Passive Coherent Location PCL

In PCL systems care must be taken to ensure that the signal received directly from the transmitter does not compete with and swamp that from the target. Typically this will be the case unless measures are taken to suppress the direct signal occurring in the indirect channel. We can formulate a simple expression for the amount of direct signal suppression required by calculating the ratio of the indirect received sig- 

Range resolution is the ability of a radar system to distinguish two closely spaced targets at differing ranges. In monostatic radar this is primarily a function of pulse length or modulation bandwidth. Azimuth 

The ambiguity function represents the output of a matched filter and may be written as 

Computation of this function results in a three-dimensional plot for which one axis is time delay (or range), the second is Doppler frequency or radial velocity and the third is the output power of the matched filter (usually normalised to unity). The extent of the ambiguity function peak in the Tr and the fd dimensions determines the range and Doppler resolutions respectively. As we are using the directly received signal only we term this self-ambiguity as there is no inclusion of any system geometry dependence on the transmitter and receiver locations. 

If a number of speech collections are analysed then we see that performance is not consistent. This is illustrated in Table 1 which shows the bandwidth in kHz for ten waveform samples. 

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A particular variant on the bistatic and multistatic themes is Passive Coherent Location (PCL). This is normally taken to mean a system where transmissions are provided by a third party and only the receiver is formerly part of the design. This is sometimes also referred to as a hitch hiking mode of operation. It is also usually referred to as an example of bistatic radar although, as we shall see later, many transmissions can be used from a variety of transmitter sites thus making an example of multistatic radar. 

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