| 摘要 |
In order to test the performance (sensitivity) of a receiver, such as a WCDMA radio telephone, (9, Fig.1), a test signal is generated (2) and applied to the receiver via a channel model 3 which simulates the communication channel between a transmitter and the receiver. The model 3 has a fading model 7 which produces a modified test signal 23 by imparting to the test signal the effects of fading in the communication channel. A comparator 9 compares a characteristic of the modified signal 23 with a characteristic of a reference signal 25, and the output of the comparator 9 is used to control the test signal power by means of a variable gain amplifier 6 or by controlling the test signal generator (2). This has the advantage of allowing the performance of an RF receiver having a power control RF link to be modelled by incorporating a model of the power control loop within the channel model 3. Means 8 may be provided for estimating the power of the modified signal 23. The compared signal characteristic may be the signal power, or the signal to interference ratio (SIR), or the signal to noise ratio (SNR). The simulated RF path characteristics may be varied dynamically. The fading model 7 can be selected to model single path fading or multipath fading using a Rayleigh or Ricean probability density function (Figs.3a,3b). The power estimator 8 may introduce a time lag to represent time delays in an actual communication system. Modelled channel noise, generated by an Additive White Gausian Noise (AWGN) probability density function 12, is summed 21 with the modified test signal 23 to form the test signal 18 which is applied to the receiver. The AWGN function 12 can be incorporated within the power control loop 6, 8, 9, 10, 11. |
