Download Functional Block Descriptions - VLF Designs specializing in Analog

ISIS 3
INTEGRATED SEISMIC INSTRUMENTATION SYSTEM
RADIO TELEMETRY SYSTEM
Rev: A
01/2012
VLF DESIGNS
1621 BELLA VISTA DR
JACKSON,MO. 63755
573-204-1286
[email protected]
1
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
TABLE OF CONTENTS
ISIS 3 OVERVIEW
3
ISIS 3 SPECIFICATIONS
4
FUNCTIONAL BLOCK DESCRIPTIONS
RECEIVER
5
OUTPUT MULTIPLEXER
5-8
TRANSMITTER
9
CANISTER
10
OUTPUT TEST CABLE
10
ADJUSTMENTS
TRANSMITTER
11
RECEIVER
11-12
OUTPUT MULTIPLEXER
12-13
3 CARRIER OUTPUT MUX LEVEL SPREADSHEET
14
6 CARRIER OUTPUT MUX LEVEL SPREADSHEET
15
APPENDIX A HAMTRONICS RECEIVER DOCUMENTATION
16-22
APPENDIX B HAMTRONICS TRANSMITTER DOCUMENTATION
23-30
APPENDIX C PARTS LISTS
31
RADIO CANISTER
32-35
OUTPUT MULTIPLEXER
36-38
2
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
ISIS 3 OVERVIEW
The ISIS 3 radio telemetry hardware represents the first major redesign of the field
hardware for analog NBFM telemetry. The new RF telemetry equipment utilizes modified
Hamtronics radio equipment for receiving and transmitting the data from the various short
period monitoring sites.
All capacitors used in the circuitry are either mylar, ceramic or high temperature
electrolytic in order to maximize longevity of the circuitry. All pc board connections utilize gold
plated connectors to prevent interconnection problems due to oxidation.
The radio transmitters are modified to remove their pre-emphasis networks. An
external switching type high efficiency power supply provides power to the driver and final so
that the power output of the radio can be controlled.
The radio receivers are modified for low distortion in order to prevent intermodulation
between carriers. The receiver outputs are run through external bandwidth limiting filters prior
to multiplexing to minimize the accumulation of noise in the multiplexed signal.
All power, output signal and monitoring connections are made via a single round
shielded 10 conductor ribbon cable. Three preamplifier output signals, gain range signal, analog
ground, VCO carrier signals, received audio and composite transmit audio are made available
external to the canister for onsite system diagnostics.
Transient suppression on the power leads protects the radio and multiplexer
equipment.
The entire package is housed in a shielded polished stainless steel cylinder capped with
aluminum plugs and “o” ring seals for shielded watertight operation to a depth of 25 ft. The
system has been designed to fit into the top of a 4” thin wall PVC pipe borehole. In addition a 4”
PVC screw plug has been installed on all leads coming from the radio canister, in order to seal
the borehole containing the radios and sensors.
3
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
ISIS 3 RADIO SYSTEM SPECIFICATIONS
RADIO TRANSMITTER
Operating voltage: 12-14 VDC
Operating current: Approximately
70mA
@100mW
90mA
@200mW
110mA
@300mW
130mA
@400mW
150mA
@500mW
200mA
@750mW
250mA
@1000mW
Output Power: 100mW to approximately 1W
Frequency Range: 216-220 Mhz, 5 Khz channel spacing
Frequency Stability: ±2ppm (-30˚C to +60˚C)
Output Protection: short or open
Output Impedance: 50Ω
Spurious Outputs: -65 dB below carrier or better
Modulation Bandwidth: 300 – 3500 Hz
Modulation Linearity: 0.1% or better
Input Impedance: 1KΩ
Deviation Sensitivity: ±5Khz for 1V r.m.s. (2.83Vp-p)
Radio Receiver
Operating voltage: 12-14 VDC
Operating current: Approximately 40mA.
Operating Frequency: Factory programmable with 2 alternate frequencies
Channel Spacing: 5 Khz
Sensitivity: 0.25uV or better (12dB SINAD)
Audio Bandwidth: 300-3000Hz
Output Impedance: 8 Ω
Audio Output: 1Vr.m.s. for ± 5 KHz Deviation
Normal Modulation Bandwidth: ±5 KHz
Modulation Acceptance: ±10 KHz
Distortion: Less than 1.0% THD
Selectivity: 1st IF, 2 pole, 250Khz, 2nd IF, 6 pole, 30Khz
Image Rejection: 70dB or better
Frequency Stability: ±2ppm (-30˚C to +60˚C)
Output Multiplexer Card
Transmitter Variable Power Supply: 3-11 VDC
Output Multiplexer: 3 channel, individual adjustable weighting, adjustable output to 1Vrms.
Output Impedance: 100 Ω
4
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
Receiver Filter 1: 1.9KHz Low Pass, 7 pole, (For Low Group Frequencies)
Receiver Filter 2: 3.4Khz High Pass, 4 pole, 4.5KHz low pass 3 Pole(For High Group Frequencies)
Functional Block
Descriptions
Radio Receiver
The radio receiver
used in the ISIS 3 system
is
purchased
from
Hamtronics and modified
to
provide
proper
operation when used
with data telemetry
equipment.
The modifications
consist of removing very
narrow band IF filters and replacing them with broader band filters. Receiver de-emphasis
components are also removed because the companion transmitters do not employ preemphasis. The quadrature discriminator is also modified for wider bandwidth and lower
distortion. Additional modifications to the receivers internal low pass filter are required when
use of the three highest frequency carriers are anticipated.
Operating power for the radio receiver (s) is provided by the output multiplexer card
through an RF filter network from the power input. A single stage of transient suppression is
provided by the output multiplexer card.
The radio output signal and the filtered radio output signal are available at test points
on the output multiplexer card. The radio outputs are set to 1Vrms (2.828 Vp-p) output for a
single 1 KHz carrier deviation of ± 5 KHz during radio calibration.
Output Multiplexer Board
The output multiplexer
board is made in three different
versions. A transmitter only
version for outer ring ( low or
high group carriers) stations; a
repeater
version
for
multiplexing an inner (middle
group carriers) and outer ring
station (low group carriers) and
5
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
a non-standard repeater version for multiplexing two receivers (low and high group carriers)
with an inner group station. A schematic is provided for a completely loaded system. Unused
filter components are deleted from the other versions to save power and minimize cost.
Low Group Receiver Filter
If the ISIS-3 hardware is
ordered with a single receiver,
(for a repeater site), it is
assumed that this receiver will
provide a signal containing the
lowest three frequency carriers
for subsequent multiplexing
with the three middle carrier
frequencies. (A high carrier
group multiplexed with a
middle carrier group requires
that the received signal be
processed through a high group receiver filter, and this type of repeater will not contain a low
group filter.)
The receiver output signal (TP601) is routed through a bandwidth limiting filter prior to
multiplexing with locally generated carriers to minimize the accumulation of received radio
background noise. A 7th order low pass filter is provided to limit the bandwidth of the received
signal to only that required by the carriers received. The high frequency corner of this filter is
set at 1.9KHz. A 0.5dB Chebyshev filter is used to maximize out of band roll-off consistent with
minimal group delay distortion and flat response for in band signals. Each filter provides 0 dB of
gain within the pass band. A trimpot at the filter output (TP602) allows variable attenuation of
the signal prior to multiplexing.
This filtered and possibly attenuated radio output signal is also available for analysis on
a test jack on the ISIS 3 test box.
High Group Receiver Filter
If the ISIS-3 hardware is ordered with two receivers, (for a non-standard repeater site), it
is assumed that the first receiver will provide a signal containing the lowest three frequency
carriers for subsequent multiplexing with the three middle carrier frequencies. The second
receiver will provide the highest three carriers for subsequent multiplexing. Both receiver
output signals are routed through bandwidth limiting filters prior to multiplexing with locally
generated carriers to minimize the accumulation of received radio background noise in the
composite signal.
The low group signal will be connected to a low group filter as previously stated. The
high group (TP603) signal is processed differently. A combination of low and high pass filters are
utilized to band limit noise from the receiver. The high pass filter is a 4 th order filter at 3.4 KHz
6
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
and the low pass filter is a third order filter at 4.8 Khz. These filters also have a 0.5 dB
Chebyshev response.
This filter provides 0 dB of gain within the pass band. A trimpot at the filter output
allows variable attenuation of the signal (TP604) prior to multiplexing.
The filtered and possibly attenuated radio output signal is also available for analysis on a
test jack on the ISIS 3 test box.
Output Multiplexer
The output multiplexer combines by means of FDM the internally generated carriers
from the site with up to two signals from different receivers. The output of this multiplexer is
the composite modulation signal for the transmitter.
The locally generated signals from the ISIS 3 sensor package are brought into the
multiplexer through transformer T601, and then variable attenuation is provide to this signal by
trimpot R626. The output of this trimpot can be seen on the grey test point TP 605.
The multiplexer composite output signal is available on the white test point TP606 and
on a test jack on the ISIS 3 test box. The gain of the multiplexer can be set from 0.3 to 1.3 by
trimpot R632 and provides a means of adjusting the overall composite signal level that will
modulate the transmitter.
7
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
8
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
Transmitter
The radio transmitters used in the ISIS 3 system are purchased from Hamtronics and
subsequently modified to provide proper operation when used with data telemetry equipment.
The modifications consist of removing the de-emphasis components and the application of a
variable voltage to power the final stage. An additional modification supplies 12V power to the
pre-driver and driver stages. Additional modifications to the transmitters internal low pass filter
are required when use of the three highest frequency carriers are anticipated.
Operating power for the radio transmitter is provided by the output multiplexer card
directly from the fused power input. A single stage of transient suppression is provided by the
output multiplexer card. Power for the final is obtained from a switching regulator configured
around U604. The output of this regulator is between Vin-3.1 and 2VDC. Higher radio output
powers (at the expense of power regulation) may be obtained by removing the wht/org wire
from J604-1 and connecting it to J604-4. The transmitter may be completely powered down by
unplugging P604 from J604 in order to check for possible receiver desense in repeater
configurations.
The transmitter deviation sensitivity is set to 1Vrms (2.828 Vp-p) output for a single
carrier deviation of ± 5 KHz during radio calibration.
9
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
NOTE: Blue wire attachment point changed after photo was taken. Photo indicates variable
power to driver and final, not just final.
10
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
Radio Canister
The radios and multiplexer card are housed in a 4” diameter stainless steel cylinder with
aluminum end caps. This results in a totally shielded enclosure to minimize leakage of any
internally generated signals other than those on the transmitter cable. O-ring seals, screw seals
and cord seals are used to make the entire assembly waterproof to a depth of 25 ft. The o-rings
should be cleaned and re-greased any time the container is opened for service or adjustment.
The canister requires 6 small bags of desiccant and they should also be replaced any time the
equipment requires service.
The cable seals are installed on the inside of the enclosure to minimize corrosion
between the brass and aluminum. An epoxy seal is poured on the outside as a secondary seal
between the wires and the enclosure.
The
canister may be
opened
by
removing the seal
screw from the
bottom end of
the
package.
Remove
the
bottom cap and
unplug the 8 position cable plug from the header on the multiplexer PC board. The internal
assemblies may then be removed by gently pushing up on the end of the aluminum plate that
contains the clip nut until the upper O-ring clears the top of the cylinder.
Output Test Cable
A ten position round, shielded, ribbon cable connected to J605 on the output
multiplexer card carries the test and diagnostic signals from the ISIS 3 system to the external
test box. A separate ground lug has been provided for the cable shield connection.
11
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
Adjustments
Receiver Adjustment
Full instructions for receiver adjustment and troubleshooting can be found in Appendix
A which contains the Hamtronics documentation. In general, the receiver is adjusted like any
other NBFM receiver. The following is a short form of receiver adjustment.
The receiver can operate at one of three frequencies, the primary (as indicated on the
label) and 2 alternate frequencies that are selectable by jumper and given in the attached
calibration sheet. If a new frequency is selected, the VCO coil, L1 must be set to center the
range of the phase comparator error signal at approximately 2VDC at TP1.
Set the squelch adjustment on the receiver (R25) fully CCW. A low level signal with 1 KHz
modulating frequency and a deviation of ±5 Khz is injected into the input such that a SINAD
reading of approximately -12 dB is obtained. The input stages are then re-tuned for maximum
sensitivity. The input signal may be reduced further as needed during the alignment process.
Once maximum sensitivity is attained the input signal is adjusted for a SINAD reading of exactly
-12 dB. The rf output level from the test source at this point is equal to the sensitivity of the
receiver which should be in the range of .15 to .25µV.
NOTE: because of the wide band nature of the modified 1st IF filter, T1 and T2 tune
extremely broadly, and normally do not measurably affect the response of the receiver.
Set the signal generator to produce -80dBm signal with the modulation unchanged.
Connect a distortion analyzer to the receiver filter output on the output multiplexer card.
Retune the quadrature coil T3 for minimum distortion. If 1% or less distortion cannot be
attained, It is usually necessary to adjust the TCXO U3 slightly, and then retune the quadrature
coil. Repeat as needed to minimize distortion.
Finally, set the receiver output level to 1 Vrms at the receiver input TP on the output
multiplexer board using volume control R37 on the Hamtronics receiver board.
If receiver squelch is to be used with the receiver, set the RF signal generator to produce
a fully modulated 1 KHz signal at the desired RF squelch level. Set squelch adjustment R25 fully
CW. The receiver should now be squelched. (If not, select a lower RF squelch level). Slowly turn
squelch adjustment R25 CCW until the receiver output squelches. Increase the RF signal
generator output and verify that the receiver unsquelches.
Transmitter
Full instructions for transmitter adjustment and troubleshooting can be found in
Appendix B which contains the Hamtronics documentation. In general, the transmitter is
adjusted like any other NBFM transmitter. The following is a short form of transmitter
adjustment.
The transmitter is completely frequency agile within its band. Once a new frequency is
selected, the VCO coil L1 must be set to center the range of the phase comparator error
correction signal, to approximately 2VDC at TP1.
12
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
R632 (power adjustment) on the output multiplexer board should be set fully CCW. The
RF circuits of the transmitter are then adjusted for maximum power output. Once all
adjustments are complete, final power output adjustment should be made by adjusting R632
CW to decrease radio output power until the desired power output is obtained. L5, L8 and C44
may be slightly retuned to increase the power output at this level and then R632 adjusted
further CW to return to the desired power output. This will maximize the efficiency of the final
at the desired output power level.
Finally, the deviation adjustment R35 is set fully CW. Adjust af gain pot R26 so that a 1
KHz, 1 Vrms signal provides ± 5 KHz of deviation. This will also automatically set the limiter.
Transmitter Multiplexer Adjustment
Adjustment of the multiplexer is slightly complicated by the fact that one of the carriers
has AM modulation applied to it to convey the gain range information. The increase in
amplitude of this one carrier must be accounted for in order to avoid limiting in the transmitter
and distortion in the radio system that would increase during gain range events.
Adjustment can be done with either an oscilloscope (p-p signal) or true rms voltmeter.
Once the VCO carriers are stabilized, the oscilloscope method can be difficult to implement
because the carriers are phase locked and harmonically related to one another. This
relationship may tend to obscure the peaks of the waveform during the measurement interval.
The rms method does not suffer from this drawback.
In any case, the positive or negative peak of the modulation signal cannot exceed
1.414Vp, or peak limiting in the transmitter will occur leading to serious distortion. In reality,
we will only use 95% (1.343Vp) of the available 5KHz (4.75 KHz) deviation so that a small safety
factor is built in to the system. A math cad spread sheet is supplied indicating how the
modulation voltage values were calculated.
Outer Ring Site, (non repeater)
In this case there are only three carriers involved. Set the local level trimpot, R626, fully
CW. Each locally generated VCO carrier is normally 1Vp-p in amplitude and the input
multiplexer will add them together to create an approximately 3Vp-p, (866mVrms), signal at
test point TP605. The actual modulation voltage will be set using the composite gain
adjustment, R632.
Using the values determined from the spreadsheet, set R632 to produce a voltage of
411 mVrms, (2.015Vp-p), at test point TP606. Then shake the sensor stack; the voltage at TP606
should increase to 582 mVrms. Careful observation of this waveform will indicate a voltage of
2.687 Vp-p. This is all that is required to properly set the transmitter modulation. Note that the
modulation meters in most service monitors are average reading devices and thus will indicate
significantly less than the 4.75 Khz peak deviation expected.
13
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
Inner Ring Site, (repeater single receiver)
In this case, the three locally generated carriers are multiplexed with three remote site
carriers from the radio receiver. The same concerns about limiting in the transmitter are
addressed.
In the first step, the local carriers are slightly attenuated to keep from overdriving the
output multiplexer. Adjust the local level adjustment R626 to produce a 250 mVrms signal at
test point TP605. (Make sure that the gain range circuit is not activated during this
adjustment!)
In the next adjustment, the received VCO carriers will be equalized to the locally
generated VCO carriers. Adjust the low group level trimpot , R609 to produce 250 mVrms at
test point TP602. (Make sure that the gain range circuit is not activated during this
adjustment!)
The absolute values of the previous two adjustments are not critical, but both levels
should be equal, so that the remotely generated carriers are equal in amplitude to the locally
generated carriers in the composite signal applied to the transmitter.
Finally, adjust output level trimpot, R632, to produce a signal of 291 mVrms at test point
TP606. (Make sure that none of the gain range circuits are activated during this adjustment!)
This signal amplitude will insure that when both ISIS 3 systems are operating in gain ranging
mode, the transmitter will not be over modulated. The modulation voltage will increase to 411
mVrms when both systems are in gain ranging mode. This is all that is required to properly set
the transmitter modulation in this case. Note that the modulation meters in most service
monitors are average reading devices and thus will indicate significantly less than the 4.75 Khz
peak deviation expected.
14
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
15
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
16
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.
17
Copyright disclaimer:
This manual may be copied in full or in part by the equipment owner or user without written permission
from the manufacturer. VLF Designs retains the right to make improvements or changes in the
equipment design as needed. If any additional information is required by the equipment user, please
contact VLF Designs by phone or email.