JPH0261161B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC bias circuit for transistors used in the microwave band.

[Conventional technology]

Conventionally, as a bias circuit for a microwave transistor, one end of a high impedance bias line is connected to an RF signal line, the other end is connected to a feedthrough capacitor, and bias is supplied via the feedthrough capacitor.

[Problem that the invention seeks to solve]

However, in this circuit, as the frequency increases, the RF shorting surface of the feedthrough capacitor becomes inconsistent and loss occurs, so fine adjustment is required especially for low-noise circuits and high-output circuits that require low loss. It also had the disadvantage of causing ripples within the band. In addition, high-output circuits that require a large amount of bias current have the disadvantage that it is difficult to obtain high-impedance lines.

In order to compensate for the drawbacks of the conventional circuits as described above, the present invention provides a constant RF short circuit surface and a short circuit surface with extremely low loss, thereby achieving stable characteristics within the band of use and improving the RF circuit side. It is an object of the present invention to provide a microwave transistor bias circuit with reduced loss.

The present invention also seeks to provide a microwave transistor bias circuit that does not require the bias lead-out line to be of sufficiently high impedance.

[Means for solving problems]

In the present invention, a capacitor having a structure in which a conductor disk is sandwiched between two dielectric films having a relative dielectric constant ε _r is interposed in the bias line at a position 1/4 wavelength from the RF signal line, and the diameter of the disk is is effectively 1/√ of 1/2 wavelength
ε _r times, and the diameter of the hole accommodating the capacitor is substantially 1/√ _r times one wavelength.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

The figure is a longitudinal sectional view of one embodiment of the present invention. The microwave band transistor 5 is connected to the microstrip line 4. A DC bias line 1 is connected to the microstrip line 4 through a chassis divided into upper and lower halves.
A structure in which a sufficiently thin conductor disk 2 with a diameter d of approximately 1/2√ _r wavelength is sandwiched between dielectric films 3 and 3' with a relative dielectric constant ε _r at four wavelength positions (indicated by L in the figure). A capacitor is interposed. The diameter of the hole that accommodates this capacitor is approximately 1/√ _r wavelength. The feedthrough capacitor 6 is connected via the RF shorting surface configured in this manner.

With this configuration, not only is the radial tip of the disk 2 open and the center almost a short-circuit surface, but the hole itself that accommodates the disk 2 and the dielectric films 3, 3' becomes a radial yoke. Since it forms
The shorted surface becomes a more complete shorted surface.

As described above, the disk 2 is configured so that not only the center becomes a short-circuit surface, but also the diameter of the hole that becomes the outer conductor becomes a short-circuit surface at the center, so it provides a short-circuit surface with extremely good short-circuit characteristics. do. Therefore, even if the DC bias line is somewhat thick and cannot be used as a sufficiently high-impedance bias lead line, this bias circuit becomes a bias circuit without RF loss, and is also suitable for the RF signal line, that is, the microstrip line 4. The influence is reduced, resulting in a stable and high-performance bias circuit. Furthermore, since the inner conductor, that is, the DC bias line 1 is supported by the disk 2, it also has the effect of providing a mechanically stable configuration.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to have stable characteristics within the usage band and reduce loss on the RF circuit side. Also, since the bias line does not have to have a sufficiently high impedance,
The bias current capacity can also be increased.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view of one embodiment of the present invention. In the figure, 1 is the DC bias lead wire, 2 is the RF
Conductor disk for short circuit, 3 and 3' are dielectric films,
4 is a microstrip line, 5 is a microwave transistor, and 6 is a feedthrough capacitor.

Claims (1)

[Claims] 1 This is a circuit that biases a microwave band transistor, and the capacitor has a structure in which a conductor disk is sandwiched between two dielectric films with a relative dielectric constant ε _r on the bias line located 1/4 wavelength from the RF signal line. interposed, and the diameter of the disk is substantially 1/√ _r of 1/2 wavelength.
A microwave transistor bias circuit characterized in that the hole diameter for accommodating the capacitor is substantially 1/√ _r times one wavelength.