Phase shifter circuit adjusts the phase relationship between a locally generated reference frequency and a received RF signal applied to a phase-coherent detector. It is small enough to be integrated into a receiver subassembly and operates on command from remote control panels

Johns, C. E.

English

NASA Technical Reports Server

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Output
June 1970	 Brief 70-10073 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Continuously Variable Voltage-Controlled Phase Shifter 
(a)
Odeg	 Dl 
Reference T1J	 R2 'Cl 90
Input 
	 .L D2 ht— T-ie®_I 
'[Jc2 I Rl 180 I_I_D3 
D4 
S	 ir
M	 I 
I Dl 02 D3 D4 Dl	 (d) 
. :9E1.0
L,/)c)KI)KIKi " (3	 00 90180 270 360 450 
Potentiometer Shaft Rotation. Deg. 
Figure 1. Voltage-Ci )ntrolled Phase Shifter 
This phase shifter circuit will adjust the phase	 (I) Continuously variable dc voltage cOntro 
relationship between a locally generated reference	 through 360° 
frequency and a received rf signal applied to a phase- 	 (2) RF circuit volume small enough to combine 
coherent detector. The phase shifter is small enough	 with a phase detector, thereby eliminating the phase 
to be integrated into a receiver subassembly such as 	 shifter subassembly 
a phase detector module and operates on command	 (3) Phase stability within ± 10° over the range of 
from remote control panels of automatic checkout 	 0° to 49°C 
equipment. The novel features are:	 (4) Applicability of the circuit to any reference 
(continued overteal) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned.rights.
https://ntrs.nasa.gov/search.jsp?R=19700000069 2020-03-17T00:24:54+00:00Z
0) IL 
U) 
0
8-
0 
uJ 
-C 
U) 
U) 
U) 
0
	 0	 40	 80	 120	 160	 200	 240	 280	 320	 360
Potentiometer Shaft Rotation, Deg. 
Figure 2. Phase Shift Error Versus Potentiometer Rotation 
input frequency from 100 kHz to 10 MHz. Although 
present phase shifters perform satisfactorily, they are 
physically large and do not lend themselves to remote 
automatic phasing for automatic checkout. 
As shown in the schematic, Figure 1, the dc voltage 
applied to diodes Dl, D2, D3, and D4 is supplied 
from the armatures of the sine/cosine potentiometer. 
As the potentiometer shaft is rotated through 360 w , it 
causes the conductance of each diode to vary sequen-
tially, as shown in Figure Id. 
Reference signals differing in phase by 90° are 
applied to the diodes at terminals W, X, Y, and Z. 
These signals are vectorially summed across the load 
resistor RL. For example, as the potentiometer shaft 
is rotated from 0° to 90°, D I goes from zero to full 
conduction, and the signal appearing across RL will 
be that which is applied to terminal W (0°). Shaft 
rotation from 90° to 180° will turn Dl off and D2 on. 
As this occurs, the effective resistance of D 1 is increas-
ing and that of D2 is decreasing. Since the resistance of 
each diode is a function of the applied forward dc 
voltage, i.e., RD = f(Ed), the resultant signal 
across R. is
= E [(sin
RD1 + RL 
RL	 1 
+ (sin wt + 90) 
RD2 + RL I 
where E is the signal amplitude applied to terminals 
W and X. For shaft rotation from 90° to 180°, the re-
sultant signal across RL varies in phase from 0° to 90°. 
For a shaft rotation from 180° to 270°, the same action 
takes place between D2 and D3, and the signal across 
RL changes phase from 90° to 180°. Between 270° and 
360°, the shift is repeated between D3 and D4. From 
360° to 90°, it occurs between D4 and : D1. Since the 
potentiometer has no stops, the reference signal phase 
can repeatedly be varied through 360°.
A linear integrated circuit (Figure Ic) is used to am-
plify the small signal across R L to a suitable level. The 
output of the amplifier is applied across R4 and diodes 
D5 and D6, which serve as amplitude limiters to re-
duce the reference-signal amplitude variations due to 
potentiometer rotation. The quadrature signals applied 
to terminals W, X, Y, and Z are generated by trans-
former Ti (Figure Ia) and the phase lead and lag net-
works Rl, C  and R2, C2. To change the operating 
center frequency of the phase shifter, it is necessary to 
change only the values of Cl and C2 (Figure la) to 
assure a 90° phase lead and lag. Circuitry is minimal 
and requires little more than 1 cu. in. packaging space, 
which is small enough to allow its installation within 
a phase detector. 
The phase shift error versus potentiometer shaft 
rotation and temperature variations is shown in Fig-
ure 2. As shown, the phase shift at any potentiometer 
shaft setting is well within the design goal of ± 10° 
over the temperature range. 
Notes: 
The dc voltages to the diodes can be supplied from 
two digital-to-analog converters, rather than from 
a sine/cosine potentiometer, thus allowing the 
circuit to be programmed for automatic checkout. 
Documentation is available from: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP70-10073 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code GP, 
Washington, D.C. 20546.
Source: C. E. Johns of 
Caltech/JPL
under contract to
NASA Pasadena Office

(NPO-1 1129) 
Brief 70-10073	 Category 01


Continuously variable voltage-controlled phase shifter

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