JP2006254109A - Receiving device, and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiving device which is possible to change an output C/N (Carrier to Noise ratio) characteristic, and to provide its control method. <P>SOLUTION: A high frequency amplifier 12, a low frequency amplifier 17, and an output amplifier 20 are changed to gain variable amplifiers. If an input signal level inputted through a high frequency signal input terminal 11 is higher than a certain magnitude, a gain of the high frequency amplifier 12 is set larger, a gain of the low frequency amplifier 17 is not changed, and a gain of the output amplifier 20 is set small. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a receiving device such as a digital satellite broadcast receiving device and a control method thereof. More specifically, the present invention relates to a receiving apparatus that can change an output C / N characteristic according to an application and a control method thereof.

  In digital satellite broadcasting, the input signal level varies widely depending on the installation conditions of the receiving device and the receiving channel, so the gain of the receiving device is set appropriately according to the input signal level and the output signal level is constant. A control loop is used.

  FIG. 10 is a block diagram showing the configuration of a general direct conversion satellite broadcast receiving apparatus. For example, Patent Document 1 discloses gain control in such a conventional general reception device.

  10 includes a high frequency signal input terminal 101, a high frequency amplifier (high frequency gain variable amplifier) 102, a gain control terminal 103, a mixer circuit 104, an oscillation circuit 105, a 90-degree phase shift circuit 106, a low frequency amplifier (low frequency). Gain variable amplifier) 107, gain control terminal 108, filter circuit 109, output amplifier 110, and output terminal 111.

  The high frequency signal input terminal 101 receives a high frequency signal received from the outside of the receiving device. The high frequency amplifier 102 is a variable gain high frequency amplifier that amplifies a high frequency signal input via the high frequency signal input terminal 101. A control signal for controlling the gain of the high-frequency amplifier 102 is input to the gain control terminal 103 from a control circuit (not shown).

  The mixer circuit 104 performs frequency conversion on the output signal of the high-frequency amplifier 102. The oscillation circuit 105 generates an oscillation signal and supplies it to the 90-degree phase shift circuit 106. The 90-degree phase shift circuit 106 generates two local signals having a phase difference of 90 degrees from the oscillation signal supplied from the oscillation circuit 105 and supplies the two local signals to the mixer circuit 104.

  The low frequency amplifier 107 is a variable gain low frequency amplifier that amplifies the signal output from the mixer circuit 104. A control signal for controlling the gain of the low-frequency amplifier 107 is input to the gain control terminal 108 from a control circuit (not shown).

  The filter circuit 109 is a filter circuit that removes unnecessary frequency components included in the output signal of the low-frequency amplifier 107. The output amplifier 110 amplifies the output signal of the filter circuit 109 and outputs it from the output terminal 111.

  In the receiving apparatus shown in FIG. 10, the gains of the high frequency amplifier 102 and the low frequency amplifier 107 depend on the signal level of the high frequency signal input from the output terminal 111 via the high frequency signal input terminal 101. It is controlled so as to be constant. FIG. 11 is a graph (level distribution diagram) showing signal levels at various parts of the receiving apparatus shown in FIG.

  As shown in FIG. 11, even when the signal level input to the high frequency signal input terminal 101 fluctuates, the gain of the high frequency amplifier 102 and the low frequency amplifier 107 is appropriately controlled to be output from the output terminal 111. The output signal level can be made constant.

  As shown in FIG. 11, the control of the high-frequency amplifier 102 and the low-frequency amplifier 107 is performed when the input signal level is equal to or lower than a predetermined value, the lower of the two gain variable amplifiers (the high-frequency amplifier 102 and the low-frequency amplifier 107). The gain of the frequency amplifier 107 is changed, and when the input signal level is higher than a predetermined value, the gain of the high frequency amplifier 102 is changed. As a result, the noise figure and distortion characteristics of the entire receiving apparatus can be made relatively good.

  In general, in a receiving apparatus, no matter what gain control is performed, a noise component is included in an output signal. This noise component is an important parameter for determining the reception performance of the receiving apparatus.

  For example, consider output noise in the receiving apparatus shown in FIG. When the signal level of the high frequency signal input through the high frequency signal input terminal 101 is low, the gains of the high frequency amplifier 102 and the low frequency amplifier 107 are set high. For this reason, noise generated in the first half of the receiving device (for example, the high-frequency amplifier 102 and the mixer circuit 104) is amplified, so that the noise characteristic of the first half of the receiving device is dominant over the output noise level of the receiving device. Become.

  Conversely, when the signal level of the high frequency signal input via the high frequency signal input terminal 101 is high, the gains of the high frequency amplifier 102 and the low frequency amplifier 107 are set low. Therefore, rather than the noise characteristic of the first half of the receiving apparatus, the characteristic of the worst part of the C / N (ratio of signal level to noise level) in the output of each circuit block shown in FIG. Dominant over the noise level.

  FIG. 12 plots the input signal input to the output amplifier 110 of the receiving apparatus shown in FIG. 11 and the output signal from the output amplifier 110 corresponding to this input signal, with the horizontal axis representing frequency and the vertical axis representing signal level. It is a graph. The left graph in FIG. 12 shows an input signal to the output amplifier 110, and the right graph shows an output signal from the output amplifier 110.

  As shown in FIG. 12, the input C / N of the output amplifier 110 is represented by the ratio (Ci / Ni) between the input signal level Ci and the input noise floor level Ni.

  When the gain of the output amplifier 110 is G1, the waveform of the output signal of the output amplifier 110 (output terminal 111) is as shown in the graph on the right side of FIG. That is, the output signal level Co is a signal level obtained by multiplying the input signal level Ci by the gain G1, and the output noise level No is a noise level obtained by multiplying the input noise floor level Ni by the gain G1. Further, the output C / N of the receiving apparatus is represented by the ratio (Co / No) between the output signal level Co and the output noise level No. Since noise is actually added by the output amplifier 110, the amount of increase in noise between the input and output of the output amplifier 110 is slightly larger than the amount of increase corresponding to the gain G1, but generally this error is gain G1. It can be ignored compared to.

As described above, since the output signal level of the receiving apparatus shown in FIG. 10 is kept constant by the two variable gain amplifiers, the output signal level Co shown in FIG. Gain is controlled.
JP 2002-76805 A (publication date March 15, 2002)

  However, in the receiving apparatus having the conventional configuration as described above, when the required output C / N is different, it is necessary to design the receiving apparatus separately for each output C / N. Therefore, for example, when a receiving device as shown in FIG. 10 is formed on a semiconductor integrated circuit, separate semiconductor integrated circuits must be prepared according to the required output C / N.

  For example, a digital satellite broadcast receiver that receives a QPSK modulated signal and a digital satellite broadcast receiver that receives an 8PSK modulated signal can be realized with the same circuit configuration with respect to the portion shown in FIG. However, a digital satellite broadcast receiver that receives an 8PSK modulated signal is required to have a higher output C / N. That is, even in a receiving device having the same circuit configuration, the required output C / N may differ depending on the type of received signal or the use of the receiving device.

  In such a case, the output C / N of the receiving device is determined by the performance of each circuit block constituting the receiving device. For this reason, it is necessary to design separately the receiving apparatuses (for example, the receiving apparatus for QPSK modulation signals and the receiving apparatus for 8PSK modulation signals) having different required output C / N. That is, when a receiving apparatus as shown in FIG. 10 is configured on a semiconductor integrated circuit, separate semiconductor integrated circuits must be prepared according to the required output C / N.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a receiving apparatus capable of switching output C / N characteristics and a control method therefor.

  In order to solve the above problems, a receiving apparatus of the present invention includes a first amplifying unit that amplifies an input signal, a frequency converting unit that converts a frequency of an output signal of the first amplifying unit, and the frequency converting unit. A receiving apparatus including an output amplifying unit that amplifies and outputs a subsequent signal, wherein the gain of the output amplifying unit is variable.

  According to said structure, the gain of the said output amplification means is variable. As a result, the output C / N characteristic of the receiving apparatus can be switched and used in accordance with the output C / N required for the receiving apparatus (the ratio between the output signal level and the output noise level). That is, the output C / N characteristic can be switched according to the use of the receiving apparatus. Therefore, even when the required output C / N is different (or changes), it is not necessary to use a receiving device designed individually for each application, and reception is appropriately performed using the same receiving device. be able to.

  Moreover, it is good also as a structure provided with the 2nd amplification means which amplifies the signal after the said frequency conversion, and the said output amplification means amplifies and outputs the signal after being amplified by the said 2nd amplification means.

  According to the above configuration, the second amplifying means is provided in addition to the first amplifying means and the output amplifying means. For this reason, the gain of the whole receiving apparatus can be increased. In addition, in order to achieve the required output signal level, the gain required for each amplifying means can be reduced.

  In addition, an unnecessary component removing unit that removes an unnecessary frequency component included in the signal after the frequency conversion is provided, and the output amplification unit amplifies the signal after the unnecessary frequency component is removed by the unnecessary component removing unit. It is good also as a structure to output.

  According to said structure, the unnecessary frequency component contained in the signal after the said frequency conversion can be removed by the said unnecessary component removal means, and the quality of the output signal from a receiver can be improved.

  The gain of the output amplifying unit may be configured to include a control unit that controls the gain according to the set output signal level. Here, the set output signal level may be set to a constant value according to the use of the receiving device, or may be arbitrarily set by the user via the input means. Also good.

  According to said structure, a control means controls the gain of an output amplification means according to the set output signal level. As a result, even when the output signal level required according to the use of the receiving device is different (or changed), it is possible to receive appropriately using the same receiving device.

  The control means may be configured to control the gain of the output amplifying means in accordance with the signal level of the signal input to the first amplifying means.

  According to said structure, the said control means controls the gain of the said output amplification means according to the set output signal level and the signal level of the signal input into the said 1st amplification means. Thereby, for example, the gain of the output amplifying means can be controlled so that the set output signal level can be achieved and the output noise level is lowered. Therefore, even when the output signal level required for the receiving apparatus is different (or changes), the required output signal level can be achieved according to the signal level of the signal input to the first amplifying means, and Therefore, it is possible to appropriately receive so as to improve the output C / N characteristic.

  The first amplifying means is a gain variable amplifying means, and can satisfy a set output signal level according to a signal level of a signal input to the first amplifying means, and the output. A configuration may be adopted in which a second control means is provided for controlling the gains of the first amplification means and the output amplification means so that the gain of the amplification means becomes as small as possible.

  According to the above configuration, the second control means can satisfy the set output signal level according to the signal level of the signal input to the first amplification means, and the output amplification means The gains of the first amplifying unit and the output amplifying unit are controlled so that the gain is as small as possible. In general, the output noise level in the receiving apparatus configured as described above depends more on the output amplifying means than on the first amplifying means. For this reason, the output C / N characteristic can be improved by reducing the gain of the output amplifying means as much as possible within a range in which the set output signal level can be satisfied.

  The first amplifying means and the second amplifying means are variable gain amplifying means, and can satisfy a set output signal level according to a signal level of a signal input to the first amplifying means. And third control means for controlling the gains of the first amplification means, the second amplification means, and the output amplification means so that the gains of the output amplification means and the second amplification means become as small as possible. It is good also as a structure.

  According to the above configuration, the third control unit can satisfy the set output signal level according to the signal level of the signal input to the first amplification unit, and the output amplification unit and The gains of the first amplification unit, the second amplification unit, and the output amplification unit are controlled so that the gain of the second amplification unit is as small as possible. The output noise level in the receiving apparatus configured as described above depends more on the second amplifying means and the output amplifying means than on the first amplifying means. Therefore, the output C / N characteristics can be improved by reducing the gains of the second amplifying means and the output amplifying means as much as possible within a range in which the set output signal level can be satisfied.

  The first amplifying means and the second amplifying means are variable gain amplifying means, and the gain of the output amplifying means is set to the set output signal level and the gain of the first amplifying means and the second amplifying means. It is good also as a structure provided with the 4th control means controlled based on these.

  According to the above configuration, the fourth control unit controls the gain of the output amplification unit based on the set output signal level and the gains of the first amplification unit and the second amplification unit. Thus, even when the output signal level required for the receiving apparatus is different (or changes), the receiving process can be appropriately performed using the same receiving apparatus.

  Further, the output amplification means may be configured to switch the gain stepwise. In this case, the circuit configuration for switching the gain of the output amplification means can be simplified, and the gain of the output amplification means can be easily switched.

  For example, the control means for controlling the gain of the output amplification means may be provided, and the control means may be configured to switch the gain of the output amplification means stepwise by changing a set value of a register provided in the control means. Good. In this case, the gain of the output amplifier circuit can be easily switched by the control means changing the set value of the register.

  The output amplifying unit may include a plurality of amplifying units having different gains, and the gain may be changed by selecting any one of the amplifying units from the plurality of amplifying units. According to said structure, the said output amplification means is easily realizable.

  In this case, the output amplification means may be configured to turn off the power of the amplification means that are not selected from among the plurality of amplification means. According to said structure, the current consumption of an output amplification means and the said receiver 1 can be reduced.

  The output amplifying means may be composed of a feedback amplifier and resistance changing means for changing the feedback resistance value of the feedback amplifier. In this case, the resistance variable means includes a plurality of resistance means having different resistance values arranged in parallel with the feedback amplifier, and a resistance means arranged in series with each of the resistance means and used as a feedback resistance of the feedback amplifier. The output amplification means may be configured to change the gain of the output amplification means by selecting a resistance means used as a feedback resistor of the feedback amplifier by the switching means. Further, in this case, the switching means may be an analog switch composed of a field effect transistor. According to any one of the configurations described above, the output amplification means can be easily realized.

  In addition, separation means for separating an input signal into an I signal and a Q signal is provided, and the output amplification means amplifies the I signal amplified by the separation means, and amplifies the Q signal. It is good also as a structure provided with Q signal amplification means. Here, the I signal is a signal when the signal input to the receiving device is separated into I-axis (In-phase axis, real axis) data and Q-axis (Quadrature axis, imaginary axis) data by the separation unit. It is a signal of I axis data. The Q signal is a Q-axis data signal in this case.

  According to the above configuration, when a required output C / N is different in a receiving device that separates an input signal into I-axis data and Q-axis data, such as a receiving device for digital satellite broadcast reception, Alternatively, when the required output C / N changes, it is possible to perform reception according to each application by the same receiving apparatus.

  Each of the receiving devices described above may be formed on a semiconductor integrated circuit. According to the above configuration, even when the required output C / N is different or the required output C / N changes, the semiconductor integrated circuit individually designed for each application can be provided. There is no need to use it, and reception can be appropriately performed using the same semiconductor integrated circuit.

  In order to solve the above problems, a control method for a receiving apparatus of the present invention includes a first amplifying unit that amplifies an input signal, a frequency converting unit that converts a frequency of an output signal of the first amplifying unit, A control method for a receiving apparatus comprising output amplification means for amplifying and outputting the signal after frequency conversion, wherein an output signal set in accordance with the signal level of the signal input to the first amplification means The gain of the first amplifying means and the output amplifying means is controlled so that the level can be satisfied and the gain of the output amplifying means is as small as possible.

  According to the above control method, the output C / N characteristic can be switched according to the output signal level required of the receiving apparatus. That is, the output C / N characteristic can be switched according to the use of the receiving apparatus. Therefore, even when the required output C / N is different (or changes), it is not necessary to use a receiving device designed individually for each application, and reception is appropriately performed using the same receiving device. be able to.

  In general, the output noise level in the receiving apparatus configured as described above depends more on the output amplifying means than on the first amplifying means. For this reason, the output C / N characteristic can be improved by reducing the gain of the output amplifying means as much as possible within a range in which the set output signal level can be satisfied.

  As described above, in the receiving apparatus of the present invention, the gain of the output amplification means is variable. Therefore, even when the required output C / N is different or when the required output C / N changes, it is not necessary to use a receiving device designed individually for each application, and the same reception is possible. It can be appropriately received using the device.

  The control method of the receiving apparatus of the present invention can satisfy the set output signal level according to the signal level of the signal input to the first amplifying means, and the gain of the output amplifying means is as small as possible. Thus, the gains of the first amplifying means and the output amplifying means are controlled.

  Therefore, even when the required output C / N is different (or changes), it is not necessary to use a receiving device designed individually for each application, and reception is appropriately performed using the same receiving device. can do. Further, the output C / N characteristic can be improved by reducing the gain of the output amplifying means as much as possible within a range in which the set output signal level can be satisfied.

  An embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit block diagram showing a configuration of a digital satellite broadcast receiver 1 which is a receiver according to the present embodiment. As shown in this figure, a receiving device (digital satellite broadcast receiving device) 1 includes a high frequency signal input terminal 11, a high frequency amplifier 12, a gain control terminal (high frequency amplifier gain control terminal) 13, a mixer circuit 14, and oscillation circuits 15, 90. A phase shift circuit 16, a low frequency amplifier 17, a gain control terminal (low frequency amplifier gain control terminal) 18, a filter circuit 19, an output amplifier 20, and an output terminal 21 are provided. Note that each circuit in the receiving apparatus 1 is formed on a semiconductor integrated circuit.

  In addition, the receiving device 1 includes two mixer circuits, a low-frequency amplifier, a filter circuit, an output amplifier, and an output terminal for each of I-axis data (I signal) and Q-axis data (Q signal). Each of these two circuits performs substantially the same processing for the I-axis data and the Q-axis data. For this reason, in the following description, for convenience of explanation, the common reference numerals are used for both of the two circuits, and the processing of both data will be described in common. That is, as shown in FIG. 1, each two mixer circuits, low frequency amplifiers, filter circuits, output amplifiers, and output terminals are connected to mixer circuit 14, low frequency amplifier 17, filter circuit 19, output amplifier 20, and output terminals, respectively. The processing of both data will be described in common.

  A high frequency signal received from the outside of the receiving device 1 is input to the high frequency signal input terminal 11. The high frequency amplifier 12 is a variable gain high frequency amplifier that amplifies a high frequency signal input via the high frequency signal input terminal 11. The gain of the high frequency amplifier 12 is controlled by a control signal input from a high frequency amplifier control circuit (not shown) via the gain control terminal 13.

  The oscillation circuit 15 generates an oscillation signal and supplies it to the 90-degree phase shift circuit 16. The 90-degree phase shift circuit 16 generates two local signals having a phase difference of 90 degrees from the oscillation signal supplied from the oscillation circuit 15, and supplies them to the two mixer circuits 14, respectively.

  The mixer circuit 14 performs I / Q separation (Hilbert transform) and frequency conversion on the output signal of the high-frequency amplifier 12. That is, in the receiving apparatus 1, by supplying a local signal having a phase difference of 90 degrees from the 90 degree phase shift circuit 16 to the two mixer circuits 14, I / Q separation (Hilbert transform) and frequency conversion are simultaneously performed. It is like that.

  The low frequency amplifier 17 is a variable gain low frequency amplifier that amplifies the signal output from the mixer circuit 14. A control signal for controlling the gain of the low frequency amplifier 17 is input to the gain control terminal 18 from a low frequency amplifier control circuit (not shown).

  The filter circuit 19 is a filter circuit that removes unnecessary frequency components contained in the output signal of the low-frequency amplifier 17. The output amplifier 20 amplifies the output signal of the filter circuit 19 and outputs it from the output terminal 21. Note that external devices such as a display device, a sound output device, and a storage device are connected to the output terminal 21. In the receiving device 1, the signal amplified by the output amplifier 20 is passed through the output terminal 21. Output to these external devices. The output amplifier 20 is a variable gain amplifier that can switch the gain stepwise.

  Next, the operation of the receiving device 1 will be described. FIG. 2 is a graph (level distribution diagram) showing signal levels in each part of the receiving apparatus 1. FIG. 2 shows an example when the signal level input to the high-frequency signal input terminal 11 is a certain level (predetermined value) or more. In FIG. 2, the broken line indicates the signal level of each part in the receiving apparatus 1, and the solid line indicates the case where the same input signal as that of the receiving apparatus 1 is input to the high frequency signal input terminal 101 of the conventional receiving apparatus shown in FIG. The signal level of each part is shown. FIG. 2 shows an example in which the output signal level of the output amplifier is the same as the example of the conventional receiving apparatus shown in FIG.

  In the receiving device 1, when the signal level of the input signal input to the high-frequency signal input terminal 11 is a certain level (predetermined value) or more, the gain G2 of the output amplifier 20 is set to a reference value (in the example shown in FIG. The gain of the high-frequency amplifier 12 is set to be larger than the reference value (in the example shown in FIG. 2, the gain of the high-frequency amplifier 102 in the conventional receiver). In the example shown in FIG. 2, the gain of the low frequency amplifier 17 and the gain of the conventional low frequency amplifier 107 are set to be substantially the same. That is, in the example shown in FIG. 2, the gain G2 of the output amplifier 20 is made smaller than the gain G1 of the output amplifier 110 in the conventional receiving apparatus, and the gain of the high-frequency amplifier 12 is correspondingly increased by the gain of the high-frequency amplifier 102 in the conventional receiving apparatus. By setting the gain larger than the gain, the signal level Co of the output signal from the output amplifier 20 becomes the same as the output signal level Co of the conventional receiving apparatus.

  FIG. 3 plots the input signal input to the output amplifier 20 of the receiving apparatus 1 and the output signal from the output amplifier 20 with respect to this input signal, with the horizontal axis representing frequency and the vertical axis representing signal level. It is a graph. Note that the left graph in FIG. 3 shows an input signal to the output amplifier 20, and the right graph shows an output signal from the output amplifier 20.

  As shown in this figure, the input C / N of the output amplifier 20 is represented by the ratio (Ci2 / Ni) between the input signal level Ci2 and the input noise floor level Ni. As shown in FIG. 2, the input signal level Ci2 of the output amplifier 20 is set to be higher than the input signal level Ci of the output amplifier 110 in the conventional receiving apparatus. This is because, as described above, the gain of the high-frequency amplifier 12 is set larger than the gain of the high-frequency amplifier 102 in the conventional receiving apparatus. However, since the gain G2 of the output amplifier 20 is set smaller than the gain G1 of the output amplifier 110 in the conventional receiving apparatus, the signal level Co of the output signal of the receiving apparatus 1 and the signal of the output signal in the conventional receiving apparatus It is equal to the level Co.

  The input noise floor level Ni is substantially equal to the input noise floor level Ni input to the output amplifier 110 in the conventional receiving apparatus shown in FIG. This point will be described in more detail.

  Generally, when the input signal level to the receiving device is higher than a certain level, the output noise level (output noise component) of the receiving device is not the first half of the receiving device (the high frequency amplifier 12 and the mixer circuit 14 (RF unit)), It is determined by the latter half (low frequency amplifier 17, filter circuit 19, output amplifier 20). That is, the influence on the output noise (output C / N) of each circuit block included in the receiving apparatus 1 depends not only on the performance of each circuit block but also on the gain distribution of the entire receiving apparatus 1. When the input signal level to the receiving device 1 is higher than a certain level, the output noise level of the receiving device 1 is generally determined by the low frequency amplifier 17, the filter circuit 19, and the output amplifier 20.

  In the example shown in FIG. 3, only the high-frequency amplifier 12 has changed the gain in accordance with switching the gain of the output amplifier 20, and the circuit states of the low-frequency amplifier 17 and the filter circuit 19 have not changed at all. . For this reason, even when the gain of the output amplifier 20 is switched, it can be considered that the noise component included in the input signal of the output amplifier 20 does not substantially change.

  Therefore, as shown in FIG. 3, even when the gain of the output amplifier 20 is reduced, the noise floor level Ni of the input signal to the output amplifier 20 is the case where the gain of the output amplifier 20 is not reduced, that is, in the conventional receiving apparatus. It can be regarded as the same value as the input noise floor level Ni of the output amplifier 110.

  As shown in FIG. 3, the output noise level No2 from the output amplifier 20 is a noise level obtained by multiplying the input noise floor level Ni by a gain G2. Further, the output C / N of the receiving apparatus 1 is represented by the ratio (Co / No2) between the output signal level Co and the output noise level No2. Since noise is actually added by the output amplifier 20, the amount of increase in noise between the input and output of the output amplifier 20 is slightly larger than the amount of increase corresponding to the gain G2, but in general this error is It can be ignored compared to the amount of increase in noise due to the gain G2.

  As described above, since the gain G2 of the output amplifier 20 is smaller than the gain G1 of the output amplifier 110 in the conventional receiving apparatus (G2 <G1), the output noise level No2 of the receiving apparatus 1 is as shown in FIG. The output noise level No in the conventional receiver becomes smaller (No2 <No). As is clear from comparison between FIG. 3 and FIG. 12, when the output signal level Co is the same, the gain of the output amplifier 20 is switched to be small, and the gain of the high-frequency amplifier 12 is increased, so that The output C / N (Co / No 2) can be made smaller (changed) than in the conventional receiving apparatus.

  Although it is possible to design the gain of the output amplifier 20 to be a small value from the beginning, at this time, the gain of the entire receiving apparatus 1 is lowered by that amount, and the minimum input signal level that can be received is reduced. (Minimum input signal level that can be received at a predetermined output signal level) increases.

  For this reason, it is preferable that the gain of the output amplifier 20 is designed to be switchable. Thereby, for example, an application that needs to reduce a minimum input signal level that can achieve a predetermined output signal level (a set output signal level) (an application that needs to receive an input signal with a smaller signal level) ), The gain of the output amplifier 20 is set to a high value to achieve a predetermined output signal level (set output signal level) and the output C / N must be improved. The gain of the output amplifier 20 can be changed according to the application, such as setting to improve the output C / N.

  The predetermined output signal level may be set to a constant value according to the use of the receiving device 1 or may be arbitrarily set by a user via an input unit (not shown). Also good.

  As described above, in the receiving device 1 according to the present embodiment, the variable gain amplifier capable of switching the gain is used as the output amplifier 20. Thereby, the characteristics of the receiving device 1 can be switched and used according to the output C / N required by the receiving device 1 (the total gain of the receiving device 1 and the priority of the output C / N). Therefore, even when the required output C / N is different (or changes), it is not necessary to use a receiver designed individually for each application, and the characteristics of one receiver can be switched to Can be used for applications.

  Further, as described above, the receiving device 1 according to the present embodiment is formed on a semiconductor integrated circuit. Therefore, the receiving device 1 formed on the semiconductor integrated circuit can be used for a plurality of uses, and it is not necessary to use a different semiconductor integrated circuit for each use. Accordingly, for example, a single type of semiconductor integrated circuit is also provided for a receiving device having a different output C / N, such as a receiving device for a QPSK modulated signal and a receiving device for an 8PSK modulated signal. The characteristics of the receiving device 1 formed above can be switched and used. However, the receiving device 1 of the present invention is not limited to the configuration formed on the semiconductor integrated circuit.

  In this embodiment, the output amplifier 20 that can switch the gain stepwise is used. However, the present invention is not limited to this. However, control of the gain of the output amplifier 20 is facilitated by using the output amplifier 20 that can switch the gain stepwise. For example, a register for switching the gain is provided, and the gain of the output amplifier 20 can be switched by digital control based on the set value of this register. That is, the gain of the output amplifier 20 can be easily switched based on the setting by the digital circuit using a circuit configuration in which the gain can be switched stepwise. FIG. 4 is a circuit block diagram showing the configuration of the receiving apparatus 2 as an example of the receiving apparatus of the present invention in this case.

  The receiving device 2 is formed on a semiconductor integrated circuit 24 as shown in FIG. For convenience of explanation, members having the same functions as those of the receiving apparatus 1 described above are denoted by the same reference numerals as those of the receiving apparatus 1 and description thereof is omitted.

  The receiving device 2 includes a control signal input terminal 23 and a control circuit 22 in addition to the configuration of the receiving device 1.

  A control signal for controlling the gain of the output amplifier 20 is input to the control signal input terminal 23 from the outside of the semiconductor integrated circuit 24.

  The control circuit 22 controls the gain of the output amplifier 20 based on the control signal input to the control signal input terminal 23. Note that the gain of the output amplifier 20 can be switched stepwise under the control of the control circuit 22.

  As described above, the control signal input terminal 23 to which the control signal for controlling the gain of the output amplifier 20 is input, and the control circuit 22 that switches the gain of the output amplifier 20 stepwise based on the input control signal. By providing, it is possible to realize a receiving apparatus that can easily switch the output C / N based on an external control signal. Note that the control circuit 22 shown in FIG. 4 can be realized by a register designed as a digital circuit.

  The output amplifier 20 provided in the receiving device 1 or the receiving device 2 according to the present embodiment includes a plurality of output amplifiers having different gains, and selects an output amplifier having an appropriate gain from the plurality of output amplifiers. May be used.

  FIG. 5 is a circuit block diagram showing a circuit configuration when the output amplifier 20 having such a configuration is applied to the receiving device 2 described above.

The output amplifier 20 shown in this figure includes n amplifiers of amplifiers 20 _a1 ,..., 20 _an . Then, the control circuit 22 selects an amplifier having an appropriate gain from the n amplifiers in accordance with a control signal input from the outside via the control signal input terminal 23, and outputs it to the filter circuit 19 By connecting between the terminal 21 and the terminal 21, the gain of the output amplifier 20 can be switched.

  Of the n amplifiers included in the output amplifier 20, the signal from the filter circuit 19 does not pass through the n-1 amplifiers that are not selected, so the power of these unselected amplifiers is turned off. You may do it. Thereby, the current consumption of the receiver 1 can be reduced.

  Further, the output amplifier 20 provided in the receiving device 1 or the receiving device 2 according to the present embodiment may be, for example, a combination of an operational amplifier and a plurality of resistors. FIG. 5 is a circuit block diagram showing the configuration of the output amplifier 20 in this case.

The output amplifier 20 shown in this figure includes an operational amplifier (feedback amplifier) 31, a resistor 32, a switch 33, and m resistors (feedback resistors) 34 _a1 ,..., 34 _am .

The resistors 32 and 34 _a1 ,..., 34 _am are resistors that determine the gain of the operational amplifier 31.

The switch 33 is a switch that selects a resistor used as a feedback resistor from m resistors 34 _a1 ,..., 34 _am .

The gain of the output amplifier 20 shown in FIG. 5 is determined by the ratio between the resistor 32 and the feedback resistor selected by the switch 33 (any one of the m resistors 34 _a1 ,..., 34 _am ). Is done. For this reason, the gain of the output amplifier 20 can be switched by switching the resistor used as the feedback resistor by the switch 33.

  The configuration of the switch 33 is not particularly limited. For example, an analog switch configured with a MOSFET (FET (Field Effect Transistor)) as shown in FIG. 7 can be used.

  The analog switch (switch) 33 shown in FIG. 7 includes a control signal input terminal 41, an inverter 42, an N-channel MOSFET 43, and a P-channel MOSFET 44.

  A control signal from the control circuit 22 is input to the control signal input terminal 41. The inverter 42 inverts the control signal (logic signal) input to the control signal input terminal 41 and inputs it to the gate of the P-channel MOSFET 44. Further, the control signal input to the control signal input terminal 41 is also input to the gate of the N-channel MOSFET 43.

  As a result, when a high-level control signal is input to the control signal input terminal 41, the N-channel MOSFET 43 and the P-channel MOSFET 44 are turned on, and the resistor connected to the N-channel MOSFET 43 and the P-channel MOSFET 44 is selected as a feedback resistor. Is done. On the other hand, when a low-level control signal is input to the control signal input terminal 41, the N-channel MOSFET 43 and the P-channel MOSFET 44 are turned off.

That is, the switch 33 shown in FIG. 7 is connected to each of the resistors 34 _a1 ,..., 34 _am , and the switch 33 connected to the resistor to be selected is made conductive by the control circuit 22, whereby the output amplifier 20 gains can be switched.

  In this embodiment, an example in which the gain of the output amplifier 20 is made smaller than a reference value (in the above example, the gain of the output amplifier 110 in the conventional receiving apparatus) has been described, but the present invention is not limited to this. The gain of the output amplifier 20 may be set as appropriate according to the application of the receiving apparatus 1 and may be configured to be larger than that of the conventional receiving apparatus.

  In the present embodiment, an example in which the gain of the output amplifier 20 is decreased, the gain of the high-frequency amplifier 12 is increased, the gain of the low-frequency amplifier 17 is not changed, and the gain of the output amplifier 20 is decreased. However, it is not limited to this. For example, when it is necessary to realize the set output signal level, not only the gain of the high-frequency amplifier 12 but also the gain of the low-frequency amplifier 17 and / or the output amplifier 20 may be increased.

  That is, when the signal level of the high-frequency signal input to the high-frequency signal input terminal 11 is small (less than a predetermined value), it is necessary to increase the gain of the entire receiving device 1 to improve the reception sensitivity. The gains of the high-frequency amplifier 12, the low-frequency amplifier 17, and the output amplifier 20 may be set high. Further, when the input signal level is not small (when it is greater than or equal to a predetermined value), the output C / N is improved by setting the gains of the output amplifier 20 and the low frequency amplifier 17 low, and the reception performance is improved. May be.

  However, as described above, generally, when the input signal level to the receiving device is higher than a certain level, the output noise component of the receiving device is not the first half of the receiving device (for example, the high-frequency amplifier 12 and the mixer circuit 14), but the second half. It is determined by the part (for example, the low frequency amplifier 17, the filter circuit 19, and the output amplifier 20).

  For this reason, when the input signal level to the receiving apparatus is higher than a certain level and the required total gain (gain of the entire receiving apparatus 1) can be obtained by increasing the gain of the high-frequency amplifier 12, the high-frequency amplifier It is preferable to set the gain of 12 large and set the gains of the low frequency amplifier 17 and the output amplifier 20 as small as possible. When the total gain required cannot be obtained simply by increasing the gain of the high-frequency amplifier 12, it is preferable to increase the gain of the low-frequency amplifier 17 and / or the output amplifier 20 by a necessary amount.

  The gain of the output amplifier 20 may be controlled based on a gain control signal for controlling the gain of the high-frequency amplifier 12 and / or the low-frequency amplifier 17 supplied from the outside. For example, a high-frequency amplifier control circuit (gain control signal generator) for controlling the gain of the high-frequency amplifier 12 based on a gain control signal supplied from outside, and a gain control signal supplied from the outside for the gain of the low-frequency amplifier 17 And a low-frequency amplifier control circuit (gain control signal generator) for controlling the gain of the output amplifier 20 based on the gain control signals of the high-frequency amplifier 12 and the low-frequency amplifier 17 input from the outside. You may do it.

  FIG. 8 is a circuit block diagram showing the configuration of the receiving apparatus 3 as an example of the receiving apparatus of the present invention in this case.

  As shown in FIG. 8, the receiving device 3 is formed on a semiconductor integrated circuit 24b. For convenience of explanation, members having the same functions as those of the receiving apparatuses 1 and 2 described above are denoted by the same reference numerals as those of the receiving apparatuses 1 and 2, and description thereof is omitted.

  The receiving device 3 includes a gain control signal generation circuit 51 in addition to the configuration of the receiving device 1. The gain control signal generating circuit 51 is supplied with the gain control signal of the high frequency amplifier 12 and the gain control signal of the low frequency amplifier 17 input to the gain control terminal 13 and the gain control terminal 18.

  Further, the gain control signal generation circuit 51 generates a gain control signal for the output amplifier 20 based on the gain control signal for the low-frequency amplifier 17 and controls the gain of the output amplifier 20.

  When the input signal level is low (less than a predetermined value), gain control signals that set the gains of the high frequency amplifier 12 and the low frequency amplifier 17 high are input to the gain control terminal 13 and the gain control terminal 18. When the input signal level is not small (when it is greater than or equal to a predetermined value), there is a gain control signal that increases the gain of the high-frequency amplifier 12 and sets the gain of the low-frequency amplifier 17 low (or does not change it). The signals are input to the gain control terminal 13 and the gain control terminal 18.

  Thereby, the gain control signal generation circuit 51 sets the gain of the output amplifier 20 high based on the gain control signal of the low frequency amplifier 17, for example, when the input signal level is small (less than a predetermined value). When the gain of the entire receiving apparatus 1 is increased and the input signal level is not small (in the case of a predetermined value or more), the gain of the output amplifier 20 is set low to improve the output C / N and improve the reception performance. Can be improved.

  In the configuration of FIG. 8, the gain control signals of the high-frequency amplifier 12 and the low-frequency amplifier 17 are input from the outside of the semiconductor integrated circuit 24b. However, the present invention is not limited to this, and the high-frequency amplifier 12 and the low-frequency amplifier 17 Gain control means for generating a gain control signal may be provided on the semiconductor integrated circuit 24b.

  Moreover, it is good also as a structure which controls the gain of the high frequency amplifier 12, the low frequency amplifier 17, and the output amplifier 20 based on the gain control signal supplied from the outside. For example, a signal corresponding to a required output signal level is input as a gain control signal, and a gain control signal generation circuit that sets the optimum gains of the high frequency amplifier 12, the low frequency amplifier 17, and the output amplifier 20 based on the signal. May be provided.

  FIG. 9 is a circuit block diagram showing the configuration of the receiving device 4 as an example of the receiving device of the present invention in this case. As shown in FIG. 9, the receiving device 4 is formed on a semiconductor integrated circuit 24c. For convenience of explanation, members having the same functions as those of the receiving apparatuses 1 to 3 are denoted by the same reference numerals as those of the receiving apparatuses 1 to 3, and the description thereof is omitted.

  The reception device 4 includes a gain control signal generation circuit 52 in addition to the configuration of the reception device 1. The gain control signal generation circuit 52 receives a signal corresponding to the output signal level required of the receiving device 4 from an external circuit (not shown) via the control signal input terminal 23b.

  Then, the gain control signal generation circuit 52 sets the gains of the high-frequency amplifier 12, the low-frequency amplifier 17, and the output amplifier 20 according to the input signal to the output signal level (set by the receiver 4). The output signal level is realized and the output C / N is optimized. Specifically, the gain control signal generation circuit 52 can satisfy the set output signal level according to the input signal, and the gains of the output amplifier 20 and the low-frequency amplifier 17 are as small as possible. In this manner, the gains of the high frequency amplifier 12, the low frequency amplifier 17, and the output amplifier 20 are controlled.

  Based on the gains of the high-frequency amplifier 12, the low-frequency amplifier 17, and the output amplifier 20 set as described above, a control signal for each amplifier is generated, and the gain of each amplifier is controlled.

  Thereby, the set output signal level can be achieved, and the output C / N characteristic can be improved.

  In the present embodiment, the configuration including the low-frequency amplifier 17 has been described. However, the configuration is not limited thereto, and a configuration without the low-frequency amplifier 17 may be employed.

  Moreover, although this embodiment demonstrated the case where this invention was applied to a digital satellite broadcast receiver, the receiver which can apply this invention is not restricted to this. The present invention can be applied to any receiving apparatus having a configuration (gain distribution) in which the output C / N of the receiving apparatus changes by changing the gain of the output amplifier.

  ADVANTAGE OF THE INVENTION According to this invention, the receiver which can respond by changing a setting according to the request | requirement of output C / N and a maximum gain is realizable. In particular, when the present invention is used in a semiconductor integrated circuit, it is possible to meet the demands for output C / N and maximum gain based on an external signal, so that one type of semiconductor integrated circuit is used for general purposes. Can do.

  The present invention can be implemented in various other forms without departing from the main features described above. Therefore, the above-mentioned embodiment is only a mere illustration in all points, and should not be interpreted limitedly. The scope of the present invention is indicated by the claims, and is not restricted by the text of the specification. Further, all modifications, changes and processes belonging to the equivalent scope of the claims are within the scope of the present invention.

  Since the receiving apparatus of the present invention can arbitrarily switch the output C / N characteristic by switching the gain of the output amplifier, the receiving apparatus in which the output C / N of the receiving apparatus changes by changing the gain of the output amplifier. If applicable. The receiving apparatus of the present invention is particularly suitable for a receiving apparatus for digital satellite broadcasting, for example, because a single receiving apparatus can be used for a plurality of uses having different required output C / N. .

It is a block diagram which shows one structural example of the receiver concerning one Embodiment of this invention. It is a graph which shows the gain distribution with respect to each circuit block in the receiver concerning one Embodiment of this invention, and the conventional receiver. It is a graph which shows the input signal and output signal of an output amplifier in the receiver concerning one embodiment of the present invention. It is a block diagram which shows the other structural example of the receiver concerning one Embodiment of this invention. It is a block diagram which shows one structural example of the output amplifier with which the receiver concerning one Embodiment of this invention is equipped. It is a block diagram which shows the other structural example of the output amplifier with which the receiver concerning one Embodiment of this invention is equipped. FIG. 7 is a block diagram illustrating a configuration example of a switch provided in the output amplifier illustrated in FIG. 6. It is a block diagram which shows the further another structural example of the receiver concerning one Embodiment of this invention. It is a block diagram which shows the further another structural example of the receiver concerning one Embodiment of this invention. It is a block diagram which shows the structure of the conventional receiver. It is a graph which shows gain distribution with respect to each circuit block in the conventional receiver. It is a graph which shows the input signal and output signal of the output amplifier in the conventional receiver.

Explanation of symbols

1, 2, 3, 4 Receiver 11 High-frequency signal input terminal 12 High-frequency amplifier (first amplification means)
13 Gain control terminal 14 Mixer circuit 15 Oscillation circuit 16 degree phase shift circuit 17 Low frequency amplifier (second amplification means)
18 Gain control terminal 19 Filter circuit (unnecessary component removing means)
20 Output amplifier (output amplification means)
20a1, ..., 20an amplifier (amplifying means)
21 output terminal 22 control circuit (control means)
23, 23b Control signal input terminals 24, 24b, 24c Semiconductor integrated circuit 31 Operational amplifier (feedback amplifier)
32 resistor 33 switch (switching means)
34a1,..., 34am resistance (feedback resistance)
41 control signal input terminal 42 inverter 51 gain control signal generation circuit (fourth control means)
52 Gain control signal generation circuit (second control means, third control means)

Claims (18)

First amplification means for amplifying an input signal, frequency conversion means for converting the frequency of an output signal of the first amplification means, and output amplification means for amplifying and outputting the signal after frequency conversion A receiving device,
A receiving apparatus characterized in that the gain of the output amplifying means is variable. A second amplifying means for amplifying the signal after the frequency conversion;
The receiving apparatus according to claim 1, wherein the output amplifying unit amplifies and outputs the signal amplified by the second amplifying unit. An unnecessary component removing means for removing an unnecessary frequency component included in the signal after the frequency conversion,
The receiving apparatus according to claim 1, wherein the output amplifying unit amplifies and outputs the signal after the unnecessary frequency component is removed by the unnecessary component removing unit.   2. The receiving apparatus according to claim 1, further comprising control means for controlling the gain of the output amplifying means in accordance with a set output signal level. The control means includes
5. The receiving apparatus according to claim 4, wherein a gain of the output amplifying unit is controlled in accordance with a signal level of a signal input to the first amplifying unit. The first amplifying means is a gain variable amplifying means,
In accordance with the signal level of the signal input to the first amplifying unit, the first amplifying unit and the first amplifying unit and the output amplifying unit can be set as small as possible so that the set output signal level can be satisfied. The receiving apparatus according to claim 1, further comprising second control means for controlling a gain of the output amplifying means. The first amplification means and the second amplification means are variable gain amplification means,
According to the signal level of the signal input to the first amplifying means, the set output signal level can be satisfied, and the gains of the output amplifying means and the second amplifying means are as small as possible. The receiving apparatus according to claim 2, further comprising third control means for controlling gains of the first amplifying means, the second amplifying means, and the output amplifying means. The first amplification means and the second amplification means are variable gain amplification means,
4. A fourth control means for controlling the gain of the output amplifying means based on a set output signal level and the gains of the first amplifying means and the second amplifying means. The receiving device described in 1.   The receiving apparatus according to claim 1, wherein the output amplifying means switches the gain stepwise. Control means for controlling the gain of the output amplification means,
The receiving apparatus according to claim 9, wherein the control means switches the gain of the output amplifying means stepwise by changing a setting value of a register provided in the control means.   The output amplifying means includes a plurality of amplifying means having different gains, and the gain is changed by selecting one of the amplifying means from the plurality of amplifying means. The receiving device described.   12. The receiving apparatus according to claim 11, wherein the output amplifying means turns off power of an amplifying means that is not selected among the plurality of amplifying means. The output amplification means includes
The receiving apparatus according to claim 1, comprising a feedback amplifier and resistance changing means for changing a feedback resistance value of the feedback amplifier. The resistance variable means is
A plurality of resistance means having different resistance values arranged in parallel with the feedback amplifier;
It is arranged in series with each of the resistance means, and comprises switching means for switching the resistance means used as the feedback resistance of the feedback amplifier,
14. The receiving apparatus according to claim 13, wherein the output amplifying means changes a gain of the output amplifying means by selecting a resistance means used as a feedback resistor of the feedback amplifier by the switching means.   15. The receiving apparatus according to claim 14, wherein the switching means is an analog switch composed of a field effect transistor. Separating means for separating the input signal into an I signal and a Q signal;
2. The reception according to claim 1, wherein the output amplification means includes I signal amplification means for amplifying the I signal separated by the separation means, and Q signal amplification means for amplifying the Q signal. apparatus.   The receiving apparatus according to claim 1, wherein the receiving apparatus is formed on a semiconductor integrated circuit. First amplification means for amplifying an input signal, frequency conversion means for converting the frequency of an output signal of the first amplification means, and output amplification means for amplifying and outputting the signal after frequency conversion A control method of a receiving device,
In accordance with the signal level of the signal input to the first amplifying unit, the first amplifying unit and the first amplifying unit and the output amplifying unit can be set as small as possible so that the set output signal level can be satisfied. A control method for a receiving apparatus, wherein the gain of the output amplifying means is controlled.

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