JP2007040740A - Cdma receiver and received electric field detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow accurate received electric field detection even at a high electric field saturating an IF amplifier. <P>SOLUTION: A control section 12 controls a VAGC voltage signal S5 to be output to an AGC amplifier 8 so that an IF digital signal S7 remains constant. The control section 12 measures the value of a base-emitter voltage Vbe of a silicon transistor constituting the IF amplifier 7 by a Vbe voltage detection signal S8. When the measured Vbe voltage is higher than a reference voltage, a received electric field level is estimated on the basis of a VAGC control value for controlling the gain of the AGC amplifier 8. When the measured Vbe voltage is lower than the reference value, it is decided as being in a high electric field state and the received electric field level is estimated from the Vbe voltage using a prepared conversion table. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a CDMA receiver for receiving a radio signal of a CDMA (Code Division Multiple Access) system, and in particular, a received electric field detection for detecting a received electric field level of a received electric field of a received radio signal. Regarding the method.

  In recent years, CDMA communication systems that are resistant to interference and interference have attracted attention as communication systems used in mobile communication systems. One of the CDMA communication systems is a W-CDMA (Wideband CDMA) communication system. In this W-CDMA mobile communication system, a function for detecting the received electric field level of the radio signal from the mobile station to the radio base station apparatus is required to control the transmission power of the mobile station. Therefore, the W-CDMA wireless base station apparatus is provided with a function for receiving a W-CDMA wireless signal and detecting the received electric field level.

  In such a receiver, various techniques have been proposed as a received electric field detection method for detecting a received electric field of a received radio signal (see, for example, Patent Documents 1, 2, and 3). In particular, Patent Document 2 discloses a method for detecting a received electric field level based on the level of a VAGC voltage for performing AGC (Automatic Gain Control) control.

  FIG. 6 shows a configuration of a conventional receiver that performs such a reception electric field detection method. As shown in FIG. 6, the conventional receiver includes an antenna 1 that receives a reception signal S1, an RF amplifier 2 and an RF filter 3 that process the reception signal S1, and a reception signal that has passed through the RF filter 3. In order to perform AGC control, the first mixer 4 that converts the frequency to the first intermediate frequency signal S2, the IF amplifier 5 and the IF filter 6 that process the first intermediate frequency signal S2, the IF amplifier 7 that includes a silicon transistor, and the like. AGC amplifier 8 whose gain is controllable, a second mixer 9 for frequency-converting the signal amplified by the AGC amplifier 8 to a second intermediate frequency signal S3, an A / D converter 10, and a baseband (BB) Unit 11 and a control unit 92. The baseband unit 11 includes a circuit that demodulates the IF digital signal S4 output from the A / D converter 10. The gain of the AGC amplifier 8 is controlled by the VAGC voltage signal S5 input from the control unit 92.

  FIG. 7 shows the configuration of the control unit 92 in FIG. As shown in FIG. 7, the control unit 92 includes a microprocessor (hereinafter referred to as “CPU”) 95 that performs calculation, a read-only memory (hereinafter referred to as “ROM”) 96, and a D / A converter 17. Yes.

  As shown in FIG. 8, the ROM 96 stores two tables: an IF level difference-VAGC variable amount conversion table 22 and a VAGC control value-received electric field report value conversion table 26.

  The IF level difference-VAGC variable amount conversion table 22 is a table for converting an IF level difference, which is a difference between the IF digital signal S7 from the A / D converter 10 and a reference value, into an AGC control amount.

  The VAGC control value-received electric field report value conversion table 26 is a table for calculating the received electric field with respect to the VAGC variable amount.

  The D / A converter 17 generates an analog VAGC voltage signal S5 for controlling the gain of the AGC amplifier 8.

  Next, the operation of the above-described conventional W-CDMA receiver will be described with reference to the drawings.

  A received signal S1, which is a desired wave received by the antenna 1, is amplified by the RF amplifier 2, passes through the RF filter 3, and then converted to the first intermediate frequency signal S2 by the first mixer 4. The first intermediate frequency signal S2 is amplified by the IF amplifier 5, passes through the IF filter 6, and is then amplified again by the IF amplifier 7. The output signal of the IF amplifier 7 is amplified to a signal of a certain level by the AGC amplifier 8, then frequency-converted by the second mixer 9, converted to the second intermediate frequency signal S 3, and input to the A / D converter 10. The

  The A / D converter 10 converts the second intermediate frequency signal S3, which is an analog quantity, into IF digital signals S4, S7, which are digital quantities, and outputs it to the baseband unit 11 and the control unit 92.

  In a mobile communication system such as a mobile phone system, the received electric field level at the radio base station changes every moment as the mobile station moves. However, if the level of the IF digital signal S4 demodulated by the baseband unit 11 fluctuates with the change in the received electric field level, normal demodulation processing cannot be performed. Therefore, the level of the second intermediate frequency signal S3 input to the A / D converter 10 needs to be constant.

  For this purpose, the control unit 92 monitors the IF level of the IF digital signal S7 that is the output of the A / D converter 10, and inputs the IF level to the AGC amplifier 8 so that the IF level becomes constant. The VAGC voltage signal S5 is controlled.

  The AGC control performed in the control unit 92 will be described with reference to the block diagram of FIG.

First, the CPU 95 in the control unit 92 sets the IF reference level 20, and when the IF level 19 which is the value of the IF digital signal S7 is higher than the IF reference level 20, the gain of the AGC amplifier 8 is lowered. When the level is lower than level 20, the gain of the AGC amplifier 8 is increased and control is performed so that the difference between the IF level 19 and the IF reference level 20 becomes zero. Therefore, in the control unit 92, the CPU 95 calculates the IF level difference 21 that is a level difference between the IF level 19 that is the value of the IF digital signal S7 and the IF reference level 20 that is set in advance by the following equation.

IF level difference [dB] = 10 log (IF reference level) -10 log (IF level)

The reason for calculating the IF level difference 21 using a logarithm is that the value of the IF digital signal S7 output from the A / D converter 10 is a linear value, and therefore it is easier to calculate the level if converted to [dB]. is there.

  Furthermore, the CPU 95 refers to the IF level difference 21 described above with reference to the IF level difference-VAGC variable amount conversion table 22 stored in the ROM 96, and derives the VAGC variable amount 23 corresponding to the IF level difference 21.

  The calculated VAGC variable amount 23 is converted into a VAGC voltage signal S5 by the D / A converter 17 as a digital signal S6, and the gain of the AGC amplifier 8 is controlled.

As shown in FIG. 8, the IF level difference-VAGC variable amount conversion table 22 has a one-to-one correspondence between the above-described IF level difference 21 and VAGC variable amount 23, and the VAGC variable amount at this time. The gain [dB] of the AGC amplifier 8 that is varied by 23 has the following relationship with the absolute amount [dB] of the IF level difference 21.

Gain [dB] of AGC amplifier 8 = −IF level difference [dB]

Next, the CPU 95 updates the VAGC control value. If the current AGC control value before the VAGC variable 23 is added is the VAGC control value (old) 24, and the new AGC control value after the VAGC variable 23 is added is the VAGC control value (new) 25. The following relational expression holds.

VAGC control value (new) 25 = VAGC control value (old) 24 + VAGC variable amount

The CPU 95 controls the gain of the AGC amplifier 8 based on the VAGC control value (new) 25 updated in this way.

  As an example, -90 dBm electric field detection when the received electric field level is increased from -93 dBm to -90 dBm will be described.

In this case, the received electric field level is increased by 3 dB. Here, it is assumed that the IF reference level 20 is set to “80”. If the reception electric field level increases in this case, the IF level 19 that is the input level of the A / D converter 10 that has converged to the reference level “80” is changed from “80” to “160”. When the IF level difference 21 is calculated by the above formula,

IF level difference [dB] = 10 log (80) -10 log (160) =-3 dB

Thus, the IF level difference 21 is 3 dB. When this value is converted into the VAGC variable amount 23 by the IF level difference-VAGC variable amount conversion table 22 shown in FIG. Since the VAGC control value (old) 24 that is the current VAGC control value is “900”,

VAGC control value (new) = VAGC control value (old) + VAGC variable amount
= 900 + (− 40) = 860

Therefore, the new VAGC control value (new) 25 is 860. When this value is converted into the VAGC voltage signal S5 by the D / A converter 17,

VAGC voltage signal S5 = 3 × 860/2 ¹⁰ = 2.52 [V]

It becomes. When the VAGC control value 24 is a value of 900 hours, the AGC amplifier 8 is controlled by a voltage 0.12 [V] lower than the voltage 2.64 [V] for controlling the AGC amplifier 8 by the VAGC voltage signal S5. To reduce the 3 dB gain. As a result, the IF level of the IF digital signals S4 and S7 output from the A / D converter 10 is “80”. Then, since the VAGC control value is changed from “900” to “860”, the CPU 95 refers to the VAGC control value-received electric field report value conversion table 26 shown in FIG. 8 to change the received electric field level from −93 dBm. It can be detected that −90 dBm is reached.

  By performing such AGC control, the input level and output level of the A / D converter 10 are controlled to be constant without being affected by the received electric field level. The CPU 95 can detect the current received electric field level by comparing the VAGC control value for performing the AGC control with the VAGC control value-received electric field report value conversion table 26.

  As described above, according to the conventional received electric field detection method for detecting the received electric field level based on the VAGC control value, the received electric field level can be detected with considerable accuracy when the received electric field level itself is not so high. Is possible. However, there is a problem that the received electric field level cannot be accurately detected when the received electric field level is high. The reason is described below.

  In the W-CDMA receiver, the first-stage RF amplifier 2 has a high input resistance, but the IF amplifier 7 is configured using a relatively inexpensive silicon transistor device having a high gain and low input resistance. At that time, as shown in FIG. 10, the received signal level is low when the normal reception is low, but there is no problem, but when the high electric field is received, the AGC amplifier 8 is not saturated but the IF amplifier 7 with low input resistance is saturated. Resulting in. That is, the operating point of the IF amplifier 7 moves, Vbe (base-emitter voltage) decreases, from 0.7 V to 0.5 V, as shown in FIG. When an electric field is input, the input signal approaches Vebo. In this state, as shown in FIG. 12, a saturation region where the output is saturated is reached, so that a linear output with respect to the input cannot be obtained.

  The conventional W-CDMA receiver is based on the premise that the total gain up to the AGC amplifier 8 is constant. That is, in the conventional W-CDMA receiver, in order to accurately detect the received electric field, each device must be used in a region having linearity, and as described above, when the device approaches the saturation region. The received electric field was not accurately reported. This is because, when the saturation level where the output of the IF amplifier 7 becomes constant with respect to the input level as shown in FIG. 12 is reached, the input electric fields of the A / D converter 10 and the AGC amplifier 8 are changed even if the reception electric field level increases or decreases. This is because the received electric field level is detected as if it has not changed, and an accurate received electric field report cannot be expected. Further, when the electric field is high, as shown in FIG. 13, the output level is lowered by the IF amplifier 7 even if the reception electric field level is increased.

If an expensive device with a high gain and a high IP is used for the IF amplifier 7, the above problem can be solved. However, using a high-IP, high-current device causes a problem that power consumption increases with an increase in cost, which is not realistic. After using an IF amplifier 7 composed of a silicon transistor device, There is a need for a received electric field detection method that can accurately detect the received electric field level even when an electric field is applied.
JP 2000-261339 A JP 2002-335139 A JP 2003-348025 A

  The above-described conventional CDMA receiver has a problem in that when the reception electric field level becomes high and reaches a saturation region where the output of the IF amplifier becomes constant, the reception electric field level cannot be accurately detected.

  An object of the present invention is to provide a CDMA receiver and a received electric field detecting method capable of accurately detecting a received electric field even in a high electric field.

In order to achieve the above object, a reception electric field detection method of the present invention is a reception electric field of a received radio signal in a receiver including an IF amplifier configured by a silicon transistor and an AGC amplifier for performing AGC control. A received electric field detection method for detecting a level, comprising:
Measuring a base-emitter voltage of the silicon transistor;
When the measured base-emitter voltage is larger than a preset reference voltage, the received electric field level is estimated based on the VAGC control value for controlling the gain of the AGC amplifier, and the measured And a step of estimating a received electric field level based on the base-emitter voltage when the base-emitter voltage is equal to or lower than a preset reference voltage.

  According to the present invention, when the Vbe voltage of the IF amplifier is smaller than a preset comparison reference voltage, it is determined that the electric field is high, and the received electric field level is based on the Vbe detection value instead of the VAGC control value. Therefore, even when the received electric field level is high, the received electric field can be detected accurately.

  As described above, according to the present invention, when the Vbe voltage of the IF amplifier is smaller than a preset comparison reference voltage, the received electric field level is detected based on the Vbe detection value instead of the VAGC control value. As a result, it is possible to obtain an effect that accurate reception electric field detection is possible even when the reception electric field level is high.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing the configuration of the receiver according to the first embodiment of the present invention. In FIG. 1, the same components as those in FIG. 6 are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 1, the receiver of the present embodiment includes an antenna 1, an RF amplifier 2, an RF filter 3, a first mixer 4, an IF amplifier 5, an IF filter 6, an IF amplifier 7, AGC amplifier 8, second mixer 9, A / D converter 10, baseband (BB) unit 11, and control unit 12.

  The receiver of this embodiment is different from the conventional receiver shown in FIG. 6 in that the control unit 92 is replaced with the control unit 12 and the base-emitter voltage (hereinafter referred to as Vbe) of the silicon transistor constituting the IF amplifier 7. The difference is that the Vbe voltage detection signal S8 that detects the voltage is input to the control unit 12.

  Next, FIG. 2 shows the configuration of the control unit 12 in FIG. As shown in FIG. 2, the control unit 12 in the present embodiment includes a CPU 15, a ROM 16 that is a recording unit, a D / A converter 17, and an A / D converter 18.

  The control unit 12 in this embodiment has a configuration in which the CPU 95 and the ROM 96 are replaced with the CPU 15 and the ROM 16, respectively, and an A / D converter 18 is added to the control unit 92 in the conventional receiver shown in FIG. . The A / D converter 18 A / D converts the Vbe voltage detection signal S8 of the IF amplifier 7 into a digital signal S9.

  As shown in FIG. 3, the ROM 16 includes a Vbe detection value-received electric field report value conversion table 27 in addition to an IF level difference-VAGC variable amount conversion table 22 and a VAGC control value-received electric field report value conversion table 26. It is a newly added configuration.

  The Vbe detection value-received electric field report value conversion table 27 is a table for estimating the received electric field from the Vbe voltage of the IF amplifier 7, and the Vbe detection value and the received electric field report value correspond one-to-one.

  The control unit 12 calculates the AGC amplifier control value necessary for the function of detecting the input level to the A / D converter 10 and the input level of the A / D converter 10 to be a predetermined level. A function for controlling the gain and a function for detecting the Vbe voltage of the IF amplifier 7 are provided.

  The reception electric field detection method of this embodiment is different from the conventional reception electric field detection method in that a Vbe voltage of the IF amplifier 7 is newly used in order to accurately detect reception electric field detection at a high electric field. .

  Next, the received electric field detection method in the receiver of this embodiment will be described in detail with reference to the drawings.

  The reception electric field detection method of this embodiment is shown in the flowchart of FIG. First, in the receiver of the present embodiment, when the received electric field level is detected, the CPU 15 in the control unit 12 sets the voltage of the Vbe voltage detection signal S8 of the IF amplifier 7 to a preset Vbe reference value. (Step 401).

  When it is determined that the voltage of the Vbe voltage detection signal S8 of the IF amplifier 7 is higher than a preset Vbe reference voltage, it is determined that the IF amplifier 7 is not saturated and a high electric field is not input, and the CPU 15 Refers to the VAGC control value-received electric field report value conversion table 26, which is a table showing the relationship between the VAGC control value and the received electric field detection value stored in the ROM 16, and the above VAGC control value (new) 24 A received electric field report value is obtained (step 402). In this VAGC control value-received electric field report value conversion table 26, the VAGC control value and the received electric field report value correspond one-to-one. As a result, it is possible to detect the received electric field report value of the desired wave from the VAGC control value. Since the operation up to this point is the same as the reception electric field detection method in the conventional CDMA receiver, detailed description is omitted.

  If it is determined in step 401 that the voltage of the Vbe voltage detection signal S8 of the IF amplifier 7 is equal to or lower than a preset Vbe reference voltage, the CPU 15 determines that the IF amplifier 7 is saturated and determines VAGC. Instead of detecting the received electric field based on the control value, the Vbe detected value is converted into the received electric field reported value using the Vbe detected value-received electric field reported value conversion table 27 (step 403).

Next, a specific example of the received electric field detection method of this embodiment will be described. Here, it is assumed that the Vbe reference voltage is set to 0.6 V around which the Vbe voltage starts to drop and the IF amplifier 7 approaches the saturation region. (See Figure 12)
For example, it is assumed that the CPU 15 starts detection of the received electric field and detects the Vbe voltage of the IF amplifier 7 by the Vbe voltage detection signal S8 when the electric field is normal, and is 0.7V. Then, since the Vbe voltage is larger than the Vbe reference voltage 0.6V, the CPU 15 determines that the electric field is not high (Y in step 401 in FIG. 4), and enters the VAGC control value-received electric field report value conversion table 26. Then, the received electric field is detected by converting the value “860” of the VAGC control value 24 into the received electric field report value “−90 dBm” (step 402).

  Next, detection of an electric field of -35 dBm when the reception electric field level is increased from -45 dBm to -35 dBm will be described as a specific example at the time of a high electric field.

  Referring to the level diagram shown in FIG. 10, when the reception electric field level is a high electric field of −35 dBm, the input level of the IF amplifier 7 is −15 dBm, so that the IF amplifier 7 enters the saturation region. Therefore, the value of the digital signal S9 representing the digital amount of the Vbe voltage detection signal S8 of the IF amplifier 7 is lower than the Vbe reference voltage “205” (0.6 V after D / A conversion), and is “119” (D / Therefore, the CPU 15 determines that the received electric field report value corresponding to the above-mentioned “119” is − according to the Vbe detection value-received electric field report value conversion table 27 −. The result is 35 dBm. This makes it possible to accurately detect the received electric field when the electric field is high.

  Next, the case where the received electric field detection is performed by the conventional received electric field detection method at the time of high electric field reception will be described.

  Since the IF amplifier 7 is approaching the saturation region, as shown in FIG. 12, the output level is saturated with respect to the input level of −15 dBm. The fact that the output of the IF amplifier 7 is saturated in the block diagram shown in FIG. 1 means that the VAGC voltage CPUS5 of the AGC amplifier 8 is constant because the input level of the A / D converter 10 thereafter does not change. As a result, the received electric field report value should be reported as -35 dBm as originally shown in FIG. 13, but it is reported as -33 dBm, and an incorrect report value is output. On the other hand, according to the received electric field detection method of this embodiment, as described above, an accurate result of −35 dBm can be obtained.

  As described above, according to the receiver of the present embodiment, by detecting the Vbe of the silicon transistor constituting the IF amplifier 7 in a region where the output of the IF amplifier 7 is saturated, it is possible to accurately detect the received electric field even in a high electric field. Therefore, the dynamic range of the received electric field detection can be expanded. As a result, in the conventional W-CDMA receiver, when the IF amplifier 7 is approaching the region where the output decreases in the saturation region, it erroneously detects as if the reception electric field has increased even if it has decreased. The phenomenon can be prevented.

  That is, according to the present embodiment, the dynamic range of the received electric field detection can be expanded by switching between two types of received electric field detection methods based on the VAGC control value and the Vbe voltage according to the received electric field level.

(Second Embodiment)
Next, a CDMA receiver according to the second embodiment of the present invention will be described.

  A CDMA receiver according to a second embodiment of the present invention is shown in FIG. In the CDMA receiver according to the first embodiment shown in FIG. 1 described above, the IF amplifier 7 for amplifying the intermediate frequency signal after passing through the IF filter 6 is assumed to be composed of a silicon transistor. However, in the present embodiment, the present invention is applied to the case where the IF amplifier 5 for amplifying the intermediate frequency signal before being input to the IF filter 6 is also composed of a silicon transistor. In FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 5, the receiver according to the present embodiment configures an IF amplifier 7 by replacing the control unit 12 with a control unit 52 with respect to the receiver according to the first embodiment shown in FIG. 1. The difference is that not only the Vbe voltage detection signal S8 of the silicon transistor but also the Vbe voltage detection signal S9 of the silicon transistor constituting the IF amplifier 5 is input to the control unit 52.

  In the received electric field detection method according to the present embodiment, it is possible to detect the received electric field more accurately by monitoring the Vbe voltage of the IF amplifier 5 as well as the IF amplifier 7 to detect the received electric field. It becomes. For example, when the IF amplifier 5 starts to saturate after the IF amplifier 7 in a high electric field, the Vbe of the IF amplifier 7 is detected by detecting the Vbe of the IF amplifier 5 together with the Vbe of the IF amplifier 7. Compared to the case, it is possible to detect the received electric field at a higher electric field.

  In the first and second embodiments, the received electric field detection method in the CDMA receiver has been described. However, the present invention is not limited to this, and the received electric field is detected in a receiver using another communication method. Even in this case, the present invention can be similarly applied.

It is a block diagram which shows the structure of the receiver of the W-CDMA system of the 1st Embodiment of this invention. It is a block diagram which shows the structure of the control part 12 in FIG. It is a figure which shows the table in ROM16 in FIG. It is a flowchart which shows the received electric field detection method in the W-CDMA receiver of the 1st Embodiment of this invention. It is a block diagram which shows the structure of the receiver of the W-CDMA system of the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the receiver of the conventional W-CDMA system. It is a block diagram which shows the structure of the control part 92 in FIG. It is a figure which shows the table in ROM96 in FIG. It is a block diagram for demonstrating AGC control in the receiver of a W-CDMA system. It is a figure which shows the example of the level diagram at the time of high input and low input. It is a figure which shows the relationship between the input electric field level of the silicon transistor IF amplifier 7, and Vbe (base-emitter voltage). It is a figure which shows the relationship between the output level with respect to the input level of the silicon transistor IF amplifier 7, and Vbe. It is a figure which shows the received electric field report value with respect to an input electric field.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 RF amplifier 3 RF filter 4 1st mixer 5 IF amplifier 6 IF filter 7 IF amplifier 8 AGC amplifier 9 2nd mixer 10 A / D converter 11 Baseband (BB) part 12 Control part 15 Microprocessor (CPU)
16 Read-only memory (ROM)
17 D / A converter 19 IF level 20 IF reference level 21 IF level difference 22 IF level difference-VAGC variable amount conversion table 23 VAGC variable amount 24 VAGC control value (old)
25 VAGC control value (new)
26 VAGC control value-reception field report value conversion table 27 Vbe detection value-reception field report value conversion table 52 Control unit 92 Control unit 95 Microprocessor (CPU)
96 Read-only memory (ROM)
401 to 403 Steps S1 Reception signal S2 First intermediate frequency signal S3 Second intermediate frequency signal S4 IF digital signal S5 VAGC voltage signal S6 Digital signal S7 IF digital signal S8, S9 Vbe voltage detection signal

Claims (3)

In a receiver including an IF amplifier configured by a silicon transistor and an AGC amplifier for performing AGC control, a received electric field detection method for detecting a received electric field level of a received radio signal,
Measuring a base-emitter voltage of the silicon transistor;
When the measured base-emitter voltage is larger than a preset reference voltage, the received electric field level is estimated based on the VAGC control value for controlling the gain of the AGC amplifier, and the measured And a step of estimating a received electric field level based on the base-emitter voltage when the base-emitter voltage is equal to or lower than a preset reference voltage. In a CDMA receiver having an IF amplifier configured by a silicon transistor and an AGC amplifier for performing AGC control,
An A / D converter for converting a base-emitter voltage value of a silicon transistor constituting the IF amplifier into a digital signal, and a conversion table for calculating a received electric field level from the base-emitter voltage value converted into the digital signal When the measured base-emitter voltage is larger than a preset reference voltage, the received electric field is based on a VAGC control value for controlling the gain of the AGC amplifier. A control unit that estimates a level and estimates a received electric field level from the base-emitter voltage using the conversion table when the measured base-emitter voltage is equal to or lower than a preset reference voltage; A CDMA receiver.   A first IF amplifier for amplifying the intermediate frequency signal before the IF amplifier is input to the IF filter; and a second IF amplifier for amplifying the intermediate frequency signal after passing through the IF filter; The CDMA receiver according to claim 2, comprising:

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