JP2991112B2 - Transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a transmitter, and more particularly to a television signal transmitter using a digital modulation amplifier as a main amplifier.

[0002]

2. Description of the Related Art A television signal transmitter using a conventional digital modulation amplifier as a main amplifier corresponds to each bit value of n-bit digital data obtained by converting a television signal into a digital signal. N RFs whose output power is specified by a power of 2
An amplifier and n RF amplifiers for cutting off or passing the input of each RF amplifier according to the value of each bit of the digital data.
A double sideband (DSB) signal extracted from a digital modulation amplifier including a switch and a combiner that combines the output signals of the respective RF amplifiers and outputs a combined signal in both sidebands is converted into a residual sideband by an output filter. And configured to transmit the output signal of the output filter. Here, the pass frequency characteristic of the output filter indicates a residual sideband characteristic of an existing terrestrial television broadcast signal as shown in FIG.

[0003]

However, in the above-mentioned conventional transmitter, an output filter having a vestigial sideband characteristic shown in FIG. 3 is required at the last stage of the transmitter. Has large power, so its outer dimensions are large,
There is a problem that the price is expensive and the insertion loss is large.

[0004] The present invention has been made in view of the above points,
An object of the present invention is to provide a small and inexpensive transmitter.

[0005]

In order to achieve the above object, a first aspect of the present invention is directed to a first aspect of the present invention, wherein each output power is defined by a power of 2 corresponding to n-bit digital data. Amplifiers, n switches individually provided on the input side or the output side of the n amplifiers, and switching controlled according to the value of each bit of the n-bit digital data, amplifiers and switches having n systems Having a digital modulation amplifier as a main amplifier, which synthesizes a transmission carrier taken out through the serial transmission path and outputs a modulated wave obtained by modulating the transmission carrier with n-bit digital data,
A transmitter for transmitting a modulated wave in a vestigial sideband, comprising: a first band component serving as a both sideband region of the vestigial sideband of n-bit digital data; and a predetermined amount with respect to the first band component. A first digital filter having a characteristic of outputting a second band component which becomes a single sideband region of the attenuated residual sideband, and a single sideband region of a residual sideband of n-bit digital data. A second digital filter having a characteristic of extracting a band component and attenuating and outputting the same by a predetermined amount;
A local oscillation frequency signal generating means for generating first and second local oscillation frequency signals having different phases by 0 ° and having the same frequency, and output signals of the first and second digital filters to first and second digital filters. The local oscillation frequency signals are separately multiplied and then combined to form the first and second local oscillation frequency signals.
Signal generating means for outputting a signal having a residual sideband characteristic having a carrier frequency equal to the wave number, an amplitude suppressing circuit for suppressing the amplitude of an output signal of the signal generating means and extracting phase information, and an amplitude suppressing circuit Frequency conversion and distribution means for frequency-converting the frequency of the output signal to the transmission carrier frequency and distributing it into n and inputting them to a serial transmission line of an amplifier and a switch having n systems of digital modulation amplifiers; An envelope detection circuit for extracting the amplitude information, and a generator for generating a control code for controlling the switching of the n switches independently of each other based on an output signal of the envelope detection circuit; It is configured to output a modulated wave in the vestigial sideband.

According to the present invention, the vestigial sideband modulator, which has conventionally been constituted by an amplitude modulator and a subsequent filter, is constituted by an amplitude modulation circuit and a signal processing circuit in the preceding stage, and is combined with a digital modulation amplifier. There is a feature. The present invention utilizes the fact that the modulated wave in the vestigial sideband is composed of a double sideband region and a single sideband region, of which the single sideband region is only on one side with respect to the carrier wave, thereby causing phase distortion. doing.

That is, the output signals of the first and second digital filters differ in phase by 90 ° from each other, and
Synthesized from multiplying separately with first and second local oscillation frequency signal of the same frequency, residual <br/> the same frequency as that of the first and second local oscillator frequency signal and the frequency of the carrier wave The signal of the residual sideband characteristic is output once, and the signal of the residual sideband characteristic is divided into an amplitude component and a phase component. The amplitude component is used to control the n switches of the digital modulation amplifier independently of each other. And the phase component is used for a carrier wave to obtain a finally required residual sideband signal. According to the present invention, signal amplification and modulation are simultaneously performed by the digital modulation amplifier, and the vestigial sideband signal of the analog signal can be output therefrom.

[0008] In a second aspect of the present invention, n
N amplifiers whose output power is specified by a power of 2 corresponding to the digital data of bits, and each bit of the digital data of n bits respectively provided on the input side or the output side of the n amplifiers N switches controlled in accordance with the value of the above, and a transmission carrier extracted through a series transmission line of n systems of amplifiers and switches is combined to output a modulated wave obtained by modulating the transmission carrier with n-bit digital data. A transmitter for transmitting modulated waves in the vestigial sideband, comprising two sets of parallel digital modulation amplifiers as main amplifiers, and a first and second sideband region of the vestigial sideband of the n-bit digital data. And a first digital filter having characteristics that attenuate the second band component, which is a single sideband region of the vestigial sideband, with respect to the first band component, and output them. A second digital filter having a characteristic of extracting and attenuating and outputting a band component which is a single sideband region of a residual sideband of n-bit digital data; and an output signal of the first digital filter. On the basis of,
A first generator for generating a control code for independently controlling the n switches in one of the two sets of digital modulation amplifiers, and an output signal of the second digital filter; A second generator for generating a control code for independently controlling the n switches in the other one of the two sets of digital modulation amplifiers; and two sets of transmission carriers that are 90 ° out of phase with each other. It is characterized by having carrier input means for separately inputting to a digital modulator, and a synthesizer for synthesizing output signals of two sets of digital modulation amplifiers and outputting a modulated wave in a residual sideband.

According to the present invention, the band component in the double sideband region and the band component in the single sideband region in the vestigial sideband characteristics are separated, each is quadrature-modulated by two sets of digital modulation amplifiers, and then synthesized by a synthesizer. By doing so, a modulated wave in the vestigial sideband is output. Therefore, also in the present invention, signal amplification and modulation are simultaneously performed by the digital modulation amplifier, and the vestigial sideband signal can be output from the combiner.

[0010]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a first embodiment of a transmitter according to the present invention. In the figure, n obtained by converting a television signal into a digital signal
The bit baseband digital data is input to digital filters 3 and 4 via an input terminal 1, respectively. On the other hand, the clock signal input to the input terminal 2 is distributed and supplied to each circuit unit by the clock distributor 6.

The digital filter 3 converts a signal (low-frequency component) corresponding to the double sideband region II in the residual sideband signal composed of the lower sideband region I and the double sideband region II shown in FIG. On the other hand, it has the frequency characteristic of FIG. 5A in which a signal (high-frequency component) corresponding to the lower sideband region I is attenuated by 6 dB and output.

The digital filter 4 extracts a high-frequency component of the television signal corresponding to the lower sideband region I of FIG. 3 and attenuates it by 6 dB and outputs the same. The frequency characteristic shown in FIG. Having. Each output signal of the digital filters 3 and 4 is supplied to one input terminal of each of multipliers 7 and 8 provided correspondingly.

On the other hand, a station oscillated and output by the oscillator 5
The partial oscillation frequency signal is phase-shifted by 90 ° by the 90 ° phase shifter 10 and supplied to the other input terminal of the multiplier 8 as a second carrier, while the delay unit 9 delays the time by the 90 ° phase shifter 10. Is supplied to the other input terminal of the multiplier 7 as a first carrier. The signals obtained by the multiplication by the multipliers 7 and 8 are supplied to the adder 11 where they are added and synthesized. As a result, the local oscillation frequency _fIF is a carrier wave, and high-frequency components in the baseband are canceled in the upper sideband around the carrier wave, and high-frequency components are added in the lower sideband. A signal having the residual sideband characteristics shown in FIG.

The signal of the residual sideband output from the adder 14 is input to the envelope detection circuit 12 and the amplitude suppression circuit 13, respectively. The amplitude suppression circuit 13 suppresses the amplitude of the signal in the residual sideband, extracts only the phase component, converts the phase component into an analog signal by the D / A converter 14, and further removes unnecessary frequency components by a band filter (not shown). And supplies it to the frequency converter 15. Frequency converter 15 and a frequency conversion between the frequency and the local frequency of the input signal, after frequency conversion of the frequency of the output signal of the D / A converter 14 into RF carrier f _T of the transmission frequency band, divider 16
Respectively supply the RF switch 18 ₁ ~ 18 _n through.

On the other hand, the envelope detector 12 extracts the amplitude component by performing envelope detection on the input residual sideband signal, and supplies the amplitude component to the amplitude control code generator 17 at the next stage, where the amplitude control code is output. Convert to The amplitude control code controlling switching n number of RF switches 18 ₁ ~ 18 _n. R
The F switches 18 ₁ to 18 _n correspond to one-to-one and have n RFs.
Because it is connected to an input terminal of the amplifier 19 ₁ ~19 _n,
With the above switching, the n RF amplifiers 19 ₁ to 19 ₁ to
The _19n input is turned on or off. Here, the n RF amplifiers 19 _{1 to} 19 _n are arranged such that their output powers (gains) are defined by powers of 2 corresponding to n-bit digital data.

The output signals of the RF amplifiers 19 _{1 to} 19 _n are 3
They are respectively synthesized by dB combiner 20 ₁ to 20 _m. That is, a series transmission line composed of the RF switch 18 _k and the RF amplifier 19 _k (where k = 1, 2,..., N) has n
The transmission carrier waves extracted through these transmission paths are combined in 3 dB, and the transmission carrier frequency f _T is output from the 3 dB combiner 20 _m as shown in FIG. A vestigial sideband signal amplitude-modulated with data (video signal) is extracted. The vestigial sideband signal is an analog signal.

In the residual sideband signal, the information of the lower sideband region I is used as the upper sideband region III,
Is the same frequency spectrum as an existing terrestrial television broadcast signal in which the double sideband area IV is set as the information. This residual sideband signal is supplied to the output filter 21, where the higher harmonic components are suppressed and output to the output terminal 22, and further transmitted through the transmission means.

According to this embodiment, the vestigial sideband signal is a composite wave of the carrier wave p and the modulated wave s in the double sideband region as shown in FIG. Although the phase changes, the phase is constant, but in the lower sideband region, as shown in FIG. 4B, the phase changes according to the information in the composite wave of the carrier p and the modulation wave s. Focus on RF
Amplifiers 19 ₁ ~ 19 _n front in separately the amplitude and phase components of the VSB signal processing, RF amplifier 1 in amplitude component
9 ₁ performed ~ 19 _n input on / off control of, by phase component is reflected in the RF carrier, via an RF amplifier input is turned on synthesized by 3dB combiner 20 ₁ to 20 _m, As a result, the residual sideband characteristics can be obtained from the final 3 dB combiner 20 _m .

Therefore, an output filter for obtaining a residual sideband signal from a double sideband signal in the last stage as in the prior art can be dispensed with (the output filter 21 in FIG. 1 is simply a filter for suppressing harmonics). This is different from the conventional output filter), and the configuration can be made cheaper and smaller than the conventional one.

Next, a second embodiment of the present invention will be described. FIG. 2 shows a block diagram of a second embodiment of the present invention. In the figure, the same components as those of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 2, FIG.
The output signal of the digital filter 3 having the characteristic shown in FIG. 5 is supplied to the control code generator 25, and the output signal of the digital filter 4 having the characteristic shown in FIG. Is done.

On the other hand, the RF output from the oscillator 27
The carrier is passed through the delay unit 9 and the distributor 29, respectively.
Each of the RF switches 31 _{1 to} 31 _n is input in parallel as a first carrier. The RF carrier oscillated and output from the oscillator 27 is supplied to the 90 ° phase shifter 10 and the splitter 3.
0, and is input in parallel to each of the _n RF switches 32 _{1 to} 32 _n as a second carrier. The RF switches 31 _{1 to} 31 _n use the output control code of the control code generator 25 to control the low-frequency component of the n-bit digital data corresponding to the double sideband area of the residual sideband signal shown in FIG. The high-frequency component of the n-bit digital data corresponding to the lower sideband region is on / off controlled in accordance with the value of each bit of the data whose 6 dB has been attenuated.

The first carrier output through the turned on RF switch among the RF switches 31 _{1 to} 31 _n is:
After being amplified is input to the RF amplifiers corresponding among the n RF amplifier 33 ₁ ~ 33 _n, are each 3dB synthesized is input to one input terminal of the 3dB combiner 37 by the combiner 35 ₁ to 35 _m You.

On the other hand, the RF switches 32 _{1 to} 32 _n operate according to the output control code of the control code generator 26 to generate n-bit digital data corresponding to the lower sideband region of the vestigial sideband signal shown in FIG. Is turned on / off in accordance with the value of each bit of the data in which the high-frequency component is attenuated by 6 dB. RF
The second carrier output through the RF switch turned on among the switches 32 _{1 to} 32 _n is input to the corresponding RF amplifier among the _n RF amplifiers 34 _{1 to} 34 _n , amplified, and then combined. 3 dB each by the unit 36 _{1 to} 36 _m
The signals are synthesized and input to the other input terminal of the 3 dB synthesizer 37. The combined signal output from the 3 dB combiner 37 has the residual sideband characteristic shown in FIG. 3B, and after the output filter 21 suppresses the higher harmonic components, the output terminal 2
2 is transmitted.

In this embodiment, the vestigial sideband characteristics
And modulates the modulated wave with the filter characteristics shown in FIG.
The obtained low-frequency component and high-frequency component are shown in FIG.
It is separated into the high-frequency components obtained by the filter characteristics and
The first and second carriers each having a phase difference of 90 ° from each other.
After orthogonally modulating the transmission waves and combining them, the combiner 3
5_mFrom this, a signal having a frequency characteristic as shown in FIG.
Take out, synthesizer 36_m As shown in FIG. 6 (b)
The signal of the frequency characteristic is taken out, and these are
7, the high band of the lower sideband after modulation
The components are canceled, and the upper band adds the respective high frequency components.
Then, the residual sideband signal having the frequency characteristic shown in FIG.
No. can be obtained.

Therefore, according to the present embodiment, an output filter for obtaining a residual sideband signal from a double sideband signal in the last stage as in the conventional case can be omitted, so that it is inexpensive and compact as compared with the conventional case. It can be configured.

Note that the present invention is not limited to the above-described embodiment. For example, the RF switches 18 ₁ to 18 _n ,
31 _{1 to} 31 _n 32 _{1 to} 32 _n are RF amplifiers 19 _{1 to} 19
_{n, 33 1 ~33 n, 34} 1 ~34 n may be provided on the output side of the.

[0027]

As described above, according to the present invention,
Signal amplification and modulation are performed simultaneously by the digital modulation amplifier by the signal processing at the previous stage of the digital modulation amplifier,
Further, since the vestigial sideband signal can be output from this, the high output for obtaining the vestigial sideband signal which is provided in the subsequent stage of the amplitude modulator (the last stage of the transmitter) as in the related art is provided. Therefore, an expensive and large output filter corresponding to the above can be dispensed with, so that the transmitter can be configured to be inexpensive and small in size as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a characteristic diagram of a vestigial sideband signal.

FIG. 4 is an explanatory diagram of components of residual sideband characteristics.

FIG. 5 is a diagram showing characteristics of the digital filter in FIGS. 1 and 2;

FIG. 6 is a diagram showing filter characteristics after modulation in FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Digital data input terminal 2 Clock signal input terminal 3 First digital filter 4 Second digital filter 5, 27 Oscillator 7, 8 Multiplier 9 Delayer 10 90 ° phase shifter 11 Adder 12 Envelope detector 13 Amplitude Suppression circuit 14 D / A converter 15 frequency converter 16, 29, 30 distributor 17 amplitude control code generator 18 ₁ to 18 _n , 31 _{1 to} 31 _n , 32 _{1 to} 32 _n RF switch 19 _{1 to} 19 _{n 33 1 ~33 n, 34 1 ~34} n RF amplifier _{20 1 ~20 m, 35 1 ~35} n, 36 1 ~36 n, 37
3 dB synthesizer 21 output filter 22 output terminal 25, 26 control code generator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 5/38-5/46 H03C 1/00-1/62 H04B 1/68 H04L 27/02

Claims (3)

(57) [Claims] 1. An n-number of amplifiers each having an output power defined by a power of 2 corresponding to n-bit digital data, and the n-number of amplifiers being individually provided on an input side or an output side of the n-number of amplifiers. n switches that are switched and controlled in accordance with the value of each bit of the n-bit digital data, and a transmission carrier extracted through a serial transmission path of the n amplifiers and switches, and combining the transmission carrier with the n Having as a main amplifier a digital modulation amplifier that outputs a modulated wave modulated with bits of digital data,
A transmitter for transmitting a modulated wave of a vestigial sideband, comprising: a first band component which is a double sideband region of the vestigial sideband of the n-bit digital data; A first digital filter having a characteristic of outputting a second band component that is a single sideband region of the residual sideband attenuated by a predetermined amount, and a single digital filter of the residual sideband of the n-bit digital data. A second digital filter having a characteristic of extracting a band component to be a sideband region and attenuating the output by a predetermined amount, and a first and second local oscillators having a phase difference of 90 ° from each other and the same frequency. Local oscillation frequency for generating frequency signal
Signal generating means; separately multiplying the output signals of the first and second digital filters with the first and second local oscillation frequency signals and synthesizing the first and second local oscillation frequencies; Signal
A signal generation unit that outputs a signal having a residual sideband characteristic having the same frequency as the frequency of the carrier wave; an amplitude suppression circuit that suppresses the amplitude of an output signal of the signal generation unit and extracts phase information; Frequency conversion and distribution means for converting the frequency of the output signal of the suppression circuit into the transmission carrier frequency, distributing it to n, and inputting it to the serial transmission line of the amplifier and the switch having n systems of the digital modulation amplifier; An envelope detection circuit for extracting amplitude information of an output signal of the generation means, and a generator for generating a control code for controlling switching of the n switches independently of each other based on an output signal of the envelope detection circuit. And a modulated wave in the vestigial sideband is output from the digital modulation amplifier. 2. An n-number of amplifiers each having an output power defined by a power of 2 corresponding to n-bit digital data, and said amplifiers individually provided on the input side or output side of said n number of amplifiers. n switches that are switched and controlled in accordance with the value of each bit of the n-bit digital data, and a transmission carrier extracted through a serial transmission path of the n amplifiers and switches, and combining the transmission carrier with the n A transmitter for transmitting a modulated wave in a vestigial sideband, comprising two sets of digital modulation amplifiers for outputting a modulated wave modulated by digital data of bits in parallel as main amplifiers, and transmitting the modulated wave in the residual sideband. A first band component serving as a double sideband region of the vestigial sideband, and a second band serving as a single sideband region of the vestigial sideband attenuated by a predetermined amount with respect to the first band component. A first digital filter having a characteristic of outputting each component, and a characteristic of extracting a band component which is a single sideband region of the residual sideband of the n-bit digital data, and attenuating the band component by a predetermined amount for output. Based on the output signal of the first digital filter,
A first generator for generating a control code for controlling the n switches in one of the two sets of digital modulation amplifiers independently of each other, and an output signal of the second digital filter. On the basis of,
A second generator for generating a control code for independently controlling the n switches in the other one of the two sets of digital modulation amplifiers; and transmitting the transmission carriers having a phase difference of 90 ° from each other. Carrier input means for separately inputting the two sets of digital modulators; and a synthesizer for synthesizing output signals of the two sets of digital modulation amplifiers and outputting a modulated wave in the residual sideband. Features transmitter. 3. The transmitter according to claim 1, wherein the modulated wave in the residual sideband is a modulated wave in the residual sideband standardized by an existing television system.