JPH09232924A - Nonlinear line equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the trailing time of an input signal by using a fact that a propagation speed of a signal traveling wave propagating through a gate transmission line and a drain transmission line of a travelling wave transistor(TR) is decreased as a trans-conductance of the TR increases. SOLUTION: An input signal is given to an input terminal of a gate electrode transmission line T2 by a voltage signal source Vin . This signal propagates on the gate electrode transmission line T2 as a travelling wave and two transmission modes are induced in a drain electrode transmission line T1. In the c-mode, as a trans-conductance gm increases, a propagation speed Vc of the travelling wave on both electrode transmission lines slows down. Thus, a principle that as the trans-conductance gm increases, the propagation speed Vc of the travelling wave on both electrode transmission lines slow down is utilized. Thus, the trailing time of the input signal is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming an ultra high speed digital circuit.

[0002]

2. Description of the Related Art 100G has been sought after for optical communication technology.
When configuring a bit / s super high-speed digital circuit,
To evaluate the circuit, a signal containing a high frequency component is required, but the lack of a signal source for generating the signal containing the high frequency component is now a big problem.

Conventionally, a non-linear line device using a non-linear capacity of a Schottky diode is known as the signal source (MJW Rodwell, M. Kamegawa, R. Yu, MC.
ase, E. Carman and K. Giboney, "GaAs nonlinear tansmi
ssion lines for picosecond pulse generation and mi
llimeter-wave sampling ", IEEE Trans. MTT-39, no7, p
p.1194-1204, July 1991.). This non-linear line device,
The function of the signal source is fulfilled by the following principle.

First, the capacitance C _d (V) of the Schottky diode
Is given by the following equation (1). C _d (V) = C _j0 / {1- (V / φ)} ^1/2 (1) where V is the reverse bias voltage between the two terminals of the diode, and φ is the Schottky barrier voltage. , C _j0 are capacitance values at zero bias.

The non-linear line has a structure in which the Schottky diodes are connected in series via a transmission line. With this structure, the propagation velocity v of the traveling wave on the transmission line is given by the following equation (2). v = 1 / {LC _d (V)} ^1/2 (2) From this equation (2), the larger the reverse bias voltage V between the two terminals of the diode, the slower the propagation speed v of the traveling wave.

FIG. 7 is a diagram for explaining the operation of the conventional non-linear line device using the voltage variable capacitance of the Schottky diode.

In the conventional nonlinear line device, as shown in FIG.
The input signal shown in (1) is output with the waveform shown in FIG. 7 (2). That is, the reverse bias voltage V between the two terminals of the diode
Is higher (the peak value of the waveform), the propagation speed v of the traveling wave is slower. On the other hand, the lower the reverse bias voltage V between the two terminals of the diode (the bottom value of the waveform), the higher the propagation speed v of the traveling wave is. Therefore, when the falling portion of the input signal propagates through the line, the bias voltage is high near the peak of the waveform that is input earlier, so the propagation speed v is slower and the bias voltage is low near the bottom of the waveform that is input slowly. Therefore, the transmission speed v becomes faster, and therefore the difference between the falling start time of the output waveform and the falling end time of the output waveform becomes relatively shorter than that of the input waveform.
The fall time of the output waveform is shortened.

[0008]

However, the above-mentioned conventional non-linear line device using the Schottky diode generally has a large device scale and is difficult to manufacture. Further, in the above-mentioned conventional non-linear line device using the Schottky diode, since the Schottky diodes are discretely arranged, a low-pass filter is parasitically configured, and its cutoff frequency is low. There is a problem that the operation is rate-controlled. Further, since it is composed of only passive circuit elements, there is a problem in that it is not possible to compensate for the loss that the signal receives as the signal propagates.

The present invention is to provide a non-linear line device capable of compacting the device scale, removing the cutoff frequency, and compensating for the loss when the fall time of the input signal is shortened. It is intended.

[0010]

According to the present invention, the propagation speed of a signal traveling wave propagating through a gate transmission line and a drain transmission line of a traveling wave type transistor decreases with an increase in the transconductance g _m of the transistor. Is used to shorten the fall time of the input signal.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a non-linear line device LS1 which is an embodiment of the present invention, in which a traveling wave transistor, an input signal source and a terminating resistor are viewed from above. It is a simplified diagram.

The nonlinear line device LS1 has a traveling wave transistor, termination resistance values R ₁ , R ₂ , R ₃ and R ₄ , and DC voltages V _dd and V _gg .

The traveling wave transistor is composed of a drain electrode transmission line T1, a gate electrode transmission line T2, and a source electrode transmission line T3. The source electrode transmission line T3 is grounded.

Further, the termination resistance values R ₁ , R ₂ , R ₃ , R ₄
Is the termination resistance value connected to the input / output terminal of each electrode transmission line. The DC voltage V _dd is a DC voltage that pulls up the terminal of the drain electrode transmission line T1, and the DC voltage V _gg is a DC voltage that pulls down the terminal of the gate electrode transmission line T2.

At the input end of the gate electrode transmission line T2, an input signal is given by the voltage signal source V _in . This input signal propagates on the gate electrode transmission line T2 as a traveling wave, and upon receiving this input signal, a voltage wave is induced on the drain electrode transmission line T1 by the operation of the field effect transistor, and the drain electrode transmission line T1. Propagate over T1.

Here, due to the action of the mutual capacitance C _m and the mutual inductance L _m existing between the drain electrode transmission line T1 and the gate electrode transmission line T2, the drain electrode transmission line T1 and the gate electrode transmission line T2 are connected to each other. Two modes of propagation are induced. Here, the first propagation mode is expressed as a c mode and the second propagation mode is expressed as a π mode.
In the following description, the c-mode will be focused on. propagation velocity v _c of the c-mode, the self-capacitance C ₂ of the drain electrode transmission line T1, the self capacitance C ₁ of the gate electrode transmission line T2, the self-inductance L ₂ of the drain electrode transmission line T1, the self-inductance of the gate electrode transmission line T2 It is expressed as follows using L ₁ , mutual inductance L _m , mutual capacitance C _m , and transistor transconductance g _m . v _c = ω / I _m (γ _c (ω)) Note that I _m indicates an imaginary part, and γ _c
Is the propagation constant in c-mode.

FIG. 2 is a diagram showing an equivalent circuit of the drain electrode transmission line T1 and the gate electrode transmission line T2 in the above embodiment.

In this equivalent circuit, the self-capacitance C ₁ and self-inductance L ₁ of the gate electrode transmission line T2, the self-capacitance C ₂ and self-inductance L _{2 of} the drain electrode transmission line T1, the drain electrode transmission line T1 and the gate electrode transmission line T1. A transconductance g _m is further provided on the drain electrode transmission line T1 as a mutual capacitance C _m existing between the drain electrode transmission line T1 and the drain electrode transmission line T1 and a mutual inductance L _m existing between the drain electrode transmission line T1 and the gate electrode transmission line T2. To construct a mathematical model of the traveling wave transistor.

The transmission equation of this system is as follows, where V ₁ is the voltage on the gate electrode transmission line T2, I ₁ is the current, V ₂ is the voltage on the drain electrode transmission line T1, and I ₂ is the current. To do. _{- (dV 1 / dx) =} Z 1 I 1 + Z m I 2 - (dV 2 / dx) = Z m I 1 + Z 2 I 2 - (dI 1 / dx) = Y 1 I 1 + Y 12 I 2 - ( dI ₂ / dx) = Y ₂₁ I ₁ + Y ₂ I ₂ where Z ₁ = jωL ₁ Z ₂ = jωL ₂ Z _m = jωL _m Y ₁ = jωC ₁ Y ₁₂ = −jωC _m Y ₂ = jωC ₂ Y ₂₁ = G _m −jωC _m .

If I ₁ and I ₂ are eliminated from the above transmission equation, (d ² V ₁ / dx ² ) = (Y ₁ Z ₁ + Y _m Z _m ) V ₁ +
(Z ₁ Y _m + Y ₂ Z _m ) V ₂ (d ² V ₂ / dx ² ) = (Y ₂ Z ₂ + Y _m Z _m ) V ₂ +
(Z ₂ Y _m + Y ₁ Z _m ) V ₁ This equation has a general solution in the form of V _1,2 (x) = V ₀ exp (−γx), where γ is the propagation constant of the system. Substituting the functional form into the transmission equation, γ ⁴ −γ ² (Y ₁ Z ₁ + Y ₂ Z ₂ + 2Y _m Z _m ) + (Y
₁ Z ₁ + Y _m Z _m ) (Y ₂ Z ₂ + Y _m Z _m ) − (Z ₁ Y
_{m + Y 2 Z m) (} Z 2 Y m + Y 1 Z m) = 0 is obtained by solving this, the following equation (3) is obtained.

Γ_c ^Two(Ω) = {(2C_m L_m -L_Two C_Two -L₁ C₁ ) Ω^Two / 2} + [{-jg _m γ_m ω + ω (L₁ C₁ -L_Two C_Two )｝^Two +4 {ω^Four (L_m C_Two -C_m L₁ ) (L_m C₁ -C_m L_Two ) -Jg_m L_Two ω^Three (L_m C_Two -C_m L₁ )}]^1/2 / 2 (3) Figure 3 shows the gate input voltage in the field effect transistor.
Value V_g And transconductance g_m Diagram showing the relationship with
It is.

As shown in FIG. 3, the transconductance g _m of the transistor is the voltage V applied to the gate electrode.
_{When the} voltage has a peak value with respect to _g and is equal to or lower than the voltage giving the peak value, the transconductance g _m increases as the voltage level on the gate electrode transmission line T2 increases.

FIG. 4 shows, in the nonlinear line device LS1,
A transconductance g _m of the transistor is a diagram showing the relationship between the propagation speed v _c of the c-mode.

According to FIG. 4, in the c-mode, as the transconductance g _m increases, the propagation velocity v _c of the traveling wave on the electrode transmission line becomes slower. In the above embodiment, as the transconductance g _m increases,
The phenomenon that the propagation velocity v _c of the traveling wave on the electrode transmission line becomes slow is used.

That is, when the gate electrode transmission line T2 and the drain electrode transmission line T1 of the traveling wave type transistor are arranged close to each other, the transconductance of the transistor is caused by the mutual capacitance and mutual inductance between the transmission lines T2 and T1. depending on the value of g _m, the propagation velocity of the traveling wave is changed on both the electrodes, with an increase in the transconductance g _m of the transistor, the signal propagation speed.

That is, from the equation (3), the propagation constant γ _c in the c mode changes according to the transconductance g _{m of the} transistor, and this transconductance g _m is applied to the gate electrode as shown in FIG. This transconductance g _m changes according to the applied voltage V _g.
Changes, the propagation speed of the signal changes as shown in FIG.

FIG. 5 is a diagram showing the result of circuit simulation in which the waveform shaping effect in the nonlinear line device LS1 is quantified.

In FIG. 5, the fall time is 10 ps,
When a rectangular wave input voltage having a low level of 0.3 V and a high level of 1.0 V is applied to the nonlinear line device LS1, the input signal waveform and the output signal waveform thereof are shown.
That is, the upper waveform in FIG. 5 shows the drain electrode transmission line T
1 is a waveform showing the signal voltage wave transmitted above, and the lower waveform is a waveform showing the signal applied to the gate electrode transmission line T2.

As the transconductance g _m increases, the propagation velocity v of the traveling wave on the electrode in the c mode
_{Since c} becomes slower, it can be seen that the higher the input level of the voltage traveling wave, the slower the propagation speed. Therefore, the rise time of the output waveform corresponding to the fall of the input waveform is shorter than the fall time of the input waveform. FIG.
Specifically, the fall time of the input signal is 10p
s is shortened to a rise time of the output signal of 5 ps or less.

That is, the above embodiment is a traveling wave type transistor in which the source electrode of the field effect transistor is grounded, and the gate electrode and the drain electrode thereof are respectively configured as a signal transmission line, and the gate electrode transmission line T2 is used. By setting the difference in voltage level of the input signal applied to the predetermined value or more, the transconductance of the field effect transistor changes, and the input signal is changed by using the region where the signal propagation speed changes with frequency. It is a non-linear line device for waveform shaping.

FIG. 6 is a diagram showing a configuration when the above embodiment is used for circuit evaluation.

In FIG. 6, the non-linear line device LS1 according to the above-described embodiment is used as a digital logic circuit under evaluation DUT (De
It is connected to the input section of the sign Under Test).

The non-linear line device LS1 is, as described above,
Since it has the ability to generate an electric signal with a sharp rise, it can be applied to the characteristic evaluation of the ultrahigh-speed digital circuit DUT with the configuration shown in FIG.

By the way, conventionally, the waveform is steepened by the non-linear line using the bias dependence due to the parasitic capacitance of the diode. However, in the above embodiment, the transconductance g _{m of the} transistor is used to compare with the conventional case. Not only the same function can be realized, but also the function of signal amplification is simultaneously realized by a single element.

By the way, between the gate electrode transmission line T2 and the grounded source electrode T3, an inter-terminal voltage V
There is a parasitic capacitance C _gs (V) having a dependence on
Then, as the parasitic capacitance C _gs (V) increases, the propagation speed of the traveling wave on both electrodes slows down.

Therefore, the source electrode of the field effect transistor is a traveling wave type transistor in which the source electrode is grounded, and the gate electrode and the drain electrode are respectively configured as a signal transmission line, and an input applied to the gate electrode transmission line T2. By setting the difference between the voltage levels of the signals to a predetermined value or more, the gate
A non-linear line device that shapes the waveform of the input signal can be configured by using a region in which the parasitic capacitance between the sources changes and the signal propagation speed changes with frequency.

In practice, the higher the input signal voltage level to the gate electrode transmission line T2, the more transconductance g.
_{As m} increases, the gate-source parasitic capacitance C
_{Since gs} (V) also increases, the signal propagation speed becomes slower due to these two phenomena, and thus the fall time of the input signal becomes shorter.

Further, since the above embodiment is constructed by using a single element, the device scale can be made compact, the cutoff frequency can be removed, and the active circuit element called a transistor is used. The loss can be compensated by.

[0039]

According to the present invention, when the fall time of the input signal is shortened, the device scale can be made compact, the cutoff frequency can be removed, and the loss can be compensated.

[Brief description of drawings]

FIG. 1 is a non-linear line device LS1 according to an embodiment of the present invention.
FIG. 4 is a diagram showing a traveling-wave type transistor, an input signal source, and a terminating resistor as viewed from above.

FIG. 2 is a drain electrode transmission line T1 in the above embodiment.
FIG. 7 is a diagram showing an equivalent circuit of the gate electrode transmission line T2.

FIG. 3 is a diagram showing a relationship between a gate input voltage value V _g and a transconductance g _m in a field effect transistor.

FIG. 4 is a diagram showing a relationship between a transconductance g _m of a transistor and a c-mode propagation velocity v _c in the nonlinear line device LS1.

FIG. 5 is a diagram showing a result of a circuit simulation quantifying a waveform shaping effect in the nonlinear line device LS1.

FIG. 6 is a diagram showing a configuration when the above embodiment is used for circuit evaluation.

FIG. 7 is a diagram illustrating an operation of a conventional nonlinear line device using a voltage variable capacitance of a Schottky diode.

[Explanation of symbols]

LS1 ... non-linear line _{device, R 1, R 2, R} 3, R 4 ... terminal resistance value, V _dd, V _gg ... DC voltage, T1 ... drain electrode transmission line T1, T2 ... gate electrode transmission line T2, T3 ... Source electrode transmission line, v _c ... c mode propagation velocity, V _in , V _gg ... voltage signal source, g _m ... transistor transconductance, C _m ... between drain electrode transmission line T1 and gate electrode transmission line T2 Mutual capacitance existing, L _m ... Mutual inductance existing between the drain electrode transmission line T1 and the gate electrode transmission line T2, C ₂ ... Self capacitance of the drain electrode transmission line T1, C ₁ ... Self of the gate electrode transmission line T2 capacity, L ₂ ... self-inductance of the drain electrode transmission line T1, the self-inductance of L ₁ ... gate electrode transmission line T2.

Claims (2)

[Claims] 1. A traveling-wave transistor in which a source electrode of a field effect transistor is grounded, and a gate electrode and a drain electrode thereof are respectively configured as a signal transmission line, and an input signal applied to the gate electrode transmission line. By setting the difference between the voltage levels of the input signal to a predetermined value or more, the transconductance of the field effect transistor changes, and the waveform of the input signal is shaped using the region in which the signal propagation speed changes with frequency. Non-linear line device. 2. A traveling-wave transistor in which a source electrode of a field effect transistor is grounded, and a gate electrode and a drain electrode thereof are respectively configured as a signal transmission line, and an input signal applied to the gate electrode transmission line. By setting the voltage level difference of the above to a predetermined value or more, the gate-source parasitic capacitance of the field effect transistor changes, and the input signal waveform is shaped using the region where the signal propagation speed changes with frequency. A non-linear line device characterized by: