JPS58162155A - Driving circuit for linear modulator - Google Patents

Abstract

PURPOSE:To suppress out-band spurious at the ON/OFF gate operation of a differential driving type linear modulator, by controlling driving current into a driving circuit for the modulator by a gate signal passed through a low-pass filter. CONSTITUTION:A modulating signal is inputted from a terminal 11 to the driving circuit 1 including a differential amplifier and a differential signal 13 outputted from the circuit 1 is inputted to the differential driving type linear modulator 2 to modulate a carrier wave from a local oscillator 5. An ON/OFF gate signal is inputted from a terminal 15 to a current supplying circuit 3, which supplies driving current to the driving circuit 1. In the current supplying circuit 3, the driving current is controlled by a signal obtained by limiting the ON/OFF gate signal at its band through the low-pass filter 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a drive circuit for a differential drive type modulator that sends out a burst-like modulation signal waveform at high speed.

When using a pulse code modulated signal by time division multiplexing, the modulating signal is turned on/off to obtain a burst signal.
Requires a 0N10FF gate circuit that turns off. This 0N10FF gate circuit requires the following performance.

(2) A sufficient 0N10FF ratio can be obtained.

(2) Ability to perform high-speed switching at a speed comparable to the speed of the clock signal of the transmission signal.

■Do not emit spurious signals outside the band.

■It must be easy to drive.

Conventionally, this type of gate circuit has been configured using a diode or the like as a switching element, and a method has been adopted in which the modulated signal wave is 0N10'FF.

However, with this method, as the frequency of the carrier wave increases, the circuit required to obtain the required performance becomes more complex, and it is difficult to control the speed of the switch. The disadvantage of this method is that it generates spurious signals outside the band during operation.

The present invention has been made in view of the above-mentioned conventional circumstances.
Therefore, an object of the present invention is to provide a function to drive the modulator according to a data signal when a differentially driven linear modulator is used as a modulator, and an o1 that can easily control the 0N10FF waveform.
It is an object of the present invention to provide a novel differential drive type linear modulator drive circuit which can eliminate the above-mentioned drawbacks of the conventional art by having a q10rF gate function.

The above object of the present invention is to provide a linear modulator drive circuit including a differential amplifier and a current supply circuit for supplying current to the differential amplifier, in which the current supply circuit includes a low-frequency f-wave amplifier and a band-limited This is achieved by a linear modulator drive circuit comprising a circuit for generating a drive current and supplying the band-limited drive current waveform to the differential amplifier.

Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a block diagram showing the concept of the present invention, and FIG. 2 shows signal waveforms of each part. The modulation signal is input from the modulation signal input terminal // to the drive circuit / including a differential amplifier, where it is converted to a differential signal output / /3,
Drives a differentially driven linear modulator λ. Here, the carrier wave supplied from the local oscillator S is linearly modulated and output from the modulator output terminal/da.

On the other hand, the 0N10FF gate signal is input from the gate signal input terminal 15 to the current supply circuit 3, and controls the supply of the differential amplifier included in the drive circuit connected thereto. When the 0N10FF gate is ON, a constant current is supplied to the above-mentioned differential amplifier, so the modulator is driven by the differential signal output obtained according to the modulation input signal. When the ON/OFF gate signal is OFF, the current supplied to the differential amplifier described above becomes O, and the output terminal of the drive circuit /, 2. A voltage equal to /3 is supplied.

That is, the difference signal (/2)-(/,?) in FIG. 1 becomes Ov, and the output signal of the differential drive type modulator driven thereby becomes OFF. At this time, if the 0N10FF of the gate signal is sharply applied, the spectrum outside the band will expand, causing interference to other channels. therefore,
Here, the output of the current supply circuit 3 is oN10 of the gate signal.
If the tr signal is waveform-shaped by an appropriate low-frequency r wave generator to become a current /6, the output terminal of the modulator /
The envelope of the 0N10FF waveform can be controlled arbitrarily, and by only slightly slowing down the switching speed, it is possible to prevent spectrum expansion outside the band.

FIG. 3 shows an embodiment of the present invention in which the block configuration of FIG. 1 is detailed. The emitter terminals of each of the transistors 3/32 are connected in common at terminal N, thereby forming a differential amplifier.

The modulation signal input to the input terminal // of this differential amplifier is converted into a differential signal by this differential amplifier and outputted, and is then passed through a buffer transistor, 33.3Q, to a differential drive type modulator.
The carrier wave signal from the local oscillator S is linearly modulated and output from the modulator output terminal /4'.

On the other hand, the gate signal is input from the terminal /j and is sent to the current supply circuit 3 of the differential amplifier via the left buffer transistor 3.
guided by. In this circuit 3, after the gate signal is waveform-shaped by an appropriate low-frequency P wave device, the resistor J9. IIO
, 'l/, is input to the voltage-current conversion circuit consisting of the transistor 36, and is a current /6 proportional to the output voltage of the low-frequency r-wave generator.
Convert to This output current /6 is connected to the common emitter terminal 23 of the differential amplifier and connects the differential amplifier to 0N10FF.
do. When OFF, the output voltage of the differential amplifier is equal to the potential of the power supply terminal /9, so the output voltage of the buffer transistor is /2. The potentials of /3 also become equal. That is, the modulator λ
The differential input terminal voltage becomes OV, and no carrier wave is output from the modulator. When turned on, the differential amplifier operates as a normal drive circuit unless it is turned on.

In the current supply circuit 3, the insertion location of the low-frequency f-wave device used to control the 0N10F filtration transient response is shown in Figure 4 (
Even if the structure is modified as shown in a) or (b), the same effect as described above can be obtained. Note that the low-frequency f-wave device in the case of FIG. 4(a) can be realized using seven coils.

In the above description, for the sake of simplicity, only a U-phase modulator and a driving circuit have been described, but the present invention can be similarly implemented when driving a D-phase or multi-phase modulator.

From the above, when using a differential amplification type modulator, the gate signal is appropriately band-limited from the current supply circuit to the drive circuit [-
By supplying a high current, it is possible to obtain a signal with a fast rise and no out-of-band spurious,
This has the effect of omitting the RF gate circuit that was conventionally necessary.

[Brief explanation of drawings]

FIG. 7 is a block diagram showing the concept of the present invention, FIG. It is a figure showing a modification. l...drive circuit, co...differential drive type linear modulator, 3
. . . current supply circuit, da . . . low frequency f wave generator, j . . . local oscillator, // . /3
...Modulator drive signal terminal, /da...Modulator output terminal, /j...Gate signal input terminal, /F...Differential amplifier supply current, /7...Bias terminal, /9 ,20. Edge...Power supply terminal, -...Gate signal buffer output terminal1. ? / +-32...Differential amplifier transistor, 3
3,3Q...Buffer transistor, 35...Gate signal buffer transistor, 36...Current supply transistor, 3'), 31;, 39.4IO, da/,
invasion, t3. qtei, gs...resistance, ri6...diode. Patent applicant: NEC Corporation Representative: Patent attorney Yutabe Kumagai 7- Figure 2 29

Claims (1)

[Claims] A linear modulator drive circuit including a differential amplifier and a current supply circuit that supplies current to the differential amplifier, wherein the current supply circuit includes a low-frequency f-wave generator and a circuit that generates a band-limited drive current. A linear modulator drive circuit comprising: a linear modulator drive circuit that supplies the band-limited drive current waveform to the differential amplifier.