射频 李缉熙RF培训课件 RF课件 Lecture01_Different RF nd digitl design ology

1、Lecture 1,Richard Li, 2009,1,Lecture 1 : Different Methodology between RF and Digital Circuit Design Richard Chi-Hsi Li 李缉熙 Cellular phone:(PRC) Email : ,1. Differences of Digital and RF Blocks in a Communication System o Impedance o Current drain o Location 2. Controversy o Impedance M

2、atching o Key Parameter o Circuit Testing and Main Test Equipments 3. Answer 4. Notes for High Speed Digital Circuit Design,Lecture 1,Richard Li, 2009,2,1. Differences of RF and Digital Blocks in a Communication System,o Impedance,o Current Drain,o Location,Low impedance for RF but high impedance fo

3、r digital circuitry,The definitions of power and voltage are :,Current for RF circuitry is about 1000 times than that for digital circuitry.,The impact on power and voltage is obvious: For a certain or constant voltage v , In a RF block Z P i In a digtal block Z P i,Lecture 1,Richard Li, 2009,3,* Ca

4、se #1: Low digital data rate,Item RF module /RFICDigital circuit (Low data rate) Impedance Low (50 typically)High (Infinitive ideally) CurrentHigh (mA)Low (A) Location in a communication system * Rx Front end (Before de-modulation)Back end (After de-modulation) * TxBack end (After modulation)Front e

5、nd (Before modulation) Transportation typePower (Watt)Status (Voltage or current) Impedance matching ImportantDont care (usually),Table 1.1 The difference between RF and digital circuit when data rate is low.,where R = Transmitted bits per second, fRF = RF frequency.,Lecture 1,Richard Li, 2009,4,* C

6、ase #2: High digital data rate,and,Table 1.2 Difference between RF and digital circuit design when data rate is high.,Item RF/RFIC Circuit Digital circuit Impedance Low (50 ohm typically) Low to high CurrentHigh (mA) Low to high (A to mA) Location in a communication system * Rx Front end (Before de-

7、modulation)Back end (After de-modulation) * TxBack end (After modulation)Front end (Before modulation) BandwidthNarrow or intermediateWide Transportation typePower (Watt)Status (Voltage or current) Impedance matching Important Dont care (usually)? / Important,where R = Transmitted bits per second, f

8、RF = RF frequency.,Lecture 1,Richard Li, 2009,5,2. Controversy,o Impedance Matching,o Key Parameters,o Testing,Is reflected voltage or power in the circuit really existed ?,Is reflection not existed in IC chip because the size of IC chip very small ?,Voltage ? Current? Power? Impedance ?,Oscilloscop

9、e and Network Analyzer ?,Scale voltage and vector voltage testing ?,The necessity of impedance matching is to reduced the reflected voltage or power.,Lecture 1,Richard Li, 2009,6,3. Answer,Q: Why the transportation type for RF signal is power while the transportation type for digital signal is statu

10、s (voltage or current)? A: Refer to Figure 1, the RF signal is a modulated carrier. It can be effectively modulated, transmitted, transported, and de-modulated, only when it has enough power. The ratio of RF signal to noise power at the input of the de- modulator is required to be more than 10 dB us

11、ually. Therefore, The power transportation or manipulation but not voltage transportation or manipulation is required in the RF block before the demodulator in a receiver and after the modulator in the transmitter. On the contrary, the voltage or current represents the status of digital signal direc

12、tly. The power of digital signal is expected to be reduced down as much as possible. Therefore, The voltage transportation or manipulation but not power transportation or manipulation is required in the digital/analog blocks, after demodulator in a receiver or before the modulator in a transmitter.,

13、Lecture 1,Richard Li, 2009,7,Lecture 1,Richard Li, 2009,8,The different circuit design methodology comes from the different circuit design task.,Conclutions,Lecture 1,Richard Li, 2009,9,Q: Why impedance matching is so important in RF but not in digital circuit design when ? A: Without impedance matc

14、hing, the RF signal would be suffered with * Additional attenuation, * Additional distortion, or additional cross-talk, and eventually * Additional reduction of signal to noise ratio. Without impedance matching, the digital signal would be transported effectively because the impedance of the circuit

15、ry is always high, which is in “quasi- impedance matched” state.,Lecture 1,Richard Li, 2009,10,Lecture 1,Richard Li, 2009,11,1) Without impedance matching, the reflected voltage will appear and interference with the incident voltage. It brings about additional attenuation, additional jitter, an additional cross-talk, and eventually an additional bit error to the digital signal. 2) The traditional layout scheme is no longer reliable to digital circuit with high data rate, 3) The traditional AC grounding