JP2007221297A - Multi-carrier receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-carrier receiver for revising the operations of AGC control depending on level relation between reception levels of channels. <P>SOLUTION: The multi-carrier receiver is provided with a reception level detecting circuit 10 for detecting the reception levels of all the channels; a reception level condition calculating circuit 11 for calculating the presence/absence and the magnitude correlation of the reception levels of all the channels; and an AGC control determining circuit 12 for revising the operation threshold of the AGC, depending on a result of the calculation of the reception level condition calculating circuit 11, and the multicarrier receiver carries out the AGC operation, without causing deterioration in the reception characteristics, under both the real environment condition and disturbance wave selectivity characteristic measurement condition by changing the AGC operation condition by the real environment condition and the disturbance wave selectivity characteristic measurement condition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In a wideband receiver (referred to as a multi-carrier receiver) that collectively demodulates a multi-carrier signal (“carrier” is synonymous with “channel”) by digital signal processing, The present invention relates to prevention of an AGC (Automatic Gain Control) malfunction during measurement of interference wave selectivity characteristics due to a difference in reception level conditions between measurement of interference wave selectivity characteristics.

  In the conventional receiver AGC system, the attenuation of the variable attenuator is adjusted according to the magnitude of the received signal level quantized by the A / D conversion (see, for example, Patent Document 1).

JP-A-8-167820 (FIGS. 1 and 2)

  Since the conventional receiver AGC system is configured as described above, a wideband receiver (hereinafter referred to as a multicarrier receiver) that collectively demodulates a plurality of carrier signals (multicarrier signals) received by a receiving antenna by digital signal processing. On the other hand, when the AGC method is applied, the reception level condition at the time of measuring the interference wave selectivity characteristic in the radio reception standard and the reception level condition in the actual environment are greatly different. There is a possibility that a carrier receiver or an AGC device may operate against an interference wave when measuring an interference wave selectivity characteristic, and it is difficult to satisfy a part of the standard as a wireless receiver by this operation. there were.

  In the above, the reception level condition in the measurement of the interference wave selectivity characteristic in the radio reception standard is that the signal level ratio between the interference signal having a different frequency and the desired signal is large and the reception level of the interference signal is large and desired. A condition where the signal reception level is low. When the AGC is operated by the interference signal by detecting a large interference signal level at the receiver, there is a possibility that the desired signal cannot be demodulated due to a level decrease due to the AGC operation.

  On the other hand, the reception level condition in the real environment is a reception level condition when the receiver is used on a wireless system, and the signal level ratio between the interference wave signal having a different frequency and the desired signal is not so large. The absolute value of the level of the desired signal indicates a condition that is input at a considerably large level. For example, when the wireless communication system is configured with LCX (Leaky Coaxial Cable) and the conditions are such that multiple carrier signals are received from the same base station, the mobile station receives stable transmission power from the base station. Will be. Since this condition is a condition for receiving a multi-carrier signal transmitted from the same base station, the conditions for the transmission path through which the radio waves of the multi-carrier signal pass are the same. It becomes.

  Since the AGC device is designed so that the lowering of the desired signal level is within the range that can be demodulated even when the AGC is operated under such a condition where the multicarrier signal level ratio is small, the anti-jamming wave sensitivity characteristics On the other hand, under conditions far from actual environmental conditions such as measurement conditions, there arises a problem that a desired signal having a low level may not be demodulated due to the AGC operation.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to change the operation of AGC control according to the level relationship of the reception levels of each channel in a multicarrier receiver.

  The receiver AGC system according to the present invention is a multicarrier receiver having AGC control for expanding a dynamic range of a radio receiver, the receiving antenna receiving wideband radio waves for a plurality of channels, and the receiving antenna. A variable attenuator that performs AGC on the multi-carrier signal received in step 1, an A / D converter that digitally converts the multi-carrier signal output from the variable attenuator, and the multi-carrier signal after digital conversion as a signal for each channel. A band-pass filter group to be separated, a reception level detection circuit for detecting a reception signal level of each channel, a reception level condition calculation circuit for obtaining presence / absence and magnitude relationship of each channel, and calculation of the reception level condition calculation circuit An AGC control format that varies the control conditions of the variable attenuator according to the result. Characterized in that it comprises a circuit.

  Hereinafter, various embodiments of the subject of the present invention will be described in detail along with the effects and advantages thereof with reference to the accompanying drawings.

  According to the subject of the present invention, the multi-carrier receiver is configured to change the AGC operation condition by detecting the relationship between the reception levels of all channels (all carriers). Even when the input condition and the reception level input condition at the time of measuring the interference wave selectivity are greatly different, an AGC circuit that operates normally under both conditions can be configured.

(Embodiment 1)
FIG. 1 is a block diagram schematically showing a configuration of a multicarrier receiver or receiver AGC system according to the present embodiment. In FIG. 1, a receiving antenna 1 receives radio waves, and an RF band bandpass filter 2 limits the band of a received signal received by the receiving antenna 1, that is, a multicarrier signal, and only a signal in a desired frequency band. Pass through.

  The variable attenuator 3 is a component responsible for the AGC operation for adjusting the signal level of the reception signal (multicarrier signal) band-limited by the RF band-pass filter 2, and is a control signal output by an AGC control determination circuit 12 described later. The level of the input multi-carrier signal is adjusted based on the condition given by. The high frequency amplifier 4 amplifies the reception signal (multicarrier signal) output from the variable attenuator 3, and the mixer 5 sets the frequency band of the reception signal (multicarrier signal) amplified by the high frequency amplifier 4 to a high frequency band (hereinafter referred to as “high frequency band”). RF band) is converted to an intermediate frequency band (hereinafter referred to as IF band). Here, reference numeral 6 is a local oscillator for converting the received signal (multicarrier signal) from the RF band to the IF band. The IF band-pass filter 7 removes the image frequency generated by the mixer operation and passes only the received signal (multi-carrier signal). The A / D converter 8 receives the received signal (multi-signal) that is an analog signal. (Carrier signal) is converted into a digital signal.

  The channel selection band-pass filter group 9 is a band-pass filter for cutting out only a signal of a desired channel from the reception signals converted into digital signals. That is, the channel selection bandpass filter group 9 has a function of separating the multicarrier signal into signals of each channel having a predetermined frequency.

  The reception level detection circuit 10 calculates and detects the signal level of the reception signal separated into each channel. Further, the reception level condition calculation circuit 11 is a circuit that calculates the relationship between the signal levels of the respective channels. That is, the circuit 11 determines the presence / absence and magnitude relationship of the reception level of each channel, as will be described later. Further, the AGC control determination circuit 12 is a circuit that determines the control value of the variable attenuator 3 according to the condition calculated by the reception level condition calculation circuit 11.

  Next, an operation related to the receiver AGC method will be described. Broadband radio waves for a plurality of channels are received by the receiving antenna 1, and the RF band bandpass filter 2 performs band limitation on the received signal (multicarrier signal). The RF band-pass filter 2 is not a narrow-band band-pass filter, but a wide-band band-pass filter that passes all signals of a plurality of channels. Therefore, the RF band-pass filter 2 has a function of removing only unnecessary radio waves in the wireless system. The band-limited reception signals (multicarrier signals) of the plurality of channels are adjusted by the variable attenuator 3 to a level that does not saturate the A / D converter 8, and then mixed by the local oscillator 6 and the mixer 5. Down-converted from RF band to IF band signal. Thereafter, the reception signals (multi-carrier signals) of a plurality of channels down-converted to the IF band pass through the IF band-pass filter 7, whereby the image frequency component generated by the mixer 5 is removed. The pass band width of the RF band band pass filter 2 and the pass band width of the IF band band pass filter 7 are the same. A plurality of channels of reception signals (multicarrier signals) band-limited by the IF band-pass filter 7 are converted into digital signals by the A / D converter 8. Furthermore, the received signals (multicarrier signals) of a plurality of channels converted into digital signals are subjected to digital signal processing (having the frequency of each channel) by each bandpass filter of the channel selection bandpass filter group 9. The reception level detection circuit 10 calculates the reception signal level of each channel. The calculated signal giving the reception signal level of each channel is input to the reception level condition calculation circuit 11, and the presence / absence and magnitude relationship of the reception level of each channel is obtained by the circuit 11. It is assumed that the calculation result of the circuit 11 takes a binary value meaning “real environment use condition” or “reception standard measurement condition”.

  The operation of the reception level condition calculation circuit 11 will be described in detail below. The circuit 11 calculates the presence / absence and magnitude relationship of the reception level of each channel as follows. As an example, a system in which the number of carriers (number of channels) is 2 will be described. In this case, with respect to the received signal of carrier A and the received signal of carrier B having different frequencies from each other, a) when only either the carrier A signal or the carrier B signal is present, Outputs a value that gives the “standard measurement condition”. On the other hand, when both the carrier A and carrier B signals exist, the power difference between the carrier A signal and the carrier B signal (which is a parameter) is, for example, 30 dB or more. The circuit 11 outputs a value giving “reception standard measurement condition” as a calculation result. On the other hand, when both the carrier A and carrier B signals exist and the power difference (parameter) between the carrier A signal and the carrier B signal is less than 30 dB, for example, the circuit 11 calculates As a result, a value giving "real environment use conditions" is output.

  Next, the AGC control determination circuit 12 changes the AGC operation threshold setting according to the calculation result of the reception level condition calculation circuit 11 (change of the AGC operation condition).

  That is, when the output of the reception level condition calculation circuit 11 is “real environment use condition”, the AGC control determination circuit 12 controls the variable attenuator 3 by a control method having hysteresis characteristics as shown in FIG. To do. As shown in FIG. 2, when the variable attenuator 3 is operated with the antenna input signal level being relatively low, the A / D input signal level is somewhat small, that is, the saturation level of the A / D converter 8 (A in FIG. 2). The variable attenuator 3 is operated (controlled) in a state where there is more margin than (corresponding to / D maximum level). Under the control conditions of the variable attenuator 3 in FIG. 2, the upper limit value of the AGC threshold value is set to a value smaller than the A / D maximum level by the margin, and the lower limit value of the AGC threshold value is A / D input. The signal level is set to a smaller value. In an actual environment where the mobile station moves at a high speed, as shown in FIG. 3, since the level of the received signal fluctuates at a high speed, if the control response of the variable attenuator 3 becomes slower than the reception level fluctuation speed, the variable attenuator 3 may occur before the A / D converter 8 is saturated. If the A / D converter 8 is saturated, distortion may occur in the received signal after A / D conversion, which may cause an error in the received signal processing result and hinder communication. For the purpose of preventing this, as in the control condition shown in FIG. 2, the AGC control determination circuit 12 sets the AGC threshold value with a margin with respect to the saturation level of the A / D converter 8 and makes it variable. The attenuator 3 is operated.

  When the output of the reception level condition calculation circuit 11 is “reception standard measurement condition”, the AGC control determination circuit 12 controls the variable attenuator 3 by a control method having hysteresis characteristics as shown in FIG. As shown in FIG. 4, when the variable attenuator 3 is operated in a state where the antenna input signal level is relatively large, the A / D input signal level is somewhat large, that is, the saturation level of the A / D converter 8 (A in FIG. 4). / D maximum level), the variable attenuator 3 is operated. Among the cases where the reception standard of a radio is measured, as shown in FIG. 5, a disturbing wave having a signal level different from that of a desired signal having a low signal level (the signal shown on the left side of FIG. 5). Under the condition that a signal (the signal shown on the right side of FIG. 5) is input to the receiving antenna 1 (hereinafter referred to as measurement of interference wave selectivity characteristics), the variable attenuator 3 is controlled by the interference wave. As shown in FIG. 6, the level of the desired signal is lowered together with the disturbing wave signal as shown in FIG. Since the level of the desired signal is originally low, if the level of the desired signal is further lowered by the control of the variable attenuator 3 by the interference signal, the desired signal is lowered to an unreceivable level as shown in FIG. It may cause trouble. If the interference wave selectivity characteristic measurement is performed under the control conditions as shown in FIG. 2 described above, the control (AGC operation) of the attenuator 3 is executed by the interference wave signal when the antenna input signal level is relatively low. As a result, the “interfering wave selectivity” indicating the degree to which the desired signal can be demodulated is low. Therefore, in the case of the reception standard measurement condition and the interference wave selectivity characteristic measurement, the control condition (AGC operation condition) as shown in FIG. The AGC threshold value is set equal to the A / D maximum level, and the lower limit value of the AGC threshold value is set to a large value relatively close to the A / D maximum level). (In this case, the interference wave different from the frequency of each channel is removed by the filter of the band-pass filter group 9 for channel selection in FIG. 1). Therefore, the level of the desired signal as already described in FIG. The reduction is not caused, and the interference wave selectivity characteristic is configured to ensure a sufficient characteristic. Under the condition that the interference wave selectivity characteristic is measured, since the steep fluctuation of the antenna input signal level is not expected, the AGC control determination circuit 12 has a margin with respect to the saturation level of the A / D converter 8. Even if the control of the variable attenuator 3 (AGC control) is performed under a condition or condition that does not have the above, there is no particular problem.

  As described above, according to the present embodiment, both the “real environment condition” in which the antenna input signal level fluctuates sharply and the “interference wave selectivity characteristic measurement condition” in which the desired signal level is small and the disturbing wave signal level is large. AGC control that satisfies the above can be performed.

(Appendix)
While the embodiments of the present invention have been disclosed and described in detail above, the above description exemplifies aspects to which the present invention can be applied, and the present invention is not limited thereto. In other words, various modifications and variations to the described aspects can be considered without departing from the scope of the present invention.

It is a block diagram which shows the structure of the multicarrier receiver (receiver AGC system) which concerns on Embodiment 1 of this invention. It is a figure which shows the operation | movement (AGC operation | movement rule) of the AGC control determination circuit when a real environment use condition is detected in the reception level condition calculation circuit. It is a figure which shows the received signal level in real environment use conditions. It is a figure which shows the operation | movement (AGC operation rule) of the AGC control determination circuit when the reception standard measurement condition is detected by the reception level condition calculation circuit. It is a figure which shows the received signal level in case two carrier level difference is large among the interference wave selectivity characteristic measurement conditions in radio | wireless machine reception standard. When measuring the interference wave selectivity characteristics in the radio reception standard, especially when the level difference between two carriers is large, the desired signal with a low reception level cannot be received when the AGC control is performed according to the AGC operation rule of FIG. It is a figure which shows the subject which becomes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reception antenna, 2 RF band band pass filter, 3 Variable attenuator, 4 High frequency amplifier, 5 Mixer, 6 Local oscillator, 7 IF band pass filter, 8 A / D converter, 9 Channel selection band pass filter group, 10 Reception level detection circuit, 11 Reception level condition calculation circuit, 12 AGC control determination circuit.

Claims (3)

In a multi-carrier receiver with AGC control to expand the radio receiver dynamic range,
A receiving antenna for receiving broadband radio waves for multiple channels;
A variable attenuator that performs AGC on the multicarrier signal received by the receiving antenna;
An A / D converter for digitally converting the multicarrier signal output by the variable attenuator;
A bandpass filter group for separating the multicarrier signal after digital conversion into a signal of each channel;
A reception level detection circuit for detecting the reception signal level of each channel;
A reception level condition calculation circuit for obtaining the presence / absence and magnitude relationship of each channel;
An AGC control determination circuit that varies a control condition of the variable attenuator according to a calculation result of the reception level condition calculation circuit;
Multi-carrier receiver. The multi-carrier receiver according to claim 1, wherein
If the calculation result of the reception level condition calculation circuit is a real environment use condition, the AGC control determination circuit controls the variable attenuator with a margin with respect to the saturation level of the A / D converter. Is characterized by
Multi-carrier receiver. The multi-carrier receiver according to claim 1, wherein
When the calculation result of the reception level condition calculation circuit is the reception standard measurement condition and the interference wave selectivity characteristic measurement, the AGC control determination circuit has a margin with respect to the saturation level of the A / D converter. The variable attenuator is controlled in a state where there is no
Multi-carrier receiver.

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