gd sdr automatic gain control characterization …...july 20, 2012 • installed on iss august 7,...

National Aeronautics and Space Administration

www.nasa.gov

GD SDR Automatic Gain Control

Characterization Testing

Jennifer Nappier

NASA Glenn Research Center, Cleveland, Ohio

Co-Author: Janette Briones

NASA Glenn Research Center, Cleveland, Ohio

SDR-WInnComm

January 2013

https://ntrs.nasa.gov/search.jsp?R=20130010499 2020-07-29T16:16:50+00:00Z


www.nasa.gov

Presentation Contents

2

• SCaN Testbed Overview

• GD SDR Description

• AGC Characterization Test Objectives

• Test Setup

• Test Results

• Useful Applications of the AGC Characterization

Testing Data

• Recommendations


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SCaN Testbed Flight System Overview

3

• 2 S-band SDRs

• 1 Ka-band SDR

• Ka-band TWTA

• S-band switch network

• Antennas

– 2 - low gain S-band

antennas

– 1 - L-band GPS antenna

– Medium gain S-band and

Ka-band antenna on

antenna pointing

subsystem.

• Antenna pointing system

• Flight Computer/Avionics

• Launched on Japanese HTV-3 on

July 20, 2012

• Installed on ISS August 7, 2012

• Checkout and Commissioning is in

progress


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• TDRSS S-band Transponder

– 8 Forward link receive waveform configurations

– 30 Return link transmit waveform configurations

• 1 Xilinx Virtex II QPro FPGA, 3 M gate

• ColdFire microprocessor with VxWorks RTOS running the Space

Telecommunications Radio System (STRS) Architecture

SCaN Testbed GD SDR Description

Waveform

Number

Center

Frequency

Data Rate

(kbps)

Forward

Error

Correction

1 SA 18 Coded

2 SA 18 Uncoded

3 SA 72 Coded

4 SA 72 Uncoded

5 MA 18 Coded

6 MA 18 Uncoded

7 MA 72 Coded

8 MA 72 Uncoded

• CRAM (Chalcogenide

RAM) Memory (4 Mb)

• Analog (10 MHz filter

bandwidth) and Digital

(6 MHz filter

bandwidth) automatic

gain controls (AGCs)


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Test Objective and Plan • Characterize the relationship

between:

– SDR input power

– SDR baseplate temperature

– Waveform configuration

– The digital and analog AGC

values

• Temperature range:

– -15 to +45 °C

• SDR input power range:

– -90 to -130 dBm

5

• Results will be used to estimate SDR input power in future testing

• Testing phases included:

– GD verification testing

– GRC thermal vacuum (TVAC) testing

– GRC verification testing

SCaN Testbed during TVAC testing, March 2011


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GRC Test Setup

• S-Band TDRSS Simulator (TSIM) was

used to emulate the forward link

waveform

• TSIM was connected to the SCaN

Testbed using a test equipment

interface circuit and RF cable

• SDR input power was measured from

a coupled port in the interface circuit

using a power meter

• The RF subsystem inside the SCaN

Testbed was used to connect an

antenna port to the GD SDR

• During TVAC, the RF cable and SCaN

Testbed were located in the vacuum

chamber

6

S-Band TDRSS Simulator

Forward Link

Waveform

Var Att.

Tx

Test Equipment Interface Circuit

80 dB

Attenuator

CouplerPower

Meter

SCAN Testbed

RF

Subsystem

GD SDR

RF Tx RF Rx

GRC Test Setup


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AGC Characterization Results at Ambient Temperature

Analog AGC at 26 °C Digital AGC at 26 °C

7

100

110

120

130

140

150

160

-130 -120 -110 -100 -90 -80

An

alo

g A

GC

Val

ue

SDR Input Power (dBm)

18k, Uncoded, SA

18k, Coded, SA

72k, Coded, SA

72k, Uncoded, SA

18k, Coded, MA

18k, Uncoded, MA

72k, Coded, MA

72k, Uncoded, MA

0

50

100

150

200

250

-130 -120 -110 -100 -90 -80D

igit

al A

GC

Val

ue


18k, Uncoded, SA

18k, Uncoded, MA

18k, Coded, SA

18k, Coded, MA

72k, Coded, SA

72k, Coded, MA

72k, Uncoded, SA

72k, Uncoded, MA

• Analog AGC varies with center frequency (MA/SA)

• Digital AGC varies with symbol rate (coding + data rate)


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AGC Characterization Results over Temperature

Analog AGC Digital AGC

8

60

80

100

120

140

160

180

200

-125 -120 -115 -110 -105 -100 -95 -90

An

alo

g A

GC

Val

ue


60 deg C

48 deg C

39 deg C

33 deg C

26 deg C

21 deg C

-7 deg C

-8 deg C

-20 deg C

0

20

40

60

80

100

120

140

160

-125 -120 -115 -110 -105 -100 -95 -90

Dig

ital

AG

C V

alu

eSDR Input Power (dBm)

60 deg C

48 deg C

39 deg C

33 deg C

26 deg C

21 deg C

-7 deg C

-8 deg C

-20 deg C

• Both analog and digital AGCs vary over temperature.

The analog AGC variation is more significant.


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Sources of Error in Data Collection

• Differences in the

GD and GRC test

setup (+/-.5 dB)

• Compensation

method for the cable

loss over

temperature during

thermal vacuum

testing (+/-.5 dB)

9

• Data interpolated for waveforms with incomplete

data sets (+/- 1 dB)

• System loss measurement error (+/-.3 dB)


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SDR Input Power Estimation using Digital AGC

10

• The Digital AGC characterization

data was used estimate the SDR

input power during operations on

ISS (note: predicted power is

TBD)

• The Eb/No was

calculated from the

SDR input power and

used to create a BER

curve


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Estimation of Interferer Signal Strength using Digital AGC

11

• Digital AGC shows received

power is higher than expected

due to an interferer

• The purple curve was plotted with

the Eb/No calculated from a

measured power.

• The green curve was plotted with

the Eb/No calculated from the

digital AGC


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Recommendations and Forward Work

Recommendations

• Plan test phases and

design a test setup that

can be kept constant

throughout each phase

• Balance SDR

reconfigurable

parameters with project

test time

Forward Work

• 3 SDR input power

estimation algorithms

have been developed

• Characterize the SDR

input power algorithms

during on-orbit operations

on ISS

• Utilize the engineering

model (EM)

characterization data to

create SDR input power

estimators for the EM 12


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Questions?

[email protected]

216-433-6521

13

gd sdr automatic gain control characterization …...july 20, 2012 • installed on iss august 7,...

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