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3.9.1.2 SWR Operation

The SWR meter displays impedance in specific formats. Refer to an antenna or radio

handbook for detailed information on these quantities.

3.9.1.2.1 SWR

SWR is the same as voltage standing wave ratio. This can be used to roughly determine

an antenna’s match to its coax.

3.9.1.2.2 Return Loss

The amount of transmitted energy that is reflected back, expressed in dB’s.
Example! - If you are transmitting 100 Watts and have 1 Watt reflected, the 1 Watt is 20

dB less than the forward power, so the return loss is –20 dB.

3.9.1.2.3 Reflection Coefficient Magnitude

This is the magnitude of the S11 vector. Minimum value is zero and implies perfect

match. Maximum value is 1.0, complete reflection of energy.

3.9.1.2.4 Reflection Coefficient Angle

This is the same thing as the phase angle of the S11 vector. This angle contains the

information to determine cable length. Combined with the magnitude, all the impedance
information can be determined.

3.9.1.2.5 Q Factor

The 2:1 SWR bandwidth is used to calculate the circuit Q. The Q is displayed

numerically when the plot has 80 points, and one of the plots displayed is SWR.

3.9.2 Right Plot Data

Any data available for the left plot can be plotted on the right plot. Even the same data

can be plotted on both plots (use different scales to see both). See paragraph 3.9.1 for
detailed information on plots. The curve of the right plot is always a hashed line.

3.9.3 RLC Model, Series or Parallel

The equivalent L or C (calculated from the reactance at the center frequency) can be

displayed numerically in CW mode or when using a 100 point plot.  The equivalent load
appears as a resistor and a capacitor (or resistor and inductor).  The values of the resistance
and reactive component can be calculated as two components in series or two components
in parallel.  Selecting series or parallel determines which calculation is used when displaying
resistance or reactance.  This calculation (series or parallel) affects both the numeric output
and the plots for resistance or reactance.  This option has no effect on SWR plots, total Z, or
impedance angle.

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Содержание VIA Bravo MRI

Страница 1: ...MRI Network Analyzer MRI Network Analyzer 100KHz to 70 MHz ...

Страница 2: ...ntained herein for purposes other than operation and or maintenance is prohibited without written authorization from AEA Technology by AEA Technology Inc All rights reserved This document and all software or firmware designed by AEA Technology Inc is copyrighted and may not be copied or altered in any way without the written consent from AEA Technology Inc Bravo PC Vision TM and AEA Logos are trad...

Страница 3: ...ment Mode 7 3 9 F3 PLOT DATA PROPERTIES 8 3 9 1 Left Plot Data 8 3 9 2 Right Plot Data 9 3 9 3 RLC Model Series Parallel 9 3 9 4 Plot Width 10 3 9 5 Big Frequency Display 10 3 10 F4 SCALES AND LEGENDS 10 3 10 1 Grid Lines 10 3 10 2 X Axis Label 10 3 10 3 Left Plot Scale 10 3 10 4 Right Plot Scale 10 3 11 F5 MEMORY AND MISCELLANEOUS 10 3 11 1 Save Operation 11 3 11 2 Recall Operation 11 3 11 3 Plot...

Страница 4: ...t and Contrast 20 8 1 2 Power On Preset Value if Contrast Was Lost 20 8 1 3 Power Induced Failure 21 8 2 BATTERIES 21 8 3 SERIAL PORT 21 8 4 OTHER PROBLEMS 21 9 APPENDICES 22 9 1 VIA BRAVO MRI SPECIFICATIONS 22 9 1 1 Output Characteristics 22 9 1 2 Measurement Specifications 22 9 1 3 Display Characteristics 23 9 1 4 Miscellaneous Specifications 23 9 1 5 Absolute Maximum Ratings 24 9 1 6 Size 25 9 ...

Страница 5: ...oax is displayed The VIA Bravo MRI operates over a wide range of characteristic impedances so you are not limited to measuring 50 ohm systems The VIA Bravo MRI periodically self calibrates during operation The VIA Bravo MRI determines when recalibration is required and displays the marquee screen with a CALIBRATING message during the calibration The unit begins measurements after a few seconds Thi...

Страница 6: ...ertain values and the VIA Bravo MRI adjusts your entry to an available sweep width The VIA Bravo MRI flashes a brief warning if it changes the sweep width from the number you entered The x axis legend displays the lower and upper sweep frequencies Press the OFF key The settings you have entered are automatically saved prior to the unit shutting off The next time you power up these settings will re...

Страница 7: ...t you may need to add zeroes to get your entry to align properly with the decimal point When the correct number is ready press the ENTER key The unit should start plotting with the new center frequency after a re calibration cycle only if you are not in cable null mode You may also alter the center frequency using the FREQ keys The center frequency will shift up or down by the frequency step size ...

Страница 8: ...width you can continue to enter digits use zeros until an illegal width too wide is entered Eventually the display resets allowing you to start a new sweep entry You are allowed to interrupt calibration cycles when you enter a width command A new calibration cycle will start after you enter your new width 3 3 Frequency Step Size The frequency step size determines the change in center frequency whe...

Страница 9: ...occurs at the edge of the calibrated frequencies If you wish to remove the truncation you must force a new calibration cycle One way to do this is to just enter a new center frequency paragraph 3 1 Other ways to force a calibration cycle are to press the FREQ or WIDTH arrow keys while in the plot mode paragraphs 3 2 or 3 3 EXAMPLE Once you press the EXAM PLOT key the cursor comes up Press the FREQ...

Страница 10: ...ight goes out after 10 sweeps If you press a key ENTER for example the light will come on again for another 10 sweeps after returning to measuring Also note the maximum intensity is limited and the backlight will only be noticed in dim light conditions When the VIA Bravo MRI is in a bright environment the backlight will be washed out The lowest brightness level is equivalent to the off setting 3 8...

Страница 11: ...en CW and Sweep mode see paragraph 3 2 3 8 4 1 1 Sweep Mode with or without cable This mode measures impedances and can plot one or two of the following quantities 1 Total impedance Z 2 Impedance angle A or Theta 3 Resistance R 4 Reactance X 3 8 4 1 2 CW Mode with or without cable In CW mode all of those quantities see above are displayed numerically along with the frequency SWR and return loss 3 ...

Страница 12: ... same info that can be extracted or plotted on a Smith Chart 3 9 1 1 1 Total Impedance This is the total Z of the load It is equal to the square root of the sum of resistance squared and reactance squared If resistance and reactance are made to be the two legs of a right triangle the total Z is the hypotenuse 3 9 1 1 2 Impedance Angle The impedance angle is the ratio of resistance to reactance exp...

Страница 13: ... determined 3 9 1 2 5 Q Factor The 2 1 SWR bandwidth is used to calculate the circuit Q The Q is displayed numerically when the plot has 80 points and one of the plots displayed is SWR 3 9 2 Right Plot Data Any data available for the left plot can be plotted on the right plot Even the same data can be plotted on both plots use different scales to see both See paragraph 3 9 1 for detailed informati...

Страница 14: ...be reading the numbers more than you will be examining the plots This option is also useful when you are examinig the plots on the VIA Director program and you just want to check the status of the VIA Bravo MRI from a distance 3 10 F4 Scales and Legends This menu allows you to select the plot scales the x axis format and the number of horizontal grid lines to show See Below 3 10 1 Grid Lines You c...

Страница 15: ...ursor across it Once you leave the exam mode the display is updated with new data but the saved data is still intact in the save memory slot ready to be recalled again if necessary 3 11 3 Plot Name Allows you to assign up to a 12 character name to the save data A descriptive name will help you remember what the plots are when downloading the data to a PC You can enter the name via this submenu or ...

Страница 16: ...IA to cable nulling after power up see 3 8 4 1 3 12 1 Cable Definition The coaxial cable characteristic impedance Z0 must be defined for cable nulling to operate properly This can be done in the Cable Characteristics sub menu see 3 11 4 3 12 2 Nulling Procedure The nulling procedure begins by selecting a with cable option when setting up the VIA instrument mode see 3 8 4 1 Install the cable to be ...

Страница 17: ...es The VIA Bravo compliments the plot displays with a number of numerical quantities These quantities depend on the sweep settings and the instrument mode 3 12 5 80 Point Sweeps The 80 point sweeps use large font numbers that can be read from about 10 feet away with proper lighting backlight conditions 3 12 5 1 VIA Mode There are three numbers displayed all of these numbers are center frequency va...

Страница 18: ... 1 Total Z 2 Z angle 3 Resistance 4 Reactance 5 Capacitance Inductance see para 3 12 5 1 3 12 6 2 SWR Mode There a 4 numbers displayed in a small font The numbers are in order from top to bottom 1 SWR 2 Return loss 3 S11 magnitude 4 S11 angle 3 12 7 CW Mode When in CW mode all relevant information is displayed with large font numbers ...

Страница 19: ...k for zero phase crossing from lower left to upper right Impedance will be very low This method is less preferred as the coax must be re shorted after every snip 4 2 Make a wavelength coaxial line To make a coaxial line that is tuned to one quarter wavelength 1 Start with a piece of coax that is slightly longer about 5 to 10 than calculated The formula for a wave cable is L 245 5 vf fr where L len...

Страница 20: ...gs there are below the frequency of interest The length in degrees is L 180 number of zero crossings modified RCA Calculate the modified RCA using this algorithm if the RCA is positive then subtract off 360 from RCA if RCA is negative don t subtract anything Now multiply the new RCA by negative The result will be a number between 0 and 180 To convert the length to wavelengths divide L by 360 EXAMP...

Страница 21: ... provided on your CD package and hit ENTER This is CASE SENSITIVE so be sure to type it in exactly as listed on your documentation The upper left corner of the title box should now say Registered to your registration name You need to do this within 15 minutes of starting the software or you will get a note stating that the DEMO PERIOD IS OVER If this happens to you Do NOT hit the OK button Click o...

Страница 22: ...urce other than the AEA Technology s AC adapter ensure that it meets the requirements of 9 1 4 3 1 6 3 Batteries Due to the strong magnetic fields involved with MRI servicing the use of batteries is not recommended Both the VIA Bravo MRI unit and the MRI unit under test could be more susceptible to damage if batteries were installed We have had some success with the new NiMH batteries within 8 fee...

Страница 23: ...l or workmanship for a period of one year from the date of shipment All units returned to the factory delivery charges prepaid and deemed defective under this warranty will be replaced or repaired at this company s option No other warranties are implied nor will responsibility for operation of this instrument be assumed by AEA Technology Inc ...

Страница 24: ...adings Cable nulling function is in wrong state 3 12 8 1 Contrast 8 1 1 Environment and Contrast Occasionally changes in temperature or ambient light conditions may necessitate adjustment of the display contrast Instructions may be found in section 3 8 2 8 1 2 Power On Preset Value if Contrast Was Lost If the contrast has dropped so you cannot see the display then you can try the following procedu...

Страница 25: ... RTD Users Verify that your Software and Computer settings conform with the specifications in Section 9 1 4 2 Terminal Users Verify that you are observing the protocols specified in Sections 9 1 4 2 and 9 3 8 4 Other Problems If you have any questions concerning instrument maintenance cleaning care or before making any return warranty or out of warranty for an operational issue material defect or ...

Страница 26: ...m for higher frequencies 9 1 1 5 RF Connector BNC type receptacle 9 1 1 6 Output Impedance 50 ohms nominal VSWR typically better than 1 3 1 Operates with non 50 ohm systems 9 1 1 7 Output Distortion Harmonic distortion 30dB for 25MHz or less 15 db for 70MHz or less 9 1 1 8 Phase Noise Better than 75dBC 10KHz offset for 25 MHz or less Better than 65dBC 10KHz offset for higher frequencies 9 1 2 Meas...

Страница 27: ...ce Same as resistance but 100 etc Total Z Same as resistance Z angle 15 45 90 degrees SWR 1 to 3 6 11 no units Return Loss 0 to 20 50 90 dB S11 Magnitude 0 to 0 2 0 5 1 0 no units S11 angle 15 45 90 180 degrees 9 1 3 2 Graphing Formats All graphs are X Y format Select one or two plot curves Left axis plots with thin line Right axis plots with hashed line X axis is 81 or 101 points wide 9 1 3 3 Plo...

Страница 28: ... Bravo MRI unit 9 1 4 3 1 DC input Power jack Min 12 VDC 300 ma Typical 14VDC 250ma Max 20VDC 250 ma Positive polarity is applied to the center pin of the power jack for proper operation 2 1 mm center pin DC power connector 9 1 4 3 2 Battery Power If battery power must be used only use an external battery pack that will sit outside the magnetic field A sealed lead acid battery will avoid the dange...

Страница 29: ...Power Jack 20VDC Maximum 9 1 5 3 Serial Port Input Max applied voltage on Ring TD 20 VDC Max applied voltage on Tip RD 10 VDC 9 1 6 Size 8 5 x 4 3 x 2 25 inches 235 x 110 x 57mm 1 9 lbs 800grams with batteries and beltcase ...

Страница 30: ...ot selection Plot 2 scale Scale choices vary with plot selection Save Enter 1 to 24 Enter memory name Recall Enter 1 to 24 Plot Name Alpha numeric entry up to 12 chars Z0 Numeric Entry routine with limit checks VF Numeric Entry routine with limit checks Exit Com port baud 4800 9600 19200 28800 52600 Self Test Self rest results and keypad tester Backlight Time Intensity Z scales 100 200 500 1K and ...

Страница 31: ...r is denoted by the prefix letter of the next piece of information At the end of the command or response string an End Of String EOS marker is appended This EOS marker pushes the last piece of information through the software routines Some commands do not require the EOS marker The VIA Bravo MRI unit sends an EOS marker in response to a command If the VIA Bravo MRI doesn t understand the command n...

Страница 32: ...ly operates in the SWR mode No EOS marker is required but one may be sent if desired 9 3 1 1 3 Mxx Read the data stored in memory location xx The EEPROM memory location contains the unit setup info and sometimes the plot from a single sweep saved by the user The maximum value of xx depends on the unit version and can be obtained using the S000 command The number sent for xx should always be a 2 di...

Страница 33: ...in pairs Z A or R X etc count as one data point Dxxx 101 to 104 Data format See D in unit setup command Defines the type of data that follows Measured Data Formats Characters Sent Range of x x Range of y y Meaning Notes Rx xXy y 0 to 32 767 32 768 to 32 767 R 10x ohms X 10x j ohms insert Before last digit Resist React D 101 Zx xAy y 0 to 32 767 899 to 899 Z 10x ohms A 10x degrees insert Before las...

Страница 34: ...ta lower and upper valid data indices Data that is not valid is garbage and should be tossed out Memory Read Response Table Characters Received Range of x x Meaning Notes Mxx 1 to Memmax Header allows software to verify response Memmax can be found with S000 command S001 plus Setup data State of the unit when the data was saved to memory Format is identical to S000 response w S001 header instead o...

Страница 35: ...inition of xxx 9 3 3 1 4 S100 Set the unit s configuration An entire block of configuration data follows this command The format of this data block is identical to the unit response for configuration request without the S002 No EOS marker is required if immediately followed with another command but one may be sent if desired If this is the last command in a string the EOS marker must be used The E...

Страница 36: ...tory use Ax x 0 to 50 Lower plot index Equal to 0 except when the sweep would try to extend below the minimum calibrated freq Ax x 40 to 100 Upper plot index Usually the same as points in a sweep except when sweep extends beyond maximum cal freq Ax x 0 to 1 Auto power shutoff 0 disabled 1 enabled Ax x 0 to 3 Calibration Mode 0 1 sweep 2 3 CW 1 3 Cable null mode Ax x 0 to 255 Backlight Intensity Co...

Страница 37: ... down key Ax x 100 to 50 000 Min width KHz in 100MHz octave Ax x 10 000 to 100 000 Max width KHz in 100MHz octave Ax x 1 to 1000 Min center freq KHz Ax x 1000 to 100 000 Max center freq KHz Ax x 0 to 199 Lower valid data index Base 0 beginning of valid data Ax x 1 to 200 Upper valid data index Base 0 end of valid data Ax x alphanumeric Memory Name user defined name for location Mxx up to 12 charac...

Страница 38: ...M01 M01S001F200000W4000A0 A7 0000 Read Save memory 1 Freq 200K Width 4KHz Instrument mode VIA Max center freq 70MHz S000 S002F500000W32000A1 A700 00 VIA Bravo MRI s current settings Freq 500K Width 32KHz Instrument mode SWR Max center freq 70MHz F5000000 Center freq 5MHz W800000 Sweep width 800KHz D102 Set unit to read total Z and Z angle Q Q345 Q is 34 5 Command Response Notes S100F1000000 A660 S...

Страница 39: ... M 109 m 14 46 78 N 110 n 15 47 79 O 111 o 16 48 0 80 P 112 p 17 XOFF 49 1 81 Q 113 q 18 50 2 82 R 114 r 19 XON 51 3 83 S 115 s 20 52 4 84 T 116 t 21 53 5 85 U 117 u 22 54 6 86 V 118 v 23 55 7 87 W 119 w 24 56 8 88 X 120 x 25 57 9 89 Y 121 y 26 58 90 Z 122 z 27 59 91 123 28 60 92 124 29 61 93 125 30 62 94 126 31 63 95 _ 127 Characters 0 to 31 are not used by VIA Bravo MRI except for XON XOFF Lower...

Страница 40: ...8 50 52 93 HJ9 50 52 93 HJ11 50 52 92 HJ12 50 52 93 LDF2 50 52 88 LDF4 50 52 88 LDF4 75 73 88 RG 6 U 9116 73 82 RG 6A U 8215 73 78 RG 8 U 8214 52 78 RG 8 U 8237 52 66 RG 8 U 9913 52 84 RG 8 U 9914 52 78 RG 8A U 9251 52 66 RG 8 X 9258 52 78 RG 9 U 8242 52 66 RG 11 U 8213 73 78 RG 11 U 8238 73 66 RG 11A U 8261 73 66 RG 11 U 9011 73 82 RG 58 9203 52 66 RG 58 U 8240 52 66 RG 58A U 8219 52 78 RG 58A U ...

Страница 41: ... 70 RG 142B U 52 70 RG 174 U 8216 52 66 RG 178B U 52 70 RG 179 83264 73 70 RG 180 83266 93 70 RG 187A U 73 70 RG 188A U 52 70 RG 212 U 9861 52 66 RG 213 U 8267 52 66 RG 214 U 8268 52 66 RG 216 9850 73 66 RG 223 U 9273 52 66 RG 303 84303 52 70 RG 316 84316 52 70 RG 316 U 83284 52 70 RG 402 U 1673A 52 70 RG 405 U 1671A 52 70 ...

Страница 42: ...38 NOTES ...

Страница 43: ...39 NOTES ...

Страница 44: ...5933 Sea Lion Place Suite 112 Tel 800 40 5933 Sea Lion Place Suite 112 Carlsbad CA 92010 Tel 800 258 7805 or 1 760 931 8979 Fax 1 760 931 8969 www aeatechnology com ...

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