Title: Multi-band amplifier
Abstract: In a multi-band amplifier, provided are a first differential voltage-to-current converting circuit for converting a first frequency signal into a current and outputting the current, a second differential voltage-to-current converting circuit for converting a second frequency signal into a current and outputting the current, and a current transposition point connected in phase with and in parallel with output terminals of the first and second differential voltage-to-current converting circuits. A base-grounded amplifying circuit is connected in phase with and in series with an output terminal of the current transposition point. With this configuration, the circuit of a virtual ground point and the following of after voltage-to-current conversion can be provided in common by using a cascode amplifier as a low-noise amplifier, making it possible to constitute a multi-band amplifier minimized in the connection loss resulting from interconnection.
Patent Number: 6,909,325 Issued on 06/21/2005 to Saito
| Inventors:
|
Saito; Noriaki (Tokyo, JP)
|
| Assignee:
|
Matsushita Electric Industrial Co., Ltd. (Osaka, JP)
|
| Appl. No.:
|
695042 |
| Filed:
|
October 28, 2003 |
Foreign Application Priority Data
| Oct 29, 2002[JP] | 2002-313916 |
| Current U.S. Class: |
330/126; 330/124R; 330/252 |
| Intern'l Class: |
H03F 003/68 |
| Field of Search: |
330/126,124.R,252
|
References Cited [Referenced By]
U.S. Patent Documents
| 4220974 | Sep., 1980 | Craft.
| |
| 5339458 | Aug., 1994 | Nakatsuka et al.
| |
| 5715532 | Feb., 1998 | Sagawa et al.
| |
| 6496545 | Dec., 2002 | Liu.
| |
| 2005/0005296 | Jan., 2005 | Bargroff et al.
| |
| Foreign Patent Documents |
| 2000/-124829 | Apr., 2000 | JP.
| |
Primary Examiner: Nguyen; Patricia
Attorney, Agent or Firm: RatnerPrestia
Claims
1. A multi-band amplifier comprising:
a first differential voltage-to-current converting circuit for converting a first
frequency signal into a current signal;
a second differential voltage-to-current converting circuit for converting a
second frequency signal into a current signal;
a current transposition point connected in phase with and in parallel with output
terminals of the first and second differential voltage-to-current converting circuits;
and
a base-grounded amplifying circuit connected in phase with and in series with
an output terminal of the current transposition point.
2. A multi-band amplifier according to claim 1, wherein the base-grounded amplifying
circuit includes a base-grounded transistor grounded at a base thereof by the base-grounded capacitance.
3. A multi-band amplifier according to claim 1, wherein each of the first and
second differential voltage-to-current converting circuits includes an RF operating
section having a differential amplifying circuit, a direct-current bias circuit
formed by a current mirror circuit, and an RF blocking resistance inserted in series
in a manner separating between the RF operating section and the direct-current
bias circuit.
4. A multi-band amplifier according to claim 1, wherein each of the first and
second differential voltage-to-current converting circuits includes an RF operating
section having a differential amplifying circuit and a direct-current bias circuit
formed by a current mirror circuit, to directly connect between the RF operating
section and the direct-current bias circuit.
5. A multi-band amplifier according to claim 1, wherein the first differential
voltage-to-current converting circuit includes a first RF-current differential
output terminal, and the second differential voltage-to-current converting circuit
includes a second RF-current differential output terminal and the current transposition
point includes an RF-current differential input terminal whereby, in the case the
first frequency is higher than the second frequency, the RF-current transposition
point is connected with a transposition line by a wiring in an upper level at between
the first RF-current differential output terminal and the RF-current differential
input terminal of the RF-current transposition point and by a wiring in a lower
level at between the second RF-current differential output terminal and the RF-current
differential input terminal of the RF-current transposition point.
6. A multi-band amplifier according to claim 1, further comprising one or a plurality
of differential voltage-to-current converting circuits for converting a signal
having a frequency different from the first and second frequencies into a current signal.
Description
FIELD OF THE INVENTION
This invention relates to a multi-band amplifier for use mainly in various kinds
of radio units, communication apparatuses, measuring instruments and so on.
BACKGROUND OF THE INVENTION
In the market of the cellular telephones in the GSM scheme as a de-facto standard,
there is an increasing, indispensable need for those using the multi-band amplifiers,
such as dual bands, in order for expanding the service area.
FIG. 1 is a schematic block connection diagram showing a configuration example
of a conventional dual-band amplifier described in JP-A-2000-124829. The signal
radio wave in a frequency band f1 is received by an f1-band input
terminal 1000 and then removed of the interfering waves in the other band
than f1 by a f1-band BPF (band-pass filter) 1002. Then, the
signal is amplified to a desired level by an f1-band low-noise amplifier
1004 and inputted to one input terminal of a radio-frequency change-over
switch 1006. On the other hand, the signal radio wave in a frequency band
f2 is received by an f2-band input terminal 1001 and then
removed of interfering waves in the other band than f2 by a f2-band
BPF 1003. The signal is amplified to a desired level by an f2-band
low-noise amplifier 1005 and inputted to the other input terminal of the
radio-frequency change-over switch 1006. The radio-frequency change-over
switch 1006 selects either one of the inputted f1-band or f2-band
signal. The selected f1-band or f2-band signal is orthogonally demodulated
by an orthogonal demodulating section 1007. In this manner, the orthogonal
demodulating section 1007 is shared between the two frequency bands. In
the case there exist three or more frequency bands, the orthogonal demodulating
section 1007 is shared by a change-over selection at the radio-frequency
change-over switch 1006.
In the configuration sharing an orthogonal demodulating section by using the
radio-frequency
change-over switch 1006, two of the low-noise amplifiers 1004, 1005
are required independently. Furthermore, loss is possibly caused by the radio-frequency
change-over switch 1006.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to realize a low-loss
multi-band amplifier by the utilization of a virtual ground point of a cascode amplifier.
An amplifier of the present invention comprising: a first differential voltage-to-current
converting circuit for converting a first frequency signal into a current and outputting
the current; a second differential voltage-to-current converting circuit for converting
a second frequency signal into a current and outputting the current; a current
transposition point connected in phase with and in parallel with output terminals
of the first and second differential voltage-to-current converting circuits; and
a base-grounded amplifying circuit connected in phase with and in series with an
output terminal of the current transposition point. Due to this, a cascode amplifier
is used as a low-noise amplifier to thereby make common the circuit of a virtual
ground point and the following of after voltage-to-current conversion. This configuration
makes it possible to constitute a multi-band amplifier minimized in the connection
loss resulting from interconnection.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block connection diagram of a conventional dual-band amplifier;
FIG. 2 is a block connection diagram of a dual-band amplifier in embodiment
1 of the present invention;
FIG. 3 is a circuit diagram of a differential voltage-to-current converting
circuit used in the dual-band amplifier of FIG. 2;
FIG. 4 is a connection diagram of an RF-current transposition point used in
the dual-band amplifier of FIG. 2; and
FIG. 5 is a circuit diagram of a differential voltage-to-current converting
circuit used in the dual-band amplifier of embodiment 2 of the invention.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
Exemplary embodiments of the present invention are demonstrated hereinafter
with reference to the accompanying drawings. Incidentally, the below embodiment
exemplifies a dual-band amplifier as one kind of the multi-band amplifiers.
1. First Exemplary Embodiment
FIG. 1 shows a block connection diagram of a dual-band amplifier. In FIG. 1,
the dual-band amplifier
100 is configured with a differential voltage-to-current
converting circuit
110 corresponding to a signal in a frequency band f
1,
a differential voltage-to-current converting circuit
120 corresponding to
a signal in a frequency band f
2, an RF(Radio Frequency)-current transposition
point
130 and a base-grounded amplifying circuit
140.
The differential voltage-to-current converting circuit
110 has an RF-voltage
differential input terminal
111 and an RF-current differential output terminal
112. The radio-frequency voltage having a frequency f
1 and inputted
at the RF-voltage differential input terminal
111 is converted into a radio-frequency
current in the differential voltage-to-current converting circuit
110 and
then outputted to the RF-current differential output terminal
112. Likewise,
the differential voltage-to-current converting circuit
120 has an RF-voltage
differential input terminal
121 and an RF-voltage differential output terminal
122. The radio-frequency voltage having a frequency f
2 and inputted
at the RF-voltage differential input terminal
121 is converted into a radio-frequency
current in the differential voltage-to-current converting circuit
120 and
then outputted to the RF-current differential output terminal
122.
The base-grounded amplifying circuit
140 has base-grounded transistors
150,
160, base-ground capacitances
151,
161, a driving
power source
143, a base-bias power source
144, a bias resistance
145, and load resistances
152,
153. The radio-frequency current
inputted at the RF-current differential input terminal
141 is converted
into a voltage and then outputted to the voltage differential output terminal
142.
The RF-current transposition point
130 is connected in parallel with and
in phase with the RF-current differential output terminals
112,
122,
and furthermore connected in series with and in phase with the RF-current differential
input terminal
141.
Now, explanation is made on the operation of the dual-band amplifier
100
configured as above.
In the case that a signal having a frequency f
1, for example, is selected,
the differential voltage-to-current converting circuit
110 turns ON and
the differential voltage-to-current converting circuit
120 turns OFF. The
radio-frequency signal f
1 inputted at the RF-voltage differential input
terminal
111 of the differential voltage-to-current converting circuit
110
is converted into a radio-frequency current by the differential voltage-to-current
converting circuit
110 and then outputted to the RF-current differential
output terminal
112. The outputted radio-frequency current is inputted through
the RF-current transposition point
130 to the base-grounded amplifying circuit
140 at the RF-current differential input terminal
141. In the base-grounded
amplifying circuit
140, the base-grounded transistors
150,
160
are properly biased at a common base thereof by the base-bias power source
144
and bias resistance
145, the base of which is RF-grounded by the base-ground
capacitance
151,
161. The base-grounded transistor
150,
160
has an output connected with the load resistance
152,
153. Consequently,
the radio-frequency current inputted to the RF-current differential input terminal
141 is voltage-converted by the base-grounded amplifying circuit
140
and then outputted as a voltage signal onto the RF-voltage differential output
terminal
142.
Likewise, in the case that a signal having a frequency f
2 is selected,
the differential voltage-to-current converting circuit
120 turns ON and
the differential voltage-to-current converting circuit
110 turns OFF. The
radio-frequency signal f
2 inputted at the RF-voltage differential input
terminal
121 of the differential voltage-to-current converting circuit
120
is converted into a radio-frequency current by the differential voltage-to-current
converting circuit
120 and then outputted to the RF-current differential
output terminal
122. The outputted radio-frequency current is inputted through
the RF-current transposition point
130 to the base-grounded amplifying circuit
140 at the RF-current differential input terminal
141. In this case,
because the RF-current differential output terminal
122 is connected in
parallel with and in phase with the RF-current differential output terminal
112
through the RF-current transposition point
130, the RF-current differential
input terminal
141 can be inputted by a signal at a radio-frequency current
in the same phase regardless of the frequency band f
1, f
2. The radio-frequency
current inputted to the RF-current differential input terminal
141 is similarly
voltage-converted by the base-grounded amplifying circuit
140 and then outputted
as a voltage signal onto the RF-voltage differential output terminal
142.
In the above configuration, the RF-current differential output terminals
112,
122, the RF-current transposition point
130 and the RF-current differential
input terminal
141 can all be considered as radio-frequency virtual ground
points by the operation of the base-ground capacitances
151,
161.
This can suppress to the minimum extent the influences of transmission lines and
off-sided circuits, as compared to the conventional circuit extending the output
with high impedance.
FIG. 2 shows a circuit diagram of the differential voltage-to-current converting
circuit
111,
121. Although FIG. 2 exemplifies the differential voltage-to-current
converting circuit
111, the differential voltage-to-current converting circuit
121 is quite same in configuration.
The differential voltage-to-current converting circuit
111 is configured
with a direct-current bias circuit
250 and an RF operating section
240.
The direct-current bias circuit
250 is configured with a power source
251,
transistors
252,
253, resistances
254,
255, a reference
current source
256, a current reference transistor
257, a base-current
compensating transistor
258 and a bias resistance
261. The RF operating
section
240 is configured with an RF differential-voltage differential input
terminal
111, an RF current differential output terminal
112, transistors
210,
220 for voltage-to-current conversion, a feedback inductor
211
for improving the linearity without deteriorating the noise factor, and a feedback
inductor
241 effective for improving the in-phase-noise removal ratio. The
direct-current bias circuit
250 and the RF operating section
240
are connected together by RF blocking resistances
262,
263.
In the case the differential voltage-to-current converting circuit
111
is selected, a reference current flows to the reference current source
256.
The reference current determines a current flowing through the current-reference
transistor
257 by a current-mirror circuit constituted by the transistors
252,
253 and the resistances
254,
255. Meanwhile, the
transistors
210,
220 of the RF operating section
240 constitute
a current-mirror circuit cooperatively with the current-reference transistor
257.
The base-current compensating transistor
258 makes a base-current compensation.
Furthermore, the resistance ratio of the bias resistance
261 and RF blocking
resistances
262,
263 is determined to a reciprocal of the current
ratio of the reference-current transistor
257 and transistors
210,
220. By selecting such a ratio, the voltage drop due to the base current
is made equal. This is effective for correcting for the hfe absolute variation
of transistor. Meanwhile, because the RF blocking resistances
262,
263
prevent noise source from leaking from the current bias circuit
250 to the
RF operating section
240, the RF operating section
240 can be set
with a direct-current bias without deteriorating the noise factor.
FIG. 3 shows a connection diagram of the RF current transposition point
130.
The RF current transposition point
130 is formed, for example, by the lower-level
signal lines
300,
301 using a second level of a three-layered wiring
of an integrated circuit and the upper-level signal lines
302,
303,
304,
305 using a third level thereof.
Where the frequency f
1 is higher than the frequency f
2, priority
is placed on the wiring of from the RF-current differential output terminal
112
to the RF-current differential input terminal
141 through which the frequency
f
1 is to pass, thereby making a wiring in the upper level having less parasitic
capacitance. The wiring, of from the RF-current differential output terminal
122
to the RF-current differential input terminal
141 through which the frequency
f
2 is to pass, uses the lower-level signal line
300 in the transposition
point, thereby reducing the loss on the frequency f
1 side to the minimum
extent. Furthermore, by providing the lower-level signal line
301 with the
same length as the length of the lower-level signal line
300, connection
is possible also on the frequency f
2 side without losing the balance. In
this manner, the wiring on the frequency f
1 side having higher frequency
and greater loss is provided in the upper level lower in parasitic capacitance
while the wiring on the frequency f
2 side is provided in the lower level.
This can configure a dual-band amplifier where the loss on the frequency f
1
side is reduced to the minimum extent.
2. Second Exemplary Embodiment
FIG. 5 shows a circuit diagram of a differential voltage-to-current converting
circuit of an amplifier in embodiment
2 of the invention. The other parts
than the differential voltage-to-current converting circuit of the amplifier are
similar to those of FIGS. 2 and 4. Meanwhile, in the differential voltage-to-current
converting circuit of FIG. 5, the same components as the constituent elements of
the differential voltage-to-current converting circuit of FIG. 3 are attached with
the same references, to omit explanations thereof. The difference from FIG. 3 lies
in the configuration of a direct-current bias circuit
410.
The direct-current bias circuit
410 is configured with a power source
251, transistors
252,
412,
422, resistances
254,
411,
421, base-current compensating transistors
413,
423,
current reference transistors
415,
425, RF blocking resistances
414,
424 and feedback resistances
416,
426.
In the case that the differential voltage-to-current converting circuit
111
is selected, a reference current flows to the reference current source
256.
The reference current determines a current flowing to the current reference transistor
415,
425 by a current mirror circuit formed by the transistors
252,
412,
422, and the resistances
254,
411,
421.
Meanwhile, the transistors
210,
220 of the RF operating section
240
configure current mirror circuits cooperatively with the current reference transistors
415,
425, respectively. The base-current compensating transistor
413,
423 makes a base-current compensation while the RF blocking
resistance
414,
424 blocks a high frequency signal from flowing into
the base-current compensating transistor
413,
423. Although a radio-frequency
current flows to the current reference transistor
416,
426, the linearity
can be enhanced by fully increasing the feedback resistance
416. Because
there is no necessity of a series resistance between the current reference transistor
415,
425 and the transistor
210,
220, even in the case
that there is large hfe relative variation between the transistors, the transistor
210,
220 can be secured with a current balance without causing a
voltage-drop difference based on a series resistance.
According to this embodiment, when the transistors have large hfe relative
variations, the current variations due to series resistances can be prevented,
to prevent the balance deterioration between the differentials.
As described above, according to the invention, the RF current transposition
point
130 is set up in the virtual ground point of a cascode amplifier, to parallel-connect
the virtual ground point of cascode amplifier with an amplifier which is adjacent
with respect to operating frequency band. Due to this, a dual-band amplifier can
be configured which is reduced to the minimum extent the connection loss due to
interconnection of the first and second differential voltage-to-current converting
circuits
110,
120.
Incidentally, the above embodiments exemplified the dual-band amplifier
having two differential voltage-to-current converting circuits. However, by providing
differential voltage-to-current converting circuits three or more, the circuit
can be shared as a multi-band amplifier at three or more adjacent frequency bands.
*
