High-frequency circuit apparatus and communication apparatus

Details High-frequency circuit apparatus and communication apparatus High-frequency circuit apparatus and communication apparatus

2000-06-09

2004-02-24

Appiah, Charles (Department: 2682)

Telecommunications

Transmitter and receiver at same station

With transmitter-receiver switching or interaction prevention

C455S078000, C455S083000, C333S126000

Reexamination Certificate

active

06697605

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hiqh-frequency circuit apparatus and a communication apparatus used for, e.g., a microwave band.
2. Description of the Related Art
For instance, a transmitting frequency band of 1850 to 1910 MHz is required for a transmitting side circuit of an antenna duplexer used for a PCS, a receiving frequency band of 1930 to 1990 MHz is required for a receiving side circuit. Both of transmitting side and receiving side circuits need to have a wide passing band of 60 MHz. Separation of 20 MHz is assured to separate the transmitting frequency band and receiving frequency band, and the separation between them is extremely small.
The antenna duplexer synthesizes a phase of the transmitting side circuit with a phase of the receiving side circuit. In case of the PCS, the transmitting side circuit is set to have a high impedance of the receiving frequency band of 1930 to 1990 MHz (become open), and the receiving side circuit is set to have a high impedance of the transmitting frequency band of 1850 to 1910 MHz (become open). Accordingly, the phase of the transmitting side circuit is synthesized with that of the receiving side circuit desirably.
FIG. 8
shows a circuit construction example of an antenna duplexer
1
, and
FIG. 9
is a perspective view of the antenna duplexer
1
where parts are mounted on a circuit board
40
. In case of the PCS system, the antenna duplexer
1
has narrow separation between the transmitting frequency band and the receiving frequency band of 20 MHz, so that the transmitting frequency band is divided into two bands, i.e., a band of 1850 to 1880 MHz and a band of 1880 to 1910 MHz, the receiving frequency band is divided into two bands, i.e., a band of 1930 to 1960 MHz and a band of 1960 to 1990 MHz, and thus the passing band is made narrow and the separation is made wide. That is, a reactance element (PIN diode) capable of controlling a voltage is connected to a resonator, and the reactance element and resonator are voltage-controlled. Consequently, it is possible to switch the two kinds of passing bands which a transmitting side circuit
25
and a receiving side circuit
26
have, respectively, and the number of filter stages is reduced to have a small size and high characteristics.
Referring to
FIGS. 8 and 9
, Tx denotes a transmitting terminal; Rx a receiving terminal; ANT an antenna terminal;
2
and
3
resonators of the transmitting side circuit
25
;
4
to
6
resonators of the receiving side circuit
26
; L
1
and L
11
coupling coils; C
1
and C
2
coupling capacitors which decide the magnitude of a blocking band attenuation amount; L
9
and L
10
inductances for resonance; C
5
, C
6
, and C
24
capacitors; C
3
, C
4
, and C
7
to C
9
capacitors for variable frequency band; D
2
to D
6
PIN diodes; L
2
, L
3
, and L
6
to L
8
choke coils; R
1
, R
2
, C
22
, and C
23
resistors and capacitors for supplying a control voltage; L
20
, L
21
, C
15
coils and capacitors comprising phase circuits; and C
11
to C
14
coupling capacitors. Dielectric resonators are used for the resonators
2
to
6
.
The antenna duplexer
1
outputs a transmitting signal, which is inputted from a transmitting circuit system to the transmitting terminal Tx, from the antenna terminal ANT via the transmitting side circuit
25
, and also outputs a receiving signal inputted from the antenna terminal ANT from the receiving terminal Rx to a receiving circuit system via the receiving side circuit
26
.
CONT
1
denotes a voltage control terminal for voltage-controlling the PIN diodes D
2
and D
3
in the transmitting side circuit
25
; and CONT
2
a voltage control terminal for voltage-controlling the PIN diodes D
4
to D
6
in the receiving side circuit
26
. If applying a positive voltage to the voltage control terminals CONT
1
and CONT
2
, the PIN diodes D
2
to D
6
are turned on, and the antenna duplexer
1
operates at a LOW channel. In other words, as shown in
FIG. 10
, the passing band of the transmitting side circuit
25
is set to 1850 to 1880 MHz, and that of the receiving side circuit
26
is set to 1930 to 1960 MHz. On the contrary, if setting the control voltage to 0V to prevent a voltage from being applied to the voltage control terminals CONT
1
and CONT
2
, alternatively, applying a negative voltage to the voltage control terminals CONT
1
and CONT
2
, the PIN diodes D
2
to D
6
are turned off and the antenna duplexer
1
operates at a HIGH channel. That is, as shown in
FIG. 10
, the passing band of the transmitting side circuit
25
is set to 1880 to 1910 MHz and that of the receiving side circuit
26
is set to 1960 to 1990 MHz.
A cellular phone is set to a standby mode of a receiving wave for time excluding communication time. If the frequency of the receiving wave standby mode is equal to 1930 MHz and the cellular phone then enters the receiving wave standby mode while applying the positive voltage to the voltage control terminals CONT
1
and CONT
2
in the antenna duplexer
1
, there might be arisen problems such that a battery of the cellular phone is wasted fast and the receiving wave standby time becomes short.
With regard to the countermeasures against the foregoing, it is devised that the control voltage of the voltage control terminal CONT
1
is set to 0V and the positive voltage is applied only to the voltage control terminal CONT
2
. Thereby, a consumption current flows only to the receiving side circuit
26
for receiving wave standby mode and thus it is able to suppress the waste of the battery. However, in a system, e.g., the PCS such that the transmitting frequency band has a frequency lower than that of the receiving frequency band, if turning off the PIN diodes D
2
and D
3
in the transmitting side circuit
25
and turning on the PIN diodes D
4
to D
6
in the receiving side circuit
26
, as shown in
FIG. 11
, the separation is made extremely narrow between the passing band (1880 to 1910 MHz) in the transmitting side circuit
25
and the passing band (1930 to 1960 MHz) in the receiving side circuit
26
. As a consequence, it is made difficult to set the transmitting side circuit
25
to have a high impedance (become open) at the receiving frequency band of 1930 to 1960 MHz, thereby arising a new problem to increase a loss for inserting the receiving side circuit
26
.
FIG. 12
is a graph showing a result to measure a passing characteristic S
32
and a reflecting characteristic S
22
of the receiving side circuit
26
, when applying the positive voltage to the voltage control terminals CONT
1
and CONT
2
(refer to FIG.
8
). In this figure, the loss for inserting the receiving side circuit
26
is equal to 3.3 dB. By contrast,
FIG. 13
is a graph showing a result to measure the passing characteristic S
32
and the reflecting characteristic S
22
of the receiving side circuit
26
, when applying the positive voltage only to the voltage control terminal CONT
2
. Referring to
FIG. 13
, a waveform distortion is caused at a portion indicated by a circle A. In this figure, the loss for inserting the receiving side circuit
26
deteriorates to 5.0 dB.
SUMMARY OF THE INVENTION
To overcome the above described problems, preferred embodiments of the present invention provide a high-frequency circuit apparatus and a communication apparatus having a small consumption current and a low inserting loss.
One preferred embodiment of the present invention provides a high-frequency circuit apparatus comprising:
an antenna duplexer of a frequency variable type having a first external terminal, a second external terminal, and an antenna terminal;
a first change-over switch which is electrically connected to the antenna terminal;
a second change-over switch which is electrically connected to the second external terminal; and
a filter which is electrically connected across the first change-over switch and the second change-over switch. Herein, the first external terminal is, e.g., a transmitting terminal, the second external terminal is, e.g., a receiving terminal, and the filter

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