RF/Microwave Circuits I. Introduction Fall 2003

Transcription

1 Introduction Fall 03

2 Outline Trends for Microwave Designers The Role of Passive Circuits in RF/Microwave Design Examples of Some Passive Circuits Software Laboratory Assignments Grading

3 Trends for Microwave Designers Wireless Communications (major market) T Trend toward integrated (very small) circuits --- transmission line theory and distributed circuits have less direct relevance (RF I is modified to account for this) T At 5 GHz.there s still a lot of board-level design that is not entirely integrated Point-to-point comm, radar and sensing T GHz through 0 GHz distributed circuits are unavoidable Broadband communications (optical telecom) T Requires microwave design at 2.5//40/80 GHz

4 Microwave Receiver - How Important are Passive Ckts? Some systems use multiple antennas for diversity Switch RF Filter Channel 1 Channel 2 LNA Gain Control IF Filter Channels may be multiplexed Mixer LNA Isolator Coupler Crystal Oscillator n Multiplier RF Filter

5 Active Components - How Important are Passive Ckts? 4-Stage MMIC LNA Raytheon : Nominal Gain > 30 db : Noise Figure < db (@ V D = +5 V; I D = 41mA) : Technology: Raytheon 5m phemt The entire chip has only 4 active devices - the rest is passive!

6 Lumped Filters and Parasitics S S21 S43 Ideal Filter Schematic S11 (db) Freq (MHz) Simulated Measured Loss Factor Cut-Off Frequency Freq (MHz) Simulated Measured Inductor Radiation Effects

7 A 2-4 GHz Microstrip Variable Attenuator Varactor Diodes Radial Stub Chip Capacitors Microstrip Coupler

8 Small Discontinuities Can Be a Big Deal Parasitic reactance presented by discontinuities in transmission lines can greatly affect overall system performance (need EM simulation) 0 microns 2 micron gap TEE Junction Air Bridge

9 Good Designers Consider EM Effects 0 59 mil FR4 21 mil FR4 0 mil Alumina - S11 (db) Freq (MHz) Simulated Measured Simulated Measured Simulated Measured S21 (db) Freq (MHz) Simulated Measured Simulated Measured Simulated Measured Surface Mount Capacitor Coupling to Ground Effects

10 PWB Circuits and Modeling nf nh 1.5 pf 1.5 pf LNA (low noise amplifier) Bias Pad S11 Simulation Measured Data 1 6 GHz

11 Microwave Design for Optoelectronics pf Capacitor 680 pf Capacitor Simulation Measured Data GHz Ohm Resistor 1.5 nh Inductors High frequency impedance matching network designed for laser diode 50 Ohm reference impedance; terminated in Ohm resistor (for validation)

12 Software Laboratories Software Laboratories are assignments that involve one or more computer-aided engineering software tools (there s no hardware involved) The topic of the labs will follow material that is discussed during the lecture Specifics about the use of the software will not be discussed in class - you will have written procedures to follow as aids The software will be available in ENB 228, and possibly in other open use labs as well

13 Software Laboratory Topics (Tentative) Circuit optimization and model extraction Numerical electromagnetic simulation Microstrip coupler design Lumped element filter design Distributed element filter design Microwave receiver front-end simulation

14 Grading - Expectations of Neatly Written Assignments All assignments are expected to be well organized and clearly legible else they will be returned with a grade of ZERO. Suggestion: if you simply cannot work well from a neatly organized piece of paper, then REWRITE your solutions before you hand them in. Don t turn in your scratch paper and expect to receive credit.