A 36-element monolithic grid amplifier has been fabricated. The peak gain is 4 dB at 40 GHz with a 3-dB bandwidth of 800 MHz. We discuss the design and measurements for the monolithic grid amplifier. The grid includes base stabilizing capacitors which result in a highly stable grid. This is the first report of a successful monolithic grid amplifier

Liu, Cheh-Ming

Rutledge, David B.

Sovero, Emilio A.

English

Caltech Authors - Main

40 GHz Monolithic Grid Amplifier

GHz Monolithic Grid Amplifier 
Cheh-Ming Liul, Emilio A. Sovero2, and David B. Rutledgel 
Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125 
Rockwell International Corporation, 1049 Camino Dos &os, Thousand Oaks, CA 91385 
Abstract-A 36-element monolithic grid amplifier has been fabricated. The peak gain 
is 4 dB at 40GHz with a 3-dB bandwidth of 800MHz. We will discuss the design 
and measurements for the monolithic grid amplifier. The grid includes base stabilizing 
capacitors which result in a highly stable grid. This is the first report of a successful 
monolithic grid amplifier. 
SUMMARY 
A grid amplifier is a structure that amplifies a microwave beam and combines the output beams of 
many transistors, making it possible to greatly increase power. Because the power is combined in free 
space, grid ampliiers eliminate losses associated with waveguides and transmission-line networks. 
Fig. 1 shows a perspective view of a grid-amplifier measurement setup. The input beam is fed on the 
left-hand side with horizontal polarization. In the active grid, the input beam is received, amplified, 
and then reradiated, with vertical polarization, as the output beam to the right-hand side. By this 
quasi-optical technology, grid amplifiers demonstrated gains of 10 and 11 dB with HBT’s[1,2], and 
9 dB with MODFET’s[3] at X-band. These grids were fabricated by hybrid technology with chips 
mounted on a printed-circuit board. 
In this paper, we will report the models and measurements of the monolithic grid amplifier. Based 
on the models, a 36-element monolithic grid was fabricated on GaAs substrate. The grid amplifier, 
as shown in Fig. 2, is composed of 36 unit cells periodically distributed on the substrate. The period 
of the unit cell is 1.9 mm. The unit cell is shown in Fig. 3. In the unit cell, the input beam is 
received by the input leads. The input matching capacitor -compensates for the inductive reactance 
of the input lead. The stabilizing capacitor provides a phase lead to stabilize the grid[2]. The output 
leads radiate the amplified output beam. The active devices are heterojunction-bipolarr-transistor’s 
(HBT’s)[4] with a maximum oscillation frequency, fmaz, of 54 GHz and unity-current-gain frequency, 
f2, of 38 GHz. The maximum available gain at 40 GHz is 8.2 dB. 
The gain is measured in the far-fieldtl], and is shown in Fig. 4. The maximum measured gain is 
4 dB at 40 GHz and the 3-dB bandwidth is 800 MHz. The difference of biased and non-biased gains 
is 17 dB at 40 GHz. No oscillation was observed. Fig. 5 shows the gain versus the bias current at 
40 GHz. The peak gain occurs at a bias current of 16 mA per transistor. 
REFERENCE 
[l] M. Kim, E. Sovero, J .  Hacker, M. DeLisio, J.-C. Chiao, S. Li, D. Gagnon, J. Rosenberg, and 
D. Rutledge, “A 100-Element Grid Amplifier,” IEEE Trans. Microwave Theory Tech., vol. 41, 
pp. 1762-1771, October 1993. 
[2] C.-M. Liu, E. Sovero, M. DeLisio, A. Moussessian, J. bsenberg, and D. Rutledge, “Gain and 
Stability Models for HBT Grid Amplifiers,” submitted to 1995 IEEE AP-S Int. Symp., 1995. 
[3] M. DeLisio, C.-M. Liu, A. MouSSeSSian, J .  Rosenberg, and D. Rutledge, “A 100-Element MOD- 
FET Grid Amplifier,” submitted to 1995 IEEE AP-S h t .  Symp., 1995. 
[4] P. Asbeck, F. Chang, K.-C. Wang, G. Sullivan, D. Cheung, “GaAs-Based Heterojunction Bipolar 
Transistors for Very High Performance Electronic Circuits,” Proceedings of the IEEE, vol. 18, 
pp. 1709-1726, December 1993. 
92 
Input Active output 
Polarizer Grid Polarizer 
L 
E 
1 
output 
Signal 1 
Y lrly 
Figure 1. Perspective view of the grid-amplifier measurement setup. 
Figure 2. Photograph of the 36-element monolithic 
grid amplifier compared with a dime. 
0 
e 
d 5  'a 
Q 
E 5 -10 
E 
-1 5 
$I 
" " " " " " " " " '  
35 40 45 
Frequency, GHz 
Figure 4. Gain of the monolithic grid amplifier. The 
measured peak gain is 4 dB at 40 GHz. 
93 
- 1.9 mm _______( 
Figure 3. Unit cell sketch. 
-1 5 
-20 
0 5 10 15 20 
Bias Currcnt per Transistor, mA 
Figure 5. Gain versus bias current at 40 GHz. 


GaAs-Based Heterojunction Bipolar Transistors for Very High Performance Electronic Circuits,”

Gain and Stability Models for HBT Grid Amplifiers,” submitted to

https://authors.library.caltech.edu/29339/1/LIUdrc95.pdf

40 GHz Monolithic Grid Amplifier

Abstract

Similar works

Full text

Available Versions

Caltech Authors - Main

Caltech Authors - Main

Caltech Authors - Main