JPS606561B2 - Sunring gate circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called sampling gate circuit that performs an operation of sequentially extracting and holding a part of ultra-high frequency waves, for example.

Sampling gate circuits are used in sampling oscilloscopes, strobing voltmeters, etc.
This is a circuit that samples and holds a high frequency signal or a signal containing a high frequency, and converts the input signal to a low frequency signal.The electrical circuit is roughly as shown in Figure 1.

Briefly explaining the circuit of FIG. 1, an input signal (signal under test) 1 has a defined characteristic impedance Z. The signal is propagated through a signal transmission line Le having a characteristic impedance Z. is terminated with a resistor R with a value equal to When changing, a portion of the input signal passes through the diodes D, , D2 and charges the memory capacitors E, , E2, outputting a value proportional to the instantaneous level of the input signal. In order for this sampling gate circuit to have flat frequency characteristics over a wide band, gate diodes D, D2 and capacitors E. , E2, and the like to be used, the configuration of the signal transmission line Le to be measured and the sampling pulse transmission line Ls, and the arrangement of each element become issues. FIG. 2 shows an example of the arrangement of the gate diode ○n and the memory capacitor En with respect to the cross section of the signal transmission line Le under test for efficient sampling.

The arrow indicates the electromagnetic field (TE
The diode Dn and the capacitor En must be placed in the direction of the electric field and in a place where the electric field is concentrated. In addition, in a super high frequency band sampling gate circuit, memory capacitors E, . . . connected to gate diodes D, , D2 shown in FIG.
It is desirable that the ground side of the electrode E2 be directly grounded to the ground plane of the signal transmission line Le to be measured. This is a gated diode D. , input signal 1 leaked to the sampling pulse transmission line Ls due to the capacitance between the terminals of D2, etc.
A part of the signal is reflected within the sampling pulse transmission line LS and returns to the gate diodes D, D2. This is because of its negative effects. In addition, the sampling gate circuit has SWR (standing wave ratio) and leakage (kick out) of the sampling pulses p+ and p- to suppress the influence on the signal source under test and other devices connected at the same time. A configuration that reduces the number of pulses by 4 is required. In order to satisfy this condition, gate diodes D, D2 are used that have low inter-terminal capacitance, and the diodes D, D2 are arranged so as not to cause unnecessary disturbance to the input signal transmission line Le. In addition, the sampling pulse p has a well-balanced positive and negative polarity.
+, p- must be input to the gate circuit. A conventional sampling gate circuit is constructed using a coaxial line (see FIG. 3a) and a microstrip line (see FIG. 3b) as transmission lines.

When coaxial lines are used for the signal under test transmission line Le and the sampling pulse transmission line Ls, the transmission of the signal under test and the sampling pulse is excellent, but the positive and negative sampling pulses p+ and p- are separated by independent paths. Since the asymmetric components of the positive and negative sampling pulses p10 and p- are input to the sampling gate circuit through the signal transmission line Le, the asymmetric components of the positive and negative sampling pulses p1 and p- leak to the signal transmission line Le and become relatively large kick-out pulses. Furthermore, in the sampling gate circuit shown in FIG. 3b using a microstrip line, not only the transmission efficiency of the signal under test deteriorates, but also the direction in which the gate diode Dn is arranged is opposite to the signal transmission line Le as shown in FIG. Since the direction of the electric field does not match the direction of the electric field, the sampling efficiency decreases and the SWR increases, making it unsuitable for use as a sampling gate circuit in an ultra-high frequency band. Furthermore, in the above two structures, it is difficult to ground the memory capacitors E, E2 directly to the ground of the signal transmission line Le.

This is because the parts connected to the ground side electrodes of capacitors E, E2 also serve as the sampling pulse transmission line Ls, so a distance equal to at least half of the electrical length corresponding to the sampling pulse width is the sampling pulse p.
This is because it is necessary to have a structure in which + and p- are not grounded. In order to achieve this, in the case of a coaxial line, a conical cavity is provided (lEEE
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In the former case, the circuit has a complicated three-dimensional configuration and is difficult to manufacture. Furthermore, in the latter circuit, it is difficult to efficiently input sampling pulses to the slot line. The present invention eliminates the drawbacks of conventional sampling gate circuits and provides a sampling gate circuit that is easy to manufacture and has excellent high frequency characteristics.

The present invention will be explained in detail below using the drawings. A cross-sectional view of a sampling gate circuit according to the present invention is shown in FIG. 5a. The three strips A, B, and C shown in the figure constitute a transmission line, and gate diodes D, D2 and memory capacitors E, E2 are connected between each strip A, B and B, C according to the strip direction. arranged vertically. Gate·
Diodes D,,D2 and memory capacitors E,,E2
and strips A and B near the locations where these are connected.
, C constitute a sampling gate circuit. The signal transmission line Le under test has strip B as the center strip,
This is a so-called tri-plate strip line in which strips A and C are grounded. The original tri-plate strip line has a ground plane that extends infinitely, but because the tri-plate strip line is better at concentrating electromagnetic fields, it can have a ground plane several times the width of the central strip. It has been shown that there is no problem in practical use. The present invention takes advantage of the features of the tri-plate strip line and constructs two strip lines L and L2 for transmitting sampling pulses in FIG. 6 (L2 is not shown).
The strips A and C, which are connected to the strips A and C to form a ground plane, are configured as a microstrip line with a virtual ground plane G as part of the sampling pulse transmission line Ls, as shown in FIG. FIG. 6 mainly shows parts related to strips A and B.
Next, the sampling operation will be described with respect to the example shown in FIG.

The signal under test 1 is typically input to strips A, B, and C via coaxial lines (not shown in FIG. 6). The ends of this coaxial line are such that the center conductor is at the tip of strip B, and the outer conductor is at the tip of strip A, and strip C (
(not shown in FIG. 6), and the signal to be measured is transmitted from the coaxial line to the tri-plate strip line. Generally, when a transmission line is converted from a coaxial line to a strip line, a so-called fringing field often occurs and deteriorates the transmission characteristics, but in the case of a tri-plate type strip line, as shown in Figure 5b, the coaxial line and the electromagnetic field Since the shapes (electromagnetic field shapes in the cross section of the line as TEM waves) are similar, the converter can be manufactured so that the deterioration of the transmission characteristics can be almost ignored. The signal under test 1 is transmitted with strip B as the center strip and strips A and C as the ground plane. Ground plane A of the tri-plate strip line
and C gradually become narrower until A2 and C2 (C2 is not shown) are approximately four times as wide as the center strip B, and while maintaining that width, diodes D, , D2 and capacitors E and E2 (however, D2 and Sampling gate sections A3, B3 and C3 (C
3 (not shown) transmits the signal under measurement. The signal under test 1 that has passed through the sampling gate section is then converted from A to A.
3, A tri-plate type strip line having a shape in which almost the same shapes as those from B, to B3 and C, to C3 are arranged in the opposite direction, and A5, B, and C5 are connected to the coaxial line on the other side. connected to the line.

Note that A4 and C4 (C4 is not shown) indicate locations where the widths of strips A and C constituting the ground plane become wide. Diodes D, , D2 and capacitors E, , E2
A3 and C3 of the tri-plate strip line part 3, ears and C3 (C3 not shown) on which are mounted
are connected to striplines L and L2 (L2 not shown), the other end of L receives a positive sampling pulse p+, and the other end of L receives a negative sampling pulse p+ with the same amplitude as p+. A pulse p- (p- is not shown) is input. The sampling pulses p- and p- have electric lines of force shown in Figure 5c in the cross section in the transmission direction, and the strip lines L and L are microstrip lines with a virtual ground plane G between L and L. It consists of Sampling pulses p+ and p- are connected to sampling gate sections A3 and C3.
(C3 not shown) and capacitor E. and E2
(E2 is not shown) through the diode D, and D2 (
D2 is not shown), the diode D, and D2
is conductive for the time width of the sampling pulse, and the capacitors E and E2 are connected to the capacitors E and E2, which are connected to the capacitors E and E2, which are connected to the capacitors E and E2. A charge proportional to the instantaneous value of the measurement signal is accumulated. Incidentally, a part of the sampling pulse inputted to the sampling gate section is reflected by the strip lines L and L2, and a part is propagated through the strips A and C of the tri-plate line.

In order for the sampling gate to be driven by the time width of the sampling pulse, the time required for the rising edge of the sampling pulse to be reflected at the discontinuous part of the sampling pulse transmission line and return to the gate section is longer than the sampling pulse time. It is necessary that the pulse time width be narrow. For this reason, L,
, the electrical length of the strip L2 (and the strip from C3 to C2 and C3 (not shown)
The electrical length of the strip from C4 to C4 is determined by the sampling
The length is 1/sha of the pulse time width. In addition, in FIG. 6, the microstrip lines L and L2 that input the sampling pulse are connected to the sampling line.
Although it is connected to the ground plane strip N and C3 of the tri-plate type strip line in the gate part, this connection point does not have to be limited to the sampling gate part, and L can be connected to any part of the strip from A4 to A4 in FIG. It may be connected at a point, for example, in the middle between A3 and A3.

However, the strip line L2 is also connected between C3 and A4. In that case, it is necessary to set the electrical length of the strip between the connection point and A4 and C4 to 1/sa of the sampling pulse time width. In addition, a directional coupler is formed by the strip lines L and strip A, and the strip line L and strip C, and the strip lines L and L are connected to the strip A.
Strips A and C may be driven with positive and negative sampling pulses without being directly connected to strips A and C. According to the above configuration, the conditions that the sampling gate circuit described above should have can be realized.

First, the gate diodes D, D2 and memory capacitors E, E2 shown in FIG. 5a are placed in the direction of the electric field of the signal under test and the sampling pulses p+, p-, and in a place where the electric field is concentrated. I can do it.

This is clear from the electric field diagrams in the cross sections of the tri-plate stripline and microstripline shown in FIGS. 5b and 5c. With this arrangement of diodes and capacitors, it is possible to efficiently take out the sampling output and create a wideband sampling gate circuit.
Second, when configuring a transmission line with a suitable characteristic impedance (for example, 500), the width of strips A and C of the microstrip line shown in Figure 5a is smaller than the width of the central strip B of the tri-plate strip line. twice as wide (
(depending on the derivative used).

Therefore, strip A that constitutes the micro strip line
, C are almost equivalent to the infinite-width ground plane of the tri-plate strip line, so the electrodes to be twilled of the memory capacitors E, , E2 are directly connected to the ground of the signal transmission line under test Le. It can be grounded to the surface, and it is possible to reduce the adverse effect of leaking the diode and capacitor on the frequency characteristics of the sampling gate circuit of the signal under test. Third, the sampling pulse transmission line is composed of two parallel strips A and C and strip lines L and L2, as shown in FIG. 5a.

With this configuration, the anti-phase components of the sampling pulses p+ and p- transmitted on the strip lines L, , L and strips A and C are transmitted through a low-impedance microstrip with a virtual ground plane G between strips A and C. Although it is efficiently transmitted on the line, the in-phase component becomes a high impedance line with the body or the like grounded, which deteriorates the transmission efficiency.
As a result, the loss of the unbalanced components of the sampling pulses p+, p- increases, and the gate diode' inputs the sampling pulses p+, p-, which are balanced between positive and negative, and prevents the generation of the kick-out pulse. It can be made small. Fourth, since the transmission line is constructed of strip lines, the circuit elements cannot be assembled using etching technology, film (thin film or thick film) technology, or chip assembly on commonly used microwave printed circuit boards or discussion conductors. etc., and can avoid the configuration of a three-dimensional circuit with complicated mechanical parts.

Gate diodes, memory capacitors, etc. are fabricated on a suitable substrate (often made of the same material used to fabricate the stripline) and then inserted into the holes provided in the concession body that makes up the stripline using ribbons or wires. At Abonding,
Can be easily placed. As described above, according to the present invention, it is possible to realize a sampling gate circuit with excellent high frequency characteristics with a simple circuit configuration, and it can be manufactured by using film technology or assembly technology developed with the development of IC technology. The circuit configuration is easy.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a sampling gate to which the present invention is applied, FIG. 2 is a cross-sectional view of a transmission line and a diagram of a preferred arrangement of elements, FIGS. 3a and b are block diagrams of a conventional sampling gate circuit, and FIG. 4 is a micro - Electric field distribution diagram of a sampling gate circuit using a strip line, FIG. 5a is a cross-sectional view of the sampling gate circuit according to the present invention, FIG. 5b is a cross-sectional diagram and electric field distribution diagram of the signal transmission line to be measured according to the present invention, FIG. 5c
6 is a cross-sectional view and an electric field distribution diagram of a sampling pulse transmission line according to the present invention, and FIG. 6 is a schematic perspective view showing the main parts of an embodiment of the present invention. 1... Input signal, Le... Signal transmission line, Ls... Sampling pulse transmission line,
Z.・・・・・・Characteristic impedance of signal transmission line, R・
...Termination resistor, p10, p-...Sampling
Pulse, D,,D2,Dn・”...Gated diode,
E,,E2,En...Memory capacitor, A,B,C
...Strip, G...virtual ground plane, L2...
...Strip line, A,, A2, A3, A4,...
... Each part of strip A, B,, B3, B...
Each part of strip B, C,, C5...Strip C
Each part of. Box l Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. A sampling gate circuit composed of a signal transmission line through which a signal under test propagates, a sampling means connected to the signal transmission line, and a sampling pulse transmission line through which a sampling pulse that operates the sampling means is transmitted. In this method, the signal transmission line is constituted by a triplate type strip line, and the sampling pulse transmission line is constituted by two parallel strip lines, and the portion of the triplate type strip line to which the sampling means is connected is The sampling method is characterized in that the ground plane is aligned with the parallel strip line, and the pair of diodes and the pair of capacitors of the sampling means are arranged in the electric field direction of the two types of transmission lines. gate circuit.