a rather large value for J Nds, but taking into account for the possible worst condition. With A/ = 50 MHz, A</> is estimated to be about 4°, which is not too small. When we took the average of phases </>, and <i2 in Eq. (4), there could introduce an ambiguity known as the rr-ambiguity. Let In performing the phase average, the Ktt term could get lost. For K even, no damage is done. For K odd, a n error is introduced and one would conjugate the wrong phase. In order to remove these two difficulties, especially the rr-ambiguity, Raytheon (5), Boeing (6), and Rockwell (7) have all made suggestions. Their solutions are very complicated and usually require a lot of hardware in the receiving and phase conjugation circuitries with much added cost. We shall show in our next section several simple solutions which circumvent the abovementioned difficulties and do not add extra costs. III. NEW DESIGNS OF PILOT BEAM SYSTEM In this section, several uplink designs are proposed. The first simple design avoids the ^-ambiguity and the rest are improved versions of the first one. They are all free from the ir-ambiguity, but reduce the phase difference A</> to various orders. (i) This is also a two-tone uplink, but the two frequencies are both on one side of the downlink frequency with where again e = kf/fD is a small number. In this simple design the 7r-ambiguity is removed since no division of the phase is used anywhere. The combined phase is
RkJQdWJsaXNoZXIy MTU5NjU0Mg==