instrumentation receiver: analog signal processing for a dsp...

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

10.0k

10k

10.0k

10.0k

10.0k

10.0k

10.0k

10.0k

10.0k

10.0k

10.0k

10.0k

10.0k

10.0k

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

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


ant

enna

el

emen

t


ant

enna

el

emen

tinstrumentation receiver

ant

enna

el

emen

t

Physics-Based Noise Figure Measurements


Local Oscillator

Audio Voltmeter

100

ohm

re

sist

or

liquidnitrogen

Integrated Vector Network Analyser


Local OscillatorDigital Storage Oscilloscope


Signal Generator

Cartesian Feedback System


Local OscillatorCompare


Modulated signal

predistortion

VHF Sonobouy Receiver


Local Oscillator

Audio Recorder

Moose Tracking


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

instrumentation receiver: analog signal processing for a dsp...

Documents