JP2007158812A - Digital television broadcasting repeater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct frequency characteristics in a digital television broadcasting repeater arbitrarily in a digital television broadcasting repeater. <P>SOLUTION: An IF stage of transmission conversion units 15a and 15b is provided with a frequency characteristic correction circuit 86. The frequency characteristic correction circuit 86 comprises pass (PASS) circuits 91a to 91d for making, for example, a signal pass, attenuators (ATT) 92a to 92d of 1dB, 2dB, 4, dB and 8dB, building out networks (BON) 93a and 93b of 0. 5dB and 1dB, and equalizers (EQ) 94a and 94b of 0. 5dB and 1dB and is configured to be able to correct a frequency characteristic by switching the pass circuits 91a to 91d, the attenuators 92a to 92d, the building out networks 93a and 93b and the equalizers 94a and 94b arbitrarily by switches. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a digital television broadcast relay device that relays terrestrial digital television broadcasts.

  In digital terrestrial television broadcasting, for example, radio waves having a high frequency such as UHF are used. High-frequency radio waves such as UHF are hardly diffracted, and if there are obstacles such as buildings and mountains, the radio waves are blocked, resulting in an area where it is difficult to receive radio waves in a part of the service area.

In order to eliminate such difficult viewing areas or to deliver broadcast radio waves to distant areas, a TV broadcast relay device is installed on the rooftop of the building, the top of the mountain, etc., and the radio waves from the transmitting station are received by the receiving antenna, After amplification, the signal is retransmitted to the difficult viewing area or the next relay station by the transmission antenna (see, for example, Patent Document 1).
JP 2000-151552 A

  In the digital television broadcast relay apparatus, a deviation (inclination) within a band is defined for each unit. In the digital television broadcast relay apparatus, the standard specification stipulates that the deviation of each unit be within 1.5 dBp-p at fc (carrier frequency) ± 2.79 MHz.

  Conventionally, each unit is generally manufactured so as to satisfy the conditions stipulated in the above standard specifications, and no frequency characteristic correcting means is provided.

  Even when manufactured so that the deviation of each unit is within a specified value as in the conventional case, the deviation may be larger than the specified value depending on the combination of units. However, since the conventional digital television broadcast relay apparatus does not include a frequency characteristic correction means, if the deviation becomes larger than a specified value due to the combination of units, a circuit is provided so as to satisfy the specified condition. It is difficult to adjust.

  The present invention has been made to solve the above-described problem, and even when the unit is combined, even when the deviation becomes larger than the specified value, the digital television broadcast relay apparatus can correct the deviation to be within the specified value. The purpose is to provide.

  A first invention receives a digital television broadcast for each channel, amplifies it by a high frequency amplifier, and converts it to an intermediate frequency signal by a frequency converter, and an intermediate frequency signal converted by the reception converter unit In a digital television broadcast relay apparatus comprising a transmission conversion unit that amplifies the signal by an intermediate frequency amplification unit, converts the signal to a high frequency signal by a frequency conversion unit, and outputs the signal, the reception conversion unit and the transmission conversion unit each amplify the signal A gain control circuit that adjusts the gain of the signal, a signal level detection unit that detects the level of the signal amplified by the amplification unit, and the gain control circuit that is controlled based on the signal level detected by the signal level detection unit And a microcomputer for keeping the signal level constant.

  According to a second aspect of the present invention, in the digital television broadcast relay device according to the first aspect of the present invention, the reception conversion unit is provided with a gain control circuit in a high frequency unit for amplifying a high frequency signal and an intermediate frequency unit for amplifying the intermediate frequency signal, In the range where the input of the high frequency signal is lower than the preset level, the signal level is controlled by controlling the gain control circuit of the intermediate frequency unit, and in the range where the input of the high frequency signal is higher than the preset level, the high frequency amplification unit and the intermediate frequency are controlled. The signal level is controlled by controlling both of the gain control circuits.

  According to a third aspect of the present invention, in the digital television broadcast relay apparatus according to the first or second aspect of the present invention, frequency characteristic correction comprising at least a pseudo-line network and an equalizer in either one or both of the reception conversion unit and the transmission conversion unit. A circuit is provided.

  According to the present invention, a wide AGC range can be precisely controlled by mounting the gain control circuit divided into the RF stage and the IF stage and performing AGC control according to the input level of the RF signal by the microcomputer. In addition, it is possible to reliably suppress deterioration of noise figure and intermodulation distortion. Further, by providing a gain control circuit after the AGC loop and setting the AGC level with a variable resistor, the AGC control can be finely adjusted.

  In addition, since the frequency characteristic correction circuit is configured by the path circuit, the attenuator, the pseudo line network, and the equalizer, and each element can be arbitrarily switched and connected by the switch, the frequency characteristic of the circuit can be arbitrarily corrected. Therefore, even when the frequency deviation becomes larger than the specified value due to the combination of the plurality of units, the frequency characteristic correction circuit can adjust the deviation to be within the specified value.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration for one channel of a digital television broadcast relay apparatus according to an embodiment of the present invention. In the entire digital television broadcast relay apparatus, the circuit shown in FIG. 1 is provided for n channels.

  In FIG. 1, reference numerals 11a and 11b denote RF input terminals to which television broadcast waves received by a receiving antenna (not shown) are input. One of the RF input terminals 11a and 11b is an active system and the other is a standby system. The reception signals input to the RF input terminals 11a and 11b are sent to the transmission / reception unit 13 via the input filters 12a and 12b, respectively. The input filter 12 selects and outputs an arbitrary channel (band 6 MHz) in the UHF-TV band of terrestrial digital television broadcasting, for example, 470 MHz to 770 MHz.

  The transmission / reception unit 13 includes reception conversion units 14a and 14b and transmission conversion units 15a and 15b. The reception conversion units 14a and 14b receive television broadcast waves of preset channels, and convert the RF signals (high frequency signals) selected by the input filters 12a and 12b into IF signals (intermediate frequency signals). Amplified and output to the transmission conversion units 15a and 15b, respectively. The transmission conversion units 15a and 15b correct the frequency characteristics of the IF signals transmitted from the reception conversion units 14a and 14b, convert them to RF signals, for example, the RF frequency of the original channel, and amplify and output the signals.

  The RF signals of the specific channels output from the transmission conversion units 15a and 15b are amplified by the power amplifiers 16a and 16b, respectively, and then one signal is selected by the switch 17, and the RF output terminal via the output filter 18 is selected. 19 is sent. One of the two signal systems is used as an active system and the other is used as a standby system, and is switched by a switch 17. The switcher 17 switches to the standby system when a failure or the like occurs in the active system. The output signal of the power amplifier 16a or the power amplifier 16b selected by the switcher 17 is sent to the RF output terminal 19 via the output filter 18.

  The RF signal output from the RF output terminal 19 for each channel is sent to a transmission antenna via a duplexer (not shown), and transmitted to the next television relay station or the like.

  Next, detailed configurations of the reception conversion units 14a and 14b and the transmission conversion units 15a and 15b provided in the transmission / reception unit 13 will be described.

[Configuration of receiving conversion unit]
First, the detailed configuration of the reception conversion units 14a and 14b will be described with reference to FIGS. The reception conversion units 14a and 14b have the same configuration.

FIG. 2 is a block diagram showing the configuration of the main part of the reception conversion unit 14a (14b), and FIG. 3 is a block diagram showing the configuration of other parts.
In FIG. 2, reference numeral 21 denotes an RF input terminal to which a TV signal of a predetermined channel selected by the input filter 12 of FIG. 1 is input. The signal input to the RF input terminal 21 is an RF stage including a high frequency amplifier 22, a branch circuit 23, a first gain control circuit (GC) 24, a high frequency amplifier 25, a second gain control circuit (GC) 26, and an equalizer 27. Is input to one input terminal of the mixer 28.

  The RF signal amplified by the high frequency amplifier 22 is branched by a predetermined level attenuation by the branch circuit 23, amplified by the amplifier 30, and input to the signal level detection unit 31. The amplifier 30 amplifies the signal branched by the branch circuit 23 to a level substantially equal to the output signal level of the high-frequency amplifier 22. The signal level detection unit 31 is configured by, for example, an amplitude detection circuit and a logarithmic amplifier. The amplitude detection circuit detects the RF signal input from the branch circuit 23 via the amplifier 30, converts the amplitude level of the RF signal into a DC level, and outputs the DC level. The logarithmic amplifier performs logarithmic processing on the DC level signal output from the amplitude detection circuit so that the input level and the output level can be expressed in a linear relationship.

  As described above, the signal level detector 31 detects the output signal level of the high-frequency amplifier 22, converts it to a DC voltage, and outputs it. The signal level detected by the signal level detector 31 is sent to a microcomputer (hereinafter abbreviated as a microcomputer) 32.

  The first gain control circuit 24 is composed of, for example, a pin diode, and an AGC control signal output from the microcomputer 32 is input via a DC amplifier 33 and a driver (DRV) 34. Similarly to the first gain control circuit 24, the second gain control circuit 26 includes a pin diode, and an AGC control signal output from the microcomputer 32 is input via a DC amplifier 35 and a driver (DRV) 36. . That is, the first and second gain control circuits 24 and 26 have their attenuation adjusted by the AGC control signal output from the microcomputer 32, and hold the RF stage output signal, that is, the RF signal input to the mixer 28, constant. To do. The equalizer 27 corrects the frequency characteristics of a predetermined channel in the RF stage.

  A local oscillation signal output from the local oscillation circuit 38 is input to the other input terminal of the mixer 28 via an attenuator 39. The local oscillation circuit 38 includes, for example, a PLL (Phase-Locked Loop) circuit 381, a crystal oscillation element 382, a digital signal generator 383, and a voltage controlled oscillator (VCO) 384, and a control unit (not shown). Based on, for example, a 10 MHz reference signal input to the input terminal 37, a local oscillation signal having a predetermined frequency is output for each channel.

  The mixer 28 corrects the frequency characteristics by the equalizer 27, mixes the RF signal and the local oscillation signal sent from the local oscillation circuit 38, and converts the mixed signal into an IF signal of 37.15 MHz. The IF signal frequency-converted by the mixer 28 is output via a low-pass filter (LPF) 41, an intermediate frequency amplifier 42, a third gain control circuit (GC) 43, and intermediate frequency amplifiers 44 and 45. The third gain control circuit 43 is composed of, for example, a pin diode, and an AGC control signal output from the microcomputer 32 is input via a DC amplifier 46 and a driver (DRV) 47. In addition, an amplifier on / off signal is input from the microcomputer 32 to the intermediate frequency amplifiers 42, 44, and 45 via a driver (DRV) 48. The microcomputer 32 monitors the presence / absence of a reception signal from the signal level detected by the signal level detection unit 31, and when there is no reception signal or when the reception signal is lower than a preset level, the intermediate frequency amplifiers 42, 44. , 45 is turned off.

  The IF signal output from the intermediate frequency amplifier 45 is, as shown in FIG. 3, a SAW filter (Surface Acoustic Wave filter) 50, intermediate frequency amplifiers 51 and 52, a branch circuit 53, a low-pass filter (LPF) 54, a first filter. The signal is sent to the IF output terminal 59 via the 4-gain control circuit (GC) 55, the intermediate frequency amplifier 56, and the branch circuits 57 and 58.

  The SAW filter 50 passes an intermediate frequency signal of 37.15 ± 2.79 MHz. The intermediate frequency amplifiers 51 and 52 are on / off controlled in the same manner as the intermediate frequency amplifiers 42, 44 and 45 by an amplifier on / off signal given from the microcomputer 32 via the driver (DRV) 61.

  A part of the IF signal output from the intermediate frequency amplifier 52 is branched by the branch circuit 53 and input to the AGC detector 63 via the amplifier 62 to be detected. The signal detected by the AGC detector 63 is amplified by the DC amplifier 64 and sent to the microcomputer 32. The microcomputer 32 outputs an AGC control signal based on the AGC detection output input from the AGC detector 63 via the DC amplifier 64, and includes first and second gain control circuits 24, 26 provided in the RF stage. The AGC control operation is executed by adjusting the attenuation amount of the third gain control circuit 43 provided in the IF stage.

  In this case, when the input level of the RF signal is low, the microcomputer 32 holds the AGC control signal for the first and second gain control circuits 24 and 26 in the RF stage constant, and the third gain control circuit 43 in the IF stage. In contrast, the AGC control signal is changed based on the AGC detection output from the DC amplifier 64, and the output signal level is kept constant. When the input level of the RF signal is high, both the first and second gain control circuits 24 and 26 in the RF stage and the third gain control circuit 43 in the IF stage are controlled to keep the output signal level constant.

  The fourth gain control circuit 55 provided after the AGC loop is supplied with an output level control signal set by the AGC adjusting variable resistor 65 via a DC amplifier 66 and a driver (DRV) 67. . The fourth gain control circuit 55 outputs an IF signal having a predetermined level based on the output level control signal. As described above, the variable resistor 65 sets the AGC level after the AGC loop.

  The output level control signal adjusted by the variable resistor 65 is sent to the microcomputer 32 and monitored. Further, the intermediate frequency amplifier 56 is supplied with an amplifier on / off signal from the microcomputer 32 via a driver (DRV) 68 and is controlled to be turned on / off in the same manner as the intermediate frequency amplifiers 42, 44 and 45.

A part of the IF signal amplified by the intermediate frequency amplifier 56 is branched by the branch circuit 57 and input to the signal level detector 69. This signal level detection unit 69 has the same configuration as the signal level detection unit 31, detects the output signal level of the intermediate frequency amplifier 56, converts it to a DC voltage, and outputs it. The signal level detected by the signal level detector 69 is amplified by the DC amplifier 70 and sent to the microcomputer 32. The microcomputer 32 monitors the IF output signal level based on the signal detected by the signal level detector 69.
The IF signal output from the intermediate frequency amplifier 56 is partly branched by the branch circuit 58 and sent to the IF monitor terminal 60.

[Reception Conversion Unit Operation]
In the above configuration, the RF signal input to the RF input terminal 21 is amplified by the high frequency amplifier 22 and passes through the branch circuit 23, the first gain control circuit 24, the high frequency amplifier 25, the second gain control circuit 26, and the equalizer 27. To the mixer 28.

  The mixer 28 mixes the RF signal whose frequency characteristic has been corrected by the equalizer 27 and the local oscillation signal sent from the local oscillation circuit 38 via the attenuator 39, and converts it into a 37.15 MHz IF signal. The IF signal converted by the mixer 28 is a low-pass filter 41, an intermediate frequency amplifier 42, a third gain control circuit 43, intermediate frequency amplifiers 44 and 45, a SAW filter 50, intermediate frequency amplifiers 51 and 52, a branch circuit 53, and a low-pass filter. 54, the fourth gain control circuit 55, the intermediate frequency amplifier 56, and the branch circuits 57, 58 are sent to the IF output terminal 59.

  The RF signal amplified by the high frequency amplifier 22 is partly branched by the branch circuit 23 and sent to the signal level detector 31 via the amplifier 30. The signal level detection unit 31 detects the level of the RF signal output from the high-frequency amplifier 22, converts it to a DC signal, and outputs it to the microcomputer 32. The microcomputer 32 monitors the presence / absence and signal level of the RF input signal based on the detection signal sent from the signal level detection unit 31, and is provided in the IF stage when the RF signal of the designated channel is not received. The intermediate frequency amplifiers 42, 44, 45, 51, 52, 56 are turned off, and when the RF signal of the designated channel is normally received, the intermediate frequency amplifiers 42, 44, 45, 51, 52, 56 To turn on.

  The microcomputer 32 performs AGC control based on the detection output for AGC sent from the AGC detector 63 via the DC amplifier 64. The level of the RF input signal detected by the signal level detection unit 31 is When the level is low, AGC control is performed only by the third gain control circuit 43 in the IF stage. When the level of the RF input signal is higher than a preset level, the first and second gain control circuits 24 and 26 in the RF stage are used. The AGC control is performed by both of the third gain control circuit 43 of the IF stage and the output signal level is kept constant.

  The IF signal held at a constant level by the AGC loop control is sent from the intermediate frequency amplifier 52 to the fourth gain control circuit 55 via the branch circuit 53 and the low-pass filter 54. The fourth gain control circuit 55 outputs an IF signal having a predetermined level based on the AGC output level control signal set by the variable resistor 65. The IF signal is amplified by the intermediate frequency amplifier 56 and then output from the IF output terminal 59 via the branch circuits 57 and 58.

  As shown in the above embodiment, the gain control circuit is divided into the RF stage and the IF stage and mounted, and the AGC control is performed by the microcomputer 32 according to the input level of the RF signal, thereby controlling a wide AGC range. it can.

  According to the standard specification, the AGC response range in the reception conversion units 14a and 14b is defined such that the IF output is −10 dBm ± 3 dB or less with respect to the fluctuation of the UHF input −80 to −27 dBm. By dividing the control circuit into the RF stage and the IF stage and mounting, the AGC response range defined in the standard specification can be sufficiently satisfied. Further, by controlling the gain control circuit with the microcomputer 32, the control range of AGC can be set finely. However, since the microcomputer 32 recognizes the AGC detection voltage bit, fine adjustment of the AGC output level is difficult. Therefore, the setting of the AGC level can be finely adjusted by mounting the AGC adjusting variable resistor 65.

[Configuration of transmission conversion unit]
Next, the detailed configuration of the transmission conversion units 15a and 15b will be described with reference to FIGS. The transmission conversion units 15a and 15b have the same configuration.

FIG. 4 is a block diagram showing the configuration of the main part of the transmission conversion unit 15a (15b), and FIG. 5 is a block diagram showing the configuration of other parts.
In FIG. 4, reference numeral 81 denotes an input terminal to which an IF signal of a predetermined channel output from the reception conversion unit 14a (14b) is input. The IF signal input to the IF input terminal 81 passes through an IF stage including a branch circuit 82, an intermediate frequency amplifier 83, a low pass filter (LPF) 84, a first gain control circuit (GC) 85, and a frequency characteristic correction circuit 86. Is input to one input terminal of the mixer 87.

  The frequency characteristic correction circuit 86 includes, for example, path (PASS) circuits 91a to 91d that allow signals to pass through, 1 dB, 2 dB, 4 dB, and 8 dB attenuators (ATT) 92 a to 92 d, and 0.5 dB and 1 dB pseudo-line networks ( BON (Building Out Network) 93a, 93b and 0.5 dB, 1 dB equalizers (EQ) 94a, 94b. The path circuits 91a-91d, attenuators 92a-92d, pseudo-line networks 93a, 93b, equalizer 94a 94b can be arbitrarily switched by a switch (not shown) to correct the frequency characteristics.

  The IF signal input to the IF input terminal 81 is branched by the branch circuit 82 and input to the signal level detection unit 101. The signal level detection unit 101 includes, for example, an amplitude detection circuit and a logarithmic amplifier. The amplitude detection circuit amplitude-detects the IF signal branched by the branch circuit 82, converts the amplitude level of the IF signal to a DC level, and outputs the DC level. The logarithmic amplifier performs logarithmic processing on the DC level signal output from the amplitude detection circuit so that the input level and the output level can be expressed in a linear relationship.

  As described above, the signal level detection unit 101 detects the level of the IF signal sent from the preceding circuit, converts it to a DC voltage, and outputs it. The signal level detected by the signal level detection unit 101 is sent to a microcomputer (hereinafter simply referred to as a microcomputer) 102.

  The first gain control circuit 85 is configured by, for example, a pin diode, and an AGC control signal output from the microcomputer 102 is input via the DC amplifier 103 and the driver 104. That is, the first gain control circuit 85 adjusts the gain by the AGC control signal output from the microcomputer 102 and holds the IF signal output from the frequency characteristic correction circuit 86 constant.

  A local oscillation signal output from the local oscillation circuit 106 is input to the other input terminal of the mixer 87 via the attenuator 107. The local oscillation circuit 106 includes, for example, a PLL (Phase-Locked Loop) circuit 1061, a crystal oscillation element 1062, a digital signal generator 1063, and a voltage controlled oscillator (VCO) 1064, and a control unit (not shown). Based on, for example, a 10 MHz reference signal input to the input terminal 105, a local oscillation signal having a predetermined frequency is output for each channel.

  The mixer 87 mixes the RF signal and the local oscillation signal sent from the local oscillation circuit 106 with the frequency characteristic corrected by the frequency characteristic correction circuit 86, and converts the 37.15 MHz IF signal into the RF signal of the original channel. Convert. The RF signal frequency-converted by the mixer 28 is taken out through a low pass filter (LPF) 110.

  The RF signal output from the low-pass filter 110 is, as shown in FIG. 5, a high-frequency amplifier 111, a channel / band-pass filter (CH.BPF) 112, a high-frequency amplifier 113, a branch circuit 114, and a second gain control circuit 115. The signal is sent to the RF output terminal 119 via the high-frequency amplifier 116 and the branch circuits 117 and 118. The signal branched by the branch circuit 118 is sent to the RF monitor terminal 120.

  The high frequency amplifiers 111, 113, and 116 receive amplifier on / off signals from the microcomputer 102 through drivers 121, 122, and 123, respectively. The microcomputer 102 monitors the presence or absence of a reception signal from the signal level detected by the signal level detection unit 101. When there is no reception signal or when the reception signal is lower than a preset level, the high-frequency amplifiers 111 and 113, 116 is turned off.

  Further, a part of the RF signal output from the high-frequency amplifier 113 is branched by the branch circuit 114 and is input to the AGC detector 126 through the amplifier 125 and detected. The signal detected by the AGC detector 126 is amplified by the DC amplifier 127 and sent to the microcomputer 102. The microcomputer 102 outputs an AGC control signal based on the AGC detection output input from the AGC detector 126 via the DC amplifier 127, adjusts the gain of the first gain control circuit 85 provided in the IF stage, and Holds the output signal level constant.

  The second gain control circuit 115 provided after the AGC loop, that is, after the branch circuit 114 receives the output level control signal set by the AGC adjusting variable resistor 128 from the DC amplifier 129 and the driver 130. Given through. The second gain control circuit 115 outputs an RF signal of a predetermined level based on the output level control signal set by the AGC adjustment variable resistor 128. As described above, the variable resistor 128 sets the AGC level after the AGC loop. The output level control signal set by the variable resistor 128 is sent to the microcomputer 102 and monitored.

The signal whose level is set by the second gain control circuit 115 is amplified by the high frequency amplifier 116, and a part of the output signal is branched by the branch circuit 117 and input to the signal level detector 131. The signal level detection unit 131 has the same configuration as the signal level detection unit 101, detects the output signal level of the high-frequency amplifier 116, converts it to a DC voltage, and outputs it. The signal level detected by the signal level detector 131 is amplified by the DC amplifier 132 and sent to the microcomputer 102. The microcomputer 102 monitors the RF output signal level based on the signal detected by the signal level detector 131.
The RF signal output from the high frequency amplifier 116 is sent to the RF output terminal 119 via the branch circuits 117 and 118, and a part of the signal is branched by the branch circuit 118 and sent to the RF monitor terminal 120. .

[Transmission Conversion Unit Operation]
In the above configuration, the IF signal input to the IF input terminal 81 is input to the intermediate frequency amplifier 83 via the branch circuit 82, amplified, and then the frequency via the low pass filter 84 and the first gain control circuit 85. It is sent to the characteristic correction circuit 86.

  The frequency characteristic correction circuit 86 corrects the frequency characteristic by switching the path circuits 91a to 91d and the attenuators 92a to 92d, or the pseudo-line networks 93a and 93b, and the equalizers 94a and 94b with a switch (not shown).

The pass circuits 91a to 91d in the frequency characteristic correction circuit 86 output the input signal as it is without correcting the frequency characteristic of the input signal.
The attenuators 92a to 92d simply attenuate the level of the input signal and output it.
Further, the pseudo line networks 93a and 93b have a flat characteristic as shown in FIG. 5B when the frequency characteristic has a high level in the low band as shown in FIG. 5A and a low level in the high band. To improve. In the transmission conversion unit 15a shown in FIG. 4, the band characteristics of the frequency band “fc (carrier frequency) ± 2.79 MHz” for one channel, that is, “37.15 MHz (fc: IF frequency) ± 2.79 MHz” are improved. .
The equalizers 94a and 94b improve to a flat characteristic as shown in FIG. 6 (b) when the frequency characteristic is low as shown in FIG. 6 (a) and the low level is low and the high level is high.

  The frequency characteristic correction circuit 86 switches the 1 dB, 2 dB, 4 dB, and 8 dB attenuators 92 a to 92 d, 0.5 dB, and 1 dB pseudo-line networks 93 a, 93 b, 0.5 dB, and 1 dB equalizers 94 a, 94 b by switches. A plurality of frequency characteristics can be handled.

  Then, the IF signal whose frequency characteristic is corrected by the frequency characteristic correction circuit 86 is sent to the mixer 87. The mixer 87 mixes the IF signal whose frequency characteristic is corrected and the local oscillation signal sent from the local oscillation circuit 106 via the attenuator 107, and converts the mixed signal into an RF signal of the original channel. The RF signal converted by the mixer 87 is a low pass filter 110, a channel / band pass filter 112, a high frequency amplifier 113, a branch circuit 114, a second gain control circuit 115, a high frequency amplifier 116, branch circuits 117 and 118, and an RF output terminal 119. And sent to the power amplifier 16a (16b) at the next stage.

  The IF signal input to the IF input terminal 81 is partly branched by the branch circuit 82 and sent to the signal level detector 101. The signal level detection unit 101 detects the level of the IF signal input to the IF input terminal 81, converts it to a DC signal, and outputs it to the microcomputer 102. The microcomputer 102 monitors the presence / absence of the IF input signal and the signal level based on the detection signal sent from the signal level detection unit 101. When the IF signal of the designated channel is not input, the microcomputer 102 is provided in the RF stage. The high frequency amplifiers 111, 113, and 116 are turned off, and when the IF signal of the designated channel is normally input, the high frequency amplifiers 111, 113, and 116 are turned on.

  Further, the microcomputer 102 controls the gain of the first gain control circuit 85 based on the AGC detection output sent from the AGC detector 126 via the DC amplifier 127, and keeps the output signal level constant.

  The second gain control circuit 115 outputs an RF signal having a predetermined level based on the AGC output level control signal set by the variable resistor 128. This RF signal is amplified by the high frequency amplifier 116 and then output from the RF output terminal 119 via the branch circuits 117 and 118.

  As shown in the above embodiment, the first gain control circuit 85 is mounted in the IF stage, the AGC is controlled according to the input level of the IF signal by the microcomputer 102, and the second gain control circuit 115 is provided after the AGC loop. By setting the AGC level with the variable resistor 128, precise AGC control and fine adjustment are possible. According to the standard specification, the AGC response range in the transmission conversion units 15a and 15b is defined such that the UHF output is within ± 0.4 dB with respect to the fluctuation of IF input −10 dBm ± 5 dB. The AGC response range in the transmission conversion being performed can be sufficiently satisfied. Furthermore, by optimizing the operation of the AGC, it is possible to reliably suppress the degradation of noise figure and intermodulation distortion.

Further, by providing the frequency characteristic correction circuit 86 in the IF stage, the frequency characteristic can be arbitrarily corrected, and even if the frequency deviation becomes larger than the specified value by combining the units, the deviation is within the specified value. Can be adjusted.
Since the IF input terminal 81 and the mixer 87 always have a predetermined IF frequency (37.15 MHz), the same circuit can be used regardless of the channel setting.

  In the above embodiment, in the reception conversion units 14a and 14b, the case where only the equalizer 27 is provided as the frequency characteristic correction circuit in the RF stage is shown, but the reception conversion units 14a and 14b are provided in the transmission conversion units 15a and 15b in FIGS. Similarly to the frequency characteristic correction circuit 86, a path circuit, an attenuator, a pseudo-line network, and an equalizer may be combined and switched by a switch to correct the frequency characteristic.

  Further, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.

It is a block diagram which shows the whole structure of the digital television broadcast relay apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of a part of reception conversion unit in the embodiment. It is a block diagram which shows the structure of the other part of the reception conversion unit in the embodiment. It is a block diagram which shows the structure of a part of transmission conversion unit in the embodiment. It is a block diagram which shows the structure of the other part of the transmission conversion unit in the embodiment. It is a figure for demonstrating the frequency characteristic correction | amendment operation | movement of the pseudo-line network which comprises the frequency characteristic correction circuit in the embodiment. It is a figure for demonstrating the frequency characteristic correction | amendment operation | movement of the equalizer which comprises the frequency characteristic correction circuit in the embodiment.

Explanation of symbols

  11a, 11b ... RF input terminal, 12a, 12b ... input filter, 13 ... transmission / reception unit, 14a, 14b ... reception conversion unit, 15a, 15b ... transmission conversion unit, 16a, 16b ... power amplifier, 17 ... switch, 18 ... Output filter, 19 ... RF output terminal, 21 ... RF input terminal, 22 ... high frequency amplifier, 23 ... branch circuit, 24, 26 ... gain control circuit, 25 ... high frequency amplifier, 27 ... equalizer (EQ), 28 ... mixer, 30 ... Amplifier, 31 ... Signal level detection unit, 32 ... Microcomputer (microcomputer), 33, 35 ... DC amplifier, 34,36 ... Driver, 37 ... Input terminal, 38 ... Local oscillation circuit, 39 ... Attenuator, 41 ... Low pass filter (LPF), 42, 44, 45, 51, 52, 56 ... intermediate frequency amplifier, 43 ... gain control Roll circuit 46 ... DC amplifier 47, 48, 61 ... Driver 50 ... SAW filter 53 ... Branch circuit 54 ... Low pass filter (LPF) 55 ... Gain control circuit 57,58 ... Branch circuit 59 ... IF Output terminal 60 ... IF monitor terminal 62 ... Amplifier 63 ... AGC detector 64, 66, 70 ... DC amplifier 65 ... AGC adjusting variable resistor 67,68 ... Driver 69 ... Signal level detector , 81 ... IF input terminal, 82 ... branch circuit, 83 ... intermediate frequency amplifier, 84 ... low pass filter (LPF), 85 ... gain control circuit, 86 ... frequency characteristic correction circuit, 87 ... mixer, 91a to 91d ... pass circuit ( PASS), 92a to 92d ... Attenuator (ATT), 93a, 93b ... Pseudo-line network (BON), 94a, 94b ... Equal Isa (EQ), 101 ... Signal level detection unit, 102 ... Microcomputer (microcomputer), 103 ... DC amplifier, 104 ... Driver, 105 ... Input terminal, 106 ... Local oscillation circuit, 107 ... Attenuator, 110 ... Low pass filter (LPF) , 111, 113 ... high frequency amplifier, 112 ... channel band pass filter (CH / BPF), 114 ... branch circuit, 115 ... gain control circuit, 116 ... high frequency amplifier, 117, 118 ... branch circuit, 119 ... RF output terminal 120, RF monitor terminals, 121, 122, 130, drivers, 125, amplifiers, 126, AGC detectors, 127, 129, 132, DC amplifiers, 128, variable resistors for AGC adjustment, 131, signal level detection unit.

Claims (3)

A digital TV broadcast is received for each channel, amplified by a high frequency amplifier, and then converted to an intermediate frequency signal by a frequency converter, and an intermediate frequency signal converted by the reception converter unit is received by an intermediate frequency amplifier. In a digital television broadcast relay device comprising a transmission conversion unit that amplifies and converts to a high frequency signal by a frequency conversion unit and outputs it,
Each of the reception conversion unit and the transmission conversion unit includes a gain control circuit that adjusts a gain of an amplification unit that amplifies a signal, a signal level detection unit that detects a level of a signal amplified by the amplification unit, and the signal level detection And a microcomputer for controlling the gain control circuit based on the signal level detected by the unit to keep the signal level constant.   The reception conversion unit is provided with a gain control circuit in a high frequency part for amplifying a high frequency signal and an intermediate frequency part for amplifying an intermediate frequency signal, and in a range where the input of the high frequency signal is lower than a preset level, the gain control circuit for the intermediate frequency part The signal level is controlled by controlling the signal level, and in the range where the input of the high frequency signal is higher than the preset level, the signal level is controlled by controlling both the high frequency amplification unit and the gain control circuit of the intermediate frequency unit. The digital television broadcast relay device according to claim 1.   3. The digital television broadcast relay apparatus according to claim 1, wherein a frequency characteristic correction circuit including at least a pseudo line network and an equalizer is provided in one or both of the reception conversion unit and the transmission conversion unit.

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