JP2582828Y2 - Level control direct receiver - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct receiver using orthogonal transform, and an object of the present invention is to improve the level control of an orthogonal transform signal performed for various purposes.

[0002]

2. Description of the Related Art Conventionally, as a technique in the field of such a direct receiver, there has been one disclosed in Japanese Patent Application Laid-Open No. 61-273005. In a direct receiver, automatic gain control (AGC), which is usually performed on two orthogonally transformed signals I and Q having phases different from each other by 90 °, that is, the amplitude of the output characteristic of a demodulated signal is kept constant with respect to a change in input. Control is being performed. In the latter stage, DSP
(Analog to Digital Converter) converts an analog signal into a digital signal in order to perform demodulation processing by a (Digital Signal Processor). The S / N due to quantization noise by the A / D converter is set to a predetermined value. In order to achieve the above, a level correction unit that holds an input signal at a predetermined value or more is used in a stage preceding the A / D converter. Further, if there is a difference in level or a phase difference between the two orthogonally transformed signals, distortion occurs when performing the DSP demodulation processing. Therefore, the level difference or phase difference between the two signals is detected, and the difference is fed back. Then, control is performed to remove those differences.

[0003]

However, in the conventional level control direct receiver for controlling the level of the orthogonal transform signal, a plurality of feedback loops for adjusting the signal level exist for the above-mentioned reason. There is a problem that the processing of (1) affects the processing of other feedback. Further, there is a problem that it is desired to simplify a plurality of feedback loops in terms of signal processing.

Accordingly, an object of the present invention is to provide a level control direct receiver that can simplify a plurality of level controls in view of the above problems and problems.

[0005]

According to the present invention, to solve the above-mentioned problem, a demodulated signal is synthesized by combining two orthogonally transformed signals I and Q having mutually different phases by 90 °.
A direct receiver for obtaining the two orthogonal transform signals.
After converting the signal to a digital signal,
And demodulates the two orthogonal transform signals by combining them.
Level converter that converts analog signals to analog signals.
Digital conversion in Troll Direct receiver
Control value to suppress the effect of noise
The orthogonally converted signals I and Q before the digital conversion
A pre-digital conversion level detector for detecting a bell;
Of orthogonal transform signals I and Q before demodulation by digital processing
The digital value is used as a control value to match the levels.
The levels of the orthogonally transformed signals I and Q before demodulation by the processing are detected.
An output level detector before demodulation and a demodulated signal after demodulation.
As a control value for keeping the level constant,
A demodulated level detector for detecting the level of the demodulated signal,
The level detector before digital conversion and the level before demodulation.
The outputs of the detector and the demodulated level detector are combined and controlled.
A control signal synthesizer for outputting a control signal;
The orthogonal transform signal I with a gain corresponding to the control signal from the
And an amplifier for amplifying Q.
Provide bell control direct receiver. Further
The position at which the phase difference between the orthogonal transform signals I and Q is detected
A phase detector, and outputting an output signal of the phase detector to the control signal.
The signal may be output to a signal combiner.

[0006]

According to the level control direct receiver of the present invention, a plurality of orthogonally transformed signals I and Q having phases different from each other by 90 ° are provided with a plurality of signals corresponding to fluctuations in signal levels detected at a plurality of locations. In a level control direct receiver that performs feedback control, feedback control is performed by synthesizing fluctuations of the plurality of signal levels and varying the degree of amplification based on the synthesized signal to control the level of the orthogonally transformed signal. Speed is increased and the configuration is simplified. Furthermore, a phase difference between the two orthogonally transformed signals is combined with the fluctuation of the plurality of signal levels, and the level of the orthogonally transformed signal is controlled by varying the amplification degree based on the combined signal. In addition, the convergence speed of the feedback control is increased, and the configuration is simplified.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a level control of a direct receiver according to an embodiment of the present invention. The level control direct receiver shown in FIG. 1 includes a receiving antenna 1, a high-frequency amplifier 2 for amplifying a high-frequency signal received from the antenna 1, and a quadrature having a phase difference of 90 ° between signals amplified by the high-frequency amplifier 2. Mixers 3 and 4 for converting the converted signals into I and Q to form a baseband signal, a local oscillator 5 for supplying a signal of a predetermined frequency to the mixers 3 and 4, and forming a quadrature converted signal;
A phase shifter 6 for supplying a signal obtained by shifting the phase of the signal of the local oscillator 5 by 90 °, variable amplifiers 7 and 8 connected to the mixers 3 and 4 respectively, and variable amplifiers 7 and 8 Low-pass filters 9 and 10 connected to each other for filtering an audio signal band to be demodulated, level detectors 11 and 12 for detecting the levels of signals filtered by the low-pass filters 9 and 10, A / D converter (Analog to Digital Converter) 13 for converting a signal passed through the level detectors 11 and 12 from analog to digital
, 14, level detectors 15 and 16 for detecting the output signal levels of the A / D converters 13 and 14, demodulating means 17 for demodulating the signals passing through the level detectors 15 and 16, A D / A converter 18 (Digital to Analog) for converting the demodulated signal by the means 17 from digital to analog.
(Analog Conerter), a level detector 19 that detects the level of the signal from the D / A converter 18 and outputs it to a speaker (not shown) at the subsequent stage, and the output signals of the level detectors 11, 15 and 19 are added. An adder 21 controls the amplification of the variable amplifier 7 with the addition signal, and an adder 22 adds the output signals of the level detectors 12, 16 and 19 to control the amplification of the variable amplifier 8. .

FIG. 2 is a diagram showing the configuration of the level detectors 11, 12 and 19 of FIG. As shown in the figure, each of the level detectors 11, 12 and 19 processes an analog signal, so that their configurations are almost the same, that is, each of the low-pass filters 9, 10 and each of the A / Averaging means 11-1, 12-1 and 19- which divide and average the signals to the / D converters 13 and 14 and the speaker, respectively.
1 and the averaged output signals of the averaging means 11-1, 12-1 and 19-1 are input to one of the adders 21 and 2
2, differential amplifiers 11-2, 12-2 and 19-
2 and the other of the inputs of the differential amplifiers 11-2, 12-2 and 19-2 to the reference signal re of the averaged output signal.
Reference signal generating means 11-3, 12-3 and 19-3 for providing f1, ref2 and ref3 are included.

FIG. 3 is a diagram showing the configuration of the level detectors 15 and 16 of FIG. As shown in the figure, since the level detectors 15 and 16 process digital signals, their configurations are almost the same. That is, the signals from the A / D converters 13 and 14D to the demodulation means 17 are respectively branched. Absolute value converting means 15-1 and 16-1 for averaging, and averaging means 15-2 and 16-2 for averaging output signals of the absolute value converting means 15-1 and 16-1; Means 1
Subtractors 15-3 and 16-3 that input the averaged output signals of 5-2 and 16-2 to one and simultaneously input the reference signals ref4 and ref5 to the other, and the subtracters 15-3 and 1
A D / A converter 15- which converts the output signal of 6-3 from digital to analog and outputs it to the adders 21 and 22
4 and 16-4.

Next, the operation of the various level detectors will be described. The level detector 19 constitutes an automatic gain control (AGC), that is, the detected level difference signal is added to adders 21 and 2
The amplifiers are fed back to the variable amplifiers 7 and 8 via 2 to adjust their amplification so that the difference signal becomes zero, and as a result, are used to secure the level of the output signal of the demodulation means 17 to a certain value or more.

Next, the level detectors 11 and 12 are connected to A
It is used to monitor the level of the signal so as not to be affected by quantization noise at the time of signal conversion of the / D converters 13 and 14, and adjust the level as necessary. FIG. 4 shows A in FIG.
FIG. 4 is a diagram illustrating quantization noise of a / D converter. As shown in the figure, the S / N of the input signal is normally maintained at 60 dB. Since the A / D converters 13 and 14 include quantization noise at the time of signal conversion, in order to maintain the above S / N, it is necessary that the S / N for the quantization noise be larger than that. Is done. Therefore, it is assumed that a 12-bit A / D converter of 72 dB is used as the S / N of the quantization noise. This S / N is determined in consideration of economy. However, if the input signal level of the A / D converter is used in the entire area (12 bits), the above S / N can be achieved.
Since / N is doubled to 36 dB and 60 dB cannot be ensured, passing through the A / D converter deteriorates S / N. For this reason, the signal levels are monitored at the input positions of the A / D converters 13 and 14 by the level detectors 11 and 12, and if the signal level becomes lower than a predetermined value, the signal level lower than the predetermined value is detected. The signals from the level detector 19 are added by the devices 21 and 22, and the amplification degree of the variable amplifiers 7 and 8 is controlled by the added signals.

Next, the level detectors 15 and 16 determine the orthogonality with the local oscillator 5 at the time of the orthogonal transformation, the efficiency of the mixers 3 and 4,
If a level difference occurs between the orthogonal transform signals due to a difference in the transmission path, distortion occurs in the demodulation processing by the demodulation means 17 at the subsequent stage. Therefore, this level is monitored and the level of each signal line is adjusted as necessary. Used to adjust. The level detectors 15 and 16 detect the deviation of the level of each signal line from a predetermined value, add the signals to the signals detected by the level detectors 19, 11 and 12 by the adders 21 and 22, and add The amplification degree of the variable amplifiers 7 and 8 is controlled by the addition signal.

Therefore, according to this embodiment, the signal is processed by one feedback for a plurality of level detections, so that the signal is not further fed back by the feedback signal as in the prior art. Be faster. Further, in the prior art, since the feedback signal is collectively returned to the signal line, the initial object of simplifying the circuit configuration can be achieved.

In the above description, the level of the orthogonal transform signal line is detected and feedback is applied. However, the orthogonal transform signal between the orthogonal transform signals depends on the orthogonality by the local oscillator 5, the efficiency of the mixers 3 and 4, and the transmission path. May cause a phase mismatch. Also in this case, since the feedback control is performed by detecting the phase, this feedback may be performed together with the feedback control as described below.

FIG. 5 is a diagram showing a level control structure of a direct receiver according to another embodiment of the present invention.
The phase detector 20 shown in the figure is an example of phase control, that is, a mixer 21 for mixing the output signals of the level detectors 15 and 16 shown in FIG. 1, a filtering 22 connected to the multiplier 21, A multiplier 23 connected to the filtering 22; a filtering means 25 for filtering the signal of the demodulation means 17;
A divider 24 that divides the output of the level detector 3 by using the output of the filtering means 25 as a divisor, and a multiplier 26 that multiplies the output signal of the divider 24 by the output signal of the level detector 15.
An adder 27 for adding the output signal of the multiplier 26 to the output signal of the level detector 16; and an adder 28 for inverting the output signal of the adder 27 and adding the inverted signal to the output signal of the level detector 15. And a D / A converter 29 that converts the digital signal of the adder 28 into an analog signal and outputs the analog signal to the adder 22.

The operation of the phase detector 20 will be described. For the sake of simplicity, it is assumed that only the variation due to the phase difference occurs in the orthogonal transform signal line. The signals E1 and E2 of the signal lines from the level detectors 15 and 16 can be expressed as follows. E1 = 1/2 · Ei · Eo · cos θi (1) E2 = 1/2 · Ei · Eo · sin (θi−Δθo) (2) Here, Ei denotes the amplitude of the received signal, and Eo denotes the local oscillator. 5 indicates the amplitude of the signal, θi indicates the phase shift due to the modulation signal, and Δθo indicates the phase error between the orthogonal transform signal lines. Therefore, the output signal of the multiplier 21 is as follows.

E1 · E2 = 1/8 · Ei ² · Eo ² · {sin (2θi−Δθo) −sinΔθo} (3) The cutoff frequency fc is determined by the phase angle (2θi−Δθ).
When filtering is performed by the filtering unit 22 having a low-pass characteristic which is a frequency sufficiently lower than the frequency corresponding to o), the output is represented by the following equation.

Eer = − ／ · Eia ² · Eo ² · sin Δθo (4) Here, Eia ² represents an average value of Ei ² . When the filtering processing of the demodulated signal by the demodulating means 17 is performed by the filtering means 25 having a sufficiently low cutoff frequency, the following equation is obtained. Ek = １ ／ Eia ² Eo ² (5) If the multiplier coefficient of the multiplier 23 is −2, the output of the divider 24 is Eer / Ek = sinΔθo.
... (6).

Next, the output of the multiplier 26 is as follows. Ed = 1/2 · Ei · Eo · cos θi · sin Δθo (7) Next, the output of the adder 27 is as follows. E2 '= E
2 + Ed = 1/2 · Ei · Eo · sin θi · cosΔθo (8) Here, if Δθo is small, cosΔθo ≒ 1.

Therefore, the output of the adder 28 is as follows. ΔE = E2-E2 ′
(9) Thus, .DELTA.E is fed back to the adder 22 variable amplifier 8 via the D / A converter 29, and the correction of the phase error can be similarly controlled by the common feedback control.

[0021]

As described above, according to the present invention, two orthogonally transformed signals I and Q whose phases are different from each other by 90 ° correspond to the signal level fluctuations detected at a plurality of locations. In the level control direct receiver that performs the feedback control, the fluctuations of the plurality of signal levels are combined, and the level of the orthogonally transformed signal is controlled by varying the amplification based on the combined signal. The speed of feedback control is faster,
The configuration is simplified.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a level control of a direct receiver according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of level detectors 11, 12, and 19 of FIG.

FIG. 3 is a diagram showing a configuration of level detectors 15 and 16 in FIG.

FIG. 4 is a diagram illustrating quantization noise of the A / D converter in FIG. 1;

FIG. 5 is a diagram illustrating a configuration of a level control of a direct receiver according to another embodiment of the present invention.

[Explanation of symbols]

 3, 4 mixer 5 local oscillator 6 phase shifter 7, 8 variable amplifier 9, 10 low-pass filter 11, 12, 15, 16, 19 level detector 13, 14 A / D conversion Unit 17 demodulation means 18 D / A converter 20 phase detector

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-251747 (JP, A) JP-A-3-208433 (JP, A) JP-A-61-273005 (JP, A) 112237 (JP, U) Japanese Utility Model Hei 5-11521 (JP, U) Japanese Utility Model Utility Model 557916 (JP, U) (58) Fields studied (Int. Cl. ⁶ , DB name) H03D 1/00-1 / 28

Claims (2)

(57) [Scope of request for utility model registration] 1. A demodulated signal is synthesized by combining two orthogonally transformed signals I and Q whose phases are different from each other by 90 °.
A direct receiver for obtaining the two orthogonal transform signals.
After converting the signal to a digital signal,
And demodulates the two orthogonal transform signals by combining them.
Level converter that converts analog signals to analog signals.
In the Troll Direct receiver, the effect of quantization noise during digital conversion was reduced.
The orthogonal transform signal before digital conversion is used as a control value for
Level before digital conversion for detecting the levels of I and Q
A detector, and a quadrature transformed signal I before demodulation by the digital processing;
The control value for matching the level of Q
Level of quadrature transformed signals I and Q before demodulation by total processing
And a control for keeping the level of the demodulated signal after demodulation constant.
Detect the level of the demodulated signal as a value
Level detector after demodulation, level detector before digital conversion, and level before demodulation
The outputs of the detector and the demodulated level detector are combined and controlled.
A control signal combiner that outputs a control signal, and a gain according to the control signal from the control signal combiner,
And an amplifier for amplifying the orthogonal transform signals I and Q.
And a level control direct receiver. 2. The method according to claim 1, further comprising :
A phase detector for detecting a phase difference is provided, and an output of the phase detector is provided.
Outputting a signal to the control signal synthesizer.
The level control direct receiver according to claim 1 , wherein