Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy John Musson (and Colleagues!) TJNAF Ultra-Linear Receivers for Digital LLRF Control Systems

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 2 Receiver Parameters Intrinsic Noise Figure Low-end limit Ultimate sensitivity Saturation Large-signal limitations, distortion Linearity Everything in- between! External Phase Noise ADC Sampler Jitter Interference ”blocking” Reciprocal mixing Additionally, AM demod is inherently linear PM is NOT! Threshold effect

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 3 Taxonomy IIP3 = Input 3 rd Order Intercept Point P1dB = 1 dB Compression Point K = Boltzmann's Constant To = 290 degrees Kelvin NF = Noise Factor (linear) F = Noise Figure (in dB) SFDR = Spurious-Free Dynamic Range BW = Receiver Bandwidth MDS = Minimum Discernible Signal SNR = Signal to Noise Ratio

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 4 All Math Aside....or a Toolbox Smorgasbord To = 290 K (IEEE) KTo = -174 dBm NF = Tsys / F = 10 log NF IIP3 = Pim = 3Ptone – 2PIIP3 NFnet = SFDR3 = 2/3 (IIP – F -10log BW) SFDR2 = ½ (IIP – F -10 log BW) P phase noise = P unwanted + 10log BW + P rx phase noise

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 5 Courtesy “RF and Microwave Designer's Handbook, Watkins-Johnson Company, 1997 “Introduction to Radio Frequency Design,” Wes Hayward, ARRL 1994

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page MHz Warm Cavity Requirements

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 7 Receiver Bandwidth Software Defined Radios (SDRs) can have 2 associated bandwidths: Analog Minimum element in Front End Factors include latency, anti-alias, IF / Digital Generally the narrowest, set by IIR / FIR DR Calculations should use the analog BW SNR should use narrow/digital BW In addition, Closed-Loop control BW for LLRF BW determined largely by sensitivity (KTB) and latency (“Group Delay”) requirements Ex. JLAB LLRF Rx uses a 8 MHz BPF exhibiting 100 ns of latency

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 8 Components High IIP3 FET Mixer WJ HMJ5 IIP3 = 35 dBm Try to shield active (vulnerable) amplifier, but not deep enough to destroy noise figure! High IIP2 / IIP3 Amplifier WJ AHJ-2 IIP3 = +26 dBm F = + 4dB dBm LO AHJ2HMJ5 BPF Thermopad

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 9 Don't Forget the ADC!! Effective Dynamic Range = b + 10log fs b = # of bits, fs = sample frequency 1 Hz BW DR > Analog, and LSB >> MDS Noise Figure can be assigned Function of sample rate and # of bits F = 12 dB (AD 6645 w/ fs = 56 MHz, Rs = 200 Ohms) S/N degradation from sample clock jitter: Reference: Frerking, M., “Digital Signal Processing in Communication Systems” Sets ultimate PM S/N Sets ultimate PM limit

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 10 Courtesy “Digital Signal Processing in Communication Systems,” Frerking, M., Chapman and Hall,1994 “Digital Communications,” Proakis, J., McGraw-Hill, 1994

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 11 Modeling

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 12 Modeling (Dynamic)

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 13 Grouping Relevant Terms..... Pmin ~ KT o B + F net + S/N jitter + P phase noise + S/N imposed - ??? (ie Processing Gain from DSP decimation??) JLAB LLRF (Gradient) IF = 70 MHz, fs = 56 MHz, B = (control BW) (<90 dBc for  < 200 ps) + ? = -39 dBm!! So, our receiver is within spec at Pin > -39 dBm.

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 14 What About High-End? FET mixer (IIP3 = +35 dBm) combined with CATV amplifier (IIP3 = +27 dBm), predicts an IIP3 of + 43 dBm (+41 dBm measured) Maintaining an IM supression of 80 dB implies: Pmax = 2* 43 – 80 = + 3 dBm. So, based on the additional requirement of 20 dB of specification compliance, we achieve +3 - (-39) = 42 dB of dynamic range (100 : 1) with 80 dB of supression on either side. Arguably, high-end range can also be extended by noting that IM corruption is correlated….Would most likely lead to a “DC” phase offset” Presumption of some processing gain bails us out!!!

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 15 Verification Measurements Noise Figure —Y-Factor Effective for F < 25 dB Affordable; easily built into receiver front ends —Spectrum Analyzer + LNA Nice paper presented by T. Powers at BIW '98 –“Improvement of the Noise Figure of the CEBAF Switched Electrode Electronics BPM System” MDS / Tangential Sensitivity —Easy to do; outcome-based! —Can also be built-in Dynamic Range —1 dB Compression —IIP3 Phase Noise

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 16 “Fundamentals of RF and Microwave Noise Figure Measurements,” HP Tech Note 57-1 “Noise Figure Measurement Accuracy- The Y- Factor Method,” HP Tech Note 57-2 “Radio Astronomy,” J. Kraus, Cygnus-Quasar, 1988

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 17 Two-Tone IMD Test for IIP3 Courtesy “Improve Two Tone, Third Order Testing,” Mini Circuits Tech Note

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 18 Courtesy “Introduction to Radio Frequency Design,” W. Hayward, ARRL, 1994

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 19 Phase Noise Or

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 20 Summary Life for the Analog RF Engineer is STILL interesting! Back-to-basics design and testing —Made much easier with modern ($$) test equipment —Models are quite reliable for first-cuts Narrowband techniques can improve most parameters (ala Genesys) If LLRF becomes more demanding…….(?) 73, DE WD8MQN