Remote Station User’s Guide 

by John T. Clark 

ARL-TR-4449 May 2008 

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Army Research Laboratory 

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ARL-TR-4449 May 2008 

Remote Station User’s Guide 

John T. Clark 

Sensors and Electron Devices Directorate, ARL 

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Remote Station User’s Guide 

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John T. Clark 

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U.S. Army Research Laboratory 

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13. SUPPLEMENTARY NOTES 

14. ABSTRACT 

A transmitter that responds to an input signal (transponder) has been designed at the Ka Band frequency range. The 

transponder is further enhanced to simulate a moving target by returning a signal with an artificial Doppler frequency and 

power level commensurate with that of a particular Radar Cross Section (RCS). The RF architecture is described first, 

followed by a detailed derivation of simulated RCS and then a complete step by step operational instruction is provided. 

15. SUBJECT TERMS

Moving target simulator, transponder, simulated RCS 

16. SECURITY CLASSIFICATION OF:

19a. NAME OF RESPONSIBLE PERSON

John T. Clark 

a. REPORT 

U 

b. ABSTRACT 

U 

c. THIS PAGE 

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OF ABSTRACT 

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OF PAGES 

30 19b. TELEPHONE NUMBER (Include area code) 

301-394-3800 

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18 
iii 

Contents 

List of Figures iv

List of Tables iv

Acknowledgments v

Introduction 1

RF Architecture 1

Derivation of Simulated Radar Cross Section 3

Operating Instructions 7

Conclusion 18

Appendix 19 

Distribution List 21 
iv 

List of Figures 

Figure 1. Remote station (RS) schematic diagram. ........................................................................2 

Figure 2. Radar and remote station (RS) setup...............................................................................3 

Figure 3. Measured gain of remote station. ....................................................................................6 

Figure 4. Remote station in transit/storage state.............................................................................8 

Figure 5. Field test setup to determine minimum range. ................................................................9 

Figure 6. (a) Frontal view of the RS (b) rear view of the RS. ......................................................11 

Figure 7. Remote station aiming plate. .........................................................................................12 

Figure 8. RF deck with aiming plate connections in place...........................................................13 

Figure 9. Remote station laptop critical items. .............................................................................14

Figure 10. RS-232 interface attachment. ......................................................................................14 

Figure 11. Screenshot of RS laptop desktop.................................................................................15 

Figure 12. Screenshot of full control VI. ......................................................................................16 

Figure 13. Screenshot of fd setting sent to SBC (and DDS)..........................................................17 

List of Tables 

Table 1. Maximum simulated RCS for selected frequencies..........................................................7 
v 

Acknowledgments 

The author acknowledges the technical contributions of David Hutchins, Russell Harris, Arthur 

Harrison, and Ronald Wellman of the Millimeter Wave Branch of the Army Research 

Laboratory without whom this work would not have been possible. 
vi 

INTENTIONALLY LEFT BLANK
1 

Introduction 

The Millimeter Wave Branch of the Army Research Laboratory has developed a Remote Station 

(RS) that operates in a portion (33.2 GHz to 36.4 GHz) of the Ka Frequency Band to be used as a 

transponder (transmitter-responder) to simulate radar target returns with the following attributes: 

Radar Cross Section (RCS) and Doppler Frequency Shift. The Doppler Shift settings are 

controlled by a single board computer (SBC) which is resident in the RS. The user interfaces 

with the SBC via a standard laptop serial (RS-232) interface. Simulated RCS is determined by 

the setting of a manual (rotary knob) variable attenuator. This guide will describe in detail the 

operation and procedures for configuration of the RS. 

RF Architecture 

The schematic diagram of the RS is shown in figure 1. Note that several power dividers are in 

place with only one output in use. This signifies legacy hardware that is no longer in use but 

remains present to maintain proper power levels. There are two sections, the Local Oscillator 

(LO) Section and the Radio Frequency (RF) Section as shown in figure 1. 

The LO Section starts with the master oscillator (an oven controlled 400 MHz crystal oscillator). 

As shown in the schematic, this signal is manipulated to obtain a 2.8 GHz signal and a 200 MHz 

reference. The reference is used by a Direct Digital Synthesizer (DDS) which produces output 

signals ranging from DC to 1 MHz in both In-Phase (I) and Quadrature-Phase (Q) outputs. The 

DDS is controlled by a resident SBC which the user interfaces with via a standard RS-232 serial 

interface. Details of this control interface will be provided later. The DDS output represents the 

synthetic Doppler offset frequency (fd) the RS is to emulate. The DDS I&Q outputs are sent to a 

single sideband modulator where they are added onto the previously mentioned 2.8 GHz carrier 

(this modulator output is denoted LO#2). An unadulterated version of the 2.8 GHz carrier is also 

available (this pure carrier is denoted LO#1). Thus, the LO Section has synthesized the two LO 

signals needed by the RF Section: (1) 2.8 GHz and (2) 2.8 GHz+ fd. The user determines the 

value of fd as discussed later. 

The RS is a transponder which indicates that it will not transmit a signal unless it has received 

one in the appropriate frequency and power range. Filters shown in figure 1 effectively limit the 

acceptable bandwidth to 33.2 GHz to 36.4 GHz. As with any RF system, there are non-linear 

devices in use which exhibit power compression. These devices will exhibit a 1 dB gain 

decrease (or 1 dB conversion loss increase) when certain power levels are met or exceeded. 

Operation in this region is not desired since signal distortion may occur as well as an inadvertent 

lowering of system gain which will alter the simulated RCS. Compression measurements have 
2 

been performed on the RS for this frequency band, revealing that the input power level should be 

less than –35 dBm to prevent power compression. 

Figure 1. Remote station (RS) schematic diagram. 

To facilitate aiming of the RS input to a remote radiation source, some front-end hardware has 

been relocated to an aiming plate. This plate is denoted in figure 1 as the items enclosed by the 

rectangle. After reception of a radiation source by the standard gain horn antenna (G~19.8 dBi), 

the received signal is amplified and sent via coaxial cable to the main RS assembly where it is 

up-converted (by LO#1 of 2.8 GHz) to 36 GHz to 39.2 GHz. This Intermediate Frequency (IF) 

is then down-converted (by LO#2 of 2.8 GHz +fd) back to 36 GHz to 39.2 GHz minus the 

Doppler shift (the “minus” shift is the result of performing a down-conversion on the signal). 

This Doppler sign represents a closing target. Finally, this signal is transported back to the 

aiming plate via coaxial cables where it is amplified and presented to a manual variable 

attenuator (AT3) which will determine the value of simulated RCS. The next section will 

describe in detail how AT3 is utilized in the determination of simulated RCS. 

Q

I

AT3 (RCS ATTENUATOR)

MANUAL (ROTARY KNOB)

RANGE 0 -50 dB (IL=0.8 dB [SET AT ZERO]) Modulator Output

2.8 GHz +fd

DDS Output

DC<fd<1 MHz DC Ampliifers

G=3dB Nominal

DDS

MOD

L1

(har. gen.)

IL=3 dB

IL=10.6 dB

IL=13.8 dB

IL=10.1 dB

IL=3.8 dB

NOTES:

1. SEVERAL DISCONNECTED COMPONENTS

REMAIN PRESENT (FIBER OPTIC DELAY

LINE, COMMUNICATIONS INTERFACE HAWRDWARE). 

 ALL INPUTS/OUTPUTS ARE TERMINATED IN A MATCHED LOAD.

2. THE STATE OF THE DDS IS CONTROLLED BY THE SINGLE 

BOARD COMPUTER WHICH IS INTERFACED 

VIA THE RS-232 PORT OF THE LAPTOP.

IL=12 dB

IL=12 dB

IL=6 dB

IL=3 dB IL=6 dB

IL=3 dB

IL=6 dB

A30

G= 30.8 dB

P= 13.9 dBm

NF=6 dB

A29

G=21.5 dB

P=+13.4 dBm

NF=5 dB

A28

G=23.7 dB

P=+10 dBm

NF=4 dB

A8

G=16 dB

P=+24.0 dBm

NF=5.5 dB

A10

G=22.5 dB

P=+20 dBm

NF=5.0 dB

A3

G=23.4 dB

P=+11 dBm

NF=6 dB

A4

G=29.2 dB

P=+8.0 dBm

NF=3.5

A13 A24

A9

G=26 dB

P=+20 dBm

NF=3 dB

A25

G=22.5 dB

P=+20 dBm

NF=5 dB

A7

G=11 dB

P=+22.5 dBm

NF=6.0 dB

F26

CF=2.84 GHz

BW=2 GHz

F21

CF=180 MHz

BW=60 MHz

F25

FC=38 GHz

BW=4 GHz

IL= 4.1 dB

F9

CF=2 GHz

BW=10 MHz

F5

CF=2.02 GHz

BW=100 MHz

AIMING PLATE

F3

FC=34.8 GHz

BW=3.2 GHz

IL= 3.6 dB F8

CF=250 MHz

BW=150 MHz

F7

CF=2.8 GHz

BW=10 MHz

F19 (LPF)

FCO=3 GHz

F6

CF=800 MHz

BW=40 MHz

F4

CF=400 MHz

TRANSMIT 

PORT

f= 33.2 GHz to 36.4 GHz

P=Pr+45 dB-AT3 SETTING

RECEIVE PORT

f=33.2 GHz to 37.2 GHz

P=Pr

TRANSMIT 

HORN

G=19.6 dBi (avg)

RECEIVE

HORN

G=19.6 dBi (avg)

M9

CL=10 dB 

I R

M3

CL=14.4 dB 

M6

CL=11.75 dB

R I

R I

S2

IL=4 dB

S4

IL=7.5 dB

DA=0.4 dB

S3

IL=4 dB

S13

IL=4 dB S14

IL=3.8 dB

DA=0.3 dB

FM1

Fin=400 MHz

Fout=800 MHz

O1

f=400 MHz

P=+14 dBm 

f/4 FD1

fin=800 MHz

fout=200 MHz

CP2

IL=1 dB

CPL=10 dB

MFRF REMOTE STATION 071017 JTC/RJW

LENGTH=6'

IL= 6.2 dB

LENGTH=6'

IL= 4.4 dB

RF-RX

RF IF

RF-TX

IF RF

2

3 Ref

1

2

3

1

2

1

Ref

DIV LO SECTION

RF 

SECTION 
3 

Derivation of Simulated Radar Cross Section 

In this section, a derivation of the expression for simulated RCS as a function of wavelength, RS 

antenna gain and system (RF) gain of the RS will be performed. As discussed above, the input 

power into the RF Section (after reception by the RS Receive Antenna) should be less than 

–35 dBm. Failure to limit the power level in this manner will compress the RS Gain and thus 

alter the simulated RCS as described below. The user should calculate an expected input power 

level as given by equation 2 below which is a function of source power, source transmit antenna 

gain, the range between the source and the RS and the Gain of the RS Receive Antenna. This 

value should not exceed the maximum input power of the RS which is less than or equal to 

–35 dBm. Refer to the Operating Instructions section for detailed instructions on calculating a 

safe minimum distance between the RS and the user’s radiation source. 

Consider the case shown in figure 2, where a radar system generates a Power level, Pt, which is 

presented to a directive transmit antenna with Gain, Gt. 

Figure 2. Radar and remote station (RS) setup. 

The radiated power density, Prad, is given by equation 1. 

2 4 R

PG P t t

rad

π = (W/m2

) (1) 

RADAR 

With 

Transmit 

Power 

Pt 

RS 

With 

Gain 

Range GRS 

 R 

Transmit 

Antenna 

Gt, Aet

Receive 

Antenna 

Gr, Aer

Transmit 

Antenna 

Gtx, Aetx

Receive 

Antenna 

Grx, Aerx

2 4 R

PG P t t

rad

π =

35 (max) 4 2 dBm

R

PG A

P t t erx

in = = − π

2 2 4 t

t t erx RS

out P

R

PG A G P = = π

2

2

2 4 R

P G P t tx

rad

π =

2

2

4 R

P G A

P t tx er

r π =
4 

This radiated power is received by the RS receiver antenna’s effective aperture, Aerx, and it is the 

input power, Pin, to the RS, given by equation 2. Recall that this value must not exceed 

–35 dBm. 

2 4 R

PG A

P t t erx

in

π = (W) (2) 

This signal’s power is increased by the gain of the RS, GRS, and is given by equation 3. 

2 2 4 t

t t erx RS

out in RS P

R

PG A G P = P G = = π

 (W) (3) 

This signal is now presented to the RS Transmit Antenna and is denoted for convenience as Pt2. 

Just as in equation 1, another radiated power density (denoted as Prad2) is created, in this case via 

the RS transmit antenna, which has a gain, Gtx , as in equation 4. 

2

2

2 4 R

P G P t tx

rad

π = (W/m2

) (4) 

Finally, Prad2 is received through the radar’s receive antenna’s effective aperture, Aer, and listed 

as a received power, Pr, as in equation 5. 

2 2 2

2

4 (4 R )

PG A G G A

R

P G A

P t tx er t t erx tx RS er

r π π = = (W) (5) 

Now consider a true target at a distance R, using the same radar system as in figure 1, with an 

RCS, σ. Skolnik1 derives the power received from such a target as in equation 6. 

2 2 (4 R )

PG A

P t t er

r π

σ = (W) (6) 

Setting equations 5 and 6 equal to each other, as in equation 7a, we can solve for σ as in equation 

7b after common terms are removed. 

2 2 2

2

4 (4 R )

PG A G G A

R

P G A

P t tx er t t erx tx RS er

r π π = = = 2 2 (4 R )

PG A

P t t er

r π

σ = (W) (7a) 

σ = AerxGtxGRS (m2) (7b) 

Equation 7b shows that simulated RCS only depends on the gain of the RS, the gain of the RS 

transmit antenna and the effective aperture of the RS receive antenna. Thus, it is independent of 

radar transmitter power, range or type of antennae used at the radar. It is implicitly dependent on 

the frequency just as true RCS is (since antenna gain and effective aperture are functions of 

wavelength). As mentioned above, GRS will be less than expected if the input power is equal to 

or greater than –35 dBm. 

 1Skolnik, M. I., Introduction to Radar Systems, p. 4, McGraw Hill, 1980. 
5 

If the two RS antennae are identical (which is usually the case), equation 7b can be rewritten as 

2

4 ⎟

⎠

⎞ ⎜

⎝

⎛ = λ

σ π eRS

RS

A G (m2 ) (8a) 

 or ( )2

_ 4

λ

π

σ RS ANT

RS G G= (m2

) (8b) 

where GRS_ANT and AeRS are the gain and effective aperture of the identical transponder antennae 

respectively, since2

2

4

λ

Ae π G = (9) 

As an example, consider the RS with a gain of 45.5 dB (Pin=–40 dBm) which uses two identical 

horn antennae with a gain of 19.5 dBi at 33.575 GHz. The calculation of simulated RCS is as 

follows: 

m

Hz

m s

f

c 3

9

8

8.94*10

33.575*10

3*10 / − λ = = = 19.5 89.1:1

45.5 35,481.3 :1

_ = =

= =

G dBi

G dB

RS ANT

RS

( ) 89.1:1*8.94*10 m 1,790.6 m 32.53 dBsm

4

35,481.3 :1 2 2 3 = = = + −

π

σ .

This is the maximum RCS that can be simulated by the RS and corresponds to the manual 

variable attenuator (RS AT3) being set to 0 dB. The RCS Attenuator has calibrated attenuation 

values between 0 and 50 dB therefore the calibrated RCS can range from the above mentioned 

maximum value of +32.73 dBsm to –17.27 dBsm (for f=33.575 GHz). There is also an 

uncalibrated region between 50 dB past a point denoted “MAX” to a hard stop where AT3 

delivers even more attenuation than 50 dB. It should be noted that once the setting of AT3 

exceeds the RS Gain of 45.5 dB the overall noise figure of the RS will be more directly degraded 

by the setting of AT3. 

It is important to note that the RCS will vary with frequency. A natural target will exhibit an 

increase in RCS with an increase in frequency. However, our synthetic target differs from this 

phenomenon. This deviation is due to the fact that the RF Gain of the RS is not constant with 

respect to frequency nor is it monotonic. Figure 3 is a plot of the RS Gain versus frequency 

measured by the author on 10/15/07 using a Wiltron 32796A Vector Network Analyzer. 

Appendix A lists the data points for this plot (data collected every 20 MHz). 

 2Skolnik, M. I., Introduction to Radar Systems, p. 4, McGraw Hill, 1980. 
6 

16

21

26

31

36

41

46

51

56

33 33.5 34 34.5 35 35.5 36 36.5 37

Frequency (GHz)

|S21 | (dB)

Figure 3. Measured gain of remote station. 

To illustrate the variation of simulated RCS due to RS Gain ripple, the above example is 

repeated for an operating frequency of 34.7 GHz where the gain of the RS antennae have 

increased to19.8 dBi and the RS Gain has increased to 48.8 dB: 

m

Hz

m s

f

c 3

9

8

8.65*10

34.7 *10

3*10 / − λ = = = 19.8 95.5 :1

48.8 75,857.76 :1

_ = =

= =

G dBi

G dB

RS ANT

RS

( ) 95.5 :1*8.65*10 m 4,115 m 36.14 dBsm

4

75,857.76 :1 2 2 3 = = = + −

π

σ

Note that this simulated RCS varies by 3.61 dB from the previous example. The gain has 

increased by 3.3 dB which shows that for a constant gain, the simulated RCS would have only 

increased by 0.31 dB (similar to the natural increase of a “true” target). 

Table 1 lists the parameters used in equation 8b to calculate maximum simulated RCS for 

selected frequencies of interest. This maximum value is achieved when AT3 is set to an 

attenuation value of 0 dB. The change in simulated RCS is directly proportional to RS Gain as 

shown in equation 8b, which implies that for every dB increase in the attenuation value of AT3 

(which is a dB decrease in GRS) there is a corresponding dB decrease in simulated RCS. For 

example, if the user desires to simulate +10 dBsm at 33.575 GHz, GRS must be reduced by 

22.53 dB (=32.53-10) which is accomplished by setting AT3 to 22.53 dB (such precision is not 

possible so a setting of 22.5 dB would have to suffice). 
7 

Table 1. Maximum simulated RCS for selected frequencies. 

Frequency (GHz) λ (mm) GRS_ANT (dBi)* GRS (dB) σMAX (dBsm) 

33.575 8.94 19.5 45.5 32.53 

34.7 8.65 19.8 48.8 36.14 

35.825 8.37 20.1 46.3 33.96 

*Accuracy of Antenna Gain Measurements is limited to ±0.5 dB due to alignment errors and tolerance of 

Calibrated Gain (Reference) Antenna. 

Table 1 illustrates the effect of RS Gain ripple on maximum simulated RCS. Note that as the 

frequency increases from 34.7 GHz to 35.825 GHz the maximum simulated RCS actually 

decreases from 36.14 dBsm to 33.96 dBsm (decreased by 2.18 dB). Also note the gain is also 

decreased from 48.8 dB to 46.3 dB (decreased by 2.5 dB). Thus, if the gain were constant the 

simulated RCS would have actually increased by 0.32 dB (again similar to the natural increase of 

a “true” target). 

If the user desires, the gain ripple may be removed by applying an initial value to AT3 which 

would change GRS to 45.5 dB. For example if operation at 35.825 GHz is desired an initial 

attenuation value of 0.8 dB should be set on AT3. This would reduce GRS to 45.5 dB and change 

σmax to 33.16 dBsm (recall that for constant gain, σmax still increases by a small amount). Care 

must be exercised to remember the initial value when determining future settings for RCS 

reduction. As an example, suppose the user desires to simulate 0 dBsm at 34.7 GHz using the 

above discussed gain ripple removal technique. The gain is 3.3 dB higher than the reference 

value at 33.575 GHz (this frequency is chosen as the reference since it has the lowest gain), thus 

AT3 should be set to 3.3 dB. This will reduce GRS to 45.5 dB and via equation 8b σmax would 

equal 32.84 dBsm. To achieve a simulation of 0 dBsm, GRS must be reduced by 32.84 dB, which 

is accomplished by setting AT3 to a value of this desired decrease plus the initial value. In this 

case that value is (32.84+3.3=) 36.14 dB. Once again that level of precision is not possible with 

AT3 so a setting of 36 dB will have to suffice. 

Maximum Simulated RCS may be calculated for any frequency the user desires by using 

equation 8b. To determine the correct value of GRS to use, consult the appendix which lists the 

measured values of GRS from 33 GHz to 37 GHz in 20 MHz increments. To calculate the correct 

value of GRS_ANT, equation 9 can be used to solve for the constant value of the Antenna Effective 

Aperture (Ae) when the Gain and wavelength are known. Use this constant value (in the case of 

our RS Receive Horns, Ae=5.66 * 10–4 m2

) with the new wavelength corresponding to the new 

frequency of interest to calculate the new GRS_ANT in equation 9. 

Operating Instructions 

The RS is housed in a white portable rack enclosure which is weatherproof when the both front 

and rear doors are attached. Figure 4 is a photograph of the RS in its transit/storage state. 
8 

Figure 4. Remote station in transit/storage state. 

Located at the four corners of the front and rear doors are spring loaded fasteners which seal the 

doors to the enclosure creating the weatherproof condition. These fasteners must be completely 

tightened to ensure a weatherproof seal and/or secure shipping mode. There are also two 

latching fasteners on the center sides of each door which provide an extra layer of closure. 

Engaging these latching fasteners is not required. 

The RS has a total weight of 154 lbs. When moving the RS manually, two persons are required 

to lift the unit using the side handles shown in figure 4. The task is simplified when four persons 

each use a handle and position the RS in place. Be sure to face the “FRONT” of the RS towards 

the source of RF Radiation. 

To verify a safe range of operation, consider the scenario illustrated in figure 5. 

LATCHING 

FASTENERS 

(OPTIONAL) 

SPRING 

LOADED 

FASTENERS 

(REQUIRED) 

SPRING 

LOADED 

FASTENERS 

(REQUIRED) 
9 

Figure 5. Field test setup to determine minimum range. 

The radiated signal will endure space (or path) loss as it travels through the atmosphere. This 

space loss, (SL), is defined by Wolff & Kaul3 as 

⎟

⎠

⎞ ⎜

⎝

⎛ = λ

πR SL dB 4 ( (dB) (10) ) 20log

The two antenna gains shown in figure 4 reduce the Space Loss encountered by directing 

(pointing) the energy in a certain direction. When the two antennae are aimed at each other, the 

actual loss is then the sum of the Gain of the Transmit Antenna (Gt) in dBi and the Gain of the 

RS Receive Antenna (Grx) in dBi less the Space Loss (SL) in dB. The input Power to the RS, 

PIN, would then be the amount of Power Transmitted, Pt (in dBm), less the actual loss and is 

given by equation 11: 

PIN = Pt + Gt − SL dB + Grx ( (dBm) (11) )

Recall that PIN must be less than or equal to –35 dBm to prevent the RS from exhibiting gain 

compression which sets up a maximum input power level condition. This condition has a 

corresponding minimum range, Rmin, which will be derived at this point. 

Equation 11 can be solved for SL(dB) as in equation 12: 

SL dB = Pt − PIN + Gt + Grx ( (dB) (12) )

Setting equations 12 and 10 equal to each other yields: 

 3Edward A. Wolff & Roger Kaul, Microwave Engineering and Systems Applications, p. 26, John Wiley & Sons, 1988. 

PIN 

Gt Grx

Pt

RADIATION 

SOURCE 

REMOTE 

STATION 

⎟

⎠

⎞ ⎜

⎝

⎛ = λ

πR SL dB 4 ( ) 20log
10 

Pt PIN Gt Grx

R ⎟ = − + + ⎠

⎞ ⎜

⎝

⎛

λ

4π 20 (dB) (13) log

Equation 13 can be solved for R as follows: 

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡ = ⎟

⎠

⎞ ⎜

⎝

⎛ − + +

20 10

4

Pt PIN Gt Grx

R

π

λ (m) (14) 

Setting the maximum input power, PIN, equal to the maximum value of –35 dBm allows the use 

of equation 14 to calculate, Rmin as shown in equation 15. 

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡ = ⎟

⎠

⎞ ⎜

⎝

⎛ + + +

20

35

min 10

4

Pt dBm Gt Grx

R

π

λ (m) (15) 

For example, consider a radiation source operating with 150 W of output power, a Transmit 

Antenna with 42 dBi of Gain at 34.7 GHz the determination of Rmin is as follows: 

1. From Table 1, Grx is 19.5 dBi 

2. Transmit Power=150 W=150,000 mw=>Pt=10log(150,000 mw)=+51.76 dBm 

3. λ=c/f=(3*108

 m/s)/(34.7 GHz)=8.65*10–3 m 

4. Substituting these values into equation 15 gives: 

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡ = ⎟

⎠

⎞ ⎜

⎝

⎛ + + + −

20

51.76 35 42 19.5 3

min 10

4

8.65*10 dBm dBm dBi dBi

m R

π

=17,806.64 m=17.8 km 

Thus, the RS should be at least 17.81 km from the radiation source in this example to prevent 

gain compression. If this is not possible, the user can either (1) reduce the amount of transmit 

power or (2) reduce the link gain by misaligning the RS antenna and that of the source transmit 

antenna (aim-off). 

Once a safe location has been determined as described above, the RS may be positioned. The RS 

may be placed directly on the ground, however, it is recommended that if wet (swampy) 

conditions are expected that the unit be placed on a structure to elevate it such that the possibility 

of ground water flooding the bottom of the enclosure (where the power supply is located) is 

eliminated. 

Remove each door by rotating the latching fasteners (if engaged) and the spring loaded fasteners 

counterclockwise (to the left) until the door is free of all connections. The doors may be stored 

on the ground provided that the inside of the door is not susceptible to collecting ground water. 

When reattaching the doors, check that the inside of the doors are free of debris (sand, dirt, 
11 

insects, grass, etc.) and moisture. Avoid placing heavy items on the doors when they are 

removed as this may bend the doors such that they can not be reattached. Figure 6 contains 

photographs of the interior of the enclosure showing the frontal view in figure 6(a) and the rear 

view in figure 6(b) with key user interfaces highlighted. The locking clips shown in figure 6(a) 

are required to prevent the RF Deck and Power Supply Decks from sliding out. If service is 

required, these locking clips must be removed. 

(a) (b) 

Figure 6. (a) Frontal view of the RS (b) rear view of the RS. 

Figure 7 is a photograph of the Aiming Plate. 

LAPTOP 

DECK 

POWER 

SUPPLY 

RX IN 

RS-232 

INTERFACE 

LOCKING CLIPS 

RESET 

SW 

AC PWR IN 

TX OUT 

DC 

CONNECT 
12 

 

Figure 7. Remote station aiming plate. 

Mount the aiming plate on a tripod and use the aiming scope to align the antennae with the 

radiation source. Connect the yellow coaxial cable labeled “RCVR” to the RX IN coaxial 

connection inside the RS chassis (left side as highlighted in figure 6(a)). Connect the yellow 

coaxial cable labeled “XMTR” to the TX OUT coaxial connection inside the RS chassis (right 

side as highlighted in figure 6(a)). Connect the BNC Cable labeled “DC” to the RS DC Connect 

(a BNC Jack highlighted on the right side of figure 6(a)). When these connections are 

completed, figure 6(a) should now resemble figure 8. 

RCS 

ATTENUATOR 

RX ANT 

AIMING 

SCOPE 

TO RS RX IN TO RS TX OUT 

TO RS DC 

CONNECT 

TX ANT 
13 

Figure 8. RF deck with aiming plate connections in place. 

Connect a standard AC Line Power Cord to the AC Receptacle shown in figure 6(b). Make sure 

the power switch is in the OFF position and then plug the other end of the AC Line Power Cord 

into standard US AC Voltage (120 VAC rms). If you are planning to power the RS from a 

generator, it is recommended that you use the supplied Uninterruptible Power Supply (UPS) 

between the generator and the RS, as any fluctuation in line voltage will likely cycle the RS 

power supplies causing the SBC to reset to its default values without any indication to the user 

that this has occurred. Be sure to connect to the plugs on the side of the UPS labeled “Battery 

Backup plus Surge Protection” as the opposite side does not provide battery backup. Move the 

Power Switch to the ON position. The red power indicator should now be illuminated and the 

user should be able to hear the power supply fans operating. The Level Variable Attenuators 

will also “CLICK” upon power-up. If these conditions do not occur, check the status of the fuse 

(a slow acting 3A device) and replace if required. 

Locate (shipped separately) and unpack the RS Laptop and check to make sure all components 

shown in figure 9 are present. Connect the RS-232 extender cable to the Serial Port (on the rear 

of the laptop) and to the input RS-232 port of the SBC as shown in figure 10. It is recommended 
14 

to use the AC Power Adaptor to power the Laptop, if feasible, so that the battery may be kept 

fully charged. However, the laptop may be operated solely from its internal battery until the 

battery is depleted. If this is the case, expect frequent entrances into sleep mode to conserve 

battery power. During down time, the laptop should be connected to the AC Power adapter so 

that the battery will be replenished for the next operational cycle. To use the AC Power Adapter, 

align the DC Icons on the Adapter and on the port (on the right side of the Laptop) and slide in to 

connect and then plug in the other end of the Adapter to US AC Power (117 V rms) or to the 

UPS. The green LED on the Adapter AC to DC Transformer should illuminate and the battery 

icon on the laptop front panel should also illuminate. 

Figure 9. Remote station laptop critical items. 

Figure 10. RS-232 interface attachment. 

CARRYING 

CASE 

LAPTOP 

AC 

ADAPTER 

RS-232 

EXTENDER 

CABLE 
15 

Press the Power Button on the Laptop Front panel (to the left above the keyboard). The power 

LED should illuminate on the Laptop and Windows 98 should load ending with the Guest Login 

screen. Click OK to login as guest (no password is needed). Click CLOSE if an “Old Virus 

Definition File” Dialog Box appears. Figure 11 is a screenshot of the Desktop which should be 

displayed. 

Figure 11. Screenshot of RS laptop desktop. 

Double click the Full Control VI as highlighted in figure 11. This is a National Instruments Lab 

View Run Time Executable file and will launch the compiled Virtual Instrument (VI) as shown 

in figure 12. There are a number of controls present, however, only the Doppler frequency offset 

(fd) control will be used. As with all Vis, the first step is to start the VI by clicking on the white 

Run arrow in the upper left corner of figure 12. Next click the DDS_FREQUENCY Tab as 

highlighted in figure 12. The resulting Display is shown in figure 13. 

DOUBLE CLICK “FULL CONTROL” TO CONFIGURE fd
16 

Figure 12. Screenshot of full control VI. 

In the DDS_FREQ1 Box (highlighted in figure 13), enter the desired Doppler Frequency offset 

in Hertz. For example, enter “200” for 200 Hz, “1000” for 1 kHz or “3000” for 3 kHz. The 

acceptable range is 0 to 1000000 (1 MHz). Be sure to press the ENTER key after typing in the 

desired value. Next click the OK button under the SEND DATA text. Note that (1) you should 

hear clicking sounds as the configuration commands are sent by the SBC to switches and 

variable attenuators (not currently in use) and (2) the data string is updated as shown in figure 13 

reflecting the desired value of fd. If for some reason, the AC power fluctuates enough, the SBC 

will reset to a default value with no indication to the user that this has occurred. Furthermore, 

the VI will be hung up and will not be able to send data (even though the Concatenated String 

field shown in figure 13 will update, the message traffic is NOT being transmitted). To rectify 

this situation, depress the red reset switch shown in figure 6(b) and you will hear a click. Data 

can now be sent normally by clicking OK under the SEND DATA text. 

The other parameter to set is the simulated RCS. As discussed in the preceding section, simply 

rotate the knob on the RCS Attenuator (AT3) on the aiming plate to the desired value of 

attenuation corresponding to the desired value of simulated RCS. As mentioned above, the 

attenuation values are only calibrated for those areas within the readout range (0 to 50 dB) with 

less precision as attenuation values increase. 

1. CLICK 

HERE TO 

START VI 

2. CLICK HERE 

TO BRING fd TAB 

FORWARD 
17 

Figure 13. Screenshot of fd setting sent to SBC (and DDS). 

At this point the RS is completely configured and operational. To change simulated RCS change 

the attenuation value as described in the preceding section. To change fd, repeat the process 

shown in figure 13 making sure to (1) press ENTER in Step 1 and (2) Press OK as in Step 2. 

Again, if it appears that this process is not working, reset the SBC by pressing the reset switch 

and retry the data transmission. 

The RS may be operated in all conditions including precipitation provided the power supplies are 

protected from liquid accumulation sufficient to short out the voltage lines. The use of a plastic 

wrap to protect the power supplies on the front of the RS chassis as well as the terminal blocks 

on the rear of the RS chassis and on the aiming plate and on all exposed voltage terminals of 

active elements (i.e., amplifiers on the aiming plate) is strongly recommended. If the power 

supplies detect a short condition, protection circuitry will current (and thus voltage) limit the 

output such that the RS will effectively shut down. 

To shut down the RS, simply turn off the AC Power Switch. The laptop should be Shut-Down 

following standard Windows shut down procedures. Make sure to press the power button on 

UPS (turn off) or the battery on the UPS will deplete when the AC Power source (generator) is 

switched off. The laptop, aiming plate and UPS may be stored on the laptop deck shown in 

figure 6 and the doors reattached which provides a weatherproof container. This should only 

occur provided the RS is not to be transported. The coaxial connections between the aiming 

1. ENTER fd

IN HERTZ 

AND PRESS 

ENTER 

2. PRESS OK TO 

SEND DATA TO SBC 3. NOTE 

UPDATED 

DATA STRING 

(freq1) 
18 

plate and the RS chassis can not withstand the vibration environment associated with 

transportation. If the RS is to be transported any distance, the aiming plate should be 

disconnected and the packed in its shipping crate. The Laptop should be put away in its carrying 

case and the UPS should also be packed separately from the RS. 

Conclusion 

A Millimeter Wave Transponder has been developed to simulate a moving target with the ability 

to alter RCS and Doppler frequency. An explanation of the RF Architecture followed by a 

detailed derivation of Simulated RCS has been given. Start to finish operating instructions are 

also provided. 
19 

Appendix 

Measured RS Gain (data points for figure 3) 

(33 to 34 GHz) (34 to 35 GHz) (35 to 36 GHz) 

Frequency 

(GHz) |S21| (dB) 

Frequency 

(GHz) |S21| (dB) 

Frequency 

(GHz) |S21| (dB) 

33 40.602 34.02 48.89 35.02 47.588 

33.02 42.323 34.04 48.602 35.04 46.891 

33.04 43.452 34.06 48.324 35.06 46.36 

33.06 44.219 34.08 47.776 35.08 45.818 

33.08 44.733 34.1 47.483 35.1 45.489 

33.1 44.419 34.12 47.327 35.12 45.349 

33.12 44.222 34.14 47.316 35.14 45.387 

33.14 44.977 34.16 47.483 35.16 45.591 

33.16 45.783 34.18 47.734 35.18 46.03 

33.18 46.295 34.2 48.011 35.2 46.296 

33.2 47.414 34.22 48.31 35.22 46.441 

33.22 48.066 34.24 48.549 35.24 46.679 

33.24 47.858 34.26 48.484 35.26 46.667 

33.26 47.873 34.28 48.421 35.28 46.407 

33.28 47.986 34.3 48.476 35.3 46.373 

33.3 47.44 34.32 48.488 35.32 46.477 

33.32 47.294 34.34 48.386 35.34 46.449 

33.34 47.313 34.36 48.436 35.36 46.474 

33.36 46.889 34.38 48.292 35.38 46.371 

33.38 46.338 34.4 48.115 35.4 46.114 

33.4 46.842 34.42 47.879 35.42 45.579 

33.42 47.079 34.44 47.653 35.44 45.302 

33.44 47.06 34.46 47.605 35.46 44.821 

33.46 47.799 34.48 47.682 35.48 44.421 

33.48 47.979 34.5 47.913 35.5 44.157 

33.5 47.206 34.52 48.266 35.52 44.236 

Frequency 

(GHz) |S21| (dB) 

Frequency 

(GHz) |S21| (dB) 

Frequency 

(GHz) |S21| (dB) 

33.54 46.416 34.56 49.324 35.56 44.677 

33.5575 45.761 34.58 49.637 35.58 45.338 

33.58 45.527 34.6 49.896 35.6 45.95 

33.6 46.197 34.62 49.866 35.62 46.561 

33.62 46.605 34.64 49.792 35.64 46.942 

33.64 47.181 34.66 49.498 35.66 47.176 

33.66 48.345 34.68 49.244 35.68 47.023 

33.68 48.954 34.7 48.828 35.7 46.801 

33.7 49.123 34.72 48.662 35.72 46.712 

33.72 49.462 34.74 48.413 35.74 46.658 

33.74 49.517 34.76 48.188 35.76 46.551 

33.76 49.294 34.78 47.779 35.78 46.555 
20 

33.78 49.215 34.8 47.509 35.8 46.489 

33.8 49.386 34.82 47.224 35.82 46.358 

33.82 49.015 34.84 46.948 35.84 46.187 

33.84 48.701 34.86 46.863 35.86 46.073 

33.86 48.426 34.88 46.929 35.88 45.885 

33.88 48.178 34.9 47.072 35.9 45.908 

33.9 47.769 34.92 47.344 35.92 45.922 

33.92 47.839 34.94 47.623 35.94 45.992 

33.94 47.953 34.96 48.039 35.96 46.175 

33.96 48.117 34.98 48.087 35.98 46.541 

33.98 48.552 35 47.995 36 46.582 

34 48.937 

 (36 to 37 GHz) 

Frequency 

(GHz) |S21| (dB) 

Frequency 

(GHz) |S21| (dB) 

Frequency 

(GHz) |S21| (dB) 

36.02 46.653 36.42 46.254 36.8 39.812 

36.04 46.245 36.44 45.67 36.82 36.599 

36.06 45.737 36.46 45.442 36.84 33.527 

36.08 45.119 36.48 45.542 36.86 30.843 

36.1 44.741 36.5 45.717 36.88 28.407 

36.12 44.39 36.52 45.947 36.9 26.12 

36.14 44.37 36.54 46.448 36.92 24.11 

36.16 44.453 36.56 46.882 36.94 22.31 

36.18 44.707 36.58 47.178 36.96 20.589 

36.2 45.021 36.6 47.138 36.98 18.966 

36.22 45.405 36.62 46.802 37 17.345 

36.24 45.463 36.64 46.219 

36.26 45.634 36.66 45.765 

36.28 45.928 36.68 45.531 

36.3 46.253 36.7 45.423 

36.32 46.454 36.72 45.448 

36.36 47.083 36.74 45.768 

36.38 46.925 36.76 44.799 

36.4 46.632 36.78 42.741 
21 

NO. OF 

COPIES ORGANIZATION

 1 ADMNSTR 

 ELEC DEFNS TECHL INFO CTR 

 ATTN DTIC OCP 

 (ELECTRONIC COPY) 

 8725 JOHN J KINGMAN RD STE 0944 

 FT BELVOIR VA 22060-6218 

 1 DARPA 

 ATTN IXO S WELBY 

 3701 N FAIRFAX DR 

 ARLINGTON VA 22203-1714 

 1 OFC OF THE SECY OF DEFNS 

 ATTN ODDRE (R&AT) 

 THE PENTAGON 

 WASHINGTON DC 20301-3080 

 1 US ARMY RSRCH DEV AND ENGRG 

 CMND 

 ARMAMENT RSRCH DEV AND 

 ENGRG CTR 

 ARMAMENT ENGRG AND TECHNLGY 

 CTR 

 ATTN AMSRD AAR AEF T J MATTS 

 BLDG 305 

 ABERDEEN PROVING GROUND MD 

 21005-5001 

 1 US ARMY TRADOC 

 BATTLE LAB INTEGRATION & TECHL 

 DIRCTRT 

 ATTN ATCD B 

 10 WHISTLER LANE 

 FT MONROE VA 23651-5850 

 1 PM TIMS, PROFILER (MMS-P) 

 AN/TMQ-52 

 ATTN B GRIFFIES 

 BUILDING 563 

 FT MONMOUTH NJ 07703 

 1 US ARMY INFO SYS ENGRG CMND 

 ATTN AMSEL IE TD F JENIA 

 FT HUACHUCA AZ 85613-5300 

 1 COMMANDER 

 US ARMY RDECOM 

 ATTN AMSRD AMR W C MCCORKLE 

 5400 FOWLER RD 

 REDSTONE ARSENAL AL 35898-5000 

NO. OF 

COPIES ORGANIZATION

 1 US ARMY RSRCH LAB 

 ATTN AMSRD ARL CI OK TP 

 TECHL LIB T LANDFRIED 

 BLDG 4600 

 ABERDEEN PROVING GROUND MD 

 21005-5066 

 1 US GOVERNMENT PRINT OFF 

 DEPOSITORY RECEIVING SECTION 

 ATTN MAIL STOP IDAD J TATE 

 732 NORTH CAPITOL ST NW 

 WASHINGTON DC 20402 

 DIRECTOR 

 1 US ARMY RSRCH LAB 

 ATTN AMSRD ARL RO EV 

 W D BACH 

 PO BOX 12211 

 RESEARCH TRIANGLE PARK NC 

 27709 

 14 US ARMY RSRCH LAB 

 ATTN AMSRD ARL CI OK T 

 TECHL PUB 

 ATTN AMSRD ARL CI OK TL 

 TECHL LIB 

 ATTN AMSRD ARL SE R 

 P AMIRTHARAJ 

 ATTN AMSRD ARL SE R J MAIT 

 ATTN AMSRD ARL SE RM 

 J CLARK (3 COPIES) 

 ATTN AMSRD ARL SE RM 

 R WELLMAN 

 ATTN AMSRD ARL SE RM E ADLER 

 ATTN AMSRD ARL SE RM R HARRIS 

 ATTN AMSRD ARL SE RM 

 D HUTCHINS 

 ATTN AMSRD ARL SE RM 

 J SILVIOUS 

 ATTN AMSRD ARL SE RM 

 A HARRISON 

 ATTN IMNE ALC IMS 

 MAIL & RECORDS MGMT 

 ADELPHI MD 20783-1197 

TOTAL: 25 (24 HCS, 1 ELECT) 
22 

INTENTIONALLY LEFT BLANK