Title: Design and Implementation of Low Power, Highly Integrated Receivers for Indoor Wireless Systems
1Design and Implementation of Low Power, Highly
Integrated Receivers for Indoor Wireless Systems
- Dennis Yee
- Robert Brodersen
- University of California, Berkeley
2Receivers General Considerations
- Main goal downconvert signal from fRF to
baseband - Hostile wireless environment
- weak desired signal
- strong neighboring interferers
- Circuit nonidealities
- limited filter attenuation, thermal noise,
nonlinearities, LO phase noise, etc.
3Heterodyne Architecture
- Most commonly used architecture in practice
- How is fIF chosen?
4The Image Problem
- Image signal can be much stronger than the
desired signal and must be attenuated before
downconversion
- Trade-offs
- high IF relaxes RF filtering requirements
- low IF relaxes IF amplification and filtering
requirements
5Image Reject (Weaver) Architecture
- 30 - 45dB image rejection
- Image rejection limited by gain and phase
mismatch - Examples
- DECT Gray
- DCS1800 Steyaert
- GPS Lee
6Direct Conversion Architecture
- Eliminates IF stage(s)
- if equivalent baseband signal is real, no image
problem
- Design issues
- DC offsets (LO self-mixing, circuit mismatch,
even-order distortion) and flicker noise
7Direct Conversion Practical Considerations
Even-Order Distortion
LO Self-Mixing
Baseband Circuit Offset
Flicker Noise
- Possible solutions AC coupling, offset
compensation
8Prototype A Zero-IF Receiver for W-CDMA
- Zero-IF architecture for high integration and
efficient power consumption
9Framework for System/Hardware Co-Design
- Performance metric comparison
- Simulation to examine system/hardware interactions
10Matlab Simulink Model of Zero-IF Receiver
- Techniques used to decrease simulation time
- Baseband equivalent modeling of RF signals
(envelope simulation techniques) - Compile design using Matlab Real-Time Workshop
11Simulation Speed Issues
- RF signals occupy a narrow bandwidth relative to
carrier - Example 25MHz W-CDMA signal centered at 2GHz
- Simulation sampling rate determined by Nyquist
Sampling Theorem - fs gt 2fRF
- Simulation of RF signals can be really, really
slow
12Baseband-Equivalent Model
- Represent any real signal as
- Example an ideal RF signal centered at wc with
baseband I and Q components, sI1(t) and sQ1(t)
- Eliminate dependence on wc by keeping track of
time-varying coefficients sDC(t), sIn(t), and
sQn(t) - Sample time based on symbol period
- Complexity depends on number of harmonics
13Simulation of Flicker Noise
- Pass white noise through a filter with frequency
response 1/f 1/2 - Approximate transfer function by
14System Simulation of Zero-IF Receiver
- 10 users (equal power)
- 13.5dB receiver NF
- PLL -80dBc/Hz _at_ 100kHz
- 2.5 I/Q phase mismatch
- 82dB gain
- 4 gain mismatch
- IIP2 -11dBm
- IIP3 -18dBm
- 500kHz DC notch filter
- 20MHz Butterworth LPF
- 10-bit, 200MHz S-D ADC
Output SNR 15dB
15Receiver Prototype
- 0.25mm CMOS ST process
- Fully differential architecture
- LNA inductors used for 50W matching
- Mixer Gilbert quad
- PLL ring oscillator VCO
- ADC S-D 2-1-1 multi-bit cascade
- 5mm x 5mm
S-D ADC
SK Filter/ Notch
PLL
Mixer
LNA
16Simulated Performance
- Simulation of entire receiver using SpectreRF
transmit spectrum
receive spectrum
17Analog Design Flow
behavioral
- Simulink
- system specifications
- rapid end-to-end simulation
structural/physical
- SpectreRF
- component performance
- periodic steady-state, envelope analyses
- HP ADS
- microwave design
- ASITIC
- integrated passive components
18Session Talks
- Single-Chip Custom Transceiver Project
- Brian Limketkai
- Chinh Doan
- David Sobel
- Johan Vanderhaegen
- Single-Chip Multi-Standard Transceiver Project
- Martin Tsai