Oscillators – Solid state active element oscillator – Transistors
Utility Patent
1998-07-27
2001-01-02
Kinkead, Arnold (Department: 2817)
Oscillators
Solid state active element oscillator
Transistors
C331S10800D, C331S132000, C331S114000, C331S115000, C331S1070SL, C331S10800D, C331S17700V
Utility Patent
active
06169461
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-frequency oscillating circuit such as a voltage-controlled oscillator in a radio communication apparatus such as a cellular telephone or a satellite communication apparatus.
2. Description of the Prior Art
Conventional techniques are described with reference to the drawings.
FIG. 19
is a circuit diagram of a conventional high-frequency oscillating circuit. In this figure,
1
and
17
are oscillating transistors;
2
,
3
,
4
,
18
,
19
, and
20
are capacitors;
5
and
21
are resonator coupling capacitors;
6
and
22
are output coupling capacitors;
7
is a resonator;
8
and
23
are varactor diode coupling capacitors;
9
and
24
are varactor diodes;
11
,
12
,
13
,
26
,
27
, and
28
are biasing resistors;
14
and
29
are varactor diode bias chokes;
15
and
16
are high-frequency output terminals;
10
,
25
, and
30
are high-frequency chokes;
31
and
32
are bypass capacitors;
33
is a tuning voltage supply terminal; and
34
is a bias voltage supply terminal.
Conventional high-frequency oscillating circuits of this configuration operate as follows.
In
FIG. 19
, the oscillating transistors
1
and
17
have their base terminal grounded via the capacitors
4
and
20
, respectively, having a sufficiently low impedance in an oscillating frequency band. The capacitors
2
and
18
are connected to the transistors
1
and
17
, respectively, as collector-to-emitter capacitive elements. In addition, the capacitors
3
and
19
are connected between the ground and the emitters of the transistors
1
and
17
, respectively, and are equivalently connected between the emitter and the base because this circuit is of a grounded base type. Furthermore, the resonator
7
, which is connected via the resonator coupling capacitors
5
and
21
, is a half-length resonator with its tip open. Since the middle point of the resonator equivalently acts as a short-circuit point for the ground, the resonator
7
is equivalently connected between the collector and base of the transistor
1
via the resonator coupling capacitor
5
as an inductive element and between the collector and base of the transistor
17
via the capacitor
21
as an inductive element.
Thus, in the circuit in
FIG. 19
, two grounded-base clap oscillating circuits perform oscillating operations by using one half-length resonator to provide oscillating signals the phases of which are mutually shifted through 180°, and their output is obtained from between the high-frequency output terminals
15
and
16
via the output coupling capacitors
6
and
22
as a differential signal output between the two circuits.
In addition, the varactor diodes
9
and
24
are each connected to the resonator
7
via the varactor diode coupling capacitors
8
and
23
, respectively. Furthermore, since the anodes of the varactor diodes
9
and
24
are provided with the ground potential by the varactor diode bias chokes
14
and
29
in a DC manner, the value of a voltage applied to the tuning voltage supply terminal
33
via the high-frequency choke coil
30
varies the values of the capacity of the varactor diodes
9
and
24
to enable the oscillating frequency to be varied.
In addition, the oscillating circuit, which performs such circuit operations, can use an IC process to provide on an IC, elements including not only the oscillating transistors
1
and
17
and their peripherals but also the resonator
7
and a resonating circuit composed of the varactor diodes
9
and
24
.
In the above configuration, however, the capacitors
3
,
4
,
19
, and
20
are connected to the ground, so if an external electromagnetic interference occurs, a potential difference may occur on the ground surface of a circuit board on which the circuits are mounted, thereby losing the balance between the two transistors to degrade the S/N ratio.
In addition, since the resonator
7
and varactor diodes
9
and
24
are formed on an IC chip using the IC process, it is not easy to produce elements having a high Q factor, that is, a small loss. Consequently, this resonating circuit for an oscillating circuit IC cannot easily achieve a high Q factor, so it is difficult to provide a high C/N ratio for the oscillating circuit IC.
SUMMARY OF THE INVENTION
In view of these problems, it is an object of this invention to provide a high-frequency oscillating circuit that does not have its characteristics such as the S/N ratio degraded under an external electromagnetic interference.
It is another object of this invention to provide a resonating circuit for an oscillating circuit IC that can provide a high Q factor and a high-frequency oscillating circuit using this resonating circuit so as to obtain a high C/N ratio.
This invention is a high-frequency oscillating circuit comprising a first and a second oscillating transistors, wherein the bases of the first and second transistors are connected together directly or via a capacitor the impedance of which is lower than a predetermined value at an oscillating frequency, and wherein a differential signal output is obtained from between the emitters of the first and second oscillating transistors as an oscillating output.
According to this configuration, the capacitor connected between the base of the oscillating transistor and the ground is not connected to a ground pattern on a mounting circuit board, but the base electrodes of the two oscillating transistors are connected together directly or via the capacitor. Thus, differential oscillating operations can be performed at a high frequency without the use of the ground pattern on the mounting circuit board, so a high-frequency oscillating circuit can be provided that is not affected by a common mode noise source occurring in the ground pattern on the mounting circuit board or that does not have its characteristics such as the S/N ratio degraded even if an external electromagnetic interference occurs.
In particular, if both bases are directly connected together, this eliminates the load of an impedance unwanted for the bases at the oscillating frequency, thereby providing a high-frequency oscillating circuit that does not have its characteristics such as the S/N ratio degraded.
In addition, this invention is a high-frequency oscillating circuit comprising a first and a second oscillating transistors, wherein the collectors of the first and second transistors are connected together directly or via a capacitor the impedance of which is lower than a predetermined value at an oscillating frequency, and wherein a differential signal output is obtained from between the emitters of the first and second oscillating transistors as an oscillating output.
According to this configuration, the capacitor connected between the collector of the oscillating transistor and the ground is not connected to a ground pattern on a mounting circuit board, but the collector electrodes of the two oscillating transistors are connected together directly or via the capacitor. Thus, differential oscillating operations can be performed at a high frequency without the use of the ground pattern on the mounting circuit board, so a high-frequency oscillating circuit can be provided that is not affected by a common mode noise source occurring in the ground pattern on the mounting circuit board or that does not have its characteristics such as the S/N ratio degraded even if an external electromagnetic interference occurs.
In particular, if both collectors are directly connected together, this eliminates the load of an impedance unwanted for the collectors at the oscillating frequency, thereby providing a high-frequency oscillating circuit that does not have its characteristics such as the S/N ratio degraded.
In addition, according to this invention, a resonator, varactor diodes, and capacitors and chokes constituting a resonating circuit for an oscillating circuit IC are integrated together as module separate from a negative-resistance-generating circuit configured as an IC and including oscillating transist
Andoh Toshiaki
Ishida Kaoru
Kosugi Hiroaki
Miura Takeshi
Sakakura Makoto
Kinkead Arnold
Matsushita Electric - Industrial Co., Ltd.
Ratner & Prestia
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