of phase shift and gain deviation is difficult to achieve with sufficient accuracy when the characteristics of each part change according to temperature, power supply voltage, aging, and the like.

  The present invention provides a calibration control device, a calibration signal generation device, an orthogonal transformation device, and a demodulation device capable of flexibly adapting to various input signals and maintaining stable high performance and characteristics stably without changing the configuration. The purpose is to provide.

  According to the first aspect of the present invention, the frequency of the calibration signal superimposed or replaced with the two signals is used as a reference for compensating the deviation of either or both of the orthogonality and the level of the two signals orthogonal to each other. In the calibration control apparatus, the frequency setting means sets the frequency of the calibration signal to a frequency within a band in which the level of distributed noise is less than a predetermined value among bands that can be occupied bands of the two signals. To do.

  That is, the frequency of the calibration signal is constantly set and maintained at a frequency in a band where the noise level is less than a predetermined value.

  According to the second aspect of the present invention, a calibration signal that is superimposed or replaced with the two signals is generated as a reference for compensating for the deviation of either or both of the orthogonality and the level of the two signals orthogonal to each other. In the calibration signal generating apparatus, the frequency setting means sets the frequency of the calibration signal to a frequency within a band in which the level of distributed noise is less than a predetermined value among bands that can be occupied bands of the two signals. To do.

  That is, the frequency of the calibration signal is constantly set and maintained at a frequency in a band where the noise level is less than a predetermined value.

  According to a third aspect of the present invention, in the orthogonal transformation device that converts the input signal into two signals orthogonal to each other and compensates for the deviation of either or both of the orthogonality and level of the two signals, the filtering means Extracts a component in a band instructed from the outside, in any band of either one of the two signals and a composite wave of the two signals.

  Such a component can be extracted from both the high and low bands of noise superimposed on the two signals.

  According to a fourth aspect of the present invention, in the orthogonal transform device according to the third aspect, the superimposing unit superimposes the calibration signal generated based on the component extracted by the filtering unit on the input signal.

  That is, the calibration signal is given in parallel with the input signal, and serves as a reference for compensating for the deviation of either or both of the orthogonality and level of the two signals.

  According to a fifth aspect of the present invention, in the demodulating device for demodulating two signals generated by the orthogonal transformation device according to the fourth aspect, the frequency setting means is a pass band of the filtering means provided in the orthogonal transformation device. And the frequency of the calibration signal is set to a frequency within a band in which the level of distributed noise is not more than a predetermined value in the passband.

  That is, the orthogonality and level of the two signals are flexibly adapted to the noise level and spectrum input together with the input signal and compensated with high accuracy.

  According to the present invention, the orthogonality and level deviation of two signals orthogonal to each other are compensated without being unnecessarily reduced by noise.

  In the present invention, the deviation of either or both of the orthogonality and the level of these two signals is compensated based on a component extracted from a band having a low level of distributed noise.

  Furthermore, according to the present invention, compensation for the orthogonality and level deviation is steadily realized regardless of whether or not an input signal is applied.

  Therefore, in the transmission system and communication system to which the present invention is applied, high transmission quality is ensured and stably maintained regardless of the configuration and characteristics of these systems.

It is a figure which shows one Embodiment of this invention. It is a figure explaining operation | movement of this embodiment. It is a figure which shows the structural example of the conventional image rejection mixer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of the present invention.
In the figure, components having the same functions and configurations as those shown in FIG. 3 are given the same reference numerals, and descriptions thereof are omitted here.

The difference between the present embodiment and the conventional example shown in FIG. 3 is as follows.
(1) An adder 11 is provided in place of the switch 31.
(2) A demodulation control unit 12 is provided instead of the demodulation control unit 39.
(3) The output of the adder 38 is connected to the third input of the demodulation control unit 12 via the variable band filter 13, and the control port of the variable band filter 13 has a corresponding output port of the demodulation control unit 12. Is connected.

FIG. 2 is a diagram for explaining the operation of the present embodiment.
The operation of this embodiment will be described below with reference to FIGS.
The feature of the present invention lies in the following processing procedure performed by the demodulation control unit 12 in conjunction with the variable band filter 13 and the adder 11 in this embodiment.

  In contrast to the conventional example shown in FIG. 3, the demodulation control unit 12 performs demodulation processing in the same manner as the conventional example by linking with each unit, but the other units are connected via the variable band filter 13 and the adder 11. By linking with, different calibration processing is performed in the points described below.

  The demodulation control unit 12 performs the calibration process according to the following procedure in parallel with the communication control and the above-described demodulation process regardless of whether or not it is the above-described period.

(1) The pass band of the variable band filter 13 is swept on the frequency axis (FIG. 2 (1)).
(2) Within the band of the sum signal (sum of calibration signals Sci and Scq) obtained by the adder 38 by an automatic control or adaptive control algorithm based on the power of the signal obtained through the passband, A frequency f satisfying both the following criteria (a) and (b) is obtained.

(a) On the frequency axis, they are as close as possible to the occupied bands of the intermediate frequency signals IFi and IFq (FIG. 2 (2)).
(b) The level of noise (interference waves and interference waves including image interference waves) (FIG. 2 (3)) not corresponding to the intermediate frequency signals IFi and IFq is lower than the predetermined threshold th (FIG. 2 (4)).

  Further, the demodulation control unit 12 generates the calibration signal of the frequency f thus obtained at an appropriate level (for example, it is not excessive compared with the levels of the intermediate frequency signals IFi and IFq), and D / A. The calibration signal is superimposed on the received wave via the converter 41, the low-pass filter 42 and the adder 11.

  The received wave on which the calibration signal is superimposed is applied to each stage after the multipliers 32i and 32q in the same manner as in the conventional example, and the received wave is demodulated by the demodulation control unit 12 as in the conventional example. On the other hand, the calibration signal is separated from the received wave by the variable band filter 13 in parallel, and is then referred to by the demodulation control unit 12 and used for the calibration process.

  In other words, the frequency of the calibration signal is substantially low (or minimal) in the frequency arrangement previously applied to the received wave and the known channel arrangement set under the frequency arrangement. ) Set and maintained in the frequency band.

  Therefore, according to this embodiment, the orthogonality and level deviation of two orthogonal signals generated by orthogonal frequency conversion of the received wave are stable with accuracy regardless of whether or not communication is in progress. Is compressed.

  Furthermore, according to the present embodiment, it is possible to realize a communication system and a communication device that are advantageous in terms of the following list as compared with the conventional example.

(1) Since the process for identifying the above-described period is unnecessary, the process to be performed by the demodulation control unit 12 can be simplified.
(2) The present invention can be easily applied to a communication system or a transmission system in which a once formed communication path or transmission line should be maintained for a long time.
(3) It can flexibly adapt to sudden changes in temperature, power supply voltage, etc., and maintain stable performance.

  In addition, according to the present embodiment, the level of the calibration signal is set to a value that is not excessive compared to the levels of the intermediate frequency signals IFi and IFq, which is caused by the excessive level of the calibration signal. A reduction in calibration accuracy is avoided.

  In the present embodiment, the frequency at which the frequency of the calibration signal is updated may be any value as long as the above-described orthogonality and the accuracy with which the level deviation is to be compressed have desired values.

  In the present embodiment, the calibration signal may be generated only for re-evaluation of the deviation of the orthogonality and the level, and may not be generated constantly.

  Furthermore, in the present embodiment, both the phase shifter 36 and the variable gain amplifier 37 may be distributed and arranged in the subsequent stage of the orthogonality correction unit 35 corresponding to both the intermediate frequency signals IFi ′ and IFq ′. .

  In the present embodiment, the phase shifter 36 and the variable gain amplifier 37 are distributed in the front stage and / or the rear stage of the orthogonality correction unit 35 as long as the input / output characteristics are linear. May be arranged.

  Further, in the present embodiment, the delay devices 40 may be distributed and arranged in the subsequent stage of the orthogonality correction unit 35 corresponding to both the intermediate frequency signals IFi ′ and IFq ′.

  Further, in the present embodiment, the delay device 40 is distributed and arranged in both the preceding stage and the succeeding stage of the orthogonality correction unit 35 if the input / output characteristics are linear, or may be arranged only in the preceding stage. Good.

  Furthermore, in the present embodiment, the orthogonality correction unit 35 is a control system that varies part or all of the phase of the local oscillation signal generated by the local oscillator 44 and the phase shift amount of the phase shifter 43, for example. It may be replaced.

  In the present embodiment, when the period during which the calibration process is to be performed may be the same period as in the conventional example, the adder 11 may be replaced with the switch 31 illustrated in FIG.

  Furthermore, the input of the variable band filter 13 is set such that the frequency f of the calibration signal is set and maintained as the frequency of the band where the decrease in the S / N ratio due to the noise described above is as small as possible. It may be connected to either the output of the variable gain amplifier 37 or the output of the delay device 40.

  Further, in this embodiment, if the reference applied to obtain the frequency f of the calibration signal matches the occupied bandwidth (presence / absence of modulation) of the calibration signal, the above-described reference (a) , (b), and any combination of criteria (1) to (3) listed below may be used.

(1) Of the channels pre-arranged in the band adjacent to the occupied band of the intermediate frequency signals IFi and IFq on the frequency axis, there is a possibility that it becomes an obstacle to the calibration process under the procedures such as the channel control described above. There is no channel
(2) A frequency outside the band where the intermediate frequency signals IFi and IFq can be located on the frequency axis (for example, a plurality of channels arranged adjacent to each other by a predetermined channel separation) (FIG. 2 (5), (6))

(3) A frequency that can be separated from these intermediate frequency signals IFi, IFq, and noise by applying a multiple access method or the like even if they overlap with the intermediate frequency signals IFi, IFq, and noise on the frequency axis.

  Furthermore, the present invention is not limited to the receiving end of a communication system or transmission system, and any one of orthogonal transformation, orthogonal demodulation, and orthogonal frequency transformation is performed, and compression of orthogonality and level deviation in these processes is required. In other words, the present invention can be similarly applied to various electronic devices such as a transmitting end.

In this embodiment, the multipliers 32 i and 32 q generate intermediate frequency signals IFi and IFq by down-converting the received wave based on the local oscillation signal given from the local oscillator 44 via the phase shifter 43. doing.
However, the present invention is not limited to such a configuration. For example, the present invention can be similarly applied when the multipliers 32i and 32q up-convert or shift the received wave to the baseband region. .

  Further, according to the present invention, all or part of the orthogonality correction unit 35, the phase shifter 36, the variable gain amplifier 37, the adder 38, and the delay device 40 are not configured as hardware such as PGA. May be replaced by digital signal processing performed by

  The present invention is also applicable to the compression of the deviation of only one of the above-described orthogonality and level.

  Further, the present invention is not limited to the above-described embodiments, and various configurations can be made within the scope of the present invention, and any improvement may be applied to all or some of the components.

11, 38 Adder 12, 39 Demodulation control unit 13 Variable band filter 31 Switch 32i, 32q Multiplier 33i, 33q, 42 Low pass filter 34i, 34q A / D converter 35 Orthogonality correction unit 36, 43 Phase shifter 37 Variable gain amplifier 40 Delay device 41 D / A converter 44 Local oscillator

Claims (5)

A calibration control device for obtaining a frequency of a calibration signal superimposed or substituted on the two signals as a reference for compensation of deviation of either or both of orthogonality and level of two signals orthogonal to each other,
A frequency setting means for setting the frequency of the calibration signal to a frequency within a band in which a level of distributed noise is less than a predetermined value among bands that can be occupied bands of the two signals is provided. Calibration control device. A calibration signal generating device that generates a calibration signal that is superimposed on or replaced with the two signals as a reference for compensating for the deviation of either or both of the orthogonality and level of two signals orthogonal to each other,
A frequency setting means for setting the frequency of the calibration signal to a frequency within a band in which a level of distributed noise is less than a predetermined value among bands that can be occupied bands of the two signals is provided. Calibration signal generator. An orthogonal transform device that converts an input signal into two signals orthogonal to each other and compensates for a deviation in both or either of the orthogonality and level of the two signals,
An orthogonal transformation device comprising: filtering means for extracting a component of a band designated from the outside of any band of either one of the two signals and a synthesized wave of the two signals . The orthogonal transformation device according to claim 3,
An orthogonal transforming device comprising superimposing means for superimposing a calibration signal generated based on the component extracted by the filtering means on the input signal. A demodulator that demodulates two signals generated by the orthogonal transform device according to claim 4,
A frequency for changing the pass band of the filtering means provided in the orthogonal transform device, and setting the frequency of the calibration signal to a frequency within the band where the level of distributed noise is a predetermined value or less within the pass band. With setting means
A demodulating device.