JP2010050816A - Millimeter-wave transmitting apparatus and millimeter-wave transmitting/receiving system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the level difference between a television broadcast signal and a local oscillation signal to be wirelessly transmitted to a proper value, in a millimeter-wave transmitting apparatus that uses the local oscillation signal of a millimeter-wave band to up-convert the television broadcast signal and wirelessly transmits the up-converted television broadcast signal and the local oscillation signal. <P>SOLUTION: In order to allow a self-heterodyne type receiving apparatus 30 to normally restore a CATV signal before being up-converted by a transmitting apparatus 10, it is necessary to control a level difference between the CATV signal and a local oscillation signal in a reception signal to a proper value (about 15 dB). Then, the transmitting apparatus 10 comprises an AGC circuit 14 for performing level adjustment on the CATV signal, in such a way that the level difference between a pilot signal, corresponding to the CATV signal before up-converting and the local oscillation signal, becomes the targeted level difference. As a result, the level difference between the up-converted CATV signal and the local oscillation signal is controlled to a proper value, so that the receiving apparatus 30 can carry out down-conversion in a normal manner. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a millimeter wave transmission device that up-converts a television broadcast signal using a millimeter wave band local oscillation signal and wirelessly transmits the up-converted television broadcast signal and the local oscillation signal, and the millimeter wave transmission device The present invention relates to a self-heterodyne millimeter wave transmission / reception system composed of a millimeter wave receiver.

  2. Description of the Related Art Conventionally, in a CATV system, a television broadcasting reception system for an apartment house, etc., in order to transmit a television broadcasting signal to a subscriber-side receiving terminal without using a transmission line such as a coaxial cable, the end of the transmission line is used. In addition, a transmission device that up-converts a television broadcast signal to the millimeter wave band and wirelessly transmits it from a transmission antenna is provided, and the subscriber side receives a transmission radio wave from the transmission device and down-converts the received signal. It is proposed to provide a receiving device for restoring the original television broadcast signal before up-conversion (see, for example, Patent Document 1).

  Also, in this type of millimeter-wave transmission / reception system, in order to accurately restore the transmission signal (television broadcast signal) on the receiving device side, it is the same as the local signal used to upconvert the transmission signal on the transmitting device side. A local oscillator signal with a frequency is required, but since this local oscillator signal has a millimeter wave band with a frequency of several tens of GHz, frequency fluctuations are likely to occur, and the same local oscillator signal as that of the transmitter is generated on the receiver side. There was a problem that it was difficult.

  On the other hand, as a millimeter wave transmission / reception system capable of preventing such problems, the transmission device simultaneously transmits the transmission signal up-converted to millimeter wave and the local signal used for the up-conversion. It has been proposed to restore the original transmission signal before up-conversion by multiplying the transmission signal included in the received signal and the local oscillation signal (see, for example, Patent Document 2).

  In this proposed millimeter-wave transmission / reception system, the receiving device becomes a so-called self-heterodyne receiving device, and the transmission signal is down-converted by using the local oscillation signal on the transmission device side without generating the local oscillation signal for down-conversion. Therefore, even if a frequency variation occurs in the local signal, the original transmission signal before being up-converted by the transmission device can be accurately restored.

Therefore, in a system for transmitting a television broadcast signal, such as a CATV system, the proposed self-heterodyne transmission / reception apparatus is also used when the television broadcast signal is up-converted to the millimeter wave band and wirelessly transmitted to the subscriber side. If used, the original television broadcast signal before up-conversion can be accurately restored on the subscriber side.
Japanese Patent No. 3889885 JP 2001-53640 A

  By the way, in order to down-convert a television broadcast signal using a local oscillation signal transmitted together with a millimeter wave band television broadcast signal from the transmission device on the self-heterodyne receiver side, the local oscillation signal becomes a saturation region. Therefore, it is necessary to make the signal level of the local oscillation signal sufficiently higher than that of the television broadcast signal so that the television broadcast signal is in the linear region.

  On the other hand, the transmission power from a transmitting device that wirelessly transmits millimeter waves is normally limited by the Radio Law, etc., so that the local broadcasting signal and the TV broadcasting signal can be restored so that the receiving device can restore the TV broadcasting signal. When the difference in level is increased, the signal level (absolute level) of the television broadcast signal transmitted from the transmission device is reduced, and the quality (C / N: TV broadcast signal) obtained by down-conversion on the reception device side. There is a problem that the carrier-to-noise ratio) deteriorates.

  For this reason, when configuring a self-heterodyne millimeter-wave transmitter that simultaneously transmits a television broadcast signal and a local oscillation signal, a level difference between the millimeter-wave band television broadcast signal transmitted from the transmission antenna and the local oscillation signal. The signal level of each of these signals should be adjusted so that becomes an appropriate value.

  However, conventionally, such level adjustment has not been considered. For example, when the level of a TV broadcast signal before up-conversion transmitted by a CATV system or the like changes in level, the TV broadcast signal after up-conversion and station transmission are accordingly changed. It is conceivable that the level difference with the signal fluctuates and the level difference deviates from the appropriate value.

  The present invention has been made in view of such a problem, and uses a millimeter wave band local signal to upconvert a television broadcast signal, and wirelessly transmits the upconverted television broadcast signal and the local signal. It is an object of the transmission device to control the level difference between a television broadcast signal to be transmitted wirelessly and a local oscillation signal to an appropriate value so that the original television broadcast signal can be satisfactorily restored on the reception device side.

  The millimeter wave transmission device according to claim 1, which has been made to achieve such an object, includes a local oscillation signal generation unit that generates a local oscillation signal having a constant frequency in the millimeter wave band, and a local oscillation signal generation unit that generates the local oscillation signal. Upconverting means for upconverting a television broadcast signal to the millimeter wave band using the generated local oscillation signal, and transmitting the millimeterwave band television broadcast signal upconverted by the upconverting means and the local oscillation signal The level difference between the output means for outputting to the transmission antenna as a signal and wirelessly transmitting from the transmission antenna, and the TV broadcast signal output from the output means and the local oscillation signal is determined by the millimeter-wave receiver that receives the transmission signal. The television broadcast signal and the input to the up-conversion means are set so that the set value is suitable for down-converting the television broadcast signal using the local signal. Characterized in that and a level adjusting means for adjusting at least one of the signal level of the local oscillator signal.

  The millimeter wave transmission device according to claim 2 is the millimeter wave transmission device according to claim 1, wherein the level adjustment means is configured such that the television broadcast signal output from the output means is compared with the local oscillation signal. Thus, the signal level of at least one of the television broadcast signal and the local oscillation signal is adjusted so as to be reduced by a set value set within a range of 6 dB to 26 dB.

  Further, the millimeter wave transmission device according to claim 3 is the millimeter wave transmission device according to claim 1 or 2, wherein the level adjusting means is configured to input a television broadcast signal input to the millimeter wave transmission device. According to the level, at least one of the television broadcast signal and the local oscillation signal input to the up-conversion means so that the level difference is small when the input level is high and the level difference is large when the input level is low. The signal level is adjusted.

  Further, the millimeter wave transmission device according to claim 4 is the millimeter wave transmission device according to any one of claims 1 to 3, wherein the level adjustment unit inputs the television broadcast signal to the up-conversion unit. Based on the gain adjustment circuit provided together with the amplifier circuit in the input path, the signal level of the television broadcast signal before being up-converted by the up-conversion means, and the signal level of the local signal And a first control means for controlling the gain adjustment amount.

  Next, the millimeter wave transmission device according to claim 5 is the millimeter wave transmission device according to any one of claims 1 to 3, wherein the level adjustment unit is connected to the local signal generation unit from the local signal generation unit. A variable attenuator provided on the input path of the local oscillation signal to the converting means and a signal level of the television broadcast signal before being up-converted by the up-converting means are used to control the attenuation amount of the variable attenuator. And two control means.

  Further, the millimeter wave transmission device according to claim 6 is the millimeter wave transmission device according to any one of claims 1 to 5, wherein the up-conversion means uses the local oscillation signal and is 59 GHz or more and 66 GHz. The television broadcast signal is up-converted so that the bandwidth is 2.5 GHz or less within the following frequency band.

  On the other hand, according to the seventh aspect of the present invention, a television broadcast signal is up-converted using a local frequency signal having a constant frequency in the millimeter wave band, and the TV broadcast signal and the local frequency signal after the up-conversion are transmitted from a transmission antenna. A millimeter-wave transmitter for wireless transmission, and a radio wave received from the millimeter-wave transmitter by a receiving antenna, and a television broadcast signal is converted to an original frequency band before up-conversion using a local signal included in the received signal. A self-heterodyne millimeter-wave transmission / reception system comprising a millimeter-wave reception device that down-converts the millimeter-wave reception device, wherein the millimeter-wave transmission device is the millimeter-wave transmission device according to any one of claims 1 to 6. It is characterized by having.

  In the millimeter wave transmission device according to claim 1, the up-conversion unit up-converts the television broadcast signal into the millimeter-wave band using the local oscillation signal generated by the local oscillation signal generation unit, and the output unit includes: The millimeter-wave band television broadcast signal and the local oscillation signal up-converted by the up-conversion means are output as transmission signals to the transmission antenna, so that they are wirelessly transmitted from the transmission antenna.

  Then, the level adjusting means transmits the local difference in the level difference between the television broadcast signal output from the output means and the local oscillation signal included in the received signal on the side of the millimeter wave receiver that has received the transmission signal from the transmission antenna. The signal level of at least one of the television broadcast signal and the local signal input to the up-conversion means is adjusted so that the set value is suitable for down-converting the television broadcast signal using the signal.

  Therefore, according to the millimeter wave transmission apparatus of the present invention, the level difference between the television broadcast signal and the local oscillation signal wirelessly transmitted from the transmission antenna is controlled to the set value (in other words, the appropriate value), and the millimeter wave reception is performed. The original television broadcast signal before up-conversion can be restored to the apparatus satisfactorily.

  Here, the set value of the level difference between the TV broadcast signal after up-conversion and the local signal, which is a target value when the level adjusting means adjusts the signal level of at least one of the TV broadcast signal and the local signal, The millimeter wave receiving device side is equal to or higher than the lower limit value at which the TV broadcast signal can be down-converted by multiplying the TV broadcast signal and the local signal, and the quality of the TV broadcast signal obtained by the down-conversion (C / N) may be less than or equal to the upper limit value that can secure N).

  The level difference setting value (in other words, the appropriate value) varies depending on the wave number (channel number) and frequency bandwidth of a television broadcast signal that is converted into millimeter waves and wirelessly transmitted. As a result of the examination, it was found that, as described in claim 2, it should be set within the range of 6 dB or more and 26 dB or less, more preferably about 15 dB.

  Further, the level difference may be fixed to a constant value (for example, 15 dB), but according to the input level of the television broadcast signal input to the millimeter wave transmission device as described in claim 3. It may be changed.

  According to the millimeter wave transmission apparatus of claim 3, when the input level of the television broadcast signal is low, the television broadcast signal is increased so that the level difference between the up-converted television broadcast signal and the local oscillation signal becomes large. Since the signal level of at least one of the local oscillation signal and the local oscillation signal is adjusted, the signal level of the local oscillation signal becomes larger than the television broadcast signal on the receiving device side, and the television broadcast signal is converted using the local oscillation signal. The conversion efficiency when down-converting can be improved.

  For this reason, when the signal level of a television broadcast signal input to the millimeter wave transmitter is low and the quality (C / N) is low, the television broadcast obtained on the receiver side by wireless transmission using millimeter waves Further deterioration of signal quality (C / N) can be prevented.

  In addition, according to the millimeter wave transmission device of claim 3, when the input level of the television broadcast signal is high (in other words, the quality (C / N) of the television broadcast signal input to the millimeter wave transmission device is high). ), The signal level of at least one of the television broadcast signal and the local signal is adjusted so that the level difference between the TV broadcast signal after the up-conversion and the local signal is small.

  For this reason, if the millimeter-wave transmission device is configured so that the transmission power is constant, the transmission level of the television broadcast signal is further increased to prevent the quality (C / N) of the television broadcast signal from being lowered. it can.

  Next, to adjust the signal level of the TV broadcast signal before up-conversion so that the level difference between the TV broadcast signal after up-conversion and the local oscillation signal becomes a set value (for example, 15 dB), As described, an amplification circuit with a gain adjustment circuit is provided in an input path for inputting a television broadcast signal to the up-conversion means, and the amount of gain adjustment by the gain adjustment circuit is adjusted by the first control means in the television before the up-conversion. Control may be performed based on the signal level of the broadcast signal and the signal level of the local signal.

  In other words, the level difference between the TV broadcast signal after up-conversion and the local oscillation signal changes according to the level difference between the TV broadcast signal before up-conversion and the local oscillation signal, so gain adjustment is based on these level differences. If the signal level of the TV broadcast signal before up-conversion is adjusted by controlling the circuit, the level difference between the TV broadcast signal after up-conversion that is wirelessly transmitted to the millimeter wave receiver and the local signal is set. It can be controlled to a value (in other words, an appropriate value).

  The signal level of the television broadcast signal before up-conversion is adjusted so that the level difference between the television broadcast signal after up-conversion and the local oscillation signal becomes a set value (for example, 15 dB). As described above, a variable attenuator is provided in the input path of the local oscillation signal from the local oscillation signal generation means to the up-conversion means, and the second control means determines the amount of attenuation of the variable attenuator in the television broadcast before the up-conversion. You may make it control based on the signal level of a signal.

  In other words, even when the signal level of the local signal is adjusted in this way, the level difference between the up-converted television broadcast signal and the local signal that are wirelessly transmitted to the millimeter wave receiver is set (in other words, If so, it can be controlled to an appropriate value).

  On the other hand, the continuous frequency bandwidth that can be used to wirelessly transmit a television broadcast signal or the like using a millimeter wave of 60 GHz band in Japan is 2.5 GHz, and the frequency band of the millimeter wave is 59 GHz. ~ 66 GHz.

  For this reason, as described in claim 6, the up-conversion means uses the local oscillation signal to convert the television broadcast signal so that the bandwidth is 2.5 GHz or less within a frequency band of 59 GHz to 66 GHz. It is desirable to configure to up-convert, and for this purpose, the frequency of the local oscillation signal may be set to an arbitrary frequency within the range of 60.25 GHz to 64.75 GHz.

  Next, in the millimeter wave transmission / reception system according to claim 7, the millimeter wave transmission device wirelessly transmits the television broadcast signal up-converted to the millimeter-wave band and the local oscillation signal used for the up-conversion. On the receiving device side, the received signal that received the transmission radio wave is down-converted using the local signal included in the received signal, thereby restoring the original television broadcast signal before the millimeter-wave transmitting device up-converts. This is a self-heterodyne millimeter-wave transmission / reception system.

  In this millimeter wave transmission / reception system, the millimeter wave transmission device according to any one of claims 1 to 6 is provided as a millimeter wave transmission device. The original television broadcast signal before being up-converted by the millimeter wave transmitter can be accurately restored without degrading the signal quality (C / N).

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram showing the overall configuration of a millimeter wave transmission / reception system to which the present invention is applied.
The millimeter wave transmission / reception system of this embodiment is provided on the terminal side of the transmission line of the CATV system, and transmits a CATV signal (VHF, UHF), various TV broadcast signals such as BS and CS transmitted by the CATV system ( Frequency: 70 MHz to 1250 MHz) is converted to a millimeter wave band (60 GHz band) and wirelessly transmitted to a receiving terminal (such as a television receiver) on the subscriber side. The millimeter wave receiver 30 is configured.

  The CATV system processes a plurality of receiving antennas 2 (only one is shown in the figure) that receives various types of television broadcasting radio waves such as terrestrial waves (VHF, UHF), BS, CS, and the like, and processes received signals from each receiving antenna 2. The head end 4 is sent to the transmission line, and the television broadcast signal transmitted from the head end 4 through the transmission line is amplified and output to the terminal side, and the amplifiers 6, 8,.

  The head end 4 has a constant frequency (for example, 450 MHz) that does not overlap with a television broadcast signal of a specific channel in the same frequency band as the reception signal as well as a reception signal (that is, a television broadcast signal) from each reception antenna 2. A pilot signal is output. The pilot signal is used by a transmission device such as amplifiers 6 and 8 constituting the CATV system to adjust the signal level of the CATV signal.

  Next, the millimeter wave transmitter 10 includes an amplifier circuit 12 that amplifies the CATV signal from the head end 4 input through the transmission line, and an AGC circuit that automatically adjusts the output level of the CATV signal from the amplifier circuit 12 (automatically). (Gain adjustment circuit) 14, a local oscillator 16 that generates a local oscillation signal having a constant frequency (for example, 60.25 GHz) in the millimeter wave band, a CATV signal output from the AGC circuit 14, and a local oscillation signal generated by the local oscillator 16 The mixer 18 that upconverts the CATV signal to the millimeter wave band by mixing the upper and lower sidebands (double sideband: DSB) centered on the local signal among the millimeter wave band signals output from the mixer 18. ), That is, a millimeter wave signal having a frequency of 60.25 GHz ± 1.25 GHz (refer to the frame indicated by a one-dot chain line in FIG. 1) is selectively passed. Band-pass filter (BPF) 20 and the millimeter-wave band CATV signal that has passed through the band-pass filter 20 are amplified and output to the millimeter-wave transmission antenna 24. An amplifier circuit 22 that wirelessly transmits a signal is provided.

  Further, the millimeter wave transmitter 10 is provided with a narrow-band bandpass filter (BPF) 26 for extracting a pilot signal from the CATV signal amplified by the input-side amplifier circuit 12, and this bandpass filter The pilot signal extracted at 26 is input to the AGC circuit 14 together with the local oscillation signal generated by the local oscillator 16.

  The AGC circuit 14 includes a variable attenuator (hereinafter simply referred to as an attenuator (ATT)) 28 capable of adjusting an attenuation amount, and a control circuit 27 that adjusts the attenuation amount of the attenuator 28. The output CATV signal is attenuated by the attenuator 28 and output to the mixer 18, thereby adjusting the signal level of the CATV signal input to the mixer 18.

  The control circuit 27 compares the signal level of the pilot signal extracted by the bandpass filter 26 with the local signal generated by the local oscillator 16, and the level difference becomes a preset target level difference. Thus, the amount of attenuation of the attenuator 28 (in other words, the amplification factor (gain) of the amplifier circuit 12 is controlled.

  Note that the target level difference used by the control circuit 27 to control the attenuation amount of the attenuator 28 is output from the amplifier circuit 22 to the millimeter wave transmission antenna 24 and is transmitted wirelessly from the millimeter wave transmission antenna 24 (FIG. 1 is set in advance so that the level difference between the up-converted CATV signal and the local oscillation signal is 15 dB. As a result, the millimeter wave transmission apparatus 10 wirelessly transmits a millimeter wave band CATV signal having a signal level lower by about 15 dB than the local oscillation signal together with the local oscillation signal.

  On the other hand, the millimeter wave receiving device 30 includes a millimeter wave receiving antenna 32 for receiving a radio wave transmitted from the millimeter wave transmitting antenna 24 of the millimeter wave transmitting device 10, and an amplification for amplifying a reception signal from the millimeter wave receiving antenna 32. Among the reception signals amplified by the circuit 34 and the amplification circuit 34, a double sideband (DSB) signal composed of a CATV signal and a local oscillation signal up-converted to the millimeter wave band on the millimeter wave transmitter 10 side, that is, , Frequency: 60.25 GHz ± 1.25 GHz millimeter-wave signal (refer to the frame indicated by the alternate long and short dash line in FIG. 1), a band-pass filter (BPF) 36 that selectively passes through, and the DSB that has passed through this band-pass filter 36 A multiplier 38 that multiplies (squares) the signal, and among the output signals from the multiplier 38, the frequency difference between the CATV signal in the millimeter wave band and the local oscillation signal The band-pass filter (BPF) 40 that selectively passes the original CATV signal (frequency: 70 MHz to 1250 MHz) before up-conversion, and the CATV signal that has passed through the band-pass filter 40 are amplified to receive a television image. An amplifier circuit 42 is provided for outputting to a receiving terminal such as a machine.

  That is, the millimeter wave receiving apparatus 30 multiplies the reception signal from the millimeter wave transmission apparatus 10 by the multiplier 38, so that the millimeter wave band CATV signal included in the reception signal is included in the same reception signal. It is configured as a self-heterodyne receiving device that performs frequency conversion using a local oscillation signal and extracts the original CATV signal before being up-converted by the millimeter wave transmission device 10 from the frequency-converted signal. .

  In order to enable the self-heterodyne millimeter wave receiver 30 to restore the CATV signal from the received signal, the local signal is included in the saturated signal and the CATV signal is included in the linear signal. It is necessary to set the level difference between the CATV signal and the local signal to an appropriate value (approximately 15 dB in this embodiment).

  On the other hand, in the present embodiment, when the millimeter wave transmitter 10 mixes the CATV signal and the local oscillation signal and upconverts the CATV signal to the millimeter wave band, the CATV signal and the local oscillation signal before the up-conversion. The AGC circuit 14 adjusts the signal level of the CATV signal (in other words, the amplification factor (gain) of the amplifier circuit 12) so that the difference between the two levels becomes the target level difference.

  For this reason, when the millimeter wave receiving device 30 receives the transmission radio wave from the millimeter wave transmitting device 10, the level difference between the CATV signal and the local oscillation signal included in the received signal is approximately irrespective of the signal level of the received signal. In addition, since the target level difference is set so that the level difference between the CATV signal after up-conversion and the local oscillation signal is 15 dB, the CATV signal and the local oscillation signal included in the reception signal are The level difference is about 15 dB.

  Therefore, according to the millimeter wave transmission device 10 of the present invention, the level difference between the CATV signal (multi-channel television broadcast signal) wirelessly transmitted from the millimeter wave transmission antenna 24 and the local signal is set to an appropriate value of approximately 15 dB. By controlling, the original CATV signal before up-conversion can be satisfactorily restored to the millimeter wave receiver 30.

  In the millimeter wave transmitting apparatus 10 of the present embodiment, the local oscillator 16 corresponds to a local signal generation unit of the present invention, and the mixer 18 corresponds to an up-conversion unit of the present invention, and includes a bandpass filter 20 and an amplification. The circuit 22 corresponds to the output means of the present invention, and the AGC circuit 14 corresponds to the level adjusting means of the present invention. The attenuator 28 in the AGC circuit 14 corresponds to the gain adjustment circuit of the present invention, and the control circuit 27 in the AGC circuit 14 corresponds to the first control means of the present invention.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect can be taken in the range which does not deviate from the summary of this invention.
For example, in the above embodiment, a pilot signal output together with the CATV signal from the head end 4 is extracted by the band pass filter 26 as a signal representative of the CATV signal before up-conversion, and the extracted pilot signal is converted into an AGC circuit. The TV broadcast signal of a specific channel included in the CATV signal is extracted by the band pass filter 26 instead of the pilot signal, and the extracted TV broadcast signal is input to the AGC circuit 14. You may do it.

  In the above-described embodiment, the AGC circuit 14 is provided in the millimeter wave transmitter 10, and the CATV signal transmitted from the millimeter wave transmitter 10 is wirelessly transmitted by the AGC circuit 14 by adjusting the level of the CATV signal before up-conversion. The level difference between the signal and the local oscillation signal is controlled to the set value (15 dB). To control this level difference to the set value, the signal level of the CATV signal before up-conversion and the local oscillator 16 are controlled. The signal level of the local oscillation signal output from each may be adjusted, or only the signal level of the local oscillation signal may be adjusted.

  In this way, by adjusting only the signal level of the local signal, the level difference between the CATV signal wirelessly transmitted from the millimeter wave transmitter 10 and the local signal is controlled to the set value (15 dB). The millimeter wave transmitter 10 may be configured as shown in FIG.

  That is, in the millimeter wave transmitter 10 shown in FIG. 2, the attenuator 28 as a variable attenuator is provided on the transmission path of the local signal from the local oscillator 16 to the mixer 18, and the control circuit 27 A pilot signal (or a television broadcast signal of a specific channel) included in the CATV signal amplified by the circuit 12 is captured via the band pass filter 26, and based on the signal level of the captured pilot signal (or television broadcast signal), The attenuation amount of the attenuator 28 is adjusted.

  Therefore, according to the millimeter wave transmitter 10 shown in FIG. 2, the control circuit 27 functions as the second control means of the present invention, and the signal of the local signal input to the mixer 18 for up-conversion of the CATV signal. By adjusting the level, the level difference between the CATV signal wirelessly transmitted from the millimeter wave transmitter 10 and the local signal can be controlled to the set value (15 dB).

  Next, in the above embodiment, the level difference between the local oscillation signal and the millimeter-wave band CATV signal, which is suitable for restoring the CATV signal before up-conversion in the millimeter-wave receiver 30, is 15 dB. As described above, the appropriate value of the level difference varies depending on the number of TV broadcast signal channels constituting the CATV signal, the frequency band of the CATV signal, the characteristics of the millimeter wave receiver 30, and the like.

  According to the experiment by the present inventor, the appropriate value of the level difference may be set within a range of approximately 6 dB to 26 dB. Therefore, the control circuit 27 is used to control the attenuation amount of the attenuator 28. The target level difference between the CATV signal before conversion and the local oscillation signal may be set based on the most suitable level difference (setting value) within the range.

  On the other hand, in the millimeter wave transmitting apparatus 10 shown in FIGS. 1 and 2, the control circuit 27 adjusts the attenuation level of the attenuator 28 to change the signal level of the CATV signal or the local oscillation signal before the up-conversion. In the above description, the level difference between the CATV signal and the local oscillation signal is controlled to be a constant set value (15 dB).

  However, as shown in FIGS. 3A and 3B, the millimeter wave transmitter 10 is included in the CATV signal before being amplified by the amplifier circuit 12 via the bandpass filter 29 in the control circuit 27. A pilot signal (or a TV broadcast signal of a specific channel) is input, and the control circuit 27 responds to the signal level of the input pilot signal (or a TV broadcast signal of a specific channel) according to the control characteristics shown in FIG. Thus, the signal level of the CATV signal or the local oscillation signal before up-conversion may be controlled.

  That is, by inputting the CATV signal before being amplified by the amplifier circuit 12 (specifically, a pilot signal or a television broadcast signal) to the control circuit 27, the smaller the signal level of the input CATV signal, the more the post-upconvert. The signal level of the CATV signal before up-conversion or the local signal is controlled so that the level difference between the CATV signal and the local signal becomes large.

  If the millimeter wave transmitting apparatus 10 is configured in this way, when the CATV signal input level to the millimeter wave transmitting apparatus 10 is low and the quality (C / N) of the CATV signal is likely to be lowered, the CATV after up-conversion is performed. Since the signal level of the local oscillation signal is higher than that of the signal, the conversion efficiency when the CATV signal is down-converted on the millimeter wave receiving device 30 side is improved, and the quality (C / N) of the CATV signal is reduced by the down-conversion. ) Can be prevented from deteriorating.

  In this case, when the input level of the CATV signal is high (in other words, when the quality (C / N) of the television broadcast signal is high), the level difference between the CATV signal after up-conversion and the local oscillation signal is different. Therefore, if the amplifier circuit 22 at the output stage is configured to control the transmission power from the antenna 24 to be constant, the transmission level of the CATV signal can be further increased. Therefore, also in this case, it is possible to prevent the quality (C / N) of the CATV signal down-converted on the millimeter wave receiving device 30 side from deteriorating.

  In the characteristic diagram of FIG. 4, when the input level of the CATV signal is 57 to 81 [dBμV], the level difference (set value) between the CATV signal after up-conversion and the local oscillation signal is 26 to 6 [dB]. It represents that it is controlled within the range of.

  When the level difference (setting value) between the CATV signal after up-conversion and the local oscillation signal is controlled in accordance with the input level of the CATV signal to the millimeter wave transmitter 10 as described above, FIG. As indicated by the dotted line, the level difference (set value) may be continuously changed according to the change in the input level of the CATV signal.

  Further, as shown by the solid line in FIG. 4, when the input level of the CATV signal is in the range of 57 to 64 [dBμV] and 74 to 81 [dBμV], the level difference (set value) is continuously changed, and CATV When the input level of the signal is in the range of 64 to 74 [dBμV], the level difference (set value) may be fixed to 15 [dB] as a reference.

  Next, in the above embodiment, when the CATV signal is up-converted to the millimeter wave band in the millimeter wave transmitter 10, the local oscillation signal having the frequency of 60.25 GHz is used, and the CATV signal is converted into the local oscillation signal. Although it has been described that it is converted into a millimeter wave signal having a center frequency of 60.25 GHz ± 1.25 GHz, the frequency of this local oscillation signal is appropriately set according to the frequency of the millimeter wave available for wireless transmission of the CATV signal. do it.

  Currently, a continuous frequency bandwidth that can be used for wirelessly transmitting a television broadcast signal or the like using a millimeter wave of 60 GHz band in Japan is 2.5 GHz, and the frequency band of the millimeter wave is 59 GHz. In view of this point, it is desirable that the CATV signal after up-conversion should have a bandwidth of 2.5 GHz or less in a frequency band of 59 GHz or more and 66 GHz or less. The frequency of the local oscillation signal may be set to an arbitrary frequency within 60.25 GHz to 64.75 GHz.

  Furthermore, in the above embodiment, the case where the millimeter-wave transmission / reception system of the present invention is constructed on the terminal side of the CATV system has been described. However, the millimeter-wave transmission / reception system of the present invention is, for example, a receiving antenna in an apartment house or a private house. Even in a receiving system that transmits a received signal from a receiver to one or a plurality of receiving terminals, it can be applied in the same manner as in the above embodiment.

  In this case, since the pilot signal is not normally given to the reception signal transmitted to the terminal side, the AGC circuit 14 of the millimeter wave transmission apparatus 10 has a signal indicating the signal level of the reception signal before up-conversion. A TV broadcast signal of a specific channel may be input.

It is a block diagram showing the structure of the whole millimeter wave transmission / reception system of embodiment. It is a block diagram showing the modification of the millimeter wave transmission apparatus shown in FIG. It is a block diagram showing the further modification of the millimeter wave transmission apparatus shown to FIG. It is explanatory drawing showing the control characteristic of the level difference in the millimeter wave transmitter shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Reception antenna, 4 ... Head end, 6, 8 ... Amplifier, 10 ... Millimeter wave transmission apparatus, 12 ... Amplification circuit, 14 ... AGC circuit, 16 ... Local oscillator, 18 ... Mixer, 20 ... Band pass filter, 22 ... Amplifying circuit, 24 ... millimeter wave transmitting antenna, 26 ... band pass filter, 27 ... control circuit, 28 ... attenuator, 29 ... band pass filter, 30 ... millimeter wave receiving device, 32 ... millimeter wave receiving antenna, 34 ... amplifying circuit, 36... Bandpass filter, 38... Multiplier, 40.

Claims (7)

A local oscillation signal generating means for generating a local oscillation signal having a constant frequency in the millimeter wave band;
Using the local oscillation signal generated by the local oscillation signal generation means, up-conversion means for up-converting a television broadcast signal into a millimeter wave band;
Output means for outputting a millimeter-wave band television broadcast signal up-converted by the up-conversion means and the local oscillation signal as a transmission signal to a transmission antenna, and transmitting the radio from the transmission antenna;
The level difference between the television broadcast signal output from the output means and the local oscillation signal is suitable for down-converting the television broadcast signal using the local oscillation signal on the side of the millimeter wave receiver that has received the transmission signal. Level adjusting means for adjusting the signal level of at least one of the television broadcast signal and the local signal input to the up-converting means so as to be set values,
A millimeter wave transmitter characterized by comprising:   The level adjustment means is configured to reduce the television broadcast signal and the television broadcast signal so that the television broadcast signal output from the output means is smaller than the local signal by a set value set in a range of 6 dB to 26 dB. 2. The millimeter wave transmitter according to claim 1, wherein a signal level of at least one of the local signals is adjusted.   The level adjusting means is configured such that the level difference is small when the input level is high and the level difference is large when the input level is low, according to the input level of the television broadcast signal input to the millimeter wave transmission device. 3. The millimeter wave transmission device according to claim 1, wherein the level of at least one of a television broadcast signal input to the up-conversion means and the local oscillation signal is adjusted. The level adjusting means includes
A gain adjustment circuit provided together with an amplifier circuit in an input path for inputting the television broadcast signal to the up-conversion means;
First control means for controlling the amount of gain adjustment by the gain adjustment circuit based on the signal level of the television broadcast signal before being up-converted by the up-conversion means and the signal level of the local oscillation signal;
The millimeter-wave transmitter according to any one of claims 1 to 3, further comprising: The level adjusting means includes
A variable attenuator provided in the input path of the local oscillation signal from the local oscillation signal generation means to the up-conversion means;
Second control means for controlling the attenuation amount of the variable attenuator based on the signal level of the television broadcast signal before being up-converted by the up-conversion means;
The millimeter-wave transmitter according to any one of claims 1 to 3, further comprising:   The up-conversion means uses the local signal to up-convert the television broadcast signal so that a bandwidth is 2.5 GHz or less within a frequency band of 59 GHz to 66 GHz. The millimeter-wave transmitter according to any one of claims 1 to 5. A millimeter-wave transmission device that up-converts a television broadcast signal using a local frequency signal of a constant frequency in the millimeter wave band, and wirelessly transmits the television broadcast signal and the local frequency signal after the up-conversion from a transmission antenna;
A millimeter wave receiver that receives a transmission radio wave from the millimeter wave transmitter by a receiving antenna and downconverts a television broadcast signal to an original frequency band before upconversion using a local signal included in the received signal; ,
A self-heterodyne millimeter-wave transmission / reception system equipped with
A millimeter-wave transmission / reception system comprising the millimeter-wave transmission device according to any one of claims 1 to 6 as the millimeter-wave transmission device.

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