JP2003069440A - Portable telephone set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a portable telephone set that can be downsized and save power consumption without deteriorating disturbance characteristics. SOLUTION: The portable telephone set is provided with a low noise amplifier 2 provided in a receiver side RF stage front end section, a mixer circuit 7, and a current switching control circuit 6 that controls a source current of the low noise amplifier 2 and a feeding current to the mixer circuit according to the communication power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile phone, and more particularly to improvement of an RF stage front end portion in a CDMA mobile phone.

[0002]

[Prior Art] CDMA (Code Division Multiple Acces)
The s) method is one of multiple access methods in which a plurality of mobile stations connect to one base station, and each mobile station is identified using a unique code. This system, which is also called a spread spectrum system, disperses a signal to be transmitted in a wide range of spectrum of the entire usable frequency band and transmits it. For this reason, the signals of all stations are superimposed and transmitted in the same frequency band, but since a unique code is used for each station, they can be identified without interference. CDMA system is also known as multiple access system
It is said that it is more resistant to interference and obstruction than FDMA and TDMA methods, has high confidentiality, and has a large number of channels.
It has been put to practical use in many countries, including Japan and North America.

On the other hand, on the other hand, the intermodulation interference ratio is defined by the standard for interference / interference due to signals between multiple stations in cells having the same frequency used in the same cell and having different frequencies. . Especially 8
In the cellular band of 00MHz, it is specified for three-step input of a desired signal, and in order to satisfy this, as a method of coping with interference / interference mainly caused by a mixer circuit, an LNA A circuit for controlling the gain of a low noise amplifier) is well known.

[0004]

By the way, when the miniaturization of mobile phones has been prioritized as in recent years, the distance between the transmitting circuit and the receiving circuit becomes short inside the mobile phone. , The isolation of the transmission signal from the receiving circuit becomes insufficient, and the standard of the single tone interference ratio cannot be satisfied. An example of the mechanism that deteriorates is that a modulation component of the transmission signal occurs in the interfering signal at the time of single-tone measurement (caused by the third-order term of the nonlinear element called cross modulation), and part of this modulation component is the IF band of the reception. It falls inside and appears as distortion of the desired signal.
Therefore, it is essential for mobile phones to reduce cross modulation.

In addition to the above, along with the downsizing of mobile phones, it has been required to reduce the battery size, and as a result, lowering the power consumption of the entire set has become an important issue. It is an object of the present invention to provide a mobile phone which compensates for deterioration of isolation due to miniaturization and contributes to miniaturization and power saving.

[0006]

[Means for Solving the Problems] To achieve the above object,
The mobile phone according to the present invention includes a low-noise amplifier provided in a high-frequency circuit, a mixer circuit that mixes a high-frequency signal that has passed through the low-noise amplifier with a local signal, the magnitude of the source current of the low-noise amplifier, and the supply current to the mixer circuit. It is characterized in that it is provided with a current switching control circuit for controlling the magnitude according to the magnitude of the transmission power.

Here, the mobile phone performs power control with the radio base station to keep the relationship between the transmission power and the reception power constant, and the current switching switching control circuit controls the reception signal level during a call. Is greater than the reference value, the first current is supplied, and when the received signal level is less than or equal to the reference value, the first current is supplied.
It is possible to adopt a configuration in which switching is performed so as to supply a second current larger than the current of.

Further, the current switching control circuit is a bias circuit connected to the source terminal of the low noise amplifier and the mixer circuit, and the value of the bias resistance in the bias circuit is adjusted to a large or small value to adjust the magnitude of the bias current of each circuit. It is characterized by controlling. Further, the current switching control circuit includes a first main bias circuit for supplying a bias current to the source terminal of the low noise amplifier, a second main bias circuit for supplying a bias current to the mixer circuit, and a telephone having a predetermined power or more. When in communication with power, the first
And a first sub-bias circuit that supplies bias current in a superposed manner, a second main bias circuit, and a second sub-bias circuit that supplies bias current in a superposed manner. it can.

[0009]

1 is a diagram showing an RF stage front end portion of a receiver circuit of a mobile phone according to an embodiment of the present invention. In the figure, reference numeral 1 is a duplexer, one terminal of which is connected to an antenna, another one of which is connected to a transmission circuit, and another of which is connected to a reception circuit. Reference numeral 2 is a low noise amplifier, and 3 is a SAW filter as an example of a high frequency filter. A mixer circuit 7 is connected to the output side of the SAW filter to mix the signal transmitted by the local oscillator circuit 8 with the received signal and reduce the frequency to an intermediate frequency.

The duplexer 1 and the low noise amplifier 2
An input matching circuit 4 of the low noise amplifier 2 is provided between the two, and an output matching circuit and bias supply circuit 5 of the low noise amplifier 2 is provided between the low noise amplifier 2 and the SAW filter 3. The low noise amplifier 2 is, for example,
The Ga-As type FET is provided with a bias circuit 6 at its source terminal. The bias circuit 6 includes a main bias circuit 61, a sub bias circuit 62, and a sub bias circuit 62.
And a switch circuit 63 for turning on and off.

The main bias circuit 61 is the Ga-As type FET.
Resistor R that generates a DC bias voltage applied to the source of
1 and bypass capacitors C4 and C5 that bypass the high frequency component flowing from the source terminal. The bias voltage generated by the main bias circuit 61 is V
1 and the bias current is I1. Sub bias circuit 62
Is composed of a resistor R2.

The switch circuit 63 includes two FET switches T
It consists of r1 and Tr2. The IDLE signal and the LNA control signal are input to the gates of the FET switches Tr1 and Tr2, respectively. On the other hand, the bias circuit 8 of the mixer circuit 7 is also provided with a similar main bias circuit 81, a sub bias circuit 82, and a switch circuit 83. Main bias circuit 8
Reference numeral 1 denotes a bias resistor R5, which is a sub bias circuit 82.
Is a resistor R6, and the switch circuit 83 is a FET switch Tr3.
Is. The FET switch Tr3 is connected in parallel with the FET switch Tr1 to the source of the FET switch Tr2. Therefore, the bias circuit 9 of the mixer circuit 7 switches between a single resistor and a parallel circuit of two resistors at the same timing as the bias circuit of the low noise amplifier 2.

The IDLE signal is a signal indicating whether the mobile phone is in the transmitting state or the non-transmitting state. In the non-transmitting state, the IDLE signal is Low and the transmitting state is High. In CDMA system, it is in non-transmission state during standby reception and during communication (transmission and reception)
It corresponds to the transmission state. The LNA control signal becomes High when the transmission output is lower than the predetermined power (when the reception signal level is higher than the reference value), and becomes Low when the transmission output is higher than the predetermined power (when the reception signal level is equal to or lower than the reference value).
In the CDMA system like the mobile phone according to the present embodiment, power control is performed to keep the relationship between the transmission power and the reception power constant with the radio base station, so whether the transmission output is smaller or larger than the predetermined power is determined. , It is determined by whether the received signal level is larger than the reference value or small. This determination is made by MSM (Mobil Station MODEM) (not shown) inside the mobile phone.

The relationship between the transmission power and the reception power in the above power control can be simplified to be (average transmission power) + (average reception power) = almost constant value (for example, −76 dBm). The details of the power control are standardized as an open-loop estimation performed by the mobile station and a closed-loop correction performed by both the mobile station and the radio base station. Also, the above constant value is -76.
In the case of dBm, the above predetermined power is, for example, 15 dBm.
(In this case, the above reference value is -91 dBm). In this case, the LNA control signal becomes High when the received signal level is higher than -91 dBm, and becomes Low when the received signal level is equal to or lower than -91 dBm.

The FET switches Tr1 (Tr3) and Tr2 are turned on and off depending on the states of the IDLE signal and the LNA control signal, as shown in the table below.

[0016]

[Table 1]

As can be seen from the above table, the FET switches Tr1 and Tr3 are turned on when the transmission output is higher than the predetermined power, and turned off otherwise. When the FET switches Tr1 and Tr3 are turned on, the sub bias circuits 62 and 9
2 is turned on, and the resistors R2 and R6 are connected in parallel with the resistors R1 and R5 of the main bias circuits 61 and 91. Therefore, the bias voltage and bias current supplied to the source of the Ga-As type FET of the low noise amplifier 2 and the bias voltage and bias current supplied to the mixer circuit 7 are two resistors R1 and R2 (R
5, R6) is determined by the combined resistance value. At this time, the bias voltage of the bias circuit 6 is V2 and the bias current is I2. The bias circuit 9 is not related to the IIP3 characteristic, so its explanation is omitted here.

FIG. 2 shows an example of the characteristic curve of the IIP3 with respect to the bias current of the low noise amplifier 2, and FIG.
Shows an example of the characteristic curve of IIP3 with respect to the bias voltage. As can be seen from these figures, the IIP3 characteristic has little dependence on the bias voltage and high dependence on the bias current. In the present embodiment, attention is paid to the fact that IIP3 has a high dependence on the bias current and a low dependence on the bias voltage.
The value of 2 is set appropriately. That is, the main bias circuit 6
When the bias current is supplied only by 1, the current value I1 is shown by the bias point 1 in FIG. 2, and when the bias current is supplied by both the main and sub bias circuits 61 and 62, the bias value shown in FIG. Current value I2 indicated by point 2
I am trying. As a result, IIP3 for bias current I1
Is -2.5 dBm, while I2 is 6.5.
This means an increase of approximately 9.0 dB in dBm.

In FIG. 2, I3 indicates the value of the bias current that has sufficient circuit space and satisfies the isolation. Bias current I1 of the present embodiment
Is less than this value and I2 is greater than that value. Since the bias current I1 is smaller than I3, the power consumption becomes lower than that in the conventional case during standby or when the transmission power is low. In the case of the present embodiment, the bias circuit 9 of the mixer circuit 7
Is also switched in the same manner as the low noise amplifier 2, so the power consumption during standby and low transmission power is further reduced. The measurement result of the current value is as follows.

[0020]

[Table 2]

[0021] Normally, the standby time is much longer than the call time in the mobile phone, and therefore, from the above table, the mobile phone according to the present embodiment also contributes to prolonging the life of the battery or reducing the size of the battery itself. I understand. In the above embodiment, the resistors R1 and R2 are connected in parallel in FIG. 1, but they may be connected in series. That is, instead of the resistor R2, a resistor R2 ′ is connected in series with the resistor R1, and a transistor Tr1 is connected in parallel to the resistor R2 ′ (both ends of the resistor R2 ′ and the drain terminal and source terminal of Tr1 are connected). It may be configured to. However, in this case, the series combined resistance of R1 and R2 changes the bias current I1 to
The resistance value is set so that the resistor R1 gives the bias current I2. This can also be applied to the bias circuit 9 of the mixer circuit 7, and a similar connection configuration can be made.

Further, in FIG. 1, the bias current is switched in two stages, but it may be switched in three stages or more.

[0023]

As described above, the mobile phone according to the present invention includes a low noise amplifier provided in a high frequency circuit,
A mixer circuit that mixes a local signal with a high-frequency signal that has passed through a low noise amplifier, and a current switching control that controls the magnitude of the source current of the low noise amplifier and the magnitude of the current supplied to the mixer circuit according to the magnitude of the transmission power. Since the circuit is configured to include the circuit, the intersection of the desired signal and the disturbing signal in the IIP3 characteristics of the low noise amplifier moves according to the magnitude of the transmission power, and the desired signal and the disturbing signal are detected even when the communication power is large. It is possible to identify and secure good anti-jamming characteristics, and it has the effect of being suitable for further miniaturization by bringing the high-frequency transmitter circuit and the high-frequency receiver circuit closer together, and it is also possible to reduce the power consumption of the low-noise amplifier and mixer circuit. There is also an effect that it is possible to use a battery of a smaller size.

[Brief description of drawings]

FIG. 1 is a diagram showing a high frequency circuit portion of a receiving circuit of a mobile phone according to an embodiment of the present invention.

FIG. 2 is a diagram showing IIP3 characteristics with respect to a source current of a low noise amplifier.

FIG. 3 is a diagram showing IIP3 characteristics with respect to a source voltage of a low noise amplifier.

[Explanation of symbols]

1 ... Duplexer, 2 ... Low noise amplifier, 3 ... SAW filter, 4 ... Input matching circuit, 5 ... Output matching circuit and bias supply circuit, 6 ... Bias circuit, 7 ... -Mixer circuit, 8 ... Local oscillation circuit, 9 ... Bias circuit, 61 ... Main bias circuit, 62 ... Sub bias circuit, 63
... Switch circuit, 91 ... Main bias circuit, 92 ... Sub bias circuit, 93 ... Switch circuit.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5K011 DA01 DA03 DA06 DA12 EA03                       FA03 GA06 JA01 KA03 KA05                 5K020 AA08 DD03 DD05 DD13 EE01                       EE07 FF00 GG00 LL01                 5K052 AA01 AA11 BB01 CC06 DD19                       FF00 GG02 GG12 GG26 GG35                 5K067 AA43 BB04 DD44 GG08 GG09

Claims (6)

[Claims] 1. A low noise amplifier provided in a high frequency circuit, a mixer circuit for mixing a high frequency signal passing through the low noise amplifier with a local signal, a magnitude of a source current of the low noise amplifier and a magnitude of a current supplied to the mixer circuit. A mobile phone, comprising: a current switching control circuit that controls according to the magnitude of transmission power. 2. The current switching control circuit supplies a first current when the telephone is in a standby state or in a transmission state with a power lower than a predetermined power, and when the telephone is in a transmission state with a power equal to or higher than a predetermined power, the first current control circuit supplies the first current. The mobile phone according to claim 1, wherein the mobile phone is configured to switch so as to supply a second current larger than the current. 3. The mobile phone performs power control for maintaining a constant relationship between transmission power and reception power with a radio base station, and the current switching switching control circuit is configured to receive a signal level during a call. Is greater than the reference value, the first
2. The mobile phone according to claim 1, wherein the mobile phone is configured to switch to supply a second current larger than the first current when the received signal level is equal to or lower than the reference value. 4. The current switching control circuit is a bias circuit connected to a source terminal of a low noise amplifier and a mixer circuit, and adjusts the value of a bias resistance in the bias circuit to adjust the magnitude of the bias current of each circuit. The mobile phone according to claim 1, wherein the mobile phone is controlled. 5. The current switching control circuit comprises: a first main bias circuit for supplying a bias current to a source terminal of a low noise amplifier; a second main bias circuit for supplying a bias current to a mixer circuit; A first sub-bias circuit that supplies a bias current in a superposed manner with the first main bias circuit and a second sub-bias circuit that supplies a bias current in a superposed manner with the second main bias circuit when in a communication state with electric power equal to or higher than the electric power. 5. The mobile phone according to claim 4, further comprising: 6. The mobile phone according to claim 5, wherein the communication system of the mobile phone is a CDMA system.