A multiple frequency RF modem includes a frequency synthesizer for providing local oscillator signals to double balanced mixer circuits in both the transmitter and receiver sections. To test the frequency synthesizer, the synthesizer is set to produce a local oscillator signal having a nominal frequency of 3 IF. The transmitter RF filter is tuned to suppress all harmonics and sidebands other than the 4 IF sideband. A ganged set of switches is employed to connect the transmitter output directly to the receiver input in the modem. Another switch in the set isolates the receiver mixer circuit from the frequency synthesizer during testing and connects it instead directly to the output of an IF oscillator in the transmitter section. Due to its non-linear operating characteristics, the receiver mixer circuit generates a strong third harmonic of its local oscillator input. During operation in the testing mode, this third harmonic has a frequency of 3 IF. The mixer circuit combines the 3 IF harmonic with the nominal 4 IF signal received through the wrap line. If the received signal has an actual frequency of 4 IF, a strong signal will appear at the output of the IF filter in the receiver. Since the wrapped signal has an actual frequency of 4 IF only if the frequency synthesizer output during testing is actually 3 IF, a strong output signal indicates that the frequency synthesizer is operating properly.
A novel circuit architecture is disclosed for achieving audio, tone, and digital data signal modulation in a full duplex radio transceiver. A single signal source is utilized to generate both transmitted carrier and receiver local oscillator injection signals. Yet the architecture is such that the transmitted data does not appear at the receiver's discriminator output--while a "side tone" of transmitted audio does so appear. The audio to be transmitted is used to frequency modulate a VCO and provide the receiver first mixer injection signal as well as a "carrier" input to a phase modulator. The data/tone signals are on the other hand, combined and integrated in a complex waveform and input to control the phase modulator. The resulting FM (data/tone and voice) output from the phase modulator is then input to a conventional duplexed r.f. transmitter.
A circuit for testing the function of mobile radio receiving installations is provided, wherein the circuit generates an HF-output signal that is used to test the system. A frequency mixer receives an oscillation signal (8) generated from within the superheterodyne receiver and an IF-carrier oscillation signal (32) generated from and oscillator (7) within the circuit. The frequency mixer generates an HF-output signal (12) that is dependent on the amplitude and frequency of the received oscillation signals. In alternative embodiments of the invention, the circuit of the invention is incorporated into the superheterodyne receiver, and the generated IF-carrier frequency 32 is eliminated and replaced with an IF-signal 22 produced by self-excitation of the superheterodyne receiver. With multi-antenna scanning diversity systems, additional switches and switching signals are included.
An antenna test system is used for testing wireless telecommunication systems. In an embodiment of the invention, the test system includes an antenna array comprising a plurality of individual antennas that are deployed in a pattern within a confined testing area such as in a building or laboratory. A plurality of base stations are selectively connected to the antennas via an antenna matrix. When the antenna matrix makes a connection between a base station and an antenna, a cell is activated accordingly. At least one mobile is positioned in fixed location and operates within range of an activated cell wherein various test procedures are run and monitored by a remote computer workstation. The invention is particularly suitable for testing problems associated with handoff procedures and interference by sequentially shifting activated cells relative to the stationary mobiles. The inventive technique provides consistent conditions necessary for repeat testing for use in system optimization.
An off-channel leakage power monitor implemented in a transceiver (100) dynamically measures adjacent and alternate channel leakage power produced by nonlinearities in a transmitter (110) power amplifier (116). A main local oscillator (124), offset voltage-controlled oscillator (122), and second local oscillator (170) are adjusted to obtain on-channel power, adjacent channel power, and alternate channel power measurements using a measurement calculator (185) implemented in a digital signal processor (180) or as a gate array in a receiver (140). Once the off-channel leakage power measurements have been obtained, any number of techniques can be used to extract increased efficiency from the power amplifier (116) while maintaining acceptable linearity under changing operating conditions.
