JPH06291788A - Radio receiver - Google Patents

Abstract

PURPOSE:To correct a deviation from a frequency of a local oscillation signal by applying an averaging to reception data, detecting an angle between the received data so as to correct the frequency of the local oscillation signal thereby avoiding accumulation of errors due to approximation. CONSTITUTION:An error detecting circuit 24 inputs I axis data and Q axis data sequentially outputted from an A/D converter circuit 7 to output both reception data Xi being a demodulation result letting a reference phase be a criterion and reception data Yi being the result of demodulation whose phase is shifted by 90 deg. from a reference signal. The error detection circuit 24 accumulates the reception data Xi, Yi to operate accumulated data Ai, Bi. The reception data Xi, Yi are inputted to a line buffer, from which reception data Xi+1, Yi+1 delayed by the number of prescribed stage are generated. A change between accumulated data Ai+1, Bi+1 resulting from accumulating the delayed data Xi+1, Yi+1 and the accumulated data Ai, Bi is detected to detect a frequency deviation in a local oscillation signal.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Industrial Application Conventional Technology (FIGS. 4 to 7) Problem to be Solved by the Invention (FIGS. 4 to 7) Means for Solving the Problem (FIGS. 1 and 2) Action (FIGS. 1 and 2) Example (1) Overall configuration of example (FIG. 1) (2) Correction of frequency of local oscillation signal (FIGS. 2 and 3) (3) Effect of example (4) Effect of other example of invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio receiver, and can be applied to, for example, a digital cellular which encodes and transmits a voice signal.

[0003]

2. Description of the Related Art Conventionally, in a digital cellular phone, which is one of radio telephones, by encoding and transmitting a voice signal, a time-division multiplexing method is applied so that one channel is simultaneously used by a plurality of terminal devices. It is designed to be used.

That is, when the terminal device of this type is turned on, the preset 124 channels are sequentially scanned to detect the channel having the highest electric field strength.
As a result, the terminal device is assigned a BCCH (broadcast control channel) assigned to the area to which the terminal device belongs.
) Is detected and this BCCH is received.

The BCCH is adapted to form a time slot and transmit various kinds of information, whereby the digital cellular receives information of the base station which receives the BCCH at each terminal device and sends out the BCCH, which is adjacent to the information. The information of the base station, the calling information of the terminal device, and the like are transmitted. For this reason, the terminal device outputs the FCCH (frequency co
rrection channel), and this FCCH
Is used to roughly detect the timing at which necessary information is transmitted, and the FCCH is used as a reference to correct the frequency of the local oscillation signal.

Here, FCCH has a value of "1" when demodulated.
Is a synchronizing signal assigned with a bit pattern so that the data is continuous for a predetermined number of bits. In digital cellular, this data is GMSK-modulated and transmitted. As a result, as shown in FIG. 4, when the FCCH is received at the correct reference phase that is phase-synchronized with the base station, the terminal device can demodulate the reception data represented on the IQ plane and distributed on the I axis and the Q axis, respectively. it can. By the way, the actual demodulation result is sequentially circulated on the I-axis and the Q-axis in a 90-degree phase.

On the other hand, as shown in FIG. 5, when the FCCH is received with the reference phase frequency deviated, the received data deviates slightly from the I axis and the Q axis depending on the frequency deviation. This state occurs not only when the frequency of the reference phase is displaced, but also when the frequency of the local oscillation signal is displaced. As a result, this type of terminal device detects the angle θ of the phase shift of the received data represented on the IQ plane, and corrects the frequency of the local oscillation signal based on the detection result.

That is, the terminal device detects the position of the received data on the IQ plane by detecting the demodulation result based on the reference phase and the demodulation result that is 90 ° out of phase with respect to this demodulation result, and the positions are continuous. The angle θ is detected between the received data.

If the frequency of the local oscillation signal is shifted by 1 [ppm] with respect to the base station, the following equation is obtained.

[Equation 1] It is understood that the angle θ becomes 5 degrees by applying the relational expression of Here, fcarrier represents a carrier frequency, which is 900 [MHz] in digital cellular, and Δf
Represents the difference in clock frequency between the terminal device and the base station.
Further, .DELTA.BIT represents the bit interval, which is 4 bits in the digital cellular, and .DELTA.t represents the bit deration (1 / fb), which is approximately 1 / 270,000 in the digital cellular. As a result, it can be seen that the angle θ can be detected to detect the frequency shift, and the frequency of the local oscillation signal can be corrected.

However, noise is mixed in the actual received data, so that each received data is irregularly distributed in a circular area, as shown in FIG. Therefore, this type of terminal device averages the angle detection results by accumulating the angle detection results, thereby eliminating the influence of noise.

For this reason, the terminal device first uses the following equation

[Equation 2] Is executed, and as a result, as shown in FIG.
In order to detect the phase shift angle with reference to the positive side of the axis, the received data whose phase is sequentially changed by 90 degrees is phase-matched. Here, Xj represents received data represented by complex data,% represents modulo calculation, and j represents imaginary unit.

As a result, the terminal device phase-matches the received data so that the received data is distributed in the vicinity of the I-axis,
Two consecutive data (Ai, Bi) and (Ai + 1, B)
i + 1) between

[Equation 3]

[Equation 4]

[Equation 5] Of the two data (Ai, Bi) and (Ai + 1, Bi + 1) which are continuous, the angle .theta.
detect i. Here, the arithmetic processing of sin ^-1 is executed by using the Maclaurin expansion or the trigonometric function table.

Further, the terminal device averages the sequentially detected angles θi, thereby applying the relationship described above in relation to the equation (1) to detect the deviation of the frequency of the local oscillation signal, and the frequency of the local oscillation signal. It is designed to correct.

[0014]

By the way, when the angle θi is sequentially detected and accumulated between two continuous data (Ai, Bi) and (Ai + 1, Bi + 1), two data (A
There is a drawback in that the approximation error is unavoidable in the arithmetic processing of sin ^-1 when detecting the angle θi between (i, Bi) and (Ai + 1, Bi + 1), and this error is accumulated. Therefore, the conventional frequency correction method has a feature that the frequency shift cannot be detected accurately, and there is a problem that the frequency of the local oscillation signal cannot be corrected accurately.

As a method for solving this problem, a method of correcting this kind of frequency shift by, for example, generating a local oscillation circuit by a PLL circuit formed of an analog circuit is conceivable, but the overall configuration becomes complicated and complicated. In addition, there is a problem that the reliability is deteriorated due to increase in noise and failure to completely prevent secular change of elements forming a circuit.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a radio receiving apparatus capable of easily and reliably detecting a frequency deviation of a local oscillation signal.

[0017]

In order to solve such a problem, according to the present invention, a local area is provided in a radio receiving apparatus 1 which receives a transmission signal with reference to a synchronization signal FCCH inserted in the transmission signal at a predetermined timing. A frequency conversion circuit 4 that frequency-converts and outputs the transmission signal based on the oscillation signal, and a first demodulation that demodulates the output signal of the frequency conversion circuit 4 at a predetermined reference phase and outputs a first demodulation result Xi. Means 24 and second demodulation means 24 for outputting a second demodulation result Yi having a phase difference of 90 degrees with respect to the first demodulation result Xi,
A first averaging means 24 for accumulating a predetermined number of first and second demodulation results Xi and Yi respectively and outputting first accumulated data Ai and Bi of the first and second demodulation results Xi and Yi. 25, 26, 27 and a predetermined number of first and second demodulation results Xi and Yi are respectively accumulated, and second accumulated data Ai + of the first and second demodulation results Xi and Yi are accumulated.
Second averaging means 24, 25, which output 1 and Bi + 1
26, 27, 28, changes in the first accumulated data Ai and Bi and second accumulated data Ai + 1 and Bi + 1 are detected to detect the frequency shift of the local oscillation signal, and the frequency shift detection result An error detection unit 15 that outputs θ is provided, and the frequency of the local oscillation signal is corrected based on the frequency shift detection result θ.

Further, in the second invention, the synchronization signal FC
CH is formed by phase-modulating predetermined reference data, and the first averaging means 24, 25, 26, 27 phase-correct the first and second demodulation results Xi and Yi by the amount of phase modulation. And then generate the first cumulative data Ai and Bi,
The second averaging means 24, 25, 26, 27, 28 have the first and second demodulation results Xi and Y corresponding to the amount of phase modulation.
After phase correction of i, second accumulated data Ai + 1 and Bi +
Generates 1.

Further, in the third invention, the first averaging means 24, 25, 26 and 27 have shift register circuits 25 connected in series by a predetermined number of stages, and the first and second demodulation results Xi and In synchronization with the cycle of Yi, the shift register circuit 25 sequentially transfers the first and second demodulation results Xi and Yi, and cumulatively adds the first and second demodulation results Xi and Yi input to the shift register circuit 25. At the same time, the output data Xi + 1 and Yi + 1 of the shift register circuit 25 are subtracted from the cumulative addition result to generate the first cumulative data Ai and Bi, and the second averaging means 24, 25, 26, Two
Reference numerals 7 and 28 hold the first cumulative data Ai and Bi for the period of the first and second demodulation results Xi and Yi to generate the second cumulative data Ai + 1 and Bi + 1.

[0020]

The first accumulated data Ai and Bi of the first and second demodulation results Xi and Yi and the first and second demodulation results X
obtain the second cumulative data Ai + 1 and Bi + 1 of i and Yi,
After that, the first and second accumulated data Ai, Bi and Ai + 1
, Bi + 1 changes to detect the frequency deviation of the local oscillation signal, the influence of noise can be reduced and the frequency deviation can be detected with high accuracy.

At this time, the first and second demodulation results Xi and Yi are phase-corrected by the phase-modulated amount to generate the first accumulated data Ai and Bi, and the phase-modulated similarly. If the second demodulation results Xi and Yi are phase-corrected to generate the second accumulated data Ai + 1 and Bi + 1, the frequency deviation can be detected with reference to the phase-modulated synchronization signal FCCH.

Further, the first and second demodulation results Xi and Y are generated by the shift register circuit 25 connected in series for a predetermined number of stages.
The first and second demodulation results Xi and Yi which sequentially transfer i and input to the shift register circuit 25 and the first and second demodulation results Xi which transfer and output the shift register circuit 25.
And Yi generate the first cumulative data Ai and Bi,
If the first accumulated data Ai and Bi are held only for the period of the first and second demodulation results Xi and Yi to generate the second accumulated data Ai + 1 and Bi + 1, the first and the second accumulated data can be easily obtained. Two
Cumulative data Ai, Bi and Ai + 1, Bi + 1 can be generated.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

(1) Overall Configuration of the Embodiment In FIG. 1, reference numeral 1 denotes a digital cellular terminal device as a whole, in which a transmission signal transmitted from a base station is received by an antenna 2 and a reception signal obtained as a result is received by the antenna. Output to the mixer 4 via the duplexer 3. The mixer 4 frequency-converts the received signal using the local oscillation signal output from the oscillation unit 5, and then outputs the received signal via the filter 6, whereby the terminal device 1 switches the frequency of the local oscillation signal to a desired value. It is designed so that channels can be selectively received.

Analog digital conversion circuit (A / D) 7
Receives the output signal of the filter 6 through the amplifier circuit 8, converts it into a digital value with reference to a predetermined reference signal, and outputs the digital value, whereby the terminal device 1 is synchronized with the reference phase of the received signal. The I data I which is the demodulation result can be demodulated. Further, the analog digital conversion circuit 7 inputs the output signal of the amplification circuit 8 through the phase shifter 9 and converts this input signal into a digital value, whereby the terminal device 1 is 90 degrees in phase with the I data. Q data Q having different demodulation results can be demodulated, and thus I data and Q data which are GMSK modulated and transmitted can be demodulated.

The equalizer 10 removes the multipath by correcting the distortion of the I data and the Q data and outputs the data. The channel decoder 12 selects the audio data from the output data of the equalizer 10 and selects the voice decoder 1.
Output to 3. As a result, the voice decoder 13 drives the speaker 14 after demodulating the transmitted audio signal by converting it into I data and Q data.

As a result, the terminal device 1 can receive the voice signal transmitted from the call target via the base station. Further, the equalizer 10 detects the FCCH based on the I data and the Q data output from the analog digital conversion circuit 7, outputs the detection result to the central processing unit (CPU) 15, and the central processing unit 15
Controls the operations of the equalizer 10, the channel decoder 12, etc. based on the detection result.

As a result, the terminal device 1 receives the predetermined information transmitted from the base station on the basis of the FCCH detection result, and switches the frequency of the local oscillation signal based on the reception result, thereby performing a predetermined call. After switching the frequency to the channel, a predetermined time slot can be received to receive a voice signal.

On the other hand, in the transmission system of the terminal device 1, the voice signal output from the microphone 16 is transmitted to the voice encoder 17
After converting to voice data with, channel encoder 18
Is converted into I data and Q data. Further, the digital analog conversion circuit (D / A) 19 converts the I data and Q data into analog signals of I component and Q component,
The mixer 20 converts the analog signal of the I component and the Q component into a transmission signal of a predetermined frequency by using the local oscillation signal.

As a result, the terminal device 1 receives this mixer 20.
Is output to the power amplifier 22 via the filter 21, and the output signal of the power amplifier 22 is transmitted from the antenna 2 via the antenna duplexer 3. At this time, the terminal device 1 switches the transmission and reception timings based on the predetermined timing detection result detected by the equalizer 10, thereby applying the time division multiplexing technique to the base station from a plurality of terminal devices. Among the transmission signals transmitted to the base station, the time slot assigned to the local station is selectively received, and the time slot assigned to the local station is used to transmit the voice data to the base station. There is.

(2) Correction of Frequency of Local Oscillation Signal The terminal device 1 performs frame synchronization with FCCH as a reference,
Further, the frequency of the local oscillation signal is corrected, and further, the entire operation is synchronized with the received data with reference to a predetermined burst, and then a time slot is received to receive desired information. That is, when the power of the terminal device 1 is turned on and the area to which the terminal device belongs is further switched, the central processing unit 15 outputs a control code to the oscillating unit 5 and outputs the BCC.
After receiving H, the control code is output to the equalizer 10 to detect FCCH.

As a result, the central processing unit 15 is
When the timing of CH is detected, the time base counter built in the equalizer 10 is set on the basis of this timing, whereby the whole operation is frame-synchronized. Furthermore, the terminal device 1 corrects the frequency of the local oscillation signal by using FCCH as a reference by controlling the operation of the oscillator 5 with FCCH as a reference.

That is, in the terminal device 1, the error detection circuit 24 sequentially inputs the I data and the Q data output from the analog digital conversion circuit 7, thereby receiving data Xi (which is a demodulation result based on the reference phase). That is, I data) and received data Yi (that is, Q data), which is a demodulation result that is 90 degrees out of phase with this reference signal, are sequentially input and directly output to the equalizer 10. In addition to this, the error detection circuit 24 performs the arithmetic processing described above with respect to the equation (2) to phase-match the received data Xi and Yi so that they are distributed in the vicinity of the I axis, and then, as shown in FIG. This received data Xi and Yi
Are input to the line buffer 25 connected in series by a predetermined number of stages, and are sequentially transferred at the timing of the received data Xi and Yi.

As a result, the error detection circuit 24 generates received data Xi + 1 and Yi + 1 delayed by the number of stages of the buffer 25 with respect to the received data Xi and Yi.

That is, if the averaging operation is performed after detecting the angle θ, the approximation error when the angle θ is detected is accumulated. On the contrary, if the averaging operation is performed beforehand and then the angle θ is detected, the approximation error is approximated. Accumulation of errors can be effectively avoided. Therefore, the terminal device 1 uses the following equation for the phase-matched received data Xi and Yi.

[Equation 6]

[Equation 7] The cumulative data Ai obtained as a result of executing the calculation processing of
And Bi and Ai + 1 and Bi + 1 are central processing units 15
To enter.

Therefore, the error detection circuit 24 generates reception data Xi + 1 and Yi + 1 delayed by the number of stages of the buffer 25 with respect to the reception data Xi and Yi, and the input data Xi of the buffer 25, Yi is cumulatively added by the cumulative adder 26A, and the buffer 2 is calculated from the cumulative addition result.
The output data Xi + 1 and Yi + 1 of 5 are subtracted by the subtractor 26B. As a result, the error detecting circuit 24 receives the received data Xi.
And Yi are cumulatively added by the number of stages of the buffer 25,
The first cumulative data Ai and Bi represented by the equation (6) are stored in the buffer 27.

Further, the error detection circuit 24 has a buffer 25.
The buffer 2 which continues the data stored in the buffer 27 in synchronization with the timing at which the reception data Xi and Yi are transferred.
8 to thereby generate the second cumulative data Ai + 1 and Bi + 1 represented by the equation (7). As a result, the error detection circuit 24 averages the received data in advance, whereas the central processing unit 15 executes the arithmetic processing of the equations (3) to (5) based on the averaged data to calculate the angle. Detect θ.

At this time, the terminal device 1 transfers the data stored in the buffer 27 to the subsequent buffer 28 at the timing of transferring the received data Xi and Yi to accumulate the accumulated data Ai +.
By generating 1 and Bi + 1, as shown in FIG. 3, it is possible to easily reduce the influence of noise by performing arithmetic processing between the output data Ai to Bi + 1 of the error detection circuit 24. The angle θi can be detected with high accuracy.

Further, in the case of this embodiment, the central processing unit 15 takes in a predetermined number of the detected angles θi and cumulatively adds them to average the detection results θi, and based on the average value data obtained as a result. (1) is executed to detect the frequency shift. As a result, the terminal device 1 can control the operation of the oscillating unit 5 based on the frequency shift detection result, and simply and reliably correct the frequency of the local oscillation signal.

(3) Effects of the Embodiments According to the above configuration, after the received data is averaged in advance, the angular displacement between the successively received data is detected, and the frequency of the local oscillation signal is detected based on the detection result. By detecting the deviation, it is possible to effectively avoid the accumulation of approximation errors at the time of angle detection and reduce the influence of noise, and thereby the frequency of the local oscillation signal can be corrected easily and reliably.

(4) Other Embodiments In the above embodiment, the case where the received data Xi and Yi are input to the line buffer 25 connected in series by a predetermined number of stages and the average operation is performed, the present invention is not limited to this. Alternatively, a ring buffer formed so that the pointer shifts may be used.

Further, in the above-described embodiment, the case where the detected angle θ is further cumulatively added and the detection result θ is averaged to detect the frequency deviation is described, but the present invention is not limited to this. For the calculation results of equations (3) and (4), the following equation

[Equation 8] By executing the arithmetic processing of
Of the accumulated angle C and D, and the average value of the angle θ obtained by executing the arithmetic processing of the equations (5) and (1) with the accumulated values C and D.
May be detected. By doing so, the detection accuracy can be further improved.

Further, in the above-mentioned embodiment, the case where the present invention is applied to the digital cellular to correct the frequency of the local oscillation frequency is described. However, the present invention is not limited to this and is applied to various radio receiving devices. Therefore, the present invention can be widely applied to the case where the synchronizing signal of the preset bit pattern is detected and the frequency of the local oscillation signal is corrected.

[0044]

As described above, according to the present invention, after averaging the received data, the angle between the received data is detected and the frequency of the local oscillation signal is corrected to effectively accumulate the approximation error. Can be avoided to reduce the influence of noise, whereby a radio receiving apparatus can be obtained that can easily and reliably correct the frequency deviation of the local oscillation signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing a digital cellular terminal device according to an embodiment of the present invention.

FIG. 2 is a block diagram for explaining the processing of the received data.

FIG. 3 is a schematic diagram for explaining the frequency shift detection.

FIG. 4 is a schematic diagram for explaining a reception result of FCCH.

FIG. 5 is a schematic diagram showing a case where a frequency of a local oscillation signal is shifted.

FIG. 6 is a schematic diagram for explaining a case where noise is further superimposed.

FIG. 7 is a schematic diagram for explaining phase matching.

[Explanation of symbols]

1 ... Terminal device, 2 ... Antenna, 4 ... Mixer, 6 ...
… Filters, 7… Analog digital conversion circuits, 10
…… Equalizer, 15 …… Central processing unit, 24 ……
Error detection circuit.

Claims (3)

[Claims] 1. A radio receiving apparatus for receiving the transmission signal with reference to a synchronization signal inserted in the transmission signal at a predetermined timing, frequency-converts the transmission signal based on a local oscillation signal, and outputs the frequency-converted transmission signal. A frequency conversion circuit, first demodulation means for demodulating the output signal of the frequency conversion circuit with a predetermined reference phase and outputting a first demodulation result, and a phase difference of 90 degrees with respect to the first demodulation result A second demodulation means for outputting a second demodulation result and a predetermined number of the first and second demodulation results are respectively accumulated, and first accumulated data of the first and second demodulation results is outputted. A first averaging means, a second averaging means for accumulating a predetermined number of the first and second demodulation results, respectively, and outputting second accumulated data of the first and second demodulation results, , The first cumulative data and the first And detecting a change in the accumulated data to detect the deviation of the frequency of the local oscillation signal,
And an error detection means for outputting the frequency shift detection result,
A radio receiving apparatus, characterized in that the frequency of the local oscillation signal is corrected based on the frequency shift detection result. 2. The synchronization signal is formed by phase-modulating predetermined reference data, and the first averaging means phase-corrects the first and second demodulation results by the phase-modulated amount. After doing the above first
Of the accumulated data, and the second averaging means phase-corrects the first and second demodulation results by the amount of the phase modulation, and then the second averaging means.
The wireless reception device according to claim 1, wherein the wireless reception device is configured to generate accumulated data of 3. The first averaging means has a shift register circuit connected in series by a predetermined number of stages, and the shift register circuit operates in synchronization with the cycles of the first and second demodulation results. The first and second demodulation results are sequentially transferred, the first and second demodulation results input to the shift register circuit are cumulatively added, and the output data of the shift register circuit is subtracted from the cumulative addition result. To generate the first cumulative data, and the second averaging means holds the first cumulative data only for the cycles of the first and second demodulation results to generate the second cumulative data. The radio receiver according to claim 1 or 2, characterized in that