NATIONAL RADIO ASTRONOMY OBSERVATORY Green Bank, West Virginia Electronics Division Internal Report No. 88 MULTIFILTER RECEIVERS

Transcription

1 NATIONAL RADIO ASTRONOMY OBSERVATORY Bank, West Virginia Electronics Division Internal Report No. 88 MULTIFILTER RECEIVERS D. L. Thacker and Lewis Beale OCTOBER 1969 NUMBER OF COPIES: 100

2 MULTIFILTER RECEIVERS D. L. Thacker and Lewis Beale TABLE OF CONTENTS Page I. Abstract (i) II. General Description 1 HI. 40- Receivers 1 MHz and 5 MHz s 4 IV. 50- Receivers 30 khz and 10 khz s 17 I. ABSTRACT References: (1) Electronics Division Internal Report No. 70, "The NRAO 50- Spectral Line Receiver, n by Michael Balister. (2) Electronics Division Internal Report No. 79, "Synchronous Detector and Readout System, " by Kok Chen. (3) Electronics Division Internal Report No. 85, "The 40/50 Integrator /Multiplexer, " by Ray Hallman. (4) Computer Division Internal Report No. 7, "Multi- Receiver On-Line Programs, " by Bob Vance. This report contains the necessary block diagram and schematics for main tenance and interfacing with the new multifilter receiver plus a general, verbal description to acquaint the users with the filter bank. The above references must be consulted for a complete understanding of the system. (i)

3 II. GENERAL DESCRIPTION A set of 5 multifilter banks has been built at NRAO for use on spectral line receivers or pulsar receivers. They are: khz (hereafter referred to as the old 50-channel) per channel using L.C. tuned amplifier for a contiguous filter bank. For a description of the receiver see EDIR No MHz per channel using passing L.C. filter (purchased from I-Tel) MHz per channel using passing L.C. filter (purchased from I-Tel) khz per channel using 10.7 MHz crystal filter and separate LO's for each channel khz per channel every MHz crystal filters and separate LO's for each channel. Prototype parts have been ordered for two additional receivers, a 50-channel 100 khz per channel using MHz crystal filter and offset LO's and a 50-channel (300 or 250) khz per channel using MHz L.C. filters and offset LO' s. In building the last four receivers listed above, the output levels, connectors, and input signal conversion that were used on the first 50-channel receiver were fol lowed. (See Table 1.) This allows one to use the same software and interfacing with all systems. There are, of course, minor changes that have to be made when using the 40-channel receiver in place of the 50-channel because of the difference in number of channels. One simple expedient that has been used in the past has been to simulate channels by jumping selected channels of the receiver outputs to the channel input of the computer interface. For more information on the integration of the line receiver with the DDP-116 computer, see section 3 of EDIR No. 70. The following block diagram shows this chief difference between the 40-channel receiver and the new 50-channel receiver and it also should clarify crystal filter off set LO techniques. (See Figure 1 and Table 1.)

4 IF INPUT P S 0 P WL E I R T T E R ^ FILTER AMP p S 0 P w L E 1 R T T E FILTER! fdetector' N REPEATED 40 TIMES DC AMP OUT SWAY SWAY 40 CHANNEL IF INPUT' MIXER dojmhz FILTER F XTAL 10.7 MHz AMP -D> DETECTOR DC AMP > OUT I to I H> i> OUT ^->f -CHANNEL SEPARATOR - BW XTAL FILTER SAME FOR OTHER 48 CHANNELS 50 CHANNEL FIG. 1

5 -3 - TABLE 1 Multifilter of IF Resolution Receiver s Frequency ( Width) khz (old) MHz MHz khz khz (IdB) MHz (3 db) MHz (3 db) khz (6 db nom.)

6 -4 - HI. 40-CHANNEL RECEIVERS The two 40-channel receivers show a common IF driven box and therefore cannot be used simultaneously. Change over time from one bandwidth to another is approximately 1/2 hour. Note that the driver unit has a specially keyed DC power connector which prevents plugging in a standard DC power cord. Do not try to de feat its purpose. Table 2 lists the nominal center frequencies and bandwidths of the fixed, tuned 3-section L.C. filters that are used in the receivers. There is some distor tion of the expected filter band shape and center frequency caused by the interaction of adjacent filters. This rarely causes a shift in center frequency of a channel larger than 30 percent of the channel bandwidth. The block diagram, schematics (Figs. 1-5), rear panel connector listings (Tables 3-5), and photographs are selfexplanatory. s on the 40-channel are left open-circuited.

7 # (5) wv ^A^ #8 ( ) 33 r 33 FILTER 71/1 (52.5/5) 72/1 (57.5/5) 73/1 (62.5/5) 74/1 (67.5/5) 75/1 (72.5/5) ALL UNITS ARE IDENTICAL TO ABOVE WSH> VW- DETECTOR & DC AMPLIFIER EXCEPT FOR FILTER CENTER FREQUENCY. (TOTAL OF EIGHT UNITS ) 106/1 (227.5/5) 107/1 (232.5/5) 108/1 (237.5/5) 109/1 (242.5/5) 110/1 (247.5/5) DETECTOR & DC AMPLIFIER ii ti J CHANNEL ^ I, COM. OUT ^2, COM. OUT #-3,C0M. OUT #4, COM. OUT #5, COM. OUT #36 TT if #38 #39 # 40 COM. OUT f T0J2-JJ TO J2-FF TO J5-B TO J2-EE TO J5-A SWITCH SHOWN 100 K IN UP POSITION ^A^, T0J5-D TO J2-HH TO J5-C ^Ci, A TOTAL OF 40 CKTS IDENTICAL TO ABOVE ONE FOR EACH CHANNEL T0J2^ \<i TOJ5-Z TO J2e T0J5-Y i - 'NUL JI & J 2-TO COMPUTER J5 1 J6-T0 ANALOG OUTPUT SYSTEM TOTAL POWER OUT NOTE: NUMBERS IN ( ) REFER TO VALUES FOR 5 MHz/CHANNEL RECEIVER TOTAL POWER IN >JI-EE >J6-AA >J6-CC I I BLOCK DIAGRAM OF 40 CHANNEL MULTIFILTER RECEIVERS FILTER BANK ne. 2

8 NOTES: 1. SAME DC AMP. AS FOR EACH CHANNEL EXCEPT USES EXTERNAL DETECTOR 2. ALL AMPLIFIERS - APD-3 AVANTEK 3. FILTERS -I-TEL FBT/20 3 SECTION, 50A WITH BNC CONNECTORS EXCEPT WHERE NOTED 4. USE LOWER CHAIN FOR 1MHz FILTERS -1MHz. 5 MHz <: 62.5/30 73 /6 87.5/30 -K /6 II2.5/30 83/6 I37.5/30 88 / 6 IF '/jj^ FLT/ /50- Vjri -3A/3A D HP ATTENUATOR 3556 IT i FILTER I-TEL FILTER MFBT/20-90/ /50-3A/3A.-_ ADP- I IS i 8 WAY POWER SPLITTER ISO-T TV-50 DETECTOR I62.5 /30 #5 93/6 I87.5/30 #6 98/6 2I2.5/30 ~~^ #7 I03/6 as /30 #8 + 2«V TOTAL POWER AM NOTE 1 I TOTAL BNC \9J POWER B.P. ^"^ OUT (DETECTOR OUT) I08/6 BLOCK DIAGRAM OF 40 CHANNEL MULTIFILTER RECEIVER DRIVER DRAWER FIG. 3

9 -7-20 K 200pF I5V-WV-+I5V. jf TRIM RESISTOR SUPPLIED WITH AMP. R -SELECTED FOR BEST SQUARE LAW CHARACTERISTICS, TYPICAL VALUE ABOUT 430 fl. CKTS.-SAME FOR 5 81 MHz RECEIVERS DETECTOR 8 DC AMPLIFICATION FOR 40 CHANNEL RECEIVERS FIG. 4

10 s V (2) +I5V.0068»T0 AVANTEK BNC ZERO CHECK IW 2N22I9 OR 2NI6I3 + I5V i oo i -I5V OVOLTS-0 (7mA) -6 VOLTS OR OPEN CKT. «OPERATE ZERO CHECK CKT. for 40 CHANNEL DRIVER FIG. 5

11 -9 - TABLE 2 Center Frequencies 5 MHz 1 MHz Bandwidth Bandwidth

12 TABLE 3 Back Panel Connectors, Cable Connection, and Color Code for 40 and 50 Jl Filter Analog Buffer Pin Bank No. nolnv \*/\JX\J ±. C!OHP vyvsu.*-' A 3 16 Red B Black C 4 17 D Black E 5 18 F Black H 6 19 Blue J Black K 7 20 Brown L Black M 8 21 Yellow N Black P 9 22 Orange R Black S T Red U V Red w Blue X Red Y Yellow z Red a Brown b Red c Orange Continued

13 Table 3 (continued) Jl Filter Analog Buffer Pin Bank No. Color Code e Blue f h J k Brown 1 m Orange n P Yellow r s Blue t u Brown V w Orange X y Yellow z AA Brown BB Blue CC Orange DD Blue EE Total Pwr 13 Yellow FF from BNC Blue HH Gnd Gnd Orange JJ Gnd Gnd Brown KK Gnd Gnd Yellow LL Gnd Gnd Brown MM Gnd Gnd

14 TABLE 4 Back Panel Connectors, Cable Connection, and Color Code for 40 and 50 J2 Filter Analog Buffer Pin Bank No. Color Code A Red B Black C D Black E F Black H Blue J Black K Brown L Black M Yellow N Black P Orange R Black S T Red U V Red w Blue X Red Y Yellow z Red a Brown b Red c Orange d Red e Blue Continued

15 Table 4 (continued ) J2 Pin Filter Bank Analog Buffer No. Color Code h J k 1 m n P r s t u V w X y z AA BB CC DD EE FF Brown Orange Yellow Blue Brown Orange Yellow Brown Blue Orange Blue 1 14 Yellow Blue

16 TABLE 5 Back Panel Connectors, Cable Connection, and Color Code for 40 and 50 J5 Pin Filter Bank Color Code A B Red Black C D Black E F Black H J Blue Black K L Brown Black M N Yellow Black P R Orange Black S T Red U V Red w X 10 Blue Red Y z 11 Yellow Red a b 12 Brown Red c d 13 Orange Red e f 14 Blue Continued

17 Table 5 (continued) - 15 J5 Pin Filter Bank Color Code h J k 1 m n P r s t u V w X y z AA BB CC DD Bpawn 17 Orange 18 Yellow 19 Blue 20 Brown 21 Orange 22 Yellow 23 Brown Blue 24 Orange Blue EE FF Total Pwr from BNC Yellow Blue

18 - 15a - TABLE 6 Back Panel Connectors. Cable Connection, and Color Code for 40 and 50 J6 Pin Filter Bank Color Code J6 Pin Filter Bank Color Code A B C D E F H J K L M N P R S T U V W X Y Z a b c d e f Red Black Black Black Blue Black Brown Black Yellow Black Orange Black Red Red Blue Red Yellow Red BT own Red Orange Red B;ue Greta: m n P r s t u V w X y z AA BB CC DD EE FF HH JJ KK LL MM NN Gnd Gnd Gnd Gnd Gnd Gnd Brown Orange Yellow Blue Brown Orange Yellow Total power from BNC Total power from BNC Spare Spare Spare Spare

19 Front Panel of 5 MHz Receiver Back Panel of 5 MHz Receiver

20 IV. NEW 50-CHANNEL RECEIVER The 10 khz and 30 khz 50-channel receivers use the fixed filter, offset LO technique, that is shown in Figure 1. This permits the use of a standard filter to determine the bandpass characteristic of the channel, which results in greater re peatability from channel to channel plus greater economy. The center frequencies of the channels are determined by crystal osciuators, which gives better stability than L. C. filters plus the freedom to easily change center frequencies. The 10 and 30 khz receivers are similar in design with the only differences being the crystal filter and its matching resistors and the crystal frequency of the channel LO. Mechanically, the receivers are identical, which allows printed circuit cards to be interchanged or mixed. Output connectors and zero check levels are the same as on other receivers. Output level is nominally +1 volt DC. The following diagrams (Figs. 6-9), tables, and photographs are to assist in troubleshooting and repair and are essentially self-explanatory (Figs. 7-8). The cost for parts is approximately $ 100 per channel.

21 BACK PANEL TOTAL / ~ POWER ( } I-25CH. ZERO CmV CHECK ^ INPUT /s\ l-zsch.^ T TOTAL PWR. DET. SAMP. 5 WAY POWER DIVIDER 5CH. DETECTOR BOARDS I 2 OUTPUT TO Z4 CONNECTORS CH.(5) INPUT CH. TOTAL POWER CH METER MONITOR F.P. N)0-2V <3~o IOOK 4- " «A/\A» ' I TOTAL POWER SW. BLOCK DIAGRAM OF 50 CHANNEL RECEIVER Figure 6

22 l NOTE: Rx VALUE DEPENDENT ON FILTER (EX: 30KC/2K & I0KC/680A) 5 CHANNEL FILTER & DETECTOR BOARD CARD CONNECTOR END Figure 7

23 -20 - RF IN.01 IN I II t tt 470 IOO/I H S)O5T.01 IN J 100/i.H OUT DIODE SWITCH. I.5K IIV ZENER IN474I -I5V DIODE SWITCH DRIVER 50 CHANNEL MULTIFILTER I0-30KHZ Figure 8

24 K TRIM TOTAL S-y. POWER t^-k+j BACK PANEL V ASB CKTS.-SAME FOR-30 a 10-KHz TOTAL POWER DETECTOR a PC AMPLIFICATION FOR 50 CHANNEL RECEIVERS Figure 9

25 -22 - TABLE 7 Crystal Frequency and Center Frequency for the 30 khz Multifilter Receiver Frequency LO LO (Crystal (Crystal Frequency Oscillator Oscillator Frequency) Frequency)

26 TABLE 8 Crystal Frequency and Center Frequency for the 10 khz Multifilter Receiver Frequency LO LO (Crystal (Crystal Frequency Oscillator Oscillator Frequency) Frequency)

27 -24 - o STRR MONirOR PVP 'vski ' $*? ^* " *^* i ^*? ^ ^ ^ f' f '* 4 ^ * * 4 ' r' '# ir' '# r f t- r 40 <5 50 ^ ^ p> ^ frffef* ^ (r '? r "r V 'f' f ^; * ^, * * ^> '* $ '* $ Front Panel of khz Receiver Back Panel of khz Receiver TOTAt POWER 1-25

28 Top View of 30 khz and 10 khz Printed Circuit Board Botton View of 30 khz and 10 khz Printed Circuit Board