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Two low-noise amplifier design

In Electronic Infomation Category: T | on April 15,2011

Low noise amplifier (LN A) is the RF transceiver is an important part of the receiver can effectively improve the receiver sensitivity, thereby increasing the transmission distance of the transceiver. Therefore, whether the design of low noise amplifier good of the entire communications system of communication quality. In this paper, the transistor ATF54143 illustrate two different low-noise amplifier design, the frequency range of 2 ~ 2. 2 GHz; transistor voltage is 3 V; operating current is 40 mA; input and TDA6060XS datasheet and output impedance of 50.

1 qualitative analysis

1. 1 transistor modeling

Through the network can access the relevant information transistors manufacturers, which can be downloaded transistor model provided by the manufacturer, or you can download the tube according to the actual needs of the S2P file. In this case the tube by direct S2P file into the software, using S parameters for the modeling circuit. If this is the first import, you can use S-parameter simulation module SParams, observed S-parameter data provided with the S2P file is the same at the same time, measuring the input impedance of the transistor and TDA6060XS price and the corresponding minimum noise figure, and TDA6060XS suppliers and determine the stability of the transistor etc., to prepare for the next step.

1. 2 transistor stability

S parameter simulation of the circuit to complete, you can get input / output of the mu frequency 2 ~ 2. 2 GHz is less than 1 between, according to the theory of radio, the transistor is unstable. Parallel at the output of a 10 and 5 pF of capacitance, m2 and m3 of values ??greater than 1, as shown in Figure 1, Figure 2. Transistors to achieve stable conditions in the bandwidth, and measured at 2. 1 GHz when the input impedance of 16. 827 - j16. 041. Also found that the output due to join the resistance, making Fmin from the 0.48 increased to 0. 573, Topt is 0. 329 125. 99 , Zopt = (30. 007 + j17. 754) . Which, Topt is the best source reflection coefficient.


Figure 1 using the simulation module SParams schematic


Figure 2 Input / Output mu vs. frequency

1. 3 development program

Shown in Figure 3, will be available gain and noise figure of Circle Group Circle Group on paintings in the same Ts plane. Through analysis shows that, if available gain circles through the best location of the point where the noise figure, and according to the input point for the circuit match, this time for the LNA, the noise factor is minimal, but the gain did not reach the most good amplification. So it is available through the expense of the gain in exchange. In this case, the transistor gain can reach 14 dB or so, Fmin is about 0.48, shown in Figure 3.

Another solution is to gain and noise figure of the available balance as possible to match the target with a small noise, the use of context in both the design of the gain. In this case, the gain of the transistor is about 15 dB or so, Fmin is about 0.7 (see Figure 3). This is mentioned in this article 2 of the kinds of programs.


Figure 3, the same is available on the Ts plane gain and noise figure of Circle Group Circle Group.

2 best noise figure target for the design of the simulation program

2. 1 input matching circuit design

For low-noise amplifier, in order to obtain the minimum noise figure, Ts have the best Topt coefficient, minimum noise figure LNA at this time, that the best noise match condition. When the state deviation from the best match position, LNAs noise figure will increase. Qualitative analysis has been obtained earlier Topt = 0. 329 125. 99 , and the corresponding Zopt = 30. 007 + j17. 754 . ADS can be used following the Passive CIRcuit / MicorST rip Co nt ro lWindow this tool to automatically generate input port matching circuit.

In the schematic to add a DA_SSMatch1 intelligent modules, and then modify the settings: F = 2. 1 GH z, Zin = 50. It should be noted that the use of the tool to generate matching circuit, Zload is Zopt conjugate. Set up, and then add a MSub the control that primarily used to describe the basic information board, modify the settings for the H = 0. 8 mm, Er = 4. 3, Mur = 1, CONd = 5. 88 10 7 , H u = 1. 0e + 33 mm, T = 0. 03 mil. After setting, can be generated automatically matching circuits, the results of the circuit shown in Figure 4.


Figure 4 input matching circuit

The input matching circuit in Figure 1 and then added to the S-parameter simulation. You can see, the best noise figure Topt position to join because the input matching circuit and successfully matched to 50 position.

2. 2 output matching circuit design

According to the principle of maximum power output gain matching circuits design (taking into account the existence of stable output circuit, the impact on the output impedance, output impedance measurements during stable circuit should be included), will output impedance (Zout = 8. 055 - j8. 980, shown in Figure 5) using the above method matched to 50 . The output matching circuits are shown in Figure 6.


Figure 5, output impedance matching


Figure 6, the output matching circuits

2. 3 simulation results The simulation results observed

can see a gain of 14. 4 dB; noise figure of 0.586, which is the best stable transistor noise figure 0.573 is very close, and the gain flatness is low, stability excellent. Specific performance indicators shown in Figure 7.


Figure 7 schematic simulation data

3 to take into account the noise gain of the main objectives of the program for the design of the simulation

3. 1 input matching circuit design

If you choose to epoxy glass FR4 substrate material for the substrate, dielectric constant 4.3, thickness of 0. 8 mm, then 2. 1 GHz input impedance when the transistor 16. 827 - j16. 041. Generation method using the matching circuit, the input matching circuit A DS design wizard to design single section of the module. Can quickly match the circuit in Figure 8. Shown in Figure 9, the figure m6 = 50 (0. 927 + j0. 001). And very close to 50, so come to the input of the match situation is more reasonable.


Figure 8 input matching circuit


Figure 9 after adding the input matching circuit smit h S 11 of the original

3. 2 output matching circuit design

The completion of the input matching circuit design, you can design the output matching circuits. In this full play the advantages of CAD software, with optimization methods to achieve. The basic process is as follows:

The results of the input matching circuit added to the figure 10, and the transistor output microstrip added as shown. Tune the optimization control, and optimization of the target set to dB (S) 11)) is - 20, dB (S (22)) is - 15.

In optimizing the beginning, the first T L1, T L2, TL3 width is set to 61. 394 mil, which is taken into account in order to protect the plate, plate thickness and other factors under the microstrip line characteristic impedance is 50 . Default T L1, T L2, TL3 length, optimized once, refresh, observation is a better indicator of a variety of charts, setting the maximum value is reached, if the maximum, change the settings again, re-optimization. Repeated several times, will meet again to change these values, if changed little for the role of indicators, you can try to change the input resistance and further optimization of the values ??match.

Found through multiple debugging, R1 is set to 15, and with TL7, the gain and noise figure, and input and output VSWR better. Simulation and optimization of the control circuit diagram shown in Figure 10 and the target control.


circuit schematic in Figure 10 Simulation and optimization control and target control

3. 3 simulation results The simulation results observed

can see a gain of 15. 816 dB; noise figure of 0.708, the index than to be good when the qualitative analysis, and other performance indicators shown in Figure 11.


Figure 11 schematic simulation data

4 Concluding Remarks

Through qualitative analysis of the transistor can be selected according to the actual needs of low-noise preamplifier design, the first best solution at the expense of gain and noise figure obtained; second option is to improve the noise figure the cost and reduce the standing wave ratio VSWRs worth to. 2 methods using computer-aided design tools can be quickly achieved, each with their own existence, which has been applied on many occasions.

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