JP2005318039A - Reception level measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reception level measurement method whereby a downsized and inexpensive means can more accurately measure reception levels of one or more carriers modulated by a CDMA multiplex signal. <P>SOLUTION: An AGC gain calculation means 109 calculates the gain of an AGC amplifier 105 on the basis of a ratio of a first pilot signal PLA digitized through the AGC amplifier 105 to a second pilot signal PLB digitized not through the AGC amplifier 105, and a reception level calculation means 117 obtains power of carriers on the basis of I, Q components of the carriers extracted by a quadrature detection processing and calculates the reception level of the carriers by dividing the power by the second power of the calculated gain. The pilot signal can be sampled with a synchronized pulse by generating the pilot signal used for the measurement by frequency division of the sampling pulse so that an error attended with A/D conversion is principally made a quantization error only, and the gain, that is, the calculation accuracy of the reception level is enhanced and further, the amplitude of the pilot signal is controlled by the gain so that the carrier level output from the AGC amplifier is not too small. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reception level measurement method, and more particularly to a reception level measurement method suitable for a radio system in which each of a plurality of carriers is multiplexed by a CDMA system.

  FIG. 2 is a block diagram showing a schematic configuration of a CDMA radio receiving apparatus including an AGC amplifier. A high frequency signal received by an antenna 201 is converted into an intermediate frequency signal by a frequency conversion unit 202, and a predetermined frequency band is obtained. The desired signal is extracted by the band pass filter 203. Thereafter, the desired signal is amplified by the AGC amplifier 204, digitized by the A / D converter 205, and digitally processed by the quadrature detection unit 206 to generate baseband I and Q (in-phase and quadrature) signal components. The gain of the AGC amplifier is controlled so as to optimize the input signal level to the A / D converter 205.

  The output of the band pass filter 203 is branched and input to an RSSI unit (received signal strength indicator) 207 to perform level measurement, and its analog output is digitized by the A / D converter 208 as data indicating the received level. To be acquired. Although this data is not shown, this data is used to calculate the reception level of each CDMA multiplexed channel, and the reception level of each individual channel is sent to the transmission side through the transmission system, and is received at the transmission side. The transmission level is adjusted so that the reception level on the side becomes an appropriate value. The function used in this CDMA system is called power control, and transmission can be performed with the minimum necessary power. Therefore, in the case of a mobile communication device, the usable time of the power source battery can be increased.

  FIG. 2 shows a configuration with only one carrier. In the case of a multi-carrier system, the block from the bandpass filter 203 to the quadrature detection unit 206, the RSSI unit 207, and the A / D converter 208 are separated for each carrier. Will be provided.

  The RSSI unit 207 measures the level of the input signal using a logarithmic amplifier. The accuracy required for this measurement is ± 2.0 dB, and if possible, ± 0.5 dB or less is required. Yes. However, in the RSSI measurement, the characteristics of the logarithmic amplifier are likely to change due to temperature changes, variations in component characteristics, etc., and it is necessary to provide a correction table in order to obtain the required accuracy, resulting in high costs. In the case of a multi-carrier system, since an RSSI section is provided for each carrier, improvement has been demanded from the viewpoint of cost and mounting.

The above-mentioned RSSI unit detects the envelope of the intermediate frequency signal and measures its level. If the gain of the AGC amplifier is accurately known, the reception level is obtained from the level of the digitized signal. Such a prior art is disclosed in “Digital Receiver” of Patent Document 1. In this prior art, a pilot signal having an amplitude A having a frequency outside the passband of the filter is applied to the bandpass filter output side of the intermediate frequency band, amplified by an AGC amplifier, and the output is A / D converted. A pilot signal component is extracted by a digital filter. A method of obtaining the gain of the AGC amplifier from the ratio between the amplitude of the pilot signal component and the amplitude A at the time of application is used. Even in the case of a multi-carrier system, the circuit from the bandpass filter to the A / D converter has a single system that allows all carrier band signals to pass through.
JP 2002-246828 A

  According to the above-described prior art, since the signal level can be detected mainly by digital processing, it is effective in improving accuracy and simplifying the circuit configuration. However, in the prior art, the level of the signal obtained by collectively frequency-converting, band-limiting, AGC amplification, and A / D conversion of the signals of a plurality of carriers is divided by the gain of the AGC amplifier obtained as described above. Seeking no signal when not. However, in order to accurately digitize the pilot signal by A / D conversion, it is necessary to consider the relationship between the sampling frequency and the frequency of the pilot signal, and unless the amplitude of the pilot signal to be applied is appropriately controlled For example, if the amplitude of the pilot signal is too larger than the signal level, there is a problem that the AGC amplifier gain is controlled by the pilot signal and the signal level is not output at a sufficient level.

  An object of the present invention is to obtain an AGC gain by using a pilot signal, obtain a carrier reception level from the AGC gain, accurately perform digitization of the pilot signal to be used, and perform AGC by applying the pilot signal. An object of the present invention is to provide a reception level measurement method that prevents an amplifier from operating inappropriately.

The present invention receives one or a plurality of carriers, each of which is modulated by a CDMA multiplexed signal, and collectively amplifies the one or a plurality of carriers by an AGC amplifier and then uses a first A / D converter. A method for measuring the reception level of each carrier in a receiver configured to extract the in-phase and quadrature components of a CDMA multiplexed signal corresponding to each carrier by performing quadrature detection processing on one or more carriers that have been digitized and digitized,
A pilot signal whose frequency does not overlap with the frequency bands of the plurality of carriers is added to the one or plurality of carriers as an input of the AGC amplifier, and the pilot signal is amplified by the AGC amplifier and the first A / D converter. The signal digitized by the above AGC amplifier is taken out as a first pilot signal, the pilot signal input to the AGC amplifier is branched and digitized by a second A / D converter as a second pilot signal, The gain of the AGC amplifier is calculated from the ratio between the first pilot signal and the second pilot signal, and is further proportional to the square of the gain of each CDMA multiplexed signal from the in-phase and quadrature components obtained by the quadrature detection processing. The power is calculated, and the reception of the carrier corresponding to each CDMA multiplexed signal is calculated from this power and the calculated gain. With measuring the bell,
The sampling pulse used in the first and second A / D converters is divided by a predetermined ratio, the fundamental wave is taken out, and a signal in which the amplitude of the fundamental wave is controlled by the calculated gain is obtained. Disclosed is a reception level measurement method characterized in that by using a pilot signal, the amplitude of the pilot signal is not more than a predetermined ratio with respect to the amplitude of the plurality of carriers.

  Since the pilot signal is generated by frequency-dividing the sampling pulse, the pilot signal and the sampling pulse are always completely synchronized, and the above-described digital signal is digitized in the first and second A / D converters. There is no error due to the asynchronous nature of the two parties. For this reason, the gain of the AGC amplifier, and hence the reception level of each CDMA multiplexed signal, can be accurately obtained by digital processing, and the level measurement can be performed in a smaller, cheaper and more accurate manner than when the carrier level is directly measured by a logarithmic amplifier. . In addition, by controlling the pilot signal level according to the gain value, the gain of the AGC amplifier is reduced by the large level of the pilot signal, and the carrier level is not sufficiently amplified and A / D converted. The quantization error when the carrier is A / D converted can be kept sufficiently small.

  Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing a configuration example of a receiver equipped with a reception level measuring method of the present invention. Although this receiver will be described below as receiving and demodulating four carriers each modulated by a signal multiplexed by the CDMA system, the present invention limits the number of multicarrier carriers to four. It is not a thing. The operation of this receiver will be described below with reference to the operation explanatory diagram of FIG.

  In FIG. 1, a high frequency signal including four carriers received by the antenna 10 is converted into an intermediate frequency signal by the frequency conversion unit 102. The steps so far are the same as those of the conventional circuit of FIG. Next, the band-pass filter 103 has a frequency characteristic 300 (FIG. 3) for extracting the intermediate frequency signals S of four carriers together. The center frequency of this filter is 46.08 MHz. A pilot signal PL generated by a circuit to be described later is applied to the intermediate frequency signal S output from the bandpass filter 103 by the coupler 104, and then the output amplitude is changed by the AGC amplifier 105 to the dynamic range of the A / D converter 106. The signal is amplified so as to be constant and input to the A / D converter 106. The A / D converter 106 digitizes the input intermediate frequency signal and pilot signal PL for four carriers, and the quadrature detection unit 107 processes the digitized intermediate frequency signal to obtain I, Take out the Q signal (baseband). Also, the digitized pilot signal component is separated by the signal extraction means 108 which is a digital filter and sent to the AGC gain calculation means 109.

  The sampling pulse SP of the A / D converter 106 is generated by the sampling pulse generation circuit 111 from the output of the transmitter 110 (VCXO; Voltage Controlled Crystal Oscilltor). The frequency of this sampling pulse varies depending on whether it is digitized by the undersampling method or digitizing by the oversampling method, but here it is assumed that the frequency is 184.32 MHz which is four times the center frequency of the intermediate frequency signal S. Therefore, the oversampling method is used. In this case, as shown in FIG. 3, an image signal SI or the like of the intermediate frequency signal S is generated by oversampling, but this is easily removed because it is in a high frequency region.

  The sampling pulse SP is frequency-divided into 1/16 times the frequency of 11.52 MHz by the frequency divider 112, converted into a sine wave of that frequency by the band pass filter 113, and then the amplitude is adjusted by the level adjusting means 114. And branching by the coupler 115. One of the branches is added to the intermediate frequency signal S as the pilot signal PL by the coupler 104 described above, and the other is digitized by the A / D converter 116 and input to the AGC gain calculation means 109. The sampling pulse SP of the A / D converter 116 is also the same sampling pulse SP as that of the A / D converter 106. For this reason, the image signal PLI of the pilot signal PL is generated by oversampling in the A / D converter 106 as shown in FIG. 3, but this is also easily removed.

Under the above configuration, the gain g of the AGC amplifier 105 is obtained by the AGC gain calculation means 109 as follows. Now, assume that the amplitude of the output sine wave level of the level adjusting means 114 is A, and this is branched by the coupler 115 so as to have an amplitude of αA to the coupler 104 and βA to the A / D converter 116. However, α + β = 1. The change that the amplitude αA of the pilot signal PL undergoes until it becomes the input PLA of the AGC gain calculation means 109 through the coupler 104, the AGC amplifier 105, the A / D converter 106, the quadrature detection unit 107, and the signal extraction means 108 is AGC The variable gain g of the amplifier and the constant amplitude coefficient k ₁ of other circuits, and the amplitude HA of the input PLA is given by (Equation 1).

On the other hand, since the other branch output from the coupler 115 is directly digitized by the A / D converter 116, the amplitude HB of the other input PLB to the AGC gain calculating means 109 remains β · A. Therefore, the ratio HA / HB of the amplitudes of the two inputs PLA and PLB to the AGC gain calculation means 109 is (Equation 2) and is independent of the output level A of the level adjustment means 114. The (alpha / beta) is constant as a constant in the couplers 115, if obtaining the value in advance by measurement with constant k _1, it calculates a gain g of the AGC amplifier from the ratio HA / HB. The AGC gain calculation means 109 calculates the gain g in this way.

The reception level calculation unit 117 calculates the reception level corresponding to each carrier from the AGC gain g calculated by the AGC gain calculation unit 109 and the signal corresponding to each carrier output from the quadrature detection unit 107. That, I of each carrier corresponding signal from the quadrature detection unit 107, the Q baseband signal is output, I of one signal now, the average value P ₁ of the square sum of the Q component corresponding the carrier The proportional constant is proportional to the square of the received power P _{0 of the} signal and the AGC gain g, and this proportional constant is a value that can be measured in advance with a value k ₂ determined by the amplitude coefficient of each circuit on the signal path other than the AGC amplifier. Multiply by the equation to get (Equation 3)

Accordingly, the received power P ₀ is obtained by dividing the mean square value of the I and Q components by the constant k ₂ and the square of the AGC gain g calculated by the AGC gain calculating means 109, and this is the received level power value. It is.

  According to the configuration example of FIG. 1 described above, the reception level for each carrier can be accurately obtained by digital processing, and not only the circuit can be reduced in size and cost but also the pilot signal can be converted into A / A. Since it is generated by dividing the sampling pulse of the D converter, the sampling pulse for A / D converting the pilot signal and the pilot signal are completely synchronized. Therefore, there is no error when sampling is asynchronous, and accurate digitization is always possible. Further, the sampling pulse generation circuit may be a 1/16 frequency dividing circuit, which can be realized with a very simple configuration of 4 stages of 1/2 frequency dividing, and has an advantage that a dedicated transmitter is not required. In the description of FIG. 1, the A / D conversion is performed by oversampling using a sampling pulse having a frequency four times the center frequency of the intermediate frequency signal, and the pilot signal is generated by dividing the sampling pulse by / 16. Needless to say, these frequencies and frequency division ratios are merely examples, and various changes are possible.

  Further, in the configuration of FIG. 1, the level of the pilot signal is adjusted by the level adjusting means 114. However, as described above, if the level of the pilot signal is larger than that of the received signal, the AGC matches the level of the pilot signal. This is to prevent the received signal level from becoming too small compared to the dynamic range of the A / D converter. In mobile communication or the like, the reception level of the received signal varies greatly, and the same applies to the signal of the entire multicarrier. The gain g of the AGC amplifier is changed by the AGC circuit (not shown) according to this level, but it is calculated by the AGC gain calculation means 109. Therefore, if the AGC gain calculated by the AGC gain calculating means 109 is used as a control signal for the level adjusting means 114, the pilot signal level can be maintained at an appropriate value.

  As a specific configuration method of the level adjusting unit 114, it is desirable in terms of characteristics to finely adjust the level according to the obtained value of the AGC gain g. However, if the level is too fine, the level adjustment means becomes complicated, which is not preferable in terms of cost, and it is preferable to determine the adjustment level width in consideration of a trade-off with characteristics. For example, when gain g is given as 16-bit data, 16 attenuators capable of turning on / off at 6 dB are connected in tandem, and the first is turned on / off by 1 bit of MSB (most significant bit) of gain g. If the second is turned on / off with the MSB and the next bit OR, and the third is turned on / off with the upper 3 bits OR, the pilot signal level can be controlled at intervals of 6 dB.

  Although FIG. 1 illustrates four carriers as an example, the number of carriers is not limited to this, and the present invention is effective even in the case of a single carrier that is not a multicarrier.

  The reception level measuring method of the present invention can be applied to a system that does not have the purpose of power control in a system multiplexed by the CDMA method, as long as it is a system that measures the AGC gain by applying a pilot signal to the AGC amplifier input side. Thus, AGC gain measurement with an accurate and simple configuration can be performed.

It is an example of composition of a receiver provided with a receiving level measuring method of the present invention. It is an example of composition of a receiver provided with the conventional receiving level measuring method. It is a figure which shows the relationship between a desired signal and a pilot signal.

Explanation of symbols

104, 115 Coupler 105 AGC amplifier 106, 116 A / D converter 107 Quadrature detection unit 108 Extraction means 109 AGC gain calculation means 112 Frequency divider 113 Band pass filter 114 Level adjustment means 117 Level calculation means

Claims (1)

Each of them receives one or more carriers modulated by a CDMA multiplexed signal, and the one or more carriers are collectively amplified by an AGC amplifier and digitized by a first A / D converter. A method for measuring the reception level of each carrier in a receiver configured to extract the in-phase and quadrature components of a CDMA multiplexed signal corresponding to each carrier by performing quadrature detection processing on the one or a plurality of carriers,
A pilot signal whose frequency does not overlap with the frequency bands of the plurality of carriers is added to the one or plurality of carriers as an input of the AGC amplifier, and the pilot signal is amplified by the AGC amplifier and the first A / D converter. The signal digitized by the above AGC amplifier is taken out as a first pilot signal, the pilot signal input to the AGC amplifier is branched and digitized by a second A / D converter as a second pilot signal, The gain of the AGC amplifier is calculated from the ratio between the first pilot signal and the second pilot signal, and is further proportional to the square of the gain of each CDMA multiplexed signal from the in-phase and quadrature components obtained by the quadrature detection processing. The power is calculated, and the reception of the carrier corresponding to each CDMA multiplexed signal is calculated from this power and the calculated gain. With measuring the bell,
The sampling pulse used in the first and second A / D converters is divided by a predetermined ratio, the fundamental wave is taken out, and a signal in which the amplitude of the fundamental wave is controlled by the calculated gain is obtained. A reception level measuring method, characterized in that the pilot signal has an amplitude of a predetermined ratio or less with respect to the amplitude of the plurality of carriers.

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