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TWOWAY RADAR EQUATION (BISTATIC)
The following table contains a summary of the equations developed in this section.
BISTATIC
RADAR
There are also true bistatic radars  radars where the transmitter and receiver are in different locations
as is depicted in Figure 1. The most commonly encountered bistatic radar application is the semiactive missile.
The transmitter is located on, or near, the launch platform (surface or airborne), and the receiver is in the
missile which is somewhere between the launch platform and the target.
The transmitting and receiving
antennas are not the same and are not in the same location. Because the targettoradar range is different from
the targettomissile range, the targettoradar and targettomissile space losses are different.
The peak power at the radar receiver input is :
[1]
* Keep λ or c, σ, and R in the same units.
On reducing the above equation to log form we have:
10log P_{r} =
10log P_{t} + 10log G_{t} + 10log G_{r} + 10log σ  20log f + 20log c  30log 4π
 20log R_{Tx}  20log R_{Rx} [2]
or in simplified terms:
10log P_{r}
= 10log P_{t }+ 10log G_{t} + 10log G_{r} + G_{σ} 
α_{Tx}  α_{Rx} (in dB) [3]
Where
"Tx corresponds to transmitter to target loss and "Rx corresponds to target to receiver loss, or:
α_{Tx} = 20log(f_{1}T_{Tx}) + K1 (in dB) and α_{Rx}
= 20log(f_{1}T_{Rx}) + K1 (in dB)
with K1 values provided on page 46.1 and with f_{1} being the MHz or GHz value of frequency.
Therefore, the difference between monostatic and bistatic calculations is that two α's
are calculated for two different ranges and different gains may be required for transmit and receive antennas.
To avoid having to include additional terms for these calculations, always combine any transmission line loss with
antenna gain.
As shown in Figure 2, it should also be noted that the bistatic RCS received by the missile
is not always the same as the monostatic RCS. In general, the target's RCS varies with angle. Therefore, the
bistatic RCS and monostatic RCS will be equal for receive and transmit antennas at the same angle to the target
(but only if all three are in a line, as RCS also varies with elevation angle).
Figure 2. Bistatic RCS Varies
Table of Contents
for Electronics Warfare and Radar Engineering Handbook
Introduction 
Abbreviations  Decibel  Duty
Cycle  Doppler Shift  Radar Horizon / Line
of Sight  Propagation Time / Resolution  Modulation
 Transforms / Wavelets  Antenna Introduction
/ Basics  Polarization  Radiation Patterns 
Frequency / Phase Effects of Antennas 
Antenna Near Field  Radiation Hazards 
Power Density  OneWay Radar Equation / RF Propagation
 TwoWay Radar Equation (Monostatic) 
Alternate TwoWay Radar Equation 
TwoWay Radar Equation (Bistatic) 
Jamming to Signal (J/S) Ratio  Constant Power [Saturated] Jamming
 Support Jamming  Radar Cross Section (RCS) 
Emission Control (EMCON)  RF Atmospheric
Absorption / Ducting  Receiver Sensitivity / Noise 
Receiver Types and Characteristics 
General Radar Display Types 
IFF  Identification  Friend or Foe  Receiver
Tests  Signal Sorting Methods and Direction Finding 
Voltage Standing Wave Ratio (VSWR) / Reflection Coefficient / Return
Loss / Mismatch Loss  Microwave Coaxial Connectors 
Power Dividers/Combiner and Directional Couplers 
Attenuators / Filters / DC Blocks 
Terminations / Dummy Loads  Circulators
and Diplexers  Mixers and Frequency Discriminators 
Detectors  Microwave Measurements 
Microwave Waveguides and Coaxial Cable 
ElectroOptics  Laser Safety 
Mach Number and Airspeed vs. Altitude Mach Number 
EMP/ Aircraft Dimensions  Data Busses  RS232 Interface
 RS422 Balanced Voltage Interface  RS485 Interface 
IEEE488 Interface Bus (HPIB/GPIB)  MILSTD1553 &
1773 Data Bus  This HTML version may be printed but not reproduced on websites.
