CN101364791A

CN101364791A - Low noise amplifier with multiband variable gain

Info

Publication number: CN101364791A
Application number: CNA2007102012982A
Authority: CN
Inventors: 李俊
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-08-07
Filing date: 2007-08-07
Publication date: 2009-02-11

Abstract

The invention discloses a low-noise amplifier capable of achieving adjustable multiband gain. The circuit has a frequency spectrum coverage range of 820 MHz to 2,200 MHz. The circuit can also provide different gain modes according to the intensity of received signals. The low-noise amplifier adopting IC design supports a plurality of mobile communication protocols, and has the advantages of small size, low power consumption, high linearity, high reliability, signal conversion, etc. The low-noise amplifier suits solving the problems such as multimode in the communication field and reception and amplification of wideband wireless signals.

Description

A kind of low noise amplifier of multiband variable gain

Technical field

The present invention relates to the wireless coverage technology of the communications field, particularly be to have a low noise amplifier that switch control gain and multiband are selected in the receiving system in the wireless communication system.

Background technology

The present mobile communication protocol mode is various, just comprises PHS in second generation mobile communication, and GSM (900MHz, 1800MHz, 1900MHz), and CDMA (IS95), the 3G (Third Generation) Moblie standard comprises CDMA2000, WCDMA, TD-SCDMA again.In the predictable quite a long time, the service of the mobile communication of these mode standards all will be present in our actual life.Based on such market demand, make the LNA that can be applied to a plurality of frequency ranges receive much concern at present.

Low noise amplifier is the major part of radio-frequency receiver front-end, and it is positioned at receiver foremost, and this just requires its noise the smaller the better.For the influence of the noises at different levels that suppress the back to system, also require to have certain gain, but, produce nonlinear distortion in order not make the frequency mixer overload of back, its gain is unsuitable excessive again.When signal was strong, the system linearity degree required just strict, and gain just more can not be too high.So the LNA of gain-variable also is trend of the times.

Summary of the invention

Goal of the invention of the present invention is, at the demand of existing market and the deficiency of technology, proposed to realize the LNA of three kinds of gain mode adjustable multibands, to improve the dynamic range that gains in the radio receiver, the integrated level of increase system, the cost of reduction system.

Above-mentioned purpose of the present invention is achieved by the following technical solution:

Fig. 1 is the low noise amplifier structured flowchart of the integrated multiband with switch control gain.It comprises biasing control (bias control) circuit and two cascode level amplifiers." bias control " circuit (as shown in Figure 3) is the switching that is used for realizing frequency band.Two cascode level amplifiers have been realized the amplification to the different frequency bands signal.The LNA physical circuit of single frequency band as shown in Figure 2.Describe each part of described low noise amplifier below in detail.

As shown in Figure 3, it is by transistor Q1 that described signal amplifies branch road, and inductance L e and feedback branch (Rf1 and C1) are formed.Metal-oxide-semiconductor M1 and inductance L 1 are the bypass path.When R0 (2) is high level, the M1 conducting, signal is by L1, and M1 flows to output.By regulating the size of M1 and inductance L 1, satisfy 50 ohm coupling.Circuit is realized the bypass pattern.As R0 (2) when being low level, M1 ends, and signal amplifies by transistor Q1.When R0 (1) was high level, M2 ended, and feedback loop is made up of Rf1 and C1." Cain control " circuit (as shown in Figure 4) disconnects Rload and load, and load is by Lc, C2, and C3 forms.At this moment, circuit provides maximum gain.As R0 (1) when being low level, the M2 conducting, the R1 feedback that makes in parallel with feedback loop (Rf1 and C1) puts more effort, and gain descends." Cain control " circuit with Rload resistance and load by Lc, C2, the C3 parallel connection, load diminishes, gain descends.This moment, circuit provided lower gain.

The present invention has following advantage and effect with respect to prior art:

(1). the present invention supports various communications protocols, and as PHS, GSM, CDMA, WCDMA, CDMA2000, TD-SCDMA etc., its RF spectrum coverage reaches 820MHz～2200MHz.

(2). the present invention adopts integrated circuit (IC) design, realizes that on the basis of chip-scale circuit multiband is multiplexing, and three kinds of gain modes are adjustable.It is little, low in energy consumption to have volume, the integrated level advantages of higher.

(3). the input and output matching network in the circuit can be applied to three kinds of different gain modes.

(4). based on the advantage of above-mentioned multi-protocols and integrated circuit, can be on integrated circuit of the present invention basis, the design correspondent peripheral circuit, connect to form the indoor covering system of wireless signal with other equipment, Kai Fa indoor covering system has simple in structure thus, and applied widely, can support characteristics such as various communications protocols.

Description of drawings

Fig. 1 is a chip design structure chart of the present invention

Fig. 2 is single LNA physical circuit design

Fig. 3 is a bias control circuit

Fig. 4 is a load control circuit

Fig. 5 current biasing circuit

Embodiment

The receiving system operation principle that this invention chip constitutes is: far-end access unit antenna receives the mobile radio station RF signals transmitted by duplexer Diplexer, delivers to receiver section.The signal that antenna receives at first carries out low noise by the outer low noise amplifier of sheet and amplifies, and enters into the receiving unit of transceiving chip then through RF Filter.Chip of the present invention is the first order of receiving unit.Chip of the present invention is integrated two low noise amplifier LNA, LNA1 realizes that the channel signals low noise of GSM900 and CDMA amplifies, and LNA2 realizes that the low noise of GSM1800, PHS and 3G application channel signal amplifies, during chip operation, have only a LNA operate as normal, another one LNA is closed.Radiofrequency signal after LNA amplifies is sent into the rf inputs of two down-conversion mixers simultaneously by radio frequency buffering device (RF Buffer).Intermediate-freuqncy signal through frequency mixer and image removing circuit generation is sent outside the sheet, carries out intermediate frequency filtering, and intermediate-frequency filter is selected the sheet outer filter of high selectivity, effectively the inhibition zone external signal.Deliver to variable gain amplifier in the chip again through the intermediate-freuqncy signal after the intermediate-frequency filter selection, change amplifier gain by digital control, thereby make final intermediate frequency stable output signal.Deliver to common house cable by matched filter then, as CAT-5.

Technical characterictic

Can amplify and suppress noise multiple mobile communication protocol mode signal (PHS, GSM, CDMA etc.).

Can realize the adjustable of three kinds of gain modes of signal.

All can realize 50 ohm input and output coupling for different mode.

Adopt band gap reference (Bandgap) that biasing is provided.

As mentioned above, be preferred forms of the present invention.Although described example has been represented and has been described the present invention, but do not represent restriction to the present invention self, those skilled in the art should be understood that, under the prerequisite of the spirit and scope of the present invention that do not break away from the claims definition, can make various variations at it, appending claims has covered all such changes and modifications in the spirit and scope of the invention in form and on the details.

Claims

The low noise amplifier that [claim 1] a kind of multiband has switch control gain is characterized in that: realized the selection of frequency band by bias control circuit.Realize the adjustable of gain by switch Control and Feedback and load.
The described bias control circuit of [claim 2] claim 1, SPI provides control signal by serial communication protocol.The break-make of two LNA bias currents of bias control circuit control is for the LNA of required frequency range provides bias current and the bias current of another LNA closed (it is not worked).
[claim 3] low noise amplifier according to claim 1 is characterized in that described signal amplifies a route transistor Q1, and inductance L e and feedback branch (Rf1 and C1) are formed.
[claim 4] low noise amplifier according to claim 1 is characterized in that bypass props up route metal-oxide-semiconductor M1 and inductance L 1 is formed.
The described Gain Adjustable of [claim 5] claim 1 is characterized in that by M2 Control and Feedback loop, by the size of " load control " circuit control load.
[claim 6] low noise amplifier according to claim 1 is characterized in that described current biasing circuit provides the direct current biasing of amplifier.