Oscillators – Solid state active element oscillator – Transistors
Reexamination Certificate
1999-07-23
2001-02-13
Pascal, Robert (Department: 2817)
Oscillators
Solid state active element oscillator
Transistors
C331S1170FE
Reexamination Certificate
active
06188296
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to local oscillators, and more particularly, to a dielectric oscillator for use in an antenna unit (Low Noise Block downconverter, hereinafter referred to as “LNB”) for receiving signals in the Ku band or higher frequency bands (such as Ka band).
2. Description of the Background Art
The Ku band about in the range of receiving frequencies from 10 GHz to 13 GHz has been used for satellite broadcasting and satellite communication. A typical Ku band satellite broadcasting receiving system will be now described in conjunction with accompanying drawings, where the same reference characters represent the same or corresponding portions.
Referring to
FIG. 11
, the Ku band satellite broadcasting receiving system is divided into an outdoor part
200
and an indoor part
210
. Outdoor part
200
includes an antenna
201
and an LNB
202
connected thereto, while indoor part
210
includes an indoor receiver
204
and a television set
209
. LNB
202
amplifies an electric wave received from antenna
201
with reduced noise and supplies a signal at a sufficient level with a low noise to indoor receiver
204
connected through a coaxial cable
203
. Indoor receiver
204
includes a DBS tuner
205
, an FM demodulator
206
, a video and audio circuit
207
and an RF modulator
208
. A signal applied to indoor receiver
204
through coaxial cable
203
from LNB
202
is processed by these circuits and applied to television set
209
.
As a typical Ku band receiver LNB, a domestic CS receiving LNB will be now described. Referring to
FIG. 12
, an incoming signal at an input frequency in the range from 12.2 GHz to 12.75 GHz is received at an antenna probe
251
in a waveguide, amplified by a low noise amplifying circuit herein after simply as “LNA”)
252
with reduced noise, and then passed through a band pass filter (hereinafter simply as “BPF”)
253
. BPF
253
allows a desired frequency band to pass therethrough in order to remove a signal in an image frequency band.
A signal passed through BPF
253
is input to a mixing circuit (hereinafter MIX
254
together with an oscillation signal of 11.2 GHz from a local oscillator (LO)
256
, and frequency-converted into a signal in an intermediate frequency band from 1000 to 1550 MHz at MIX
254
. The resultant signal is amplified by an intermediate frequency amplifying circuit (hereinafter as “IF AMP”)
257
to have appropriate noise and gain characteristics and output from an output terminal
261
. A power supply
258
is a power supply to provide electric power to LNA
252
, IF AMP
257
and local oscillator
256
.
In the Ku band satellite broadcasting receiving system as described above, local oscillator
256
used in LNB
202
is a critical part which determines the performance of LNB
202
. A dielectric resonator oscillator (DRO) generally called a drain ground band reflective type dielectric oscillator is used as local oscillator
256
.
Meanwhile, satellite broadcasting and communication are planned to be realized using the Ka band about in the range of receiving frequencies from 16 GHz to 24 GHz.
Referring to
FIG. 13
, the Ka band satellite broadcasting receiving system planned to be used for domestic COMETS is divided into an outdoor part
300
and an indoor part
310
. Outdoor part
300
includes an antenna
301
and an LNB
302
connected thereto. Indoor part
310
includes an indoor receiver
304
and a terminal
308
. LNB
302
amplifies a very small electric wave received at antenna
301
with reduced noise and supplies a signal at a sufficient level with reduced noise to indoor receiver
304
connected through coaxial cable
303
. Indoor receiver
304
demodulates a signal input from LNB
302
using DBS tuner
305
and FM demodulator
306
, and decodes data with decoder
307
for transmission to terminal
308
. Terminal
308
can be for example, a so-called digital processing device such as personal computer, television set, modem and FAX.
Referring to
FIG. 14
, in the Ka band receiving LNB, an incoming signal at an input frequency in the range from 20.4 GHz to 21.0 GHz is received at an antenna probe
351
in a waveguide, amplified with reduced noise at an LNA
352
, and then removed of images at a BPF
353
. A signal passed through BPF
353
is input to an MIX
354
together with an oscillation signal at a frequency of 18.7 GHz from a local oscillator
355
. The resultant signal is frequency-converted at MIX
354
into a signal in an intermediate frequency band from 1700 MHz to 2300 MHz. The signal is then amplified by an IF AMP
357
and output from an output terminal
361
. A power supply
358
is a power supply to provide electric power to LNA
352
, IF AMP
357
and local oscillator
356
.
As a local oscillator used for receiving the Ka band can be a circuit as shown in FIG.
15
. Referring to
FIG. 15
, the Ka band local oscillator includes an FET
401
and a dielectric resonator
402
. The gate terminal G of FET
401
is connected in series with a coupling line
403
and a 50&OHgr;-terminal chip resistor
404
, the other end of which is connected to ground.
The drain terminal D of FET
401
is connected to a DC power supply
414
and a capacitor
405
for grounding, the other end of which is connected to ground.
The source terminal S of FET
401
is connected to an output matching stub
406
, the other end of which is connected to a coupling capacitor
407
and an inductance
408
. The inductance
408
is further connected to a capacitor
409
for grounding and a chip resistor
410
for grounding, connected in parallel to the other end of inductance
408
. The other ends of capacitor
409
for grounding and chip resistor
410
for grounding, are connected to ground.
The oscillation characteristics of the Ka band local oscillator such as power, frequency temperature drift, phase noise and load fluctuation are optimized depending upon the distance between dielectric resonator
402
and coupling line
403
, the distance between dielectric resonator
402
and FET
401
, and the width and length of output matching stub
406
provided at source terminal S.
The Ka or Ku band local oscillator is particularly difficult and costly to manufacture. This is because the circuit designing does not allow much flexibility and is difficult in optimizing the oscillation characteristic. In addition, substrate patterns cannot be readily changed as practiced according to conventional techniques in response to improvement in the oscillation characteristics derived from change in design.
SUMMARY OF THE INVENTION
The present invention is directed to a solution to the above-described problems, and it is one object of the present invention is to provide a local oscillator easy to be manufactured with reduced cost and capable of exhibiting stable oscillation characteristic.
Another object of the present invention is to provide a local oscillator capable of readily changing oscillation characteristic if the design is changed.
In order to achieve the above objects, a local oscillator according to one aspect of the present invention includes an oscillation element, a bias circuit having one end connected to a power supply and the other end connected to a drain terminal of the oscillation element, and a printed circuit board on which the oscillation element and the bias circuit are provided, and the bias circuit includes a first stub for grounding, a high impedance line and a chip capacitor.
According to the present invention, the circuit of a local oscillator can be formed on a single printed circuit board sheet, which reduces assembling operation, and a local oscillator with reduced manufacturing cost can be provided. Furthermore, a local oscillator having stable oscillation characteristics can be provided.
According to another aspect of the present invention, the local oscillator includes an oscillation element and a bias circuit having one end connected to a power supply and the other end connected to the drain terminal of the oscillation element, and the bias
Kato Masahiro
Nibe Masayuki
Choe Henry
Pascal Robert
Sharp Kabushiki Kaisha
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