Introduction to RFIC receiver architecture

1. Introduction to RFIC receiver architecture Special Topics in Computers and Circuits 30(Wed), March, 2011 2007144078 Min, Kyungsik

2. Context • Terminology • Local Oscillator (LO) • Low Noise Amplifier (LNA) • Intermediate Frequency (IF) • Receiver Architecture • Heterodyne • SuperHeterodyne • Direct-Conversion (Zero-IF) • Low-IF • Quasi-IF

3. Terminology Receiver Architecture

4. Local Oscillator(LO) • converting a signal of interest to a different frequency using a mixer (by wikipedia) • Heterodyning : process of conversion • produces the sum and difference frequencies of the frequency of the local oscillator and frequency of the input signal of interest.

5. LNA • first amplifier in the receiver, right after the antenna and the duplex filter • To boost the received signal out from the noise and reduce the noise interference • The gain of the LNA helps to suppress the noise of the subsequent blocks in the receiver. • Frii’s Equation ++…

6. Intermediate Frequency(IF) Definition • a frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception • Created by mixing the carrier signal with a local oscillator signal • Used in superheterodying radio receivers Merits • can be used in many devices • To convert the various different frequencies of the stations • Improve frequency selectivity

7. Intermediate Frequency(IF) • Television receivers: 30 MHz to 900 MHz • Analogue television receivers using system M: 41.25 MHz (audio) and 45.75 MHz (video). Note, the channel is flipped over in the conversion process in an intercarrier system, so the audio IF frequency is lower than the video IF frequency. • Analogue television receivers using system B and similar systems: 33.4 MHz. for aural and 38.9 MHz. for visual signal. • FM radio receivers: 262 kHz, 455 kHz, 1.6 MHz, 5.5 MHz, 10.7 MHz, 10.8 MHz, 11.2 MHz, 11.7 MHz, 11.8 MHz, 21.4 MHz, 75 MHz and 98 MHz. • AM radio receivers: 450 kHz, 455 kHz, 460 kHz, 465 kHz, 470 kHz, 475 kHz, 480 kHz • Satellite uplink-downlink equipment: 70 MHz, 950-1450 Downlink first IF • Terrestrial microwave equipment: 250 MHz, 70 MHz or 75 MHz • Radar: 30 MHz • RF Test Equipment: 310.7 MHz, 160 MHz, 21.4 MHz

8. Terminology Receiver Architecture

9. Heterodyne receiver • Traditional heterodyne receiver architecture based on the parallel data detector concept • the original radio receiver design • introduced in 1901 by Reginald Fessenden (Canadian inventor-engineer)

10. Heterodynereceiver • exploits high quality filters to provide desired performance 1st filter : duplex filter 2nd filter : image rejection filter 3rd filter : channel selection filter

11. Heterodyne receiver Problem #1 : It is very difficult to tune an amplifier and/or filter! • We can change the frequency response of an amplifier/filter by changing the values of the reactive components(i.e., inductors and capacitors). • But the center frequency and bandwidth of an amplifier/filter are related to the inductor and capacitor values in very indirect and complex ways. • Additionally, a filter of high selectivity(i.e., “fast roll-off”) will be a filter of high order -> high order means many inductors and capacitors! Result : Tuning a good heterodyne receiver can be very difficult, requiring a precise adjustment of many control knobs!

12. Heterodyne receiver Problem #2 : The signal reaching the detector can be any one of many frequencies(e.g., w1, w2, w3, w4) distributed across a very wide bandwidth. As a result, the detector must be wideband! Unfortunately, a good wideband detector/ demodulator is difficult to build. Generally speaking, a detector/demodulator will work well at some frequencies, but less well at others.

13. Superheterodyne receiver • superheterodyne : creating a beat frequency that is lower than the original signal • to purposely mix in another frequency in the receiver, so as to reduce the signal frequency prior to processing Incoming signal, centered at the carrier frequency Intermediate frequency signal, at constant frequency, IF

14. Superheterodyne receiver • Advantages of using Superheterodying (receiver) • Reduces the signal from very high frequency sources where ordinary components wouldn’t work(like in a radar receiver) • Devices can be optimized or made more inexpensively • Can be used to improve signal isolation by arithmetic selectivity • Difficulty • Hard to treat high quality of digital signal • Duplication of original signal and image signal

15. Direct-conversion Direct-conversion receiver architecture

16. Direct conversion

17. Direct conversion • Amplification and filtering : performed at baseband • Low current drain in amplifiers and active filters • No task of image-rejection • Wide tuning and high selectivity • Two high frequency conversion stages in parallel • LO frequency deviation • Spurious LO leakage • DC offset connected to direct-conversion

18. Low-IF Low-IF receiver architecture

19. Low-IF

20. Low-IF • Analog implementation : hard to provided superior performance and a degree of flexibility → downconversion of information signal to a low-IF frequency • no duplication of desired signal with image frequency • power consumption • Use of I/Q-demodulation • I/Q demodulation providing for 20-40 dB’s of image rejection → a less selective filter

21. Quasi-IF Quasi-IF receiver architecture

22. Quasi-IF • Combining a non-tunable I/Q down-conversion mixer and a tunable image rejection mixer for down-conversion to baseband and channel selection Advantages • first LO : optimized with respect to phase noise as no switching requirements are now present • Tunable second LO : operates at low frequencies whereby phase noise and undesired non-linearities may be minimized • absence of IF filter Disadvantages • DC offset

23. Comparison Comparison of various receiver architecture key parameters

24. Comparison

25. Thank you.