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Instrumentation Receiver:
Analog Signal Processing for a DSP World
Rick Campbell
Portland State University
Tonight’s Talk discusses 3 questions:
What is an Instrumentation Receiver?
How does Rick design one?
What is it good for?
An Instrumentation Receiver is a general purposeRF-analog front-end that connects between an antenna or microwave downconverter and audio frequency range signal processing electronics.
Digital Storage OscilloscopeAudio Spectrum AnalyzerAnalog VoltmeterBaseband Digital Signal ProcessorHeadphonesStereo HeadphonesAudio Power AmplifierArray ProcessorWideband Transmogrifier Filter
Part 1: What is an Instrumentation Receiver?
The output signal might be connected to:
Modern Receiver Design:
Meets specs for specific applicationHigh VolumeHighly manufacturableLowest CostSmallestHighly integrated
Example: typical microwave radio chip
2 dB Noise Figure2.4 GHz to 2.5 GHz input-10 dBm input third order interceptintegrated demodulator--digital outputbuilt in a TSMC RF CMOS processspecified die area
How is it different from a modern wireless receiver?
But an Instrumentation Receiver performs some simple math:
si(t) = a(t){cos[2pfot + j(t)]} + noise
RF input:
...and you very specifically have no idea what it will be used for
so(t) = ga(t){cos[2pf1t + j(t)]} + more noise
baseband output:
where:
f0 - f1 = fLO g = gainmore noise
noisenoisefigure
_________ =
If we knew the application ahead of time, we could minimize current, move many functions into DSP on some other part of the CMOS die, build 100 million parts that only do one thing.
But: to foster Innovation, the Bell Labs stockroom in 1975 was full of useful parts, not ASICs:
transistors, transformers, diodes, capacitors, resistors, motors, photocells, microphones, switches, batteries, op-amps, mixers, inductors, quartz crystals...
These are the basic components creative designers use to do science experiments, test new ideas for next generation tech-nology, and inspire next-generation innovators. We don’t know how they will be used when we design them.
It’s like a microphone with a built-in preamp, an antennainstead of a pressure transducer, and a frequency conversion inside. The output is identical to a microphone output.
So my working definition of an Instrumention Receiver is that it is a block in a system:
Instrumentation Receiver
RF in
Audio out
LO in
My Lab Instrumentation Receiver:
Racal RA6790/gm
Works great, but too big, too heavy, and too expensive for many applications.
My Lab Instrumentation Microphone:
Bruel & Kjaer 4006
Works great...too big and expensive for many applications. NASA uses Knowles Acoustics elements on Mars Rover
Part 2: How does Rick Design One?
pages 60-61 notebook number 124
Start with pen and paper--not the simulator!
Then test the ideas at the bench. Use scale models for mm-wave circuits.
Stuff on my bench for measurements:
precision attenuators
wideband gain blocks
narrow filters
isolators
Some measurement wisdom: Precision loss is a good thing. Reverse isolation is a very good thing. Amplifiers should be flat and have headroom. Filters should have flat tops and graceful skirts. Connections to the outside world should have well-de-fined impedance and nothing unsavory leaking out.
simple things that I understand
Measurement tools are both simpler and more refined than commercial products--like a fixed gear bicycle.
My specs for an instrumentation receiver:
Input S11 < 10 dB from 2 to 250 MHz4.0 dB noise figure (makes calculations easy)60.0 dB gain: 1.0 microvolt in = 1.0 millivolt out
100 Hz to 20 kHz output bandwidth (like microphone)
little box with SMA RF in, SMA LO in, RCA audio out
5% wide Input band anywhere between 2 - 250 MHz
2 volt peak-to-peak output into 600 ohms
It connects to anything I would connect a microphone to
40 dB adjacent channel interference suppression
>>40 dB everywhere else
First: design, build, and measure each subcircuit:
Then combine into PC board system:
First Pass functional
Second Pass meet specs
Third Pass limited production run
Here’s the circuit board--the size of a business card
The top half is the RF Signal Processor and the bottom half is the Analog Signal Processor. This one works at 10 MHz RF.
Even at 10 MHz using chip components improves RF circuit performance by reducing stray electromagnetic coupling
The top half is the RF Signal Processor
+m
22
10n
15p 22
+m10n 10n
10n
10n
10n
22
220220
1p
20p 20p
1p
20p 20p
100k
15051
100k
15051
L1 L2 L3 L4 L5L6
L7
L8
33p
5p
15p
20p
U2
U1
51
22p
LNA bandpass amplifier-isolator image-reject mixer
I out
Q out
LO inRF in
Lots of subtle generalizations: A generalization is like an optimization, except it achieves a global, shallow minimum rather than focusing on one parameter.
Open-Design: everything is published, no hidden parts
The bottom half is the Analog Signal Processor
a
b1.87k 115k
10.0n 10.0n11.8k
10.0n
20
33u
470
470
I
10.0k
487 30.1k
10.0n 10.0n4.81k
10.0n
1.5k
33u
10u10k
100k
100k27k
220n
3.0k
3.9k
24
10u
20
Q1.5k
33u
10u10k
100k
100k27k
220n
3.0k
3.9k
24
10u
f
s2
s1
10.0k
10.0k
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10k
10.0k
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27k
3.9k
10.0k
470 33u
220n
10n
LNA
LNA
all-pass
all-pass
sum line out
Many generalizations.....
I in
Q in
Frequency Response and Opposite Sideband Suppression
passband phase
flat passband
50.1 MHz Instrumentation Receiver with VHFs LO
50.1 MHz Instrumentation Receiver with VHFs LO
Part 3: What is it used for?
Most important answer is: use your imagination!
But here are some examples to start you thinking...
100 nV 50.110 MHz sine wave
Two-tone Third Order products at 50 MHz
Tone spacing 72 Hz
Electromagnetic Sensor Array with Baseband Combiner
instrumentation receiver
ant
enna
el
emen
t
Local Oscillator
BasebandProcessor
instrumentation receiver
ant
enna
el
emen
t
instrumentation receiver
ant
enna
el
emen
tinstrumentation receiver
ant
enna
el
emen
t
Physics-Based Noise Figure Measurements
instrumentation receiver
Local Oscillator
Audio Voltmeter
100
ohm
re
sist
or
liquidnitrogen
Integrated Vector Network Analyser
instrumentation receiver
Local OscillatorDigital Storage Oscilloscope
instrumentation receiver
Signal Generator
Cartesian Feedback System
instrumentation receiver
Local OscillatorCompare
instrumentation receiver
Modulated signal
predistortion
VHF Sonobouy Receiver
instrumentation receiver
Local Oscillator
Audio Recorder
Moose Tracking
instrumentation receiver
Local Oscillator
Audio Recorder
Monopulse Modulated Scatterer Radar IF
......but that’s the subject of my next talk.
Thank you and good evening.
These slides will be posted on:
ece.pdx.edu/~campbell