JP3604912B2 - Tuner for cable modem - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tuner for a cable modem, and more particularly to a tuner for a cable modem that is easy to adjust and that is downsized.
[0002]
[Background technology]
In CATV, HFCs (abbreviation of Hybrid Fiber / Coax) adopting a coaxial cable as a drop-in line of each home and an optical fiber cable as a trunk line are being introduced.
[0003]
HFC is adopted to provide a broadband data communication service of several Mbit / s to each home. The use of HFC can provide a high-speed data line having a bandwidth of 6 MHz and a transmission speed of 30 Mbit / sec even in a 64 QAM (Quadrature Amplitude Modulation) system.
[0004]
By using a cable modem for the high-speed data line, high-speed data communication of 4 Mbits / sec to 27 Mbits / sec using a free channel of CATV is realized. The above-described cable modem has a tuner, and the tuner for the cable modem has a UFH band (B3 band) having 470 to 860 MHz, a VHF High band (B2 band) having 170 to 470 MHz, and a VHF Low band (B1 band) having 54 to 170 MHz. Band). However, band division is not specified here.
[0005]
FIG. 4 is a circuit diagram of a tuner for a cable modem for explaining the background of the present invention. In the circuit of the tuner B for the cable modem shown in FIG. 4, the high-frequency amplification input tuning circuit is improved to improve the characteristics of the B3 band.
[0006]
In FIG. 4, a tuner for a cable modem includes an input terminal 1, an HPF (abbreviation for high-pass filter) 2, a data terminal 41, and a receiving circuit for each of the above-described B1 to B3 bands for communication-connecting a line (not shown) with the tuner. , IF (intermediate frequency) amplifier circuits 55 and 57, a SAW filter 56, and an IF output terminal 15. HPF2 may be an IF filter.
[0007]
The data signal input from the data terminal 41 is connected to the input terminal 1 through the upstream circuit 40.
[0008]
The receiving circuits for each of the B1 to B3 bands described above include input signal switching circuits 18 to 20 to which a switching method using a switching diode or a method using a filter by band division is applied, and high-frequency amplification input tuning circuits 3 to 5 respectively. , Each of the high-frequency amplifiers 6 to 8, each of the high-frequency amplification output tuning circuits 70 to 72, each of the mixing circuits 9 to 11, and each of the local oscillation circuits 12 to 14.
[0009]
The input signal switching circuits 18 to 20 receive B1 to B3 band reception signals and selectively output only reception signals in a predetermined frequency band.
[0010]
The high-frequency amplification input tuning circuits 3 to 5 tune each of the received signals selected and output by the input signal switching circuits 18 to 20 to a desired frequency (frequency of a desired channel) using a tuning coil or the like in each band, and output. .
[0011]
Each of the high-frequency amplifiers 6 to 8 amplifies and outputs the output signals of the high-frequency amplification input tuning circuits 3 to 5 so as to prevent deterioration of the SN ratio in each band.
[0012]
Each of the high-frequency amplification output tuning circuits 70 to 72 tunes the output signal of each of the high-frequency amplifiers 6 to 8 to a desired frequency in each band using a tuning coil or the like, and outputs the tuned signal.
[0013]
The local oscillation circuits 12 to 14 oscillate stably to generate a predetermined intermediate frequency corresponding to each band, and the mixing circuits 9 to 11 convert the signals output from the high-frequency amplification output tuning circuits 70 to 72 by local oscillation signals. Since the signal is converted into an intermediate frequency signal, the local oscillation circuits 12 to 14 and the mixing circuits 9 to 11 form a frequency conversion circuit for each band.
[0014]
As for the B3 band receiving circuit, a high frequency amplification output tuning circuit 70 is provided at the output stage of the high frequency amplifier 6.
[0015]
After that, the output signal of each receiving circuit is amplified to a predetermined level by the IF amplifier circuit 55, frequency-converted to a predetermined level by the SAW filter 56 and the IF amplifier circuit 57, and output through the IF output terminal 15.
[0016]
In the receiving circuit for the B3 band, the portion related to the high-frequency amplification input tuning circuit 3, the high-frequency amplification output tuning circuit 70, and the local oscillation circuit 12 is configured to improve the characteristics of the B3 band.
[0017]
The high frequency amplification input tuning circuit 3 includes coupling capacitors 16 and 24 for cutting DC components, an impedance matching coil 17, a tuning coil 21, a capacitance change ratio suppressing capacitor 22, a variable capacitance diode 23, a bias resistor 25, and an RFC (high frequency choke coil). 26, a bypass capacitor 27, a tuning voltage terminal 28, and a UHF band power supply voltage terminal 29.
[0018]
By the coupling capacitors 16 and 24 and the impedance matching coil 17, impedance matching between the input signal switching circuit 18 in the previous stage and the high frequency amplifier 6 and the high frequency amplification input tuning circuit 3 in the next stage is achieved.
[0019]
A tuning circuit is formed by the tuning coil 21, the capacitance change ratio suppressing capacitor 22, and the variable capacitance diode 23. The tuning point of this tuning circuit is adjusted by the tuning voltage supplied from the tuning voltage terminal 28 to the variable capacitance diode 23 via the bias resistor 25.
[0020]
A predetermined bias voltage of the B3 band is supplied to the high frequency amplifier 6 of the next stage from the power supply voltage terminal 29 of the UHF band via the RFC 26.
[0021]
Since the high-frequency amplification input tuning circuit 3 supplies a bias to the high-frequency amplifier 6 at the subsequent stage via the RFC 26, a resonance circuit is formed by the RFC 26 and the input capacitance of the high-frequency amplifier 6 at the subsequent stage.
[0022]
The high frequency amplification output tuning circuit 70 includes a bypass capacitor 30, an RFC 31, a damping resistor 32, coupling capacitors 33 and 39, variable capacitance diodes 34 and 48, bias resistors 35 and 42, capacitance change ratio suppressing capacitors 36 and 51, and tuning coils 37 and 38. including.
[0023]
Here, a primary side tuning circuit is formed by the variable capacitance diode 34 and the tuning coil 37, and a secondary side tuning circuit is formed by the variable capacitance diode 48 and the tuning coil 38. Tuning coils 37 and 38 are coupled.
[0024]
The tuning coils 21, 37 and 38 are so-called air-core coils without iron cores.
[0025]
In addition, it includes a bias resistor 43, a coupling capacitor 44, a variable capacitance diode 45, a capacitance change ratio suppressing capacitor 46, and a resonance coil 47 in connection with adjustment of the oscillation frequency of the local oscillation circuit 12.
[0026]
In operation, the CATV signal has an up signal of 5 to 42 MHz and a down signal of 54 to 860 MHz, and is input / output between the tuner circuit and a cable (not shown) via the input terminal 1.
[0027]
A data signal subjected to quadrature phase shift modulation from a QPSK (quadrature phase shift keying) transmitter (not shown) is introduced into the uplink signal via a data terminal 41. The data signal is supplied to the input terminal 1 via the data terminal 41 and the upstream circuit 40.
[0028]
Since the downstream signal passes through the HPF (IF filter) 2 and is provided to the input switching circuits 18 to 20, only the receiving circuit whose frequency of the downstream signal corresponds to the operating frequency of the three receiving circuits operates. , And other receiving circuits do not operate. The operation of each receiving circuit is common.
[0029]
Next, an operation state of the receiving circuit of each band will be described.
The CATV signal is amplified by the high frequency amplifiers 6 to 8 via the input switching circuits 18 to 20 and the high frequency amplification input tuning circuits 3 to 5 and is derived as a reception signal via the high frequency amplification output tuning circuits 70 to 72.
[0030]
After that, the received signal is converted into an intermediate frequency signal by the mixing circuits 9 to 11 and the local oscillation circuits 12 to 14, and is subjected to LOW IF conversion by the IF amplifier circuits 55 and 57 and the SAW filter 56, and is led to the output terminal 15. .
[0031]
Note that these series of operations are performed by selecting data from a CPU (not shown) to a PLL selecting circuit (not shown), performing channel selection based on the data, and simultaneously performing an input signal switching circuit for band switching according to band characteristics. This is realized by operating and switching the power supply of each band.
[0032]
[Problems to be solved by the invention]
When the circuit of the cable modem tuner B of FIG. 4 was manufactured, it was necessary to adjust the tuning coils 21, 37 and 38 and the resonance coil 47.
[0033]
In detail, by changing the inductance by changing the winding space of the coils of the air-core coils 21, 37 and 38, the resonance coil 47 is adjusted while moving the resonance point of the tuning circuit, and the signal waveform in the high-frequency amplifier circuit is adjusted. Was being adjusted. As a result, variations in capacitance of elements such as transistors, capacitors, and variable capacitance diodes and variations in inductance of the coil itself have been absorbed.
[0034]
In this case, the time required for processing the coil for adjustment accounts for 30% of the entire adjustment time of the tuner B for the cable modem, and the adjustment by the tuner cannot be performed efficiently.
[0035]
In the cable modem tuner B shown in FIG. 4, the resistors and capacitors are formed into chips and can be miniaturized, whereas the tuning coils 21, 37 and 38 which are air-core coils are formed by inductors. The shape is physically determined, and miniaturization is difficult.
[0036]
Also, attempts have been made to automatically insert or surface mount the tuning coils 21, 37 and 38 of the air-core coil on the substrate of the tuner circuit, but this has a low efficiency in reducing the manufacturing cost, and the coil is omitted. Required no adjustment.
[0037]
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a tuner for a cable modem which can reduce the manufacturing cost and reduce the size.
[0038]
[Means for Solving the Problems]
The cable modem tuner according to claim 1 includes an input unit that receives a multi-wave received signal, selects and outputs the signal to one of a plurality of different frequency bands including UHF, and a first inductance element. Then, in each system, an input tuning unit that tunes each reception signal selected and output by the input unit to a desired frequency in each system by a first inductance element and outputs the signal, and amplifies an output signal of each input tuning unit in each system. An output tuning unit having an amplification unit and a second inductance element, wherein the output signal of each amplification unit is tuned to the desired frequency by the second inductance element in each system and output, and an output signal of each output tuning unit And a frequency conversion unit that converts each signal into a signal of a desired intermediate frequency in each system, and the first and second inputs in the UHF system. Inductance element is configured so that a strip line.
[0039]
Therefore, in the UHF system, since the inductance element for tuning in the input and output tuning sections is a strip line, adjustment of the tuning coil is omitted, and the adjustment cost during manufacturing is reduced.
[0040]
In addition, since the inductance element is formed of the strip line as described above, the flattening and miniaturization of the cable modem tuner are promoted.
[0041]
Further, since the inductance element is formed of a strip line as described above, the adjustment of the inductance element is omitted, and the processing time for the inductance element is omitted, so that the manufacturing cost for the tuner for the cable modem is reduced.
In the above-described cable modem tuner, the frequency conversion unit in the UHF system receives the local oscillation circuit that oscillates at a predetermined frequency using the resonance coil, and receives the oscillation signal of the local oscillation circuit and the output signal of the output tuning unit. A predetermined frequency of the local oscillation circuit is a frequency capable of absorbing variations in tuning characteristics.
Therefore, the oscillation frequency of the local oscillation circuit is optimally adjusted according to the characteristics of the output signal of the output tuning circuit, that is, the variation of the tuning characteristics, and the deviation of tracking is absorbed. As a result, the processing time during the manufacture of the cable modem tuner is reduced, and the manufacturing cost is reduced.
[0042]
According to a second aspect of the present invention, there is provided a tuner for a cable modem according to the first aspect, wherein an output tuning unit in a UHF system includes a primary side tuning unit and a secondary side tuning unit each having a strip line. The strip lines of the primary-side and secondary-side tuning units are coupled, and the coupling unit is provided with an inductance unit.
[0043]
Therefore, the variation in the pass bandwidth in the UHF system due to the mass production lot at the time of manufacturing the cable modem tuner is absorbed by the inductance portion, and the adjustment cost at the time of manufacturing the tuner is reduced.
[0046]
The method according to claim 3 is a method for adjusting a tuner for a cable modem .
The cable modem tuner has an input unit that receives a multi-wave received signal, selects and outputs the received signal to any of a plurality of different frequency bands including UHF, and a first inductance element. An input tuning unit that tunes each output signal to a desired frequency in each system by a first inductance element and outputs the same, an amplification unit that amplifies an output signal of each input tuning unit in each system, and a second inductance. An output tuning unit that tunes the output signal of each amplifying unit to a desired frequency by a second inductance element in each system and outputs the output signal of each output tuning unit in each system. And a frequency conversion unit for converting the signal into a signal.
The first and second inductance elements in the UHF system are formed of strip lines, and the frequency converter in the UHF system uses a resonance coil to oscillate at a predetermined frequency, and tunes an oscillation signal of the local oscillation circuit to an output signal. And a mixing circuit that receives the output signal of the section, converts the signal into an intermediate frequency signal, and outputs the intermediate frequency signal.
The predetermined frequency of the local oscillation circuit is a frequency that can absorb variations in tuning characteristics.
Then, with the cable modem tuner further equipment system for adjusting, in equipment system UHF strains, and an alternative oscillator circuit for oscillating a signal superimposed on the output signal of the output tuning circuit to alternate the local oscillator circuit , and a monitor circuit for monitoring output a superimposed signal in which the oscillation signal is superimposed alternate oscillation circuit to the output signal of the output tuning circuit.
In the adjustment method, the oscillation signal of the alternative oscillation circuit is adjusted to match the waveform of the output signal of the output tuning circuit based on the superimposed signal output from the monitor, and the oscillation frequency of the local oscillation circuit is adjusted using the adjustment amount . You.
[0047]
Therefore, the oscillation frequency of the local oscillation circuit can be optimally adjusted according to the variation in the tuning characteristics due to the variation in the capacitance of the output tuning circuit during the manufacture of the cable modem tuner, and the processing time during the manufacturing can be reduced. This reduces manufacturing costs.
According to a fourth aspect of the present invention, there is provided a cable modem tuner to which the third aspect of the present invention is applied, wherein an output tuning unit in a UHF system has a primary side and a secondary side tuning unit each having a strip line. The strip lines of the primary-side and secondary-side tuning sections are coupled, and the coupling section is provided with an inductance section.
[0048]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0049]
FIG. 1 is a circuit diagram of a tuner for a cable modem according to an embodiment of the present invention.
[0050]
The B3 band high-frequency amplifier circuit of the cable modem tuner B of FIG. 4 is formed to include a tuning circuit using an air core coil, and the tuner is supplied to the input tuning coil 21, the output tuning coils 37 and 38, and the local oscillation circuit 12 at the time of tuner manufacturing. Although it was necessary to adjust the related resonance coil 47, the tuner A for the cable modem in FIG. 1 uses a B3 band high-frequency amplification tuning circuit to reduce the size and improve the adjustment method. Here, the improvement of the B3 band high-frequency amplification tuning circuit will be specifically described below.
[0051]
The difference between the circuit of the cable modem tuner A of FIG. 1 and that of FIG. 4 is that the high-frequency amplification input and output tuning circuits 3 and 70 of FIG. 70A. The other configuration of FIG. 1 is the same as that of FIG. 4, and the description is omitted here.
[0052]
The high-frequency amplification input and output tuning circuits 3A and 70A of FIG. 1 are different from the high-frequency amplification input and output tuning circuits 3 and 70 of FIG. 4 in that the tuning coils 21, 37 and 38 of FIG. 1A, 37A and 38A, and a coupling coil 52 is added to FIG. Other configurations of the high frequency amplification input and output tuning circuits 3A and 70A in FIG. 1 are the same as those in FIG.
[0053]
In the high frequency amplification input and output tuning circuits 3A and 70A of FIG. 1, the tuning coils 21, 37 and 38 of FIG. 4 are omitted by forming strip lines 21A, 37A and 38A on a printed circuit board together with other circuits of the tuner. You.
[0054]
By forming a tuning circuit including these strip lines, the only coil to be adjusted during tuner manufacturing is the resonance coil 47 related to the local oscillation circuit 12. Note that the strip line can be formed mainly in the B3 (UHF) band, and is difficult in other bands.
[0055]
In FIG. 1, since the tuning coils in the tuning circuit of the B3 band are changed to the printed coils (pattern coils formed on the printed circuit board) of the strip lines 21A, 37A and 38A as described above, variations in the inductors of the coils themselves are obtained. Is minimized. Then, the oscillation frequency of the local oscillation circuit 12 is adjusted to match the variation of the tuning characteristics caused by the variation of the capacitance element such as the diode, the capacitor, and the transistor. That is, a method is adopted in which the oscillation signal of the local oscillation circuit 12 is added to the band-pass characteristic that is the high-frequency amplification characteristic.
[0056]
FIG. 2 is a diagram showing an equipment system for adjusting the oscillation frequency of local oscillation circuit 12 in FIG.
[0057]
In the figure, this equipment system includes a Sweep SG (abbreviation for signal generator) 80, tuner A for cable modem in FIG. 1, IF marker SG81, detector 82, and oscilloscope 83.
[0058]
The output signal of the IF marker SG81 is applied to indicate the position (frequency) of the local oscillation signal on the IF signal instead of the local oscillation signal by the local oscillation circuit 12.
[0059]
The Sweep SG 80 stably oscillates a reference sweep waveform (waveform showing high-frequency amplification characteristics) and supplies the signal to the terminal 1 of the cable modem tuner A.
[0060]
In this case, the local oscillation circuit 12 of the cable modem tuner A is in a stopped state.
[0061]
The sweep waveform given to the cable modem tuner A is output as the test point signal TP of the IF signal at the output stage of the IF amplifier circuit 55 in FIG. 1, and the output signal of the IF marker SG81 is superimposed. The resulting superimposed signal is output by the oscilloscope 83 via the detector 82.
[0062]
At this time, the output of the IF marker SG81 is adjusted while referring to the output of the oscilloscope 83, so that the waveform output by the oscilloscope 83 does not vary and only the waveform of the IF signal is obtained. Since the oscillation frequency of the local oscillation circuit 12 is uniquely determined based on the output adjustment amount of the IF marker SG81 at this time, the variation in the tuning characteristics due to the variation in the capacitance of the diode, capacitor, transistor, etc. of the tuning circuit is eliminated. Twelve oscillation frequencies can be adjusted and absorbed.
[0063]
In the tuner for the cable modem of FIG. 1, the coupling coil 52 is provided in order to suppress the variation of the pass bandwidth, which is the coupling waveform of the high-frequency amplified waveform of the B3 band.
[0064]
FIG. 3 is a detailed circuit diagram of the coupling coil 52 of FIG. 1 and its vicinity. In the figure, the coupling coil 52 is configured by connecting the printed inductors 60 in parallel to each other or connecting the printed inductor 60 and the chip inductor 61 in parallel to the coupling portion of the strip lines 37A and 38A. Note that a printed inductor is an inductor formed by a printed coil. A chip inductor is a printed coil formed on a chip.
[0065]
The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a tuner for a cable modem according to an embodiment of the present invention.
FIG. 2 is a diagram showing an equipment system for adjusting an oscillation frequency of a local oscillation circuit 12 in FIG.
FIG. 3 is a detailed circuit diagram of the coupling coil 52 of FIG. 1 and its vicinity.
FIG. 4 is a circuit diagram of a tuner for a cable modem for explaining the background of the present invention.
[Explanation of symbols]
18-20 Input signal switching circuits 3-5 and 3A High frequency amplification input tuning circuits 6-8 High frequency amplifiers 70-72 and 70A High frequency amplification output tuning circuits 9-11 Mixing circuits 12-14 Local oscillation circuits 21A, 37A and 38A Stripline In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (4)

An input unit that receives a multi-wave received signal, selects and outputs the received signal to any of a plurality of different frequency bands including UHF,
An input tuning unit that has a first inductance element, and tunes each reception signal selected and output at the input unit to a desired frequency by the first inductance element in each system and outputs the same;
An amplification unit that amplifies the output signal of each input tuning unit in each system,
An output tuning unit that has a second inductance element and tunes the output signal of each of the amplifying units to the desired frequency by the second inductance element in each system and outputs the signal;
And a frequency converter for converting an output signal of the respective output tuning unit to each signal of a desired intermediate frequency in the respective systems,
It said first and second inductance elements in the UHF of SYSTEM COMPONENTS CAN Do the stripline,
The frequency conversion unit in the UHF system includes a local oscillation circuit that oscillates at a predetermined frequency using a resonance coil, an oscillation signal of the local oscillation circuit, and an output signal of the output tuning unit. And a mixing circuit that converts and outputs the
It said local predetermined frequency of the oscillator circuit is characterized frequencies der Rukoto capable of absorbing variations in the tuning characteristics, cable modem tuner. The output tuning section in the UHF system includes a primary side tuning section and a secondary side tuning section each having the stripline,
The tuner for a cable modem according to claim 1, wherein the strip lines of the primary-side and secondary-side tuning units are coupled, and the coupling unit is provided with an inductance unit. A method for adjusting a tuner for a cable modem,
The cable modem tuner,
An input unit that receives a multi-wave received signal, selects and outputs the received signal to any of a plurality of different frequency bands including UHF,
An input tuning unit that has a first inductance element, and tunes each reception signal selected and output at the input unit to a desired frequency by the first inductance element in each system and outputs the same;
An amplification unit that amplifies the output signal of each input tuning unit in each system,
An output tuning unit that has a second inductance element and tunes the output signal of each of the amplifying units to the desired frequency by the second inductance element in each system and outputs the signal;
A frequency converter for converting the output signal of each output tuning unit into a signal of a desired intermediate frequency in each system ,
The first and second inductance elements in the UHF system are made of strip lines,
The frequency conversion unit in the UHF system includes a local oscillation circuit that oscillates at a predetermined frequency using a resonance coil, an oscillation signal of the local oscillation circuit, and an output signal of the output tuning unit. And a mixing circuit that converts and outputs the
The predetermined frequency of the local oscillation circuit is a frequency capable of absorbing a variation in tuning characteristics,
The cable modem tuner further includes an equipment system for adjustment,
The equipment system is the UHF system,
An alternative oscillation circuit that oscillates a signal superimposed on an output signal of the output tuning circuit instead of the local oscillation circuit,
And a monitor circuit for monitoring output a superimposed signal in which the oscillation signal is superimposed in the alternate oscillating circuit to an output signal of the output tuning circuit,
Wherein in the adjusting method, the oscillation signal of the alternate oscillation circuit is adjusted to match the waveform of the output signal of the output tuning circuit based on the superimposition signal to be monitored output of the local oscillator circuit using the adjustment amount and adjusting the oscillation frequency, Quai Burumodemu tuner adjustment method. The output tuning unit in the UHF system includes a primary side tuning unit and a secondary side tuning unit each having the strip line;
4. The method of claim 3, wherein the strip lines of the primary-side and secondary-side tuning units are coupled, and the coupling unit is provided with an inductance unit. 5.

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