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OPERATING CONSIDERATIONS

BPM aliasing of AM and FM modulations

Aliasing by the BPM can indicate nonexistent beam motions.  Both FM and AM modulations of the 
RF signal can cause aliasing.   No matter which button sampling frequency is chosen, aliasing will 
appear at a certain modulation frequency.  

Aliasing occurs because the beam sampling frequency is lower that the other frequencies involved.
Some of the frequencies come from the beam:
• all harmonics of the revolution frequency, thus,
• the RF frequency extending to the full frequency spectrum of the bunches,
• the betatron and synchrotron frequencies.

More frequencies are produced by the BPM module itself: 
• the local oscillator frequency and its harmonics, 
• the original frequency of the quartz,
• the prescaling dividers of the frequency synthesizer.

These frequencies are voluntarily mixed together in the superheterodyne mixer and produce every 
possible sum and difference. Most of them will be eliminated by filters, but some of them are so 
close to the intermediate frequency that they cannot be eliminated.

Finally the BPM sampling process –at the frequency of the clock– will produce signal aliasing. 
Any of these frequencies in the range 0 to 1 kHz will appear as a  spectral line in the BPM outputs 
(X, Y, A, B, C and D).

Identifying and eliminating aliasing

The BPM output (X, Y or both) must be observed with a low frequency spectrum analyser or FFT 
analyser in the 0 to 2-3 kHz bandwidth.

First, check the BPM with an RF generator.  Apply the RF generator signal to the BPM module via 
a 4-way splitter (see page 4, this manual).  The BPM noise spectrum should look as printed on the 
Noise vs. frequency hardcopy shipped with the calibration certificate.

Then, connect the BPM to the beam position pick-ups.  If spectral lines (noise peaks) appear in the 
spectrum, several actions can be attempted to eliminate them.

Note:  It is possible that one BPM module exhibits those spectral lines, while other BPM modules do not.  This is 
because the local oscillator frequency and the clock frequency is not eactly the same for all BPM modules.

a) The sampling clock frequency can be changed.
b) The local oscillator frequency can be changed by a few thousand Hertz
c) The local oscillator frequency can be changed in large steps by changing 
    the synthesizer’s F-key, yet this will generally not be necessary.

(see "F-key" page 7, this manual, for its location, page 20 for its programming)

I recommend to start with the sampling clock.  The on-board clock generator frequency can be 
adjusted over a small range (ca. ±20%) with the “Clock adjust” potentiometer (see “Button 
Sampling”, page 7, this manual).  For a wider range, the on-board clock can be overridden by an 
external clock signal (see “External Clock”, page 8, this manual).

BERGOZ Instrumentation

Multiplexed

01630 Saint Genis Pouilly, France

Beam Position Monitor

Tel. +33-450.426.642
Fax +33-450.426.643

Page 26

User’s manual

                                                                                                                                                                    

                                                                                                                                                                         

BERGOZ Instrumentation  -  01630 Saint Genis Pouilly, France - Tel.: +33-450.426.642  -  Fax: +33-450.426.643

email: [email protected] - http://www.bergoz.com - Registre des Métiers: Bourg-en-Bresse - Registre des ingénieurs: Zurich

TVA-VAT-IVA-USt. Nº FR88414997130  -  Sàrl. capital 152K  -  Siren 414 997 130  R.C.S. Bourg  - APE 332B

Содержание MX-BPM

Страница 1: ... Tel 03 3918 5326 Tel 650 802 8292 Fax 03 3918 5712 Fax 650 802 8298 sales repic co jp sales gmw com BERGOZ Instrumentation 01630 Saint Genis Pouilly France Tel 33 450 426 642 Fax 33 450 426 643 email bergoz bergoz com http www bergoz com Registre des Métiers Bourg en Bresse Registre des ingénieurs Zurich TVA VAT IVA USt Nº FR88414997130 Sàrl capital 152K Siren 414 997 130 R C S Bourg APE 332B Mul...

Страница 2: ......

Страница 3: ...N 28 ACCESSORIES 29 Table top test kit 29 Card extender 30 Service modules TTL commands RF 30 Chassis 31 SPECIFICATIONS 32 BPM MODULE REAR CONNECTOR 33 SCHEMATICS BOARD LAYOUT 34 ACKNOWLEDGEMENT 34 Annex I RF Connectors from Siemens Annex II Precision Analog Signal Processing for Beam Position Measurements in Electron Storage Rings J A Hinkson and K B Unser Proceedings of the 2nd DIPAC Travemünde ...

Страница 4: ...mended to send a detailed description of the problem by fax SERVICE PROCEDURE Products requiring maintenance should be returned to Bergoz Instrumentation or its local distributor Bergoz Instrumentation will repair or replace any product under warranty at no charge The purchaser is only responsible for transportation charges For products in need of repair after the warranty period the customer must...

Страница 5: ...nd use a transformer or contact the manufacturer to get another power supply In the 19 chassis The power supply is autoranging 98V 264V and does not need any adjustment QUICK CHECK You can check immediately that your BPM system is working If you have the table top test kit BPM KIT use the following set up Oscilloscope Ch 1 Ext trig SDEMOD SYNC Beam Position Monitor RF Source AC mains A B C D Power...

Страница 6: ...adable Connect to AC mains the oscilloscope should display Synchronous demodulated signal Each period 100 125µs represents the successive buttons A B C D A B The signals are equalized before delivery of the BPM module using a precision input 4 way splitter Differences in signal level as shown here are due to uneven input signals Note 1 dB input signal difference gives ca 300 mV of demodulated sign...

Страница 7: ...other one Getting familiar with the BPM Vary the power from the RF source to simulate beam intensity variations Explore the range from 0 dBm down to 90 dBm Remember that the 4 way power splitter absorbs some power adjust for it While the RF source output power is changed observe the intensity dependence of X and Y outputs on the voltmeters If the BPM electronics gain has been set for 1 V mm each m...

Страница 8: ... attenuators Extract the BPM module and proceed as described in Quick Check Note BPM modules can be removed and inserted while the power is on The card extender BPM XTD allows a BPM module to be extended out of its chassis slot Extract the BPM module install the extender and proceed as in Quick Check Note The card extender has unequal button to button attenuations It introduces an offset in X and ...

Страница 9: ...by simply adjusting X 0 and Y 0 There is an infinite number of A B C D combinations satisfying X 0 and Y 0 i e A 1 B 2 C 1 D 2 yields X A B C D 0 and Y A B C D 0 BUTTON SAMPLING The BPM module has an on board clock to drive the input multiplexer The internal clock frequency is adjustable by the Clock adjust potentiometer from 8 to 10 kHz Each button is thus sampled during 100 to 125 µs and a compl...

Страница 10: ...ions The performance of the BPM module is not affected by a higher sampling frequency The X Y output noise increase is not noticeable The X Y zero on center dc values are slightly shifted but stable at each particular frequency ALGORITHM POLARITY CONVENTION 45 buttons VA VB VC VD VA VB VC VD Ky X VA VB VC VD VA VB VC VD Kx Y Y X A B C D Orthogonal buttons B C D A X Y Ky Y VA VB VC VD VB VD X VA VC...

Страница 11: ... of our BPM module were developed by John W Bittner and Richard W Biscardi for the National Synchrotron Light Source at Brookhaven National Laboratory U S Patent 5 001 416 was granted to them on March 19 1991 BLOCK DIAGRAM frequency synthesizer filter BPF LNA sample hold S H S H S H S H attenuators LO oscillator phase detector mixer 21 4 MHz filter BPF amplifier IF filter BPF VCO LPF limiter phase...

Страница 12: ...t signal noise resolution vs input signal strength 90 dBm 80 dBm 70 dBm 60 dBm 50 dBm 100 mVrms Hz 10 mVrms Hz 1 mVrms Hz 100 µVrms Hz 10 µVrms Hz Signal power applied to BPM inputs Noise in 10V Y output at 1 V mm sensitivity for 17 12 mm chamber in Y Unit tested BPM499 658MHz X0 0607V Y0 1712V serial 0035 Test instrument Stanford Research SR760 Average rms 50 Noise spectra at higher input power a...

Страница 13: ...t Genis Pouilly France Beam Position Monitor Tel 33 450 426 642 Fax 33 450 426 643 Page 11 User s manual BERGOZ Instrumentation 01630 Saint Genis Pouilly France Tel 33 450 426 642 Fax 33 450 426 643 email bergoz bergoz com http www bergoz com Registre des Métiers Bourg en Bresse Registre des ingénieurs Zurich TVA VAT IVA USt Nº FR88414997130 Sàrl capital 152K Siren 414 997 130 R C S Bourg APE 332B...

Страница 14: ...ERGOZ Instrumentation Multiplexed 01630 Saint Genis Pouilly France Beam Position Monitor Tel 33 450 426 642 Fax 33 450 426 643 Page 12 User s manual BERGOZ Instrumentation 01630 Saint Genis Pouilly France Tel 33 450 426 642 Fax 33 450 426 643 email bergoz bergoz com http www bergoz com Registre des Métiers Bourg en Bresse Registre des ingénieurs Zurich TVA VAT IVA USt Nº FR88414997130 Sàrl capital...

Страница 15: ...Analog output Voltage range 0 10V Pedestal ca 1 V DOUT A output Analog output Voltage range 0 10V Pedestal ca 1 V In closed orbit mode the BPM module performance can be monitored with PLLOCK PLL demodulator in lock good signal level TTL output High PLL in lock and signal level OK Low PLL out of lock or signal level poor The DB9 female front panel connector allows the observation of the multiplexed...

Страница 16: ...e injected charge and the pickups sensitivity Note The gain may be different among BPM modules The Single Button Sampling mode is enabled by pulling down SBS Single Button Sampling mode TTL input The button is designated by a 2 bit address BADD0 Button addresses TTL input Active only when SBS mode is enabled BADD1 BADD1 BADD0 Button A high low Button B low low Button C high high Button D low high ...

Страница 17: ...whenever needed While the BPM is in Single Button Sampling mode measure the AGC voltage and record it The AGC voltage is a reliable indication of the potentiometer gain setting The AGC voltage VAGC is available from the front panel DB9 connector pin 3 and from the DIN41612 rear connector pin c19 On the BPM chassis ref BPM RFC xx it is available from the DB15 connector pin 2 BERGOZ Instrumentation ...

Страница 18: ...trary As a consequence the down converted signal varies in amplitude depending on the phase angle Amplitude variations from bunch to bunch i e from conversion to conversion can be as high as 20 These variations are purely statistical and can be eliminated by averaging a series of readings BERGOZ Instrumentation Multiplexed 01630 Saint Genis Pouilly France Beam Position Monitor Tel 33 450 426 642 F...

Страница 19: ...al is applied to GATE disconnected the Fast Gate feature is not active When GATE is pulled down by a NIM 20 mA signal all multiplexer GaAs switches remain open non conducting When GATE is released high 0 mA the GaAs switch addressed by the button address lines BADD0 and BADD1 closes conducting Fast Gate timing 20 ns Beam GATE 0 GaAs switch non conducting non conducting conducting Gated bunches To ...

Страница 20: ...tentiometers allow a fine adjustment of the gain X gain and Y gain BUTA BUTB BUTC BUTD IF BPF Level shift AGC IF BPF RF BPF Attenuators Clock adjust Y gain Σ adj X gain LO Lock Carrier phase F Key Demod phase Demodulator SBS mode fixed level gain GaAs switch driver GATE option Single Button Sampling option Mixer LNA IF IC The gain potentiometers are accessible via holes bored through the Single Bu...

Страница 21: ...n can be approximated by Y gain R169 R151 X gain R168 R141 Requ kΩ 0 93 Gain V 0 034 BERGOZ Instrumentation Multiplexed 01630 Saint Genis Pouilly France Beam Position Monitor Tel 33 450 426 642 Fax 33 450 426 643 Page 19 User s manual BERGOZ Instrumentation 01630 Saint Genis Pouilly France Tel 33 450 426 642 Fax 33 450 426 643 email bergoz bergoz com http www bergoz com Registre des Métiers Bourg ...

Страница 22: ...ng frequency exceeds 100 kHz The 17 bit word is generated by a small daughter board plugged on the BPM module main board Each bit is programmed high or low by a solder bridge to either 5V or ground Solder bridges on the F Key components side are pull ups Solder bridges on the F Key solder side are pull downs Programming bits are numbered as follows bit 17 16 bit 14 bit 13 bit 12 bit 11 bit 10 bit ...

Страница 23: ...king range accepted Top View Pull ups 1 Bottom View Pull downs 0 A B A On request the BPM manufacturer will send the solder bridges layout for a given LO frequency BERGOZ Instrumentation Multiplexed 01630 Saint Genis Pouilly France Beam Position Monitor Tel 33 450 426 642 Fax 33 450 426 643 Page 21 User s manual BERGOZ Instrumentation 01630 Saint Genis Pouilly France Tel 33 450 426 642 Fax 33 450 ...

Страница 24: ...urement Sampling frequency as given by the internal clock Automatic gain control SBS Single Button Sampling mode TTL input Default value high SBS mode not enabled BADD0 Button addresses TTL input Active only when SBS mode is enabled BADD1 BADD1 BADD0 Button A high low Button B low low Button C high high Button D low high Default value Button C PHRESET Peak and Hold Reset TTL input pull down to res...

Страница 25: ...Analog output Voltage range 10V 10V Zero is centered beam Output impedance 100Ω Driving capability 10 mA When BPM SBS option is installed and SBS is low XOUT is analog output value of button addressed from P H circuit Voltage range 0 5V pedestal ca 0 5 V P H circuit is reset by PHRESET low YOUT Y output Analog output Voltage range 10V 10V Zero is centered beam Output impedance 100Ω Driving capabil...

Страница 26: ... sampling frequency also when external clock CLK is active SDEMOD Synchronous demodulator output Analog output For oscilloscope viewing PDEMOD Peak demodulator output Analog output Reserved for future use GAIN External gain setting Analog input on option only Voltage range 0 10V Active only when optional signal AGCD AGC disable is pulled down BERGOZ Instrumentation Multiplexed 01630 Saint Genis Po...

Страница 27: ...ing frequency at least i e up to 1 GHz for 500 MHz operating frequency BPM modules must be installed in an RF shielded chassis Note Unlike most BPM electronics the BPM module does not require the button signal to be in phase Cables do not need to be phase adjusted The BPM module tolerates any phase change even 180 Defective cables examples Frequency response of two defective RG316U 25 cm 50Ω cable...

Страница 28: ...F generator signal to the BPM module via a 4 way splitter see page 4 this manual The BPM noise spectrum should look as printed on the Noise vs frequency hardcopy shipped with the calibration certificate Then connect the BPM to the beam position pick ups If spectral lines noise peaks appear in the spectrum several actions can be attempted to eliminate them Note It is possible that one BPM module ex...

Страница 29: ... response More than 2 kHz LO frequency change can be obtained by installing a few pf capacitor C94 on the BPM board Aliasing was observed on ALS at LBL3 while using the LBL built BPM prototype Jim Hinkson suggests a diagnostic of aliasing and a cure We know the frequencies for synchrotron and betatron oscillations in our machine These frequencies change with machine settings It would be a simple m...

Страница 30: ...ll outputs GND 5 a20 15 PLL demodulator in lock output PLLOCK a13 1 AGC voltage output VAGC 3 c19 2 X also button value in single button mode XOUT 4 c20 3 Y output YOUT 8 b19 4 Σ output SOUT b20 5 A button signal output AOUT a17 6 B button signal output BOUT a18 7 C button signal output COUT a15 8 D button signal output DOUT a16 9 Sync from sampling clock SYNC 9 b14 10 Synchronous demodulator outp...

Страница 31: ...o of the BPM This is useful when the normal beam position is not at the geometric center of the button pick ups b Re adjust the X and Y gains to change the sensitivity of the BPM This is useful in two situations when the beam is very stable the gain can be increased when the beam has very large displacement from the center the gain can be decreased c Re adjust the local oscillator frequency This i...

Страница 32: ...r pin out as used on BPM RFC X and BPM KIT but reversed gender This module is useful because access to the cables at the rear of the chassis will be very difficult With this module one can a Observe and debug the signals sent by the control system to a BPM station b Feed known signals into the BPM readout system to test it RF Service module BPM SERV RF Not available at the time this manual is writ...

Страница 33: ...mands input connector Common to all stations SMA jack RF input for test station IEC male connector for AC mains DB15 female BPM station output connector one per BPM station SMA jack A to D button inputs 4 per BPM station A on top BERGOZ Instrumentation Multiplexed 01630 Saint Genis Pouilly France Beam Position Monitor Tel 33 450 426 642 Fax 33 450 426 643 Page 31 User s manual BERGOZ Instrumentati...

Страница 34: ...output Output on X 0 5V pedestal 0 5V Fast gate NIM 50Ω negative going 16mA pulse Power supply 15V 200 mA 250 mA with SBS option 15V 40 mA 60 mA with SBS option Power Supply module AC mains voltage Autoranging 98 132Vac and 185 265Vac with automatic range changeover Power derating No derating down to 85 Vac at full chassis load Output 15 V unequal loading tolerant Power 75 W Efficiency 84 at 220Va...

Страница 35: ...es available for press fit connection Four or five coaxial plug type connectors series 1 0 2 3 A large number of manufacturers produce these connectors However to assure good connector mating we recommend that you use connectors from Siemens V23601 B302 E71 or V23601 A302 E71 for straight cable attachment to RG316 Øext 2 6mm V23601 A302 E1 for straight cable attachment to RG178 Øext 1 9mm V23601 A...

Страница 36: ...Richard W Biscardi for the National Synchrotron Light Source at Brookhaven National Laboratory U S Patent 5 001 416 was granted to them on March 19 1991 We sincerely thank them for their considerable contribution Our BPM module was developed on the basis of Jim Hinkson s Precision Analog Signal Processor for BPMs in Electron Storage Rings designed for the Advanced Light Source at Lawrence Berkeley...

Страница 37: ...s from Siemens Excerpt from Siemens Plug connectors data book 1992 Other references Siemens RF connector data book part number A23001 G22 D004 X 7400 Siemens Connector DIN41612 data book part number A23001 G21 D012 X 7400 ...

Страница 38: ...Siemens Cont d Excerpt from Siemens Plug connectors data book 1992 Other references Siemens RF connector data book part number A23001 G22 D004 X 7400 Siemens Connector DIN41612 data book part number A23001 G21 D012 X 7400 ...

Страница 39: ...Annex II ...

Страница 40: ......

Страница 41: ......

Страница 42: ...erator environment Introduction Beam position monitors BPM are essential diagnostic instruments in a particle accelerator and every accelerator project usually includes the development of a specific beam position monitoring system Conventional beam positions pick ups use 2 or 4 electrodes directional couplers or buttons as position sensors Beam position is a function of the amplitude difference of...

Страница 43: ......

Страница 44: ... self contained and independent of any external control or timing system In its default operating mode the user has only to connect the pick up signals and the power supplies and obtains the normalised x and y outputs All intermediate coaxial connectors were eliminated by using on board miniaturized band pass filters micro strip low pass filters and adjustable attenuators This improves the reliabi...

Страница 45: ...all area on the circuit board Not shown on the diagram are the high pass filters 7 MHz which protect the switches from an accidental dc or low frequency ac input The attenuators if required reduce the signal power to the maximum level which the amplifier can accept A 1 dB variable adjustment is used to equalize insertion loss in all 4 channels The output impedance of the 4 channels as seen by the ...

Страница 46: ...ficant amplitude or phase noise to the processed signals A frequency synthesizer is used as a source It consists of a VCO voltage controlled oscillator with programmable divider 5 phase locked to a reference frequency fref A 17 bit serial word from the plug in F key module selects the divider ratio for a specific receiver centre frequency Spectral purity of the local oscillator depends on the choi...

Страница 47: ...g on all signal cables coming from the pick ups We preferred to solves this problem in a different way Our loop filter has an electronic switch not shown in Fig 1 which reduces the time constants during 10 µs after channel switching This allows the receiver to settle on a new signal level as a result phase errors up to 180 are tolerated Fig 3 Frequency response of if amplifier BPM processor for AL...

Страница 48: ...take care of the small residual discontinuity of these connections The test set is used for measuring impedance and transfer functions Fig 3 for frequencies up to 3 GHz Testing the transient response of feedback agc and phase locked loops uses the same type of test connections but requires a different instrument set up Generally speaking the method consists of injecting a square wave modulated sti...

Страница 49: ...Hz less than 0 5 µm rms for a bandwidth 0 to 100 Hz zero stability fi X and Y zero drift less than 0 5 µm during 10 hours Linearity fi Over 60 dB of input signal range less than 5 µm error within 0 5 mm of centre less than 10 µm error within 3 mm of centre References 1 R E Shafer Beam position monitoring AIP Conf Proc 212 pp 27 58 1989 2 J A Hinkson K B Unser Precision Analog Signal Processor for ...

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