JPH09186735A - Demodulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a demodulator eliminating an error for controlling a reception level. SOLUTION: The demodulator is provided with a gain control means 5 adjusting a reception signal level, an A/D converter means 3 quantizing a reception signal, and a base band demodulation means 6 demodulating the base band signal by using the quantized reception signal, and also with a measurement means 7 measuring the reception signal level by using a sample series outputted from the A/D converter means 3 and a control variable setting means 8 setting a gain control variable to be fed back to the gain control means based on the measured reception signal level. The level of the quantized reception signal is measured and the gain control variable is decided based on the result, then the measurement range of the level of the reception signal in the case of setting the gain control variable is decided accurately and an error and dispersion in the reception level control are avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a demodulator used for a receiver of a time division multiple access communication system, and more particularly to a demodulator capable of accurately and automatically controlling the reception level even when the line condition is poor. .

[0002]

2. Description of the Related Art In digital mobile communication, when a demodulator demodulates a received signal, the level of the received signal fluctuates every moment depending on the condition of the transmission line. The demodulator quantizes the received signal, processes the digital signal to demodulate the received signal,
There is a limitation on the dynamic range when performing quantization, and it is necessary to control the received signal level within a predetermined range in order to obtain desired reception characteristics.

As shown in FIG. 7, a conventional demodulator which performs demodulation while controlling a received signal level is an automatic gain controller (AGC) 40 for adjusting the received level and an AGC controller 39 for controlling the operation of the AGC. And a high frequency section or an intermediate frequency section 35, which divides the quadrature-modulated received signal into two, one with the frequency of the local oscillator and the other with 90
° A frequency converter 36 for extracting the in-phase component and the quadrature component of the received signal by multiplying the phase-changed frequencies, an A / D converter 37 for quantizing each of the in-phase component and the quadrature component of the received signal, and an A / D A baseband demodulation unit 38 that demodulates a baseband signal based on the output of the converter 37 is provided.

In digital mobile communication, the receiving line is composed of time-division multiplexed slots as shown in FIG.
The demodulator receives the predesignated slot 29 in this frame 28. The reception level of this reception slot changes momentarily due to the effects of fading and shadowing.

AGC control unit 39 composed of an analog circuit
When the envelope of the received signal changes abruptly, A outputs a control signal corresponding to this change to AGC 40 and receives A
The GC 40 controls the reception level of the reception signal so that digit cancellation or overflow in the quantization in the A / D converter 37 does not occur.

The frequency conversion unit 36 multiplies the received signal whose gain has been adjusted by the AGC 40 by the local signal to extract the in-phase component and the quadrature component. The A / D converter 37 samples the in-phase component and the quadrature component at a sampling frequency of about 2 to 16 times the symbol rate, and displays each sample value as, for example, an 8-bit digital signal.

The baseband demodulation section 38 identifies the sample representing the value of the symbol among these samples, judges the sample value, and demodulates the baseband signal.

[0008]

However, in the conventional demodulator, since the reception level is controlled by the analog circuit, the time constant varies and the reception performance deteriorates. Further, when the information is carried by the amplitude, there is a problem that the amplitude information is distorted when the reception level is controlled.

The present invention solves these conventional problems by eliminating the error in the control of the reception level, and the control of the reception level causes distortion in the demodulation of the amplitude-modulated reception signal. It is an object of the present invention to provide a demodulation device capable of avoiding the above.

[0010]

Therefore, in the present invention, the demodulation device has a measuring means for measuring the reception signal level by using the value of the sample value sequence outputted from the A / D converting means, and the measured reception signal. A control amount setting means for setting a gain control amount to be fed back to the AGC based on the signal level is provided.

Therefore, the measurement of the received signal level that is the basis of the gain control amount setting is performed using the quantized received signal, so that the relationship between the measurement timing and the timing when the measurement result is fed back to the AGC is accurate. Is set to, it becomes possible to control the reception level without any error or variation.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises a gain control means for adjusting the received signal level, an A / D conversion means for quantizing the received signal, and a quantized received signal. In a demodulator of a time division multiple access communication system including a baseband demodulation means for demodulating a baseband signal by using the value of a sample value sequence output from the A / D conversion means, the received signal level is measured. The measurement means and the control amount setting means for setting the gain control amount to be fed back to the gain control means based on the measured reception signal level are provided, and the level of the quantized reception signal is measured, Since the gain control amount is determined based on the result, the measurement range of the received signal level when setting the gain control amount is accurately determined, and the error and the bar in the reception level control are determined. Luck is eliminated.

According to a second aspect of the present invention, the measuring means measures the received signal level of the other slot located immediately before the own slot to be received, and the control amount setting means determines based on the measured received signal level. Thus, the gain control amount for adjusting the received signal level of the own slot is set, and the gain control amount is maintained constant in the own slot.

According to a third aspect of the invention, the measuring means is A
The measurement value of the reception signal level is updated every time the sample value is output from the / D conversion means, and the measurement value of the reception signal level is updated at the sampling cycle.

According to a fourth aspect of the invention, the control amount setting means sets the gain control amount at the sampling cycle of the A / D conversion means by using the measured value of the measuring means. Is precisely controlled in the sampling period.

According to a fifth aspect of the present invention, the control amount setting means sets the gain control amount for adjusting the received signal level of the own slot at an arbitrary time interval. Within the reception time of, the gain control amount is sent to the gain control unit at a constant time interval set by the control amount setting unit.

According to a sixth aspect of the present invention, the control amount setting means transmits the set gain control amount to the baseband demodulating means, and the baseband demodulating means corrects the data used for demodulation based on the gain control amount. By doing so, it is possible to eliminate the distortion caused by the adjustment of the received signal level even when the received signal is amplitude-modulated.

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

(First Embodiment) As shown in FIG. 1, the demodulation device of the first embodiment multiplies a high frequency section or an intermediate frequency section 1 having an AGC 5 by a local frequency to receive a received signal. A frequency converter 2 for extracting the in-phase component and the quadrature component, an A / D converter 3 for quantizing each of the in-phase component and the quadrature component, and a baseband unit 4 for demodulating the baseband signal and controlling the AGC 5. The baseband unit 4 includes a baseband demodulation unit 6 that demodulates a baseband signal, and a reception signal level measurement unit 7 that measures a reception signal level using a sample value output from the A / D converter 3. And the gain control amount for the AGC 5 is fed back through the path 9 and the gain control amount is transmitted to the baseband demodulation unit 6.
Is provided.

The slot to be received by the demodulator is input to the frequency conversion section 2 via the high frequency section or the intermediate frequency section 1, and the frequency conversion section 2 multiplies the received signal by the local signal to obtain the in-phase component. And the orthogonal component are extracted. A / D
The converter 3 samples the in-phase component and the quadrature component at a sampling frequency of about 2 to 16 times the symbol rate, and outputs a sample value sequence in which each sample value is displayed as an 8-bit digital signal to the baseband unit 4. .

The received signal level measuring unit 7 of the baseband unit 4 calculates the received signal level from this received sample value sequence. For example, if the sampled value sequence of in-phase components is i ₁ , i ₂ , i
₃ , and the sampled value sequence of orthogonal components is q ₁ , q ₂ , q ₃
, The received signal level is calculated by (1 / n) Σ (i _m ² + q _m ² ) ^1/2 (where Σ is added from m = 1 to n, n is a constant number). Then, the calculation result is output to the AGC control unit 8.

The AGC control unit 8 converts the calculated received signal level into an AGC control amount and feeds it back to the AGC 5, and the AGC 5 controls the received signal level based on this control amount.

The AGC control section 8 also transmits the AGC control amount to the baseband demodulation section 6, and the baseband demodulation section 6
Corrects based on this AGC control amount when demodulating or decoding the baseband signal from the received sample value sequence. For example, when the baseband demodulation unit 6 decodes a signal by soft decision that can reflect the reliability of information on transmission, the magnitude of the AGC control amount represents the poor S / N ratio, The band demodulation unit 6 can perform decoding without error by using this AGC control amount as reference information.

As described above, in this demodulator, the reception level is measured in the baseband section, and the result is AGC.
To the baseband demodulation section. Therefore, there is no error in the reception level control, and it is possible to control the reception signal level that is compatible with amplitude modulation.

(Second Embodiment) As shown in FIG. 2, the demodulator according to the second embodiment has a slot-by-slot reception signal level measuring unit 16 which measures the reception signal level prior to each reception slot. Is equipped with. Other configurations are the same as those of the first embodiment (FIG. 1).

In this demodulator, as shown in FIG. 5, the reception window 32 is opened earlier to receive the own slot 30 to be received.
Not only that, it also receives a part of the other slots 31 in front of it. Then, the reception signal level measuring unit 16 for each slot of the baseband unit 13 outputs from the A / D converter 12,
In addition, the reception signal level is calculated from the reception sample value sequence of the slot 31 and output to the AGC control unit 17.

The AGC control unit 17 converts the calculated received signal level into an AGC control amount and feeds it back to the AGC 14, and the AGC control amount is also supplied to the baseband demodulation unit 15.
Tell also. At this time, the AGC control unit 17 keeps the AGC control amount constant within its own slot 30.

The AGC 14 controls the received signal level of its own slot 30 with a constant gain based on this AGC control amount. Also, the baseband demodulation unit 15 corrects the received signal sample value sequence of its own slot 30 output from the A / D converter 21 with reference to this AGC control amount.

As described above, this demodulator executes the gain adjustment control of the own slot based on the received signal level of the other slot received immediately before the own slot.

(Third Embodiment) As shown in FIG. 3, the demodulator according to the third embodiment has a sample-by-sample received signal level measuring unit 25 for outputting the received signal level measurement result in sample units. I have it. Other configurations are the same as those of the first embodiment (FIG. 1).

In this demodulator, as shown in FIG. 6, the reception window 34 is opened so that the own slot 33 can be received.

The sample-by-sample received signal level measuring section 25 of this demodulator calculates the received signal level using a constant number of sample values output from the A / D converter 21. Then, each time a new sample value is output from the A / D converter 21, that sample value is added to the calculation basis, and one of the old sample values is excluded from the calculation basis, so that the received signal with a fixed number of sample values is received. Continue calculating levels. In this way, each time a sample value is input, the measured value of the received signal level is updated, and it is updated
Output to the control unit 26.

Each time the measured value of the received signal level of each sample is output from the received signal level measuring unit 25 for each sample, the AGC control unit 26 converts the measured value into an AGC control amount and feeds it back to the AGC 23. Notify the baseband demodulation unit 24. Therefore, in this case, the AGC 23 is controlled by the sampling cycle, and the baseband demodulation unit 24 is
Each sample value of the received signal sample value sequence output from the converter 21 is corrected based on the AGC control amount output in the sampling cycle.

As described above, in this demodulator, the received signal level is precisely measured at the sampling period, and A
The GC control and the correction of the demodulation result are finely performed at the sampling cycle.

(Fourth Embodiment) A demodulator according to the fourth embodiment has the same configuration as that of the first embodiment (FIG. 1). The AGC control unit 8 of this demodulator converts the measurement value of the reception signal level output from the reception signal level measurement unit 7 into an AGC control amount at regular time intervals, and
To the baseband demodulation unit 6 as well. Therefore, the control amount of the AGC is switched at fixed time intervals during the reception period of the own slot. The AGC control unit 8 can arbitrarily set this time interval.

The received signal level measuring unit 7 at this time is
The measured value of the received signal level may be output at fixed time intervals set by the GC control unit 8, or
The measurement value of the reception signal level may be output at the sampling cycle, like the reception signal level measuring unit for each sample in the third embodiment. In the latter case,
The AGC control unit 8 converts the value of the measurement value output from the reception signal level measurement unit 7 at constant time intervals into an AGC control amount.

As described above, in this demodulator, the control amount of AGC is switched at an arbitrary interval during the reception period of its own slot, and the reception signal level is adjusted accordingly.

[0038]

As is clear from the above description, the demodulator of the present invention can accurately set the measurement range of the received signal level that determines the control amount of the AGC.
It is possible to suppress variations and errors in the reception level adjustment of.

Further, the reception level control amount can be reflected in the demodulation of the base band, and the distortion caused by the adjustment of the reception level can be corrected even when the signal is amplitude-modulated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a demodulation device according to first and fourth embodiments of the present invention,

FIG. 2 is a configuration diagram of a demodulation device according to a second embodiment of the present invention,

FIG. 3 is a configuration diagram of a demodulation device according to a third embodiment of the present invention,

FIG. 4 is a reception line for explaining the operation of the demodulation device of the present invention,

FIG. 5 is a diagram for explaining reception slots in the demodulation device according to the second embodiment;

FIG. 6 is a diagram for explaining reception slots in the demodulation device according to the third embodiment;

FIG. 7 is a block diagram of a conventional demodulation device.

[Explanation of symbols]

 1, 10, 19, 35 High frequency part or intermediate frequency part 2, 11, 20, 36 Frequency conversion part 3, 12, 21, 37 A / D converter 4, 13, 22, 38 Base band part 5, 14, 23, 40 AGC section 6, 15, 24 Baseband demodulation section 7 Level measurement section 8, 17, 26 AGC control section 9, 18, 27 Gain control amount feedback path 16 Level measurement section per slot 25 Level measurement section per sample 28 Frame 29 slots 30, 33 Own slot 31 Other slots before own slot 32, 34 Receive window

Claims (6)

[Claims] 1. A gain control means for adjusting a reception signal level, an A / D conversion means for quantizing the reception signal, and a baseband demodulation means for demodulating a baseband signal using the quantized reception signal. In a demodulator of a time division multiple access communication system, comprising: measuring means for measuring a received signal level using the value of the sample value sequence outputted from the A / D conversion means; A demodulation device comprising: a control amount setting unit for setting a gain control amount to be fed back to the gain control unit. 2. The measuring means measures the received signal level of another slot located immediately before the own slot to be received, and the control amount setting means, based on the measured received signal level, the own slot. The demodulator according to claim 1, wherein a gain control amount for adjusting the received signal level of is set. 3. The demodulator according to claim 1, wherein the measuring unit updates the measured value of the received signal level each time a sample value is output from the A / D converting unit. 4. The demodulation according to claim 3, wherein the control amount setting unit sets the gain control amount at a sampling cycle of the A / D conversion unit by using a measurement value of the measurement unit. apparatus. 5. The demodulator according to claim 1, wherein the control amount setting means sets a gain control amount for adjusting the received signal level of its own slot at an arbitrary time interval. 6. The control amount setting means transmits the set gain control amount to the baseband demodulation means, and the baseband demodulation means corrects data used for demodulation based on the gain control amount. The demodulator according to any one of claims 1 to 5.