An analysis was made on two commercially available silicon and gallium arsenide Schottky barrier diodes. These diodes were selected because of their particularly low noise figure in the frequency range of interest. The specified noise figure for the silicon and gallium arsenide diodes were 6.3 db and 5.3 db respectively when functioning as mixers in the 13.6 GHz region with optimum local oscillator drive

Dombrowski, M.

English

NASA Technical Reports Server

General Disclaimer 
One or more of the Following Statements may affect this Document 
 
 This document has been reproduced from the best copy furnished by the 
organizational source. It is being released in the interest of making available as 
much information as possible. 
 
 This document may contain data, which exceeds the sheet parameters. It was 
furnished in this condition by the organizational source and is the best copy 
available. 
 
 This document may contain tone-on-tone or color graphs, charts and/or pictures, 
which have been reproduced in black and white. 
 
 This document is paginated as submitted by the original source. 
 
 Portions of this document are not fully legible due to the historical nature of some 
of the material. However, it is the best reproduction available from the original 
submission. 
 
 
 
 
 
 
 
Produced by the NASA Center for Aerospace Information (CASI) 
https://ntrs.nasa.gov/search.jsp?R=19770023373 2020-03-22T07:19:08+00:00Z
!	 „„^, ^ ,er
	 nr V R
i	 I
X-953-77-147
PRE PR I NT
^)) X	 4^ .z-
13.9 GHZ SHORT PULSE RADAR NOISE
FIGURE MEASUREMENTS UTILIZING
SILICON AND GALLIUM-ARSENIDE,
MIXER DIODES
r.. ,
l	 ;;A-TM-X-71362)
	 THE 13.9 Ghz SHChT PULSE
hN)AF NOISE FIGURE MEASUREMENTS UTILIZING
SILILLN AND GAILIUM-A£+SENIL'E MIREL LICLES
(NA:)A)
	 15 p hC AC2/MF A01
	 CSCL 17I
. 77-.10317
Uuclas
G3/32 42859
MARK DOMBROWSKI
JULY 1977
- 
GODDARD SPACE FLIGHT CENTER
GREENBELT, MARYLAND
Awl 97 7rr 	 1 ^j /	 -`
RECEIVED N
RASA STI FACIL ifY
INPUT 8RANCH
r
.^ _
	
1	 [ ^^_^r.. _ 1. __ _ ^ 	 G	 !
X-953-77-147
fn,
;i
s
13.9 GHZ SHORT PULSE RADAR NOISE
FIGURE MEASUREMENTS UTILIZING SILICON
AND GALLIUM-ARSENIDE MIXER DIODES
Mark Dombrowski
July 1977
^n	
3
I	 I	 In	 l	 I.rrter, AlSF'. [^	 I
13.9 GHZ SHORT PULSE RADAR NOISE
FIGURE MEASUREMENTS UTILIZING SILICON
AND GALLIUM-ARSENIDE MIXER DIODES
Mark Dombrowski
Microwave Sensor Branch
ABSTRACT
An analysis was made on two low noise Schottky barrier mixer diodes which
were intended to be used in the GSFC 13.9 short pulse radar employed in sea state
studies. Considered in this comparison were commercially available silicon and
gallium-arsenide Schottky barrier diodes. These diodes were selected because
of their particularly low noise figure in the frequency range of interest. The
manufacturer's specified noise figure for the silicon and gallium-arsenide diodes
were 6.3 dB and 5.3 dB respectively when functioning as mixers in the 13.6 GHz
region with optimum local oscillator drive.
iii:
13.9 GIIZ SHORT PULSE RADAR NOISE
FIGURE MEASUREMENTS UTILIZING SILICON
AND GALLIUM-ARSENIDE MIXER DIODES
INTRODUCTION
A novel test procedure was developed which characterized the responses
expected by the "twice-power" and "Y-factor" methods of noise figure measure-
ments.
This analysis was also directed at obtaining a bench mark for the receiver
front end, mixer/preamplifier section, of the radar sensor. In addition, the long
term objective would be to interchange detectors and examine sea state return
data for improvements in the small signal response.
The test conducted on these semiconductors considted of a modified version
of the "twice-power" method for manual noise figure measurement, pulsing of
the noise source.
Before continuing with the test procedure it is first necessary to define what
is meant by the system noise figure. By stating a system's noise figure one can
say that a measure of the sensitivity of that system is known. For as the noise
figure of a system improves, approaches 0 dB, there is an associated decrease
in the signal power necessary for a similar detected voltage — increased sensitivity.
System noise is essentially generated by two sources, Johnson noise and shot
noise. Johnson noise is introduced into a system by the fluctuations of voltage
developed across a device's junction caused by random thermal motion. Shot
noise, on the other hand, is brought about by the random current fluctuations.
In a measuring system such as a detector, involving small power levels, it
may be defined that the minimum detectable power is that value resulting in a
signal power output from the detector equal to that of the noise. Diode noise cur-
rent, either Johnson noise or shot noise, limits the effectiveness of the mixing
operation by increasing the effective noise floor.
When calculating the noise power delivered by a load resistor into a systetli,
it is convenient to assume that no mismatches occur. If this is assumed, then tho
noise power can be expressed as a function of a resistance, R, at temperature T,
inducing a voltage V. Since noise power is of interest and not necessarilvy voltage
1
for this matched load, the available noise power can be expressed as P' = KTB
where K is Boltzmann's constant (1.37 x 10- 23 joules/°K), T is the temperature
in degrees Kelvin and B is the bandwidth of the measuring system. In actuality
the available noise power level may be lower due to mixmatches and losses. For
these calculations losses will not be considered.
Calculating the noise power level as seen by the radar front end with a band-
width of 200 MHz, the IF amplifier bandwidth, and at a temperature of 290°K we
obtain
P1 = (1,37 x 10- 23 joules/°K) (290 °K) (200 MHz)
= 7.946 x 10 -i3 watts.
Converting watts to dBm
PI dBw = 10 log P 1 = - 121 dBw
or
P1 dBm = P 1 dBw - 30 dB = - 91 dBm.
This is thebandwidth limited noise power level of theinatched terminating
resistance.
To develop a figure of merit for the radar front end, a ratio must be de-
veloped between the actual output noise power to this theoretical minimum,
-91 dBm. This figure of merit is referred to as the system noise figure, NF.
Therefore,
NF = P1/KTBG
where G is the gain added to the system.
If a broadband noise source is introduced at the input of the device under
test, (in place of the termination,) a differential power measurement at the sys-
tem's output would indicate the gain bandwidth product of the device. By using
a gas discharge tube as an external noise source at the input port, a noise power
level, P2 , higher than that found at room temperature is obtained. For an argon
gNA;, noise tube the effective temperature, T 2 , is about 10 4 °K. By comparing the
1loise power levels at these two temperatures, it is possible to calculate the noise
figure of the mixer.
2
The ratio of these two power levels, P l and P2 , is calculated as follows:
P2
 (NF) Ti+ (T2 - T l )
P 1 	(NF)T1
By reducing and solving for NF we obtain
NF - 
(T2 _ T1)	
1 \Tl
or in dB 
	
I Pl _ l l
NFdB = 10 log f T2 T TI I - 10 log P2 - 1)
\	 1	 /	 \ 1	 I
The first term on the right-hand side is a measure of the relative/excess noise
power available from the argon noise source. For these calculations, this term
is referred to as the excess noise ratio and is equal to 15.25 dB./Therefore,
/P	 1NFdB = 15.25 dB - 10 log I P2 
_ 11 equation 1\ i
This process is illustrated below..
EXCESS NOISE
X 
RECEIVER	 RECEIVER
ADDED	 ADDED	 P2
NOISE	
Pi
	
NOISE
INPUT	 INPUT
TERMINATION X G I TERMINATION X G
This method employed for making the radar front end noise figure measurement
was a modification of the "twice-power" method. The test consisted of measur-
ing P i and P., thereby satisfying equation 1. However, the power level P would
be selected such that it was twice the level of P,. Thereby reducing equation 1 to
NF dB = 15.25 - 10 log(1) = 15.25
3
3
,y
t
L	 ,1
;z
G
POWER DETECTOR
AND
OSCILLOSCOPE
MIXER UNDER
TEST
^S
t
y
i
Ij	
>,
hnlnlKiAT. 1
Attenuation is necessary to satisfy this condition and develop a value for the
noise figure. By using the test set-up shown below, the rotary vane attenuator
will reduce the excess noise source power level, detected and viewed on an
oscilloscope, by 3 dB — half power. This particular arrangement is unique in
that the noise tube is pulsed on and off at 50%D duty cycle. This gives rise to the
3 dB or half power requirement necessary for 2P 1 = PZ.
INPUT
TERMINATION
PULSED EXCESS
NOISE SOURCE I
ROTARY VANE
ATTENUATOR
51St
The Modified Method of Manual Noise Figure Measurement.
The timing waveforms for the test are shown below:
AMPLIFIER	 ON
POWER... 	 OFF
NOISE
TUBE	 O
PULSE	
7 
NOISE c7
TUBE
Pr
OUTPUT P.
3
rj=rp
50% DUTY CYCLE
i
s
T ^ .:1	 I	 1
210 +
90 082
070
015 038
010 (0,25
AGP
The data procedure for this experiment set-up is as follows:
1. Turn on all necessary power supplies while keeping the noise tube off.
Note, it is necessary for sufficient gain to be present so that a convenient ref-
erence value can be located on the power meter. Record the power meter read-
ing, Pl . In addition, record the attenuator setting, Al.
2. Turn on the excess noise source. Check to see the duty cycle for the
discharge tube is 50%D•
3. With the noise source on, the power meter should indicate a higher power
level. If not, additional gain is needed. Record this power meter value, this is
P2 , now slowly increase the rotary vane attenuator to bring the power meter level,
P2 , back to the initial setting, P l . Record the attenuator value, A 2 . Note that
A > A . The condition now exists where P  = 2 P,. The difference between
these two attenuator settings is the noise figure of the device.
TEST PROCEDURE
The two diodes tested were Hewlett-Packard's model 5082-2723 Silicon
Schottky-Barrier diode and Alpha Industries, Inc. Model DMK-6602A Gallium-
Arsenide Diode. Both diodes were supplied in double stud ceramic packages as
shown below.
1,63
152
069—	
OBO
l
1
a
d
5,0, 3	 3
♦ 	 r,
CATHODE ENO
INDICATED By	 =4
COLOn n0-	 r— 078
2.13	
E
(1.98
5
r
^•	 ^	 ^	 1.	 ^
n'	 4
fin In r nre T. t Af-M Kq
Supplied with both diodes were the manufacturer's specifications p,
to noise figure, cut-off frequency, junction capacitance, junction resist,,
series resistance. Shown below are the company's typical specified va
Hewlett Alpha
Parameter Packard Industries Units
Noise
Figure 6.3 5.3 dB
NF
Cut-off
Frequency 136* 700 GHz
fca
Junction
C apacitance 0.13 0.10 pfd
CS
Junction
Resistance 3001 300t ohms
RS
Series
Resistance 9 2.3* ohms
R5
* Calculate value	 1St I.F. noise
I TYPical value	 figure = 1.8 dB
The first IF amplifier's noise figure is given above to rule out any error
introduced by it. The IF amplifier's input was modified by introducing a series	 i
choke and resistor to ground thereby supplying a path for diode current.
The diode's equivalent circuit is shown below and will be used to identify the
parameters set forth in the previous table.
R S 	 ARI
4
l
f
i i
The sensitivity of a low level detector is determined by various methods in-
eluding the current responsivity (,6), noise equivalent power (NEP) and tangential
sensitivity (TSS).
	
The low level current responsivity, )G, is defined as	 j
A
_ 8	 1
•	 R 2nKT1
	
(	 z	 ^
+ 
R
RiJ ^1 + \ ffoo/ J
Where	 Q is the charge on an electron, 1.602 x 10 -19 coulomb
n is the electron density ideality factor, 1.05 for hot carrier diodes.
K is Boltzmann's constant, 1.38 x 10' 23 joules per °K.
T is the temperature in Kelvin
R. is the diodes series resistance
R i is the diodes junction resistance
f is the operating frequency
f ro is the diodes cut-off frequency.
Therefore,
=1.906x 101	 1
RS
	
1+	
+	 f 2)
R i	 f C J
and for silicon
/3Si	 1. 83 10 1 = 18. 3
and for gallium-arsenide
8GaAsc1.89x101=18.9
"s
nn ln_iTTAT. 1 Ar3P K	
Y
i
i
7
Noise equivalent power -, CEP) is the term associated with the microwave
input power required for a unity signal-to-noise ratio in a 1 Hz bandwidth at the
output of the detector.	 This definition will be used to obtain a measure of the
threshold sensitivity characteristic of both the silicon and gallium-arsenide
	 p
diodes.
Noise equivalent power is calculated as
NEP= 2nKT r4KTt6o]1/z 	 RSl 
1/2	 f \z	 'N] 112
8	 L R.	
+R.J	 [1+	 +fco/
l
] [1fIF
Sy
where tw is the "white noise" temperature ratio, approximately 0.95
y
f 	 is the noise corner frequency for the diode, 100 kHz for both silicon
and Gallium-Arsenide
	
y
y'
is the intermediate frequency, 300 MHz.fIF
Thus
R	 1/2	 z	 f	 1/2
NEP = 3. 74 x 10 -13 
C1 + RSJ	
[1 + (f  1	
L
l + fNL	 ` co/	 IFJ
and for silicon
NEPs1 = 3.83 x i0-13
or
NEPsI (dBm) _ -94.16 dBm
and for gallium-arsenide
NEPG.A. = 3.76 x 10 -19
or
NEPG.A. (dBm) = -94.24 dBm.
The tangential sensitivity, TSS, can be found by two methods. First, by ad-•
'ustin	 the in ut	 ower level to-
	
_leve l such that the highest'
	
is	 ak	 thg	 p p 	 no a pe , n e
absence of the signal is at the same level as the lowest peak in the presence of
the signal. This input level is then the tangential sensit^i'sit3 ? The second methcd
is by calculating it from the noise equivalent power. Thus,
8
TSS = 2.5 (NEP)
where B is the IF bandwidth 200 MHz.
Therefore,
TSS dBm = NEP dBm + 45. 5 dB
and for silicon
TSSsi dBm = -48.65 dBm
and for gallium-arsenide
TSS GaAs dBm = -48. 73 dBm.
Since a low level detector operates in the diode's square law region, the output
voltage is proportional to the RF input power, the tangential sensitivity value is
numerically proportional to the square root of the IF bandwidth.
By calculating the voltage sensitivity, an indication of the responsivity to a
small signal is obtained. Since the voltage sensitivity, y, is defined as (R i
 +Rs)9,
we find that for silicon
ysi = 5.65 my/w
and for gallium -arsenide
ycaA. = 5. 7 my/w
The diode's loss needs to be examined too since it is a function of the junc-
tion capacitance and series resistance. By defining this loss as
where co = 277f, we obtain for silicon
^ s . dB = 1. 39 dB
and for gallium-arsenide
^GaAs dB = 0.25 dB
It can be seen from the above that a small difference in the diode's series
resistance and junction capacitance does effect its characteristic losses.
I
J'
r
r
I
ORIGINAL PAGE IS
OF POOR, QUALITY
Below is a photograph of the diode housing used in both tests. This particu-
lar configuration, used in the down mixer of the 13.9 GIIz radar, utilizes image
enhancement to optimize the noise figure. The two diodes were introduced in the
mount without any variation in the tuning loads L 1 and L 2 . Peak tuning was
accomplished by an externally mounted stud.
I.F. OUTPUT PORT
04
r4W 9 i of
L.O. AND
R,F.INPUT	 L1
MIXERPORT L2 DIODE 0
' • •
1
It was found that in both cases the overall mixer frequency response from
200 MHz to 400 MHz, did not vary. Examination of the test data below indicates
that the prime parameter change in the mixer was the locil oscillator drive.
The gallium-arsenide diode required about 8 dB more drive to achieve an IF
power level similar to that obtained from the silicon dic1e.
SUMMARY
The noise figure test procedure described previously, gave the values shown
below. Noise figure values for the silicon and gallium-arsenide diodes were 7.3
dB and 6.5 dB respectively. Because an oscilloscope/power meter arrangement
was used, a sequence of runs were made in order to obtain a representative aver-
age value. In this averaging the highest and lowest values have been discarded.
It should be noted that for the noise figure tests run on the silicon and gallium-
arsenide mixer diodes, the LO power level was selected to optimize the particular
diodes NF response. In obtaining this optimal value, a low level 13.9 GIIz CW sig-
nal was provided. A continuo- 'y variable 13.6 GHz LO drive allowed optimization
as the IF output power was mu, ;ored and recorded for indications of crystal sat-
uration. These values are shk-,vn in figure 1.
10
n r^mrer. 1 nr_7 NO	 1 I
/
The diode's mixer performance factors can be seen from the table of calcu-
lated and specified values shown below. Obviously the manufacturer's quoted
noise figure is of importance ;, nevertheless, the performance (sensitivity) of each
diode dictates its versatility I.n mixer design. Because the diode':; cut-off fre-
quency is inversely proportional to the junction capacitance and series resistance,
any variation in these parameters is reflected in this c»t-off frequency. Diode
losses are also associated with these parameters, by their product squared. This
is evident in the 1.14 dB difference in the loss experienced by the input signal
power delivered to the junction resistance (R i ).
Bemues, Kuno and Candell, (Reference 1) have verified that in order to keep
degradation of the optimum conversion loss less than 1 dB, it is required that
f /f	 > 10 and R /?1 > 10. The gallium-arsenide diode satisfied both of
theseconditions. The silicon diode, however, is borderline, thus resulting in a
higher loss value. The experimental conversion loss values include the loss
introduced by less than ideal matches throughout the system.
REFERENCES
1. Microwaves: March 1976; GaAs or Si: What Makes a Better Mixer Diode?;
F. Bemus, H. J. Kuno, P. A. Crandell.
2. Microwaves: September 1976: Select the Best Diode for Millimeter Mixers;
Dr. Geralt T. W"rixon.
3. Introduction to Microwave Theory and Measurement; A. L. Lance; McGraw-
Hill.
4. Microwave Semiconductor Devices and Their Current Applications: H. A.
Watson; McGraw-Hill.	 3
j
5. MIT Radiation Laboratory Series Volume 15.
6. MIT Radiation Laboratory Series Volume 16.
7. "Quantitative Comparison of Solid State Microwave Detectors;" A. M. Cowley,
H. 0. Sorenson; IEEE Transactions, MIT-14 #2.
8. "Characterization of Crystal Diodes for Low-Level Microwave Detection;"
A. Uhlir, Jr.; The Microwave Journal, July 1963.
9. Introduction to Optical Electronics; Amnon Yariv; Holt Rinehart Winston.
11
i
,n
n
nnTr! lgYAT. AT3F' K
10. An Introduction to Lasers and Masers; A. E. Siegman; McGraw-Hill.
11. Microwave Engineer's Handbook; Volume 2; Aertech.
t
.y. X
12


The 13.9 GHz short pulse radar noise figure measurements utilizing silicon and gallium-arsenide mixer diodes

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server