JPS644681B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a microwave integrated circuit (hereinafter referred to as "MIC").
The present invention relates to a voltage-tunable microwave semiconductor oscillator that is built into a substrate (called "Varactor diode bias voltage") and whose oscillation frequency can be tuned by the bias voltage of a varactor diode.

Conventionally, there is a voltage-tuned microwave semiconductor oscillator of this type as shown in FIG. In Fig. 1, 1 is a dielectric substrate as an MIC substrate made of ceramics or Teflon (trade name of DuPont, USA) that has low dielectric loss in the microwave band, and 2 to 5 and 8 are made by vapor deposition or plating method. 2 is a gate electrode transmission line, 3 is a drain electrode transmission line, 4 is an output matching line, and 5 is a 50Ω transmission line. The output line 6 is a gate electrode G, a drain electrode D, and a source electrode S, respectively.
4 is a gallium arsenide metal semiconductor field effect transistor (hereinafter referred to as GaAs MES FET) as a three-terminal microwave semiconductor device, 7 is a varactor diode whose junction capacitance changes depending on the bias voltage, and 8 is a varactor diode 7. This is a 1/4 wavelength transmission line for short-circuiting at high frequencies.

Next, the effect will be explained.

In this voltage-tuned microwave semiconductor oscillator, the drain electrode D to which the drain electrode transmission line 3 having a length of 1/4 wavelength is connected is short-circuited at high frequency. generally operates in the microwave band
The GaAs MES FET 6 is unstable at high frequencies when the drain electrode D is short-circuited. Therefore,
As shown in Figure 1, GaAs is unstable at high frequencies.
A resonant circuit composed of a gate electrode transmission line 2 and a varactor diode 7 is connected to the gate electrode G of the MES FET 6, and is normally used in the microwave band.
A microwave semiconductor oscillator can be constructed by matching a 50Ω output line 5 with a characteristic impedance of the same value as a 50Ω load and a source electrode S using an output matching line 4. Note that the microwave power of the oscillator is taken out from the source electrode S. Here, the oscillation frequency of this oscillator is mainly determined by the length lg of the gate electrode transmission line 2 that constitutes the resonant circuit and the junction capacitance of the varactor diode 7, so voltage tuning of the oscillation frequency is achieved by changing the bias voltage. This is possible by changing the junction capacitance of the varactor diode 7.

Since the conventional voltage-tuned microwave semiconductor oscillator is MIC-based in this way, it has the following excellent advantages. That is, (a) the design of the oscillator is easy;

(b) It is small and lightweight.

(c) It has a small number of parts and is easy to assemble.

(d) Highly reliable.

However, the conventional voltage-tuned microwave semiconductor oscillator described above has the following drawbacks because it does not have a mechanical frequency tuning mechanism.

(a) Length of gold wire used for bonding varactor diode 7, varactor diode 7
The oscillation frequency varies at a constant varactor bias voltage due to manufacturing variations in the junction capacitance or the length lg of the gate electrode transmission line 2.

(b) When creating voltage-tuned microwave semiconductor oscillators with different oscillation frequencies, the length lg of the gate electrode transmission line 2 is adjusted to suit each oscillation frequency.
This requires MIC substrates with different values or varactor diodes 7 with different junction capacitances, which increases manufacturing costs.

The present invention was made in order to eliminate the above-mentioned drawbacks of the conventional ones.
It is an object of the present invention to provide a voltage-tuned microwave semiconductor oscillator whose oscillation frequency can be adjusted by electrically coupling and arranging a dielectric chip.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a voltage-tuned microwave semiconductor oscillator according to one embodiment of the invention. In the figure, the same symbols as in Figure 1 indicate the same or equivalent parts, and 9 is 1/4
This is a dielectric chip mounted on the wavelength transmission line 8 so as to be movable in a direction perpendicular to the line 8.

Next, the effects will be explained.

In this voltage-tuned microwave semiconductor oscillator, the drain electrode D is short-circuited at high frequencies as in the conventional oscillator, so the GaAs MES FET 6 is unstable at high frequencies and oscillates. In addition, as with conventional oscillators, its oscillation frequency is mainly determined by the length lg of the gate electrode transmission line 2 and the junction capacitance of the varactor diode 7, which constitute the resonant circuit, so the oscillation frequency can be voltage-tuned by the diode bias voltage. be.

In addition, in this oscillator, the 1/4 wavelength transmission line 8 that short-circuits the varactor diode 7 at high frequency and the dielectric chip 9 placed on this line 8 are electrically coupled by the leakage electric field of the transmission line. Therefore, the oscillation frequency is also affected by the dielectric chip 9. Therefore, by adjusting the degree of coupling between the 1/4 wavelength transmission line 8 and the dielectric chip 9, the oscillation frequency can be adjusted. To adjust the degree of coupling, the dielectric chip 9 is moved vertically in the drawing to change the distance l between the central axis a of the 1/4 wavelength transmission line 8 and the upper end surface 9a of the dielectric chip 9 in the drawing. Just let it happen.

In order to confirm the effectiveness of the oscillation frequency adjustment function of the dielectric chip 9, the inventor of the present invention investigated GaAs
A MIC oscillator circuit was constructed using an MES FET, a GaAs shot barrier diode, and an alumina ceramic dielectric chip, and measurements were performed.
The GaAs FET 6 used has a gate length of 1 μm, a gate width of 800 μm, and a saturated drain current of 180 mA. The varactor diode 7 has a junction diameter of 100 μm and a junction capacitance of 2.5 pF at a reverse bias of 1 V. The dielectric chip 9 has a dielectric constant of 38, 3.10×3.10. ×0.635mm square chip,
The MIC board 1 has a dielectric constant of 10 and a thickness of 0.635 mm.

FIG. 3 shows the frequency adjustment characteristics obtained in the above measurements, where the horizontal axis shows the distance l between the 1/4 wavelength transmission line 8 and the dielectric chip 9, and the vertical axis shows the oscillation frequency f and the oscillation output P. In the figure, f ₁ and P ₁ are the values when the center line b of the dielectric chip 9 and the center axis a of the 1/4 wavelength transmission line 8 coincide, and f ₂ and P ₂ are the values at the upper end surface 9 of the chip 9.
f ₃ , P ₃ are the values when a and the upper end side of the line 8 in _{FIG .} is the value when the upper end surface 9a of _the chip 9 and the lower end side of the track 8 in _FIG . is the value of According to this measurement result, by changing the distance l, the oscillation frequency f can be adjusted from 9.52 GHz to 9.68 GHz while keeping the oscillation output P at approximately 170 mW, confirming the effectiveness of the present invention. Ta. In addition, in this measurement, when the varactor bias voltage Vv was changed from 5V to -12V, approximately
A voltage tuning width of 200MHz was obtained. The above characteristics are obtained by connecting a 5Ω resistor Rs to the source electrode S and gate electrode G of the GaAs MES FET6, and applying a 6V bias voltage V _B and a 130 mA bias current I _B between the drain electrode D and gate electrode G. It is obtained by applying .

In the above embodiment, a case was described in which a GaAs MES FET was used as a three-terminal microwave semiconductor device, but in this three-terminal microwave semiconductor device, the gate electrode, drain electrode, and source electrode are respectively connected to the base electrode, collector electrode, and It goes without saying that a microwave junction transistor can be used by replacing it with an emitter electrode.

As described above, according to the present invention, a transmission line and a varactor diode constituting a resonant circuit are connected to one electrode of a three-terminal microwave semiconductor element that is incorporated on a MIC board and is unstable at high frequencies. 1/ which shorts the varactor diode at high frequency.
Since the dielectric chip is electrically coupled to the four-wavelength transmission line, it is possible to obtain a highly practical voltage-tunable microwave semiconductor oscillator that can adjust the frequency.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a conventional voltage-tuned microwave semiconductor oscillator, FIG. 2 is a plan view of a voltage-tuned microwave semiconductor oscillator according to an embodiment of the present invention, and FIG. 3 is a measurement result of the frequency adjustment characteristics of the oscillator. FIG. 1...Dielectric substrate (microwave integrated circuit board),
2...Gate electrode transmission line, 6...GaAs MES
FET (3-terminal microwave semiconductor element), 7...Varactor diode, 8...1/4 wavelength transmission line (transmission line for high frequency short circuit), 9...Dielectric chip. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A three-terminal microwave semiconductor element that is incorporated on a microwave integrated circuit board and has a series or parallel feedback circuit and is unstable at high frequencies; a transmission line connected to one terminal of the wave semiconductor element; a varactor diode connected to the other end of the transmission line to form a resonant circuit together with the transmission line to perform voltage tuning of the oscillation frequency; and one end connected to the varactor diode. A harmonic shorting transmission line connected to the other end of the diode and having the other end open and having a length of approximately 1/4 wavelength, and a harmonic shorting transmission line that is placed in close contact with the harmonic shorting transmission line and transmits on the transmission line. A voltage-tuned microwave semiconductor oscillator comprising: a dielectric chip that adjusts the oscillation frequency by changing the degree of electrical coupling with the transmission line by moving in a direction perpendicular to the transmission line. 2. The three-terminal microwave semiconductor device is a field effect transistor, and the field effect transistor has its drain electrode harmonically shorted, its gate electrode connected to the transmission line, and microwave power extracted from its source electrode. A voltage-tuned microwave semiconductor oscillator according to claim 1, characterized in: 3. The voltage-tuned microwave semiconductor oscillator according to claim 1, wherein the three-terminal microwave semiconductor element is a junction transistor.