CV110-2A
Cellular-band High Linearity Downconverter
Device Architecture / Application Circuit Information
RF IN
GND
GND
IF THRU
GND
28
RF OUT 1
GND 2
N/C 3
GND 4
IF THRU 5
GND 6
RF/IF 7
27
26
25
24
IF IN
23
22
21 IF OUT
GND
Typical Downconverter Performance Chain Analysis
Stage
RF Amplifier
RF Filter
MMIC Mixer
IF Amplifier
CV110-2A
Gain
(dB)
Output
P1dB
(dBm)
Output
IP3
(dBm)
NF
(dB)
Current
(mA)
150
---
60
150
360
Cumulative Performance
Output Output
Gain
NF
P1dB
IP3
(dB)
(dB)
(dBm)
(dBm)
13.5
21.0
40.0
3.5
12.0
19.5
38.5
3.5
3.0
6.1
22.1
4.5
22.0
20.3
37.0
5.0
22.0
20.3
37.0
5.0
RF Amp
IF Amp
20 GND
19 N/C
IF Feedthru
Path
18 GND
LO Driver Amp
17 BIAS
16 GND
RF/IF
LO
8
GND
9
N/C
10
GND
11
MIXLO
12
GND
13
LO OUT
14
GND
15 LO IN
13.5
21
40.0
3.5
-1.5
---
---
1.5
-9.0
8
23.0
9.8
19.0
22
39.1
2.5
Cumulative Performance
RF Amp Matching
RF Amp Bias
IF Amp Matching
IF Amp Bias
RF Bandpass Filter /
Attenuator Pad
Printed Circuit Board Material:
.014” FR-4, 4 layers, .062” total thickness
LO Amp Bias
LO Amp Bias
RF / IF Diplexer
(used for cellular versions only)
CV110-2A:
The application circuit can be broken up into four main
functions as denoted in the colored dotted areas above: RF/IF
diplexing (purple), amplifier matching (green), filtering (red), and dc
biasing (blue). There are various placeholders for chip components in
the circuit schematic so that a common PCB can be used for all WJ
single-branch converters. Additional placeholders for other optional
functions such as filtering are also included.
RF / IF Amplifier Matching:
The RF amplifier requires a shunt
matching element for optimal gain and input return loss performance.
The IF amplifier requires matching elements to optimize the
performance of the amplifier to the desired IF center frequency.
Since IF bandwidths are typically on the order of 5 to 10%, a simple
two element matching network, in the form of either a high-pass or
low-pass filter structure, is sufficient to match the MMIC IF
amplifier over these narrow bandwidths. Proper component values
for other IF center frequencies can be provided by emailing to
applications.engineering@wj.com.
RF Bandpass Filtering:
Bandpass filtering is recommended to
reject the image frequencies and achieve the best noise figure
performance with the downconverter.
The bandpass filter,
implemented with a SAW filter on the application circuit, allows for
the suppression of noise from the image frequency. It is permissible
to not use a filter and use a 2 dB pad with R6, R7, and R16 instead
with slightly degraded noise figure performance. Standard WJ
evaluation boards will have the 2 dB pad in place.
External Diplexer:
In a downconversion application, the incoming
RF signal impinges on the switching elements of the mixer; the
interaction with these switches produces a signal at the IF frequency.
The two signals (RF and IF) are directed to the appropriate ports by
the external diplexer. Pin 5 contains the IF signal and allows the
signal to be transferred to pin 25 for the convenience of PCB layouts.
DC biasing:
DC bias must be provided for the RF, LO and IF
amplifiers in the converter. R1 sets the operating current for the last
stage of the LO amplifier and is chosen to optimize the mixer LO
drive level. Proper RF chokes and bypass capacitors are chosen for
proper amplifier biasing at the intended frequency of operation. The
“+5 V” dc bias should be supplied directly from a voltage regulator.
IF Amplifier Matching
Frequency (MHz)
L7 (nH)
C17 (pF)
R8 (ohms)
L4 (nH)
180
82
4.7
2.2
330
210
82
3.3
2.2
220
240
56
3.9
2.2
220
Specifications and information are subject to change without notice
WJ Communications, Inc
•
Phone 1-800-WJ1-4401
•
FAX: 408-577-6621
•
e-mail: sales@wj.com
•
Web site: www.wj.com
Page 2 of 4 April 2007
WJCI [ WJ COMMUNICATION. INC. ]
