ELEN 701 RF & Microwave Systems Engineering. Lecture 8 November 8, 2006 Dr. Michael Thorburn Santa Clara University

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1 ELEN 701 RF & Microwave Systems Engineering Lecture 8 November 8, 2006 Dr. Michael Thorburn Santa Clara University

2 System Noise Figure Signal S1 Noise N1 GAIN = G Signal G x S1 Noise G x (N1+No) Self Noise No F = = = + gs1 N1 g S N ( N + N ) 1 0 N + N 1 N N 0 1

3 Noise Figure of a Passive Device F = 1+ N N 2 2 N N = g( N0 + = gn F N 1 ) Signal S1 Noise N1 Self Noise No GAIN = G Signal G x S1 Noise G x (N1+No) N N 1 2 = kt0 B = kt B 0 Suppose Passive Device is at ambient temperature and that input noise is also at ambient temperature kt 0 B = gf = 1 g( kt 0 B) F

4 Transmitter System Analysis and Design Adjacent and Alternate Channel Power Low-Pass Equivalent Behavioral Model Approach Multitone Techniques ACPR of Cascaded Stages in Transmitter Chain Noise-Emission Calculation Formula Some Important Notes Output Noise of an Attenuator Output Noise Floor of Device or Transmitter Some Important Considerations in System Design Transmitter Chain Gain Distribution and Performance

5 Transmitter System Analysis and Design Adjacent and Alternate Channel Power Low-Pass Equivalent Behavior Model Approach Adjacent and Alternate Channel Power Adjacent channel power ratio (ACPR) is ratio of power in adjacent channel to the power in the desired channel The alternate channel power ratio is the ratio of power in a specified alternate channel to the power in the desired channel Sketch picture on board Low-Pass Equivalent Behavioral Model Approach The adjacent/alternate channel powers mainly result from spectral regrowth caused by the nonlinearity of the transmitter chain, which mostly comes from the power amplifier and the driver amplifier The ACPR of a digitally modulated transmission signal cannot be accurately determined from intermodulation distortion of discrete tones A nonlinear model, developed from AM-Am and AM-PM measurement or simulation is used

6 Transmitter System Analysis and Design Adjacent and Alternate Channel Power Low-Pass Equivalent Behavior Model Approach Spectral Regrowth The only concern of the spectral regrowth in the transmitter amplifiers is with the nonlinearity that generates distortion products within adjacent and alternate channels If pass-band of the transmitter is a small percentage of the carrier frequency, the nonlinearity can be characterized by odd-order terms of a power series or by a Fourier sine series See Figures 5.6 and 5.7 See Equations through 5.4.6

7 Transmitter System Analysis and Design Adjacent and Alternate Channel Power Multitone Techniques Two-tone measurements are commonly used in determining the intermodulation distortion characteristics In digital mobile communications, signals are more complicated and their spectral regrowth cannot be accurately analyzed in terms of the two-tone IMD It becomes necessary to apply the multitone signals to analytically asses the ACPR of tranmission signals The n-tone ACPR formula is found in equation This does not work for alternate channel power regrowth as it is mainly caused by fifth order nonlinear distortion of the PA

8 Transmitter System Analysis and Design Adjacent and Alternate Channel Power ACPR of Cascaded Stages in Transmitter Chain The ACPR of a transmitter consisting of multiple stages connected in cascade can be derived in terms of and the cascaded OIP3 formula

9 Transmitter System Analysis and Design Noise-Emission Calculation Formula The noise emission from mobile station transmitters is one of the important specifications of the transmitter Especially the noise emission in the receiver band of a full-duplex mobile station. The noise emissions discussed here are those located outside of alternate channels Formulas for Noise-Emission Calculation Begin with estimate of contribution from an individual stage in the transmitter chain The Noise Factor is F The equivalent device noise at the input port is P_Nd=P_No*(F-1) Therefore the noise generated at its output port is P_Ndout = g * kto * (F-1) In addition to this noise, if an input noise is imporsed on the input of the device, the total output power becomes P_Nout = g * P_Nin + g * kto *(F-1)

10 Transmitter System Analysis and Design Noise-Emission Calculation Formula For a transmitter consisting of n stages, the noise emission has a similar formula P_Nout = g_tx * P_Nin + g_tx * kto *(F_tx-1) Where g_tx is overall transmitter gain And where F_tx is the overall noise factor of the transmitter

11 Transmitter System Analysis and Design Noise-Emission Calculation Output Noise of an Attenuator General Expression P N _ out = g P + kt g ( F N _ in 0 1) It may cause some confusion when we calculate output noise of a loss device such as an attenuator While thermal noise kto is imposed at the input of an attenuator the noise at the output of this attenuator is kto

12 Transmitter System Analysis and Design Noise-Emission Calculation Output Noise Floor of Device or Transmitter Minimum Input Noise of a Device is the thermal noise kto

13 Transmitter System Analysis and Design Transmitter Chain Gain Distribution and Performance See spreadsheets

14 Applications of System Design Selection of Frequency Plan Receiver System Design Determination of Carrier-to-Noise Ratio for Receiver Performance Evaluation Noise Figure Linearity and Third-Order Intercept Point Selectivity and Blocking Performance ADC Dynamic Range System Line-Up Analysis and Design Gain Control and RSSI Accuracy Transmitter System Design Transmission Power Adjacent and Alternate Channel Power Noise and Spurious Emission in a Receiver Band Spectrum of Burst Ramp-Up and Down Transients Residual Amplitude Modulation Modulation Accuracy Radio Frequency Tolerance

15 Applications of System Design Selection of Frequency Plan For Superheterodyne architecture this amounts to: Understanding the Frequency Band Allocation (Regulation) Selection of the receive IF frequency Resulting determination of the transmit IF Resulting determination of the LO Need to do a spur analysis Understand mixer spurs Understand harmonics of power amplifiers Understand IMs of power amplifiers in multicarrier applications Need to define filter requirements for spurs

16 Applications of System Design Receiver System Design Determination of Carrier-to-Noise Ratio for Receiver Performance Evaluation and Noise Figure Determine required receiver sensitivity Determine required receiver NF Assemble line-up of elements within the receiver and determine the cascaded NF and the corresponding various component gain and NFs DESIGN is an iterative process Select Components from catalog of available parts Develop components as required Ensure sensitivity requirements are satisfied Keep in mind degradations in receiver sensitivity due to output power spectrum in receive band

17 Applications of System Design Receiver System Design Linearity and Third-Order Intercept Point Compute cascaded IIP3 (or OIP3) for line up on receiver units. Consider filtering of intermodulation products when evaluating gain of intermodulation products and corresponding IIP3 levels Determine if intermodulation power: Poses threat as interference Results in distortion

18 Applications of System Design Receiver System Design Selectivity and Blocking Performance Selectivity Design channel filters so that desired signal passes undistorted and adjacent/alternate channels are rejected Parameters include: Insertion Loss Passband flatness Passband gain slope Passband group delay and group delay slope Out of band rejection Spuriuos rejection

19 Applications of System Design Receiver System Design ADC Dynamic Range Develop line up of units in receiver Determine input power range Determine signal level through transceiver Target acceptable range of levels of input for ADC to work properly Determine to what degree ALC is required ALC=automatic level control. e.g. VGA with feedback control

20 VGA in Superheterodyne Full-Duplex Receiver

21 Applications of System Design Receiver System Design System Line-Up Analysis and Design Clearly the system line-up is a key component of the system design Allow for drop in of available units Track: Signal strength Noise Power Cascaded Noise Figure Cascaded IIP Note: Spurious frequencies LO power level Channel selectivity (filter) requirements Input signal power Threshold BER

22 Applications of System Design Receiver System Design Gain Control and RSSI Accuracy Selection of Frequency Plan Receiver System Design Determination of Carrier-to-Noise Ratio for Receiver Performance Evaluation Noise Figure Linearity and Third-Order Intercept Point Selectivity and Blocking Performance ADC Dynamic Range System Line-Up Analysis and Design Gain Control and RSSI Accuracy Transmitter System Design Transmission Power Adjacent and Alternate Channel Power Noise and Spurious Emission in a Receiver Band Spectrum of Burst Ramp-Up and Down Transients Residual Amplitude Modulation Modulation Accuracy Radio Frequency Tolerance

23 Applications of System Design Transmitter System Design Transmission Power Transmission Power of Transceiver is combined with Antenna Gain to give EIRP Key parameter in link Establishes (largely) the DC power requirements of transceiver Establishes thermal design (if applicable) Cost driver Cornerstone of transmitter design

24 Applications of System Design Transmitter System Design Adjacent and Alternate Channel Power Significant concern of transmitter is spectral regrowth and resulting undesired power in adjacent or alternate channels Interference to other users of system Drives linearity concerns in transmitter design Cascaded IIP is typical quantity tracked AM/AM and AM/PM characteristics provide details as to regrowth Post amplifier filters may be used to limit out of band power At expense of insertion loss and wasted DC power At expense of thermal design for high power transmitters

25 Applications of System Design Transmitter System Design Noise and Spurious Emission in a Receiver Band Significant signal level differences between receive and transmit signals e.g. ~-100 dbm vs. 30 dbm Design must ensure adequate rejection of noise and spurious signals in receive band Degrades receiver sensitivity May damage RF front end (due to overdrive)

26 Applications of System Design Transmitter System Design Spectrum of Burst Ramp-Up and Down Transients Selection of Frequency Plan Receiver System Design Determination of Carrier-to-Noise Ratio for Receiver Performance Evaluation Noise Figure Linearity and Third-Order Intercept Point Selectivity and Blocking Performance ADC Dynamic Range System Line-Up Analysis and Design Gain Control and RSSI Accuracy Transmitter System Design Transmission Power Adjacent and Alternate Channel Power Noise and Spurious Emission in a Receiver Band Spectrum of Burst Ramp-Up and Down Transients Residual Amplitude Modulation Modulation Accuracy Radio Frequency Tolerance

27 Applications of System Design Transmitter System Design Residual Amplitude Modulation Selection of Frequency Plan Receiver System Design Determination of Carrier-to-Noise Ratio for Receiver Performance Evaluation Noise Figure Linearity and Third-Order Intercept Point Selectivity and Blocking Performance ADC Dynamic Range System Line-Up Analysis and Design Gain Control and RSSI Accuracy Transmitter System Design Transmission Power Adjacent and Alternate Channel Power Noise and Spurious Emission in a Receiver Band Spectrum of Burst Ramp-Up and Down Transients Residual Amplitude Modulation Modulation Accuracy Radio Frequency Tolerance

28 Applications of System Design Transmitter System Design Modulation Accuracy Selection of Frequency Plan Receiver System Design Determination of Carrier-to-Noise Ratio for Receiver Performance Evaluation Noise Figure Linearity and Third-Order Intercept Point Selectivity and Blocking Performance ADC Dynamic Range System Line-Up Analysis and Design Gain Control and RSSI Accuracy Transmitter System Design Transmission Power Adjacent and Alternate Channel Power Noise and Spurious Emission in a Receiver Band Spectrum of Burst Ramp-Up and Down Transients Residual Amplitude Modulation Modulation Accuracy Radio Frequency Tolerance

29 Applications of System Design Transmitter System Design Radio Frequency Tolerance Selection of Frequency Plan Receiver System Design Determination of Carrier-to-Noise Ratio for Receiver Performance Evaluation Noise Figure Linearity and Third-Order Intercept Point Selectivity and Blocking Performance ADC Dynamic Range System Line-Up Analysis and Design Gain Control and RSSI Accuracy Transmitter System Design Transmission Power Adjacent and Alternate Channel Power Noise and Spurious Emission in a Receiver Band Spectrum of Burst Ramp-Up and Down Transients Residual Amplitude Modulation Modulation Accuracy Radio Frequency Tolerance

30 Homework Review material Refine spreadsheets A design problem will be prepared and distributed next week which we will work on for remainder of class.

ELEN 701 RF & Microwave Systems Engineering. Lecture 4 October 11, 2006 Dr. Michael Thorburn Santa Clara University

ELEN 701 RF & Microwave Systems Engineering. Lecture 4 October 11, 2006 Dr. Michael Thorburn Santa Clara University ELEN 7 RF & Microwave Systems Engineering Lecture 4 October, 26 Dr. Michael Thorburn Santa Clara University Lecture 5 Receiver System Analysis and Design, Part II Key Parameters Intermodulation Characteristics