1. 1/27 2010.08.13 지능형 마이크로웨이브 시스템 연구실 박 종 훈

2. 2/27 Contents Ch.5 Transceiver Architecture 5.1 General Considerations 5.2 Receiver Architectures 5.3 Transmitter Architectures 5.3.1 Direct-Conversion Transmitters 5.3.2 Two-Step Transmitters 5.4 Transceiver Performance Tests 5.5 Case Studies 5.5.1 Motorola’s FM Receiver 5.5.2 Philips’ Pager Receiver 5.5.3 Philips’ DECT Transceiver 5.5.4 Lucent Technologies’ GSM Transceiver 5.5.5 Philips’ GSM Transceiver

3. 3/27 5.3 Transmitter Architectures Transmitter Performances Modulation, Upconversion, Power amplification Modulation + Upconversion Transmitter VS Receiver Transmitter : Only a few forms Receiver : Variety of approaches invented Relaxed in transmitters than in receivers Noise, interference rejection, band selectivity

4. 4/27 5.3 Transmitter Architectures 1. Baseband / RF interface 1) FM System Baseband signal is conditioned By filter and/or a variable-gain stage, compensating for manufacturing variations in the VCO characteristic Because Output spectrum Oscillator must be stabilized by feedback loop Frequency synthesizer Baseband signal modulated by VCO

5. 5/27 5.3 Transmitter Architectures 2) Digital phase modulation system Data pulses must be shaped To minimize intersymbol interference and/or limit the signal bandwidth

6. 6/27 5.3 Transmitter Architectures Bandpass pulse shaping

7. 7/27 5.3 Transmitter Architectures GMSK h(t) : Impulse response of a Gaussian filter -> Impacts the channel bandwidth -> Prove more accurate filter

8. 8/27 5.3 Transmitter Architectures Phase and gain mismatch Ideal case Mismatch case

9. 9/27 5.3 Transmitter Architectures 2. PA/Antenna Interface Transmitter output must pass through a duplexer filter or a TDD switch Duplexer filters : 2 to 3dB -> Dissipating 30 to 50% of PA output power in the form of heat Example PA provides 1W of power -> 300mW is wasted in the filter PA efficiency rarely exceeds 50% 600mW drained from the supply to filter TDD switch : 0.5 and 1dB loss -> higher overall efficiency

10. 10/27 5.3.1 Direct-Conversion Transmitters 1. Direct conversion Transmitted carrier frequency = Local oscillator frequency Modulation and upconversion occur in the same circuit Matching Network Provide maximum power transfer to the antenna and filter out- of-band components Noise of the mixers is much less critical Signal is sufficiently strong

11. 11/27 5.3.1 Direct-Conversion Transmitters Drawback Disturbance of the transmit local oscillator by the power amplifier PA output is a modulated waveform with high power and a spectrum centered around the LO frequency Injection pulling or injection locking Worsens if the PA is turned on and off ( to save power)

12. 12/27 5.3.1 Direct-Conversion Transmitters Solution Offsetting the LO frequency Adding or subtracting the output frequency of another oscillator

13. 13/27 5.3.2 Two-Step Transmitters Circumventing the problem of LO pulling Baseband modulate W 1 ( Intermediate Frequency)

14. 14/27 5.3.2 Two-Step Transmitters Advantage Quadrature modulation is performed at lower frequencies I and Q matching is superior Less cross-talk Limit the transmitted noise and spurs in adjacent channels Difficulty Second upconversion must reject the unwanted sideband by a large factor (50 to 60dB) Wanted and unwanted sidebands with equal magnitudes Because of higher center frequency, filter is typically a passive, relatively expensive off-chip device

15. 15/27 5.4 Transceiver Performance tests 1. Sensitivity and Dynamic Range In most systems, a minimum detectable signal level is specified In-band intermodulation test Output carrier-to(noise+intermodulation) [C/N+I)] must not far below 9dB

16. 16/27 5.4 Transceiver Performance tests Out-of-band and second-order intermodulation test C/(N+I) of the IF signal must exceed 9dB Out-of-band cross modulation C/(N+I) of greater than 9dB

17. 17/27 5.4 Transceiver Performance tests 2. Unwanted Emission Modulation Mask Below which the transmitter output spectrum must lie Standard to ensure negligible radiation in adjacent channels ACP IS-54 standards : -26dBc IS-95 standards : -42dBc Mask

18. 18/27 5.5 Case Studies 5.5.1 Motorola’s FM Receiver 5.5.2 Philips’ Pager Receiver 5.5.3 Philips’ DECT Transceiver 5.5.4 Lucent Technologies’ GSM Transceiver 5.5.5 Philips’ GSM Transceiver

19. 19/27 5.5.1 Motorola’s FM Receiver Walkie-talkies or first-generation cordless phone (50MHz) No LNA and Image rejection filter Required some external components Remove some image 50Mhz±10.7MHz Reject interferers Reasonable noise figure and linearity Channel Selection Amplified nonlinearly

20. 20/27 5.5.2 Philips’ Pager Receiver UAA2080T is a single-chip bipolar homodyne receiver (FSK) Required some external components Local Oscillator 470MHz (frequency doubler : 235MHz X 2) Actually operates at the third harmonic of a 78.3MHz crstal Received single fixed freq. -> freq. need not be variable -> eliminating synthersizers compact, low-power But cannot easily generate precise quadrature phases -> Seperation in the RF path Matching, Single-ended to differential Spilit RF signal ( LO simplicity) Channel Selection

21. 21/27 5.5.2 Philips’ Pager Receiver Bypolar Technology Minimize the I/Q imbalance Even-order distortion is suppressed (Differential circuits) LO leakage is reduced by cascode configuration (LNA, mixers) Limited dynamic range is less serious FSK : High frequency -> High SNR Bit error rate can be as high as 3% Because redundancies are incorporated in the data stream to correct errors

22. 22/27 5.5.3 Philips’ DECT Transceiver 2nd IF is much higher than MC3362 because the DECT channel bandwidth of 1.7MHz requires a sufficiently high center frequency 1.89GHz TDD Matching, Converted to Differential Mismatch- limited SAW filter 110MHz 9.8MHz

23. 23/27 5.5.3 Philips’ DECT Transceiver Blind slot Receive and transmit modes are separated by blind slot Stabilize the frequency Approximately 250μs to settle, a blind slot precedes the signal transmission to avoid leakage of the spectrum into adjacent channels

24. 24/27 5.5.3 Philips’ DECT Transceiver Error Problem Separation from the feedback loop, the VCO control line experiences finite charge injection errors PA is turned on, its input impedance varies thereby changin the load impedance and hence the oscillation frequency of the VCO PA active current, about 250mA, drops the battery voltage by a few hundred millivolts, affecting the VCO output frequency The sum of these errors must not exceed 50kHz

25. 25/27 5.5.4 Lucent Technologies’ GSM Transceiver Lucent Microelectronics(formerly AT&T Microelectronics) offers a single-chip solution that, along with a low-noise amplifier and a power amplifier Requires only two external filters But the IF SAW device tends to have higher loss(and higher cost) if it must filter adjacent channels to sufficiently low levels 900Mhz Channel Selection To avoid VCO pulling

26. 26/27 5.5.5 Philips’ GSM Transceiver Philips’ semiconductor offers a pair of RF and IF chips for GSM transceivers 900Mhz Allow the use of two low-cost, lossy image-reject filter 1.3GHz Signal : 700Mhz Image : 1.7GHz Integrated fifth-order low-pass filters -> IF SAW filters has relaxed 1.3GHz Oscillator, Suppressing the unwanted sideband -> LC Filter has relaxed

27. 27/27 5.5.3 Philips’ DECT Transceiver Only two oscillators Simplifying the prediction of various spurs Because the system is time division(and frequency division) duplexed, making it possible to share the oscillators between the two paths